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Fractures in Dogs and Cats (and Rehabilitation Techniques) Brian S. Beale, DVM, Diplomate ACVS Gulf Coast Veterinary Surgery Houston, Texas Comminuted fractures can be especially challenging due to the complexity of the fracture fragments and concomitant soft tissue injury. Careful consideration should be given to decision-making prior to onset of fracture repair. Factors that should be considered include mechanical, biological and postoperative compliance. Complex fractures that are treated with a mechanically sound repair often leave the surgeon pondering what could have possibly gone wrong when a "perfect" repair fails. Often times, the answer lies in the neglect of the biological or postoperative compliance factors. Neurologic function should always be assessed because complex fractures are often associated with high-energy trauma that also can injure the brachial plexus or peripheral nerves of the forelimb. This lecture will focus on presentation of clinical cases involving complex fractures of the forelimb and hindlimb, with an emphasis on the decision-making process. A variety of fracture repair techniques will be discussed including interlocking nails, plate-rod construct and linear external fixators. FRACTURE MANAGEMENT Comminuted fractures of the extremities can be challenging. It is always a race between a fracture healing and an implant failing. Steps can be taken to tip the scale in the direction of early fracture healing. These steps include:
Surgical Approach Closed reduction and stabilization is the optimal method of treatment when possible. Unfortunately, this method is rarely possible in the senior patient due to the severity of fractures seen, long time until bony union, and the tendency for patients to develop bandage sores. Open surgical approaches can be either traditional or minimally invasive. The minimally invasive approach has been described as an "open but don't touch" approach. The acronym, OBDT, is used to describe this technique. The advantages to using an OBDT technique is preservation of vascular supply to the fracture site and thus quicker healing, shorter intraoperative time, less postoperative pain and early return to function. Methods of stabilization that work well with an OBDT approach include the interlocking nail, plate-rod hybrid and external fixation. Traditional surgical appoaches and methods of fracture stabilization can also be used effectively in senior patients, but anatomic reconstruction of the fracture and placement of cancellous bone grafts are recommended. 
Bone Grafts Numerous sites for harvest of cancellous bone graft have been described in the dog, but the most practical are the greater tubercle of the humerus, wing of the ilium and the medial, proximal tibia. The humerus provides the greatest amount of cancellous bone, but the ilium and tibia provide sufficient amounts for most applications. All of these sites are readily accessible, have easily recognizable landmarks, have little soft tissue covering, and provide relatively large amounts of cancellous bone. The greater trochanter can also be used if other sites are not available; however, the yield of cancellous bone is markedly less. Occasionally multiple sites are required to harvest sufficient quantities of bone to fill large bone defects or during arthrodesis. Minimal instrumentation is required for harvest of cancellous bone graft. Basic surgical instruments are used to approach the site selected for harvest. A hole is drilled through the near cortex using either a drill bit, trephine or trocar-pointed pin. A curette is used to scoop the graft out of the metaphyseal cancellous bone. The cancellous bone should be scooped out in large clumps if possible. Use a curette that can be comfortably manipulated in the medullary cavity; I prefer to use a relatively large curette as this speeds harvest and reduces trauma to the graft. Closure is performed routinely in 2-3 layers. Recently, a technique was described using an acetabular reamer to harvest large amounts of corticocancellous bone graft from the lateral surface of the wing of the ilium. The graft collected should be handled gently. It is desirable to collect the graft immediately prior to usage. This increases the osteogenic properties of the graft. As graft is harvested, it should be placed on a blood-soaked gauze until transfer to the recipient site. Extreme care should be taken to store the graft properly; do not accidentally discard the graft due to misidentification of the gauze as being used. The graft should be atraumatically packed into the recipient site. Lavage of the site should be avoided after the graft is placed. FRACTURE STABILIZATION Articular Fractures Most fractures involving the articular surfaces should be considered complex. The complexity of these fractures arises because of the need for perfect anatomic reduction and rigid stability to avoid debilitating osteoarthritis. In addition, visualization of the joint surfaces is often difficult due to inadequate exposure due to constraints of supportive soft tissues crossing the joints. Violation of these tissues by either transection or osteotomy can improve exposure, but may lead to complications such as joint instability, osteoarthritis or non-union. Comminuted articular fractures are best managed using an open approach, but simple fractures can be treated arthroscopically in some cases. Fixation methods include lag screws, divergent pins, plate-rod, external fixators and bone plates. Joint stability should also be assessed after repair because ligamentous or joint capsular injury may occur simultaneously, predisposing the patient to chronic pain and osteoarthritis if left untreated. Long Bone Fractures Interlocking Nails Interlocking nails are particularly useful for stabilization of fractures in the senior dog and cat. An interlocking nail system (Innovative Animal Products, Inc., Rochester, MN 55901) is available for repair of fractures involving the femur, humerus, and tibia of small animals. Interlocking nails are very useful in simple diaphyseal fractures, comminuted fractures, or fractures of the metaphyseal region which are often difficult to plate. They have also been used successfully in infected fractures, correctional osteotomies and nonunions. Interlocking nails give a second alternative for many fracture types previously repairable with bone plates only. They also can be used for many applications where an intramedullary pin and adjunctive external fixator would be used; an example of this is a simple, transverse femur fracture. The nail is actually a modified Steinmann pin- modified by drilling one or two holes proximally and distally in the pin, which allows the placement of screws through the holes. The nail and screws can be applied in closed or open fashion due to the incorporation of a specific guide system that attaches to the nail. The specific equipment needed to place the nail includes a handchuck, extension device, aiming device, drill sleeve, drill guide, tap guide, drill bit, tap, depth gauge, and screwdriver. Cost of the system is very reasonable and each nail is approximately half the cost of a comparative bone plate. The nails are available in diameters of 4.7, 6 and 8 mm and varying lengths. The 4.7 mm nail uses 2.0 mm screws. The 6 mm nail comes in forms that will accommodate either a 2.7 or 3.5 mm screw. The 8 mm nail comes in forms that accommodate either a 3.5 or 4.5 mm screws. The interlocking nail neutralizes bending, rotational and axial compressive forces due to incorporation of transfixation screws which pass through the pin and lock into the bone. This is in contrast to a single intramedullary Steinmann pin which only neutralizes bending forces. The interlocking nail has a similar bending strength compared to bone plates, but is slightly weaker in neutralization of torsional forces. The screws also prevent pin migration, a common complication seen with Steinmann pins. 
When using an interlocking nail, the largest diameter nail should be selected that can be accommodated by the medullary cavity at the fracture site. In most large dogs, an 8 mm nail and either 3.5 or 4.5mm screws can be used in the femur and humerus. In medium-sized dogs, the 6 mm nail and either 2.7 or 3.5 mm screws are typically used. In small dogs and cats, the 4 mm nail and 2.0 mm screws are typically used. The tibia of medium and large - sized dogs will usually accomodate a 6 mm nail, but some large dogs will accept a 8 mm nail. Small dogs and some cats will accept a 4.0 mm nail for repair of tibial fractures. Plate-Rod Construct Fixation of comminuted fractures with an intramedullary pin and a bone plate combination (plate/rod hybrid) does not require reconstruction of the comminuted fragments. Rather, the area of comminution is bridged or buttressed with a plate/rod combination without manipulation or reduction of the fracture fragments. This type of repair can be used to stabilize comminuted fractures of the humerus, femur and tibia of dogs and cats. The intramedullary pin (rod) neutralizes bending forces and the plate protects against rotational and axial compressive forces. Traditional bone plates are used in most dogs. Veterinary cuttable plates (VCP) provide adequate strength and stiffness in cats and small dogs when used in combination with an intramedullary pin, as well as providing additional holes for screw placement. The addition of the intramedullary pin protects the plate from cyclic bending forces, which can lead to early plate fatigue and screw loosening. This is particularly important in the area of comminution where plate holes must often be left open. 
When using a plate/rod combination, the diameter of the pin selected should accommodate approximately 30-40% of the medullary cavity at the diaphyseal isthmus. The length of pin should be sufficient to permit seating in the proximal and distal metaphyseal bone if possible. The size of plate selected is often dictated by the size of screw that can be placed in the bone. Ideally, at least 2 bicortical screws should be placed proximally and distally although this is not always possible. Adequate room must be present to allow screw purchase past the intramedullary pin. The screws must be angled away from the intramedullary pin or the plate must be offset slightly to accomplish screw placement. Monocortical screws are used if bicotical screws can not be placed. Application of a plate/rod hybrid is similar for most comminuted fractures of the humerus, femur and tibia. A lateral approach is generally made to the humerus and femur; a medial approach is usually made to the tibia. An attempt should be made to minimize dissection of soft tissues, thus encouraging more rapid healing. Due to the strength and rigidity of plate/rod repair and the goal to preserve blood supply to bone fragments, complete rebuilding of the bony cylinder with cerclage wires is undesirable. The goal of the dissection is to gain just enough visualization to ensure proper placement of the intramedullary pin and plate. The appropriate pin is selected and placed in routine fashion. Pins may be placed retrograde or normograde, depending on the bone involved and fracture location. The pin is driven just past the end of the fragment. The fracture is reduced and the pin is driven into the medullary cavity of the opposing main fragment. Spatial realignment (rotation and length) of the limb is established as the pin is seated into the fragment. A bone plate is contoured and applied to the tension surface of the bone, bridging the area of comminution. Consideration should be given when positioning the plate to allow screw placement with minimal interference with the intramedullary pin. Bicortical screws are placed where possible. Ideally, a minimum of 2 bicortical screws is placed in the proximal and distal fragments. Additional bicortical or monocortical screws are placed as permitted by the location of fracture fragments and location of the underlying intramedullary pin. Occasionally, markedly displaced fragments do not become incorporated into the healing callus. These fragments can be partially reduced with "lasso" sutures using 2-0 or 3-0 absorbable suture. Sutures are passed around the fragment, as well as the bone and plate, without compromising blood supply. The suture is gently tightened and secured when the fragment is drawn closer to the other fragments. This technique brings isolated fragments into the vicinity of the main fragments and may increase the likelihood of their participation in the healing process. Following placement of the plate/rod, fracture stability is checked and a cancellous bone graft is placed if desired. POSTOPERATIVE MANAGEMENT The postoperative period is often not given the level of attention that is deserved to optimize recovery from repair of orthopedic problems in senior dogs and cats. Perioperative analgesia is important for early return to function, to enhance healing and reduce the length of hospital stay. The use of NSAIDs and narcotics help to achieve this goal. Bandaging and restricted activity may be necessary postoperatively and pet owners need to educated on the importance and expectations of their use. Physical therapy exercises may be needed to prevent fracture disease, encourage early return to function, and obtain maximum return to function. Postoperative physical therapy and exercises to rehabilitate the patient undergoing orthopedic surgery is an important factor towards a successful outcome. Lameness in the growing dog -
Distinguishing growing pains from surgical disease. Lameness in the growing dog less than a year of age is common, particularly in sporting and large breeds of dogs. Common causes for lameness in these immature dogs include Osteochondritis dissecans, elbow dysplasia, hip dysplasia, trauma and panosteitis. Other less common causes include septic arthritis, hypertrophic osteodystrophy and ligamentous instability. Many of these conditions can be treated with great success. In general, an early diagnosis should be made to increase the odds of having a good long term outcome. Osteochondritis Dissecans of the Shoulder Lesions associated with osteochondritis dissecans (OCD) of the shoulder occur on the caudal aspect of the articular surface of the humeral head. The condition can be bilateral and is most common in rapidly growing large breed dogs. The severity of the lesion may range from a small cartilage flap to a large osteochondral fragment having a deep subchondral defect. Although some dogs will perform adequately following conservative management, early surgical intervention is considered to be the best recommendation. Early diagnosis and prompt surgical removal of these fragments are recommended to reduce the chance of developing degenerative joint disease (DJD) and to avoid future displacement of the flap down the biceps tendon sheath. Diagnosis is made by characteristic historical, physical exam and radiographic findings. Pain is usually present when the shoulder is fully flexed. Radiographic evidence of a subchondral defect is seen on the caudal aspect of the humeral head. Typical subchondral defect associated with OCD of the humeral head
 
Surgical removal is best performed arthroscopically. Arthroscopic treatment allows quick removal of OCD flaps using a minimally-invasive technique, as well as permitting a more thorough evaluation of the joint structures as compared to a traditional arthrotomy. Postoperative pain is minimal and return to function is rapid following arthroscopic treatment. If shoulder OCD is to be treated with an open arthrotomy, a muscle-separation technique is recommended to reduce patient morbidity and speed recovery. The shoulder can be surgical accessed between the acromial and spinous heads of the deltoideus muscle or caudal to the spinous head of the deltoideus muscle. Following removal of the osteochondral flap, the subchondral defect should be treated with light curettage or micro-picking to encourage development of a new blood supply and fibrocartilagious repair. Osteochondritis Dissecans of the Elbow Lesions associated with OCD of the elbow occur on the distal aspect of the medial humeral condyle. The lesions may be characterized as a small cartilage flaps or large osteochondral fragments. The condition can be bilateral and is most common in rapidly growing large breed dogs. Early diagnosis and prompt surgical removal of these fragments are recommended, prior to the onset of significant DJD. Diagnosis is made by characteristic historical, physical exam and radiographic findings. Pain is usually present when the elbow is fully flexed and extended. Radiographic evidence of a subchondral defect is seen on the distal aspect of the medial humeral condyle. Surgical removal is best performed arthroscopically. Arthroscopic treatment allows quick removal of OCD flaps using a minimally-invasive technique, as well as permitting a more thorough evaluation of the joint structures as compared to a traditional arthrotomy. Postoperative pain is minimal and return to function is rapid following arthroscopic treatment. If elbow OCD is to be treated with an open arthrotomy, a muscle-separation technique is recommended to reduce patient morbidity and speed recovery. The elbow can be surgical accessed between the pronator teres and flexor carpi radialis muscles. The medial collateral ligament should not be transected. Following removal of the osteochondral flap, the subchondral defect should be treated with light curettage or micro-picking to encourage development of a new blood supply and fibrocartilaginous repair. OCD of the medial humeral condyle
Osteochondritis Dissecans of the Stifle Lesions associated with osteochondritis dissecans (OCD) of the stifle occur on the medial or more commonly the lateral condyle of the distal femur. The lesions may be characterized as small, cartilage flaps or large, osteochondral fragments. Early diagnosis and prompt surgical removal of these fragments are recommended, prior to the onset of significant degenerative joint disease (DJD). The most common approach is a lateral or medial parapatellar approach to the stifle. After performing an arthrotomy, the stifle is flexed to allow access to the caudal aspect of the articular surface of the condyles. Separation of the joint surfaces with a Hohmann retractor is often helpful to improve visualization. The cartilage or osteochondral fragment is elevated and removed using a Freer or periosteal elevator. Gentle curettage of the subchondral lesion can be performed to remove loose debris and undermined edges at the periphery of the lesion. Fibrocartilaginous repair tissue within the defect should be left undisturbed. Forage (drilling of several small holes into the subchondral bone)of the defect to encourage vascular ingrowth has been proposed, but its efficacy is unknown. The prognosis is fair to good after early treatment. Recently, arthroscopic removal of the fragments has been successfully performed in dogs. This technique is an effective method of removing fragments and treating the subchondral bed, while decreasing postoperative patient morbidity. Arthroscopic visualization of the lesion is superior to that achieved by arthrotomy. Osteochondritis Dissecans of the Hock Lesions associated with osteochondritis dissecans (OCD) of the hock occur on the medial or lateral trochlear ridge of the talus. The lesions may be characterized as small, cartilage flaps or large, osteochondral fragments. Early diagnosis and prompt surgical removal of these fragments are recommended, prior to the onset of significant degenerative joint disease (DJD). Arthroscopic removal of OCD fragments can be performed with great success, but is technically demanding. Several surgical approaches have been described to gain access to the flaps. Severance of either collateral ligament allows subluxation of the joint and excellent visualization of the trochlear ridges; however, this approach should be avoided due to the probability of causing iatrogenic joint instability, predisposing the dog to greater DJD. Osteotomy of the medial or lateral malleolus also gives excellent surgical exposure; however, this approach can also be associated with increased morbidity. Medial malleolar osteotomy is technically demanding and requires iatrogenic formation of an articular fracture of the distal tibia. Precise reduction and rigid stabilization is necessary to prevent DJD. Lateral malleolar osteotomy is preferred, but precise reduction and rigid stabilization is necessary to prevent joint instabilty or nonunion of the osteotomy site. The preferred approaches are the dorsolateral and plantarolateral approaches to the lateral trochlear ridge, and the dorsomedial and plantaromedial approaches to the medial trochlear ridge. Accurate radiographic assessment of the location of the OCD lesion is necessary to select the appropriate surgical approach. Most OCD lesions can be accessed through a single approach; however, a combination of the dorsal and plantar approaches is necessary to gain access to some large lesions or lesions located on the midportion of the trochlear ridges. A combined approach to the medial trochlear ridge allows access to all but approximately 5% of the ridge (the midportion). A combined approach to the lateral trochlear ridge allows access to the entire ridge. The advantage to using the combined approaches is the preservation of the collateral ligaments without the need for a technically demanding, time consuming osteotomy. If these approaches fail to provide sufficient surgical exposure, a malleolar osteotomy can then be performed. Due to the low morbidity associated with these procedures, bilateral lesions can be operated at the same time. All four approaches are performed by making a curvilinear skin incision centered over the appropriate region of the trochlear ridge. Subcutaneous tissues are incised and retracted. Certain anatomical structures should be avoided during each approach. The dorsolateral approach requires lateral retraction of the tendons of the extensor digitorum longus, tibialis cranialis and extensor hallucis longus muscles, dorsal branch of the lateral saphenous vein, and superficial peroneal nerve (Fig 5.1). This approach also requires planter retraction of the tendons of the peroneus longus, extensor digitorum lateralis and peroneus brevis muscles. In the plantarolateral approach, the tendons of the peroneus brevis, extensor digitorum lateralis, and peroneus longus muscles must be avoided dorsally (Fig. 5.2). The plantar branch of the lateral saphenous vein and branch of the caudal cutaneous sural nerve are retracted in a plantar direction, and the flexor hallucis longus tendon is retracted medially. The dorsomedial approach requires lateral retraction of the tibialis cranialis tendon, saphenous nerve, cranial tibial artery and vein, and dorsal branches of the saphenous artery and vein (Fig. 5.3). In the plantaromedial approach, the tendon of the flexor digitorum longus muscle and distal attachment of the tibialis caudalis tendon are retracted dorsally and the flexor hallucis longus tendon, tibial nerve, medial saphenous vein and artery are retracted laterally (Fig. 5.4). The collateral ligament complex is preserved in all four approaches. The joint capsule is incised longitudinally, directly over the palpable trochlear ridge and retracted. Extension and flexion of the joint allow access to the trochlear ridge for removal of the OCD fragment. Removal is usually easily done using a Freer elevator or similar instrument. If present, synovial attachments to the fragment are sharply incised. Reattachment of the fragment with k-wires or lag screws is not recommended due to typical remodeling of the fragment present at the time of surgery, technical difficulty of the procedure, and possibility of implant failure. Gentle curettage of the subchondral lesion can be performed to remove loose debris and undermined edges at the periphery of the lesion. Fibrocartilaginous repair tissue within the defect should be left undisturbed. Forage (drilling of several small holes into the subchondral bone)of the defect to encourage vascular ingrowth has been proposed, but its efficacy is unknown. The joint capsule and subcutaneous tissues are closed in two layers using synthetic absorbable suture. The skin is closed using synthetic nonabsorbable suture. A soft padded bandage is recommended for 7-10 days. Exercise should be restricted to leashwalk only for 6 weeks. Elbow Dysplasia Elbow dysplasia refers to a collection of developmental diseases of the elbow affecting growing dogs which lead to osteoarthrosis. Manifestations of elbow dysplasia seen in dogs include fragmented medial coronoid process (FCP) of the ulna, ununited anconeal process (UAP) of the ulna, and osteochondritis dissecans (OCD) of the medial humeral condyle. These conditions are most commonly seen in medium and large breeds including the rottweiler, Labrador retriever, German shepherd, golden retriever and Bernese mountain dog, however, smaller breeds such as the Australian shepherd, Shetland sheepdog and chow chow can also be affected commonly. A genetic predisposition is suspected. Proposed etiologies of all these conditions include a manifestation of osteochondrosis or joint incongruity associated with underdevelopment of the ulnar trochlear notch. Early diagnosis of elbow dysplasia is important to optimize surgical treatment and prognosis. History Owners of dogs afflicted with elbow dysplasia usually report an onset of forelimb lameness during the rapid growth phase between 4 and 8 months of age. The lameness may be intermittant, persistent or shifting from one leg to the other. The severity of lameness may initially improve, but progressive lameness usually ensues due to progressive osteoarthritis. Clinical Signs Most dogs display an intermittant or persistent weightbearing lameness of one or both forelimbs. Palpation of the elbow may reveal joint capsular distention and pain, especially on full extension of the elbow. As the condition becomes more chronic, limited range of motion and palpable crepitus may occur. Eventually, many animals refuse to rise due to the pain associated with advancing arthritis. Diagnosis Early diagnosis is essential in order to reduce the chance of developing severe osteoarthritis and poor limb function. A diagnosis can usually be made radiographically. Radiographic views that are essential include the flexed lateral and anterior-posterior. Other views which can be beneficial include the extended lateral and oblique views. Recently, the craniocaudal-caudomedial oblique view was reported to have the highest sensitivity for diagnosing FCP.1 Tomograms and computerized tomograghy are also useful for evaluating the medial coronoid process. A presumptive diagnosis of FCP is generally made by identification of typical periarticular osteophytes seen with the disease, rather than actual identification of a free osteochondral fragment. Osteophytes are usually first seen on the proximal surface of the tip of the anconeal process. Visualization of these osteophytes requires full flexion of the elbow when the lateral radiographic view is made. Osteophytes are also seen around the ulnar trochlear notch and medial and cranial aspects of the proximal radius. Bone scans are also helpful in the early diagnosis of FCP, especially when radiographic changes may be equivocal. The diagnosis of UAP is usually simple. A large osteochondral fragment is generally seen on a flexed lateral radiographic view in the region of the anconeal process. Anterior-posterior radiographic views are usually diagnosic for the subchondral defect typically seen in cases of OCD of the medial humeral condyle. Dog with osteoarthritic changes consistent with fragmented medial coronoid process Surgery The long term prognosis following surgery can be affected by many factors including the severity of the disease (ie. size of fragment, size of subchondral defect, congruency of the joint, presence of preexisting osteoarthritis), type of surgical approach, type of surgical procedure and skill and experience of the surgeon. Clinical function is improved in most dogs if surgical treatment is performed early in the course of disease. The surgical approach chosen should be as noninvasive as possible. Osteotomy of the medial epicondyle, tenotomy or desmotomy are no longer necessary to gain access to the elbow joint. These techniques have a greater chance of leading to iatrogenic instability to the elbow due to damage to supporting structures of the joint. Arthroscopic removal of osteochondral fragments associated with FCP and OCD is the preferred method of treatment due to its lower postoperative morbidity, decreased invasiveness, improved visability, and improved postoperative performance. Hip Dysplasia in the Immature Dog Triple pelvic osteotomy (TPO) is frequently used in immature dogs for treatment of hip dysplasia. The acetabular segment is rotated an appropriate amount after osteotomy of the pubis, ischium and ilium. The acetabulum is stabilized with a contoured plate and screws placed over the ilial osteotomy site. An ischial wire is often used to give additional stability. The positional change of the acetabulum increases the stability and decreases the chance of subluxation in dogs that meet the criteria for the procedure. The end effect is a decrease of progressive osteoarthritis. Surgical Technique A standard approach to the pubis, ischium and ilium is made as described by Slocum. A pubic osteotomy is performed adjacent to the iliopectineal eminence and a small portion of pubis is removed. The ischial osteotomy is made at the lateral extent of the obturator foramen and is stabilized with a 1.0 or 1.25 mm orthopedic wire at the surgeon's discretion. The ilial osteotomy is made just caudal to the caudal extent of the sacrum. Care to avoid the sciatic nerve is taken. The acetabular segment is rotated laterally to the proper position and stabilized with a bone plate and screws of the surgeon's choice.  
Long Term Follow-Up TPO patients have been evaluated subjectively by the owner and veterinarian, radiographically and objectively using a force platform. All forms of evaluation are useful in determining the success of this technique. Complications do occur with the procedure, but fortunately are usually minor and resolve with time or treatment. Owner Evaluation Owners typically were pleased with the results of TPO surgery at long term follow-up of 218 dogs. In a study at our clinic, pet owners were interviewed for follow-up information at the time of reexamination or by phone consultation. Pet owners reported a good to excellent result in 92% of cases; 89% said they would do the procedure again. The most frequent reported complaint was stiffness after exercise. Only one dog was reported as having another surgical procedure on a hip having a TPO; the second procedure was a femoral head ostectomy (FHO). The vast majority of dogs functioned as expected by the owner. Veterinarian Evaluation The gait of dogs undergoing TPO tended to different than that of a dog with normal hips. Obvious lameness was not usually present. The gait was usually associated with a shortened hindlimb stride and bunny-hopping was often seen. Full extension of the hips was usually resisted by the dogs, and some appeared mildly to moderately painful. The Ortolani sign was consistently eliminated. The predominant long term problem was mild osteoarthritis, but this tended to be subclinical or only intermittantly a problem. Hind limb muscle atrophy was evident in some dogs. The dogs performing best had an acetabular rotation of 20-30 degrees. Radiographic Evaluation The majority of dogs had radiographic progression of osteoarthritis at follow-up. The degree of osteoarthritis tended to be very mild to mild. An occasional dog will have moderate or severe osteoarthritis. Many of the ischial wires had either broken or torn through the ischial bone. Nine dogs had loosening of the caudal screws of the plate and had obvious displacement of the plate away from the bone of the caudal fragment. Fortunately, the rotation of the acetabulum appeared to be unaffected in all but one dog. Force Platform Evaluation Force platform evaluation appears to support the use of TPO surgery for treatment of hip dysplasia. Complications The most common long term complicaton was osteoarthritis. This tended to be very mild or mild in most dogs, requiring no or occasional NSAID therapy. Seromas or incisional dehiscences occasionally were seen, predominately at the ischial incision site; all were treated conservatively and resolved. Only one of 218 dogs received an FHO following TPO due to progressive arthritis. No dogs received a total hip replacement. The failure of ischial wires did not appear to result in any long term complications. Only one dog that had plate loosening required reoperation. This patient underwent staged TPO procedures 2 weeks apart. Both plates pulled away from the caudal bone segment resulting in excessive pain and acetabular instability. The patient responded adequately to revision surgery. Temporary sciatic neuropraxia was seen in one dog; this resolved completely in 4 months. Discussion The use of TPO to treat suitable candidates appears to be warranted. The use of an ischial wire does not appear to be necessary. No differences in complications or recovery were seen with or without a wire. In addition, many of the wires failed either by breaking or tearing trought the soft ischial bone. Dogs requiring greater than 30 degrees of acetabular rotation may not be good candidates for the procedure. A rotation of 20-30 degrees appears acceptable. Radiographic progression of osteoarthritis tends to occur, but usually is mild and often asymptomatic. Complications with this technique tend to be infrequent and of minimal clinical significance. WHAT'S NEW IN ANTERIOR CRUCIATE LIGAMENT REPAIR?
I generally recommend surgical repair of all dogs having a cruciate-deficient stifle, unless predisposing medical conditions contradict anesthesia or surgery. Surgical repair of the cranial cruciate-deficient stifle may take many forms. The vast number of surgical procedures developed to return stability to the unstable stifle suggests that no technique is ideal. The technique selected is often based on the age and weight of the patient, duration of injury and surgeon's preference. Factors to consider when deciding on a type of repair include signalment, intended use of the pet, duration of injury, type of injury (partial or complete tear), amount of instability, concomitant meniscal injury, patient morbidity and postoperative management. At the present time there is no surgical technique for management of the cruciate-deficient stifle that has been shown to be unequivocally superior. Signalment My personal preference is to repair small dogs (< 45 lbs) with an extracapsular prosthetic ligament technique (EPLT) and larger dogs (>45 lbs) with a tibial plateau leveling osteotomy (TPLO). Larger dogs can also be treated successfully by traditional intracapsular or extracapsular techniques and these techniques are still used when the tibial plateau angle is modest (12-20 degrees) or when financial concerns are present. Anticipated Use of Pet Pets expected to have low levels of activity may be treated differently from those expected to reach maximal athletic performance or undergo strenuous activity. An acceptable outcome using an extracapsular suture technique can often be achieved even in large dogs if their lifestyle is sedentary or undemanding. This same pet may develop severe osteoarthritis and have poor function if faced with strenuous activity on a routine basis. I recommend a TPLO in large dogs expected to reach a high level of athletic ability or activity. In large dogs having a more sedentary lifestyle, I recommend a traditional extracapsular or intracapsular technique. Duration of Injury In my opinion, it is always advantageous to repair anterior cruciate ligament (ACL) tears as soon as possible after the initial injury. When repaired in the acute phase, more surgical options are available, the surgical procedure is easier and less time-consuming, less bleeding occurs and less secondary joint disease has occurred including meniscal tears and osteoarthritis. Chronic ACL tears often need little surgical stabilization due to the presence of a large medial buttress of fibrous tissue that acts to stabilize the joint. Unfortunately, this tissue also acts to decrease range of motion and function of the joint also. Techniques used for early surgical repair include traditional extracapsular and intracapsular techniques, as well as TPLO. Surgical repair in the chronic ACL-deficient patient may involve a clean-out only; this generally involves partial meniscectomy and synovectomy if synovial hyperplasia is marked. The stifle is also stabilized in the chronic ACL tear patient if needed. Type of Injury Tears of the ACL typically are categorized as complete or partial. Complete tears are generally easier to diagnose due to the presence of cranial drawer and tibial thrust with the tibial compression test. Partial tears typically have less instability, usually having cranial drawer only when the stifle is positioned in flexion. It is important to visualize the intraarticular structures, particularly the menisci, with either type of tear. Arthrotomy or arthroscopy accomplishes this. Meniscal tears can occur with partial or complete ACL tears, but are more common with complete tears. The most common type of meniscal injury is a bucket-handle tear of the medial meniscus. It is also interesting to note that partial tears, with little demonstrable instability, may have substantial osteoarthritis at the time of diagnosis. This indicates that gross instability is not the only cause of osteoarthritis- biologic reactions associated with the degenerating ACL and subsequent micro-instability are likely occurring. Although to early to definitively tell at this time, TPLO may be an ideal treatment for partial ACL tears as a means of decreasing stress and strain on the ligament associated with chronic tibial thrust. I generally treat small dogs having either a complete or partial ACL tear with an extracapsular prosthetic ligament. I try to perform a TPLO on all large dogs with a partial ACL tear. In large dogs with a complete ACL tear, I will use a TPLO or traditional extracapsular or intracapsular technique depending on factors described above and below. Amount of Instability Acute complete tears are associated with obvious cranial drawer and tibial thrust with the tibial compression test. Surgical stabilization with a traditional technique or TPLO should be performed as soon as possible to decrease the chance of developing a meniscal tear or osteoarthritis. Partial ACL tears or chronic complete ACL tears often have little instability when assessed grossly. Micro-instability is likely present resulting in biomechanical changes during stifle range of motion and weightbearing. Consideration should be given to TPLO in these patients, especially if a reason for persistent lameness, such as a meniscal tear, is not seen during arthrotomy or arthroscopy. Tibial plateau leveling decreases stress and strain on the ACL by transferring load to the posterior cruciate ligament during weightbearing. This transfer of load seems to be associated with a clinical improvement in function and decreased stifle pain. Surgical Repair of the Cruciate-Deficient Stifle Surgical repair is generally recommended for dogs suffering partial or complete ACL tears due to the high likelihood of developing DJD and pain if the stifle is left unstable. It is important to understand that gross instability may not be evident in some partial tears, but micro-instability can still lead to progressive DJD. Although the TPLO procedure is quickly becoming the technique of choice for treatment of the cruciate-deficient stifle, it is important not to abandon traditional techniques of stabilization. Extracapsular suture techniques, fibular head transposition and intracapsular ligament replacement can lead to a successful outcome in 80-90% of patients. In addition, these techniques tend to cost less, giving owners another option if a more costly procedure cannot be performed. Concepts of Extracapsular Stabilization Surgical repair can be performed using a standard parapatellar arthrotomy or may be arthroscopic-assisted. Arthroscopic-assisted repair generally has less morbidity due to less invasion of the joint capsule and periarticular musculature. Extracapsular and intyracapsular repairs have been used successfully for repair of the cruciate-deficient stifle. Extracapsular techniques include prosthetic ligaments ( many different variations), TPLO and fibular head transposition. The cruciate-deficient stifle in the dog can be adequately stabilized using a combination of arthroscopic evaluation, debridement and percutaneous or open placement of an extracapsular prosthetic ligament. The prosthetic ligament is composed of either monofilament or braided suture material. I usually use either monofilament nylon, Ethibond, or a braided material such as Mersilene. The advantages of this technique include its minimally invasive nature, low patient morbidity, and good long-term outcome. The disadvantages include the expense of arthroscopic equipment, increased surgical learning curve, and increased surgical time compared to a standard open, extracapsular repair technique. This method of repair does not return all dogs to normal function, but does compare favorably with other previously described techniques. Remnants of the torn anterior cruciate ligament (ACL) are removed and a partial meniscectomy is performed arthroscopically if a medial meniscal tear is present. The stifle is stabilized using an extracapsular prosthetic ligament anchored proximally in the caudolateral surface of the lateral femoral condyle using one or two #5 suture anchors (Bone Biter, Androcles, Inc., Warsaw, IN), and distally in the tibial tuberosity through a 2.0 mm bone tunnel. A second suture anchor can also be used for the distal attachment. It is important to place the prosthetic ligament as isometric as possible. The suture anchor is placed through a small incision over the lateral femoral condyle. The prosthetic ligament is tunneled percutaneously to the bone tunnel. The scope and instrument portals are used to assist placement of the prosthetic ligament. This technique can also be performed very effectively using a standard open arthrotomy. Concepts of Intraarticular Repair Intracapsular ACL ligament repair is possible arthroscopically by two techniques (as described by Whitney and Hulse) or by an open arthrotomy as described by Hulse. The arthroscopic technique described by Whitney is similar to that used in man and utilizes an intracapsular autograft or allograft in combination with an interference screw or transfixation pin. Hulse's arthroscopic-assisted intraarticular technique utilizes a patellar tendon/fascial lata autograft placed in the "over-the-top position" and anchored by suturing to the lateral retinaculum. Hulse's open technique is performed in a similar fashion, but a standard arthrotomy is used to evaluate and treat the intraarticular structures, rather than arthroscopically. Concepts of TPLO Procedure Tibial Plateau Leveling Osteotomy (TPLO) is a relatively new and innovative surgical treatment for the cranial cruciate ligament-deficient canine stifle. The stifle joint is stabilized by both passive (ligaments, menisci, joint capsule) and active (muscles and tendons) constraints. The cranial cruciate ligament (CrCL) functions as a passive constraint to cranial tibial translation, stifle hyperextension, and excessive internal rotation of the tibia. Historically, most surgical treatments for CrCL deficiency have sought to re-create a passive constraint similar to that of the original CrCL using some combination of intracapsular autografts/prosthetics, extracapsular imbrication, or advancement of the fibular head and associated lateral collateral ligament. While traditional surgical procedures have focused on re-creation of the passive constraints of the stifle joint, the TPLO is based more on the active constraints of the stifle joint. The TPLO procedure is founded on the question, "why is the CrCL needed as a passive constraint?" Asked another way, "where do the forces and moments which cause pathologic stifle instability originate"? Conceptually, IF we can adequately diminish these forces and moments, the active constraints of the stifle may control these instabilities to the degree that the CrCL is not needed as a passive constraint. Ground reaction forces and extensor muscle forces during weight bearing generate compressive forces on the articular surface of the tibia. Because of the caudally-directed slope of the tibial plateau, tibial compression generates a cranially-oriented shear force that induces cranial tibial translation in CrCL deficient stifles. The shear component of the compressive force on the tibia, called cranial tibial thrust (CTT) , is passively constrained by the CrCL and the caudal horn of the medial meniscus. The CTT is proportional to the slope of the tibial plateau. Progressive decreases of the slope of the tibial plateau diminish the CTT to a point where there are incremental increases in reliance upon the caudal cruciate ligament as a passive constraint to caudal tibial subluxation. The intent of the TPLO surgery is to attain a tibial plateau slope where cranial tibial thrust can be effectively controlled by the active constraints of the stifle with minimal reliance upon the caudal cruciate ligament as a passive constraint. Because the CrCL also functions to passively constrain excessive internal rotation of the tibia, we must logically question the source of these internally rotatory moments and the role of the TPLO procedure in functionally controlling them. Slocum introduced the concept of limb malalignment as a leading contributor to internal rotational moments acting about the stifle. That is to say, a dog with a "bowlegged" posture (due to tibial or femoral varus) and a "pigeon-toed" stance (due to internal tibial or femoral torsion) experiences dramatic internal rotatory moments acting about its stifle as compared to a dog with a more "normally" aligned pelvic limb. In presentation of their data at this meeting last year, Warzee et al showed leveling of the tibial plateau (rotation of the plateau about a mediolateral axis) has relatively little effect on the rotatory instability of the stifle. Slocum has described limb-alignment adjuncts to the TPLO procedure to control excessive rotatory moments acting about the stifle in dogs with limb malalignment. Meniscal Injury The menisci should be examined in all patients having a complete or partial ACL tear. It is often tempting to place an extracapsular stabilizing suture and skip this step in small dogs not having a "meniscal click"; a word to the wise- meniscal tears are very common and are not always associated with an obvious "click". Persistent pain and lameness will occur in dogs having a meniscal tear left untreated. Always examine the intraarticular structures of the joint, either by arthrotomy or arthroscopy. Partial meniscectomy or ablation is preferable to complete meniscectomy due to the important stabilizing role played by the menisci. Patient Morbidity In this day and age, most veterinarians and pet owners are very cognizant and concerned about postoperative pain management. The best way to reduce postoperative pain is to reduce surgical trauma, employ use of perioperative analgesics and antiinflammatories, and encourage early return to function using physical therapy immediately postoperatively. Arthroscopic operative techniques reduce postoperative morbidity in people and dogs due to their minimally invasive nature. Use of narcotic analgesics and NSAID preoperatively and postoperatively provide optimal therapeutic pain control. Epidural analgesia can also be effective for the first 24 hours postoperative. An added advantage of preoperative and epidural analgesia is the ability to reduce the amount of anesthetic necessary to maintain a surgical plane of anesthesia. Postoperatively, early return of function should be encouraged in a controlled fashion. Range of motion physical therapy exercises, cold therapy and hydrotherapy are often helpful. Early return to function helps maintain muscle mass and joint flexibility. Postoperative Management The type of ACL repair chosen may depend on the expected ability of the dog and owner to comply with controlled postoperative activity. An intracapsular graft may not be the best choice if the patient can not be controlled adequately for 5 months postoperatively. This technique can be very successful if the graft can be revascularized, but this will not occur if excessive stress and strain are placed on the healing tissue. This technique also may not be ideal if a postoperative bandage can not be maintained and changed responsibly. A TPLO may be the ideal technique in dogs with osteoporosis or in older active dogs where bone healing may be slower. Screw loosening or implant failure can occur if bone healing is delayed. I generally recommend early physical therapy with all types of ACL repair to help maintain muscle mass, joint flexibility, and encourage early bone healing, in TPLO patients. GETTING CREATIVE WITH EXTERNAL FIXATORS
Clinical Performance of External Skeletal Fixation: The objective of this section is to introduce concepts and techniques relative to transfixation pins, external connecting bar, and pin clamp. Strength and stiffness of the fixator-bone composite is determined by a number of factors including frame configuration, pin number, pin size, pin placement, bar placement, fracture configuration, and material from which the fixator is made. In general, the greater the size and number of bars connecting the pin assemble, the greater the strength and stiffness of the fixator. In addition, since bones are subject to bending in two planes (mediolateral and craniocaudal) biplanar fixators are more effective in resisting physiologic bending loads than are fixators with connecting bars in the same plane. Static strength evaluation of different external fixator configurations showed Type 1a, Type 1b, Type 11, and Type 111 external fixators to be successively stronger in resisting bending, axial compression and torsion. The greater the number of pins per fragment, the greater the stiffness and surface area over which to distribute stress at the pin-bone interface. This is true up to 4 pins per fragment. Beyond this number, the amount of stiffness increase is negligible. Studies also indicate that pin diameter has an effect on stiffness and stress at the pin-bone interface. One pin should be placed 2cm proximal to the fracture and one pin placed 2cm distal to the fracture. The closer these pins are placed on either side of the fracture, the shorter the distance between connecting clamps on the external bar. The proximal and distal pins are placed in their respective metaphysis while remaining pins are spaced evenly in the proximal and distal fragments. The external fixation bar must be placed as close to the bone as is possible without the clamps or bar impinging on the skin surface. Pin implantation is done with a low speed power drill. Considerable emphasis has been placed on pin design with the rekindled interest in external fixators. A recent clinical study compared the use of threaded pins and smooth pins in clinical patients. Limb use, patient comfort, and stability at the pin-bone interface were increased when threaded pins were used alone or in combination with smooth pins. The most common failure mode of external fixation failure is premature loosening of fixation pins. The cause of premature loosening is bone resorption at the fixation pin-bone interface. This may be the result of one of two factors acting alone or in combination: 1. local bone damage, 2. micromotion at the fixation pin-bone interface. Extensive bone resorption Principles of External Fixator Application Insertion of fixation pins. The external fixator is no stronger than the attachment of the external frame to the bone; therefore, care taken during insertion of the fixation pins is vital if consistently successful results are to be achieved with external fixation. Proper percutaneous pin placement is accomplished by making a small 1 cm longitudinal skin incision over the proposed pin site. A hemostat is then used to bluntly dissect through the soft tissue down to the bone. The goal is to atraumatically create a soft tissue tunnel large enough to prevent soft tension upon the fixation pin when it is placed. An effort should be made to create soft tissue tunnels between large muscle bellies rather than through them where possible. With a hemostat in place to retract soft tissues, the fixation pin is inserted through the soft tissue tunnel down to the bone. The pin should be drilled into the bone across its greatest cross-sectional diameter with a slow-speed power drill (~150 rpm). Alternatively, a hole may be predrilled with a twist drill bit (~1 mm smaller than the fixation pin), followed by placement of the pin into the predrilled hole using a handchuck or slow-speed power drill. Application of unilateral-uniplanar (Type Ia) fixator configurations. Unilateral- uniplanar fixators are usually applied to the radius or tibia in a craniomedial to caudolateral plane; whereas, applications to the femur or humerus are usually in a lateral to medial plane. A unilateral-uniplanar configuration is started by placing a half-pin in the desired plane in the proximal aspect of the proximal bone fragment. The pins must penetrate both the near and the far cortex of bone. The fracture is then reduced (open or closed) and a half-pin is inserted into the distal aspect of the distal bone fragment. With an appropriate number of fixation clamps on the connecting bar (to accommodate subsequent placement of fixation pins) the proximal and distal pins are connected with the bar. There must be at least 3 fixation pins proximal and 3 pins distal to the fracture when a fixator is used as the primary fixation. The desired number of half-pins are then placed directly through the pin clamps and engaged into the bone and the clamps are tightened. Application of bilateral-uniplanar (Type II) fixator configurations. Because of the adjacent body trunk, bilateral configurations cannot be placed on the femur or the humerus. Bilateral-uniplanar configurations applied to the radius or tibia are usually placed in a medial to lateral plane. The most proximal pin is inserted first, the fracture is reduced, then the most distal pin is inserted. The most proximal and distal fixation pins are inserted as full-pins. With an appropriate number of fixation clamps on each connecting bar, the proximal and distal pins are connected with each of the connecting bars (1 medially and 1 laterally) and the clamps are tightened. Pins are then placed directly through the pins clamps either as full-pins or half-pins as desired. Accurate positioning of the most proximal and most distal pins in the same frontal plane greatly assists the placement of subsequent full-pins. Application of bilateral-biplanar (Type III) fixator configurations. As previously discussed, bilateral configurations cannot be applied to the femur or humerus because of the position of the body wall. Application of type III fixators to the radius or tibia requires nothing more than a bilateral-uniplanar frame as previously described in a medial to lateral plane followed by application of a unilateral-uniplanar frame in a cranial to caudal plane. Concept of Balanced Osteosynthesis When the bone is fractured, physiologic loads produce the same internal stresses as when the bone was intact. However, with the loss of bone integrity, there is no resistence to stress and high levels of micromotion (strain) are produced in the fracture planes. Micromotion within the fracture planes affects bone union and determines the type of tissue which can survive and proliferate according to the interfragmentary strain hypothesis. This hypothesis proposes that pluripotential cells are responsive to local micromotion (strain levels) within a fracture gap. Different tissue cells are able to withstand specified levels of deformation (stretching) beyond which they are unable to survive. Granulation tissue can withstand 100 per cent deformation before failure. Cartilage, fibrocartilage, and fibrous tissue withstand 10 per cent deformation and bone 2 percent deformation before respective tissue types are unable to survive within the fracture gap. Bone formation with 5% microstrain Therefore, the amount of micromotion within a fracture plane must be low enough to allow formation of bone tissue (direct bone union) or the formation of tissues with increasing mechanical strength and stiffness; granulation tissue > fibrous or fibrocartilage tissue > bone (indirect bone union). Control of interfragmentary micromotion is achieved by a combination of two factors: application of a stabilizing system and formation of biobuttress (callus). The decision as to which stabilization system to apply is made by assessing patient mechanical, biologic, and clinical factors which influence outcome. Mechanical factors influencing outcome are those affecting degree of implant loading and those affecting fracture reconstruction. Mechanical factors affecting degree of implant loading are important because excessive physiologic loads can cause implant breakage or excessive implant deflection. If the implant deflects (bends) excessively, micromotion at the implant bone interface occurs. If micromotion between the bone and the implant is too high, bone resorption will result as a consequence of high strain between the implant and bone. The end result is lysis surrounding the implant and premature implant loosening. Mechanical factors affecting implant loading are 1. the intended function of the implant and 2. an estimate of the degree of implant loading until bone union occurs. An implant can function as a compression device, an alignment device, or as a buttress system. When an implant functions as a compression device, compression is applied across the fracture line(s) which then rigidly stabilizes the fracture and allows physiologic loads to be carried by the bone column immediately after surgery. As such, there is maximal load sharing between the implant and bone column which lowers the stress on the implant and its connection to the bone. Both of these factors lead to a low incidence of implant failure. When the implant functions as an alignment system, the fracture has been reduced and contact between the fragment ends is maintained by the implant. Contact of the fragment ends allows some physiologic load to be carried by the bone but a greater percentage is carried by the implant. In this situation, there is more deflection of the implant and stress generation at the implant bone interface. Increased stress on the implant and its connection to the bone makes cyclic implant breakage and premature loosening more likely. If the implant serves as a buttress, the bone ends are not in contact and the implant carries the entire physiologic load until biobuttress (callus) is formed. As a buttress, the stress on the implant and its connection to the bone are very large which makes implant failure more likely. It is imperative that a strong implant be used and that every effort made to enhance (cancellous bone graft) and preserve the biology (closed reduction, OBDT) of repair. Other mechanical factors are those estimating the degree of implant loading. For example, the presence of single or multiple limb injury, size of the patient and activity of the patient. Mechanical factors affecting fracture reconstruction relate to the concept of interfragmentary strain. High interfragmentary strain levels slow or impede bone formation where as lower interfragmentary strain levels favors bone formation. Interfragmentary strain is defined as the change in fracture gap width divided by the original fracture gap width. This dictates that single fracture lines which have a small original gap width concentrate motion and have high interfragmentary strain levels. Longer fracture gaps such as that seen with comminuted fractures have a larger original fracture gap width. As such, interfragmentary strain is distributed over a larger area and is lower than that seen with single fracture lines. The level of interfragmentary strain will vary dependent upon the treatment method made by the surgeon. When the surgeon chooses to anatomically reduce a fracture, he\she creates a single fracture line with a small original gap width. This is usually the case when treating a transverse or oblique fracture. Reducing these types of fracture creates a situation where interfragmenatary strain is high under normal physiologic loading. If left unchecked, high interfragmentary strain could slow or impede bone healing.Therefore, with single fracture planes absolute rigidity is ideal to eliminate high interfragmentary strain levels. Rigidity is derived from one of two sources: 1. Implant system (compression plate, rigid ESF, interlocking nail) or the rapid formation of biobuttress to bridge the fracture plane. With comminuted fractures high interfragmentary strain is produced if the surgeon chooses to anatomically reduce fragments (reducible comminuted fracture). If the fracture has been reduced, reduction of interfragmentary strain (motion) must be achieved in the same manner as if one were treating a transverse or short oblique fracture. As discussed above, this is by application of a rigid implant system and\or by the formation of biobuttress (callus). If the surgeon chooses not to reduce the fracture fragments but to buttress the fracture (non-reducible comminuted fracture), the longer original gap width favors lower interfragmentary strain and bone formation. In this situation, the implant is subject to very high loading until biobuttress is formed. The surgeon must choose an implant with adequate strength and stiffness and facilitate the rapid formation of biobuttress. Biobuttress formation is facilitated by assuring minimal injury to the soft tissue envelope during surgery and placement of an autogenous cancellous bone graft. Preservation of the soft tissue envelope is best accomplished by using a closed reduction technique or minimally manipulating the fracture area (OBDT) if open reduction is chose. Biologicic factors influence the rate of bone healing and therefore estimate the time which the implant system will share physiologic loads with the bone column (compression plate) or carry all the physiologic load until the biobuttress forms (non-reducible fracture). Biologic factors which influence time to healing are many. One of great importance is the age and general health of the patient. Other biologic factors include open vs closed fracture and low energy or high energy fracture. If the fracture is open and/or a high energy fracture (gunshot) one can assume a significant degree of soft tissue injury. In terms of bone union, this simply means prolonged healing and that the implant-bone construct must remain rigid for revascularization with fragile neovascularization. Additionally, the implant-bone construct must remain rigid for a long period of time. Conversely, with a closed or low energy fracture, less soft tissue damage is present so bone union can proceed more rapidly. Another biologic factor is if the fracture must have open reduction or if it can be stabilized through closed reduction. If the fracture must be opened, more vascular damage is incurred which will delay bone healing when compared to closed reduction. Also, if the fracture must have open reduction, operative time becomes important; longer operative times translate into vascular damage and possible postoperative infection. The location of the fracture as the specific bone and location of the fracture within the bone are important biological considerations. For example, distal radial and ulnar fractures are a recipe for non-unions in the toy breeds of dogs. Even though the fracture may be a load sharing transverse fracture in a younger patient and caused by a low velocity impact, the treatment of choice is rigid bone plating. If a fracture occurs in the metaphysis or epiphysis, the cancellous bone dictates more rapid bone union and fixation with less longevity (be careful here; you must also consider articular fractures and the comfort of the patient with the implant in that the fracture is near or involves an articular surface). Clinical factors are important in developing a fracture fixation plan. A client which is not observant and does not wish to participate in the post-operative management is not the client to have care for an external fixator. The same is true for an un-cooperative patient. If he or she is uncontrollable, then an external fixator is not a wise choice. It is vital to consider postoperative limb function. For example, if your primary fixation has failed and fracture disease is becoming apparent, you must choose an implant system which gives maximal comfort and limb use postoperatively. PRACTICAL TREATMENT OF JOINT LUXATIONS AND LIGAMENT INJURIES
Ligamentous injuries occur frequently in dogs and cats. Almost any diarthrodial joint is susceptible to ligamentous injury. These injuries are classified as grade 1,2 or 3 sprains. The consequence of damage to ligaments may be minor, as in a grade 1 sprain, or major, as in a grade 3 sprain. Disruption of the medial glenohumeral ligament can lead to shoulder instability and luxation. Elbow dislocations are associated with collateral ligament tears. The carpus and tarsus may sustain injuries to the collateral, talocalcaneal, palmar or plantar ligaments. Coxofemoral dislocation requires tearing of the ligament of the head of the femur. Lastly, the stifle is the most common joint affected by ligamentous injury. Disruption of the cranial cruciate ligament is probably the most common injury seen in dogs and also is frequently diagnosed in cats. Other ligamentous injuries in the stifle include caudal cruciate, collateral ligament and multiligamentous tears. Treatment of these conditions vary depending on the severity of injury and include exercise restriction, external coaptation, primary ligament repair, ligament augmentation, transarticular external fixation, arthroplasty and arthrodesis. Structure and Function Ligaments are composed of longitudinal bundles of collagen fibrils that form a bridge between and attach to adjacent bones. Ligaments that support diarthrodial joints of the limbs have important kinematic, biomechanical and neurosensory roles in both guiding and protecting joint movements.1 Some ligaments are discrete bands of tough fibrous tissue, while others exist as inconspicuous thickenings within joint capsular tissues. Ligaments may have subunits of collagen bundles that function differently depending on the position of and loads placed on the joint. Neurovascular structures are found in ligaments, but at a decreased presence as compared to other musculotendinous tissues. Pathogenesis and Classification Damage to ligaments most commonly occurs following substantial trauma. Ligament damage may occur in combination with substantial soft tissue wounds, such as is seen with shear wounds to the hock, or from excessive force placed across a joint. If external forces exceed the tensile strength of the ligament, disruption of the collagen bundles results, leading to various degrees of instability. Ligaments are very inelastic and collagen fiber bundles become permanently deranged after 10% elongation.2 Ligament injury is classified as grade 1, grade 2 or grade 3. A grade 1 injury is associated with disruption of relatively few collagen fibrils and little functional compromise. This type of injury is commonly seen with mild collateral ligament injuries of the carpus and tarsus. The ligament is grossly intact. Palpable or radiographic instability is likely not apparent. Diagnosis of a grade 1 injury is made based on history, pain on palpation and stressing of the joint, and evidence of mild soft tissue swelling at the site of injury. Conservative treatment of grade 1 injuries is generally successful. A grade 2 injury has greater amount of collagen damage, resulting in functional deficits and joint instability. Increased swelling and hematoma formation is seen. Collateral ligament injuries of the elbow, carpus, stifle and tarsus are often associated with grade 2 injury. Documentation of instability can generally be accomplished by stress radiographic views. It is often helpful to compare radiographs of the abnormal to the normal joint. A significant amount of the ligament has been disrupted with grade 2 injury, but a portion of the ligament remains intact. Grossly, a portion of the ligament may appear torn or simply stretched. Surgical treatment of this type of injury is generally preferable, although some grade 2 injuries with mild instability can be treated successfully with conservative management. A grade 3 injury is associated with complete tearing of the ligament, resulting in total loss of ligament function. Palpable and radiographic instability is readily evident. This type of injury is commonly associated with subluxation or dislocation of the joint (shoulder, elbow, carpus, hip, stifle, tarsus). Surgical intervention is strongly recommended to increase the chance of attaining adequate stability for good joint function. Treatment Grade 1 Ligament Injury Initial management should include application of ice to the affected area to reduce pain, swelling and hematoma formation. A soft padded bandage is not absolutely necessary, but can be used subsequently to reduce pain, control swelling and give support to the joint. Exercise should be restricted to minimal walking for 2 weeks, then short leashwalks for additional 2 weeks. Concommitant use of nonsteroidal antiinflammatory drugs can be considered to provide additional analgesia. Return to normal exercise is permitted after 4 weeks if resolution of clinical signs occurs and joint stability is present. Grade 2 Ligament Injury Initial management should include application of ice to the affected area to reduce pain, swelling and hematoma formation. If minimal instability is present, external coaptation for 3-4 weeks can be considered. Exercise should be restricted to strict confinement for 2 weeks, then short leashwalks for additional 2 weeks. Leashwalks should become progressively longer over the next 2 weeks, with short trots allowed if clinical function is satisfactory. Return to normal exercise is permitted after 6 weeks if resolution of clinical signs occurs and joint stability is present. If palpable or radiographic joint instability is present, surgical intervention is recommended. The ligament should be repaired primarily by application of a locking-loop or pulley-tendon suture pattern if possible.2 Augmentation of the ligament with a prosthetic ligament is beneficial, especially if disruption of the collagen fibrils is substantial. Prosthetic ligaments are made from heavy absorbable or nonabsorbable suture (O - #5) placed in figure-8 fashion, anchored at the ligament origin and insertion using metallic suture anchors, screws and washers, or bone tunnels. External coaptation is often necessary for 4-6 weeks postoperatively to protect the repair during the early phases of healing, especially in large or active dogs. Concommitant use of nonsteroidal antiinflammatory drugs can be considered to provide additional analgesia as needed. Exercise should be restricted to strict confinement for 2 weeks, then short leashwalks for additional 6 weeks. Leashwalks should become progressively longer over the next 4 weeks, with short trots allowed if clinical function is satisfactory. Return to normal exercise is permitted after 12 weeks if resolution of clinical signs occurs and joint stability is present. Grade 3 Ligament Injury If associated with a closed wound, initial management should include application of ice to the affected area to reduce pain, swelling and hematoma formation. Grade 3 ligament injury leads to severe instability of the joint, which often times allows dislocation to occur. Shear wounds are associated with marked damage and loss of soft tissues and bone and require aggressive management. Open wounds into the joint space are often seen. The wounds should be cleansed with sterile saline directed under moderate pressure. A 60 cc syringe and 20 gauge needle can be used to cleanse the wound and provide mechanical debridement. Additional sharp debridement should be used as dictated by the condition of the injured tissues. Appropriate bandaging technique is used to treat the wound (wet-to-dry bandage or nonadherent bandage). Surgical intervention is necessary with grade 3 injuries, but ligament reconstruction may be delayed until the wound is healthy and is beginning to develop granulation tissue. The ligament should be repaired primarily, if possible, by application of a locking-loop or pulley-tendon suture pattern if possible.2 Augmentation or reconstruction of the ligament with a prosthetic ligament is usually necessary. Prosthetic ligaments are made from heavy nonabsorbable suture (O - #5) placed in figure-8 fashion, anchored at the ligament origin and insertion using metallic suture anchors, screws and washers, or bone tunnels. If the soft tissues are severely compromised or if extensive infection is suspected, a transarticular external fixator can often times be used without reconstructing the ligament. The fixator should be maintained for 6-8 weeks if possible, however, premature fixator pin loosening often leads to earlier removal of the device. Precise ligament reconstruction is preferred if possible, External coaptation is often necessary for 4-6 weeks postoperatively to protect the repair during the early phases of healing, especially in large or active dogs. Transarticular fixators provide excellent adjunctive stability and can be used for 2-4 weeks to provide additional support during the early healing phase. The potential disadvantage of using an external fixator is the inability to allow passive range of motion postoperatively, which will lead to a marked decreased range of motion following removal of the fixator. Physical therapy of the affected joint will usually allow return the joint to satisfactory function. Concommitant use of nonsteroidal antiinflammatory drugs can be considered to provide additional analgesia as needed. Exercise should be restricted to strict confinement for 2 weeks, then short leashwalks for additional 6 weeks. Leashwalks should become progressively longer over the next 4 weeks, with short trots allowed if clinical function is satisfactory. Return to normal exercise is permitted after 12 weeks if resolution of clinical signs occurs and joint stability is present. Suture Anchors and Prosthetic Ligament Reconstruction Soft tissue fixation to bone is a basic technique of orthopedic surgery for which a multitude of procedures and devices have been developed. Traditional procedures involve various configurations of bone tunnels and screws/washers. These techniques require more time and increased surgical exposure compared to new techniques in soft tissue attachment. Bone staples were developed to allow for decreases in these two critical areas, time and approach, but present other case management problems: pain necessitating staple removal, staple loosening and migration, and joint surface excoriation. Suture anchors were developed in the late 1980s and present distinct advantages over surgical restructuring of soft tissue with bone staples and screws/washers. Suture anchors have the advantage of a lower profile than staples and screws/washers which helps avoid interference and abrasion of articular surfaces and adjacent soft tissues during joint movement. They also can be more precisely placed to allow improved reattachment of ligamentous structures to their isometric origin or insertion. Their size and instrumentation for insertion allow for quick surgical application due to the ability to place them through a small surgical approach. Suture anchors are designed to work during the healing phase until scarring or tissue reattachment has occurred, a relatively short time period. Suture anchors can be used effectively for reattaching avulsed ligaments, tendons and joint capsule to bone, thus reestablishing stability to the involved joint.3 Soft tissue structures repaired primarily can also be augmented by placing figure-of-eight sutures through tissue anchors placed on each side of the disrupted structure. This technique has been used successfully for surgical management of traumatic coxofemoral dislocation and collateral ligament injuries of the elbow, carpus, stifle and hock, as well as for stabilization of the cruciate-deficient stifle. A large variety of suture anchor designs were developed for human application in the early 1990's and one design was developed and tested specifically for veterinary use, the BoneBiter® suture anchor (Androcles, Inc., Warsaw, IN). The BoneBiter® suture anchor is affordably priced, approximately one-third the cost of anchors used in human orthopedics. Clinical reports of applications for the BoneBiter® suture anchor include: coxofemoral repair - used along the dorsal rim and in one application as a toggle pin; extracapsular cruciate repair; collateral ligament repair in the elbow, stifle, and hock; and in biceps tendon repair. This anchor is simple and quick to insert, requires minimal instrumentation and investment, and is effective. The BoneBiter® suture anchor is available in 2 sizes and allows placement of suture material up to size #5. A hole is drilled through the near cortex at the desired site of placement in the bone. The anchor is set, then inserted with the appropriate instrumentation. After insertion, the anchor lies in a subcortical position. The protruding suture can be used to anchor an avulsed ligament or to create a prosthetic ligament by attachment to a bone tunnel or second suture anchor in the adjacent bone. References
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