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Orthopedic Surgery Denis J. Marcellin-Little, DEDV, Diplomate ACVS, Diplomate ECVS Department of Clinical Sciences, College of Veterinary Medicine North Carolina State University, Raleigh, North Carolina Cruciate Ligament Injuries: What's Going On? Cranial cruciate ligament (CCL) injuries represent approximately 10% of all orthopedic problems in dogs. CCL injuries affect a variety of patients. The majority of these patients are middle-aged large breed dogs without history of trauma that may be affected unilaterally or bilaterally. CCL injuries also occur in dogs with chronic patellar luxation, in obese dogs, in dogs with metabolic diseases such as Cushing's syndrome, hypothyroidism, or diabetes mellitus, in dogs with osteochondritis dissecans of the femoral condyles, and in canine athletes. CCL injuries may be partial or complete and may be associated with meniscal tears, generally of the medial meniscus. With the exception of these particular predisposing factors, the cause of cruciate ligament injuries in the majority of dogs remains unsolved. These injuries appear to be linked to a progressive breakdown of the ligament. The likelihood of having such injury in both stifle joints in affected dogs is high, ranging from 30 to 60% in various studies. Some theorize that the cause of this progressive breakdown is a biochemical degeneration of the ligament substance. This degeneration could be linked to aging, obesity, or other factors. Others theorize that the cause of that progressive breakdown is mechanical, as a consequence of the presence of a narrow trochlear notch (a theory that has now fallen out of favor), a steep tibial plateau slope (a theory currently in favor), or other mechanical factor. Tibial shape The shape of the proximal portion of the canine tibia is complex and has been poorly described. We recently completed a study aimed at assessing the orientation of the proximal tibial metaphysis and the medial tibial condyle in relation to the tibial shaft.1 The shapes of the proximal portion of the tibia vary between dogs. A cranial displacement of the proximal portion of the tibia during weight bearing is present in cranial cruciate-deficient canine stifle joints. Surgical alterations of the tibial plateau slope (TPS) have been performed to decrease the TPS and to eliminate the cranial displacement of the tibia present during weight bearing. These procedures may also be considered as a tool aimed at increasing stifle joint extension in dogs with limited extension, a problem that may be linked to the presence of an abnormally steep TPS. Tibial plateau slope The design and assessment of TPS alteration methods requires a precise and accurate TPS assessment method. The conventional method method for TPS assessment underestimated the TPS in a recent study.2 An alternative TPS assessment method relying on a line tangential to the cranial aspect of the medial tibial condyle as seen on a cranio-caudal radiograph was more accurate than the conventional TPS assessment method. Changing the tibial shape A variety of surgical methods may be used to decrease the TPS, including sliding curvilinear osteotomies, closing planar or chevron wedge osteotomies, and opening wedge osteotomies. The specific morphologic and geometric advantages and drawbacks of these various osteotomies are not known. Factors involved in assessing these osteotomies include potential cranial / caudal displacement of the distal fragment in relation to the proximal fragment, the ease of performing the osteotomy, the creation of angular or rotational deformities during correction, and the mechanical properties of the bone implant constructs. The ideal surgical procedure for stabilization of CCL-deficient stifle joints would be minimally invasive, technically simple, maintain or restore normal joint mechanics, would require limited postoperative rehabilitation, and would decrease or stop the progression of OA in operated stifle joints. Such surgery does not exist at this point. In recent years, a technique aimed at altering the shape of the tibia has increased in popularity. That technique, named tibial plateau leveling osteotomy (TPLO), is aimed at changing the distribution of forces placed on the stifle joint during locomotion: by decreasing the cranial displacement of the tibia in relation of to the femur (a process termed cranial thrust), the CCL-deficient stifle joint may function well despite the absence of active joint stabilization. The preoperative planning of TPLO requires the radiographic assessment of the slope of the proximal portion of the tibia in relation to the tibia shaft. The TPLO appears to be leading to good clinical results in the majority of dogs. Because of the residual instability in operated stifle joint, meniscal tear may occur after TPLO. For that reason, some excise or transect intact medial menisci when doing primary TPLO's. The complication rate after TPLO appears to be above 15% and include failure of fixation and loss of bone reduction, patellar tendonitis, rupture of the tibial crest, infections, and other complications. Tibial wedge osteotomies (TWO) have been performed with a goal similar to TPLO: decreasing the slope of the tibial plateau to eliminate the thrust of the tibia in relation to the femur that occurs when the dog bears weight. While TWO appear to lead to acceptable limb function. Little is know about their long-term benefits. Closing wedges: Closing tibial wedge osteotomies have been performed to adjust the TPS in dogs.3 Historically, these wedges were planar wedge osteotomies. These osteotomies are routinely performed throughout the world. Planar wedge osteotomies have the advantage to be technically simple. They have the disadvantages to lead to a cranio-caudal displacement of the functional axis of the tibia because the origin of the wedge osteotomy tends to be distal to the anatomic origin of angulation of the tibial plateau. This displacement impacts the actual functional TPS resulting from the corrective osteotomy. They also have the potential disadvantage to lead to rotational or angular deformities. Chevron wedge osteotomies have been used for approximately 3 years at North Carolina State University. These osteotomies include two planar cuts at an angle to each other. Chevron osteotomies are used in humans for corrective osteotomies, where they appear more stable than planar osteotomies and could decrease the likelihood of iatrogenic rotational and angular limb deformities.4,5 Opening wedges: Opening wedge osteotomies have been used to decrease the TPS of cranial cruciate-deficient stifle joints in dogs. The changes in TPS may be made progressively over a period of days to weeks, using hinged external skeletal fixation frames. We have used a hybrid hinged external skeletal fixator to treat approximately 25 patients without major complications and with acceptable clinical results. Compared to plate fixation, the use of these frames has the advantage to decrease the invasiveness of surgery, to potentially minimize the likelihood of iatrogenic rotational or angular limb deformities, to decrease the physiologic impact of sudden changes in TPS, and to enhance the geometric flexibility of TPS alterations if complex, non-linear wedges are created. Due to the lack of prospective randomized trials comparing various TPS alteration procedures to each other and to other conventional stabilization methods for cranial cruciate-deficient stifle joints, the relative advantages and drawbacks of various TPS alteration methods are not yet fully known. The use of closing and opening wedge osteotomy will influence the range of motion of CCL-deficient stifle joints. This may be used as an adjunctive form of treatment (in addition to limiting cranial thrust during stance) during treatment of CCL-deficient stifle joints with limited extension. In our experience, both closing and opening wedge osteotomies lead to clinically acceptable results in dogs. Joint extension The CCL is the limiting factor to stifle joint extension (and cranial translation and internal rotation of the proximal portion of the tibia). Hyperextension is a known cause of CCL avulsion. Dogs with steep TPS have less stifle joint extension than dogs with normal TPS (Marcellin-Little, unpublished data). The lack of extension present in dogs with steep TPS could lead to abnormal stress placed on the CCL during locomotion and particularly during gallop. This abnormal stress could lead to a progressive failure of the CCL. The impact of a CCL injury on stifle joint motion is poorly known. In patients with CCL injuries, extension could be increase because of the CCL deficiency (considering that the CCL limits extension) but could also decrease because of articular or peri-articular fibrosis, stifle joint effusion, and pain. It is therefore difficult to assess the true stifle joint extension in CCL-deficient stifle joint and it may be preferable to assess stifle joint extension on the opposite side, since that side is often intact and is likely to be identical to the affected side. Assessing TPS in both stifle joints is therefore important. I recommend considering the use of a tibial plateau leveling procedure in dogs with limited stifle joint extension (Table 1). Putting it all together… Unfortunately, there is no consensus on what surgical stabilization method is optimal in dogs. While we know that the majority of dogs treated with one of the procedures mentioned above will function better than they did before surgery, the specific benefits of each surgical procedure with regards to return to function and progression of OA have not been described and these surgical procedures have not been compared to each other. In the absence of a solid scientific basis for the choice of a specific surgical stabilization procedure, the choice of a specific method relies on subjective factors. I personally base the surgical recommendation for stifle joint stabilization on the tibial plateau slope and stifle joint extension angle (Table 1). Table. Potential factors for consideration in choosing a CCL surgical stabilization method
CCL, cranial cruciate ligament References
Timing Of Deformity Correction Bone deformities are very common in dogs. This is due to the fact that many dog breeds owe their identity to specific body types that are defined by the potentially-abnormal shape of their limbs and skull. These deformities fall under the umbrella of chondrodystrophy. Chondrodystrophy leads to an impaired growth of long bones but does not affect the growth of the axial skeleton. The severity and intensity of chondrodystrophy vary among breeds. For example, Basset Hounds are large dogs with severe chondrodystrophy and Jack Russell Terriers are a small to medium dogs with moderate to severe chondrodystrophy. The size of dogs and the severity of their chondrodystrophy greatly influence the type and timing of correction. The shape of the skull and mandible vary greatly among dog breeds. Some dogs (i.e., Boxers) have a normal appendicular skeleton but have decreased skull and mandibular growth. Other dogs (i.e., Pekingese) have a combination of decreased growth of long bones and skull/mandible. Dogs with impaired mandibular growth appear greatly predisposed to malocclusion. Injuries to growth plates (physeal fractures) represent another significant source of limb deformities. One report found that physeal fractures represented approximately 20% of all fractures observed in a group of more than 500 dogs. Some physes appear much more likely to have impaired growth after injuries than other physes. For example, fractures involving the distal humeral physis do not appear to lead to humeral deformities but fractures involving the distal ulnar physis most often lead to antebrachial deformities. FACTORS INFLUENCING THE TIMING OF DEFORMITY CORRECTION The most significant factor influencing deformity correction is growth potential. Growth is linked to age. Limb deformities are most devastating when they are present in very young dogs (i.e., pup less than 3 months old). The timing of classic orthopedic problems leading to limb deformities is presented in Table 1. Physeal injuries, fortunately, occur relatively late in growth because they often result from trauma occurring when pup are moving around and explore their surroundings. A significant number of physeal fractures occur when pup jump or get dropped from the arms of people unfamiliar with holding dogs. Table 1. Classic types of canine limb deformities and their anticipated age of onset.
* Commonly: caudo-lateral radial head luxation. Less commonly: medial humeral head luxation, dorsal hip luxation. Growth may be a positive or negative feature of the management of limb deformities. In other words, growth may be beneficial with regards to self-correction of a deformity in a young dog or growth may worsen an existing problem by potentially increasing a length deficit, abnormal angulation, or the subluxation of a joint. With some deformities, the problem is focal and self-limiting (i.e. a physeal fracture heals without premature closure or a periosteal response secondary to hypertrophic osteodystrophy subsides after a few weeks); with others, the problem is ongoing (i.e., a premature physeal closure). Having growth problem that is temporary or permanent will greatly impact the anticipated evolution of the deformity. Corrective growth is a type of growth that corrects specific components of a deformity. For example, if an angular limb deformity occur early in during growth and is self-limiting, the body may correct that deformity. This is most likely to occur for medial lateral (varus / valgus) deformities. For example, a 10-week-old pup gets a green-stick fracture of the medial tibial cortex leading to a 20° valgus deformity. With corrective growth, that valgus deformity may become a 5° valgus angulation. Corrective growth does not appear to occur after 4 months of age in dogs. Compensatory growth occurs when a bone adjacent to a deformed bone has a change in growth that decreases the impact of the deformity. For example, the femur of a dog with a short tibia may be longer than the contralateral femur. The proximal epiphysis of a radius with a premature closure of its distal physis may show overgrowth. Overgrowth is generally limited to less than 5% of bone length. Joint subluxation greatly influences the timing of deformity corrections. The most common subluxations are distal humero-ulnar (i.e., after premature closure of the distal ulnar physis) that may lead to a delay or absence of fusion of the anconeal process and distal humero-radial (i.e., after premature closure of the proximal or distal radial physes) that may lead to a fragmentation of the medial coronoid process. In a report of experimentally-induced (radiation-induced) premature distal radial physeal closures in dog, significant damage to the ulnar articular cartilage was present in the elbow joint within two weeks of the physeal injury. This means that when joint subluxation is present or anticipated, deformity correction or management should be performed without delay. Carpal subluxation is also common occurrence with antebrachial deformities. The radiographic assessment of carpal congruity or subluxation is challenging. It may be more appropriate to diagnose carpal subluxations based on loss of joint motion (flexion) rather than radiographs. The presence of a radio-ulnar synostosis represents a clear emergency because with the significant difference in growth patterns between the radius and the ulna (most of the growth of the ulna originates from its distal physis, roughly half of the radial growth originates from its proximal and distal physes) a significant joint subluxation may occur within days. A significant number of radio-ulnar synostoses in patients with antebrachial deformities are unfortunately iatrogenic. They may occur after an ulnar ostectomy that damages the radius or the radio-ulnar interosseous space or ligament or from the placed of implants (bone screws, cerclage wires, Kirschner wires, external fixation pins) that connect the radius and ulna. It is critically important when dealing with antebrachial deformities early in life to avoid creating radio ulnar bridges, to monitor for their occurrence, and to treat them rapidly to avoid joint subluxation and secondary cartilage damage. Loss of range of motion in dogs with deformities may indicate the need for prompt therapy. It is important to assess the source of that loss of joint motion. It may be caused by joint subluxation, by an abnormal growth of musculo-skeletal soft tissues (i.e., short muscle-tendon complex in young dogs of hunting breeds, by a contracture of periarticular tissues, or by musculo-tendinous tethers associated with a primary injury or surgery. Loss of range of motion may lead to irreversible fibrosis or loss of limb use and may therefore increase the urgency of the management of a limb deformity. Angulation has a minor influence the timing of deformity correction. While a limb is functional, the angulation does not require immediate attention. Limbs generally remain functional when angulation is less that 25°. Length also has a minor influence on the timing of deformity correction. When a limb is functional, the management of a length deficit does not require immediate attention. Limbs tend to remain functional when length deficit is less than 20% of an affected bone. DECISION-MAKING Most limb deformities are the combination of multiple factors with variable urgency. For example, classic premature closures of the distal ulnar physis secondary to chondrodystrophy most often combine valgus and caudal angulation, external rotation, carpal joint subluxation (loss of carpal flexion), elbow joint subluxation (distal humero-radial subluxation). The most urgent aspect of these deformities is the elbow joint subluxation that should be addressed immediately. If the elbow subluxation is ? 3 mm, an ulnar ostectomy may be acceptable. As a general rule:
When Do I Use Circular External Skeletal Fixation? Deformity correction Circular external skeletal fixation (CESF) is primarily used to manage limb deformities. The key advantage of CESF on other forms of surgical management of limb deformities is its geometric versatility and its adjustability. The geometric versatility of CESF comes from the fact that wires and half-pins may be affixed to bones from any direction, that a wide range of wire and pin size may be used, that CESF systems may have a broad range of ring sizes, that connecting rods length and location is adaptable, and that rings or ring blocks may be hinged or angled in relation to each other. The adjustability of CESF comes from the fact that nuts on threaded rods may be adjusted after frame placement to increase the length of a specific connecting rod (motor of distraction) therefore opening or closing the angle between rings or ring blocks progressively and precisely. Nuts may also be turned to slide posts or ring blocks in relation to the rest of the frame leading to displacement of a bone segment or a fragment in relation to the rest of the bone. CESF is a complex form of fixation and its use should be limited to situations where their geometric versatility and adjustability are required to achieve specific goals. Patients with unifocal limb deformities without length deficit may be managed effectively using acute angular and rotational correction a fixation with a bone plate or a linear external skeletal fixator (Table 1). CESF is the only reliable method used in companion animals allowing progressive limb lengthening, and the precise, controlled, progressive displacement of one bone in relation to another to correct a joint subluxation (Table 1). The geometric versatility and adjustability of CESF is also useful when treating complex angular deformities (bifocal deformities, for example). CESF are useful when correcting juxta-articular angular deformities (i.e., originating in physes) because of their ability to secure small and short bone fragments using crossing tensioned wires and threaded half-pins. These factors make CESF the most precise and effective method used to treat complex developmental angular limb deformities in dogs.1 Table 1. Decision making in antebrachial deformity correction
Abbreviations: ESF, external skeletal fixation; Dist, distal; ML, medio-lateral; CC, cranio-caudal; sublux, subluxation *Limb deformities most often include several abnormal components. Their optimal management takes all abnormal components into account and relies on a treatment option that addresses all these abnormal components. Circular ESF is the only management option that can address all abnormal components of limb deformities. Fracture management CESF have specific advantages over other fracture fixation methods. Their geometric versatility makes them particularly useful in stabilizing juxta-articular fractures.2 This is achieved using two tensioned wires ranging in diameter from 1.0 to 1.5 mm and in tension from 0 to 60 kg, and one or two end-threaded half-pins ranging in diameter from 1.2 to 4.8 mm.3 The wires are placed immediately adjacent to the ring, 5 mm apart. Half-pins are one to two millimeters from the wires. This allows fixation of bone fragments ranging from 8 to 12 mm in length. This configuration is stiff and strong enough to allow fracture healing in all size dogs. Hybrid frames with one ring (used to secure a short bone segment) and one or two linear connecting rods (used to secure long bone segments) may be particularly useful for effective management of juxta-articular fractures. CESF are useful in treating open fractures because of the fact that implants are not present near contaminated and potentially infected tissues. CESF are also useful when treating fractures with bone loss, including gunshot trauma because the frame may be placed closed and hinged or modified using hemispheric washers to optimize fracture reduction and limb orientation.4 CESF are useful when treating non-unions because of their adjustability. The frame may be used to create transverse or longitudinal interfragmentary compression using sliding elements and olive wires. Interfragmentary compression and distraction stimulate bone growth. In some patients, one can compress then distract a non-union site to enhance bone healing. Limb sparing CESF are a useful option for limb sparing of patients with significant bone loss, particularly patients with osteosarcoma. This is achieved using single or double bone transport techniques.5 This method often requires performing an arthrodesis of the joint adjacent to original bone loss. Limb sparing using CESF appears to be an effective and cost-effective limb sparing method. References
What Is Biomodeling? This presentation focuses on the use of several modern engineering methods to enhance several aspects of the management of orthopedic problems in companion animals. Technology Image capture - Biomodeling is the use of computer modeling programs for biological applications. This presentation will focus on the authors' experience using biomodeling in veterinary orthopedics. Biomodeling is based on digital three-dimensional (3D) images of biological structures that can be rendered, viewed, manipulated, and physically reproduced. These 3D renderings may be created using a computed tomography (CT) scanning, electron beam tomography (EBT) scanning, magnetic resonance imaging (MRI), electron beam tomography, hand-held, or stationary 3D laser scanners (Table 1). CT and MRI scans are series of two-dimensional images. These series are imported into specialized software (i.e., Mimics, Materialise, Leuven, Belgium) and assembled into 3D rendering that can be magnified and rotated freely in space to allow precise assessments. Table 1. Digitization of biological structures for biomodeling
Abbreviations: 3D, three-dimensional. *Pixel size Model creation - The digital information contained in cross-sectional CT or MRI images may be imported into computer-aided design (CAD) software to make 3D renderings of biological structures. CAD is used to enhance the contrast of these images, eliminate data collection artifacts (i.e., beam hardening in CT scans), and select specific information for the creation of 3D renderings. The 3D rendering is oriented in space and a support structure may be created. 3D renderings may be kept at their original size or may be resized. Making half size models requires only one eighth of the material required to make a full size model because length, width, and depth are halved in a smaller model. Decreasing the size of the model may be necessary to make a model of a structure too large for specific manufacturing methods or to decrease the model cost. CAD may also be used to modify the 3D renderings to make models for investigative purposes. For example, markers may be placed on the shaft of a bone to accurately assess the orientation of portions of the models, markers may be placed on anatomic landmarks to assess their relative position when models are viewed, the models may be built up to optimize fit onto testing stations. Free-form fabrication - The creation of physical models based on 3D renderings is named free-form fabrication (FFF). Unlike most manufacturing processes that are subtractive processes, relying on removing material from a solid structure, FFF is an additive manufacturing process where material is added progressively in thin layers. The FFF software will slice the 3D rendering into thin slices (generally measuring approximately 0.1 mm) and will control the machine while it builds the model layer by layer. For that reason FFF is also named layered manufacturing. The term rapid prototyping is also used to describe FFF because it has been used in industry to create prototypes of tools, parts, or products. The prototypes may be used to verify a design, to assess the form, fit, and function of a part, to plan production and marketing, or to gather customer feedback. They may also be used for rapid tooling or to manufacture small batches of products. FFF became available in 1986. Approximately 25 different types of FFF methods are used, making models ranging from wax to titanium. Stereolithography apparatus (SLA) was the first commercially available FFF method (Table 2). SLA relies on an ultraviolet laser to cure a photopolymer. SLA is slow but precise. Its speed depends on the power of its laser beam. The maximal size of prototypes in SLA machines ranges from 250x250x250 mm to 500x500x500mm (VIPERsi SLA, 3D Systems, Valencia, CA). Wax FFF (Model maker II, Solidscape. Merrimack, NH) relies on a melted wax thermoplastic material printed layer by layer using inkjet technology. It is a high precision, low-speed process. 3D printing is a FFF process that projects a liquid binder on a powder (plaster, starch) using inkjet technology (Z 400, Z-Corp, Burlington, MA). 3D printing is rapid and relatively inexpensive. Electron beam melting (EBM), is a process projecting a 4 kW electron beam onto metal powder (EBM S12, Arcam AB, Mölndal, Sweden). Other FFF methods include fused deposition modelling, laminated object manufacturing, selective laser sintering, and laser engineered net shaping. Second generation models may be made using silicon molding methods (RTV). A silicon mold of a primary model is made and used repeatedly to inject soft or hard plastic materials. Table 2. Manufacturing methods for free-form fabrication
* Maximal size Clinical applications Diagnostics - FFF may be used for diagnostic purposes. Models enable clinicians to manipulate objects that are precise replicas of biological structures. This is of benefit for patients with limb deformities (Figure 1), fractures, neoplasms, abnormal vascular or lymphatic anatomy. Surgical rehearsal - FFF models may be used for surgical rehearsal. This is most commonly done on hollow SLA models filled with polyurethane (Figure 2) but it may also be performed on wax impregnated plaster models. This rehearsal is particularly helpful for the management of challenging limb deformities, including multifocal deformities, unusual deformities, juxta-articular deformities, deformities that may be difficult to assess on radiographs (i.e., femoral rotational deformities). The plastic models are used to perform specific corrective osteotomies and to select specific bone plates, interlocking nails or build external circular fixation frames that will later be used on the patient. It will also be of benefit for rehearsal before surgical management complex vascular anomalies (i.e., vascular networks of conjoined twins, intrahepatic shunts, arterio-venous fistulae, aneurysms). Custom implant manufacturing - FFF models are used to test the accuracy of custom implants used for joint arthroplasty, custom plating for limb sparing or the management of fractures with bone loss. Education The first medical applications of FFF were human anatomic models using for educational purposes. Models of normal and pathological tissues may be made non-invasively. Clients may better appreciate the nature of medical problems and understand planned medical procedures when models are made. When complex corrective osteotomies or limb sparing procedure are planned, having access to a model with internal or external fixation will help everyone conceptualize the nature of the surgical plan. References Harrysson OLA, Cormier DR, Marcellin-Little DJ, Jajal K. Rapid prototyping for treatment of canine limb deformities. Rapid Prototyping Journal; 2003, 9- 37-42. Arcam AB, Sweden www.arcam.com 3D Systems, Valencia, CA www.3dsystems.com Z-Corp, Burlington, MA www.zcorp.com Solidscape, Merrimack, NH www.solid-scape.com Further references available upon request: denis_marcellin@ncsu.edu BFX Cementless Canine Total Hip Arthroplasty The BFX cementless canine total hip prosthesesa achieve initial stability through press-fit and long term stability from bone ingrowth into porous bead surfaces. BFX prostheses have been commercialized since September 2003 as one of two application methods of the BioMedtrix Total Hip System. The system consists of Cemented Fixation (CFX®) and Biological Fixation (BFX®) applications. The prostheses are interchangeable due to a common bearing surface and common neck resection angle and level. The BFX system retained many of the features of Howmedica's PCA systemb that was in limited clinical use since 1988 (Table 1). The PCA system was used as a model to evolve to a new state of the art design. Because of the unequaled long-term clinical success of the PCA system,1,2 designers of the BFX system wanted to keep the strengths of the PCA system and improve on its weaknesses. Similarities between the BFX and PCA stems include body and neck length, proximal and distal canal fill, and having 45% of its proximal surface circumferentially beaded. The BFX system, however, has several key differences with the PCA system to address several perceived limitations: increased modularity, greater size availability, and an improved cup implantation procedure (Table 1). Table 1. Differences between the BFX and PCA cementless total hip arthroplasty systems
BFX Stem The BFX stem is available in seven sizes (#5 to #11, based on the diameter of their distal portion) with a design maintaining proportions between sizes (Table 1). It is manufactured from cast cobalt chrome with a neck inclination angle of 135°. Approximately 45% of its proximal surface is coated with sintered beads of a diameter ranging from 250 to 300µm that create a porosity of approximately 35%. Unlike the PCA stem that was curved to match the cranial curvature of the proximal portion of the femoral shaft, the BFX stem is straight, requiring a modified stem implantation procedure. The BFX stem is implanted using a series of broaches. The stem implantation relies on preoperative templating, accurate femoral head and neck excision, centralizing the broached by entering the femoral canal from the trochanteric fossa, and impacting incrementally larger broaches to result in press-fit stability of the stem. Final stem size is chosen based on the resistance to broaching during the procedure. The wide range of stem sizes enables surgeons to place BFX stems in dogs approximately 18 kilograms and over. BFX Cup The BFX cup is made of titanium alloy with an ultra-high molecular weight polyethylene insert (Table 1). The 24-, 26-, 28-, 30-, and 32-mm-diameter cups have a 17-mm inside diameter that matches standard BioMedtrix prosthetic heads and allow interchangeability with the cement fixation CFX total hip system. For the 17-mm head, four neck lengths (+0 , +3, +6, +9) are available to articulate with the cementless BFX cup. A 14-mm-diameter head is available for articulation with a 22-mm-diameter CFX or BFX cup. The appropriate BFX cup size is determined before surgery using templates. The acetabulum is prepared using accurately oriented reaming. After initial bone removal with a starter reamer, a finishing reamer is used to ensure press-fit stability. The cup geometry includes locking zones that maximize interference with the acetabular bed. The cup is impacted into the prepared bone bed using instruments designed to reproducibly achieve accurate alignment. A pelvic positioning device is used to consistently align the patient and provide reliable reference landmarks during the reaming of the acetabular bed and cup impaction. Final cup size is chosen based on the relationship of the reamer and the pelvis with regard to depth and dorsal coverage during the procedure. Clinical results The clinical results of the BFX procedure have been excellent. Principally mid-range stems (91% stems; #6, #7, #8, or #9) and small cups (80% cups; 22- or 24- mm-diameter) were used. Neck lengths were evenly distributed between +0, +3, and +6 mm. Bone ingrowth occurred into all cups and into all but one stem that had fibrous ingrowth. Stem subsidence was minor from 0 to 3 months and absent afterwards. The most common complication in our early clinical experience was femoral fissure or fracture that occurred during stem implantation (N = 14 of our first 42 stems). The rate decreased significantly when femoral broaching was initiated in the trochanteric fossa instead of the femoral neck osteotomy site (N = 2 of 32 most recent stems, P < 0.01). Femoral fissures were managed using one 1-mm-diameter double loop cerclage. Our clinical experience with the BFX hip prosthesis has been very positive overall. Templating is important to assess the anticipated maximal cup and stem sizes and to anticipate challenges resulting from abnormal anatomy, significant dorsal luxation, or significant new bone formation. A femoral canal entry from the trochanteric fossa is an important step enabling stem centralization and minimizing femoral fissures. Footnotes a. BFX® series hip prostheses, BioMedtrix, Inc., Boonton, NJ. b. Canine porous-coated anatomic (PCA®) hip system, Howmedica, Inc., Rutherford, NJ. References
Canine Total Knee Replacement: A Reality? Total knee replacement has been performed on purpose bred dogs for investigative purposes and as a custom surgery in a patient (Figure 1). A total knee replacement system will be made available to veterinarians in 2007. The surgery will include femoral and tibial components (Figure 2). Initially, the femoral component will be cementless fixation and the tibial component will be cemented. A cementless tibial component will be designed, tested, and assessed in 2007. Figure 1. Medio-lateral and cranio-caudal radiographs of the pelvic limb of a dog that received a total knee replacement 17 months earlier. The dog originally had a gunshot wound to his stifle joint that led to a nonunion of the medial femoral condyle and a medial patellar luxation (grade 4). A custom prosthesis was built that included a titanium metal augment aimed at replacing the missing medial femoral condyle and a titanium femoral stem that enhanced the fixation of the femoral portion of the implant. The femoral articulating surface was made of chrome cobalt. The tibial tray was made of ultra-high molecular weight polyethylene. The femoral and tibial components were fixed in placed using polymethylmethacrylate bone cement. The dog recovered well after surgery and resumed hunting three months after surgery (case report in review in Veterinary Surgery). The surgical procedure relies on precise preoperative planning with printed or digital template, a cranio-lateral surgical approach, and the use of specific alignment guides aimed at creating precise tibial and femoral cuts. Several interchangeable sizes are available for the femoral and tibial components. Orthopedic Problems In Cats While cats are relatively spared compared to dogs when it comes to bones and joint problems, they still suffer from specific bone and joint diseases and injuries. The lower likelihood of bone and joint problems in cats compared to dogs likely result from: 1.) the smaller size of cats compared to dogs. Most joint disease are linked to rapid bone growth and having a smaller size implies less rapid bone growth early in life than having a larger size, 2.) Having a different genetic selection pressure than dogs with less emphasis placed on specific breeds than in dogs; 3.) A probable lower likelihood of medical care in cats than in dogs; 4.) lower awareness of orthopedic problems in cats than in dogs among medical practitioners, including less knowledge on their prevalence*, the associated clinical signs, and the management of these orthopedic problems. The purpose of this presentation is to describe the relative frequency, clinical signs* and management options of the most common bone and joint problems in cats. Like for dogs and people, obesity is associated with an increased likelihood of developing orthopedic problem. In one study, obese cats was 4.9 times as likely to develop a lameness and 2.9 times more likely to be brought to their veterinarian for treatment of that lameness than their counterparts with normal weight.1 JOINT DISEASES Hip dysplasia* is relatively common in cats, unbeknownst to most medical professionals. In one study including 684 cats from 12 breeds, the prevalence* of dysplasia was 6.6%.2 Hip dysplasia appear to be breed dependent in cats. The radiographic* signs of the disease were changes present in the acetabulum* but were less likely on the femoral neck. Like in dogs, hip dysplasia appears to result from the presence of joint laxity* early in life.3 Cats with hip dysplasia may have a lameness of their pelvic limbs* or may be constipated.4 Fewer options have been used to manage hip dysplasia* in cats than dogs. Cats are generally manage conservatively in the short term and may undergo a femoral head ostectomy* is the clinical signs cannot be managed conservatively*. Unlike dogs and humans, total hip replacement is not performed routinely in cats. Patellar luxation* is a relatively common problem affecting the stifle* in cats. Affected cats often (71% in one study) have the problem in both pelvic limbs*.5 Patellar luxation and hip dysplasia appear to have a weak association. In one study, cats were three times more likely to have patellar luxation than to have either condition alone.5 Cats with patellar luxation show signs of lameness or decreased activity level. In our experience, patellar luxation with associated clinical signs is more likely to be present in overweight and obese cats than in cats of normal weight. In some patient, the patellar luxation is treated with surgery. The surgery is aimed at tethering the patella in the trochlear groove* of the femur. Idiopathic* osteoarthritis is present in cats, like their human counterparts. In a study involving 100 cats older than 12 years treated at the College of veterinary Medicine at North Carolina State University, 9 out of 10 cats had osteoarthritis.6 Among the patients with osteoarthritis, the elbow was affected in 64% of the patients, the shoulder in 21%, the hip in 7%, and tarsal joints in 7%.6 The clinical of osteoarthritis in cats include weight loss, anorexia, depression, urinating outside the litter box, poor grooming, and lameness.7 Dr. Hardie recommended managing osteoarthritis in cats using environmental changes and recommended using aspirin, butorphanol, corticosteroids, and nutritional supplements are used for chronic treatment of painful osteoarthitis in cats.7 TRAUMA Physeal* fractures - The long bones* have specific areas of cartilage where growth is occurring during the first 8 months of life. These are named growth plates or physes*. These physes are weaker than the rest of the growing long bones. When kittens undergo trauma (i.e., falling, being stepped on, being attacked by a dog), they may have physeal fractures. These physes are expected to ossify at approximately 8 month of age but in many cats these physes do not ossify until two or three years of age.8 This may be due in part to the fact that many cats undergo early spay or castration. While these early spay or castration have a protective effect against the development of mammary gland tumor, uterine disease, and behavioral problem, they lead to a persistence of the growth plate that may predispose young adult cats to fracture. Physeal fractures may affect many growth plates of long bones but the most common fracture sites appear to be the proximal* portion of the femur near the hip joint and the distal* portion of the radius.8 These physeal fractures are repaired using small diameter metal pins placed across the fracture. Long bone* fractures - The scientific reports dedicated to the management of fractures in cats are limited to a small number of case series and, to our knowledge, no clinical trial has compared various repair method for the management of specific long bone fractures. Long bone fractures may be caused by motor vehicle accidents, falls, dog attacks. In the winter, outdoor cats may crawl within car engine compartments to seek the warmth of the engine and may get traumatized by fan belts when the cars are started. In specific urban areas where cats are kept in tall buildings, cats may fall or jump from windows and balconies and may survive these falls. These injuries are named high-rise syndrome. In a series of 119 cats with high-rise syndrome, 46% fractured a long bone. 39% of these fractures affected the forelimbs* and 61% the pelvic limbs*. The tibia was the bone most commonly broken (36%). One third of the patients had thoracic* trauma.9 The surgical methods used to repair long bone fractures in cats include external skeletal fixators. bone plates, interlocking nails, and intramedullary pins. External fixators rely on metal pins anchored in the fractured bones and interconnected using metal or acrylic bars. They are very well tolerated by cats. Joint luxations* are relatively common in cats after trauma. They may result from dog attacks, motor vehicle accidents, fan belt injuries, or falls. The stifle* joint appears the most common joint luxated after trauma but luxations of the tarsus*, hip, and other joint also occur. These luxations often require surgery for repair of the torn ligaments and joint capsule and protection of the joint. We prefer avoiding immobilization after these repairs and we achieve this by placing hinged external fixators. The postoperative management of patients with hinged external fixation frames is greatly facilitated by the motion present at the joint. The frame allows joint motion but protects the primary repair. In the short term, the hinged may be lightened to limit joint motion and the resulting pain. The hinge may be loosened to perform passive range of motion exercises in the short term. Afterwards, the hinge may be kept relatively loose to facilitate limb use. Pin loosening is unlikely because the stress placed at the pin bone interface is likely smaller than the stress placed at the pin bone interface of frame used for fracture stabilization. With these frames, the tissues absorb a lot of the stress placed on the limb during functional activities. Luxations of the temporo-mandibular joints occur in cats and are most often treated under general anesthesia by levering the jaw into back into place. LIMB DEFORMITIES Limb deformities appear less common in cats than in dogs, in part because cats tend not to be affected by dwarfism, with few exceptions that include Munchkin cats, cats with chondrodystrophy*. Rarely, cat have physeal injuries that lead to abnormal limb growth with angulation and length deficits. These deformities, when severe are treated using external fixation or bone plates. REFERENCES
Physical Therapy, A Part Of Every Practice WHY DO PHYSICAL THERAPY? INFLUENCE OF PHYSICAL THERAPY ON ACUTE AND CHRONIC PAIN Acute pain - Physical therapy has proven benefits in the management of acute post-injury or post-surgical pain. These benefits are achieved through a variety of direct and indirect pathways, including pathways compatible with Melzack's gate control theory. Cold is analgesic through its anti-inflammatory effects (vasoconstriction, decrease in edema, inhibition of production and release of inflammatory mediators). Cold has been shown to disrupt the pain / spasm cycle by decreasing muscle spindle activity. Cold decreases nerve conduction velocity in sensory (and motor) nerves. Cold sensations may lead to endogenous opiate release. Heat also has gating effects on pain sensation transmission in the spinal cord. Indirectly, it may lead to a decrease in muscle spasm through vasodilation. Passive range of motion and stretching have analgesic benefits through release of muscle spasm and other mechanisms. Therapeutic ultrasound, transcutaneous electrical nerve stimulation, and neuromuscular electrical stimulation have proven analgesic benefits in acute and chronic situations through gating mechanisms, endorphine release, and other mechanisms. Chronic pain - Strengthening exercises have proven benefits in patients. For example, patients with osteoarthritis (OA) benefit from isotonic exercises. In these patients, both pain and function are improved after exercise programs. Aquatic exercises are associated with less pain sensations than land-based exercises but lead to functional improvements similar to land-based exercises. In human OA patients, concentric or eccentric exercises performed at low or high intensity are beneficial with regards to pain. Massage has direct (through the gate or counter-irritant mechanisms or psychological pathways) and indirect (through increased muscle extensibility, increased scar tissue extensibility, and increased blood flow) short-term benefits with regards to pain. INFLUENCE OF PHYSICAL THERAPY ON BONE In humans, physiotherapy (PT) has a definite positive influence on the recovery rate after surgical treatment of fractures and chronic bone and joint diseases. The specific benefits of PT (i.e., exercises, manipulation, or physical agents) on bone metabolism are harder to quantify. PT may influence the bone in several ways: 1.) It may help maintain bone composition and density in patients at risk of osteoporosis or osteopenia, 2.) It may promote fracture healing, and 3.) It may promote bone regeneration during bone lengthening procedures. Bone metabolism - The effect of physical exercise on bone composition has been evaluated in postmenopausal women. Ballard evaluated 50 women and found that high physical activity significantly increased the bone mineral composition compared to low physical activity (0.834 g/cm versus 0.721 g/cm, p<0.01). Estrogen therapy also had a positive influence on bone mineral composition in these women (0.907 g/cm with therapy versus 0.809 g/cm without therapy, p < 0.027). Surprisingly, another study involving 2025 peri- and postmenopausal women documented higher bone mineral density in the women who had performed recreational and competitive sporting activities as adolescents than in the women that did not perform such activities as adolescents. Once adjusted for age, weight, time from menopause to densitometry, and duration of estrogen replacement therapy, the bone mineral density was 1.4% higher (p = 0.015) in the women who exercised during their adolescence. This shows that physical activities have a very long-term positive influence on bone metabolism. Manipulation has also been shown to influence bone metabolism. Wilson evaluated whether manipulation techniques generate potentially osteogenic levels of strain within mammalian bone. In that study, manual levered bending created levels of compressive strain similar in magnitude to those created by mechanical devices used in previous animal experiments to induce new bone formation (osteogenesis). When the influence of physical agents on bone is considered, most of the scientific work has focused on the influence of electrical currents on bone metabolism and fracture healing. Bone formation was induced in rabbits by placing a cathode within the medullary canal of bone with an anode encircling the femoral shaft and applying a direct current of 20 µA during six weeks. When direct currents ranging from 0.02 to 0.2 µA/mm2 were applied for 21 days in rabbits, bone production was increased by approximately 50%. Platinum appears to be the most stimulatory metal compared to cobalt-chrome, silver, stainless steel, and titanium. Bone ingrowth into porous implants is also enhanced by the application of electrical stimulation. Colella reported that interfacial shear strength between porous titanium implants and cortical bone was consistently greater in dogs treated with electrical stimulation compared to control dogs. Electrical stimulation may also affect the cellular behavior of growth plates. In a three-week-long, in-vivo study of the effect of direct-current stimulation (8 µA) on the distal femoral growth plate of young rabbits, characteristic thickening of the growth plate caused by the accumulation of hypertrophic cells was found in the group stimulated for two weeks. Electricity also may have a protective effect on osteoporosis. In a report evaluating the influence of pulsed electromagnetic fields on the progression of osteoporosis in the ulna of turkeys (one hour per day of pulsed electromagnetic fields), an osteogenic dose-response to induced electrical power was observed, with a maximum osteogenic effect between 0.01 and 0.04 tesla per second. Another study in turkey confirmed these findings and found optimal osteogenesis with a 15 Hz sinusoidal electric field. The effects of electrical muscle stimulation on bone density have been evaluated in patients with spinal cord injury. Electrical muscle stimulation does not seem to have a positive effect in the short term and appear to have a positive effect, albeit minor, when used over longer periods of time. In a short-term study, electrical muscle stimulation did not influence bone mineral content or bone density. During a 32-week-long exercise period four paraplegic men volunteered for an exercise program in which their paralyzed quadriceps muscles were stimulated by means of computer-regulated electrical impulses applied through external electrodes. Another six-month study evaluating the effects of functional electrical stimulation cycle ergometry on bone mineral density was investigated in six quadriplegic men, failed to show changes in femoral bone mineral density. A longer-term study found that an electrical stimulation exercise program used on the lower limb of 37 patients with spinal cord injury significantly decreased bone loss over time (0.2 and 3.3% reduction in loss per year, p < 0.05). Fracture healing - Early and continued mobilization (manipulation, exercises) has profound beneficial effects on all the healing process of all musculoskeletal tissues. Also, prolonged rest or immobilization may delay recovery or adversely effect tissues. Buckwalter recently reviewed the effects of early motion on healing of musculoskeletal tissues. He wrote: "Experimental studies, of the past several decades confirm and help explain the deleterious effects of prolonged rest and the beneficial effects of activity on the musculoskeletal tissues. They have shown that maintenance of structure and composition of normal bone, tendon and ligament, articular cartilage and muscle, requires repetitive use and that changes in the patterns of tissue loading can strengthen or weaken normal tissues. Although all the musculoskeletal tissues can respond to repetitive loading, they vary in the magnitude and type of response to specific patterns of activity. Furthermore, their responsiveness may decline with increasing age. Skeletal muscle and bone demonstrate the most apparent response to changes in activity in individuals of any age. Cartilage and dense fibrous tissues also can respond to loading, but the responses are more difficult to measure. The effects of loading on healing tissues have been studied less extensively but the available evidence indicates that repair and remodeling tissues respond to loading and that, like immature normal tissues, repair tissues may be more sensitive to cyclic loading and motion than mature normal tissues. Early motion and loading of injured tissues is not without risks, however. Excessive or premature loading and motion of repair tissue can inhibit or stop healing. Unfortunately, the optimal methods for facilitating healing by early application of loading and motion have not been defined. Nonetheless, experimental studies and newer clinical investigations document the benefits of early controlled loading and motion in the treatment of musculoskeletal injuries, and show that optimal restoration of musculoskeletal function following injury or surgery requires early controlled activity". Bone fragment motion influences fracture healing. While axial micromotion stimulates bone healing, shear is detrimental to fracture healing. Circular external fixators help ensure the absence of shear while allowing axial micromotion. This may be the most significant factor responsible for the enhanced fracture healing associated with circular external fixation used to treat long bone fracture in dogs compared to plate or conventional external fixation. Electrical stimulation with direct current has wide applications in the stimulation of fracture healing, especially in the treatment of non-unions and delayed unions. The electrodes may be implanted in the bone or, more recently, have been placed on the surface of the skin. Electrically stimulated titanium cathodes (current density: 0.33 µA/mm2) enhanced bone formation in a model of canine delayed union. In a ten-year review of patients treated with implanted electrodes, all fractures had remained united and normal bone remodeling had occurred. This ten-year review supported the long-term safety and effectiveness of this technique in treating nonuniting fractures. Non-invasive methods (steel plates placed on the skin across the fracture site) have shown excellent results in the treatment of non-unions in man. Scott evaluated 21 patients with non-unions, six of ten treated with electrical capacitive coupling healed; none of the patients left untreated healed (p=0.004). Abeed reported on the use of 40-mm-diameter stainless steel plates providing capacitively coupled electrical stimulation (63 kHz, 6V peak-to-peak sine wave) for up to 30 weeks in 16 patients. He found that a distance of 80 mm or less between the electrodes resulted in healing in all cases. He also found that healing was not affected significantly by any of the following factors: whether or not the non-union had been treated surgically prior to stimulation, whether or not it had been infected, whether or not the patient bore weight after treatment, or by the presence or absence of metal at the fracture site from previous surgery. He concluded that the dependence of healing on the interplate distance suggests that maintaining sufficient current across the plates is necessary to allow healing, which for larger bones may be achieved by increasing the area of the plates, the applied voltage, or the excitation frequency of the stimulation signal. Limb lengthening - Physical therapy is an important component of the success of limb lengthening. Coglianese wrote that limb lengthening by distraction osteogenesis and external fixation is used increasingly in the United States for a variety of orthopedic conditions. Maintenance of joint motion critical for successful outcomes can be difficult to achieve. In a clinical review of limb lengthening, Greene wrote that the patient must be encouraged to bear weight on the lengthening limb, lest the newly formed bone fail to mature and corticalize properly. Practical recommendations - Clinically we know that limb use is important after limb trauma and fracture repair. Disuse osteoporosis will result from prolonged immobilization or absence of weight bearing. In fact, limb immobilization alone has been shown to have detrimental effects in experimental dogs including loss of bone size and weight, and contracture of the quadriceps femoris muscle. Although the causes of osteoporosis are not well known, a lack of muscular activity, increased blood supply, and a decrease in piezoelectric action of bone crystals on bone cells from the absence of weight bearing are considered to be important factors. INFLUENCE OF PHYSICAL THERAPY ON JOINTS Articular cartilage - Immobilization is detrimental to joint health. Cartilage nutrition is promoted by the displacement of synovial fluid that occurs during joint motion. Joint motion and weight bearing promote the diffusion of nutrients into articular cartilage. Also, synovial fluid production is reduced with joint immobilization. Partial immobilization (i.e., casting) is less detrimental than complete immobilization (i.e., external skeletal fixation). With joint immobilization, the cartilage becomes softer (42% softer in an 11-week-long canine study) and thinner (9% in the same study). Joint immobilization in flexion is less detrimental than joint immobilization in extension. While immobilization in extension lead to changes resembling degenerative joint disease, immobilization in flexion leads to the atrophy of articular cartilage without degenerative joint disease. Remobilization after immobilization will lead to cartilage regeneration. This restoration appears more complete after immobilization in flexion than after immobilization in extension. The recovery of cartilage after immobilization may never be complete. In a canine study including 11 weeks of immobilization and 50 weeks of remobilization, the biomechanical properties of the articular cartilage at the end of study remained 15% below control level (p=0.05). Intense exercise during that period will prevent restoration of normal cartilage thickness and proteoglycan concentration. It is therefore important to increase exercise a moderately and progressively after joint immobilization. Cartilage regeneration after immobilization may be improved by the intra-articular administration of hyaluronic acid. In a study of cartilage regeneration after 4 weeks of immobilization of the stifle joints in dogs, remobilization combined with hyaluronic acid (HA) therapy improved histochemical staining and reduced structural damage to articular cartilage when compared with remobilization alone. It is important to note that immobilization may protect cartilage during the period immediately following an injury. After chemically induced cartilage injuries in guinea pigs, immobilization in the short term (for 3 weeks) had definite protective effects on the cartilage. Joint motion - Postoperative immobilization in a plaster cast for six weeks and early mobilization in an ankle brace one to two weeks were compared in a prospective, randomized study of patients undergoing surgery and internal fixation to repair ankle fractures. Ten weeks after surgery, muscle torque and range of motion were less impaired in the early mobilization group. Also, 12 months after surgery, range of motion in flexion was increased in the early mobilization group compared to the plaster cast group. Another prospective, randomized study evaluated early mobilization of distal radial fractures and confirmed an increase in grip strength and joint range of motion in the group with early mobilization compared to the group with a short arm cast. WHO BENEFITS FROM PHYSICAL THERAPY? Some patients are at high risk of complications after an injury or a disease. In orthopedics, for example, some patients appear particularly predisposed to complications after surgery because they cannot walk on their own or may have irreversible complications if their problems are not treated immediately and aggressively. Patients with neurologic problems who are unable to walk also need intensive rehabilitation. In these high-risk patients, the rehabilitation plan should not merely be a suggestion. Rather, it must be an imperative part of the postoperative management of the patient. The classic complications of fracture repair include a delay or absence of bone healing (delayed or non-union) potentially associated with failure of fixation and the contracture of muscles adjacent to the fracture site. Other complications include infection, or vascular and neurologic injuries. After arthrotomies, complications include peri-articular fibrosis and infection. Fracture complications generally do not come alone. When something goes wrong in the biological or mechanical aspects of the fracture healing process, other things generally fail as a consequence. For example, when the blood supply of a fractured bone is inadequate (i.e., with gunshot wounds or radial fractures in small breeds), the healing process will be delayed. This delay will increase the stress placed on the metal implants and the metal - bone interface over time. This will in turn lead to the failure of the metal implant or metal bone interface. This will increase bone movement at the fracture site, further damaging the blood supply in that region. SKELETALLY IMMATURE DOGS Puppies are at higher risk of complications because of the increased inflammatory response present after tissue injury. As a consequence, fibrosis around joints is more likely after articular fracture repair and fibrosis of muscles is more likely after long bone fracture repair. Puppies are also at increased risk because of the nature of their injuries (articular or physeal fractures), their relative lack of compliance, and their increased sensitivity to osteopenia in limbs that do not bear weight for extended periods of time, compared to adult dogs. Also, laxity (i.e., carpal hyperextension) after immobilization appears more likely and more severe in puppies than in adult dogs. In summary, puppies are more sensitive to loss of range of motion after injuries secondary to extensive peri-articular fibrosis or muscle contractures. They are also more likely to be negatively impacted by limb immobilization, showing signs of osteopenia and joint laxity. It is therefore critical to design a thorough rehabilitation protocol in injured puppies aimed at maintaining range of motion and limb use. Rehabilitation is more challenging in puppies than in adult dogs because of their intrinsic higher activity level. Hyperactive puppies may be fed or sedated to calm them down. The duration of their immobilization should be kept to a minimum because they tend to lose patience sooner than adult dogs. Cold pack, massage, and passive range of motion should start immediately after surgery. Low-impact play exercise may be used to promote limb use during the activity period. Complications should be identified early and should be treated aggressively. Rehabilitation options may focus on massage, cold and heat therapy, range of motion exercises, assisted walking, treadmill exercises and controlled playing exercises. SEVERE TRAUMA The tissue trauma present after motor vehicle accidents, bite wounds (crushing injures), or gunshot wounds may be extremely severe. Dogs with fractures affecting two or more limbs are in this category. It is important to survey the full extent of orthopedic injuries and tissue trauma in order to design the rehabilitation plan. In these dogs, fractures are often associated with severe muscle contusion, skin abrasions, and, potentially, with joint instability. Infection of the bone or traumatized tissues may also be present. Providing excellent nursing care is an important part of patient management. Dogs should be turned regularly to avoid dependent edema. Prior to surgical treatment of the fractures, severely traumatized dogs benefit from massage (effleurage), gentle range of motion of all limbs, and assisted standing. After stabilization, the rehabilitation may include massage, cold therapy (if the blood supply to the affected regions is not impaired), range of motion, assisted standing, and, later, assisted walking. FEMORAL HEAD OSTECTOMY In some dogs with hip dysplasia, the pain caused by the abnormal contact between the femoral head and the acetabulum cannot be controlled and the femoral head (and neck) is removed. This surgery is named femoral head ostectomy (FHO). FHO is also performed after traumatic luxation of the hip joint (when significant cartilage damage or a femoral head fracture are present), after non-reconstructible acetabular fractures, or when Perthes disease is present. Pain in that region is expected to subside once the contact between the femoral head and the acetabulum is eliminated. The mechanics of the hip joint after the FHO is abnormal and most dogs will need time to adapt to this new situation. Additional problems are generally present in dogs with FHO. Dogs with chronic hip dysplasia or Perthes disease generally have muscle atrophy before the FHO. Dogs with acetabular fractures, femoral head fractures, or hip dislocations have pre-existing tissue trauma. The combination of the FHO and muscle atrophy or tissue trauma complicates the rehabilitation of dogs after FHO. It is most important to maintain or enhance muscle mass after surgery. Rehabilitation options may include electrical stimulation, dancing, treadmill walk, swimming, jogging, stair climbing, and controlled ball playing. TRAUMATIC JOINT LUXATIONS (DISLOCATIONS) Traumatic joint luxation may be treated by closed reduction or open reduction. Most luxations are associated with tears in the joint capsule and collateral ligaments. Most elbow luxations and some hip luxations are treated in a closed fashion. The luxations of others joints are most often treated in an open fashion. Immobilization is generally recommended after closed reduction to avoid re-luxation of the joint. Immobilization in also recommended after open reduction to protect the healing tissues. The combination of joint trauma and immobilization predisposes dogs to peri-articular fibrosis and muscle atrophy. The rehabilitation of these dogs should focus on maintaining joint range of motion, while avoiding stress on the healing joint capsule and collateral ligaments. The rehabilitation may emphasize massage (to eliminate peri-articular edema), cold therapy in the early postoperative period, heat therapy, and range of motion exercises. UNFIT DOGS Unfit dogs dog may include obese dogs, giant dog breeds, older dogs, dogs with degenerative joint disease in multiple limbs, and dog with chronic systemic diseases such as hyperadrenocorticism, diabetes, or hypothyroidism. Unfit dogs generally have a poorly developed muscle mass. After trauma or after surgery, the rehabilitation of unfit dogs may be particularly challenging because the cause of their lack of fitness can rarely be eliminated. Rehabilitation options include assisted standing, range of motion exercises, underwater treadmill, and assisted walking. NEUROLOGICAL AND NEUROSURGICAL PATIENTS Non-ambulatory neurological and neurosurgical patients need specialized nursing and rehabilitation care. For patients without motor function in affected limbs, that rehabilitation care includes the maintenance of joint motion and muscle mass. Joint motion is generally maintained through massage and passive range of motion exercises. Muscle mass appears to respond positively to the use neuromuscular electrical stimulation (NMES), even though NMES cannot fully protect against the long-term effects of denervation. Patients with motor function in their affected limbs who are unable to walk without support are ideal candidates for assisted-walking in carts or underwater treadmills. They can also be treated in whirlpools and, depending on their size and personality, they can be walked using slings. THE LOGISTICS OF PHYSICAL THERAPY(1) Human resources Clinicians and their support staff are the primary resource necessary to provide care in physical rehabilitation. Initially, the clinician has to assess the patient thoroughly to develop an objective opinion of the extent of his/her orthopedic or neurologic physical limitations, the severity and chronicity of these limitations, and the presence of complicating factors including obesity, cardiovascular problems, chronic wasting diseases, or lack of physical fitness. That initial evaluation is the key to development of the initial rehabilitation program. As such, the initial assessment of the patient must be accurate: it must be sensitive (i.e., all problems should be detected) and must be specific (i.e., all detected problems should be accurately judged). Also, this accurate assessment should be placed in proper perspective: the likelihood of success of therapy should be known, based on the scientific literature and the clinician's clinical experience and that information should be fairly presented to the owner. Making this objective assessment and discussing it objectively with the owner requires a solid scientific and clinical knowledge in orthopedics, in neurology, and in rehabilitation. This knowledge may come from a single clinician, a veterinarian trained in physical rehabilitation, or may come from a team that includes a veterinarian and a physical therapist. The rehabilitation care is often done by technical support staff with the help of the clinicians overseeing the medical care of the patient. The person delivering the rehabilitation care must: 1.) observe the patient carefully during therapy, 2.) slightly adapt the treatment based of the specific needs of the patient, 3.) clearly describe to clinicians the patient's progress during rehabilitation, 4.) provide an objective progress report to the owner. The physical limitations of the patient (i.e., ability to ambulate, likelihood of joint luxation or mechanical failures of fracture fixation) should be understood by the owners and by all people providing rehabilitation and nursing care. Physical environment The rehabilitation environment should be quiet and comfortable to minimize the patient's stress. The number of steps within and around the rehabilitation space and the presence of slippery floors should be minimized. This may be accomplished through the use of non-skid flooring surface (i.e., rubber surface, epoxy coating of concrete floor) and through the use of non-skid ramps. Access to rehabilitation equipment should be ergonomic, avoiding the need to lift heavy patients. Patient transportation for large non-ambulatory dogs should be available using low moving tables or lifts, carts, hoists, or a ceiling rail system. Bedding should be adapted to the patient's needs. Patients with limited mobility should rest on surfaces that minimize the likelihood of decubitus ulcers. These surfaces may include foam mats with impervious surfaces, mesh beds, or water beds. Urinary incontinent dogs should be kept on porous or absorbing surfaces that will decrease the likelihood of urine scalding. Dogs with mechanically weak surgical repair at risk of joint luxation or mechanical failure should be kept in a space that decreases the likelihood of stumbling or falling. A reasonably large amount of space is needed in rehabilitation to perform therapeutic exercises (Table 1) Table 1- Potential space requirements in companion animal physical rehabilitation
Equipment Specialized equipment is used in rehabilitation. This equipment include machines used to keep cold and hot packs at therapeutic temperatures, machines delivering therapeutic ultrasound, neuromuscular electrical stimulation, transcutaneous electrical nerve stimulation, land treadmills, underwater treadmills, swim tanks, balance boards, trampoline, low (7.5 cm / 3") and high (15 cm / 6") steps (Table 2). Other modalities are emerging in animal rehabilitation, including low level laser therapy and extracorporeal shockwave therapy. Table 2- Potential equipment used in companion animal physical rehabilitation
Abbreviations: ortho, orthopedic; OA, osteoarthritis; neuro; neurologic Supplies Cold is delivered to tissues in the early postoperative period and beyond. Most often, cold is delivered through conduction, where a heat absorber contacts the skin. Cold packs may be made with a mixture of water (2 volumes) and isopropyl alcohol (1 volume) in a Zip-lock® bag who form a slushy mixture once refrigerated in a conventional freezer. Cold packs are commercially available in a variety of size, shape, inner and outer material. Cold can also by applied by convection, by blowing air over the skin, or by evaporation of a volatile agent, such as ethyl chloride (ethyl chloride sprays). Heat packs are used to elevate tissue temperature. Commercial hot pack may be purchased and are maintained at 165°F in a hydrocollator. Microwaveable hot packs are also commercially available in a variety of size and shape. Some of these may have a temperature marker indicating optimal therapeutic temperatures. Supplies are needed for ambulatory assistance. Splints are used to support and protect limbs, to prevent contracture or self-mutilation. Belly slings are used to help dogs with weak pelvic limbs. Other slings and harnesses are used to support the pelvic or forelimbs of patients with orthopedic or neurologic problems. Ambulation carts are useful in dogs with limited mobility (see related presentation in this book). Spherical and peanut-shaped balls are also used to support weakly ambulatory and non-ambulatory patients during treatment or during some daily activities. These balls are available in a variety of sizes that can be used in medium, large, and giant dog breeds. Supplies are also needed to perform therapeutic exercises. Rubber exercise bands may be used to influence the motion of joint. These bands are available in a wide variety of thicknesses. Canine personal floatation devices (life-vests) are commercially available and are often used in aquatic activity. They are particularly important in dogs with impaired locomotion such as neurologic and obese patients. Supplies are needed to wrap or splint weak or injured limbs during or after rehabilitation sessions. These supplies include contact material (i.e. gauze, Vaseline-impregnated gauze, gel dressing), cast padding, rolled gauze, self-adhesive elastic tape, and a variety of splinting material (i.e., aluminum, fiberglass, thermoplastic). REFERENCE Marcellin-Little DJ, Danoff K, Taylor R, Adamson C. Logistics of companion animal rehabilitation. Vet Clin North Am Small Anim Pract. 2005 Nov;35(6):1473-84 Additional references available upon request: denis_marcellin@ncsu.edu | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
