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The objective of this study was to compare longitudinal results from two models of combined anterior cruciate ligament (ACL) and meniscal injury. A modified ACL transection (mACLT) model and a traumatic impact (ACLF) model were used to create an ACL rupture and acute meniscal damage in a Flemish Giant animal model. The animals were euthanized at time points of 4, 8, or 12 weeks. The menisci were assessed for equilibrium and instantaneous compressive modulus, as well as glycosaminoglycan (GAG) coverage. The articular cartilage was mechanically assessed for thickness, matrix modulus, fiber modulus, and permeability. Articular cartilage GAG coverage, fissuring, tidemark integrity, and subchondral bone thickness were measured. Both models resulted in damage indicative of osteoarthritis, including decreased meniscal mechanics and GAG coverage, increased permeability and fissuring of articular cartilage, and decreased GAG coverage. The mACLT model had an early and lasting effect on the menisci mechanics and GAG coverage, while cartilage damage was not significantly affected until 12 weeks. The ACLF model resulted in an earlier change of articular cartilage GAG coverage and fissuring in both the 8 and 12 week groups. The menisci were only significantly affected at the 12 week time point in the ACLF model. We concluded the progression of post traumatic osteoarthritis was dependent on injury modality: a point to be considered in future investigations. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:486-495, 2017.

Subchondral bone is thought to play a significant role in the initiation and progression of the post-traumatic osteoarthritis. The goal of this study was to document changes in tibial and femoral subchondral bone that occur as a result of two lapine models of anterior cruciate ligament injury, a modified ACL transection model and a closed-joint traumatic compressive impact model. Twelve weeks post-injury bones were scanned via micro-computed tomography. The subchondral bone of injured limbs from both models showed decreases in bone volume and bone mineral density. Surgical transection animals showed significant bone changes primarily in the medial hemijoint of femurs and tibias, while significant changes were noted in both the medial and lateral hemijoints of both bones for traumatic impact animals. It is believed that subchondral bone changes in the medial hemijoint were likely caused by compromised soft tissue structures seen in both models. Subchondral bone changes in the lateral hemijoint of traumatic impact animals are thought to be due to transmission of the compressive impact force through the joint. The joint-wide bone changes shown in the traumatic impact model were similar to clinical findings from studies investigating the progression of osteoarthritis in humans. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1835–1845, 2015.

SummaryObjective: The objective of this study was to describe the clinical and radiographic features, as well as the treatment and outcome of minimally displaced tibial-tuberosity-avulsion-fractures (MDTTAF).Materials and methods: Signalment, history, diagnostics, therapy, and outcome were recorded. Follow-up was documented as re-examination, radiographic assessment or telephone conversation.Results: Nine large breed dogs that were presented with lameness originating from the proximal tibia were included. All showed signs of pain when pressure was applied to the tibial tuberosity. There was no stifle instability or intra-articular disease. The main feature on mediolateral radiographs was a widened tibial-tuberosity-physis with reactive new bone and loss of edge definition of the epiphyseal and metaphyseal margins. Non-surgical treatment was chosen in eight dogs, and surgery in one dog. Radiographic follow-up showed progressive closure of the tibial-tuberosity-physis and healing. Clinical signs resolved at a median of 28 days (range: 14–120).Discussion: Minimally displaced tibial-tuberosity-avulsion-fractures should be a differential diagnosis in skeletally immature large breed dogs older than nine months of age with signs of subtle pelvic-limb lameness, and signs of proximal tibial pain, but no evidence of stifle joint disease. Thorough clinical examination and critical review of bilateral radiographs are important to diagnose MDTTAF. The outcome in these cases suggests that the prognosis for MDTTAF is excellent. Age and size of the affected dogs in this study differ from an earlier publication that illustrated more severely displaced tibial tuberosity avulsion fractures, occurring mainly in terriers around five months of age.

SummaryObjective: To compare the mechanical properties of pancarpal arthrodesis (PCA) constructs stabilized at 20° of extension using either a 3.5 mm limited contact dynamic compression plate (LC-DCP) or a 3.5/2.7 mm hybrid plate (HP).Methods: Seven forelimb pairs were used from dogs of similar size. All soft tissues were removed except for supporting structures of the carpus and proximal metacarpal region. All plates were accurately bent to 20°, and then instrumented with two, 350Ω strain gauges applied at the level of the bend. Constructs were embedded in epoxy moulds then mounted onto a servo-hydraulic testing machine. Specimens were loaded for 10 cycles at 100N, 200N and 300N. Tenth cycle construct compliance (CC), maximum angular deformation (MAD), and peak plate strain (PPS) were compared using two-factor analysis of variance (ANOVA) and Student-Newman- Keuls post-hoc tests (p Results: Regardless of load, CC was 29% to 33% smaller in the HP than the LC-DCP group (p Clinical significance: The mechanical advantages of the HP over the LC-DCP make it a viable alternative for PCA. Smaller CC, MAD and PSS of the HP may reduce the risk of implant failure and postoperative morbidity following PCA.

SummaryOsgood-Schlatter disease (OSD) is a condition affecting human adolescents in which there is partial separation of bone fragments from the tibial tuberosity at the site of insertion of the patellar ligament to the tibial tuberosity. Tensile trauma seems to be the most likely aetiology. Clinical signs in people consist of swelling and pain at the proximal part of the tibial tuberosity and around the distal end of patellar ligament. Radiographs frequently show small ossicles at the patellar ligament insertion. Conservative treatment is usually curative. The term OSD has also been used for the canine patient. However, radiographs of these patients typically show an enlarged radio-lucent line at the apophyseal plate of the tibial tuberosity. This finding is consistent with a mild avulsion fracture of the canine tibial tuberosity. Based on the radiographic differences between the two species, it seems more appropriate to use the term OSD only for people. The purpose of this paper is to review the literature on OSD in people and the reports of injuries to the proximal tibial tuberosity in dogs. In addition, a new classification system for tibial tuberosity avulsion injuries in the immature dog is proposed, with an algorithm for management of this injury.

Post-traumatic osteoarthritis (PTOA) develops as a result of traumatic loading that causes tears of the soft tissues in the knee. A modified transection model, where the anterior cruciate ligament (ACL) and both menisci were transected, was used on skeletally mature Flemish Giant rabbits. Gross morphological assessments, elastic moduli, and glycosaminoglycan (GAG) coverage of the menisci were determined to quantify the amount of tissue damage 12 weeks post injury. This study is one of the first to monitor meniscal changes after inducing combined meniscal and ACL transections. A decrease in elastic moduli as well as a decrease in GAG coverage was seen.

The central third of the patellar tendon is commonly used to reconstruct the injured anterior cruciate ligament. Some studies have noted changes in joint tissues following this procedure. It has been postulated that these changes may be associated with increased stress on the remaining tendon following harvest of the graft. In our study, the central third of the patellar tendon was excised in three groups of rabbits. The central tendon defects in two of the three groups were fitted with different augmentation devices to augment the host tendon during the healing process. All rabbits followed a daily treadmill exercise regimen for 12 weeks following the operation. Biomechanical testing of the tendon revealed that in nonaugmented tendons the cross-sectional area and the length of the patellar tendon significantly increased 112 and 16%, respectively. There was histological evidence of host-tendon remodeling throughout the cross section and extensive fibrosis in the infrapatellar fat pad. Augmentation of the tendon significantly reduced these changes, with the least change noted in the group with the greatest augmentation. The rabbits with augmentation devices retained tendon dimensions similar to those of the contralateral intact tendon, and tendon remodeling occurred only in the defect area. The rabbits with augmentation devices exhibited little to no fibrosis of the fat pad. Structural properties of augmented and nonaugmented tendons were similar despite the size differences, indicating higher tissue quality in the augmented tendons. This study suggested that complications of the knee joint (i.e., tendon proliferation and fat pad fibrosis) noted after anterior cruciate-ligament reconstruction with the autogenous patellar tendon may be limited by the implantation of an augmentation device.

SummaryA five-month-old male, German Shorthaired Pointer dog was presented for severe, bilateral, thoracic-limb-lameness, with elbow swelling, pain, and crepitus. Radiography and computed tomography confirmed bilateral incomplete ossification of the humeral condyles (IOHC), with a non-displaced incomplete fracture of the left medial epicondylar crest and condylar deformity, characterised by enlargement of the trochleas with extension of the disto-medial aspect of the bone below the normal elbow joint level, and a deformed proximo-medial aspect of the ulna and radius. Transcondylar lag screws were placed bilaterally in an attempt to prevent fracture. Microscopic examination of biopsies, harvested from both humeral condyles, was supportive of IOHC. Six years after surgery, radiographs showed severe osteoarthritis and it appeared that fusion of the humeral condyles had not occurred. The dog followed an active life style until 10 years after surgery when the elbows showed almost no observable range-of-motion. However, discomfort was evident only after heavy exercise. Incomplete ossification of the humeral condyles may be associated with osteoarthritis, risk for non-union, implant failure, or secondary condylar fracture. This dog maintained good limb function despite these concerns, and despite bilateral humeral condylar deformity as well as development of severe osteoarthritis. This is the first report of a German Shorthaired Pointer dog with IOHC and the first histological description supportive of this condition in a five-month-old dog.

Objective— To evaluate the effect of limb positioning and measurement technique on the magnitude of the radiographically determined tibial plateau angle (R-TPA). Study Design— In vitro study, R-TPA was determined by 6 blinded observers and image measurement software. Animals— Five canine cadaver hind limbs. Methods— The legs were positioned on a custom-made positioning device simulating a radiographic tabletop technique in lateral recumbency. True lateral positioning was defined by superimposition of femoral and tibial condyles on the radiographic projection. Radiographs were taken while the specimens were relocated in a proximal, distal, caudal, and cranial direction with respect to the radiographic beam. For each specimen, 25 different radiographic views were obtained and 6 blinded observers determined the radiographic TPA using 2 different methods. The conventional method used precise anatomic landmarks to determine the tibial plateau. To simulate osteoarthritic changes complicating identification of these landmarks, the tangential method estimated the tibial plateau as the tangent to the central portion of the tibial plateau. After periarticular soft tissue dissection the anatomic tibial plateau angle (A-TPA) was determined. The A-TPA and the R-TPA were compared. Results— The R-TPA significantly decreased as limb position with respect to the X-ray beam changed from cranial proximal to caudal distal. The maximal mean radiographic R-TPA difference was 3.6° with the first and 5.7° with the second method. Regardless of the method used there was no significant difference between A-TPA and R-TPA in the true lateral position. In the peripheral positions, however, significant differences between anatomic and radiographic TPA were seen. Conclusions— Limb positioning influenced the radiographic appearance of the tibial plateau and the magnitude of the measured TPA. Cranial and proximal positioning of the limb relative to the X-ray beam leads to overestimation whereas caudal and distal positioning leads to underestimation of the TPA. Clinical Relevance— True lateral positioning of the tibia defined by superimposition of the femoral and tibial condyles should be used for accurate TPA determination before tibial plateau leveling osteotomy.

To determine whether use of hemoglobin glutamer-200 (bovine) as a partial blood volume replacement in dogs undergoing cemented total hip replacement caused any deleterious effects on the bone-cement or cement-prosthesis interface, exerted any deleterious effects on body organs, or caused any complications during the anesthetic, immediate recovery, or long-term recovery period.9 adult dogs.Dogs were anesthetized, and 15% of the blood volume was removed. Simultaneously, lactated Ringer's solution was infused, and 6 dogs were given hemoglobin glutamer (1 g/kg of body weight, IV). Unilateral total hip replacement was performed. Limb use was assessed visually, and force-plate and radiographic evaluations were performed before, and 8 weeks after, surgery. Eight weeks after surgery, dogs were euthanatized, necropsies were performed, and prosthetic component pullout forces were determined.There were no significant differences between treated and control dogs in regard to biomechanical (visual assessment of gait, force-plate analysis, femoral and acetabular component pullout forces) and pathologic evaluations (physical examination, CBC, serum biochemical analyses, necropsy, and histologic evaluations). Radiographic signs of loosening of the femoral component were seen in 4 dogs treated with hemoglobin glutamer.Administration of hemoglobin glutamer as a blood substitute did not appear to have any deleterious effects in dogs undergoing total hip arthroplasty. The radiographic findings, which were discordant with the biomechanical results, merit further investigation.

Linear external skeletal fixators offer some unique advantages over other fixation systems; they are biomechanically versatile, minimize surgical trauma to the fracture environment, and allow for simple staged disassembly to help promote bone healing. Historically, the use of linear external skeletal fixators has been reported to result in numerous complications, primarily related to the pin-bone interface. External skeletal fixators have experienced a resurgence in the past two decades. Increased knowledge of proper pin insertion techniques and advancements in pin design have greatly enhanced the longevity of the pin-bone interface, resulting in fewer complications. This article reviews some of the potential advantages of linear external skeletal fixators and principles of application to help strengthen the pin-bone interface and minimize complications.

Chronic degeneration of articular cartilage and bone in a rabbit model of post-traumatic osteoarthrosis has been hypothesized to occur due to acute stresses that exceed a threshold for injury. In this study, we impacted the rabbit patellofemoral joint at low and high intensities. High-intensity impacts produced degenerative changes in the joint, such as softening of retropatellar cartilage, as measured by indentation, an increase in histopathology of the cartilage, and an increase in thickness of sub-chondral bone underlying the cartilage. Low-intensity impacts did not cause these progressive changes. These data suggest that low-intensity impacts produced acute tissue stresses below the injury threshold, while high-intensity impacts produced stresses that exceeded the threshold for disease pathogenesis. This study begins to identify “safe” and “unsafe” ranges of acute tissue stress, using the rabbit patella, which may have future utility in the design of injury prevention devices for the human.

To assess the efficacy of etodolac in improving hind limb function in dogs with osteoarthritis of the hip joint.Prospective study.100 client-owned dogs with clinical signs of osteoarthritis of the hip joint.Baseline ground reaction forces and subjective assessment scores were collected twice at a 7- to 10-day interval. After meeting entrance criteria, dogs were randomly assigned to the following 3 treatment groups: control group (0 mg of etodolac), low-dosage group (135 mg of etodolac), or high-dosage group (450 mg of etodolac). Dogs were treated once daily for 8 days, and gait analysis was repeated on day 8.On day 8 of treatment, vertical impulse and vertical peak force values for low- and high-dosage groups were significantly greater than baseline values within each group. On day 8, vertical impulse values from the high-dosage group were significantly greater than values from the low-dosage group. Vertical peak forces for the low- and high-dosage groups were significantly greater at 8 days than that of the control group. Analysis of the effect of evaluation center (site) on treatment outcome did not reveal a significant effect.Etodolac administration for 8 days improved ground reaction forces in dogs with osteoarthritis of the hip joint. Improvement in force transmission was dosage dependent for the primary outcome measurement (vertical impulse). Results of the study indicate that etodolac is well tolerated by dogs, with minimal adverse effects during an 8-day treatment period.

To describe intratrial differences in hind limb symmetry in healthy dogs at the trot, using noninvasive, computer-assisted, three-dimensional kinematic gait analysis.8 clinically normal large-breed adult dogs.Dynamic flexion and extension angles and angular velocities were calculated for the coxofemoral, femorotibial, and tarsal joints of dogs at the trot. Temporal and distance variables were computed. Essential Fourier coefficients were used to determine mean flexion and extension curves for all joints and to compare differences in movement between right and left hind limbs. Variances attributable to limb, dog, and trial were determined.Each joint had a characteristic pattern of flexion and extension movement that was used to compare intratrial symmetry of hind limb gait. Significant differences were not detected in temporal or distance variables between the right and left hind limbs. Significant differences were not noted in essential Fourier coefficients used to characterize coxofemoral, femorotibial, and tarsal joint angles and angular velocities, with the exception of the cosine-0 coefficient for coxofemoral angular velocity. Variation in joint angle and angular velocity measurements were attributable to individual dog and trial. Variation attributable to limb was negligible.Intratrial evaluation of right-left hind limb symmetry, using kinematic gait analysis, indicated objectively that hind limb movement is symmetrical at the trot in healthy large-breed dogs.Documentation of hind limb symmetry at the trot will help provide a basis for direct comparison of both hind limbs in future studies evaluating gait and treatment of dogs with musculoskeletal disease.

To use ground reaction forces and related impulses as an objective measurement of limb function in the comparison of 1 extracapsular and 1 intracapsular surgical technique for repair of cranial cruciate ligament rupture in dogs.18 healthy dogs.All dogs underwent force-plate analysis of gait prior to transection of the left cranial cruciate ligament. The dogs were randomly allotted to 3 groups. The ligamentous instability was corrected, using a modified retinacular imbrication technique (MRIT) in 1 group and an under-and-over technique in another group. No attempt was made to correct the ligamentous instability in a control group. Clinical grading of lameness and force-plate analysis of gait were performed at 4, 8, 12, 16, and 20 weeks after surgery.Peak vertical force and vertical, braking, and propulsion impulses were recorded for each limb at each time. The degree of clinical lameness was graded at each time.Left hind limb peak vertical forces and vertical impulses were significantly decreased at all times after surgery in the control and under-and-over technique group, compared with values before surgery. Dogs of the MRIT group had improved by 20 weeks, with no significant differences between left hind limb peak vertical forces or vertical impulses recorded before surgery and at 20 weeks.Peak vertical forces and vertical impulses in dogs undergoing MRIT repair after experimentally created cranial cruciate ligament rupture are not significantly different when values recorded for the operated limb at 20 weeks after surgery are compared with those recorded prior to surgery.

To use computer-assisted kinematic analysis to describe the walk in healthy dogs and to adapt Fourier transformation for analysis of the data.Evaluation of normal walk in dogs, using kinematic and force plate analysis.15 healthy large-breed dogs.Morphometric data were collected to describe the sample population. Temporal and distance variables were measured to describe the walk. Flexion and extension movements were described for the scapulohumeral, cubital, carpal, coxofemoral, femorotibial, and tarsal joints. Fourier transformation was adapted to facilitate analysis of the joint angle waveforms.Unique and complex patterns of flexion and extension movements were observed for each joint studied. The walk had consistency of movement in the sample population in temporal and distance variables and joint movements. Variances attributable to intra- and interdog differences were similar and 1 to 2 orders of magnitude smaller than the mean Fourier coefficients from which they were calculated for all 6 joints. The number of essential Fourier coefficients required to represent the joint angle waveforms was 3 for the coxofemoral joint, 5 each for the femorotibial, scapulohumeral, cubital, and carpal joints, and 6 for the tarsal joint.Computer-assisted kinematic gait analysis proved to be a reliable and consistent technique for assessment of movement at the walk in dogs, and Fourier transformation was shown to be an effective tool for analysis of the kinematic data.The database derived from the normal sample population in this study can be used as a model of musculoskeletal function at the walk for future comparisons with disease and treatment.

Noninvasive, computer-assisted, three-dimensional kinematic gait analysis was used to describe lameness in a chronic model of cranial cruciate ligament rupture (CCLR) in dogs.Hind limb lameness was evaluated prior to and at 1, 3, and 6 months after transection of the cranial cruciate ligament.Seven clinically normal large dogs.Dynamic flexion and extension angles and angular velocities were calculated for the coxofemoral, femorotibial, and tarsal joints. Distance and temporal variables were determined. Essential Fourier coefficients were used to develop mean flexion extension curves for all joints and to compare changes in movement that developed with CCLR over time.Each joint had a characteristics pattern of flexion and extension movement that changed with CCLR. The femorotibial joint angle was more flexed throughout stance and early swing phase of stride and failed to extend in late stance. Angular velocity of the femorotibial joint was damped throughout stance phase, with extension velocity almost negligible. The coxofemoral and tarsal joint angles, in contrast to the femorotibial joint angle, were extended more during stance phase. These changes were documented as differences noted in the essential Fourier coefficients. Stride length and frequency also varied significantly after CCLR.Cranial cruciate ligament rupture affects movement of the coxofemoral and tarsal joints, as well as the femorotibial joint, in gait. A pattern of joint movement may be discerned in which the coxofemoral and tarsal joints compensate for the dysfunction of the femorotibial joint.Methods were developed that will improve objective evaluation of CCLR and its treatment in dogs.

Bone plates applied to the cranial surfaces of the tibia, the tarsus, and the metatarsus were used in 10 dogs and 1 cat that underwent pantarsal arthrodesis. Lengthening plates were used in 7 dogs, and 2.7- and 3.5-mm dynamic compression plates were used in the remaining dogs and the cat. Radiography was used to determine whether bone plates became loose or broke, and whether the joint fused completely. Bone plates became loose in 5 dogs; mean time between surgery and development of radiographic evidence of plate loosening was 19.4 months. The bone plate used in the cat broke 4 months after surgery. Overall, 9 of 11 animals had evidence of complete bony fusion of the tarsus at the time of the last radiographic evaluation. One dog had incomplete healing of the talocalcaneocentral joint and another dog had incomplete healing of the tarsometatarsal joint.

Limb symmetry was evaluated by measuring ground reaction forces in 2 groups of normal-gaited dogs at a trot. Data were collected from 2 groups of 21 dogs trotted at dog/handler velocities of 1.25 to 1.55 m/s and 1.85 to 2.05 m/s, respectively. Of these dogs, 9 participated in both groups to allow comparison of data at both velocities. Additionally, 16 of the dogs in group 1 were measured in 2 directions of movement to determine whether directional dependence was present. Collected data were then applied to 3 described symmetry indices. Each index was easy to calculate, but all had limitations. A major limitation was variation in magnitude of ground reaction forces measured between the different axes and the effect of this variation on precision of the derived indices. Vertical ground forces provided the most consistent symmetry indices, in part because of their large magnitude. The indices indicated that no dog had perfect right-to-left symmetry during a trotting gait. Statistical differences were not found in any of the measurements of directional dependence. Likewise, comparing symmetry data in dogs trotted at both velocities indicated no significant differences in any axis. However, further analysis of the data revealed the actual amount that a variance attributable to right-left limb variation was negligible. Most of the variance was attributable to trial variation. Thus, the aforementioned indices, which use nonconsecutive footfall methods to evaluate limb symmetry, actually measure principally trial variation and not limb-to-limb variation.

Force plate gait analysis was used to study the effects of subject velocity on ground reaction forces. Seven adult Greyhounds were trotted at 3 distinct velocities: 1.5 to 1.8 m/s, 2.1 to 2.4 m/s, and 2.7 to 3.0 m/s. Forelimb and hind limb peak vertical forces increased with increase in velocity (P0.05). Forelimb and hind limb vertical impulses decreased as velocity increased (P0.05). Significant variations were not observed for craniocaudal or mediolateral peak forces or impulses. It was concluded that velocity significantly (P0.05) influenced ground reaction forces and impulses, and must be controlled in experimental design.

Coefficients of variation were calculated for peak vertical force and for vertical, cranial, and caudal impulses recorded from the left forelimb and left hind limb of 5 dogs that were trotted across a force plate 5 times by 5 handlers. To determine the percentages of variance attributable to dogs, handlers, and trial repetitions, data recorded for each force measurement were analyzed according to a two-factor ANOVA. Coefficients of variation for peak vertical forces and for vertical impulses varied between 5.8 and 8.5%. Coefficients of variation for the forelimb cranial and caudal impulses and for the hind limb cranial and caudal impulses were 26.4 and 30.5%, and 63.0 and 25.9%, respectively. The percentage of the total variance attributable to dogs and to trial repetitions ranged from 14 to 69% and from 29 to 85%, respectively, depending on the force or impulse evaluated. The percentage of variance attributable to handlers varied between 0 and 7%. The trivial amount of variation attributable to handlers indicated that multiple handlers may be used in experiments without an appreciable influence on the results.

A noninvasive computer-assisted kinematic gait analysis was used to describe flexion and extension movements of 6 joints in Greyhounds at a trot. Distinct patterns of movements were described for each joint studied. The coxofemoral and carpal joints were characterized by a single peak of maximal extension. The femorotibial, tarsal, scapulohumeral, and cubital joints had 2 peaks of maximal extension, with 1 peak preceding stance phase and a second peak within stance phase. A two-factor repeated-measures ANOVA was used to determine the variance in measurement of joint angles in degrees that was attributable to trial repetitions and to differences between dogs. The coxofemoral, femorotibial, tarsal, scapulohumeral, and cubital joints had a mean variance attributable to trial repetition of 6.6 (range, 1.7 to 12.9), and a mean variance attributable to differences between dogs of 5.1 (range, 0.9 to 9.2). The carpus had more variance, with a mean variance attributable to trial repetition of 16.3 (range, 13.3 to 20.5), and that attributable to differences between dogs of 31.8 (range, 20.5 to 46.7). Kinematic gait analysis provided a reliable description of flexion and extension movements in Greyhounds with minimal variance attributable to trial repetitions and to differences between dogs.

A 6-month-old Shetland Sheepdog was examined because of a valgus deformity of the left hind limb. Six weeks earlier, the dog had developed a fracture of the distal portion of the right fibula, which was successfully treated by use of external coaptation. Radiography revealed valgus deformity centered at the left distal tibial and fibular physes. Radiographically, the left fibula was 1.5 cm shorter than the left tibia, and the right fibula was 1.3 cm shorter than the right tibia. A distal tibial closing wedge ostectomy was performed to correct the left hind limb angular deformity. The angular deformity was believed to have developed because of abnormal growth of the left distal fibular physis. It is likely, considering the displacement of the right fibular head, that the dog also had premature closure of its right distal fibular physis. The fracture of the right fibula may have prevented development of an angular deformity of the right hind limb.

A 6-month-old female Yorkshire Terrier was examined because of acute left forelimb lameness secondary to a Salter-Harris type IV fracture of the lateral condyle of the humerus. Radiography revealed an eccentric, osteolytic lesion in the distal humeral metaphysis associated with a pathologic fracture. The limb was amputated, and the dog recovered. Microscopic examination revealed an extensive zone of hemorrhage and dilated coalescent spaces, which were filled with blood. Hemosiderin-laden macrophages and multinucleated giant cells were observed throughout the stroma. On the basis of clinical, radiographic, and histologic examinations, a diagnosis of aneurysmal bone cyst was made. Aneurysmal bone cysts generally have been detected in 11- to 13-year-old, medium- to large-sized dogs. They can develop secondary to malignant processes.

Fractures of the femoral capital physis were stabilized with small pins or a lag screw in 36 dogs (4 bilateral injuries). Radiography was used to monitor the development of osteoarthritis in affected joints and narrowing of the femoral neck. More radiographic signs of arthritis (P less than 0.05) developed in the coxofemoral joints of dogs that were less than or equal to 4 months old when injured, compared with those in dogs greater than 4 months old. Of 40 capital physeal injuries, 35% had concurrent ipsilateral coxofemoral joint injuries and developed more radiographic signs of arthritis (P less than 0.05) than did those that had no other coxofemoral injury. Narrowing of the femoral neck developed in 70% of the healing capital physeal repairs, but in most dogs, narrowing was not associated with segmental collapse of the femoral neck. Neither time interval from injury to surgical fixation nor surgical approach used had an effect (P greater than 0.05) on the development of narrowing of the femoral neck.

A method for measuring the surface area of canine articular cartilage was developed. Ten pairs of humeri were harvested from fresh canine cadavers. The articular cartilage of each humeral head was covered with liquid rubber latex applied with a brush to the margins of the articular surface. The latex cast was removed from the cartilage after the latex dried. Radial cuts were made in the cast so it could be flattened into a 2-dimensional plane. The surface area of each cast was then measured, using a compensating polar planimeter.

To define alterations of movement in dogs with hip dysplasia by use of noninvasive, 3-dimensional, computer-assisted kinematic gait analysis.Kinematic and force plate data were collected at the trot from clinically normal dogs and from dogs with hip dysplasia.12 large adult dogs of various breeds with clinical and radiographic evidence of hip dysplasia, and 12 clinically normal adult large dogs of various breeds with body weight similar to that of the dogs with hip dysplasia.Dynamic flexion and extension angles and angular velocities were calculated for the coxofemoral, femorotibial, and tarsal joints. Temporal and distance variables were also computed. Essential Fourier coefficients were determined and used to reconstruct mean dynamic flexion and extension curves for all joints, and to compare differences in movement between dogs with hip dysplasia and clinically normal dogs.Dogs with hip dysplasia had subtle characteristic changes in dynamic flexion and extension angles and angular velocities of each joint, verified by significant differences in essential Fourier coefficients between the 2 study groups. Stride length was increased and peak vertical force was decreased in dogs with hip dysplasia. Subject velocity, maximal foot velocity, stance duration, stride frequency, and impulse area did not differ between the 2 groups.Kinematic gait analysis indicated that hip dysplasia is associated with alterations in movement of the coxofemoral, femorotibial, and tarsal joints. Computer-assisted kinematic gait analysis provided a noninvasive, objective tool with which to evaluate these complex motion alterations.The information obtained may be useful in future evaluations of various modes of treatment for hip dysplasia.