A study of acute and chronic tissue changes in surgical and traumatically-induced experimental models of knee joint injury using magnetic resonance imaging and micro-computed tomography.

OBJECTIVE: The objective of this study was to monitor the progression of joint damage in two animal models of knee joint trauma using two non-invasive, clinically available imaging modalities. METHODS: A 3-T clinical magnet and micro-computed tomography (µCT) was used to document changes immediately following injury (acute) and post-injury (chronic) at time points of 4, 8, or 12 weeks. Joint damage was recorded at dissection and compared to the chronic magnetic resonance imaging (MRI) record. Fifteen Flemish Giant rabbits were subjected to a single tibiofemoral compressive impact (ACLF), and 18 underwent a combination of anterior cruciate ligament (ACL) and meniscal transection (mACLT). RESULTS: All ACLF animals experienced ACL rupture, and 13 also experienced acute meniscal damage. All ACLF and mACLT animals showed meniscal and articular cartilage damages at dissection. Meniscal damage was documented as early as 4 weeks and worsened in 87% of the ACLF animals and 71% of the mACLT animals. Acute cartilage damage also developed further and increased in occurrence with time in both models. A progressive decrease in bone quantity and quality was documented in both models. The MRI data closely aligned with dissection notes suggesting this clinical tool may be a non-invasive method for documenting joint damage in lapine models of knee joint trauma. CONCLUSIONS: The study investigates the acute to chronic progression of meniscal and cartilage damage at various time points, and chronic changes to the underlying bone in two models of posttraumatic osteoarthritis (PTOA), and highlights the dependency of the model on the location, type, and progression of damage over time.

Improving surgical reduction in radial fractures using a 'dowel' pinning technique in miniature and toy breed dogs.

OBJECTIVES: A retrospective approach was used to detail and evaluate a 'dowel' pinning technique in distal radial fractures in miniature and toy breed dogs. METHODS: Medical records and radiographs from 2003-2009 of miniature and toy breed dog radial fractures were examined. Sixty cases were divided into two groups: 51 radial fractures repaired with a 'dowel' pinning and external skeletal fixation (ESF) and nine radial fractures repaired with closed reduction and ESF. Each dog was evaluated and radiographic images were obtained at presentation, postoperatively, and at 1, 2, 4, 8, and 12 weeks postoperatively. Signalment, reduction, alignment, time to clinical bone healing and ESF removal, and implant morbidity were determined for each group. RESULTS: Radial fractures repaired with a 'dowel' pin and ESF had improved reduction compared to closed reduction and ESF alone (p<0.0001 as evaluated with lateral radiographs and p<0.0004 with cranial/caudal radiographs). Both surgical groups resulted in good clinical outcome with low morbidity, however it was observed that the time to clinical union and ESF removal was an average of 2.5 weeks less with closed reduction technique compared to the open reduction and 'dowel' pinning technique (p<0.031). CLINICAL SIGNIFICANCE: Incorporating a 'dowel' pin to the surgical repair enhances the reduction of distal radial fractures in miniature and toy breed dogs and results in excellent clinical outcomes but causes a small delay in bone healing.

Deformity secondary to bilateral incomplete ossification of the humeral condyle in a German Shorthaired Pointer dog. A case report with ten-year follow-up.

A 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.

Does Osgood-Schlatter disease exist in the dog?

Osgood-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 radiolucent 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.

Patellar tendon augmentation after removal of its central third limits joints tissue changes.

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.

Changes in the mechanical properties of patellar tendon preparations of spontaneously diabetic dogs under long-term insulin therapy.

Diabetes mellitus is known to involve a wide range of musculoskeletal disorders including tendon contracture, tenosynovitis, joint stiffness, and osteoporosis. Recent studies with experimentally induced models of diabetes show that insulin therapy mitigates such alterations. These data are from relatively short-term experiments. This manuscript reports the results of tensile failure experiments on the canine patella-patellar tendon-tibia complex from a group of juvenile diabetic animals that received insulin therapy. The duration of the disease was 4-9 yr. The stiffness of the diabetic preparations in a physiological range of loading was approximately 13% greater than controls (P < 0.05). On the other hand, the strength of the tendon preparation from the diabetic population was not different from controls, but the mode of structural failure for controls was by substance and avulsion fractures while the diabetics failed by tensile fracture of the patella.

Mechanical properties of the canine patellar tendon: some correlations with age and the content of collagen.

Portions of the patellar tendon (PT) are currently used for autogenous and allogeneic reconstruction of a torn or damaged anterior cruciate ligament (ACL). Age-related changes in the mechanical properties of the PT may influence its use in this reconstruction procedure. Age-dependent changes in the PT were determined in the dog, which is often used to experimentally study this reconstruction. Tensile failure experiments were performed at 100% s-1 on patella-patellar tendon-tibia preparations from dogs aged 0.5-15 yr. The contents of collagen soluble and insoluble in pepsin were also measured at each age. Fifty-nine percent (16/27) of the preparations failed by avulsion at the patella, but neither the failure load nor the mode of failure were a function of age. Failure load and energy were higher for tendon substance failures compared to avulsions of bone from the patella. While a positive, linear correlation was measured between tensile modulus of the PT and age, the slope of regression was not significantly different from zero. The content of total collagen in the PT decreased significantly with age. The content of collagen insoluble in pepsin, however, increased with age and positively correlated with tensile modulus of the tendon. These results are different from those reported for the canine CCL, by others, which degenerates with age. Age-related changes in the mechanical properties of the canine PT are qualitatively similar to earlier, limited data on human patellar tendons.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of immobilization versus exercise on scar formation in the rabbit patellar tendon after excision of the central third.

There is much discussion about the appropriate timing and intensity of rehabilitation after reconstruction of the anterior cruciate ligament with a patellar tendon autograft. The purpose of this study was to look at two extremes (complete immobilization and vigorous, forced exercise) on the extent of scar formation and mechanical properties of the host tendon. Three groups of six Flemish Giant rabbits had the central third patellar tendon removed in one limb. Group I was sacrificed immediately after surgery. Group II was exercised on a treadmill for 12 weeks. In Group III the limb was immobilized for 12 weeks. After 3 months, average length and cross-sectional area from Group II were greater than those of the controls and Group III tendons. Structural properties of all tests limbs were similar to each other but different from controls. Tensile modulus of Group III tendons did not decrease as much that of Group II tendons. Histology revealed a clear demarcation between the central defect and host tendon in Group III, whereas Group II tendons remodeled throughout their cross-sections. We propose that early joint mobility produces large multiaxial stresses in original tendon leading to microdamages and repair processes within the entire host tissue. Less aggressive exercise or delay in joint mobility may help control tissue remodeling.

Technique for measuring the area of canine articular surfaces.

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.

Kinematic gait analysis of hind limb symmetry in dogs at the trot.

OBJECTIVE: To describe intratrial differences in hind limb symmetry in healthy dogs at the trot, using noninvasive, computer-assisted, three-dimensional kinematic gait analysis. ANIMALS: 8 clinically normal large-breed adult dogs. PROCEDURE: 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. RESULTS: 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. CONCLUSIONS: 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. CLINICAL RELEVANCE: 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.

Kinematic gait analysis in dogs with hip dysplasia.

OBJECTIVE: To define alterations of movement in dogs with hip dysplasia by use of noninvasive, 3-dimensional, computer-assisted kinematic gait analysis. DESIGN: Kinematic and force plate data were collected at the trot from clinically normal dogs and from dogs with hip dysplasia. ANIMALS: 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. PROCEDURE: 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. RESULTS: 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. CONCLUSIONS: 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. CLINICAL RELEVANCE: The information obtained may be useful in future evaluations of various modes of treatment for hip dysplasia.

Noninvasive kinematic analysis of the walk in healthy large-breed dogs.

OBJECTIVES: To use computer-assisted kinematic analysis to describe the walk in healthy dogs and to adapt Fourier transformation for analysis of the data. DESIGN: Evaluation of normal walk in dogs, using kinematic and force plate analysis. SAMPLE POPULATION: 15 healthy large-breed dogs. PROCEDURE: 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. RESULTS: 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. CONCLUSIONS: 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. CLINICAL RELEVANCE: 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.

Use of force-plate analysis of gait to compare two surgical techniques for treatment of cranial cruciate ligament rupture in dogs.

OBJECTIVE: 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. ANIMALS: 18 healthy dogs. DESIGN: 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. PROCEDURE: 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. RESULTS: 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. CONCLUSION: 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.

Additional kinematic variables to describe differences in the trot between clinically normal dogs and dogs with hip dysplasia.

OBJECTIVE: To describe the abnormal gait of dogs with hip dysplasia by use of kinematic gait analysis. ANIMALS: 19 large-breed dogs with moderate to severe clinical and radiographic evidence of hip dysplasia and 10 clinically normal dogs (controls). PROCEDURE: Kinematic and force plate data were collected, and degree of coxofemoral joint abduction-adduction, mediolateral foot movement, distance between hind feet, maximum hind foot elevation, mediolateral pelvic movement, and coxofemoral joint angular acceleration were calculated. Essential Fourier coefficients were determined and used to reconstruct mean angular acceleration curves. Fourier coefficients and foot and pelvic movement data were compared between groups. RESULTS: Dogs with hip dysplasia had a greater degree of coxofemoral joint adduction and range of abduction-adduction and greater lateral pelvic movement, compared with controls. Foot movement variables did not differ significantly between groups. Coxofemoral joint angular acceleration was greater in the middle to end of the stance phase, whereas deceleration was greater in the late stance to early swing phase and middle to end of the swing phase in dogs with hip dysplasia, compared with controls. CONCLUSIONS AND CLINICAL RELEVANCE: Differences in degree of coxofemoral joint abduction-adduction, amount of mediolateral pelvic movement, and coxofemoral joint angular acceleration between clinically normal dogs and dogs with hip dysplasia may indicate a compensation in gait of affected dogs as a result of discomfort or biomechanical effects attributable to hip dysplasia and degenerative joint disease. Information gained from kinematic and kinetic gait analyses may be useful in evaluating treatments for hip dysplasia in dogs.

Contributions to variance in force-plate analysis of gait in dogs.

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.

Kinematic gait analysis of the trot in healthy greyhounds.

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.

Effects of subject velocity on force plate-measured ground reaction forces in healthy greyhounds at the trot.

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 (P < 0.05). Forelimb and hind limb vertical impulses decreased as velocity increased (P < 0.05). Significant variations were not observed for craniocaudal or mediolateral peak forces or impulses. It was concluded that velocity significantly (P < 0.05) influenced ground reaction forces and impulses, and must be controlled in experimental design.

Evaluation of limb symmetry indices, using ground reaction forces in healthy dogs.

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.

Kinematic evaluation of gait in dogs with cranial cruciate ligament rupture.

OBJECTIVE: 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. DESIGN: Hind limb lameness was evaluated prior to and at 1, 3, and 6 months after transection of the cranial cruciate ligament. ANIMALS: Seven clinically normal large dogs. PROCEDURE: 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. RESULTS: 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. CONCLUSIONS: 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. CLINICAL RELEVANCE: Methods were developed that will improve objective evaluation of CCLR and its treatment in dogs.

Computer-assisted three-dimensional gait analysis of amphotericin-induced carpal lameness in horses.

Motion of 6 clinically sound horses trotting at a speed of 4 m/s on a treadmill was captured by video cameras before and 9, 16, and 23 days after amphotericin-induced lameness to determine the quantitative variables of three-dimensional computer-assisted image analysis that objectively describe carpal lameness. Amphotericin-B was used to induce lameness, and phenylbutazone (2.2 mg/kg of body weight, PO, once) and butorphanol tartrate (0.1 mg/kg IM, q 6 h, to effect) were used to control discomfort. Four 60-Hz cameras were symmetrically placed around the treadmill to capture 6 seconds of images from retro-reflective spheres taped to the trotting horses. Images were transferred to a video-based digitizer and a computer work station, where 4 files of two-dimensional data were reduced to 1 file of three-dimensional data. The effect of lameness on motion analyzed was assessed by use of two-way ANOVA. Differences between means were assessed, using the Student-Newman-Keul's test (P < or = 0.05). Head and withers excursions, (dorsal vertical displacement of head and withers targets, respectively) during the sound forelimb support phase were increased significantly during all lameness measurement periods. Head excursion, but not withers excursion, during the lame forelimb support phase, was decreased significantly during all lameness measurement periods. Computer determinations of stride length swing phase, stance phase, forelimb abduction, and carpal and fetlock ranges of motion did not consistently characterize the lameness. It was concluded that three-dimensional computer-assisted image analysis could be used for objective lameness evaluation in horses and that head and withers excursions were the most consistent variables for assessing equine carpal lameness.