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.

Minimally displaced tibial tuberosity avulsion fracture in nine skeletally immature large breed dogs.

OBJECTIVE: 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.

In vitro mechanical evaluation of a limited contact dynamic compression plate and hybrid carpal arthrodesis plate for canine pancarpal arthrodesis.

OBJECTIVE: 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 <0.05). RESULTS: Regardless of load, CC was 29% to 33% smaller in the HP than the LC-DCP group (p <0.03). In each group, the CC significantly increased with increasing loads (p <0.02). Mean MAD was 19% to 22% less in HP than LC-DCP constructs, with significant differences seen at 200N and 300N loads. In both groups, MAD was significantly greater with increasing loads (p <0.02). In addition, PPS was 37% to 43% smaller for HP than LC-DCP. 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.

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.

Comparison of trochlear block recession and trochlear wedge recession for canine patellar luxation using a cadaver model.

OBJECTIVE: To compare trochlear block recession (TBR) to trochlear wedge recession (TWR) with regards to patellar depth (percentage of patellar volume under the trochlear ridges), patellar articular contact, percentage of recessed trochlear surface area, and resistance to patellar luxation. STUDY DESIGN: In vitro computed tomography (CT) and biomechanical evaluation using a cadaver model. SAMPLE POPULATION: Twelve normal, large-breed canine cadavers. METHODS: Bilateral pelvic limb specimens with intact stifle joints were mounted on a positioning device. The femoral trochlear ridges were reduced to provide a standard shallow trochlea. TBR or TWR was performed to a standard depth randomly on paired specimens. CT and biomechanical evaluations were performed pre- and postoperatively in both an extended (148 degrees ) and flexed (113 degrees ) stifle position. CT images were digitized and measurements made using an image-analysis software program. Biomechanical testing consisted of applying 40 degrees of internal tibial rotation and documenting patellar luxation. RESULTS: The change in trochlear depth (depth of recession) was not significantly different between groups. In the extended stifle position (patella in the proximal trochlea), patellar depth and patellar articular contact with the recessed trochlea were significantly greater after TBR compared with TWR. The percentage of recessed trochlear surface area was significantly greater after TBR compared with TWR. In the extended position, a smaller percentage of the patellae luxated within 40 degrees of internal tibial rotation after TBR compared with TWR. CONCLUSIONS: TBR increases proximal patellar depth, increases patellar articular contact with the recessed proximal trochlea, recesses a larger percentage of trochlear surface area, and results in a greater resistance to patellar luxation in an extended position as compared with TWR. CLINICAL RELEVANCE: TBR may help limit the development of stifle DJD in dogs treated for canine patellar luxation.

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.

Radiographic, biomechanical, and pathologic effects of hemoglobin glutamer-200 in dogs undergoing cemented total hip arthroplasty.

OBJECTIVE: 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. ANIMALS: 9 adult dogs. METHODS: 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. RESULTS: 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. CONCLUSIONS AND CLINICAL RELEVANCE: 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.

External skeletal fixation. Linear fixators.

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.

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.

Efficacy of etodolac for the treatment of osteoarthritis of the hip joints in dogs.

OBJECTIVE: To assess the efficacy of etodolac in improving hind limb function in dogs with osteoarthritis of the hip joint. DESIGN: Prospective study. ANIMALS: 100 client-owned dogs with clinical signs of osteoarthritis of the hip joint. PROCEDURE: 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. RESULTS: 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. CLINICAL IMPLICATIONS: 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.

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.

Analysis of acute mechanical insult in an animal model of post-traumatic osteoarthrosis.

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 subchondral 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.

Kinetic and kinematic gait analysis and the assessment of lameness in the dog.

The current state of canine kinetic and kinematic gait analysis, as developed for the objective description of movement for the study of musculoskeletal disease and lameness, is reviewed. Basic terminology of gait is discussed. Ground reaction forces, dynamic flexion, and extension angles and angular velocities are described for the canine walk and trot and for lameness in cranial cruciate ligament rupture and canine hip dysplasia.

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.

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.

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.