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.

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.

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.

Bilateral distal fibular growth abnormalities in a dog.

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.