Ground reaction forces in Greyhounds with tibial nerve injury.

OBJECTIVES To measure ground reaction force variables during lameness resulting from impaired tibial nerve function and to determine whether these variables changed significantly as recovery progressed. ANIMALS 11 healthy Greyhounds of either sex, weighing between 22 and 39 kg. PROCEDURE On 3 consecutive days before surgery, ground reaction forces were measured by force platform gait analysis at the trot. In dogs under general anesthesia, the left tibial nerve was crushed proximal to innervation of the gastrocnemius muscle. Gait analyses were repeated on days 8 to 10, 28 to 30, 43 to 45, 58 to 60, and 90 to 92 after surgery. Ground reaction force variables and stance time were compared among the 3-day clusters. RESULTS 10 days after surgery, all dogs had weight-bearing lameness attributed to paralysis of muscles in the caudal compartment of the crus. Nerve regeneration resulted in functional recovery within 3 months. Decreases in vertical force were significant 10 days after surgery; thereafter, changes reflected gradual return of load bearing, with the most marked improvement between 10 and 45 days. At 90 days, vertical force variables were within 3% of presurgical values. Stance time for the left hind limb was significantly longer at 10, 30, and 45 days after surgery and was seen in all dogs, but returned to within 1 % of preoperative stance time at 90 days. The effect of tibial nerve dysfunction on braking or propulsive force was not significant. CONCLUSIONS AND CLINICAL RELEVANCE The significant changes in vertical ground reaction forces in hind limbs of dogs during lameness that resulted from impaired tibial nerve function are detectable, as is response during recovery, by use of force platform analysis.