Serial force plate analyses of dogs with unilateral knee instability, with or without interruption of the sensory input from the ipsilateral limb

Objective and Design We characterized the mean peak vertical forces (MFz) in five groups of dogs which underwent transection of the left anterior cruciate ligament (ACLT) or sham ACLT and ipsilateral dorsal root ganglionectomy or sham-ganglionectomy, and the relationship of these forces to the severity of osteoarthritis (previously reported) 72 weeks after arthrotomy. Group I ( N =7) underwent ACLT; Group II ( N =8) underwent ACLT followed 52 weeks later by ganglionectomy; Group III ( N =7) underwent ganglionectomy followed 2 weeks later by ACLT; Group IV ( N =7) underwent sham-ganglionectomy followed 2 weeks later by ACLT; Group V ( N =8) underwent ganglionectomy followed 2 weeks later by sham-ACLT. The dogs were evaluated 2, 6, 12, 24, 52 and 72 weeks after arthrotomy. Results From 6 weeks after arthrotomy until death, the left hindlimb MFz in Group V was significantly greater ( P 0.05) than that in the other four groups. The MFz of all groups which underwent ACLT decreased after arthrotomy. While the MFz of Group III (very severe OA) was about 10–20% greater than that of Groups I, II and IV (mild OA) 6 and 12 weeks after ACLT, and generally about 5–10% greater subsequently, this difference was not statistically significant. The MFz of Group II returned to pre-ganglionectomy levels, rather than to baseline levels, following ganglionectomy. Conclusions (1) since the ipsilateral limb of dogs with ganglionectomy+sham ACLT bore normal amounts of weight throughout most of the postsurgical period, and its knee did not develop OA, one cannot argue that the knee was protected from OA because the limb was not used; (2) the fact that the MFz of dogs which underwent ACLT+ganglionectomy returned to pre-ganglionectomy levels, rather than baseline, is consistent with the hypothesis that the unstable joint was protected from accelerated breakdown by a central nervous system that was reprogramed by sensation from the unstable limb; (3) the slightly—but consistently—greater MFz of dogs which underwent ganglionectomy+ ACLT may contribute to the acceleration of OA in this model.