Effect of tibial plateau leveling osteotomy on femorotibial subluxation: in vivo analysis during standing.

OBJECTIVE

To assess the effect of tibial plateau leveling osteotomy (TPLO) on femorotibial subluxation during standing in dogs with cranial cruciate ligament (CrCL) insufficiency.

STUDY

DESIGN

Prospective clinical study.

ANIMALS: Fifteen dogs weighing 20-45 kg with unilateral complete CrCL insufficiency.

METHODS

Force-platform analysis, and lateral weight-bearing radiographs of the affected stifle were acquired preoperatively, 1, 3, and 6 months postoperatively. The distance between the origin and insertion of the CrCL (CrCL(d) ) was measured on each radiograph and compared between time points using ANOVA. Lateral radiographs of the non-weight-bearing affected stifle and weight-bearing contralateral normal stifle were acquired preoperatively, and CrCL(d) was compared with a paired t-test. Dogs were grouped according to medial meniscal status (intact or hemimeniscectomy) and CrCL(d) was compared within each group using ANOVA.

RESULTS

No difference was observed in CrCL(d) between the non-weight-bearing affected stifle and the contralateral stifle (P = .994). That is, femorotibial joint alignment in the affected stifle when non-weight-bearing was considered normal. Preoperatively in the affected stifle, CrCL(d) during weight-bearing was 6.3 ± 2.4 mm longer than normal (P < .001). Postoperative weight-bearing CrCL(d) in dogs with intact menisci at all time points was not statistically different from normal; CrCL(d) at 1 (P = .014) and 6 months (P = .005) postoperatively was longer than normal in dogs with hemimeniscectomy.

CONCLUSIONS

TPLO does not consistently resolve femorotibial subluxation during standing in dogs with CrCL insufficiency. The medial meniscus appears to be an important contributor to stability in stifles treated by TPLO.