Effect of upper tibial osteotomy on fibula movement and ankle joint motion.

Several techniques of upper tibial osteotomy in the treatment of unicompartmental osteoarthritis of the knee have been described. Osteotomy of the fibula is normally also carried out, or alternatively, dissection of the capsule of the proximal tibiofibular joint. There is concern, however, that this latter procedure may have an adverse effect on the mobility of the ankle joint and on fibula rotation. To investigate these suspected interactions we performed experimental studies in 14 cadaver legs. The vertical, lateral and rotational movements of the fibula were measured with the ankle in neutral (0 degrees) and maximal ankle dorsiflexion before and after performing an interligamental upper tibial osteotomy of a standardised valgus wedge. Maximal ankle dorsiflexion before the osteotomy produced external rotation of the fibula in most specimens, whereas after osteotomy this movement caused mainly internal rotation. In the neutral position of the ankle, upper tibial osteotomy lead to external rotation of the fibula. The upward movement of the fibula head after osteotomy was 0.64 cm on average. There was no measurable vertical motion of the fibula during ankle dorsiflexion either before nor after upper tibial osteotomy. Ankle dorsiflexion improved minimally after osteotomy. In conclusion, this study shows that upper tibial osteotomy with dissection of the capsule of the proximal tibiofibular joint has no adverse effect on movement of the fibula or of the ankle joint. In addition, unlike fibular osteotomy, this technique also has the advantage that the risk of common peroneal nerve injury is minimal.