Migration of the Fibula During Tibial Lengthening in Achondroplasia

Complications arising from tibial lengthening in achondroplasia include (1) delayed consolidation of the fibula, (2) premature consolidation of the fibula, (3) angulation or translation of the fibula, and (4) valgus angulation of the ankle or the knee (Kim et al., Acta Orthop 83:271–5, 2012). These can be attributed to the slower fibular distraction rate compared to the tibial distraction rate, resulting in a lagging behind of the lateral malleolus compared to the distal tibia. A study on the effect of these distraction-resisting forces measured the tibiofibular distraction difference, the proximal tibiofibular joint distraction, the distal tibiofibular joint distraction, and the mean tibial valgus angulation of patients who underwent tibial lengthening (Shyam et al., J Bone Joint Surg 91:1671–82, 2009). They concluded that if the aim of lengthening is more than 25% of the initial tibia length, one should expect an increase in knee laxity, and if it is more than 50% of the initial length, one should expect an increase in tibial valgus angulation.