Proximal migration of fibular malleolus during tibial lengthening despite syndesmotic screw fixation: a series of 22 cases.

INTRODUCTION

During tibial lengthening procedures, it is recommended to prevent fibular malleolus proximal migration using a distal tibiofibular syndesmotic screw, which is removed at 6 months. We have observed proximal migrations of the fibular malleolus despite placement of this syndesmotic screw.

OBJECTIVE

The objective of this study was to demonstrate this migration and to study the influence of two factors that may favor its occurrence: positioning of the syndesmotic screw and union of the fibula at the time of removal.

HYPOTHESIS

An unhealed fibula at the time the distal tibiofibular syndesmotic screw is removed and its tricortical position promote the proximal migration of the fibular malleolus.

MATERIAL AND METHODS

This was a retrospective, single-center, analytical study that included 22 lengthening procedures in 18 patients from 5 to 17 years of age who had undergone tibial lengthening and presented a preoperative continuous fibula. The position of the fibular malleolus, union of the fibula, and the tri- or quadricortical position of the screw were assessed based on four successive x-rays.

RESULTS

Tricortical positioning of the syndesmotic screw was significantly associated with proximal migration of the fibular malleolus during lengthening (P=0.0248<0.05). However, there was no significant relation between an unhealed fibula and proximal migration of the fibular malleolus when the screw was removed (P=0.164>0.05).

DISCUSSION

Proximal migration of the fibular malleolus during lengthening is promoted by placing a non-quadricortical syndesmotic screw. Quadricortical positioning of the screw should be recommended. Migration of the fibular malleolus after ablation of the syndesmotic screw seems to be related to absence of fibular union but this series was too small to demonstrate this clearly.

LEVEL OF EVIDENCE

Level IV: Retrospective study.