Background: Recent studies concerning the free fibular graft have focused on the high prevalence of donor-site morbidity. The prevalence of ankle pain has been reported to range from 10% to 40%, but its etiology is unclear. The literature is vague with regard to the amount of distal fibular bone that is needed to maintain ankle stability. The aim of the present study was to determine the percentage of the fibula that can be removed while still preserving ankle stability.

Methods: Eleven fresh, paired cadaveric legs were tested. One leg from each pair was tested with the foot mounted in three positions (neutral, 15° of inversion, and 15° of eversion) while an external and internal rotational torque and axial load were imposed. Each specimen was also mounted in a Telos apparatus, and a varus load was applied across the ankle. Each specimen was tested first with an intact fibula to establish baseline stability and then underwent sequential fibular resections, from proximal to distal, until ankle instability was encountered. The contralateral specimen from each pair was then used to evaluate repetitive loading of a stable distal fibular segment over 2000 cycles.

Results: Only 10% of the fibula was needed distally to maintain ankle stability. Once the residual fibular length was <10% of the total fibular length, a significant change in motion was seen in the ankle joint (p < 0.05). On visual inspection, a residual fibular length of 10% represented a fibular osteotomy just proximal to the syndesmotic ligaments. The greatest motion occurred with the ankle inverted and in external rotation. No significant change in ankle stability occurred during cyclic testing when the residual fibular length was 10% of the total fibular length.

Conclusions: While previous reports in the literature have suggested that 6 to 8 cm of residual distal fibular length is needed to maintain ankle stability, our data support the possibility that ankle stability can be maintained with even less residual fibular length.

Clinical Relevance: The fibula is the most frequent source of vascularized bone graft in microvascular limb reconstruction. Donor-site morbidity has been the focus of many recent clinical series. The present study provides details on what happens to ankle joint mechanics when large segments of the fibula are harvested.