Biomechanical assessment of a new tenodesis for correction of hallux varus

Each of six below-the-knee amputation specimens were transfixed to a wooden block and mounted to a jig on an amputee testing device preloaded with 5 N applied to the proximal phalanx and displaced at a constant rate of 2 mm/min. Load displacement curves were generated for the intact joint and after sequential incisions of the lateral capsule, the adductor hallucis, and the lateral slip of the flexor hallucis brevis tendon, which caused varus dislocation of the hallux. An extensor hallucis brevis tenodesis was performed after the varus dislocation. Division of the lateral capsule, the adductor, and the flexor brevis reduced the force required to displace the hallux by 42.2%, an additional 25.2%, and a further 14.2%, respectively. Use of the extensor hallucis brevis tenodesis restored the load displacement curves to that of the normal joint. We concluded that the extensor hallucis brevis tendon may be useful as a tenodesis for reconstructing the deformity of acquired hallux varus.