Flexor Hallucis Longus Transfer for Foot Drop without Functioning Tibialis Posterior

Abstract

digitorum longus (EDL), peroneus longus (PL) and peroneus brevis (PB) revealed no function (MRC=0 (15)), while testing of FHL and FDL revealed full (MRC=5) strength. The TP was not functioning (MRC=0) with contracture limiting pronation beyond neutral. The gastrocnemius strength was 4 with contracture limiting dorsiflexion. Supination of the foot was unrestricted. The passive range of ankle motion was (0)-5-45° (equinus contracture of 5°). There was checkrein phenomenon of the toes at the limit of dorsiflexion. On x-ray there were no signs of arthritis in the hindfoot. Patient scored 74 and 71 points in FAOQ (2) and AOFAS (8) scales, respectively. Decision processWith no return of peroneal nerve function in two years observation, neither improvement in conduction studies despite neurolysis, the nerve injury was deemed irreparable. The patient was unwilling to accept the brace and he opted for operative treatment. With no voluntary contraction of TP this tendon was deemed unsuitable for transfer. Fibrotic degeneration of TP is visible in MRI (Fig. 1). With no functioning TP, two potential motors were available -FHL and FDL. We chose to transfer the FHL tendon to the dorsum of the foot. Operative technique and aftertreatmentThe patient was operated supine without a tourniquet (due to previous vascular reconstruction). Z-lengthening of the Achilles tendon was performed through stab incisions (18). By this maneuver 10 degrees of dorsiflexion was achieved. Dorsiflexion exacerbated the checkrein deformity of the toes. Medial approach to the midfoot