Bodily KD, Mayo Medical School, 200 First Street S.W, Rochester, MN, USA, Spinner RJ, Departments of Neurologic Surgery and Orthopedics, Mayo Clinic, 200 First Street S.W, Rochester, MN, USA, and Bishop AT, Division of Hand and Microvascular Surgery, Mayo Clinic, 200 First Street S.W, Rochester, MN, USA.
Background: Stretch injuries to the common peroneal nerve, frequent at the time of varus knee injury, result in significant morbidity due to loss of ankle dorsiflexion. Reconstruction is often unsuccessful because of the length of the nerve lesion, sometimes extending from its proximal origin of bifurcation high in the popliteal fossa to the point of its terminal bifurcation several centimeters distal to the fibular head. Such lengthy injuries are poor candidates for sural nerve grafts. Furthermore, tendon transfer often does not eliminate the need for bracing and may result in late hind foot valgus and arthritis. When these options fail, chronic use of an ankle-foot orthosis is necessary. The objective of this study was to determine the anatomical feasibility of an alternative option, consisting of nerve transfer of motor branches from the tibial nerve to the deep peroneal nerve. This technique bypasses the zone of injury, obviates the need for an intercalary nerve graft and decreases regeneration time by reconstructing the nerve as close as possible to the end-organ. All of these advantages should improve the results of primary nerve reconstruction. Methods: In 10 cadaveric limbs, the branching pattern, length, and diameter of motor branches of the tibial nerve in the proximal leg were characterized. Nerve transfer of each of these motor branches was then simulated to the proximal deep peroneal nerve. Results: A consistent, reproducible pattern of innervation was seen with minor variability. Branches to the flexor hallucis longus and flexor digitorum longus muscles were determined to be adequate for direct nerve transfer in all specimens without interpositional graft based on their diameter and length. Other branches, including those to the tibialis posterior, popliteus, gastrocnemius, and soleus muscles were not consistently adequate for repair of injuries extending to the bifurcation of the common peroneal nerve. For neuromas that do not extend as far distally, branches to the soleus and lateral head of the gastrocnemius may be adequate if the intramuscular portions of the nerves are dissected. Conclusion: This study confirms the anatomical feasibility of direct nerve transfer using nerves to toe-flexor muscles as a treatment option to restore ankle dorsiflexion in cases of common fibular nerve injury.