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Femoral Nerve Transfers for Restoring Tibial Nerve Function: An Anatomical Study and Clinical Correlation
Amy M. Moore, MD; Michael J. Franco, MD; Rajiv P. Parikh, MD; Daniel A. Hunter; Thomas H. Tung, MD
Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, St. Louis, MO
Introduction: Sciatic nerve injuries are devastating and result in loss of lower leg function and impaired ambulation. While nerve transfers are commonly used to restore upper extremity function, their use in lower extremity nerve injuries is rare. To demonstrate the restoration of tibial nerve function with nerve transfer from terminal quadriceps motor branches, an anatomical study and two clinical cases were performed.
Methods: In six cadaver legs, we noted the length and the branching patterns of the terminal motor branches of the femoral nerve to the vastus medialis and lateralis muscles, and the neurolysis length of the gastrocnemius and the sural nerves. Histomorphometry was performed on both the donor and recipient nerves. Clinically, the nerve transfers included transfer of the terminal branches of vastus medialis and lateralis to the medial and lateral gastrocnemius branches respectively in the distal thigh, and sensory transfer of the saphenous nerve to the sural nerve.
Results: A consistent branching pattern and location of the saphenous nerve and terminal femoral motor nerve branches in the thigh were noted. The terminal motor branches to the vastus medialis and lateralis were identified at 13.2±1.7 and 16.7±3.5 cm superior to the medial and lateral patella, respectively. The neurolysis lengths of the medial and lateral gastrocnemius branches and the sural nerve were 8.4±1.2, 8.2±2.7, and 11.4±3.2 cm respectively, and allowed for anterior transposition for direct transfer from the femoral donors. Transfer of the vastus lateralis terminal branch required a short nerve graft in most specimens. In two patients at one year follow-up, MRC grade 3/5 gastrocnemius function was restored with active plantar flexion and improved ambulation. Because muscle reinnervation was first noted 6-8 months after surgery, these results are early and greater strength and coordination are anticipated. One patient has even returned to competitive sports with the use of a footdrop splint. An advancing Tinel’s is found at the distal lower leg in both patients, indicating sural nerve reinnervation. A planned transfer of the sural nerve to the distal tibial nerve at the tarsal tunnel for plantar sensation has been performed in one patient.
Conclusions: This study confirms the anatomical feasibility and clinical success of femoral to tibial nerve transfers to restore gastrocnemius and sural nerve function after a devastating sciatic nerve injury. Use of the femoral nerve for nerve transfer has untapped potential and could also be considered to restore ankle dorsiflexion in cases of common peroneal palsy.
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