Jaw-Dropping Twist: A Case Report of Deep Fibular Neuropathy After Fibular Flap for Jaw Reconstruction

Case Diagnosis: Isolated deep fibular neuropathy secondary to jaw reconstruction

Case Description or Program Description: A 29-year-old female with a history of jaw osteosarcoma, treated with chemotherapy and radiation, underwent jaw resection and reconstruction using a fibular free flap. She presented post-operatively with persistent left great toe extension weakness and numbness in the first web space. With concern for peri-procedural nerve injury to the left deep fibular nerve during fibula harvest for jaw reconstruction, the patient was referred for electrodiagnostic testing of the left lower extremity.

Setting: Outpatient Musculoskeletal Clinic

Assessment/Results: Electrodiagnostic studies showed absent responses in the left fibular nerve to the extensor digitorum brevis (EDB) and reduced amplitudes in the left fibular nerve to the tibialis anterior. Needle EMG demonstrated ongoing denervation in the left extensor hallucis longus (EHL) and EDB, with evidence of prior denervation and partial reinnervation in the EDB. Sensory nerve conduction studies were normal.

MRI of the left tibia/fibula revealed postsurgical changes from fibular resection and non-visualization of the deep fibular nerve near the surgical site, suggesting superimposed denervation and confirming isolated deep fibular neuropathy distal to the branch to the tibialis anterior.

Discussion (relevance): Fibular free flaps are frequently used for mandibular reconstruction surgery due to their reliability and versatility (1). While osseous complications are well-documented, neurologic complications are less frequently reported, with some studies reporting 5.1% incidence (2). Furthermore, most fibular neuropathies occur at the fibular head, while isolated deep fibular neuropathies, as demonstrated here, are rare (3).

Conclusions: This case highlights the rare but significant complication of isolated deep fibular neuropathy following fibular free flap mandibular construction. Electrodiagnostic studies were crucial in accurately localizing the lesion, confirming the diagnosis, and planning appropriate management and rehabilitation strategies. Recognition of this rare complication was crucial for optimizing patient care and improving functional outcomes.