Axillary to Radial Nerve Transfer for Recovery of Elbow Extension After Spinal Cord Injury

Abstract

Background and objectives: Cervical spinal cord injuries (SCI) result in severe loss of function and independence. Nerve transfers have become a powerful method for restoring upper extremity function, the most critical missing function desired by this patient population. Recovery of active elbow extension allows for expansion of one's workspace to reach for objects and stabilizes control at the elbow joint. Without triceps function, a patient with a cervical SCI is rendered entirely helpless when in the supine position. Our objective was to provide a concise description of the transfer of branches of the axillary nerve (AN) to the long head of the triceps branch of the radial nerve (RN) for restoration of elbow extension after cervical SCI.

Methods: An anterior, axillary approach is used for the transfer of the nerve branches of the AN (which may include branches to the teres minor, posterior deltoid, or even middle deltoid) to the long head of the triceps branch of the RN. Preoperative assessment and intraoperative stimulation are demonstrated to direct optimal selection of axillary branch donors.

Results: The axillary approach provides full access to all branches of the AN in optimal proximity to triceps branches of the RN and allows for tension-free coaptation to achieve successful recovery of elbow extension. Final outcomes may not be achieved for 18 months. Of our last 20 patients with greater than 12-month follow-up, 13 have achieved antigravity strength in elbow extension, 4 are demonstrating ongoing progression, and 3 are definitive failures by 18 months.

Conclusion: The axillary to RN transfer is an important intervention for recovery of elbow extension after cervical SCI, which significantly improves quality of life in this patient population. Further large population outcomes studies are necessary to further establish efficacy and increase awareness of these procedures.

FIGURE 1.

Preoperative assessment. A comprehensive preoperative assessment is necessary to achieving good outcomes for patients. This includes physical examination, qEMG, transcutaneous muscle stimulation, and shoulder MRI. A, A physical examination is performed to assess MRC strength of the relevant muscles. Donor strength should be at least M4. Our team also performs qEMG to estimate the number of motor units to relevant muscles. High-frequency stimulation is performed to determine whether the recipient remains innervated (preserved lower motor neurons, but nonvolitional because of loss of descending brain input). This will determine how urgent surgery should be performed in more acute cases and whether the recipient is viable in chronic cases. B, MRI may also be useful, especially to C, assess for signs of denervation (edema, fat infiltration, atrophy). In the MRI image shown, the supraspinatus and infraspinatus are intact, while the posterior deltoid and teres minor have undergone fibrosis and atrophy. D, In a healthy subject, scapulohumeral rhythm to achieve shoulder abduction occurs at a ratio of 2° of humeral flexion/abduction to 1° of upward scapular rotation. E, Weakness of the teres minor and posterior deltoid impedes scapulohumeral rhythm and shoulder abduction. In addition, weakness of the serratus anterior muscle does not allow the scapula to be pulled tightly to the posterior chest wall, causing upward rotation of the medial border of the scapula, which detracts from humeral abduction. MRC, medical research council; qEMG, quantitative electromyogram.

FIGURE 2.

Surgical anatomy. A, Graphical and B, surgical representation of the relevant anatomy as seen with the anterior axillary exposure after neurolysis of the axillary and RN. The axillary nerve divides into an AD, posterior division (subdividing into PD and LBC), and TMi branches. The RN gives rise to the PCB, LHT, and upper medial head of the triceps before continuing over the latissimus dorsi muscle tendon to further innervate the triceps and select forearm muscles. The LHT is divided and reflected distally in the image. AD, anterior division; LBC, lateral brachial cutaneous nerve; LHT, long head of triceps branch; PCB, posterior cutaneous branch; PD, posterior deltoid branch; RN, radial nerve; TMi, teres minor branch.