Factors Associated with Failed Ulnar Nerve Fasicle to Biceps Motor Branch Transfer: A Case Control Study
Andrew J Lovy, MD, MS; Nicholas Pulos, MD; Michelle Faupel, RN; Robert J. Spinner, MD; Allen Bishop, MD; Alexander Y. Shin, MD
Mayo Clinic, Rochester, MN
Introduction: Ulnar nerve fascicle (to the Flexor Carpi Ulnaris) to biceps motor branch transfer is a well described and reliable transfer to restore elbow flexion. However, there is a paucity of literature discussing predictors of failed transfers. The purpose of this study was to identify factors contributing to failed ulnar nerve fascile to biceps motor branch transfer.
Materials & Methods: A retrospective review of adult brachial plexus patients treated with an ulnar nerve fascicle to biceps motor branch transfer with a minimum 1 year follow-up was performed. Treatment failure was defined by modified British Medical Research Council grade <3 elbow flexion. Controls (M?4- elbow flexion) were randomly selected after matching age, sex and type of surgery. Demographics, mechanism, preoperative examination, and range of motion were compared between groups.
Results: A total of 36 patients, 18 failures and 18 controls, were identified. Average follow-up was 20 months (range, 12-28) in failures and 23 months (range, 12-49) in controls (p=0.34). Mean age (38.2 vs 32.9 years, p=0.25), BMI (28.3 vs 27.8, p=0.80), smoking status (33.3% vs 22.2%, p=0.71), and time from injury to surgery (6.3 vs 5.1 months, p=0.13) were similar between failures and controls. Rate of preganglionic injury was similar between groups (66.7% vs 55.6%, p=0.47), but partial C8/T1 involvement was significantly higher among failures (77.8% vs 27.8%, p=0.007). High energy mechanisms were noted for all patients with no difference in concomitant head injury (33.3% vs 27.8%, p=0.72) or ipsilateral upper extremity injury (50% vs 50%, p=0.99). All patients had preoperative FCU strength ?M4, however preoperative FCU weakness (M<5) was significantly more common in failures compared to controls (77.8% vs 33.3%, p=0.02). Additionally, rate of complete FCU recovery was significantly higher in controls (85.7% vs 7.1%, p=0.002). There was no difference in total arc of elbow motion in failures (117 °passive) compared to controls (124° active) (p=0.27).
Conclusions: Higher rates of failure following ulnar nerve fascicle to bicep transfer can be expected among patients with preoperative FCU weakness and in patients with initial complete brachial plexus injuries who recover lower trunk function with residual FCU weakness. Patients with recovering lower trunk function should be counseled regarding increased failure risk and alternative transfer option should be considered. The challenge and unanswered question is how to identify which patients will regain ultimate near normal FCU strength.
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