FORCE, FATIGUE, AND THE CROSS-SECTIONAL AREA OF WRIST EXTENSOR MUSCLES AFTER RADIAL NERVE GRAFTING

THE FORCE AND fatigue of the wrist extensor muscles during maximal voluntary and tetanic contractions were measured and compared in the injured and noninjured extremities of 11 patients with radial nerve gap injury and in 9 normal volunteers. The cross-sectional area (CSA) of the wrist extensor muscles was determined by magnetic resonance imaging and was correlated with force. In the patient group, an average of three (range, 2-4) sural nerve cable grafts, measuring 11.5 +/- 5 cm (range, 5-20 cm) in length, were sutured to the nerve stumps at least 9 years before this study. Differences in the CSA values of the injured and noninjured arms were compared, and a ratio was established (CSA(R)). The mean CSA(R) was 82.9% +/- 14.3. These differences were not statistically significant (P > 0.10, paired t-test). Despite very well-recovered muscular mass, the maximal voluntary contraction force was found to be incompletely recovered by up to 62.7% +/- 23, when compared with the noninjured side (P < 0.05, paired t-test). The fraction maximal voluntary contraction force/CSA had decreased by up to 76.4% +/- 25.5 (P < 0.05, paired t-test). An increased fatigability of the affected muscles persisted in all patients. The patients' noninjured extremity behaved in the same way as that of the dominant extremity of normal volunteers with regard to force, lever, and CSA values. In the best-recovered patients, the relation of the maximal voluntary contraction force between the noninjured and the injured side was the same (90% +/- 9.9) as that found between the dominant and the nondominant extremity of normal volunteers (P < 0.05, paired t-test). In more than half of the patients, sural nerve cables provided adequate reinnervation of the wrist extensor muscles to enable them to recover and even to exceed the bottom 5% contraction force (139 N) reported by other authors for the normal male population. Several anatomical features of the radial nerve, however, also participated in a favorable outcome of the motor function after autografting of this nerve.