Applied anatomy of recurrent branch of median nerve and microsurgical treatment of its compression syndrome / 中华显微外科杂志

ABSTRACT

Objective:To observe the anatomy of the recurrent branch of median nerve, summarize the injury mechanism of the recurrent branch of median nerve, and explore the surgical method and clinical effect of the compression.Methods:From February 2018 to October 2021, 12 fresh hand specimens were used in Department of Hand Surgery in the Second Hospital of Tangshan, including 6 male specimens, 3 left and 3 right hands, and 6 female specimens, 3 left and 3 right hands. Anatomy of the recurrent branch of median nerve and observation of its location, measurement of the length of each muscle branch innervating thenar muscle and the easy-to-jam position of the recurrent branch of median nerve in the course of running. The measurement results uses nonparametric test of statistical analysis by side and gender. P<0.05 was considered statistically significant. From January 2020 to January 2022, 21 patients with entrapment of the recurrent median nerve of wrist were treated, 14 males and 7 females. The age ranged from 31 to 65 years old, with an average of 46.2 years old. All patients developed thenar muscular atrophy. Before operation, the recurrent branch of median nerve was marked into the muscle point, and the thenar projection on palm surface was pressed, which caused fatigue and soreness. Electromyography examination the motor latency of median nerve endings was more than 4.5 ms, and both fibrillation potential and positive potential appeared. The motor conduction velocity of all patients was less than 30 m/s, and the motor nerve amplitude was less than 10 mV. Surgical exploration of the recurrent branch of median nerve revealed that the trunk of the recurrent branch of median nerve made the tendon arch thickened at the starting point of the superficial head of flexor pollicis brevis, and there was compression between the deep layer of the palmar aponeurosis and the thenar musculocutaneous membrane, which was completely released during the operation to relieve the compression factor. All 21 patients had followed-up in outpatient. Results:Distance from the origin of the recurrent branch of median nerve to the distal edge of transverse carpal ligament. The distance from the origin of the recurrent branch of median nerve to the distal edge of transverse carpal ligament were (0.30, 0.31, 0.32) cm and (0.31, 0.32, 0.32) cm in male left and right groups, respectively, with no statistical significance ( Z=-0.943, P=0.346); The female left and right groups were (0.28, 0.28, 0.28) cm and (0.29, 0.30, 0.30) cm, respectively, and the difference was statistically significant ( Z=-2.121, P=0.034). The length and transverse diameter of the trunk of the recurrent branch of the median nerve, the length of the superficial head branch of flexor pollicis brevis and the length of the palmar muscle branch of the thumb had no significant difference between the left and right sides of males and females( P > 0.05). The length of abductor pollicis brevis muscle branch the male left and right groups were (1.45, 1.27, 1.31) cm and (1.54, 1.38, 1.47) cm, respectively, and there was no statistical difference ( Z=-1.528, P = 0.127); The female left and right groups were (1.21, 1.18, 1.15) cm and (1.25, 1.24, 1.25) cm respectively, and the difference was statistically significant ( Z=-1.993, P=0.046). All the 21 patients were entered in follow-up for 9-24 (average 15) months. After operation, the wounds of all patients healed in the first stage, the soreness at thenar disappeared, and the thenar muscle was full in appearance. In 21 patients, the thumb abduction function returned to normal, the thumb to palm opposition returned to normal in 19 cases, and was slightly limited in 2 cases. After operation, thenar muscle strength recovered to grade 5 in 19 cases and grade 4 in 2 cases. At the last follow-up, electromyography showed that the motor latency of median nerve endings was less than 4.5 ms, and the motor conduction velocity was greater than 40 m/s; Motor nerve amplitudes were all greater than 10 mV. According to the functional evaluation standard of carpal tunnel syndrome recommended by Gu Yudong, 19 cases were excellent, 2 cases were good, and the excellent and good rate was 100%. Conclusion:The length of each nerve branch of the recurrent median nerve innervates thenar muscle is different, and there are many factors that cause the recurrent median nerve to get stuck. It is of high clinical value to master the anatomical structure of the recurrent median nerve and the mechanism of the entrapment, and to completely loosen vulnerable parts by surgery.