Radial nerve reconstruction at secondary synthesis of the humerus
Background. Proximal injuries of the radial nerve are most commonly associated with orthopedic trauma. Secondary synthesis of the humerus combined with the radial nerve injury leads to postponement of the nerve reconstruction, and is associated with major technical difficulties, thereafter, impacts the recovery outcomes. The purpose of the study was to evaluate the efficacy of the radial nerve reconstruction via grafting technique, to define the influence of the stump transfer maneuver on the gap length at secondary humeral synthesis. Materials and methods. This study presents a retrospective analysis of the consecutive series of 16 patients with proximal radial nerve injury over a 4year period (2013–2016). Twelve men and four women were enrolled into the study. The mean age of enrolled patients was 34.5 years (range 19–54). The mean time from occurrence of injury to primary humeral osteosynthesis was 4.8 months. Sixteen patients received secondary humeral synthesis due to absence of fracture consolidation with Bilinskyy synthesis device within mean term of 3.9 months after primary humeral synthesis. Sixteen patients underwent autologous nerve grafting in order to reconstruct radial nerve continuity. Mean gap length between proximal and distal stumps of radial nerve was the critical one in all patients (10 cm or higher). All sixteen cases of proximal radial nerve injury required transfer of both stumps onto the medial aspect of the shoulder in order to shorten the gap between the stumps. All grafts were sutured under microscopic magnification (5–8 times) with 8/0 — 10/0 nonabsorbable monofilament suture in a tensionfree manner with 180 degrees extended forearm. All patients received standard therapy in postoperative period, which included antibiotics and painkillers. No early or delayed complications associated with surgery were observed. The mean followup period was 1 year 8 months. The followup period included clinical neurological examination with evaluation of muscle strength with Medical Research Council Grading System (MRCS), ENMG in 3, 9, 12 and 15 months after surgery followed by “ondemand” examination. Results. Mild to moderate strength in wrist extensors was detected on the 10th month among younger patients (under 21 years). Mean term of wrist extensors recovery was 13 months. First signs of finger extensors reinnervation did not differ among younger patients versus older ones; mean term of finger extensors recovery was 14.5 months. The recovery of thumb extensors and abductors in the majority of patients initiated simultaneously with finger extensors, wherein their strength reached their maximum on the 15th month and showed no tendency to improve with time. Summarizing the outcomes of radial nerve reconstruction via grafting technique we conclude that the recovery of the entire complex of thumb, fingers and wrist extensors was achieved only in 8 out of 16 cases (50 %). Better recovery of more proximal radial extensors (100 % of cases) was still accompanied by the lack of consistency within the outcomes, wherein 68.75 % showed recovery of both radial wrist extensors. The more distally the extensors were situated, the more dramatically grew the inconsistency of recovery: 87.5 % showed sufficient recovery of thumb extension, 62.5 % showed sufficient recovery of all finger extensors, and only 50 % showed recovery of thumb abduction. All 6 patients (37.5 %) with incomplete recovery of finger extensors required tenodesis of the finger extensors to provide simultaneous extension in MCP joints in later terms. In much later terms another 7 patients (43.75 %) with complete but ineffective recovery of thumb abductors of the dominant hand and no reliable improvement with time required PL transfer to restore proper thumb abduction. In some patients the recovered functions of proximal and distal extensors were accompanied by simultaneous activation of thumb and wrist extensors with complete loss of movement independency most probably due to the phenomenon of heterotopic reinnervation. They required injection of botulinum toxin either into thumb or wrist extensors during the reeducation process in order to turn temporary the “parasite” movements off. Two patients with entirely recovered complex of wrist and finger extensors suffered from neuropathic pain and required longterm intake of painkillers. No patient showed poor or no consolidation of the humeral fracture after secondary synthesis. Eleven patients underwent removal of the secondary osteosynthesis device in much later terms (mean 11.4 months). Conclusions. Radial nerve stump transfer maneuver helped us to decrease the gap up to (mean) 2.75 cm, and in 4 cases decreased the gap to subcritical (under 7 cm); the recovery of the entire complex of thumb, fingers and wrist extensors was achieved only in 8 out of 16 cases (50 %); considering the unpredictability of recovery of the proximal radial nerve after injuries, lack of the consistency within the recovery outcomes we find it necessary to implement into daily practice the innovative distal mediantoradial nerve transfer.
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