Atraumatic proximal radial nerve entrapment. Illustrative cases and systematic review of literature.

The aims of the present study were to describe atraumatic proximal radial nerve entrapment (PRNE) and potential strategies for management. We performed a comprehensive search of 4 electronic databases for studies pertaining to patients with atraumatic PRNE. Studies published between 1930 and 2020 were included. Clinical presentation, nerve conduction studies, electromyography, and treatment methods were reviewed. In order to outline management strategies, 2 illustrative cases of acute PRNE were presented. We analyzed 12 studies involving 21 patients with 22 PRNE (15 acute and 7 progressive). Sudden or repetitive elbow extension with forceful muscle contraction (n = 16) was the primary mechanism of injury. The two main sites of entrapment were the fibrous arch (n = 7) and hiatus of the lateral intermuscular septum (n = 7). Conservative treatment was performed in 4 patients and allowed for complete clinical recovery in all cases. The remaining 18 patients underwent epineurolysis (n = 16) or resection/repair of hourglass-like constriction (n = 2) between 1.5- and 120-months following diagnosis. Twelve patients experience complete recovery, while partial or no clinical recovery was reported in 1 and 4 cases, respectively; the outcome was unknown in 1 case. Atraumatic PRNE is rare and remains challenging with respect to diagnosis and treatment. Current literature suggests that primary sites of entrapment are the fibrous arch and hiatus of the radial nerve at the time of forceful elbow extension. Case series (IV) & systematic review (I)