Clinical diagnosis and wide-awake surgical treatment of proximal median nerve entrapment at the elbow: a prospective study
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Proximal median nerve entrapment (PMNE, or pronator syndrome) at the elbow has traditionally been considered an elusive and rare diagnosis, as it is seldom detectable using electrophysiological techniques. In this paper, the clinical manifestations, physical diagnosis, surgical technique, and results of surgical treatment of PMNE are presented, with accompanying instructional video.
During 2011, 44 patients with PMNE were surgically released and followed prospectively, 22 women/22 men, mean age 48.8 (range 25–66). The patients were equally distributed between right/left hands (23/21) and the dominant hand was treated in 56 % of cases. The diagnosis was based on: (1) weakness in median innervated muscles distal to the lacertus fibrosus; (2) pain upon pressure over the median nerve at the level of the lacertus fibrosus; and (3) positive scratch collapse test. A minimally invasive surgical treatment using only local anesthesia with lidocaine–epinephrine and no tourniquet was used, and direct perioperative return of strength in median innervated muscles was seen in all subjects.
The average preoperative quick DASH was 35.4 (range 6.8–77.2); work DASH, 44.3 (6.25–100); and activity DASH, 61.6 (12.5–100). There were 71.1 % patients who completed the 6-month follow-up, and the average postoperative quick DASH was 12.7 (range 0–43.1), which is a statistically significant reduction (p < 0.0001; Student’s paired t test). Similarly, the work and activity DASH was significantly reduced (p < 0.001) to 12.5 (0–75) and 6.25 (0–50), respectively.
PMNE at the level of the lacertus fibrosus should be called lacertus tunnel syndrome to distinguish it from other levels of median nerve entrapment. It is a clinical diagnosis based on three distinct clinical findings: weakness, pain over point of compression, and positive scratch collapse test. Surgical release in local anesthesia allows for a safe, ambulatory, and cost-efficient procedure with low morbidity.
KeywordsEntrapment Median nerve Pronator syndrome Surgery Wide-awake
Conflict of Interest
The authors declare that they have no conflict of interest.
The video shows the scratch collapse test in a patient with right-sided lacertus tunnel syndrome. The patient is asked to sustain external rotation of the shoulders with elbows flexed, while the skin over the area of nerve compression is scratched, eliciting a temporary loss of muscle resistance. The healthy left side is compared to the contralateral side where a lacertus tunnel syndrome is present. (MOV 14518 kb)
The video illustrates the preoperative clinical examination of a patient with proximal median nerve entrapment (“lacertus tunnel syndrome”), where the flexor carpi radialis (FCR), flexor pollicis longus (FPL), and flexor digitorum profundus of the index finger (FDP II) are found to be weak, as compared to the healthy arm. The appearance of the arm following infiltration anesthesia, detailed description of the surgical technique and immediate peri-/postoperative return of strength following nerve release is also shown in this instructional video. (MOV 206403 kb)
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