Is the anconeus epitrochlearis muscle a predictor for ulnar nerve compression?

The role of the anconeus epitrochlearis (AE) in cubital tunnel syndrome, either as protector or potential compressor of the ulnar nerve, as well as its prevalence in both symptomatic and asymptomatic patients is still unclear. This study aimed to assess the prevalence of the AE in a large cohort using 3-dimensional imaging and to investigate any association of the AE with preoperative or postoperative features of patients undergoing cubital tunnel surgery.

From a database of 1240 elbow magnetic resonance imagings, all patients with an AE were retrospectively screened for major criteria of cubital tunnel syndrome. A matching cohort without AE was then similarly assessed to deduct the prevalence of AE and evaluate potential correlations. Next, 344 ulnar nerve surgeries were reviewed. Data including pre- and postoperative physical exam findings, electromyographic study results, reason for compression or (sub)luxation, presence of AE, time to improvement, and need for reoperations were collected. The prevalence of AE in the symptomatic population was determined and possible associations were explored.

The overall prevalence of AE in the population, based on magnetic resonance imaging data, was 5.9%, which closely matched the 5.8% prevalence observed in the operative population. Among the AE group of 13 patients, all were treated with myotomy and in situ decompression during surgery. No higher reoperation rate was seen in the AE group compared to the non-AE group.

The contribution of the AE to the compression neuropathy or protection of the ulnar nerve could not be discerned for the standard population. Therefore, in the routine practice, the AE should be considered as a rare and nonpathological anatomical variant, devoid of any surgical implications.