Anconeus epitrochlearis – prevalence and clinical manifestations

Introduction and Objective. Anconeus epitrochlearis (AE) is an anomalous accessory muscle discovered in 1865. It arises from the vmedial epicondyle of the humerus to the olecranon of the ulna. Its appearance is the result of evolution and has benefits as well as deficits that can be harmful. It is believed that if anconeus trochlearis is present, it replaces the Osborne’s ligament. The muscle is most commonly detected incidentally during the diagnosis of cubital tunnel syndrome (CuTS). The aim of the study is to review papers on the prevalence of AE, symptoms resulting from its presence, and conclusions drawn from available sources on PubMed. Review Methods. The review is based on 14 papers found in PubMed and PubMedCentral databases after searching for ‘anconeus epitrochlearis’, ‘anconeus epitrochlearis’ and ‘cubital tunnel syndrome’ published between 1874–2023. Brief description of the state of knowledge. Prevalence varies across different types of studies aimed at identifying anconeus epitrochlearis: 8.1%–23% for MRI studies, 4.5%–8.5% for operative reports, and 5.4%-26.5% for cadaveric studies. The mere presence of AE usually does not cause any symptoms. If the presence of anconeus epitrochlearis is symptomatic, patients complain of numbness in the fourth and fifth fingers of the hand and weakness of thenar muscle, which are symptoms of cubital tunnel syndrome (CuTS). Summary. It is likely that AE alone does not cause cubital tunnel syndrome which occurs only when anconeus epitrochlearis undergoes hypertrophy, dispelling doubts about whether the mere presence of the muscle is synonymous with the development of cubital tunnel syndrome. A higher percentage of CuTS was reported in the dominant hand of individuals who had the AE in that limb. Cubital tunnel syndrome caused by the AE is a favourable factor for treatment and post-operative regeneration.