Prevalence and Clinical Manifestations of the Anconeus Epitrochlearis and Cubital Tunnel Syndrome
Jed Ian Maslow, MD; Mihir J. Desai, MD; Daniel J Johnson, BS; John Jake Block, MD; Donald H. Lee, MD
Vanderbilt University Medical Center, Nashville, TN
Compressive neuropathy of the upper extremity is a common cause of lost work, disability, and chronic pain. CubitalTunnel Syndromecan be caused bymultiple static and dynamic factors that can be difficult to diagnose pre-operatively.Cubital Tunnel Syndrome leads to significant morbidity and days or work lost after treatment. We hypothesize that Cubital Tunnel Syndrome secondary to compression by the anconeus epitrochlearis (AE) more commonly presents with negative electrodiagnostic studies and has a predictable, rapid recovery after surgical release.
MATERIALS AND METHODS
All elbow MRI scans performed from 1996 through 2016 at one institution were retrospectively reviewed for the presence of an AE by a musculoskeletal fellowship trained radiologist and correlated to physical exam. All patients undergoing cubital tunnel release with or without transposition during the same time period were identified. A total of 40 patients had an AE identified intra-operatively. Forty patients with no AE identified at surgery were then matched for age, sex, concomitant procedures, and year of surgery. Descriptive statistics were used to analyze outcome measures including pre- and postoperative medial elbow pain, sensory changes, atrophy, Tinel's sign, elbow flexion test, and electrodiagnostic studies. Time to improvement (days) and number of reoperations were noted and compared.
A total of 199 patients had an elbow MRI performed and 27 (13.6%) patients were noted to have an AE present. In patients undergoing cubital tunnel release, 20 of the 40 with an AE identified during surgery had negative preoperative electrodiagnostic studies compared to 11 matched controls without an AE (p<0.05). Four patients without an AE had a reoperation for recurrent symptoms and no patients with an AE underwent reoperation (p<0.05). Average time to improvement after surgical release was 21.2 days for patients with an AE and 31.9 days for patients with no AE (p<0.05). Twenty-seven patients with an AE noted improvement at the first post-operative visit (67.5%) compared to 15 patients without AE (32.5%, p<0.05).
The prevalence of AE in our study is 13.6%. This is the largest series of elbows reviewed. Pre-operative electromyography and nerve conduction studies are more frequently nondiagnostic in patients with an AE and Cubital Tunnel Syndrome. Patients with an AE experience quicker symptom improvement after cubital tunnel release than those without the anomalous muscle.
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