Anconeus epitrochlearis muscle causing dynamic cubital tunnel syndrome: a case series

The anatomical variations of the cubital tunnel in a South African body donor sample

PURPOSE

The ulnar nerve (UN) courses through the cubital tunnel, which is a potential site of entrapment. Anatomical variations of the cubital tunnel may contribute towards cubital tunnel syndrome (CuTS), however, these are not well described. The aim was to compare the range of variations and dimensions of the cubital tunnel and the UN between sexes and sides of the body.

METHODS

Sixty elbows from 30 embalmed bodies (17 males and 13 females) were dissected. The prevalence of the cubital tunnel retinaculum (CuTR) or anconeus epitrochlearis (AE) forming the roof of the tunnel was determined. The length, width, thickness, and diameter of the cubital tunnel and its roof were measured. The diameter of the UN was measured.

RESULTS

The AE was present in 5%, whereas the CuTR was present in the remaining 95% of elbows. The tunnel was 32.1 ± 4.8 mm long, 23.4 ± 14.2 mm wide, 0.18 ± (0.22-0.14) mm thick, and the median diameter was 7.9 ± (9.0-7.1) mm, while the median diameter of the UN was 1.6 ± (1.8-1.3) mm. The AE was thicker than the CuTR (p < 0.001) and the UN was larger in elbows with the AE present (p = 0.002). The tunnel was longer in males (p < 0.001) and wider on the right (p = 0.014).

CONCLUSION

The roof of the cubital tunnel was more frequently composed of the CuTR. The cubital tunnel varied in size between sexes and sides. Future research should investigate the effect of the variations in patients with CuTS.

Anconeus epitrochlearis muscle resulting in cubital nerve compressive neuropathy: Two case reports

Background

The anconeus epitrochlearis muscle is an anatomical variant prevalent in amphibians but unusual in humans. In favorable cases, this muscle provides protection to the cubital nerve but can result in neuropathy due to compression of the cubital nerve.

Case Description

We present two cases with different clinical manifestations but both did not respond to conservative treatment. We opted for a surgical decompression where the anconeus epitrochlearis muscle was found intraoperatively, and the muscle fibers were dissected.

Conclusion

Considering the presence of the muscle variant is the key point to intraoperatively achieve a complete dissection of the muscle fibers of the anconeus epitrochlearis muscle variant and obtain the decompression of the cubital nerve with satisfactory postoperative results.

Dynamic Compression of the Ulnar Nerve Associated With the Anconeus Epitrochlearis Muscle: Do We Really Know Everything?

Ulnar nerve compression associated with the anconeus epitrochlearis muscle (AE) is an uncommon cause of peripheral nerve compression at the elbow. It is often seen in young women with a hypertrophied or severely edematous muscle. Its causes are unclear. Numerous observed features, such as a hypertrophic AE, a palpable mass on the medial side of the elbow, and the dynamic nature of symptoms, have sparked controversy in the literature. Its clinical presentation is often insidious, and occasionally symptoms only occur in prolonged positions (dynamic compression). EMG tests are usually negative, and a correct diagnosis relies on imaging. We present the case of a 21-year-old student and clarinet player who presented with dynamic compression of the ulnar nerve at the elbow associated with AE. Much remains to be elucidated about the incidence, pathophysiology, and contributing factors of this peripheral form of cubital compression. It may be time to revisit this condition.

Clinical Application of Anomalous Muscles for Tendon Transfer in the Upper Limb: A Systematic Review of the Literature

Numerous anomalous muscles of the forearm and hand have been reported in the literature. The majority were encountered in cadaver dissections and some were incidentally detected during tendon transfer surgery. Because of the limited number of motors available for transfer, it may be advantageous if an anomalous muscle with favorable anatomy can function as a potential donor in a suitable clinical environment. Although several authors have illustrated various anomalies and their functional significance, the reports of actual utilization of such muscles as donors for tendon reconstructions are sparse. The aim of the study is to conduct a systematic review of the clinical applications of anomalous muscles in the upper extremity. After a thorough search of PubMed, Web of Science, Scopus, and Cochrane Library databases, only three out of 106 studies were found to be relevant. Two of them discussed the anomalous radial wrist extensor tendon transfer for thumb flexion. The third study described the usage of anomalous flexor carpi ulnaris (FCU) for thumb opposition and index finger flexion, and also proposed a classification. This is the first systematic review of the clinical application of anomalous muscles as donors in the upper extremity tendon transfer surgical procedures. Knowledge of the above classification helps in intraoperative evaluation of the type of the anomaly and the possible consideration of anomalous muscle as a source of transplant material in an appropriate clinical setting.

Prevalence and Clinical Manifestations of the Anconeus Epitrochlearis and Cubital Tunnel Syndrome

Background: The true prevalence of the anconeus epitrochlearis (AE) and the natural history of cubital tunnel syndrome associated with this anomalous muscle are unknown. The purpose of this study was to evaluate the prevalence of AE and to characterize the preoperative and postoperative features of cubital tunnel syndrome caused by compression from an AE. Methods: All elbow magnetic resonance imaging (MRI) scans and all patients undergoing cubital tunnel surgery during a 20-year period were identified and retrospectively reviewed for the presence of an AE. All patients with an AE identified intra-operatively were matched to patients with no AE identified at surgery based on age, sex, concomitant procedures, and year of surgery. Preoperative and postoperative physical exam findings, electrodiagnostic study results, time to improvement, and reoperations were compared between the groups. Results: A total of 199 patients had an elbow MRI, and 27 (13.6%) patients were noted to have an AE present. Average time to improvement after surgical release was 23.0 days for patients with an AE and 33.2 days for patients with no AE. Twenty-seven patients with an AE noted improvement at the first postoperative visit (68%) compared to 15 patients without an AE (33%). No patients with an AE underwent reoperation for recurrent symptoms (0%) compared with four patients (10%) without an AE. Conclusions: The prevalence of AE in our study is 13.6%. These patients experience quicker and more reliable symptom improvement after surgical release than those without the anomalous muscle.

Ulnar Nerve Compression due to Anconeus Epitrochlearis: A Case Report and Review of the Literature

CASE

A 32-year-old right-handed surgeon presented with a history of intermittent pain at the right medial epicondyle, a mild Tinel's sign, and dysesthesia in the ulnar nerve distribution. Dynamic ultrasound demonstrated a hypertrophic anconeus epitrochlearis bilaterally, and chronic irritation of the ulnar nerve. Anterior release with myectomy of the accessory muscle was performed. No compressive symptoms were present at 1-year follow-up.

CONCLUSIONS

The anconeus epitrochlearis is an often-underappreciated cause of ulnar nerve compression that can lead to significant functional impairment. Dynamic ultrasound is an excellent diagnostic modality, and anterior release with myectomy provides durable relief with minimal downtime.

Performance and Return to Sport After Ulnar Nerve Decompression/Transposition Among Professional Baseball Players

BACKGROUND

Isolated ulnar nerve decompression/transposition is an uncommon surgical procedure among professional baseball players.

PURPOSE/HYPOTHESIS

To determine performance and rate of return to sport (RTS) among professional baseball players after isolated ulnar nerve decompression/transposition, including those who required decompression/transposition after ulnar collateral ligament reconstruction (UCLR), and to compare outcomes between cases and matched controls. The authors hypothesized a high rate of RTS among professional baseball players undergoing isolated ulnar nerve decompression/transposition with no difference in RTS rate or performance between cases and controls as related to earned run average, WHIP ([walks + hits]/innings pitched), wins above replacement, and on base + slugging percentage.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Utilizing the injury database of Major League Baseball, we identified all professional baseball players who underwent isolated ulnar nerve decompression/transposition between 2010 and 2016. De-identified demographic and performance data (before and after surgery) for each player were recorded from Major League Baseball records. Performance metrics were then compared between cases and matched controls.

RESULTS

The study included 52 players; 83% were pitchers; and 14 underwent prior UCLR. Most surgical procedures (92%) were anterior subcutaneous transpositions. Overall, 62% of players were able to successfully RTS, and 56% returned to the same or higher level. There was no significant difference between cases and controls in the majority of pre- and postoperative performance metrics-specifically, earned run average, WHIP, wins above replacement, and on base + slugging percentage. When players who had UCLR before ulnar nerve decompression/transposition were compared with controls with a history of UCLR but no subsequent ulnar nerve decompression/transposition, the only performance difference of all the recorded metrics was that cases allowed more walks per 9 innings (4.4 vs 2.8, P = .011).

CONCLUSION

Anterior subcutaneous transposition is the most common surgical procedure among professional baseball players to address ulnar neuropathy at the elbow. Players have a 62% rate of RTS, which is lower than expected for this nonreconstruction or repair procedure. For players who successfully RTS, performance metrics versus matched controls remained the same except for allowing significantly more walks per 9 innings. Postoperatively, pitchers with UCLR before ulnar nerve decompression/transposition who had a successful RTS performed the same as matched controls with prior UCLR without subsequent ulnar nerve decompression/transposition.

Etiology, Diagnosis, and Treatment of Dynamic Nerve Compression Syndromes of the Elbow Among High-Level Pitchers: A Review of 7 Cases

Background:

Dynamic compressive neuropathies around the elbow are a rare entity described by a relatively small body of literature, mostly consisting of single-case reports. No standardized diagnostic protocols have been described to date. To the authors’ knowledge, this study represents the largest case series of dynamic compressive neuropathies in the upper extremity.

Purpose:

To identify various etiologies of dynamic compressive neuropathies around the elbow, devise a systematic diagnostic protocol, and review treatment options.

Study Design:

Case series; Level of evidence, 4.

Methods:

A retrospective review was conducted of patients who presented to a single practice between 2013 and 2017 and were diagnosed with a dynamic compressive neuropathy around the elbow.

Results:

A total of 7 patients were identified, with a mean follow-up of 2 years. All patients were high-level pitchers. One patient was a minor league pitcher; 4 patients were National Collegiate Athletic Association athletes; and 2 patients were high school athletes. All patients underwent a systematic diagnostic workup. The diagnosis was established with dynamic nerve conduction testing. Three etiologies for dynamic nerve compression around the elbow were identified: 1 case of lateral antebrachial cutaneous nerve compression by the biceps tendon, 3 cases of ulnar nerve compression by an anconeus epitrochlearis muscle, and 3 cases of posterior interosseous nerve compression at the arcade of Frohse with hypertrophic extensor carpi radialis brevis and extensor digitorum communis muscles. Two patients were treated conservatively, while 5 patients required surgery. All patients were able to return to pitching.

Conclusion:

Dynamic compressive neuropathies around the elbow are rare entities that present unique diagnostic challenges to the treating clinician. In this cohort, all patients were young throwing athletes. Physical examination of the patient frequently lacks typical findings of chronic nerve entrapment syndromes. Dynamic nerve conduction studies establish the diagnosis, and treatment often requires surgical decompression to achieve complete resolution of symptoms.

Cubital Tunnel Syndrome Caused by Anconeus Epitrochlearis Muscle

Objective

We evaluated the clinical manifestation and surgical results following operative treatment of cubital tunnel syndrome (CuTS) caused by anconeus epitrochlearis (AE) muscle.

Methods

Among 142 patients who underwent surgery for CuTS from November 2007 to October 2015, 12 were assigned to the AE group based on discovery of AE muscle; 130 patients were assigned to the other group. We analyzed retrospectively; age, sex, dominant hand, symptom duration, and weakness in hand. Severity of the disease was evaluated using the Dellon classification and postoperative symptom were evaluated using disability of arm shoulder and hand (DASH) and visual analogue scale (VAS) scores. Surgery consisted of subfascial anterior transposition following excision of AE muscle.

Results

AE muscle was present in 8.5% of all patients, and was more common in patients who were younger and with involvement of their dominant hand; the duration of symptom was shorter in patients with AE muscle. All patients showed postoperative improvement in symptoms according to DASH and VAS scores.

Conclusion

The possibility of CuTS caused by AE muscle should be considered when younger patients have rapidly aggravated and activity-related cubital tunnel symptoms with a palpable mass in the cubital tunnel area. Excision of AE muscle and anterior ulnar nerve transposition may be considered effective surgical treatment.

Anomalous Forearm Muscles and Their Clinical Relevance

Despite their relatively low prevalence in the population, anomalous muscles of the forearm may be encountered by nearly all hand and wrist surgeons over the course of their careers. We discuss 6 of the more common anomalous muscles encountered by hand surgeons: the aberrant palmaris longus, anconeus epitrochlearis, palmaris profundus, flexor carpi radialis brevis, accessory head of the flexor pollicis longus, and the anomalous radial wrist extensors. We describe the epidemiology, anatomy, presentation, diagnosis, and treatment of patients presenting with an anomalous muscle. Each muscle often has multiple variations or subtypes. The presence of most anomalous muscles is difficult to diagnose based on patient history and examination alone, given that symptoms may overlap with more common pathologies. Definitive diagnosis typically requires soft tissue imaging or surgical exploration. When an anomalous muscle is present and symptomatic, it often requires surgical excision for symptom resolution.