Accessory Abductor Digiti Minimi Research Articles

Uncommon Anatomical Causes of Ulnar Compression: A Narrative Review.

Some patients develop ulnar nerve compression due to rare anatomical variations or malformations. The aims of this review are to provide a comprehensive overview of anatomical structures and variations that can cause ulnar nerve compression and to evaluate treatment options. Case reports and case series about rare cases of unusual ulnar nerve compression published from January 2000 until April 2022 were obtained from databases Embase, MEDLINE, and Web of Science. A total of 48 studies describing 64 patients were included in our study. The following structures have proven to cause ulnar nerve compression: anconeus epitrochlearis, accessory abductor digiti minimi, vascular anomalies, palmaris longus, fibrous bands, and flexor carpi ulnaris. All cases except one have had a surgical release of the ulnar nerve resulting in diminished symptoms or complete recovery at follow-up. In addition to considering common compression points, it is important to be aware that proximal compression symptoms, such as pain and a positive Tinel sign at the medial elbow, may be attributed to a hypertrophic AE or vascular anomaly. Distal compression symptoms encompass swelling, along with pain and a positive Tinel sign at the distal forearm. Various structures contributing to distal compression include an accessory abductor digiti minimi muscle, an accessory or anomalous palmaris longus muscle, or an accessory or hypertrophic flexor carpi ulnaris muscle. The occurrence of fibrous bands exhibits variability, manifesting in diverse locations across the arm.Level of Evidence: IV.

Presence of accessory abductor digiti minimi muscle in two cadavers.

During routine cadaveric dissection, accessory hypothenar muscles were incidentally discovered in two cadavers, both males, aged 86 and 92. Both muscles originated from the palmaris longus tendon in the distal portion of the forearm and were identified as accessory abductor digiti minimi (AADM) muscles, based on their association with abductor digiti minimi. While AADM is a common variant in the antebrachium, it is less typical for them to originate from the palmaris longus tendon. The presence of such an AADM could complicate surgical procedures requiring resection of the palmaris longus tendon. Moreover, the surrounding neurovasculature - namely the ulnar nerve as it passes through the ulnar canal between the pisiform and hook of the hamate - could be compressed by contractions of an AADM with such a proximal origin. This can manifest as ulnar neuropathies resulting in pain, weakness, or protracted flexion of the fourth and fifth digits (ulnar claw). Our description of these muscles adds to previous accounts of variation of the palmaris longus and abductor digiti minimi muscles while considering potential clinical implications.

Accessory abductor digiti minimi muscle, less muscular than thought: an update on prevalence, morphology, and review of the literature.

To update the prevalence and morphology of the accessory abductor digiti minimi muscle using 3T MRI. A retrospective study of 3T wrist MRI was performed. Presence and morphology of the accessory abductor digiti minimi were evaluated in addition to its relationship to the ulnar nerve. Charts were reviewed for demographics, EMG, neuropathic symptoms, and initial MRI interpretation. Analysis of 396 wrist MRI studies yielded 25% prevalence of the accessory abductor digiti minimi, of which the majority (69%) demonstrated fascial-type morphology proximal to Guyon's canal. A minority (31%) demonstrated a contiguous muscle belly throughout its course. Overall, prevalence of a muscular type was only 8%. All patients were asymptomatic with normal EMG, unremarkable ulnar nerve, and no significant nerve compression. Anterior-posterior muscle dimension was larger in males. Only 1 of 98 accessory abductor digiti minimi muscles was prospectively identified. The accessory abductor digiti minimi is not uncommon; however, patients are usually asymptomatic without neuropathic symptoms. The most common anatomic variant is a small muscle belly at the level of the pisiform with fascial morphology proximal to Guyon's canal and origin from the distal antebrachial fascia. A contiguous muscle belly extending from the distal forearm through the wrist occurs much less frequently. Clinicians should be familiar with these anatomic variants to enhance its recognition, understanding that a muscular variant is rarer than previously reported, but historically can serve as a potential source of clinical symptomatology and could be encountered during physical examination or wrist surgery.

A Cadaveric Study on Variations of Branching Patterns of Ulnar Nerve in Hand

Introduction: Anatomical knowledge of variations in the branching patterns of ulnar nerve in hand is very important for the surgeons in diagnosis of peripheral neuropathies and in treating nerve compression syndromes. In addition, knowledge of relationship between deep branch of ulnar nerve and deep palmar arch is important in treating ulnar nerve compression due to post-traumatic pseudo aneurysm, true aneurysm of distal ulnar artery or tortuous ulnar artery. Aim: To observe the division of ulnar nerve in relation to flexor retinaculum, the variations in the branching patterns of ulnar nerve in hand and the relation between deep branch of ulnar nerve and deep palmar arch. Materials and Methods: An observational study was conducted in 52 cadaveric hands collected from Department of Anatomy, Chettinad Hospital and Research Institute from August 2013 to Dec 2013. Specimens were fixed in 10% of formalin and dissected. Observations were noted. Results: Division of ulnar nerve into superficial and deep branch was seen along the middle part of flexor retinaculum in 15 (28.8%) out of 52 specimens. In 5 (9.6%) out of 52 specimens, this division was seen in the distal part of flexor retinaculum. Trunk of ulnar nerve supplying abductor digiti minimi was seen in 5 (9.6%) specimens and accessory abductor digiti minimi in 3 (5.7%) specimens. Superficial branch of ulnar nerve supplying abductor digiti minimi in five specimens and flexor digiti minimi in three specimens. Deep branch of ulnar nerve was seen along the concavity of deep palmar arch in 15 (28.8%) specimens and along the convexity in 23 (44.2%) specimens. In 14 (26.9%) specimens, deep branch of ulnar nerve was seen crossing the deep palmar arch superficially from proximal to distal. Conclusion: Ulnar nerve presents with many variations in the hand. These variations may lead to entrapment neuropathies which will have varied presentations. Knowledge of these variations will help the general surgeons, orthopedic surgeons and plastic surgeons during various surgical corrections.

Guyon's Canal Syndrome Caused by an Accessory Abductor Digiti Minimi Muscle

Guyon's Canal Syndrome Caused by an Accessory Abductor Digiti Minimi Muscle

An Accessory Abductor Digiti Minimi as Possible Risk Factor of the Median and Ulnar Nerves Compression

During routine dissection of a left upper limb of a 68-year-old male human cadaver, an unusual muscle was observed originating from the radius and flexor retinaculum, and continued in the hypothenar region with the muscle belly of the abductor digiti minimi. We checked that it was an accessory abductor digiti minimi (ADM). Its muscular belly was in close relation to the median and ulnar nerves. We review the literature regarding such muscle variations and discuss the potential for compression of the median and ulnar nerves. Although the accessory ADM is usually asymptomatic and only rarely results in nerve compression, it should be taken into account by surgeons when establishing a differential diagnosis in the compression neuropathies of the median and ulnar nerves. An ultrasound scanning can help establish the differential diagnosis.

Compression Neuropathy of the Ulnar Nerve due to the Accessory Abductor Digiti Minimi at Guyon’s Canal: A Case Report

Guyon’s canal syndrome is a compression neuropathy of the ulnar nerve that occurs at the wrist. Compression can be caused by many conditions, such as benign tumors, repeated occupational trauma, vascular lesions, fractures of the carpal bones, rheumatoid arthritis and anomalous hypothenar muscle at Guyon's canal. Here, the authors report a case of compression neuropathy of the ulnar nerve by the accessory abductor digiti minimi muscle (AADM), one of the anomalous hypothenar muscles, at Guyon's canal. The case report is accompanied by a literature review.

Ulnar nerve compression by accessory abductor digiti minimi muscle

We report two cases of accessory abductor digiti minimi muscle causing ulnar nerve compression at the Guyon’s canal. One case had venous malformations on the palm with gangrenous left little finger terminal phalanx. Excision of the abnormal muscle relieved patient symptoms. Though the abnormal muscle is reported in literature, the number of symptomatic clinical cases due to muscle compression is rare. The diagnosis itself might be missed because of lack of awareness.

Topographic anatomy of the ulnar tunnel.

The aim of this study was to clarify the definition of the anterior wall of the ulnar tunnel and to reveal the topographical characteristics of the various components of the ulnar tunnel. Twenty-two forearms from 11 embalmed cadavers (7 males, 4 females; mean age, 67.8 years) were carefully dissected. In all cases, the anterior wall of the ulnar tunnel comprised the hypothenar fascia, which originated from the tendon of the flexor carpi ulnaris muscle. The palmar carpal ligament, the distal extent of the antebrachial fascia, was located deep to the anterior wall and formed only the anterior boundary of the proximal hiatus of the ulnar tunnel. The hypothenar fascia was attached to the flexor retinaculum at 15.2 mm lateral to the pisiform bone. However, the palmar carpal ligament was attached to the flexor retinaculum just lateral to the ulnar artery; the distance between the attachment of the palmar carpal ligament and the pisiform bone was 8.7 mm. Anatomical variations potentially associated with ulnar nerve compression were observed. The accessory abductor digiti minimi muscle and the fibrous band crossing the ulnar nerve in the ulnar tunnel were found in 27 and 23 % of forearms, respectively. A more detailed description of the anterior wall of the ulnar tunnel than was previously available is presented herein, and topographic and metric data regarding each structure of the tunnel are reported.

A morphometric study of the ulnar nerve in Guyon's canal

Objectives:Guyon’s canal is clinically significant because it contains the ulnar nerve, artery and veins and is a location forcompression injury. This study was undertaken to determine the anatomy of the ulnar nerve in Guyon’s canal on 40 wristsof 20 adult formalin-fixed cadavers. Methods: 40 wrists of 20 formalin-fixed adult cadavers obtained from the Department of Anatomy, Ege University Facultyof Medicine were dissected. In each cadaver, the skin and the subcutaneous fatty tissues were removed starting from theforearm down to the palm of the hand. The palmaris brevis muscle and the palmar aponeurosis were dissected to exposeGuyon’s canal. Results: The length and diameter of the main trunk of the ulnar nerve in Guyon’s canal before dividing into its terminalbranches were measured as 11.72±1.99 mm and 3.41±0.5 mm, consequently. Within the canal, the main trunk divided intotwo terminal branches. The diameter of the deep branch was 1.77±0.47 mm and the superficial branch was 2.41±0.45 mm.The superficial branch divided into the proper palmar digital nerve supplying the medial side of the little finger and the common palmar digital nerve supplying the adjoining sides of little and ring fingers. Conclusion:An accessory abductor digiti minimi muscle was observed as a possible cause of compression in Guyon’s canal.Despite its clinical relevance, the diameters of the deep and superficial branches of the ulnar nerve in Guyon’s canal do notexist in previous studies

Possible implications of an accessory abductor digiti minimi muscle: a case report

BackgroundAccessory ADM was first reported in 1868 although muscular, vascular and nervous variations of the hypothenar eminence are rare, contrary to anomalous muscles in the wrist which are relatively common.Case presentationThis case report presents a bilateral variation of an accessory abductor digiti minimi muscle in a male specimen. Ulnar artery and ulnar nerves were taken into account regarding their position and trajectory related to this variation.ConclusionMuscle size may be an important factor in considering whether a variation is able to produce neurovascular compression and clinical implications.

Unusual Co-existence of Biaponeurotic Palmaris Longus and Accessory Abductor Digiti Minimi in man

The present study describes a rarely reported co-existence of variant muscles in the right upper limb of a male cadaver of 57 years of age, observed during routine anatomical dissection. There was a presence of the biaponeurotic palmaris longus with a central muscle belly in the anterior forearm region which was closely related to the median nerve. In addition to this, an accessory abductor digiti minimi muscle was also reported in the corresponding hypothenar region, traversing the Guyon's canal, passing superficial to the ulnar vessels and nerves. Biaponeurotic palmaris longus and accessory abductor digiti minimi are important structural causes of the entrapment neuropathies of forearm and wrist. Diagnosis of these muscles as a cause of entrapment neuropathies requires the sound knowledge of variant muscles in the forearm and wrist region.

An Anatomic Variation of the Accessory Abductor Digiti Minimi Muscle

Accessory muscles passing through Guyon’s canal are common; the most common anomalous muscle at Guyon’s canal is the accessory abductor digiti minimi muscle (AADM). The aim of this study was to demonstrate and describe the gross anatomy of an anatomic variant of the AADM relative to the surrounding structures. The AADM was found in the left forearm and hand of a 61-year-old male cadaver during dissection in a gross anatomy course. It was observed by focusing on the shape, the course, and its relationship with the surrounding structures. The AADM originated as muscle fibers from the antebrachial fascia. It coursed downward in the distal forearm and crossed the ulnar nerve and artery obliquely at Guyon’s canal. The AADM narrowed and became a long tendon in the hypothenar region. The abductor digiti minimi muscle was partly attached to the tendon of the AADM, running along the tendon. The tendon of the AADM inserted into the ulnar side of head of the fifth metacarpal bone. The AADM was innervated by several twigs from the ulnar nerve. We reported herein another variant of the AADM at Guyon’s canal, which may be helpful to surgeons performing diagnoses and surgical procedures.

Atypical ulnar tunnel syndrome accompanied by sensory disturbance of the dorsal sensory branch of the ulnar nerve

An atypical accessory abductor digiti minimi, which is morphologically a bicipital muscle, was the cause of the ulnar tunnel syndrome. A ganglion grew from the volar carpal joint at the same time and caused sensory disturbance of the dorsal sensory branch of the ulnar nerve.

New Insight Into the Enigmatic White Cord in Rembrandt’s The Anatomy Lesson of Dr. Nicolaes Tulp (1632)

The anatomic accuracy of Rembrandt's The Anatomy Lesson of Dr. Nicolaes Tulp (1632) has been debated in the literature for many years. The white cord that courses along the ulnar aspect of the carpus and small finger of the cadaver in Dr. Tulp's dissection conforms to no normal anatomic structure and is believed to represent an anomalous branch of the ulnar nerve, an artistic error, or a combination of both. After the discovery of an accessory abductor digiti minimi (AADM) during a routine dissection of a late-middle-aged male cadaver, we noted that the course of its tendon over the hypothenar eminence resembled the white cord in the painting. After conducting a detailed literature search and anatomic interpretation of the painting, we established 4 criteria for identifying the white cord. Using these criteria, we evaluated the plausibility of an AADM being represented in the painting. We conclude that an AADM should be considered as a possible explanation for the white cord.

Accessory abductor digiti minimi muscle causing ulnar nerve entrapment at the Guyon's canal: A case report

Accessory abductor digiti minimi muscle causing ulnar nerve entrapment at the Guyon's canal: A case report

Entrapment of the Ulnar Nerve at Guyon??s Canal by an Accessory Abductor Digiti Minimi Muscle

Department of General Surgery, Division of Plastic and Reconstructive Surgery, Wayne State University, Detroit, Mich. Correspondence to Dr. Spiess, Department of General Surgery, Division of Plastic and Reconstructive Surgery, Wayne State University, Harper Professional Building, Suite 400, 4160 John R Street, Detroit, Mich. 48201, [email protected]

Ulnar nerve compression at the wrist by the accessory abductor digiti minimi muscle: wrist trauma as a precipitating factor.

This paper describes four cases of ulnar tunnel compression syndrome caused by the accessory abductor digiti minimi muscle and stresses on the observation that wrist trauma could be an important precipitating factor. Possible pathophysiological explanations of this phenomenon are offered and the anatomy of the accessory abductor digiti minimi muscle is reviewed.

MR demonstration of anomalous muscles about the volar aspect of the wrist and forearm

Magnetic resonance (MR) examination of 42 normal wrists was performed for evaluation of anomalous musculature. A total of 23 muscle variations were found. An accessory abductor digiti minimi was found in 10 wrists (24%), an absent palmaris longus was found in seven wrists (16%), a muscular palmaris longus tendon was found in three wrists (7%), a muscular flexor digitorum superficialis was found in two wrists (5%), and an aberrant lumbrical muscle originating from within the carpal tunnel was found in one wrist (2.4%). Such muscle variations can be distinguished by MR from other mass lesions at the wrist and a knowledge of their frequency, appearance, and location can be of help in this regard.

Ulnar nerve compression by an accessory abductor digiti minimi muscle presenting following injury

Ulnar nerve compression by an accessory abductor digiti minimi muscle presenting following injury