Anomalies of the flexor digitorum superficialis muscle

Unusual Duplication of Flexor Tendons in the Middle Finger Leading to Trigger Finger: A Case Report and Comprehensive Review

Duplication of the flexor digitorum profundus (FDP) tendon is an extremely uncommon anatomical anomaly found within the flexor digitorum superficialis (FDS) muscle, with minimal documentation in the current literature. We present the case of a 45-year-old female manual laborer who exhibited symptoms suggestive of trigger finger in her right middle finger. Surgical exploration uncovered a duplicated FDP tendon, a previously unreported anatomical anomaly in this context. Despite attempting conservative treatment initially, surgical intervention involving release of the A1 pulley, excision of the A1 pulley, and identification of the duplicated tendon was performed. The unusual nature of this anatomical variation highlights the need for additional research into its clinical significance and treatment options. This case highlights the significance of conducting comprehensive anatomical assessments to diagnose and treat uncommon variations within the FDS muscle. It underscores the continued need for collaborative research to enhance treatment approaches, especially in instances where trigger finger symptoms are present.

MRI-Based Evaluation of the Flexor Digitorum Superficialis Anatomy: Investigating the Prevalence and Morphometry of the "Chiasma Antebrachii"

Recent dissection studies resulted in the introduction of the term "chiasma antebrachii", which represents an intersection of the flexor digitorum superficialis (FDS) tendons for digits 2 and 3 in the distal third of the forearm. This retrospective investigation aimed to provide an MRI-based morphologic analysis of the chiasma antebrachii. In 89 patients (41 women, 39.3 ± 21.3 years), MRI examinations of the forearm (2010-2021) were reviewed by two radiologists, who evaluated all studies for the presence and length of the chiasma as well as its distance from the distal radioulnar and elbow joint. The chiasma antebrachii was identified in the distal third of the forearm in 88 patients (98.9%), while one intersection was located more proximally in the middle part. The chiasma had a median length of 28 mm (interquartile range: 24-35 mm). Its distances to the distal radioulnar and elbow joint were 16 mm (8-25 mm) and 215 mm (187-227 mm), respectively. T1-weighted post-contrast sequences were found to be superior to T2- or proton-density-weighted sequences in 71 cases (79.8%). To conclude, the chiasma antebrachii is part of the standard FDS anatomy. Knowledge of its morphology is important, e.g., in targeted injections of therapeutics or reconstructive surgery.

Imaging of Anatomical Variants Around the Wrist and Hand

Wrist and hand anatomy may present several clinically relevant variants that involve bones, muscles, tendons, and nerves. Thorough knowledge of these abnormalities and their appearance in imaging studies is useful for proper management. In particular, it is necessary to differentiate the incidental findings that do not represent a trigger for a specific syndrome from those anomalies causing symptoms and functional impairment. This review reports the most common anatomical variants encountered in clinical practice and briefly discusses their embryogenesis, related clinical syndrome if present, and their appearance using different imaging techniques. The information each diagnostic study (ultrasonography, radiographs, computed tomography, and magnetic resonance imaging) may provide is described for each condition.

Unilateral Right-Sided Progressive Flexor Digitorum Superficialis Brevis to the Little Finger: A Case Report With Review of Literature

The flexor digitorum superficialis (FDS), an intermediate flexor of the forearm, can present with variations in the musculature or tendons. Here, we report a very rare anomaly of the FDS-V tendon replaced by a muscle belly in the palm, which was a progressive variation. This variation was found in a 60-year-old female cadaver on the right hand. The anomalous belly took its origin from the center of the volar aspect of the flexor retinaculum and was inserted into the A2 pulley of the middle interphalangeal joint to the little finger. The anomalous muscle was innervated by a branch of the median nerve. Knowledge of such variations will be useful for hand surgeons for meticulous planning of surgeries of the palm. The occurrences of such variations might interfere with the biomechanics of the FDS tendons.

An Analysis of Profundus Tendon Repairs After Distal Phalanx Amputation in a Cadaveric Model of Little Finger Superficialis Deficiency

PURPOSE

The flexor digitorum superficialis tendon to the little finger (FDS-5) has been observed to have a higher degree of functional and structural variation than the FDS of other digits. FDS-5-deficient individuals necessarily rely on the flexor digitorum profundus tendon to the little finger (FDP-5) for flexion in their little fingers. FDS-5 deficient patients who experience a considerable injury to their FDP-5 are therefore at a risk of losing substantial little finger flexion. The purpose of this study was to evaluate the degree of flexion of the little finger at the metacarpophalangeal and proximal interphalangeal (PIP) joints in a cadaveric model of FDS-5 deficiency following amputation of the distal phalanx.

METHODS

Ten fresh-frozen cadaveric upper extremities with no prior trauma were used. Loads were applied to the FDP-5. Flexion at the PIP and metacarpophalangeal joints was measured in degrees with a goniometer. Little finger flexion testing was conducted under 5 different conditions: "baseline," "FDS-deficient," "no repair," "bone anchor" repair, and "A4 pulley" repair.

RESULTS

The results were as follows: (1) no significant differences in the flexion between baseline and FDS-deficient conditions; (2) a significant decline in PIP flexion in the no repair condition after FDP-5 division compared with the FDS-deficient condition; (3) a significant restoration in PIP flexion in both surgical repair groups compared with the no repair group; and (4) no significant differences in PIP flexion between the A4 pulley and bone anchor groups.

CONCLUSIONS

The bone anchor repair and the A4 pulley repair demonstrate similar abilities to restore flexion of the little finger at the PIP joint to baseline levels in this cadaveric model.

CLINICAL RELEVANCE

A clinical protocol is yet to be established for the surgical treatment in FDS-5-deficient patients requiring amputation of the distal phalanx of the little finger. This study aims to address this area of uncertainty by comparing the little finger flexion after 2 different approaches to profundus tendon reattachment that may be applicable in this clinical scenario.

4D formation of human embryonic forelimb musculature

The size, shape and insertion sites of muscles enable them to carry out their precise functions in moving and supporting the skeleton. Although forelimb anatomy is well described, much less is known about the embryonic events that ensure individual muscles reach their mature form. A description of human forelimb muscle development is needed to understand the events that control normal muscle formation and to identify what events are disrupted in congenital abnormalities in which muscles fail to form normally. We provide a new, 4D anatomical characterisation of the developing human upper limb muscles between Carnegie stages 18 and 22 using optical projection tomography. We show that muscles develop in a progressive wave, from proximal to distal and from superficial to deep. We show that some muscle bundles undergo splitting events to form individual muscles, whereas others translocate to reach their correct position within the forelimb. Finally, we show that palmaris longus fails to form from early in development. Our study reveals the timings of, and suggests mechanisms for, crucial events that enable nascent muscle bundles to reach their mature form and position within the human forelimb.

Prevalence of Absence of Function of the Flexor Digitorum Superficialis Muscle Tendons in the Fourth and Fifth Fingers of the Hand in the Brazilian Population

Objectives  To evaluate the prevalence of absence of flexor digitorum superficialis muscle tendons function of the fourth and fifth fingers of the hand in the Brazilian population

Methods  Prospective study performed at the orthopedics and traumatology department of a university hospital. The study was conducted from October 2017 to April 2018. The sample consisted of volunteers with no history of upper limb trauma, surgery or any other condition. This study included both male and female individuals over 18 years old. The flexor digitorum superficialis muscle tendons of the fourth and fifth fingers were evaluated through clinical tests by three independent examiners. The data were analyzed using GraphPad Prism 5.0 (GraphPad Software, San Diego, CA, USA).

Results  A total of 2,016 hands from 1,008 volunteers were analyzed. The prevalence of absence of flexor digitorum superficialis muscle tendon function of the fourth finger was 0.56% at the right hand and 0.99% at the left hand. At the right hand, this prevalence was higher in females compared to males ( p  = 0.0328). No difference between genders was noted in the left hand ( p  = 0.7562). The prevalence of absence of flexor digitorum superficialis muscle tendon function of the fifth finger was 34.53% in the right hand and 30.06% in the left hand. This prevalence was higher in females compared to males, both at the right hand ( p  = 0.0001) and the left hand ( p  = 0.0003).

Conclusion  Even though there are studies performed separately in different ethnic groups, there were no data in the literature regarding the prevalence of absence of flexor digitorum superficialis muscle tendons function of the fourth and fifth fingers of the hand in a multiethnic population such as the Brazilian one.

The anatomy and function of a bilateral accessory flexor digitorum superficialis muscle: A case report and review of literature

Anatomical variations of the flexor digitorum superficialis (FDS) include variations of the muscle belly and/or tendon. We present a case of a bilateral accessory FDS muscle and tendon. Dissection was performed in a male specimen (56 years), where an unusual variation was found: a bilateral accessory FDS muscle and tendon. The accessory FDS muscle belly originated at the medial epicondyle, between the tendinous portions of the FDS and flexor carpi radialis, with average dimensions of 70mm in length and 23mm in width. The accessory FDS muscle belly was innervated by the median nerve. After developing a strong tendon, with a length of 51mm (right) and 85mm (left) and width of approximately 9.5mm, the accessory FDS inserted into the dorsal muscle belly of the main FDS. To further analyze the variation, the left accessory FDS muscle and tendon were separated from the adjacent tissues at the elbow and kept attached at the wrist. On a custom jig, 10N were applied sequentially to the main and accessory FDS separately and then together to access their function. Loading of the main FDS muscle resulted in flexion of the fingers with accentuation of the ulnar rays. Loading of the accessory FDS caused flexion of all four long fingers. We described a rare case of an accessory flexor digitorum superficialis, which may assist surgeons with clinical decisions. Surgeons should be aware of variability in forearm anatomy.

Muscle-tendon arrangement and innervation pattern of the m. flexor digitorum superficialis in the common marmoset (Callithrix jacchus), squirrel monkey (Saimiri sciureus) and spider monkey (Ateles sp.)

The muscle-tendon arrangement of the m. flexor digitorum superficialis (FDS) varies among different primate groups. Recent developmental investigations revealed that the primordium of FDS emerges in the hand region first and relocates to the forearm later. The relationship between the diverse muscle-tendon arrangement and the characteristic developmental process of FDS is important for understanding the evolutionary changes of the FDS. Moreover, the innervation pattern cannot go unremarked when discussing the muscle homology and evolution. We examined the muscle-tendon arrangement and intramuscular nerve distribution of the FDS in three genera of Platyrrhini: three common marmosets (Callithrix jacchus), two squirrel monkeys (Saimiri sciureus) and two spider monkeys (Ateles sp.). We observed that the FDS consisted of multiple muscle bellies. The origin of the muscle bellies to digits II and V varied, whereas muscle bellies to digits III and IV consistently originated from the medial epicondyle. The muscle-tendon arrangement of the FDS differed among the three genera owing to the different origins of muscle bellies to digits II and V. In all the examined specimens, the muscle bellies to digits II and/or III were innervated by the direct nerve branches from the median nerve. However, the muscle bellies to digits IV and V never received direct nerve branches from the median nerve. Nerve branches within the belly to digit III extended into the belly to digit IV, and one nerve branch within the belly to digit IV extended into the belly to digit V. These consistent nerve distribution patterns suggest that different patterns of FDS muscle-tendon arrangement have changed from that of a common ancestral condition. It is plausible that the diverse origins of muscle bellies in the FDS are attributable to the difference in the destination for the relocation of the muscle bellies during developmental processes.

Mapping of finger fascicles within the flexor digitorum superficialis and profundus muscles

INTRODUCTION

In this study we aimed to systematically investigate and map localization of the individual finger fascicles within the flexor digitorum superficialis (FDS) and the flexor digitorum profundus (FDP) muscles.

METHODS

Using B-mode ultrasonographic assessments, the right forearms of ten healthy participants (five males and five females) were examined during active and passive finger movements.

RESULTS

A topographical map indicating clear core areas of fascicle activation within the FDS and FDP muscles was created. Borders that could, to some degree, define individual differences were also indicated.

DISCUSSION

Our findings offer a detailed image of fascicle distributions within the FDS and FDP muscles. Various challenges, such as managing individual muscular profiles or the existence of the palmaris longus muscle, are discussed and should always be taken into consideration. The current map can serve as a general orientation for future measurements or injection therapies.

Agenesis, functional deficiency and the common type of the flexor digitorum superficialis of the little finger: A meta-analysis

Agenesis, functional deficiency and the common type of the flexor digitorum superficialis of the little finger are reported in the literature to be highly variable with significant discrepancy between clinical and cadaveric frequencies. The aim of this systematic review was to generate overall clinical and cadaveric weighted frequencies, along with ancestry-based, side-based, sex-based and laterality-based frequencies. A systematic literature search identified 34 studies including 12,213 forearms/hands that met the inclusion criteria. Functional deficit of the FDS tendon of the little finger was significantly more prevalent among Iranian and Caucasian populations as compared to Indian, East African and Chinese populations. The weighted "clinical" frequency of functional absence of the FDS tendon of the little finger was 7.45%, while prevalence of the common type was 37.5%. The weighted "cadaveric" prevalence of muscle absence of the FDS-5 in the forearm was 2.5% while tendon absence in the hands was nil. An expanded examination technique proved to be the most accurate test for FDS function. In case of injury, inadequate knowledge of different connections or substitutions of the FDS-5 could lead to a total loss of flexion of the little finger. These findings support the hypothesis of a dual origin of the FDS-5 where the muscle portion originates in the forearm, while the tendon portion originates in the hand.

Accessory muscle of the flexor digitorum superficialis and its clinical implications

Anatomical variations of the flexor digitorum superficialis (FDS) muscle and tendon unit are frequently reported by anatomists and clinicians. Anatomical muscle variations of the FDS and its tendons may include variations of muscle belly, presence of accessory or duplicate tendons, abnormal tendon connections, and absence of muscle or tendon components. Such variations may or may not have clinical implications. This report presents a case not described previously: a unilateral accessory muscle of the flexor digitorum superficialis which was connected by a thick tendon to the flexor digitorum superficialis muscle; it was directed proximally to the insertion of the medial epicondyle of the humerus, next to the superficialis head of the pronator teres muscle. The belly of the accessory muscle was positioned anterior to the median and anterior interosseous nerve. This anatomical variation is known as type V in the classification of Elliot et al. The knowledge of these anatomical variations helps hand surgeons interpret the clinical examination, particularly in the evaluation of patients who have suffered tendon injuries or show sign s of possible peripheral nerve entrapment.

A combined variation of Palmaris longus and Flexor digitorum superficialis: Case report and review of literature

The muscles of the anterior compartment of the forearm often exhibit anatomic variations. During dissection of the upper right limb of a preserved cadaver, morphological variations in the Palmaris longus and Flexor digitorum superficialis muscles were found. The Palmaris longus muscular fibers converged to a tendon that passed beneath the Flexor retinaculum, and inserted at the base of the middle phalanx of the fourth digit, replacing the tendon of Flexor digitorum superficialis. The Flexor digitorum superficialis was divided into two muscular heads: a digastric medial head giving tendons to the second and fifth digits, and a lateral head giving one tendon to the third digit. All these tendons were inserted in the respective digits by two bundles between which were located the tendon of the Flexor digitorum profundus muscle. Variations of flexor muscles must be documented because of their clinical significance and their potential use of these muscles in orthopaedic and reconstructive surgery.

Case of Trigger Finger Related to an Intertendinous Connection between the Flexor Tendons

We report a rare cause of trigger finger related to an anatomical variation of an intertendinous connection between the flexor digitorum superficialis and flexor digitorum profundus tendons in the palmar region.

Bilateral Absence of Flexor Digitorum Superficialis (FDS) Tendon of the Little Finger: Clinical Significance

The flexor digitorum superficialis (FDS/sublimis) is a flexor of the digits of the hand and has been reported to have varying degrees of agenesis. During routine cadaveric dissection for undergraduates at SRMS-IMS Bareilly, India, we observed bilateral absence of the FDS tendon to little finger in the upper limbs of a 45-year-old male cadaver. The muscle was normally supplied by a branch of median nerve in the forearm. Variants of the FDS muscle of the little finger have been reported in the literature. Proper knowledge of muscular variations is essential not only for anatomists but also for orthosurgeons, plastic surgeons and neurologists especially when evaluating possible tendon laceration/dysfunction. The FDS has been used as a motor for a wide variety of tendon transfer operations in the hand.

Painful, palpable and pathological: anomalous flexor digitorum superficialis brevis in the palm, comparative anatomical context, and an updated classification of anomalies of the flexor digitorum superficialis

Anomalies of the flexor digitorum superficialis are rare and can present a diagnostic dilemma. Patients present with a painful or palpable mass, or symptoms of carpal tunnel syndrome. This review article summarizes previously reported anomalies of the flexor digitorum superficialis, reports a further case, and proposes a new classification.

Repositioning forelimb superficialis muscles: tendon attachment and muscle activity enable active relocation of functional myofibers

The muscles that govern hand motion are composed of extrinsic muscles that reside within the forearm and intrinsic muscles that reside within the hand. We find that the extrinsic muscles of the flexor digitorum superficialis (FDS) first differentiate as intrinsic muscles within the hand and then relocate as myofibers to their final position in the arm. This remarkable translocation of differentiated myofibers across a joint is dependent on muscle contraction and muscle-tendon attachment. Interestingly, the intrinsic flexor digitorum brevis (FDB) muscles of the foot are identical to the FDS in tendon pattern and delayed developmental timing but undergo limited muscle translocation, providing strong support for evolutionary homology between the FDS and FDB muscles. We propose that the intrinsic FDB pattern represents the original tetrapod limb and that translocation of the muscles to form the FDS is a mammalian evolutionary addition.

Anomalous large unique muscle belly of flexor digitorum superficialis and the absence of palmaris longus in the forearm

Anomalies of muscles of the upper extremity are frequently encountered and anatomic variations of the flexor digitorum superficialis (FDS) muscle-tendon unit are frequently reported by anatomists and clinicians. FDS anomalies can be in forms of tendon interconnections, substitution, absence or muscle belly variations and most of the times the anomalies of FDS produce few clinical symptoms. We report a rare and unusual case of FDS anomaly with a unique and large muscle belly. The deformity is type V according to the classification of Elliot et al. in which the muscle belly extends to four digits (the index, middle, ring and little finger) in the right hand of patient and there is absence of the palmaris longus tendon. The hand surgeon should be able to realise all variations of the FDS tendon and should be prepared for unexpected findings during surgery.

The dual tendon palmaris longus variant causing dynamic median nerve compression in the forearm

This article describes a variant of palmaris longus muscle resulting in median nerve compression in the mid forearm. Although the palmaris longus has several well-documented anomalies, these seldom lead to nerve compression. The dual tendon, central muscle belly variant observed in this case is the first of its kind to be reported causing compressive neuropathy at this level. This is of both anatomical and clinical interest as it reminds surgeons of the anatomical variations of this unique muscle and presents a new mechanism of nerve compression in the forearm.

Three unusual factors contributing to compressive median neuropathy in the distal forearm in a single patient

Although there are varied aetiological factors responsible for compressive neuropathy of the median nerve in the carpal tunnel syndrome, it is rare to encounter several aetiological factors in a single case. This article reports a case in which three aetiological factors were present.

Anomalous flexor digitorum superficialis muscle belly presenting as a mass within the palm

Anomalies of the flexor digitorum superficialis muscle are extremely uncommon and usually present as a painful mass or pseudotumour within the palm. Diagnosis may be difficult because many other soft tissue tumours (lipomas, ganglions, giant cell tumours and hamartomas) may present similarly. Magnetic resonance imaging helps to define the extent and characteristics of this anomalous muscle belly and to distinguish it from a soft tissue sarcoma, whereas plain radiographs are of little value. Three types of flexor digitorum superficialis muscle anomalies have been described, and treatment consists of subtotal or total surgical debulking of the mass if symptoms persist or if the diagnosis is in question. Most patients have complete resolution and full recovery. To date, 20 cases have been reported in the literature, usually involving the right small finger. In the present paper, the case of an anomalous flexor digitorum superficialis muscle in a 17-year-old male patient's left index finger is reported. Symptoms were relieved following surgical debulking and hand-based occupational therapy.

Anomalies of the flexor carpi ulnaris: clinical case report and cadaveric study

Flexor carpi ulnaris (FCU) is an ever-present muscle of the anterior flexor compartment of the forearm. Variations of FCU are uncommon, with additional slips or heads of muscles described, and only one reported case of an accessory muscle. We describe a unique clinical case report in which an accessory FCU was identified and describe the findings of 5,000 cadaveric dissections of the forearm, performed as part of an ongoing institutional study of anatomical variations. An aberrant accessory forearm flexor muscle was identified incidentally at the wrist during surgery for an anterior interosseous to ulnar nerve transfer for management of ulnar nerve palsy. This muscle was seen running superficial to the ulnar nerve and radial to the FCU proper, arising from the common flexor origin and inserting at the triquetral carpal bone. This was therefore suitably acknowledged as an "accessory FCU". The anomaly was identified as bilateral using ultrasound imaging, and was found to be anomalously innervated by the median nerve with nerve conduction studies. A subsequent review of 5,000 cadaveric dissections of the forearm did not identify any such variations related to FCU, despite identifying a range of variations of the other forearm flexor musculature. While the scarcity of this anomaly is thus highlighted, consideration of an accessory FCU, and its aberrant innervation is important in a range of surgical approaches.

Anomalous muscle belly to the index finger

An unusual variation of flexor digitorum superficialis was observed during the cadaver dissection. The flexor digitorum superficialis (FDS) had a normal origin and insertion, except to the index finger, where a muscle belly replaced the tendon of FDS. The unusual muscle belly originated as a continuation of FDS tendon in the carpal tunnel and inserted normally into the middle phalanx. A branch of the median nerve innervated the anomalous muscle belly. The anomalous muscle belly described here should be considered in the aetiology of carpal tunnel syndrome.

The anatomy lesson of Dr. Nicolaes Tulp by Rembrandt (1632): a comparison of the painting with a dissected left forearm of a Dutch male cadaver

Rembrandt's The Anatomy Lesson of Dr. Nicolaes Tulp (1632) is considered a masterpiece and is a group portrait of the Amsterdam Guild of Surgeons in the form of an anatomy lesson. Dr. Nicolaes Tulp, Doctor of Medicine and Praelector Anatomiae to the Amsterdam Guild of Surgeons, showed an anatomic dissection of a forearm on the corpse of an executed criminal. The anatomic accuracy in Rembrandt's famous painting has been discussed in the literature for decades without any general consensus. In 2006, on the 400th anniversary of Rembrandt's birth, a forearm dissection of a cadaver and a comparison with the anatomy in the painting are presented to analyze the anatomic accuracy of Rembrandt's famous painting.

Selective recruitment of single motor units in human flexor digitorum superficialis muscle during flexion of individual fingers

Flexor digitorum superficialis (FDS) is an extrinsic multi-tendoned muscle which flexes the proximal interphalangeal joints of the four fingers. It comprises four digital components, each with a tendon that inserts onto its corresponding finger. To determine the degree to which these digital components can be selectively recruited by volition, we recorded the activity of a single motor unit in one component via an intramuscular electrode while the subject isometrically flexed each of the remaining fingers, one at a time. The finger on which the unit principally acted was defined as the 'test finger' and that which flexed isometrically was the 'active' finger. Activity in 79 units was recorded. Isometric finger flexion forces of 50% maximum voluntary contraction (MVC) activated less than 50% of single units in components of FDS acting on fingers that were not voluntarily flexed. With two exceptions, the median recruitment threshold for all active-test finger combinations involving the index, middle, ring and little finger test units was between 49 and 60% MVC (60% MVC being the value assigned to those not recruited). The exceptions were flexion of the little finger while recording from ring finger units (median: 40% MVC), and vice versa (median: 2% MVC). For all active-test finger combinations, only 35/181 units were activated when the active finger flexed at less than 20% MVC, and the fingers were adjacent for 28 of these. Functionally, to recruit FDS units during grasping and lifting, relatively heavy objects were required, although systematic variation occurred with the width of the object. In conclusion, FDS components can be selectively activated by volition and this may be especially important for grasping at high forces with one or more fingers.

Anomalous flexor digitorum superficialis muscle transposition for vascular coverage of the median nerve in recurrent carpal tunnel syndrome

Recurrent carpal tunnel syndrome is uncommon yet troublesome. Significant adhesions and scarring around the median nerve can render it relatively ischemic. A number of vascular flaps have been described to provide vascular coverage in attempts to decrease further cicatricial adhesions and to improve local blood supply around the median nerve. A rare case of an anomalous muscle in the distal forearm used as tissue to provide good vascularized coverage of the median nerve that was severely scarred in its bed is reported. The anomalous muscle was distal to the flexor digitorum superficialis tendon and inserted in the palmar fascia on the ulnar aspect of the hand. Referring branches from the ulnar artery provided vascular supply to the anomalous muscle. The muscle on these vascular pedicles was transposed over the median nerve, providing good, stable, unscarred coverage. The patient had an excellent result with resolution of the carpal tunnel symptoms. The redundant anomalous muscle provided a unique vascularized source for coverage of the median nerve in recurrent carpal tunnel syndrome.

Coexistence of multiple anomalies in the carpal tunnel

We determined the frequency of anomalous structures within the carpal tunnels of 89 cadaveric forearm-hand specimens. We also examined these same specimens for variations in the branching pattern of the median nerve, and analyzed the range in length and width of the lumbricals. Many of the hands contained extra tendinous slips from the long flexors within the tunnel, subligamentous thenar branches of the median nerve, or lumbricals with bipennate origins. Only one hand had an anomalous muscle belly within the tunnel, two had persistent median arteries, two had high division of the median nerve in the distal forearm, and eight had lumbricals with lengths or widths that were greater or less than 2 standard deviations (SD) from the mean. Twenty-nine percent of all hands examined had two to five anomalies/variations per tunnel, whereas another 27% had one anomaly or variation per tunnel. More right hands (17%) than left (11%) contained two to five anomalous/variant structures per carpal tunnel. More right hands (19%) than left (8%) contained only one variant/anomalous structure per carpal tunnel. Anticipation of the frequency and multiplicity of anomalous structures and variations within this region is of importance to clinicians, particularly surgeons.

Anomalous flexor of the little finger

We report an anomalous palmar muscle belly of the flexor digitorum superficialis muscle (FDS) in the right hand of an 80-year-old female cadaver. The muscle originated from the center of the volar surface of the flexor retinaculum and inserted onto the palmar aspect of the base of the middle phalanx of the little finger. Its tendon of insertion divided into two bands, a pattern typical of the FDS tendon, between which the tendon of flexor digitorum profundus muscle to the little finger passed. The tendon of the usual antebrachial FDS to the little finger was absent. The anomalous muscle belly was innervated by a branch from the median nerve.