A novel case of ulnar nerve compression neuropathy with co-existing accessory flexor carpi ulnaris and accessory abductor digiti minimi.

There are numerous cases reported of the accessory muscles of the hand and wrist in surgical, cadaveric, and imaging-based studies. Anatomical muscle variations in the flexor compartment of the wrist and forearm can present as a pseudo mass or space-occupying lesion causing external compression on the traversing nerves. Guyon's canal is a compact space with a high potential for nerve entrapment. Common etiologies include ganglion cysts, osteophytes, or soft tissue masses. This rare case illustrates the combined existence of two accessory muscles, an accessory flexor carpi ulnaris, and an accessory abductor digiti minimi, causing ulnar nerve compression in Guyon's canal with imaging correlation. One can raise the suspicion of an anomalous muscle when symptoms concern a patient of a younger age group in the absence of common etiologies. Furthermore, detailed anatomical knowledge of muscles around Guyon's canal is essential in making a diagnosis and aiding treatment.

Trapezium Tunnel Syndrome.

The trapezium tunnel is situated on the lateral side of the carpal tunnel, lined with synovial tissue, and accommodates the flexor carpi radialis tendon. Trapezium tunnel syndrome is characterized by flexor carpi radialis tendinitis/peritendinitis and may lead to complicated clinical scenarios, such as flexor carpi radialis tendon rupture and the formation of primary or recurrent ganglion cysts on the volar radial side of the wrist and thenar area. Notably, the simultaneous presence of trapezium tunnel syndrome might contribute to unsuccessful outcomes in carpal tunnel surgeries. Trapezium tunnel syndrome may arise from either intrinsic or extrinsic factors. The entity of trapezium tunnel syndrome has attracted a low index of clinical suspicion because the other causes of radial side wrist pain that are more prevalent and frequent. We present a narrative review of this condition in an endeavor to heighten awareness and clinical suspicion of trapezium tunnel syndrome.

A Fresh Cadaver Study on the Innervation of Brachioradialis and Extensor Carpi Radialis Longus Muscles.

PURPOSE: Distal nerve transfers have revolutionized peripheral nerve surgery by allowing the transfer of healthy motor nerves to paralyzed ones without causing additional morbidity. Radial nerve branches to the brachialis (Ba), brachioradialis (Br), and extensor carpi radialis longus (ECRL) muscles have not been investigated in fresh cadavers. METHODS: The radial nerve and its branches were dissected in 34 upper limbs from 17 fresh cadavers. Measurements were taken to determine the number, origin, length, and diameter of the branches. Myelinated fiber counts were obtained through histological analysis. RESULTS: The first branch of the radial nerve at the elbow was to the Ba muscle, followed by the branches to the Br and ECRL muscles. The Ba and Br muscles consistently received single innervation. The ECRL muscle showed varying innervation patterns, with one, two, or three branches. The branches to the Br muscles originated from the anterior side of the radial nerve, whereas the branches to the Ba and ECRL muscles originated from the posterior side. The average myelinated fiber counts favored the nerve to Br muscle over that to the ECRL muscle, with counts of 542 versus 350 and 568 versus 302 observed in hematoxylin and eosin and neurofilament staining, respectively. CONCLUSIONS: This study provides detailed anatomical insights into the motor branches of the radial nerve to the Ba, Br, and ECRL muscles. CLINICAL RELEVANCE: Understanding the anatomy of the radial nerve branches at the elbow is of utmost importance when devising a reconstructive strategy for upper limb paralysis. These findings can guide surgeons in selecting appropriate donor or recipient nerves for nerve transfer in cases of high tetraplegia and lower-type brachial plexus injuries.

Relationship between the elasticity of the forearm flexor-pronator muscles and elbow valgus torque in young baseball pitchers: a descriptive laboratory study.

BACKGROUND: The forearm flexor-pronator muscles act as a dynamic elbow stabilizer against elbow valgus load during baseball pitching. The elasticity of these muscles increases with pitching. However, it is unclear whether increased muscle elasticity is associated with greater elbow valgus torque during pitching. This study aimed to determine the relationship between the elasticity of the forearm flexor-pronator muscles and elbow valgus torque during pitching in young baseball pitchers. METHODS: We recruited 124 young baseball pitchers aged 9 to 12 years. The exclusion criteria included current pain with pitching, history of surgery on the tested extremity, or injuries on the tested extremity within the past 12 months. Before the examination, participants completed a questionnaire about their age, height, weight, dominant arm, and practice time per week. The strain ratios of flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS), and pronator teres as the index of muscle elasticity were measured using ultrasound strain elastography. Participants pitched 3 fastballs at a distance of 16 m (52 ft 6 in) with maximum effort while wearing a sensor sleeve that recorded the elbow valgus torque. A multiple linear regression analysis was conducted to examine the association between muscle elasticity and elbow valgus torque, adjusting for age, height, weight, and practice time. RESULTS: The final analysis included 107 pitchers. After adjusting for covariates, increased strain ratio of the FCU was significantly associated with greater elbow valgus torque (coefficients = 0.038, 95% confidence interval, 0.016-0.059, P < .001). Similarly, increased strain ratio of the FDS was significantly associated with greater elbow valgus torque (coefficients = 0.027, 95% confidence interval, 0.013-0.042, P < .001). CONCLUSION: The high elasticities of the FCU and FDS were associated with greater elbow valgus torque during pitching in young baseball pitchers. The high elasticity of these muscles is a protective response and may be necessary for young baseball pitchers with greater elbow valgus torque during pitching. Among young baseball pitchers with greater elbow valgus torque, those who are unable to produce the higher elasticities of these muscles could have greater elbow valgus load during pitching and be at a higher risk for elbow injuries. The measurement of the elasticities of the FCU and FDS may be useful for identifying young baseball pitchers at risk of sustaining elbow injuries.

Accessory Flexor Carpi Ulnaris Muscle in Humans: A Rare Anatomical Case with Clinical Considerations.

Anatomical variations of the forearm flexor muscles are occasionally encountered. Though usually observed incidentally during autopsies or imaging studies, they may at times cause concern due to associated clinical symptoms. This report presents a case of unilateral accessory flexor carpi ulnaris (AFCU) muscle observed in a human male cadaver aged 78 years. During routine cadaveric dissection, an anomalous AFCU muscle was observed in the left forearm of a human male cadaver aged 78 years. Standard institutional guidelines pertaining to the use of human cadaver for teaching and research were followed. A thorough literature review about the flexor carpi ulnaris (FCU) through the PubMed, Embase and Google scholar databases was undertaken, using the keywords - accessory flexor carpi ulnaris muscle, aberrant flexor carpi ulnaris muscle and anatomical variation of flexor carpi ulnaris muscle. Relevant gross anatomical findings were recorded and photographed. AFCU was identified on the medial aspect of the distal third of the left forearm. The AFCU was found originating from the ante-brachial fascia and the fascia covering the FCU on the left forearm, forming a small separate belly deep to the main muscle. It terminated as a thin tendon running alongside the hypothenar muscles and attached distally to the base of the proximal phalanx of the little finger. The AFCU was found to be innervated by a branch of the ulnar nerve. Awareness about the rare AFCU muscle is clinically important as a possible cause of ulnar nerve compression but also as a possible graft in reconstruction surgeries.

Gender differences on effects of forearm rotation on compressive stiffness of flexor carpi ulnaris during submaximal handgrip contractions.

Little is known about gender differences in stiffness of forearm muscles during voluntary actions. This study aimed to investigate the effect of forearm rotation on flexor carpi ulnaris (FCU) stiffness in men and women during submaximal handgrip contractions. During a single session, measurements were made on 20 young participants (9 females). Two positions of the forearm were compared in random order with the elbow flexed 90 degrees: (i) neutral position and (ii) maximal supination. In each position, participants performed two submaximal handgrip contractions at 25% and 50% of maximal voluntary contraction, while compressive stiffness was collected using a hand myometer (MyotonPRO). A mixed repeated measurement ANOVA was applied to assess the interaction between gender, forearm position, and contraction intensity. The FCU stiffness is affected by handgrip contraction intensity (p < 0.001), gender (p < 0.001), BMI (p = 0.009), and forearm rotation (p = 0.007). Only the gender factor was found to have significant interaction with forearm rotation (p = 0.037). Men's FCU was stiffer than women's in both positions and contraction intensities (p < 0.05). Only in men a significant increase in FCU stiffness was observed when comparing contraction intensities at both forearm positions (p < 0.05), as well as when the forearm was rotated from neutral to supine at both intensities (p < 0.05). In conclusion, FCU stiffness during handgrip contraction differed significantly between men and women. Women have fewer stiffness changes in FCU when performing different levels of handgrip contraction. We also observed that only men increased FCU stiffness by changing the forearm position from neutral to supine position for both handgrip intensities.

The role of Vesalius and his contemporaries in the transfiguration of human anatomical science.

The understanding of human anatomy has been an endeavour spanning thousands of years from the Egyptians and Greeks in antiquity to the present day. Scholars and scientists have overcome great barriers to discover the inner workings and complexities of the human body, from personal challenges and prejudices to obstacles placed by society. Our present understanding of anatomy has accumulated over centuries, and progressive generations of physicians have contributed to the ever-growing evidence-based knowledge. This article explores the contributions made by Vesalius and his contemporaries in the first half of the sixteenth century. These enlightened scholars advanced anatomical knowledge and, perhaps more importantly, the scientific method, directly impacting the mindset and methodologies of future anatomists. Individuals such as Berengario da Carpi and Gabriele Falloppio produced bodies of work during their lifetime that were not only important in disputing the teachings of Galen of Pergamon, which had been accepted as almost unquestionable truths for a thousand years, but also instrumental in developing a new generation of scientists. The anatomists of the late renaissance were unable to resolve many of the factual inaccuracies of Galenic teaching but provided the groundwork for scientific thinking which future generations of anatomists benefited greatly from. The principles of documenting what is observed and establishing a methodical approach to question discrepancies in experiments would go on to influence physicians such as Harvey and Malpighi to investigate and draw correct conclusions in their research and ultimately advance our understanding of human anatomy to what it is today.

Ultrasonographic anatomy of the palmar region of the carpus of the dog.

The palmar region of the canine carpus may be injured by traumatic, inflammatory, infectious, neoplastic, and degenerative disorders. The normal ultrasonographic anatomic features of the dorsal region of the canine carpus have been published, however information regarding the palmar region is currently lacking. The aims of this prospective, descriptive, anatomic study were (1) to describe the normal ultrasonographic characteristics of the palmar carpal structures in medium to large-breed dogs, and (2) to establish a standardized ultrasonographic protocol for evaluating them. As in the previously published study, the current study consisted of two phases: (1) identification phase, in which the palmar structures of the carpus were identified ultrasonographically in fifty-four cadaveric specimens and an ultrasonographic protocol to examine them was developed; and (2) descriptive phase, in which the ultrasonographic characteristics of the main palmar structures in twenty-five carpi of thirteen living healthy adult dogs were documented. The tendons of the flexor muscles of the carpus and digits, the superficial and deep parts of the retinaculum flexorum, the carpal canal and the median and ulnar neurovascular structures were ultrasonographically identified and described. Findings from the current study can serve as a reference for evaluating dogs with suspected injury involving the palmar carpal region using ultrasonography.

Estimating the motor unit number of the flexor carpi ulnaris muscle with MScanFit MUNE.

INTRODUCTION/AIMS: MScanFit motor unit number estimation (MUNE) is a promising method for motor unit estimation and is reported to have good reliability in distal and small muscles. In this study, we investigated the reliability of MScanFit MUNE in a proximal forearm muscle, the flexor carpi ulnaris. METHODS: Twenty healthy volunteers were included in this study, and 15 participants were re-evaluated in a second session. The ulnar nerve was stimulated at the elbow and a compound muscle action potential (CMAP) scan from the flexor carpi ulnaris (FCU) muscle was recorded from each arm. CMAP, MUNE, and other motor unit parameters were obtained. Reproducibility was evaluated using intraclass correlation coefficients (ICCs). RESULTS: The average MUNE from 40 FCU muscles was 90.9 (standard deviation: 16.4). MScanFit MUNE and CMAP were not significantly different between the dominant and non-dominant sides. The ICC indicated good reliability between sessions for each side (0.81 and 0.8, respectively). DISCUSSION: Our results indicate that MScanFit MUNE is a feasible method with good reproducibility for MUNE of the FCU muscle.

A Simplified Modification of the Henderson Extensor Carpi Ulnaris Opposition Transfer.

PURPOSE: There are several potential donor muscle-tendon units for a thumb opposition transfer. The extensor carpi ulnaris (ECU) is useful when the more usual donor units are not available. The technique and results of a simplified ECU opposition transfer elongated with a free tendon graft are described. METHODS: Ten ECU opposition transfers were performed using this modification of Henderson technique in 5 adults after complex trauma, 3 adults with median and ulnar nerve palsies, and 2 children with congenital hand differences. RESULTS: Seven patients achieved a Kapandji opposition score of 6 to the distal phalanx of the small finger, and 3 patients achieved a Kapandji score of 5 to the distal phalanx of the ring finger. None of the patients required a secondary tenolysis or developed a radial deviation imbalance of their wrist. CONCLUSIONS: This modification of the Henderson technique using ECU elongated with a free tendon graft and inserted directly and only into the abductor pollicis brevis tendon is an effective method of restoring opposition to the thumb, especially when other conventional donor muscle-tendon units are not available. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic V.

Motion Analysis of the Extensor Carpi Ulnaris in Triangular Fibrocartilage Complex Injury Using Ultrasonography Images.

The subsheath of the extensor carpi ulnaris (ECU) tendon, a component of the triangular fibrocartilage complex (TFCC), is particularly important as it dynamically stabilizes the distal radioulnar joint. However, the relationship between TFCC injury and ECU dynamics remains unclear. This study aimed to analyze ECU movement and morphology using ultrasonography (US) images. Twenty wrists of patients with TFCC injury, who underwent TFCC repair, were included in the injury group, and 20 wrists of healthy volunteers were in the control group. For static image analysis, curvature and linearity ratios of the ECU in US long-axis images captured during radioulnar deviation were analyzed. For dynamic analysis of the ECU, the wrist was moved from radial deviation to ulnar deviation at a constant speed, and the velocity of the tendon was analyzed using particle image velocimetry. The static analysis showed that the ECU tendon was more curved in ulnar deviation in the injury group than in the control group, and the dynamic analysis showed that only vertical velocity toward the deep side during ulnar deviation was higher in the injury group. These results suggest that TFCC injury caused ECU curvature during ulnar deviation and increased the vertical velocity of the ECU during wrist deviation.

The muscular branching patterns of the ulnar nerve in fetal forearms.

OBJECTIVE: We aimed to present our findings systematically by examining the muscular branching patterns of the ulnar nerve (UN) in the forearms of fetuses. METHODS: This study was conducted on the 52 forearms of 26 formalin-fixed fetal cadavers with gestational ages varying between 19 and 37 weeks. The anatomical dissection was performed by using stereomicroscope with × 8 magnification. The numbers of muscular branches leaving UN and their order of leaving main nerve were noted down. The findings were classified according to the muscles they reached, and branching typing was done. RESULTS: It was found that a total of 2-6 muscular branches left UN to reach flexor carpi ulnaris (FCU) and flexor digitorum profundus (FDP). UN was classified by separating into five main types according to the number of muscular branches, and these types were classified into 16 different branching patterns according to the order of branches leaving from the main trunk and going to FCU and FDP. The pattern where two branches left UN was classified as Type I (n = 6), three branches left was classified as Type II (n = 18), four branches left was classified as Type III (n = 24), five branches left was classified as Type IV (n = 3), and six branches left was classified as Type V (n = 1). Martin-Gruber connection occurred in 17 (32.7%) fetal forearms. CONCLUSION: We believe that the information that UN can demonstrate different branching patterns on the forearm can help the surgeons to prevent complications that may develop in potential nerve injury during the selection and transfer of relevant branch.

Typology of flexor carpi radialis muscle in human fetuses.

INTRODUCTION: The musculus flexor carpi radialis (FCR) is a muscle with an important function for the mechanics and physiology of the hand. Its isolation during intrauterine development occurs relatively late, which may result in the presence of high variability during the fetal period. The aim of this study is to determine the detailed typology of FCR in the fetal period based on the available material. MATERIAL AND METHODS: A total of 114 human fetuses (53 female, 61 male) aged between 117.0 and 197.0 days of fetal life were included in the study. The research material was derived from the collections of the Department of Anatomy, Medical University of Wroclaw. Fetuses were stored in typical conservation solvents. The study incorporated the following methods: anthropological, preparational, and image acquisition, which was obtained using an innovative digital microscope. Statistical analysis was performed using R software. RESULTS: The typology of FCR was determined based on the characteristics of the distal attachment of the investigated muscle. The statistical analysis revealed a predominance of type I in the examined fetal material - the attachment located on metacarpal bone II (about 82% of cases). Type IV (attachment to the 4th metacarpal bone) occurs with a frequency of less than 10% and the remaining types II and III occur with a frequency of 4-6%. The statistical analysis did not reveal bilateral or dimorphic differences in the prevalence of each FCR type. In respect of the collected anthropometric parameters, no statistically significant dimorphic differences were revealed. For a more complete description, the FCR proportionality index was introduced. The mean value of this index was 0.6 and was independent of the side or sex of the analyzed fetus. CONCLUSIONS: FCR in the fetal period is characterized by a stable course in both the proximal and distal attachments.

Partial trapeziectomy for Eaton stage III thumb carpometacarpal arthritis: ligament reconstruction with tendon interposition using the entire flexor carpi radialis and interference screw fixation.

BACKGROUND: Trapeziectomy with ligament reconstruction and tendon interposition (LRTI) is currently the most popular technique for treating primary osteoarthritis of the thumb carpometacarpal joint. However, reduced trapezial height has sometimes been reported after LRTI. Longer immobilization and delayed rehabilitation times are also problematic. In this study, we evaluated the clinical and radiological outcomes of patients who underwent our modified LRTI procedure. METHODS: Retrospective study included 26 thumbs in 24 cases with advanced stages. Our modified Burton's procedure was as follows: (1) trapeziectomy was limited to distal-half, (2) the entire flexor carpi radialis (FCR) was harvested from the forearm, and (3) half-slip of the FCR tendon was stabilized by interference screw in the first metacarpal bone tunnel. RESULTS: Pain on the visual analogue scale (VAS), the quick Disabilities of the Arm Shoulder and Hand score, tip pinch strength significantly improved postoperatively. The preoperative height of the trapezial space was well-maintained at final follow-up. Magnetic resonance imaging at the one-year follow-up showed the existence of FCR tendon ball in 15 cases. Eighteen housewives resumed their daily activities after a mean period of 10 days postoperative, while another 6 patients returned to their original jobs after 3 weeks. CONCLUSIONS: Our modified LRTI method involves distal-half trapeziectomy and entire FCR interposition. A sewn FCR tendon ball always provide enough volume to fill the trapeziectomy space, which helps to prevent sinking of the metacarpal bone. Our technique produced sufficient ligamentoplasty and allowed early mobilization after surgery.

The effects of local forearm heating and cooling on motor unit properties during submaximal contractions.

NEW FINDINGS: What is the central question of this study? How do temperature manipulations affect motor unit (MU) properties during submaximal contractions to the same relative percentage of maximal force? What is the main finding and its importance? MU recruitment patterns are affected by temperature manipulations at the forearm. However, the relationship between MU potential amplitude and recruitment threshold indicates no change to the order or recruitment. Additionally, the MU potential amplitude and firing rate relationship was affected by temperature, suggesting that smaller MUs are more affected by temperature changes than larger MUs. ABSTRACT: Temperature impacts muscle contractile properties, such that experiments with workloads based on thermoneutral values will produce different relative intensities if maximal force changes due to muscle temperature. We investigated how temperature affected motor unit (MU) properties with contractions performed at the same normalized percentage of maximal force. Twenty participants (10 females) completed evoked, maximal, and trapezoidal voluntary contractions during thermoneutral-, hot-, and cold-temperature conditions. Forearm temperature was established using 25 min of neutral (∼32°C), hot (∼44°C) or cold (∼13°C) water circulated through a tube-lined sleeve. Flexor carpi radialis MU properties were assessed with contractions at 30% and 60% MVC relative to each temperature using surface electromyography decomposition. Changes to contractile properties and electromechanical delay from the evoked twitch suggest that muscle contractility was changed from the thermal manipulations (effect size (d) ≥ 0.42, P < 0.05). Maximal force was not different between neutral and hot conditions (d = 0.16, P > 0.05) but decreased in the cold (d ≥ 0.34, P < 0.05). For both contraction intensities, MU potential (MUP) amplitude was larger and duration was longer in the cold compared to neutral and hot conditions (d ≥ 1.24, P < 0.05). Cumulative probability density for the number of MUs recruited revealed differences in MU recruitment patterns among temperature conditions. The relationship between MU recruitment threshold and firing rate or MUP amplitude was not different among temperature conditions (P > 0.05); however, the relationship between MUP amplitude and firing rate was (P < 0.05). Local temperature manipulations appear to affect MU recruitment patterns, which may act as compensatory mechanisms to the changes in muscle viscosity and contractile properties due to local temperature changes.

"Snapping" of the extensor carpi ulnaris tendon in asymptomatic population.

BACKGROUND: Extensor carpi ulnaris tendinopathy (ECU) can be one cause of ulnar side wrist pain and it is more prominent in pronation-supination movements against resistance. In supination, flexion, and ulnar deviation within the ulnar groove, the tendon is tense and becomes predisposed to subluxation or dislocation. Snapping occurs during this dislocation and relocation. As a result of this friction between the tendon sheath and ulnar groove, tendinopathy and pain occur. ECU tendon is an important structure that contributes to the dynamic stability of wrist therefore resulting degeneration contributes disruption of distal radioulnar joint and causes wrist instability. METHODS: Participants without active wrist complaints who presented to the outpatient clinic between 2019 and 2020 were included. Provocation test was performed and participants with snapping were evaluated with ultrasound to determine subluxation or dislocation. Participants asked to indicate approximately how much time they spent daily on the phone, computer and game console. The distribution of data was evaluated with the Kolmogorov-Smirnov test. Quantitative data that were not normally distributed were evaluated using the Mann-Whitney U test, and Student's t-test was used for normally distributed data. The Chi-square test was used to compare categorical variables. For all tests, p < 0.05 was considered statistically significant. RESULTS: Four hundred and fifteen women and 340 men were included in the study. Fifty of the 755 participants (6.6 %) had snapping. 22 of the 755 participants (2.9 %) had dislocation or subluxation on ultrasound. Three (13.6 %) participants had dislocation and 19 (%86.4) participants had subluxation on ultrasound. All 50 of the participants with snapping had significant repetitive trauma and sports activities. It was determined that 21 of the 22 participants who were found to have subluxation or dislocation by ultrasound had more than two hours of hobby activity and significantly more participants had more than two hours of activity compared to the group without subluxation or dislocation. CONCLUSIONS: This study with a large number of participants will contribute to the literature in terms of evaluating the contribution of technological devices, such as computers, smartphones, and consoles to chronic wrist pain and the prevalence of ECU snapping in the asymptomatic population. TRIAL REGISTRATION: Date of Approval; 19.02.2019, Approval Number; 19-KAEK-045.

Subluxation of the extensor carpi ulnaris on magnetic resonance imaging on neutral wrist position: correlation with tenosynovitis of the extensor carpi ulnaris and translation of the distal radioulnar joint.

OBJECTIVE: To identify the subluxation degrees of extensor carpi ulnaris (ECU) tendon on neutral wrist MRI in patients with ulnar-sided wrist pain and to evaluate the relationships of ECU subluxation with accompanying imaging findings such as ECU tenosynovitis, distal radioulnar joint (DRUJ) stability, and triangular fibrocartilage complex (TFCC) pathology. MATERIALS AND METHODS: A total of 297 MRIs of 292 patients having ulnar side pain were reviewed retrospectively. Degrees of ECU subluxation was classified into four grades: grade 0, no subluxation; grade 1, tendon displacement < 50% of the tendon width; grade 2, tendon displacement 51 to 99% of the tendon width; and grade 3, tendon displacement of 100% of the tendon width. ECU tenosynovitis, ECU tendinosis, injuries of triangular fibrocartilage and distal radioulnar ligaments (DRUL), translation ratio of the DRUJ, rotation angle of the DRUJ, and the width, depth, and length of the ulnar groove were assessed on wrist MRI. The relationships between degree of ECU subluxation and these imaging findings were investigated. RESULTS: Women had higher subluxation degrees of the ECU tendon (p = 0.001). Tenosynovitis of the ECU, sprain of the dorsal DRUL, dorsovolar translation ratio and rotation angle of the DRUJ, and depth and length of the ulnar groove were statistically significantly related to the subluxation degree of the ECU tendon (p = 0.000). CONCLUSION: High-grade subluxation of the ECU tendon was strongly correlated with ECU tenosynovitis and DRUJ translation. Clinicians and radiologists should scrutinize imaging findings, particularly when patients with ulnar-sided wrist pain have high-grade subluxation of the ECU tendon.

Anatomical Study of Stabilizing Structures of the Extensor Carpi Ulnaris Tendon Around the Wrist.

PURPOSE: The sixth dorsal extensor compartment is a relatively common site of stenosing tenosynovitis in the upper extremity, but the exact location of stenosis is not fully understood. The objective of this study was to investigate the detailed anatomy of structures surrounding the extensor carpi ulnaris (ECU) tendon around the wrist. METHODS: Fifty fresh human cadaveric wrists were used for gross observation and morphology measurements of the sixth dorsal compartment and the ECU subsheath. An additional 13 wrists were used for histological examination. We evaluated the morphology of supporting structures in 3 regions: the ulnar groove (zone I), the ulnar styloid process (zone II), and the triquetrum (zone III). RESULTS: The fibro-osseous tunnel comprising the ulnar groove and the overlying subsheath (zone I) stabilized the ECU tendon, and the subsheath had thin membranous collagen fibers attached to the periosteum. We consistently found the distal extension of ECU subsheath (zone II), which connected the ulnar styloid process and the dorsal radioulnar ligament. Variations in the length of the distal extension increased with the forearm in pronation. Collagen fiber thickness around the ECU tendon in zone II was greater than that of zone I. In zone III, the overlying extensor retinaculum and septa, which were composed of thick circumferential collagen structures, supported the ECU tendon by attaching to the triquetrum on both sides of the ECU tendon. We found the presence of an ulnar septum of the sixth compartment attached to the triquetrum in 84% of dissected wrists. CONCLUSIONS: The ECU tendon was supported by the ECU subsheath, which had thin and elastic collagen fibers over the ulnar groove. Distal extension of the subsheath and surrounding radial and ulnar extensor retinaculum septa attached to the triquetrum provided thicker supporting structures. CLINICAL RELEVANCE: Stenosing ECU tenosynovitis may occur not only in the ulnar groove but also in the more distal ulnar styloid process and triquetrum areas.

Medial elbow exposure: an anatomic comparison of 5 approaches.

PURPOSE: Several surgical approaches to the medial elbow are described; however, it remains unclear which exposure provides the optimal view of relevant medial elbow structures. The purpose of this anatomic study was to determine the visible surface area of the coronoid process, distal humerus, and radial head through 5 approaches to the medial elbow. METHODS: Eight fresh-frozen cadaveric upper extremity specimens were dissected. Five surgical approaches were performed on each specimen. The Smith muscle-splitting approach to the ulnar collateral ligament was performed first (Smith), followed by the Hotchkiss medial "Over the top" approach (Hotchkiss), the extended medial elbow approach (EMEA), the flexor carpi ulnaris splitting approach (FCU-Split), and the Taylor and Scham approach (T&S). Bony visualization was determined using laser surface scanning (Artec Space Spider; Artec 3D). The scans were segmented using commercially available digital software (Geomagic Wrap; 3D Systems Corporation), and the surface area visualized was determined. A descriptive analysis of the joint areas visible using the medial collateral ligament (MCL) as a clinical landmark was performed. RESULTS: The EMEA visualized the highest proportion of the total elbow joint from the medial side showing 13.9 ± 6.0 cm2, or 15% ± 4% of the joint. It also provided the best visualization of the coronoid (3.2 ± 1.7 cm2 of surface area, or 26% ± 9%) and distal humerus (9.9 ± 4.3 cm2, or 15% ± 4%). The Hotchkiss approach was best at visualizing the radial head (0.8 ± 0.3 cm2, or 7% ± 3%). The EMEA, Hotchkiss, and Smith approaches showed primarily the anterior bundle of the MCL, its insertion, and the regions anterior to it, whereas the FCU-Split showed the anterior bundle of the MCL and regions both anterior and posterior to it. The T&S showed primarily the areas posterior to the anterior bundle of the MCL; the anterior regions were not visible. The FCU-Split and the T&S allowed visualization of the posterior bundle of the MCL. The intraclass correlation coefficients (ICCs) for intraobserver reliability were 0.997, 0.992, and 0.974 for the test distal humerus, test coronoid, and test radial head, respectively. The ICCs for interobserver reliability were 0.915 for the test distal humerus, 0.66 for the coronoid, and 0.583 for the radial head. CONCLUSION: The EMEA provides the most visualization of the coronoid and distal humerus, whereas the Hotchkiss showed the most radial head. However, these approaches mainly visualize structures anterior to the MCL. If exposure of structures posterior to the MCL is required, the FCU-Split and T&S approaches are more appropriate.

Morphological and functional assessment of the flexor carpi radialis brevis using conventional ultrasound and elastography.

PURPOSE: The flexor carpi radialis brevis (FCRB) is a supernumerary musculotendinous structure of the wrist that has been the focus of some interest in the last decade. While its anatomy is well known, its in vivo function remains unknown as it has never been studied. METHODS: Eleven cases of FCRB underwent a multimodal ultrasound consisting of B-mode, color Doppler and shear wave elastography. RESULTS: A pennate shape was observed in all cases and the mean value of the cross-sectional area was 0.8 cm2 (SD 0.3 cm2). Young's modulus was significantly (p < 0.01) different between the resting position and active flexion or passive extension. CONCLUSION: Our study demonstrates that the FCRB shows biomechanics of a typical skeletal muscle and is voluntarily controlled by flexing the wrist. Absent in other vertebrate taxa, the FCRB probably plays a role in active stability of the wrist in Human.