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Concept: Extensor carpi ulnaris muscle


INTRODUCTION: We present the case of a patient with extensor carpi ulnaris tendon subluxation who was first treated for distal radioulnar joint sprain. CASE PRESENTATION: A 25-year-old Caucasian man was seen at our policlinic one month after he had fallen on his outstretched hand. A diagnosis of extensor carpi ulnaris subluxation was made clinically but we also had the magnetic resonance imaging scan of the patient’s wrist which displayed an increased signal on T2-weighted images consistent with inflammation around the extensor carpi ulnaris tendon. The extensor carpi ulnaris tendon was found to be dislocating during supination and relocating during pronation. The sheath was reconstructed using extensor retinaculum due to attenuation of subsheath. CONCLUSION: There was no recurrent dislocation of the extensor carpi ulnaris tendon of the patient at his last follow up 12 months after the operation.

Concepts: Nuclear magnetic resonance, Magnetic resonance imaging, Wrist, Joint dislocation, Distal radioulnar articulation, Extensor carpi ulnaris muscle, Extensor carpi radialis longus muscle, Proximal radioulnar articulation


Abstract Tendons like the flexor carpi ulnaris (FCU) that contain region-specific distributions of proteoglycans (PGs) as a result of the heterogeneous, multi-axial loads they are subjected to in vivo provide valuable models for understanding structure-function relationships in connective tissues. However, the contributions of specific PGs to FCU tendon mechanical properties are unknown. Therefore, the objective of this study was to determine how the location-dependent, viscoelastic mechanical properties of the FCU tendon are impacted individually by PG-associated glycosaminoglycans (GAGs) and by two small leucine-rich proteoglycans (SLRPs), biglycan and decorin. Full length FCU tendons from biglycan- and decorin-null mice were compared to wild type mice to evaluate the effects of specific SLRPs, while chondroitinase ABC digestion of isolated specimens removed from the tendon midsubstance was used to determine how chontroitin/dermatan sulfate (CS/DS) GAGs impact mechanics in mature FCU tendons. A novel combined genetic knockout/ digestion technique also was employed to compare SLRP-null and wild-type tendons in the absence of CS/DS GAGs that may impact properties in the mature state. In all genotypes, mechanical properties in the FCU tendon midsubstance were not affected by GAG digestion. Full-length tendons exhibited complex, multi-axial deformation under tension that may be associated with their in vivo loading environment. Mechanical properties were adversely affected by the absence of biglycan, and a decreased modulus localized in the center of the tendon was measured. These results help elucidate the role that local alterations in proteoglycan levels may play in processes that adversely impact tendon functionality including injury and pathology.

Concepts: Gene, Collagen, Extracellular matrix, Proteoglycan, Cartilage, Glycosaminoglycan, Tendon, Extensor carpi ulnaris muscle


The extensor carpi ulnaris (ECU) muscle plays a key role not only in the active movements of wrist extension and ulnar deviation but also in providing stability to the ulnar side of the wrist. Its position relative to the other structures in the wrist changes with forearm pronation and supination. As such, it must be mobile yet stable. The ECU tendon relies on specific stabilising structures to hold it in the correct positions to perform its different functions. These structures can be injured in a variety of different athletic activities such as tennis, golf and rugby league, yet their injury and disruption is predictable when the mechanics of the ECU and the techniques of the sport are understood. The ECU tendon is also vulnerable to tendon pathologies other than instability. It lies subcutaneously and is easily palpated and visualised with diagnostic ultrasound, allowing early diagnosis and management of its specific conditions. Treatment includes rest, splintage and surgery with each modality having specific indications and recognised outcomes. This review described the functional anatomy in relevant sporting situations and explained how problems occur as well as when and how to intervene.

Concepts: Pathology, Ulna, Medical school, Forearm, Wrist, Pronation, Extensor carpi ulnaris muscle, Extensor carpi radialis longus muscle


Dystrophin deficiency results in lethal Duchenne muscular dystrophy (DMD). Substituting missing dystrophin with abbreviated microdystrophin has dramatically alleviated disease in mouse DMD models. Unfortunately, translation of microdystrophin therapy has been unsuccessful in dystrophic dogs, the only large mammalian model. Approximately 70% of the dystrophin-coding sequence is removed in microdystrophin. Intriguingly, loss of ≥50% dystrophin frequently results in severe disease in patients. To test whether the small gene size constitutes a fundamental design error for large mammalian muscle, we performed a comprehensive study using 22 dogs (8 normal and 14 dystrophic). We delivered the ΔR2-15/ΔR18-19/ΔR20-23/ΔC microdystrophin gene to eight extensor carpi ulnaris (ECU) muscles in six dystrophic dogs using Y713F tyrosine mutant adeno-associated virus (AAV)-9 (2.6 × 10(13) viral genome (vg) particles/muscle). Robust expression was observed 2 months later despite T-cell infiltration. Major components of the dystrophin-associated glycoprotein complex (DGC) were restored by microdystrophin. Treated muscle showed less inflammation, fibrosis, and calcification. Importantly, therapy significantly preserved muscle force under the stress of repeated cycles of eccentric contraction. Our results have established the proof-of-concept for microdystrophin therapy in dystrophic muscles of large mammals and set the stage for clinical trial in human patients.Molecular Therapy (2013); doi:10.1038/mt.2012.283.

Concepts: Heart, Muscle, Electromyography, Muscle contraction, Muscular dystrophy, Duchenne muscular dystrophy, Muscle biopsy, Extensor carpi ulnaris muscle


Although the orientations of the hand and forearm vary for different wrist rehabilitation protocols, their effect on muscle forces has not been quantified. Physiologic simulators enable a biomechanical evaluation of the joint by recreating functional motions in cadaveric specimens. Control strategies used to actuate joints in physiologic simulators usually employ position or force feedback alone to achieve optimum load distribution across the muscles. After successful tests on a phantom limb, unique combinations of position and force feedback - hybrid control and cascade control - were used to simulate multiple cyclic wrist motions of flexion-extension, radioulnar deviation, dart thrower’s motion, and circumduction using six muscles in ten cadaveric specimens. Low kinematic errors and coefficients of variation of muscle forces were observed for planar and complex wrist motions using both novel control strategies. The effect of gravity was most pronounced when the hand was in the horizontal orientation, resulting in higher extensor forces (p<0.017) and higher out-of-plane kinematic errors (p<0.007), as compared to the vertically upward or downward orientations. Muscle forces were also affected by the direction of rotation during circumduction. The peak force of flexor carpi radialis was higher in clockwise circumduction (p=0.017), while that of flexor carpi ulnaris was higher in anticlockwise circumduction (p=0.013). Thus, the physiologic wrist simulator accurately replicated cyclic planar and complex motions in cadaveric specimens. Moreover, the dependence of muscle forces on the hand orientation and the direction of circumduction could be vital in the specification of such parameters during wrist rehabilitation.

Concepts: Knee, Simulation, Operations research, Classical mechanics, Forearm, Wrist, Euclidean vector, Extensor carpi ulnaris muscle


To investigate the ulnar groove (UG), extensor carpi ulnaris (ECU) tendon, and ulnar styloid process (USP) parameters in asymptomatic individuals without ulnar-sided wrist abnormalities, to determine whether these values can be anthropometric markers of age and gender and identify their correlations for use in clinical decision-making.

Concepts: Ulna, Forearm, Wrist, Ulnar nerve, Extensor carpi ulnaris muscle, Extensor carpi radialis longus muscle, Flexor carpi ulnaris muscle


Various flaps are used for skin defects of the dorsal hand and fingers. A sensory flap is not essential, but a thin and good color-matched flap is suitable, and donor site mobility of the flap should be considered. A reverse or free posterior interosseous artery perforator flap is one of the standard flaps. This flap requires no major arterial sacrifice, but direct closure of the donor site is difficult when the width of the flap is >3 cm, and there is also the risk of posterior interosseous nerve injury, especially the motor branch of the extensor carpi ulnaris muscle. The deltoid or acromial branch of the thoracoacromial artery has a large skin perforator, and this perforator is the vascular pedicle of the free thoracoacromial artery perforator flap. This flap is not bulky, is pliable and well color-matched for the dorsal hand, and direct closure of the donor site is easier than the posterior interosseous artery perforator flap. A free thoracoacromial artery perforator flap based on the deltoid or acromial branch is a good option for dorsal hand and finger reconstruction.

Concepts: Heart, Forearm, Finger, Ring finger, Arteries of the upper limb, Extensor carpi ulnaris muscle


The Sauvé-Kapandji (SK) procedure is one of several surgical options in the treatment of distal radioulnar disorders by osteoarthritis (OA) and rheumatoid arthritis (RA). While satisfactory postoperative clinical results were obtained in most cases, instability of the proximal ulnar stump and radioulnar convergence are the most common complications. Minami et al. have developed a modification of the SK procedure that maintains the transverse diameter of the distal radioulnar joint and stabilizes the proximal ulnar stump, using a half-slip of the extensor carpi ulnaris tendon. In this study, the modified SK procedure was performed on 83 patients with distal radioulnar disorders, due to OA and RA.

Concepts: Rheumatoid arthritis, Rheumatology, Osteoarthritis, Ulna, Arthritis, Ligament, Distal radioulnar articulation, Extensor carpi ulnaris muscle


Ulnar variance, or the difference in height between the joint surfaces of the distal radius and ulna, may play a role in several diseases of the wrist.

Concepts: Humerus, Ulna, Forearm, Wrist, Ulnar nerve, Carpal tunnel, Extensor carpi ulnaris muscle


The novel human-computer interface (HCI) using bioelectrical signals as input is a valuable tool to improve the lives of people with disabilities. In this paper, surface electromyography (sEMG) signals induced by four classes of wrist movements were acquired from four sites on the lower arm with our designed system. Forty-two features were extracted from the time, frequency and time-frequency domains. Optimal channels were determined from single-channel classification performance rank. The optimal-feature selection was according to a modified entropy criteria (EC) and Fisher discrimination (FD) criteria. The feature selection results were evaluated by four different classifiers, and compared with other conventional feature subsets. In online tests, the wearable system acquired real-time sEMG signals. The selected features and trained classifier model were used to control a telecar through four different paradigms in a designed environment with simple obstacles. Performance was evaluated based on travel time (TT) and recognition rate (RR). The results of hardware evaluation verified the feasibility of our acquisition systems, and ensured signal quality. Single-channel analysis results indicated that the channel located on the extensor carpi ulnaris (ECU) performed best with mean classification accuracy of 97.45% for all movement’s pairs. Channels placed on ECU and the extensor carpi radialis (ECR) were selected according to the accuracy rank. Experimental results showed that the proposed FD method was better than other feature selection methods and single-type features. The combination of FD and random forest (RF) performed best in offline analysis, with 96.77% multi-class RR. Online results illustrated that the state-machine paradigm with a 125 ms window had the highest maneuverability and was closest to real-life control. Subjects could accomplish online sessions by three sEMG-based paradigms, with average times of 46.02, 49.06 and 48.08 s, respectively. These experiments validate the feasibility of proposed real-time wearable HCI system and algorithms, providing a potential assistive device interface for persons with disabilities.

Concepts: Novel, Disability, Object-oriented programming, Wrist, Selection, User interface, Extensor carpi ulnaris muscle, Extensor carpi radialis longus muscle