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Concept: Flexor carpi radialis muscle

167

BACKGROUND: Tendon transfers are essential for reconstruction of hand function in tetraplegic patients. To transfer the extensor carpi radialis longus (ECRL), the extensor carpi radialis brevis (ECRB) has to be sufficiently strong. However, there is currently no reliable clinical test to individually analyse both muscles. In order to develop a reliable preoperative clinical test, the anatomy of the muscle (innervation) areas of ECRB, ECRL and brachio-radialis (BR) was examined. METHODS: In 20 arms, the ECRB, ECRL and BR were dissected and localised. Subsequently, muscle-innervation points were mapped and categorised. A novel method, computer-assisted surgical anatomy mapping (CASAM), was used to visualise muscle areas and innervation points in a computed arm with average dimensions. RESULTS: For both ECRL and ECRB a 100% area could be identified, a specific area in the computed average arm in which the muscle was present for all 20 arms. For the ECRL, this area was situated at 16% of the distance between the lateral epicondyle and the deltoid muscle insertion. The ECRB 100% area was 5 times bigger than that of the ECRL and was located at 40% of the distance between the lateral epicondyle and the radial styloid process. The ECRL and BR showed one to three innervation points, the ECRB one to four. In 47% of the cases, there was a combined nerve branch innervating both the ECRL and the ECRB. CONCLUSIONS: It is feasible to develop a preoperative test; the 100% areas can be used for needle electromyography (EMG) or local anaesthetic muscle injections.

Concepts: Muscle, Electromyography, Nerve, Upper limb anatomy, Brachioradialis, Flexor carpi radialis muscle, Extensor carpi radialis brevis muscle, Extensor carpi radialis longus muscle

27

The aim of this study was to examine changes in corticomotor excitability to a resting wrist extensor muscle during contralateral rhythmical isotonic and static isometric wrist contractions (flexion/extension) at different loads and positions, using transcranial magnetic stimulation (TMS). TMS-induced motor-evoked potentials (MEPs) were recorded from the relaxed right extensor carpi radialis (ECR) and flexor carpi radialis (FCR) respectively, while the left arm underwent unimanual manipulations. Rhythmical isotonic (0.5Hz) flexion and extension movements of the left wrist under 3 load conditions (no, low and high force) and a frequency matched passive movement condition were collected, along with isometric flexion/extension contractions in each position (low and high force). TMS was delivered at eight positions (4 in the flexion phase and 4 in the extension phase) during the continuous movement conditions and each of these positions was sampled with isometric contraction. The potentials evoked by TMS in right ECR were potentiated when the left ECR was engaged, independent of position within that phase of contraction or contraction type (isotonic and isometric). Motor cortical excitability of the resting right ECR increased as load demands increased to the left wrist. Passive rhythmical movement did not influence excitability to the resting ECR implying that voluntary motor drive is required. Our findings indicated that the increase in corticomotor drive during both rhythmic isotonic and static isometric contractions of the opposite limb is likely mediated by interhemispheric interactions between cortical motor areas. Improving our understanding of these cortical networks can be useful in future methods to enhance neuroplasticity through neurorehabilitation methods.

Concepts: Knee, Transcranial magnetic stimulation, Flexion, Extension, Semitendinosus muscle, Flexor carpi radialis muscle, Extensor carpi radialis longus muscle

26

Tendon rupture as a complication of distal radius fractures has been documented; however, flexor tendon rupture associated with closed distal radius fractures is rare. We report a case of a 43-year-old man who suffered a closed distal radius fracture. Intraoperatively, it was discovered that the flexor carpi radialis tendon had ruptured. From the frayed ends of the tendon and review of the radiographs, it was determined that the sharp ends of the fractured radius had lacerated the tendon at the time of injury. After fixation of the fracture with locking plate, the severed tendon was repaired and the wrist immobilised with a splint. The patient has been pain free after 5 months of follow-up, with full range of motion. This outcome demonstrates that timely detection and treatment of concurrent flexor carpi radialis tendon rupture and a closed distal radius fracture can achieve good functional results and outcome.

Concepts: Osteoporosis, Bone fracture, Fracture, Wrist, Tendon, Distal radius fracture, Bone fractures, Flexor carpi radialis muscle

25

Lateral epicondylalgia, pain at the lateral elbow, is commonly associated with extensor carpi radialis brevis tendinopathy. The radial head, which abuts the extensor tendons and is elliptical in shape, may affect the extensor tendons during pronation of the forearm. Cadaverous studies have shown that the radial head may act as a cam in pronation, to offer a mechanical advantage to the common extensor tendon and to mitigate load on the origin of the extensor carpi radialis brevis tendon.

Concepts: Forearm, Tendon, Brachioradialis, Tendinopathy, Flexor carpi radialis muscle, Extensor carpi radialis brevis muscle, Extensor carpi radialis longus muscle

14

A number of surgical techniques for managing tennis elbow have been described. One of the most frequently performed involves excising the affected portion of the extensor carpi radialis brevis (ECRB). The results of this technique, as well as most other described surgical techniques for this condition, have been reported as excellent, yet none have been compared with placebo surgery.

Concepts: Clinical trial, Surgery, Clinical research, Placebo, Flexor carpi radialis muscle, Extensor carpi radialis brevis muscle, Extensor carpi radialis longus muscle, Tennis elbow

3

Primary motor cortical (M1) adaptation has not been investigated in the transition to sustained muscle pain. Daily injection of nerve growth factor (NGF) induces hyperalgesia reminiscent of musculoskeletal pain and provides a novel model to study M1 in response to progressively developing muscle soreness. Twelve healthy individuals were injected with NGF into right extensor carpi radialis brevis (ECRB) on Days 0 and 2 and with hypertonic saline on Day 4. Quantitative sensory and motor testing and assessment of M1 organization and function using transcranial magnetic stimulation were performed prior to injection on Days 0, 2, and 4 and again on Day 14. Pain and disability increased at Day 2 and increased further at Day 4. Reorganization of M1 was evident at Day 4 and was characterized by increased map excitability. These changes were accompanied by reduced intracortical inhibition and increased intracortical facilitation. Interhemispheric inhibition was reduced from the “affected” to the “unaffected” hemisphere on Day 4, and this was associated with increased pressure sensitivity in left ECRB. These data provide the first evidence of M1 adaptation in the transition to sustained muscle pain and have relevance for the development of therapies that seek to target M1 in musculoskeletal pain.

Concepts: Muscle, Cerebral cortex, Cerebrum, Transcranial magnetic stimulation, Nerve growth factor, Flexor carpi radialis muscle, Extensor carpi radialis brevis muscle, Extensor carpi radialis longus muscle

2

Tennis elbow is a common elbow pathology typically affecting middle-aged individuals that can lead to significant disability. Most cases resolve within 2 years of symptom onset, but a subset of patients will develop persistent symptoms despite appropriate conservative management. There are several surgical approaches used to treat chronic tennis elbow, with arthroscopic surgery becoming an increasingly popular approach to address this pathology in North America. This procedure involves the arthroscopic release of the extensor carpi radialis brevis tendon (ECRB) origin at the elbow. The potential benefit of arthroscopic treatment of this condition is improved patient outcomes and shorter recovery time following surgery. The results of this technique have been reported only in the context of case series, which have shown positive results. However, in order to justify its widespread use and growing popularity, a high level of evidence study is required. The purpose of this prospective, randomized sham-controlled trial is to determine whether arthroscopic tennis elbow release is effective at treating chronic lateral epicondylitis.

Concepts: Hospital, United States, Surgery, North America, Flexor carpi radialis muscle, Extensor carpi radialis brevis muscle, Extensor carpi radialis longus muscle, Tennis elbow

1

Lateral epicondylitis, or “tennis elbow,” is a common musculotendinous degenerative disorder of the extensor origin at the lateral humeral epicondyle. Repetitive occupational or athletic activities involving wrist extension and supination are thought to be causative. The typical symptoms include lateral elbow pain, pain with wrist extension, and weakened grip strength. The diagnosis is made clinically through history and physical examination; however, a thorough understanding of the differential diagnosis is imperative to prevent unnecessary testing and therapies. Most patients improve with nonoperative measures, such as activity modification, physical therapy, and injections. A small percentage of patients will require surgical release of the extensor carpi radialis brevis tendon. Common methods of release may be performed via percutaneous, arthroscopic, or open approaches.

Concepts: Medical terms, Medical diagnosis, Elbow, Physical examination, Differential diagnosis, Flexor carpi radialis muscle, Extensor carpi radialis brevis muscle, Extensor carpi radialis longus muscle

0

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

Concepts: Hospital, Surgery, Physician, Flexor digitorum profundus muscle, Forearm, Wrist, Flexor carpi radialis muscle, Extensor carpi radialis brevis muscle

0

Volar locking plating through the flexor carpi radialis is a well-established technique for treating unstable distal radial fractures, with few reported complications. In certain circumstances, including metaphyseal comminuted fractures, bridge plating through a pronator quadratus (PQ)-sparing approach may be required to preserve the soft tissue envelope. This study describes our prospective experience with bridge plating through indirect reduction.

Concepts: Tissues, Soft tissue, Forearm, Distal radius fracture, Flexor carpi radialis muscle