Is synergistic organisation of muscle coordination altered in people with lateral epicondylalgia? A case-control study

BACKGROUND

Lateral epicondylalgia is a common musculoskeletal disorder and is associated with deficits in the motor system including painful grip. This study compared coordination of forearm muscles (muscle synergies) during repeated gripping between individuals with and without lateral epicondylalgia.

METHODS

Twelve participants with lateral epicondylalgia and 14 controls performed 15 cyclical repetitions of sub-maximal (20% maximum grip force of asymptomatic arm), pain free dynamic gripping in four arm positions: shoulder neutral with elbow flexed to 90° and shoulder flexed to 90° with elbow extended both with forearm pronated and neutral. Muscle activity was recorded from extensor carpi radialis brevis/longus, extensor digitorum, flexor digitorum superficialis/profundus, and flexor carpi radialis, with intramuscular electrodes. Muscle synergies were extracted using non-negative matrix factorisation.

FINDINGS

Analysis of each position and participant, demonstrated that two muscle synergies accounted for >97% of the variance for both groups. Between-group differences were identified after electromyography patterns of the control group were used to reconstruct the patterns of the lateral epicondylalgia group. A greater variance accounted for was identified for the controls than lateral epicondylalgia (p=0.009). This difference might be explained by an additional burst of flexor digitorum superficialis electromyography during grip release in many lateral epicondylalgia participants.

INTERPRETATION

These data provide evidence of some differences in synergistic organisation of activation of forearm muscles between individuals with and without lateral epicondylalgia. Due to study design it is not possible to elucidate whether changes in the coordination of muscle activity during gripping are associated with the cause or effect of lateral epicondylalgia.

Biomechanical evaluation of a new reconstruction technique of the ulnar collateral ligament in the elbow with modified bone tunnel placement and interference screw fixation

BACKGROUND

A new method for reconstruction of the anterior bundle of the ulnar collateral ligament using modified bone tunnel placement and interference screw fixation was developed to minimize operative dissection, improve graft tensioning, and reduce associated operative morbidities. The objective of this study was to compare varus-valgus laxity and failure properties of this new ulnar collateral ligament reconstruction to the intact ulnar collateral ligament.

METHODS

Nine matched pairs of cadaveric upper extremities were used, the intact ulnar collateral ligament as the control for the load to failure properties and the contralateral arm for ulnar collateral ligament reconstruction. Varus-valgus laxity was measured at 30 degrees, 50 degrees, 70 degrees, and 90 degrees of elbow flexion for intact, ulnar collateral ligament transected, and ulnar collateral ligament reconstruction. Ulnar collateral ligament reconstruction was performed using a tendon graft passed through a bone tunnel and looped around the medial column of the humerus without dissection of the ulnar nerve. Distally, the graft was looped through a bone tunnel in the proximal ulna. Both ends were secured with interference screws. The specimens were loaded to failure at 50 degrees of flexion at a rate of 30 deg/s. Repeated measures analysis of variance with a P value of 0.05 was used.

FINDINGS

Elbow laxity significantly increased with ulnar collateral ligament transection. Following reconstruction, varus-valgus laxity at 30 degrees and 50 degrees of elbow flexion was completely restored to the intact state, only partially restored at 70 degrees, and not changed at 90 degrees. There was no significant difference between the yield and ultimate torques for the intact vs. reconstructed elbows. The angular displacement at yield and failure was significantly greater for the reconstructed elbows compared to the intact.

INTERPRETATION

This reconstruction technique provides comparable strength to that of the native ligament. While stability was improved, failure occurred at greater angular displacement for the reconstructed limbs.

The effect of endurance exercise on the morphology of muscle attachment sites

The morphology of muscle attachment sites, or entheses, has long been assumed to directly reflect in vivo muscle activity. The purpose of this study is to examine whether variations in muscle activity that are within normal physiological limits are reflected in variations in external attachment site morphology. This study tests the hypothesis that increased muscle activity (magnitude, number and frequency of loading cycles) results in the hypertrophy of muscle attachment sites. The attachment sites of six limb muscles and one muscle of mastication (control) in mature female sheep were measured and compared in exercised (weighted treadmill running for 1 h per day for 90 days) and sedentary control animals. Attachment site surface morphology was assessed by quantifying the size (3D surface area) and complexity (fractal dimension parallel and perpendicular to soft tissue attachment) of the surfaces.

The results of this study demonstrate no effect of the exercise treatment used in this experiment on any measure of enthesis morphology. Potential explanations for the lack of exercise response include the mature age of the animals, inappropriate stimulus type for inducing morphological change, or failure to surpass a hypothetical threshold of load for inducing morphological change. However, further tests also demonstrate no relationship between muscle size and either attachment site size or complexity in sedentary control animals. The results of this study indicate that the attachment site morphological parameters measured in this study do not reflect muscle size or activity. In spite of decades of assumption otherwise, there appears to be no direct causal relationship between muscle size or activity and attachment site morphology, and reconstructions of behavior based on these features should be viewed with caution.

Exercise-induced compartment syndrome in the flexor-pronator muscle group. A case report and pressure measurements in volunteers

Compartment syndrome is caused by an increase in intracompartmental pressure above the capillary level, preventing capillary flow. The acute onset of symptoms occurs after events such as fracture, soft tissue trauma, and revascularization and usually necessitates prompt fasciotomy to avoid loss of function or even necrosis of the enclosed muscle. Compartment syndromes in athletes are of a recurrent nature and are usually referred to as chronic. Nonoperative treatment is often successful. Although compartment syndromes can occur in several anatomic regions, the most commonly seen in athletes involve the leg. Chronic compartment syndromes of the upper extremity are rare, and only a few cases have been reported in the literature. The intracompartmental pressures causing chronic symptoms in these cases ranged between 22 mm Hg at rest and 40 mm Hg after 30 minutes of exercise. Under maximal contraction, a pressure of 58 mm Hg has been recorded. The object of this paper is to report a case of a tennis player where much higher flexor-pronator muscle intracompartmental pressures than those noted above were recorded. We compared the intracompartmental pressure data of this patient with intracompartmental pressures measured in six symptom-free volunteers.

High prevalence of elbow problems among goalkeepers in European team handball -- 'handball goalie's elbow'

The aim of this study was to describe elbow problems among goalkeepers in team handball. A questionnaire was sent to the coaches of 449 senior and 32 junior teams in Norway in 1992. Of these, 304 coaches responded (63%) and their teams were included in the study. A total of 329 out of 729 goalkeepers (45+/-1.8%) and 166 out of 4120 court players (4.0+/-0.3%) were reported by their coaches to have current or previous symptoms from one or both elbows when playing handball. In response to a second questionnaire sent to all the goalkeepers (729; response rate 81%), 41+/-2.0% reported current elbow problems and an additional 34+/-2.0% reported previous problems. During a 2-year observation period from 1992 to 1994, 8.6+/-1.8% of the goalkeepers with previously healthy elbows experienced elbow problems. The typical complaint was recurrent pain and disability episodes, each with an acute onset, but with varying duration. The mechanism of injury for the goalkeepers appears to be repeated hyperextension traumas. We conclude that elbow pain and disability is a significant problem for a large number of goalkeepers in team handball. These problems may be described as a syndrome called 'handball goalie's elbow'.

Functional anatomy of the flexor pronator muscle group in relation to the medial collateral ligament of the elbow

To describe the relationship of the pronator teres, flexor carpi radialis, flexor digitorum superficialis, and flexor carpi ulnaris muscles to the medial collateral ligament at 30 degrees, 90 degrees, and 120 degrees of elbow flexion, we dissected 11 cadaveric specimens. The flexor carpi ulnaris muscle is the predominant musculotendinous unit overlying the medial collateral ligament in the majority of cases and is the only one at 120 degrees of elbow flexion. The flexor digitorum superficialis muscle is the only other significant contributor. The medial collateral ligament is the primary stabilizer of the medial elbow with elbow flexion greater than 30 degrees, as in throwing. The flexor carpi ulnaris muscle, because of its position directly over the medial collateral ligament, and the flexor digitorum superficialis muscle, with its near proximity and relatively large bulk, are the specific muscles best suited to provide medial elbow support. This is especially relevant to overhand throwing athletes who encounter extreme valgus force across the elbow during the cocking and acceleration phases of the throwing motion. Exercise and conditioning of the medial elbow musculature, specifically the flexor digitorum superficialis muscle and the flexor carpi ulnaris muscle, may prevent injury or assist in rehabilitation of medial elbow instability, especially in overhand throwing athletes.

Wrist kinematics differ in expert and novice tennis players performing the backhand stroke: implications for tennis elbow

Investigators have suggested that the greater prevalence of lateral humeral epicondylitis (tennis elbow, TE) in novice tennis players compared to expert players may reflect the novice players' use of faulty mechanics for the backhand stroke. We investigated the wrist kinematics (flexion/extension), grip pressures, and wrist muscle electromyographic activity in novice (N = 8) and expert (N = 8) tennis players performing the backhand stroke. Experts performed the backhand stroke with the wrist extended (re: neutral alignment of the forearm and hand dorsum). Collision of the ball and racket occurred with the wrist extended on average of 0.41 rad (about 23 degrees from neutral alignment) in the expert players; moreover, their wrists were moving further into extension at impact. In contrast, novice subjects struck the ball with the wrist flexed 0.22 rad (about 13 degrees) while moving their wrists further into flexion. Wrist extensor EMGs showed similar levels of activity during the 500 ms interval before ball-racket impact, whereas expert subjects displayed greater EMG levels after contact, consistent with the accompanying wrist extension. The wrist kinematic and EMG data together show that the novice subjects eccentrically contracted their wrist extensor muscles throughout the stroke. We argue that conditions exist for novice subjects that assist stretch of wrist extensor muscles upon collision of the ball and racket. The resulting eccentric contraction of wrist extensor muscles may contribute to lateral TE in novice players, given previous research indicating that eccentric muscle contraction facilitates muscle fiber injury.

Postcranial robusticity in Homo. II: Humeral bilateral asymmetry and bone plasticity

The analysis of humeral asymmetry in Recent human skeletal samples and an extant tennis-player sample documents minimal asymmetry in bone length, little asymmetry in distal humeral articular breadth, but pronounced and variable asymmetry in mid- and distal diaphyseal cross-sectional geometric parameters. More specifically, skeletal samples of normal modern Euroamericans, prehistoric and early historic Amerindians, and prehistoric Japanese show moderate (ca. 5-14%) median asymmetry in diaphyseal cross-sectional areas and polar second moments of area, whereas the tennis-player sample, with pronounced unilateral physical activity, exhibits median asymmetries of 28-57% in the same parameters. A sample of Neandertals with nonpathological upper limbs exhibits similarly low articular asymmetry but pronounced diaphyseal asymmetries, averaging 24-57%. In addition, three Neandertals with actual or possible post-traumatic upper limb alterations have the same low articular asymmetry but extremely high diaphyseal asymmetries, averaging 112-215%. These data support those from experimental work on animals, exercise programs of humans, and human clinical contexts in establishing the high degree of diaphyseal plasticity possible for humans, past and present, under changing biomechanical loading conditions. This lends support to activity-related functional interpretations of changing human diaphyseal morphology and robusticity during the Pleistocene.

Chronic stress injuries of the elbow in young gymnasts

The radiological changes of chronic stress injuries of the elbow in 19 adolescent elite gymnasts are reported. The principal abnormalities were avascular necrosis of the capitellar epiphysis (Panner's disease) (one patient), post-traumatic subarticular necrosis (osteochondritis dissecans) of the capitellum (six patients) and the medial articular eminence of the distal humerus (one patient). Flattening and anterior depression of the radial head epiphysis with an underlying metaphyseal notch associated with an epiphyseal cleft (three patients), which, in one patient who continued training, developed into a chronic Salter Type IV stress fracture. A further patient, post-epiphyseal fusion, showed osteochondritis dissecans of the anterior aspect of the radial head. Seven patients exhibited a spectrum of olecranon changes from fragmentation of the epiphysis to chronic Salter Type I stress fractures of the growth plate. A follow-up survey found that, of those who responded to a questionnaire, nearly all the patients with articular surface damage failed to continue with competitive gymnastics whereas those with olecranon abnormalities were able to continue gymnastics at the same level. The mechanism of injury and the pathological changes are discussed.

Injuries of exercise

This article presents a brief overview of a few of the conditions that may affect the exercising individual. An accurate diagnosis and a positive attitude toward exercise on the part of the physician is stressed.

A Study of Players With Pain

The results of this study suggest that the harmful effects of tennis are cumulative and that many variables may interact before elbow pain occurs.

The Elbow and Tennis, Part 1: An Analysis of Players With and Without Pain

After studylng 2,633 average tennis players, the authors offer some surprlslng new ideas about the factors that may contribute to elbow pain.

Correctable elbow lesions in professional baseball players: a review of 25 cases

In a retrospective study, 20 of 25 professional baseball pitchers (mean age, 24 years; range, 19 to 28 years) who had had a reconstructive surgical procedure on the dominant elbow had satisfactory results (able to return to competitive throwing for one full season or more after surgery). Gentle motion wasinitiated 1 week after the operation on each patient. Exercises for mobilization and muscle strengthening of grip, arm, and shoulder were increased until throwing was initiated 10 to 12 weeks postoperatively. Throwing was gradually increased over several weeks from 30 feet at no more than half speed for 15 min to 60 feet at three-quarter speed. Pitchers were instructed to warm up before throwing and warm down and to continue this practice after they began competitive throwing. The longest period of follow-up had been 4 years (mean, 2.8 years). Four of the 25 pitchers had unsatisfactory results (released from their team in less than one full season because of ineffective pitching and were not picked up by another team). The cause of the release of the other patient-player is controversial. This 25-patient group is too small and the follow-up period is too short for definite conclusions. Our evidence does suggest that surgical procedures directed at medial soft tissue and posterior intra-articular changes carry better prognosis for competitive throwers than other procedures. The radiohumeral articular condition should be evaluated at surgery.

Thalamic neuron theory: a hypothesis concerning pain and acupuncture

A new theory is proposed to explain various pain phenomena hitherto unexplainable. It is hypothesized that neurons in the thalamic region are responsible for the generation of most pain, particularly in chronic pain states. It is also hypothesized that the thalamic neurons are organized according to a master scheme representing a homunculus in the fetal position. Various painful conditions and the treatments of them including the trigger points phenomena, neurosurgical techniques, acupuncture and acupuncture anesthesia can be explained on this basis.