Anterior instability of the glenohumeral joint with humeral avulsion of the glenohumeral ligament. A review of 41 cases.
We studied retrospectively a consecutive series of 547 shoulders in 529 patients undergoing operation for instability. In 41, the cause of instability was considered to be lateral avulsion of the capsule, including the inferior glenohumeral ligament, from the neck of the humerus, the HAGL lesion. In 35, the lesion was found at first exploration, whereas in six it was noted at revision of a previous failed procedure. In both groups, the patients were older on average than those with instability from other causes. Of the primary cases, in 33 (94.3%) the cause of the first dislocation was a violent injury; six (17.4%) had evidence of damage to the rotator cuff and/or the subscapularis. Only four (11.4%) had a Bankart lesion. In patients undergoing a primary operation in whom the cause of the first dislocation was a violent injury, who did not have a Bankart lesion and had no suggestion of multidirectional laxity, the incidence of HAGL was 39%. (+info)
Multijoint muscle regulation mechanisms examined by measured human arm stiffness and EMG signals.
Stiffness properties of the musculo-skeletal system can be controlled by regulating muscle activation and neural feedback gain. To understand the regulation of multijoint stiffness, we examined the relationship between human arm joint stiffness and muscle activation during static force control in the horizontal plane by means of surface electromyographic (EMG) studies. Subjects were asked to produce a specified force in a specified direction without cocontraction or they were asked to keep different cocontractions while producing or not producing an external force. The stiffness components of shoulder, elbow, and their cross-term and the EMG of six related muscles were measured during the tasks. Assuming that the EMG reflects the corresponding muscle stiffness, the joint stiffness was predicted from the EMG by using a two-link six-muscle arm model and a constrained least-square-error regression method. Using the parameters estimated in this regression, single-joint stiffness (diagonal terms of the joint-stiffness matrix) was decomposed successfully into biarticular and monoarticular muscle components. Although biarticular muscles act on both shoulder and elbow, they were found to covary strongly with elbow monoarticular muscles. The preferred force directions of biarticular muscles were biased to the directions of elbow monoarticular muscles. Namely, the elbow joint is regulated by the simultaneous activation of monoarticular and biarticular muscles, whereas the shoulder joint is regulated dominantly by monoarticular muscles. These results suggest that biarticular muscles are innervated mainly to control the elbow joint during static force-regulation tasks. In addition, muscle regulation mechanisms for static force control tasks were found to be quite different from those during movements previously reported. The elbow single-joint stiffness was always higher than cross-joint stiffness (off-diagonal terms of the matrix) in static tasks while elbow single-joint stiffness is reported to be sometimes as small as cross-joint stiffness during movement. That is, during movements, the elbow monoarticular muscles were occasionally not activated when biarticular muscles were activated. In static tasks, however, monoarticular muscle components in single-joint stiffness were increased considerably whenever biarticular muscle components in single- and cross-joint stiffness increased. These observations suggest that biarticular muscles are not simply coupled with the innervation of elbow monoarticular muscles but also are regulated independently according to the required task. During static force-regulation tasks, covariation between biarticular and elbow monoarticular muscles may be required to increase stability and/or controllability or to distribute effort among the appropriate muscles. (+info)
Correlation of primate superior colliculus and reticular formation discharge with proximal limb muscle activity.
We studied the discharge of neurons from both the superior colliculus (SC) and the underlying mesencephalic reticular formation (MRF) and its relation to the simultaneously recorded activity of 11 arm muscles. The 242 neurons tested with a center-out reach task yielded 2,586 pairs of neuron/muscle cross-correlations (normalized, such that perfect correlations are +/-1.0). Of these, 43% had peaks with magnitude as large as 0.15, a value that corresponds to the 5% level of significance, and 16% were as large as 0.25. The great majority of peaks in this latter group was positive. The median lag time within this group was 52 ms, indicating that the neuronal discharge tended to precede the correlated muscle activity. We found a small but significantly higher proportion of cells with these relatively strong correlations in the MRF than in the SC. For both areas, these occurred most frequently with muscles of the shoulder girdle and became less frequent for axial as well as for increasingly distal arm musculature. The results support a role for the SC and MRF in guiding the arm during reach movements via the control of proximal limb musculature. (+info)
The inferior capsular shift operation for instability of the shoulder. Long-term results in 34 shoulders.
We reviewed 26 patients with 34 shoulders treated by the inferior capsular shift operation for inferior and multidirectional instability. The mean follow-up was 8.3 years. In total, 12 shoulders showed voluntary subluxation. Eight operations used an anterior and posterior approach, 11 were by the posterior route, and 15 shoulders had an anterior approach. In 30 shoulders (85%) the outcome was satisfactory and 20 (59%) scored good or excellent results on the Rowe system. Instability had recurred in nine shoulders (26%) from three months to three years after the operation. Six of the 12 shoulders with voluntary subluxation (50%) had recurrence, as against three of the other 22 (14%), a statistically significant difference. The operation is therefore not indicated for voluntary subluxation. The 19 shoulders which had been assessed in 1987 at a mean of 3.5 years after surgery, were also reviewed in 1995 and found to have no significant changes in instability or Rowe score. This shows that the capsular shift appeared to have maintained its tension over an eight-year period. After the use of a posterior approach, 64% of the shoulders showed a posterolateral defect on radiographs of the humerus. (+info)
Adhesive capsulitis: a sticky issue.
The shoulder is a very complex joint that is crucial to many activities of daily living. Decreased shoulder mobility is a serious clinical finding. A global decrease in shoulder range of motion is called adhesive capsulitis, referring to the actual adherence of the shoulder capsule to the humeral head. Adhesive capsulitis is a syndrome defined as idiopathic restriction of shoulder movement that is usually painful at onset. Secondary causes include alteration of the supporting structures of and around the shoulder, and autoimmune, endocrine or other systemic diseases. The three defined stages of this condition are the painful stage, the adhesive stage and the recovery stage. Although recovery is usually spontaneous, treatment with intra-articular corticosteroids and gentle but persistent physical therapy may provide a better outcome, resulting in little functional compromise. (+info)
Case report. Recovery of shoulder movement in patients with complete axillary nerve palsy.
Classical anatomical teaching suggests that the deltoid muscle is the main abductor of the shoulder. We present three cases of proven complete paralysis of the deltoid with an almost full range of movement of the shoulder owing to the compensatory action of accessory muscles. The mechanisms by which this occurs are described. (+info)
Diagnostic classification of shoulder disorders: interobserver agreement and determinants of disagreement.
OBJECTIVES: To assess the interobserver agreement on the diagnostic classification of shoulder disorders, based on history taking and physical examination, and to identify the determinants of diagnostic disagreement. METHODS: Consecutive eligible patients with shoulder pain were recruited in various health care settings in the Netherlands. After history taking, two physiotherapists independently performed a physical examination and subsequently the shoulder complaints were classified into one of six diagnostic categories: capsular syndrome (for example, capsulitis, arthritis), acute bursitis, acromioclavicular syndrome, subacromial syndrome (for example, tendinitis, chronic bursitis), rest group (for example, unclear clinical picture, extrinsic causes) and mixed clinical picture. To quantify the interobserver agreement Cohen's kappa was calculated. Multivariate logistic regression analysis was applied to determine which clinical characteristics were determinants of diagnostic disagreement. RESULTS: The study population consisted of 201 patients with varying severity and duration of complaints. The kappa for the classification of shoulder disorders was 0.45 (95% confidence intervals (CI) 0.37, 0.54). Diagnostic disagreement was associated with bilateral involvement (odds ratio (OR) 1.9; 95% CI 1.0, 3.7), chronic complaints (OR 2.0; 95% CI 1.1, 3.7), and severe pain (OR 2.7; 95% CI 1.3, 5.3). CONCLUSIONS: Only moderate agreement was found on the classification of shoulder disorders, which implies that differentiation between the various categories of shoulder disorders is complicated. Especially patients with high pain severity, chronic complaints and bilateral involvement represent a diagnostic challenge for clinicians. As diagnostic classification is a guide for treatment decisions, unsatisfactory reproducibility might affect treatment outcome. To improve the reproducibility, more insight into the reproducibility of clinical findings and the value of additional diagnostic procedures is needed. (+info)
Prevention of shoulder subluxation after stroke with electrical stimulation.
BACKGROUND AND PURPOSE: Subluxation is a significant problem in poststroke hemiplegia, resulting in pain and loss of function. Current treatments are not proved and not considered effective. It has been demonstrated that cyclical electrical stimulation of the shoulder muscles can reduce existing subluxation. The purpose of this study was to determine whether electrical stimulation could prevent subluxation in both the short and long terms. METHODS: A prospective, randomized controlled study was used to determine the efficacy of electrical stimulation in preventing shoulder subluxation in patients after cerebrovascular accidents. Forty patients were selected and randomly assigned to a control or treatment group. They had their first assessment within 48 hours of their stroke, and those in the treatment group were immediately put on a regimen of electrical stimulation for 4 weeks. All patients were assessed at 4 weeks after stroke and then again at 12 weeks after stroke. Assessments were made of shoulder subluxation, pain, and motor control. RESULTS: The treatment group had significantly less subluxation and pain after the treatment period, but at the end of the follow-up period there were no significant differences between the 2 groups. CONCLUSIONS: Electrical stimulation can prevent shoulder subluxation, but this effect was not maintained after the withdrawal of treatment. (+info)