Dynamic evaluation and early management of altered motor control around the shoulder complex.

Altered dynamic control appears to be a significant contributing factor to shoulder dysfunction. The shoulder relies primarily on the rotator cuff for dynamic stability through mid-range. Hence, any impairment in the dynamic stabilizing system is likely to have profound effects on the shoulder complex. The rotator cuff appears to function as a deep stabilizer, similar to the transversus abdominus and vastus medialis obliquus, with some evidence of disruption to its stabilizing function in the presence of pain. Similarly, serratus anterior appears to function as a dynamic stabilizer, also demonstrating altered function in painful shoulders. Examination of dynamic control begins with a detailed examination of posture, evaluation of natural movement patterns and functional movements and assessment of the specific force couples relevant to shoulder function. One useful strategy in management of altered motor control related to these force couples is that of training isolated contraction of the rotator cuff prior to introduction of loaded activity, together with facilitation and training of appropriate scapular muscle force couples--serratus anterior and trapezius, in relation to arm elevation.

Specific evaluation of the function of force couples relevant for stabilization of the glenohumeral joint.

Two clinical evaluation procedures for assessment of dynamic stability of the glenohumeral joint are presented in this paper, together with the biomedical evidence on which they are based. They are the Dynamic Rotary Stability Test (DRST) and the Dynamic Relocation Test (DRT). The purpose of the tests is presented and the technique required to perform the tests are described in detail.

Variation in shoulder position sense at mid and extreme range of motion.

OBJECTIVE: To determine the effect of different joint positions on position sense of asymptomatic shoulders. DESIGN: Repeated-measures design. SETTING: Laboratory in an educational institution. PARTICIPANTS: Thirty-four asymptomatic, right-handed men. INTERVENTIONS: The ability of subjects to replicate 3 criterion positions was examined on subjects' right shoulders by using an isokinetic dynamometer. Three criterion positions were the 50th, 75th, and 90th percentiles of each individual's total passive shoulder rotation range measured from the full internal rotation position. MAIN OUTCOME MEASURE: Repositioning accuracy, indicating the difference in degrees between the criterion and matching positions. RESULTS: All subjects were able to reproduce the criterion position near the end of external rotation range more accurately and consistently than in the middle range of motion (ROM). CONCLUSIONS: Position sense acuity at the shoulder complex varied across the ROM and may be enhanced near the end of rotation range where there is more tension on the restraints to movement. Therefore, an individual's ROM should be factored into any attempt to assess or rehabilitate shoulder proprioception.

The Musculoskeletal Physiotherapy of Australia position on pre-manipulative testing for the cervical spine.

The MPA undertook a survey of its members in 1997 to determine their compliance with and opinion of the APA Protocol for Pre-Manipulative Testing of the Cervical Spine (Magarey et al 2000a, Magarey et al submitted-a). As a result of that survey and a comprehensive literature review, the MPA developed a new set of guidelines for premanipulative procedures for the cervical spine (Magarey et al 2000b, Magarey et al submitted-b).

EMG and strength correlates of selected shoulder muscles during rotations of the glenohumeral joint.

OBJECTIVE: To identify activation patterns of several muscles acting on the shoulder joint during isokinetic internal and external rotation. DESIGN: Combined EMG and isokinetic strength analysis in healthy subjects. BACKGROUND: EMG studies of the shoulder region revealed intricate muscular activation patterns during elevation of the arm but no parallel studies regarding pure rotations of the joint could be located. METHODS: Fifteen (n=30 shoulders) young, asymptomatic male subjects participated in the study. Strength production during isokinetic concentric and eccentric internal and external rotations at 60 and 180 degrees /s was correlated with the EMG activity of the rotator cuff, biceps, deltoid and pectoralis major. Analysis of the smoothed EMG related to the timing of onset of the signal and to the normalized activity at the angle of the peak moment. Determination of the association between the EMG and the moment was based on strength ratios. RESULTS: Findings indicated that for both types of rotations, the rotator cuff and biceps were active 0.092+/-0.038-0.215+/-0.045 s prior to the initiation of the actual movement and 0.112-0.034 s prior to onset of deltoid and pectoralis major activity. These differences were significant in all of the eight conditions (P<0.05). In terms of the strength ratios, strong association was found between electrical activity and moment production in the subscapularis and infraspinatus (r(2)=0.95 and 0. 72, respectively) at the low and high angular velocities. CONCLUSIONS: Prior to actual rotation of the shoulder joint, normal recruitment of the rotator cuff and biceps is characterized by a non-specific presetting phase which is mainly directed at enhancing the joint 'stiffness' and hence its stability. Once movement is in progress, the EMG patterns of these muscles become movement specific and are correlated with the resultant moment. RELEVANCE: Muscular dysfunction relating to delayed onset activity or altered activation patterns, due to pain, perturbed mechanics or disturbed neural activation have been implicated as concomitant factors in other joint associated pathologies. Through highlighting the role of the rotator cuff in shoulder joint rotations, this study lends further support to the argument that a parallel situation may prevail with respect to shoulder joint dysfunction. This could lead to the development of rehabilitation protocols aimed specifically at redressing such dysfunction.

Biomedical considerations and clinical patterns related to disorders of the glenoid labrum in the predominantly stable glenohumeral joint.

SUMMARY. The roles of the glenoid labrum and long head of biceps are reviewed together with their significance in stability of the glenohumeral joint. Clinical presentations related to disorders of the glenoid labrum and long head of biceps not associated with frank instability but commonly responsible for dysfunction in the athletic shoulder, are reviewed from the perspective of pertinent anatomical, biomechanical and kinematic knowledge. Copyright 1996 Harcourt Publishers Ltd.