Electromyographic analysis during pull,forward punch,elevation and overhead throw after conservative treatment or capsular shift at patient with multidirectional shoulder joint instability

PurposeThe aim of this study was to compare the muscle activity of patients with multidirectional instability treated in a conservative or complex manner (capsular shift with postoperative rehabilitation) and the muscle activity of stable shoulder joints before and after treatment during pull, push, and elevation of upper extremities and during overhead throw.ScopeThe study was carried out on 34 patients with multidirectional shoulder instability treated non-operatively, on 31 patients with multidirectional shoulder instability treated operatively, and on 50 healthy subjects. Signals were recorded by surface EMG from eight different muscles. The mean and standard deviation of the maximum amplitude of normalized voluntary electrical activity for the different movement types and time broadness values during overhead throw were determined for each muscle in all groups and compared with each other.ConclusionThe centralization of the glenohumeral joint and the reduction of instability is attempted to be ensured by the organism through increasing the role of rotator cuff muscles (p = 0.009) and decreasing the role of the deltoid, biceps brachii, and pectoralis maior muscles (p = 0.007). At patients after short-term and long-term conservative treatment, the maximum amplitude of normalized voluntary electrical activity of stabilizer muscles is significantly higher (p = 0.006), and that of accelerator muscles is significantly lower (p = 0.005) and the time broadness is significantly longer (p = 0.01) than that of the control group. At patients after complex treatment (open capsular shift with postoperative conservative rehabilitation) the characteristic of the muscle pattern is similar (p = 0.19) to the control group.The complex treatment resolves the labral ligamentous abnormalities by operative treatment and restores the impaired muscular control by postoperative rehabilitation, whereas the conservative treatment restores only the muscular control.