Electromyographic and kinematic study of reverse total shoulder arthroplasty: an observational prospective cohort study.

BACKGROUND: Reverse total shoulder arthroplasty (RTSA) procedures have significantly increased in the last decade as an alternative to the current treatments for cuff-tear arthropathy. Since Grammont's theory in 1987, few data about the in vivo kinetics of the shoulder-girdle musculature in patients with RTSA have been available. The goals of this study are to (1) describe the contribution of principal muscles around the shoulder by electromyography and (2) access the range of motion of 5 movements of patients with RTSA compared with normal shoulders. METHODS: This is an observational prospective cohort study of 21 patients divided into 11 patients with RTSA and 10 controls. The muscular activity was recorded with bipolar cutaneous electrodes, whereas the range of motion was synchronized and recorded by 8 motion cameras. Five movements (flexion, abduction, neutral external rotation, external rotation in 90° of abduction, and internal rotation in 90° of abduction) were studied. RESULTS: The upper trapezius is the main activator in all directions with early and constant activity (P < .01). The latissimus dorsi demonstrates increased muscular activity in internal rotation (P < .01) as well as the posterior deltoid in external rotation in the RTSA group compared with control (P < .01). CONCLUSION: RTSA shoulder muscle activation is significantly different than in normal shoulders. The significant contribution of the trapezius in all directions, latissimus dorsi in internal rotation, and posterior deltoid in external rotation has never been described within the same study until today. New rehabilitation protocols targeting those muscles could demonstrate better and more homogeneous results and increase patient satisfaction.

Osteoarticular distal clavicle autograft for the management of instability-related glenoid bone loss: an anatomic and cadaveric study.

BACKGROUND: The reconstructive options for instability-related anterior glenoid bone loss include iliac crest autograft, allograft, or coracoid transfer. The use of distal clavicle autograft (DCG) has also been described. The purpose of this imaging and cadaveric study was to examine the dimensions, morphology, and bone density of the DCG and compare it with the Latarjet procedure. METHODS: We used 49 computed tomography scans from patients with anterior glenoid bone loss to measure the distal clavicle dimensions and bone density. Four glenoid reconstructions were simulated to compare techniques: DCG inferior surface toward glenoid (DCG inferior), DCG superior, classic Latarjet, and congruent-arc Latarjet. In addition, the morphology of the DCG was assessed on computed tomography and confirmed in 27 cadavers. RESULTS: The mean width of the DCG (11 mm) was significantly greater (P < .001) than that of the classic Latarjet orientation (9 mm) but less (P = .002) than that of the congruent-arc orientation (12 mm). The DCG had a lower bone density than the coracoid (P < .001). The mean articular surface area of the DCG-inferior orientation was 208 mm2, which was greater (P = .013) than that of the DCG-superior orientation (195 mm2) and not significantly different (P = .44) than that of the classic Latarjet orientation (214 mm2). The surface area of the congruent-arc orientation was greater (285 mm2, P < .001) than that of all other graft orientations. The DCG-inferior orientation was able to reconstruct 22% of the glenoid articular surface; DCG-superior orientation, 21%; classic Latarjet orientation, 23%; and congruent-arc orientation, 30%. Three DCG morphologies were identified: square (34%), trapezoidal (53%), and rounded (13%). CONCLUSIONS: The distal clavicle osteoarticular graft was able to reconstruct 22% of the glenoid face. Three morphologies of the distal clavicle were identified, with the square and trapezoidal morphologies most amenable for glenoid reconstruction.