Does surgery for instability of the shoulder truly stabilize the glenohumeral joint?: A prospective comparative cohort study

Abstract

Despite the fact that surgery is commonly used to treat glenohumeral instability, there is no evidence that such treatment effectively corrects glenohumeral translation. The purpose of this prospective clinical study was to analyze the effect of surgical stabilization on glenohumeral translation.Glenohumeral translation was assessed in 11 patients preoperatively and 1 year postoperatively following surgical stabilization for anterior shoulder instability. Translation was measured using optical motion capture and computed tomography.Preoperatively, anterior translation of the affected shoulder was bigger in comparison to the normal contralateral side. Differences were significant for flexion and abduction movements (P < 0.001). Postoperatively, no patients demonstrated apprehension and all functional scores were improved. Despite absence of apprehension, postoperative anterior translation for the surgically stabilized shoulders was not significantly different from the preoperative values.While surgical treatment for anterior instability limits the chance of dislocation, it does not seem to restore glenohumeral translation during functional range of motion. Such persistent microinstability may explain residual pain, apprehension, inability to return to activity and even emergence of dislocation arthropathy that is seen in some patients. Further research is necessary to better understand the causes, effects, and treatment of residual microinstability following surgical stabilization of the shoulder.

Figure 1

Apprehension could be related to (A) central nervous system sequelae, (B) peripheral neurological, muscular or capsular/ligamentous lesions consecutively to dislocation, or (C) mechanical instability as micromovements.

Figure 2

Examples of computed postures on a right shoulder showing the markers setup (small colored spheres) and a virtual skeleton used to better visualize the motion as a whole: (A) maximum flexion, (B) maximum abduction in the scapular plane, (C) maximum external rotation with elbow at side, (D), (E), and (F) show a zoom in the shoulder for each posture (A), (B), and (C), respectively.

Figure 3

(A) Definition of the glenoid coordinate system used in this study. (B) Schematic representation of glenohumeral subluxation (C = center of the humeral head, R = radius of the width or height of the glenoid surface, T = translation of the humeral head center). Left: the ratio is 40%, there is no instability. Right: the ratio is >50%, instability is noted. Image reproduced from Lädermann et al^[24] with permission.

Figure 4

STARD flow diagram.