Theoretical model of the effect of combined glenohumeral bone defects on anterior shoulder instability: A finite element approach

Abstract

ABSTRACT:The presence of either a Hill-Sachs or a bony Bankart defect has been indicated as a possible cause of subluxation and anterior shoulder dislocation. Previous studies investigated only the effects of isolated humeral or glenoid defects on glenohumeral instability. We investigated the effects on shoulder stability of both glenoid and humeral defects in the glenohumeral joint. A computerbased finite element approach was used to model the joint. A generic model was developed for cartilage and bone of the glenoid and humerus, using previously published data, and experiments were analyzed using static analysis with displacement control in the anterior-inferior direction. Simulations were run with a 50-N compressive load in the presence of both isolated and combined defects to analyze reaction forces and distance to dislocation. The distance to dislocation for normal joint was 13.6 mm at 908 abduction, which reduced to 9.7, 0, and 0 mm for largest isolated humerus defect, glenoid defect, and certain combined defects, respectively. For combined defects, stability ratio was decreased to 0% from 43%. Our results suggest that in the setting of combined bone defects, stability may be reduced more than what is known for isolated defects alone.

Influence of Combined Hill-Sachs and Bony Bankart Defects on Range of Motion in Anterior Instability of the Shoulder in a Finite Element Model

“…16 The 2 humerothoracic positions selected for simulation of joint stability were 45 and 90 , representing the testing angles for abduction of 30 and 60 of glenohumeral abduction, respectively. 7,12 In addition, rotation angles were tested between the range of 40 of internal rotation (IR) and 60 of external rotation (ER).…”

“…To our knowledge, only a single study investigated the combined defects at 45 and 90 abduction angles only and showed that instability is increased because of the combined defects. 12 Our study aimed to quantify the effect of different size combinations of Hill-Sachs defects and bony Bankart defects on shoulder instability for a broad range of motion. We hypothesized that the bony Bankart lesion and the Hill-Sachs defect would differently contribute to shoulder instability with respect to the arm position.…”

Iliac bone grafting of the intact glenoid improves shoulder stability with optimal graft positioning

“…26 The point of dislocation was determined as the position where the most medial part of the humeral head reaches the most lateral part of the glenoid surface. 30,49 …”

Acute Shoulder Trauma: What the Surgeon Wants to Know

“…Indications vary with patient and surgeon factors, but a defect that affects over 20%-25% of the glenoid surface area tends to be associated with higher rates of redislocation following repair of soft tissue only (19). Furthermore, concomitant bony Bankart and Hill-Sachs lesions reduce stability more than either in isolation (22).…”