Background-Hill-Sachs lesions are often present with recurrent shoulder instability and may be a cause of failed Bankart repair.

Increases to the posterior tibial slope can lead to an anterior shift in tibial resting position. However, the effect of this shift on anterior cruciate ligament (ACL) strain has not been investigated sufficiently. This study examined the relationship between increased tibial slope and ACL strain, as well as the subsequent kinematics of the tibiofemoral joint. We hypothesized increases in slope would shift the tibia anterior relative to the femur and increase ACL strain. ACL strain measurements and tibiofemoral kinematics were compared for 5 intact and experimental knees subject to anterior opening wedge osteotomy. Combinations of both compressive and AP loading were applied. As slope increased, the resting position of the tibia shifted anteriorly, external tibial rotation increased, and tibial translation remained unchanged. Contrary to our hypothesis, ACL strain decreased. The clinical implication of these findings is that alterations to the posterior tibial slope should not increase strain in the ACL.

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In shoulders with combined humeral head and glenoid defects, bony reconstruction may be indicated for defect sizes smaller than would be indicated for either defect found in isolation.

This is one of the only studies to date that has investigated both the reliability and accuracy of multiple indicators and quantification methods that evaluate glenoid bone loss in anterior glenohumeral instability. These data are critical to ensure valid methods are used for preoperative assessment and to determine when a glenoid bone augmentation procedure is indicated.

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.

In our evaluation of 193 pitchers examined during their preseason physical examinations, we identified a statistically significant association between decreased total arc of motion, decreased shoulder strength, and GIRD.