Biomechanical properties of the glenohumeral joint capsule in hemiplegic shoulder pain

BackgroundAlthough many hemiplegic shoulder patients have been suffering from limited range of motion, it is not fully established whether the pathologic biomechanics are same in hemiplegic shoulder pain and adhesive capsulitis. Therefore we aimed to investigate biomechanical properties of glenohumeral joint capsules of hemiplegic shoulder pain with limited range of motions.MethodsParticipants were 14 patients with hemiplegic shoulder pain, 10 controls, and 42 adhesive capsulitis patients matched with the hemiplegic shoulder pain group for sex, age, and range of motion. Demographic data, clinical variables, and sonographic findings were comparable between hemiplegic shoulder pain and adhesive capsulitis groups. We compared capsular capacity, maximal pressure, and capsular stiffness of glenohumeral joint capsule among the 3 groups.FindingsHemiplegic shoulder pain and adhesive capsulitis groups had smaller capsular capacity and higher maximal pressure than controls. The capsular stiffness of hemiplegic shoulder pain group was higher than that of controls (P = 0.001) but lower than that of adhesive capsulitis group (P < 0.001).InterpretationThe stiffness of glenohumeral joint capsules in hemiplegic shoulder pain and adhesive capsulitis patients was substantially higher than that in controls, suggesting that hemiplegic shoulder pain patients had stiffer capsules as adhesive capsulitis patients did although the severities were different. This finding implicates that hemiplegic shoulder pain may share common pathologic properties of tighter capsules with adhesive capsulitis. However, there may be additional mechanisms contributing to range of motion limitation in hemiplegic shoulder pain because capsular stiffness in those patients was not as severe as that in adhesive capsulitis patients with similar range of motion limitation.