Strength and motion after hemiarthroplasty in displaced four-fragment fracture of the proximal humerus - 27 patients followed for 1-6 years

We evaluated 27 patients with shoulder hemiarthroplasty after displaced four-fragment fracture of the proximal humerus after mean 4 (1-6) years. Isometric strength measurements (Kintrex) and three-dimensional motion analysis (Elite-System) were performed on the operated and unoperated shoulders. Clinical assessment was based on Constant's score and Neer's scoring system. The isometric strength of the operated and unoperated sides were 22 (SD 8.6) Nm and 24 (SD 5.9) Nm in abduction and 48 (SD 14) Nm and 65 (SD 21) Nm, respectively in adduction (the latter was statistically significant). Motion analyses at follow-up showed a mean reduction in glenohumeral movement. Increases in acceleration and deceleration of the acromion at the operated side were noted, indicating a change in glenohumeral rhythm during maximal abduction. The Constant score was 45 (SD 15) points with a significant reduction in the range of motion. 15 patients had some degree of heterotopic ossification. On the basis of our findings, the impaired function seems to be caused by reduced glenohumeral mobility rather than muscle strength. We also found a better outcome after early than late hemiarthroplasty.