Low Survival Rates of Stemmed Hemiarthroplasty and Reverse Arthroplasty After Treatment for Proximal Humerus Fracture Sequelae. A Register-Based Study from the Nordic Arthroplasty Register Association

Abstract

were implanted on a Sawbone® according to the manufacturer guidelines. All six implant systems were evaluated using a smaller and a larger glenosphere. The lowering and medialisation of the humerus with respect to the scapula after implantation of the implant was determined in neutral position (0 elevation and 0 internal rotation in scapular plane).The ROM was determined by the minimal and maximal elevation in the scapular and in 90 humeral plane, as by the maximal internal and external rotation at 30 and 60 elevation (glenoid plane) until bony contact.Results: With all implant systems the humerus was significantly lowered with respect to the scapula (p<0.05, mean: 38.8mm, SD: 4.4, range: 30.9; 43.6mm). With larger glenospheres, this lowering was significantly higher compared to smaller glenospheres (r¼ 0.94, p<0.05, mean: 2.1mm, SD:1.6).The humerus shifted medial (p<0.05, mean: 7.1mm, SD: 6.2) with a range of -1.5mm to 17.2 mm. The medialisation is positively correlated with the size of the glenosphere (r¼0.98, p<0.05, mean: 1.2mm, SD: 1.3). The total range of elevation depends on the orientation of the humerus in the vertical plane. The total range of elevation in the scapular plane ranges between 59.2 and 100.4 , whereas it ranges between 18.3 and 54.8 in the 90 humeral plane. The starting point, defined as the minimal elevation varies between 4.9 and 35 in the scapular plane, whereas it varies between 21.4 and 35.6 in the 90 humeral plane. The implantation of a large glenosphere resulted in a significant (p<0.05) enhancement of the total range of elevation and a reduction of the minimal elevation in both scapular an 90 humeral plane.Conclusions: There exists a wide variation in the measured parameters (position humerus, ROM) between the six most frequent implanted prosthesis. A larger glenosphere results in a better ROM in all different brands. These significant differences in ROM can be clinically important as it can result in impingement and restricted functionality of the humeroscapular joint.