Radiographic parameter(s) influencing functional outcomes following angular stable plate fixation of proximal humeral fractures

Purpose Radiographic parameters which correlate with poor clinical outcome after proximal humeral fractures could be helpful indicators to answer the question which patients should be followed up closer. Moreover, during surgery, radiographic parameters correlating with unfavourable outcome should be avoided. The primary aim of the study was to compare radiographic measurements between the injured and the contralateral, uninjured shoulder. The secondary aim was to correlate these radiographic parameters with post-operative shoulder function. Methods Fifty-eight patients (age: 55.6 ± 14.4 years, age at surgery) following angular stable plate fixation of a proximal humeral fracture (2-part fractures according to Neer: 24, 3-part: 25, 4-part: 9) were included in this retrospective cohort study. All patients were followed up at least six years (7.9 ± 1.4 after surgical intervention). During follow-up examination, the Constant score (CS) was assessed, and radiographs of both shoulders were taken. Radiographs were analyzed regarding lateral humeral offset, distance between tuberculum and head apex, head diameter, head height, perpendicular height, perpendicular center, vertical height, and angles between head and humeral shaft (CCD and HSA). These parameters were compared between the injured and uninjured shoulder. The cohort was divided in two groups: patients with a CS category of excellent/good and satisfying/worse. Both groups were tested regarding differences of demographic and radiographic parameters. Results The distance between tuberculum and head apex (2.6 ± 3.4 mm vs. 4.3 ± 2.1 mm; p = 0.0017), the CCD (123.1 ± 12.9° vs. 130.1 ± 7.3°; p = 0.0005), and the HSA (33.1 ± 12.8° vs. 40.1 ± 7.3°; p = 0.0066) were significantly smaller on the treated shoulder compared to the uninjured side. Patients reached a Constant score of 80.2 ± 17.4 (95% CI 75.6–84.8) points. Regarding outcome categories of the Constant score, 46 patients had a good to excellent outcome, and 12 patients had a satisfying or bad outcome. The comparison of these groups revealed that patients with inferior outcome in the long-term follow-up were older, female, had a more complex fracture type (AO classification), smaller lateral humeral offset, smaller head diameter and height, lower perpendicular height, and lower CCD and HSA angles. Conclusion If the abovementioned parameters cannot be restored sufficiently during surgery, (reversed) shoulder arthroplasty might be a better solution to reach good post-operative outcome. Moreover, patients presenting these radiographic characteristics in the follow-up, older patients, and patients with a more complex fracture type should be followed up closer to possibly prevent poor shoulder function. Trial registration: 83 250/2011BO2

The effect of load and plane of elevation on acromial stress after reverse shoulder arthroplasty

Background Acromial fractures are a substantial complication following reverse shoulder arthroplasty, reported to affect up to 7% of patients. Previous studies have shown that implant placement affects acromial stress during elevation of the arm in the scaption plane. The purpose of this study was to investigate the results of arm loading and variation in plane of elevation on acromial stresses. Methods Nine elevation angles (0°–120°), in three planes of elevation (abduction (0°), scaption (30°), and forward elevation (60°)), and three hand loads (0, 2.5, 5 kg) were investigated. Finite element models were generated using computed tomography data from 10 cadaveric shoulders (age 68 ± 19 yrs) to determine acromial stress distributions. Models were created for a lateralized glenosphere (0, 5, 10 mm), inferiorized glenosphere (0, 2.5, 5 mm), and humeral offset (−5, 0, 5 mm). Results For all planes of elevation (0°, 30°, 60°) and hand loads (0, 2.5, 5 kg) investigated, glenoid lateralization consistently increased acromial stress, glenoid inferiorization consistently decreased acromial stress, and humeral offset proved to be insignificant in altering acromial stress. Abduction resulted in significantly higher peak acromial stresses (p = 0.002) as compared to scaption and forward elevation. Conclusions In addition to implant position and design, patient activity, such as plane of elevation and hand loads, has substantial effects on acromial stresses. Level of evidence Basic science study

Radiologic Comparison of Humeral Position according to the Implant Designs Following Reverse Shoulder Arthroplasty: Analysis between Medial Glenoid/Medial Humerus, Lateral Glenoid/Medial Humerus, and Medial Glenoid/Lateral Humerus Designs

BACKGROUND: The currently available reverse shoulder arthroplasty (RSA) designs can be classified into medial glenoid/medial humerus (MGMH), lateral glenoid/medial humerus (LGMH), and medial glenoid/lateral humerus (MGLH) prosthesis designs. The purpose of this study was to radiologically analyze the effect of different RSA designs on humeral position following RSA.METHODS: A total of 50 patients who underwent primary RSA were retrospectively analyzed. Among 50 patients, 33 patients (group A: MGMH) underwent RSA with Aequalis system (Wright, Inc, Bloomington, MN, USA), 6 (group B: LGMH) with Aequalis system using bony increased offset, and 11 (group C: MGLH) with Aequalis Ascend Flex system. The acromiohumeral distance, acromioepiphyseal distance (AED), lateral humeral offset (LHO), LHO from the center of rotation (LHO(COR)), and deltoid length were radiologically measured to quantify the distalization and lateralization of the humerus.RESULTS: The increment in postoperative AED was 19.92 ± 3.93 mm in group A, 24.52 ± 5.25 mm in group B, and 25.97 ± 5.29 mm in group C, respectively (p=0.001). The increment in postoperative LHO was 0.13 ± 6.30 mm, 8.00 ± 12.14 mm, and 7.42 ± 6.88 mm, respectively (p=0.005). The increment in postoperative LHOCOR was 20.76 ± 6.06 mm, 22.04 ± 5.15 mm, and 28.11 ± 4.14 mm, respectively (p=0.002).CONCLUSIONS: The radiologic analysis of the effect of different RSA designs on humeral position following RSA showed significant differences in the increment in postoperative AED, LHO, and LHO(COR) between the 3 groups. Therefore, MGLH design seems to be more effective for humeral distalization and lateralization compared to original Grammont design.