Recent literature has shown that RSAs successfully improve pain and functionality, however variability in range of motion and high complication rates persist. Biomechanical studies suggest that tensioning of the deltoid, resulting from deltoid lengthening, improves range of motion by increasing the moment arm. This study aims to provide clinical significance for deltoid tensioning by comparing postoperative range of motion measurements with deltoid length for 93 patients. Deltoid length measurements were performed radiographically for 93 patients. Measurements were performed on both preoperative and postoperative x-rays in order to assess deltoid lengthening. The deltoid length was measured as the distance from the infeolateral tip of the acromion to the deltoid tuberosity on the humerus for both pre- and post- x-rays. For preoperative center of rotation measurements, the distance extended from the center of humeral head (estimated as radius of best fit circle) to deltoid length line. For postoperative measurements, the distance was from the center of glenosphere implant to deltoid length line. Forward flexion and external rotation was measured for all patients.Introduction
Methods
There has been increased focus on understanding the risk factors associated with scapular notching in reverse shoulder arthroplasty (RSA). The purpose of this study is to evaluate the effect of scapular morphology and surgical technique on the occurrence of scapular notching using the notching index as a comprehensive predictive tool. Ninety-one patients treated with a primary RSA were followed for a minimum of 24 months. Using a previously published notching index formula ((PSNA × 0.13) + (PGRD)), a notching index value for all patients was calculated. Radiographic assessment of patients were grouped by Nerot grade of scapular notching, group mean differences for prosthetic scapular neck angle (PSNA), peg glenoid rim distance (PGRD), preoperative scapular neck angle (SNA), notching index and clinical outcomes were compared.Background
Methods
The optimal degree of conformity between the glenoid and humeral components in cemented total shoulder arthroplasty (TSA) has not been established. Glenoid component stability is thought to be at risk due to the “rocking-horse” phenomenom, which, can lead to increased micromotion and loosening in response to humeral head edge loading. The goal of this biomechanical study is to investigate the influence of glenohumeral mismatch on bone-implant interface micromotion in a cemented glenoid implant model. Twenty-Five cemented glenoid components (Affiniti, Tornier, Inc., Bloomington, MN, USA) were implanted in polyurethane foam biomechanics testing blocks. Five glenoid sizes, 40 mm, 44 mm, 48 mm, 52 mm and 55 mm (n = 5 per glenoid size), were cyclically tested according to ASTM Standard F-2028-08. A 44 mm humeral head (Affiniti, Tornier, Inc., Bloomington, MN, USA) was positioned centrally within the glenoid fixed to a materials testing frame (MTS Mini-Bionix II, Eden Prairie, MN, USA). Phase I testing (n = 3 per glenoid size) involved a subluxation test for determination of the humeral head translation distance which would be used for phase II cyclic testing. During cyclic loading, the humeral head was translated ± distance for 50,000 cycles at a frequency of 2 Hz, simulating approximately 5 years of device use. Glenoid compression, distraction, and superior-inferior glenoid translation were measured throughout testing via two differential variable reluctance transducers.Purpose:
Methods:
Total shoulder arthroplasty is technically demanding in regards to implantation of the glenoid component, especially in the setting of increased glenoid deformity and posterior glenoid wear. Augmented glenoid implants are an important and innovative option; however, there is little evidence accessible to surgeons to guide in the selection of the appropriate size augmented glenoid. Solid computer models of a commercially available augmented glenoid components (+3, +5, +7) contained within the software allowed for placement of the best fit glenoid component within the 3D reconstruct of each patient's scapula. Peg perforation, amount of bone reamed and amount of medialization were recorded for each augment size.Background
Methods
