Effect of baseplate positioning on fixation of reverse total shoulder arthroplasty

Abstract

Background: The glenoid component in reverse total shoulder arthroplasty is recommended to be positioned inferiorly or with a downward tilt with the intention of reducing scapular notching. However, it is still unclear whether modifying the position of the glenoid prosthesis affects implant stability. The aim of this study was to determine the association between implant positioning and glenoid prosthesis fixation using Grammont reverse total shoulder arthroplasty. Methods: Four positions for the glenoid prosthesis were studied using the finite element method. The glenosphere was positioned as follows: 1) in the middle of the glenoid fossa, 2) flush with the inferior glenoid rim, 3) with an inferior overhang, 4) with a 15° inferior inclination. Bone-prosthesis micromotions and strain-induced bone adaptations were quantified during five daily activities. Findings: When the glenoid component was tilted inferiorly, the activities producing anteriorposterior shear forces (e.g. standing up from an armchair) caused an increase in peak micromotions. In the lateral-middle glenoid, inferior positioning caused a 64.6% reduction in bone apparent density. In the lateral-inferior glenoid, central positioning led to the most severe bone resorption, reaching 43.9%. Interpretation: Reducing activities which generate anterior-posterior shear forces on the shoulder joint will increase bone formation and may improve the primary stability of the implant when fixed in the position with an inferior tilt. Postoperative bone resorption is highly dependent on implant positioning. Understanding the relationship between bone resorption and implant positioning will help surgeons improve the long-term stability of reverse total shoulder arthroplasty.

Clinical Importance of Graft Integrity in Arthroscopic Superior Capsular Reconstruction Using a Minimally Invasively Harvested Midthigh Fascia Lata Autograft: 3-Year Clinical and Magnetic Resonance Imaging Outcomes

“…5 ASCR provides a fulcrum to the deltoid lever arm without compromising the native glenohumeral center of rotation, which allows the shoulder girdle to function in a physiological balance and prevents several unsolved mechanical problems of current reverse total shoulder arthroplasty implants that are used in the treatment of IRCTs. 2,20,40,48,52…”

“…5 ASCR provides a fulcrum to the deltoid lever arm without compromising the native glenohumeral center of rotation, which allows the shoulder girdle to function in a physiological balance and prevents several unsolved mechanical problems of current reverse total shoulder arthroplasty implants that are used in the treatment of IRCTs. 2,20,40,48,52 This is the first study to date to report the reliability statistics for the MRI outcomes of graft integrity, fatty infiltration, and atrophy of the rotator cuff muscles after ASCR. 11,12,28,29,36,37,41,50 The proportion of complete graft tears was 21.1% at 3 years, which was the most reliable MRI outcome of the present study, whereas the proportion of partial tears was less reliable and ranged from 10.5% to 21.1% across the 3 raters.…”

Tomographic Analysis of Positioning of Reverse Baseplates Positioning

“…The positioning of the baseplate in line with the lower border of the glenoid bone is implicated in reducing notching, decreasing bone resorption, and consequently improving the implant durability. 36 – 38 The Exactech brand baseplate used in our study is recommended to be positioned on the lower edge of the glenoid. We found that the surgeons’ ability to correctly position the baseplate in relation to the inferior glenoid, even without intraoperative 3D technology, is excellent (Radiologist 1 and 2 measurements reported 97.1% and 95.7% respectively, and were not influenced by the GBD).…”

Complications of Reverse Total Shoulder Arthroplasty: A Computational Modelling Perspective

“…Computational modeling of RTSA facilitates estimation of muscle and joint loading, which is currently impossible to measure non-invasively in vivo. Modeling and simulation of RTSA has played a critical role in guiding implant positioning and surgical technique [19][20][21][22], prosthesis selection [23,24], implant design [25,26], and post-operative rehabilitation prescription [27,28]. To date, most modeling and simulation tools require high levels of expertise and are generally restricted to the research setting.…”