2025 ISAKOS Biennial Congress ePoster
Quantifying the Difference in Glenoid Component Position between Total Shoulder Arthroplasty and Reverse Shoulder Arthroplasty
Christopher Child, MD, Brisbane, QLD AUSTRALIA
Luke Gilliland, BEng, Brisbane, QLD AUSTRALIA
Marine Launay, MEng, Greenslopes, QLD AUSTRALIA
Kristine R. Italia, MD, FPOA, Quezon City, Metro Manila PHILIPPINES
Roberto Pareyon MEXICO
Asma Salhi, PhD, Brisbane, QLD AUSTRALIA
Sarah L Whitehouse, PhD, Brisbane, Queensland AUSTRALIA
Jashint Maharaj, MBBS, FRSPH, Brisbane, QLD AUSTRALIA
Kenneth Cutbush, MBBS, FRACS, FAOrthA, Spring Hill, QLD AUSTRALIA
Ashish Gupta, MBBS, MSc, FRACS, FAORTHOA, Brisbane, QLD AUSTRALIA
Queensland Unit for Advanced Shoulder Research (QUASR), Brisbane, QLD, AUSTRALIA
FDA Status Not Applicable
Summary
The purpose of this study was to quantify the difference between optimal TSA and RSA glenoid implant positioning on 3-Dimensional (3D) segmented models.
ePosters will be available shortly before Congress
Abstract
Introduction
The revision of Anatomic Total Shoulder Arthroplasty (TSA) implants to Reverse Shoulder Arthroplasty (RSA) designs is becoming increasingly common as the number of arthroplasties in younger patients rises. Different convertible shoulder systems have been proposed to revise a TSA to RSA. However, switching from TSA to RSA is not possible in all cases given the high variability of glenoid and humeral components’ size and shape. To the best of our knowledge, there is limited literature comparing the glenoid component positioning for shoulder arthroplasty. Thus, the purpose of this study was to quantify the difference between optimal TSA and RSA glenoid implant positioning on 3-Dimensional (3D) segmented models.
Methods
25 patients who underwent primary RSA procedures were recruited for this study. A 3D preoperative planning software was used to reconstruct the 3D models of scapula and humerus from CT scans for each patient. Retrospectively, TSA and RSA glenoid components were positioned on each of the patient’s scapulae in the same planning software by a shoulder orthopaedic surgeon and an orthopedically trained surgical fellow. Small, medium, and large sized generic TSA glenoid implants were available. The scapulae were split into three groups according to their glenoid size. Simulated guidewires were drafted based on the implant position and orientation, along with the projected guidewire entry point on the glenoid surface. The superior-inferior (S-I) distance between the projected TSA and RSA guidewire entry points was compared for each scapula.
Results
Small, medium and large glenoid groups consisted of 6, 9 and 10 scapulae respectively, with a 72% agreement rate with the second rater. Correlating average glenoid width and height (w x h) for each group was 23.2mm x 32.3mm, 31.6mm x 38.1 mm and 33.5mm x 43.3mm. The mean (± SD) superior-inferior distance from TSA to RSA guidewire entry position is 3.0mm ± 0.4mm, 5.1mm ± 1.3mm and 6.1mm ± 1.7mm respectively for small, medium and large glenoids when compared to 25mm RSA baseplates.
Conclusion
In this study, we quantify the variation between implant position for TSA and RSA glenoid components and investigate the subsequent effect the glenoid and implant size. The ideal RSA implant position is inferior with respect to the TSA position. Larger glenoids present more disparity between TSA and RSA implant position which is minimally affected by increasing the RSA implant size.