Monica Khanna MBBS, FRCR, Presenter: Nothing to Disclose

Rodger Emery, Abstract Co-Author: Nothing to Disclose

Peter Reilly, Abstract Co-Author: Nothing to Disclose

Amanda Walker FRCR, Abstract Co-Author: Nothing to Disclose

Glenoid component aseptic loosening is an important issue post total shoulder arthroplasty (TSA). Understanding the biomechanics of the reconstructed glenohumeral joint and identifying factors that contribute to glenoid component loosening are ongoing. Glenoid malpositioning can lead to premature glenoid loosening. We describe the Thomas Gregory Position and its advantage over normal shoulder CT in the evaluation of glenoid component periprosthetic osteolysis and prosthetic placement.  

12 patients post TSA (2 bilateral) underwent a CT in the Thomas Gregory position, a lateral decubitus position with maximal flexion at the glenohumeral articulation to ensure metal artefact from the humeral head is above the glenoid. A retrospective review of each study was performed to evaluate for periprosthetic osteolysis according to the Molé criteria. Glenoid component placement was evaluated for version, inclination, rotation, and anterior posterior offset.  

13 TSAs were imaged. Molé classification composite score for periprosthetic lucency corresponded to possible or definite loosening in all symptomatic TSAs and no loosening in all asymptomatic patients. The glenoid component in 72% of symptomatic TSAs was retroverted (8.5-21 degrees), compared to 75% in the asymptomatic group (12-17 degrees). Inclination varied from 20 degrees superiorly inclined to 16 degrees inferiorly inclined. Offset distance was between 4.5mm posterior to 12mm anterior offset.  

The Thomas Gregory Position enables accurate CT evaluation for periprosthetic lucency and detailed information on placement of the glenoid component, factors important to the orthopaedic surgeon for evaluation of the painful shoulder prosthesis requiring revision surgery. These factors also provide prognostic evaluation of the asymptomatic shoulder prosthesis.

The Thomas Gregory Position enables accurate CT evaluation for periprosthetic lucency and positioning of the glenoid component post TSA, factors important in assisting the orthopaedic surgeon.

Khanna, M, Emery, R, Reilly, P, Walker, A, CT Evaluation of the Glenoid Component Post Total Shoulder Arthroplasty Utilizing the Thomas Gregory Position: Experience in 12 Patients.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11001404.html