CT EVALUATION OF CEMENTLESS GLENOID PROSTHESIS OSSEOINTEGRATION AND STABILITY IN TOTAL SHOULDER ARTHROPLASTY

In total shoulder arthroplasty a significant measure of long-term survivorship of the implant is rooted in the osseointegration of the glenoid component. The Mathys Affinis short vitamys implant brings similar properties seen in the RM pressfit acetabular cup to the shoulder containing a monobloc porous coated construction with osseointegrative properties. Using Computerised Tomography in this prospective cohort study, at 12 months we evaluated peri-peg osteolysis, independent peg osseointegration and migration of the glenoid component. As these are normally assessed on plane radiographs, we developed the Computed Tomography Fixation Integrity Score (CT-FIS) as an evaluation framework defining 4 grades of stability: stable fixation (0), “At risk / close review” (1), “Radiographically loose” (2) and grossly unstable (3). These grades are formed using revision arthroplasty definitions from CT based measurements of lucency incorporating Lazarus grading. Of 29 patients (mean age 67); 17 right, 13 left (1 with bilateral replacements), 20 were available for analysis. At one year, 85% of patients (17) demonstrated Grade 0 and 15% (3) Grade 1 using CT-FIS. No implants were radiographically loose. One patient scan showed osteolysis with cortical breach, but all showed at least partial osseointegration at superior and/or inferior pegs. No component migration was observed. This implant demonstrates early reliable osseointegration and low rates of lucency. The use of CT allows for volumetric assessment of implant success and development of our grading system will allow for quantifiable longitudinal analysis previously limited to two-dimensional radiographs.