Evaluation of periprosthetic bone mineral density and postoperative migration of humeral head resurfacing implants: two-year results of a randomized controlled clinical trial

Abstract

Implant migration, bone mineral density (BMD), length of glenohumeral offset (LGHO), and clinical results were compared for the Copeland (Biomet Inc, Warsaw, IN, USA) and the Global C.A.P. (DePuy Int, Warsaw, IN, USA) humeral head resurfacing implants (HHRIs). The study randomly allocated 32 patients (13 women), mean age 63 years (range, 39-82 years), with shoulder osteoarthritis to a Copeland (n = 14) or Global C.A.P. (n = 18) HHRI. Patients were monitored for 2 years with radiostereometry, dual-energy X-ray absorptiometry, Constant Shoulder Score (CSS), and the Western Ontario Osteoarthritis of the Shoulder Index (WOOS). LGHO was measured preoperatively and 6 months postoperatively. At 2 years, total translation (TT) was 0.48 mm (standard deviation [SD], 0.21 mm) for the Copeland and 0.82 mm (SD, 0.46 mm) for the Global C.A.P. (P = .06). Five HHRI were revised, and in the interval before the last follow-up (revision or 2 years), TT of 0.58 mm (SD, 0.61 mm) for revised HHRI was higher (P = .02) than TT of 0.22 mm (SD, 0.17 mm) in nonrevised HHRI. A comparison of TT at the last follow-up (revision or 2 years) found no difference between the HHRIs (P = .12). Periprosthetic BMD decreased initially but increased continuously after 6 months for both HHRIs. At 2 years, BMD was 48% higher around the Copeland HHRI (P = .005). The mean difference in LGHO was significantly higher for the Copeland than for the Global C.A.P. HHRI (P = .02). Clinical results evaluated with CSS and WOOS improved over time for both implant groups (P < .01), with no differences between the groups. Both implants had only little migration and good clinical results. Periprosthetic BMD and LGHO both increased for the Copeland HHRI more than for the Global C.A.P HHRI.