Comparison of bone removed with reverse total shoulder arthroplasty.

INTRODUCTION A computer model quantified glenoid base - plate surface contact area and the amount of humeral and glenoid bone removed by three different reverse shoulder prosthesis designs when implanted with various techniques. METHODS The computer model quantified differences in glenoid baseplate contact area and the cortical and cancellous humeral and glenoid bone removed to implant the 36 mm Depuy Delta III, 32 mm neutral DJO RSP, and the 38 mm Exactech Equinoxe reverse shoulders when each was implanted along the inferior glenoid rim of a normal and 10 mm medially eroded scapula in 20° of humeral retroversion. The impact of inferior glenoid tilt was also quantified. RESULTS The Delta III resected the most overall humeral bone (47.4 cm 3 ), the 32 mm RSP the second most (38.0 cm 3 ), and the Equinoxe the least (31.7 cm 3 ). The 32 mm RSP reamed away the most glenoid bone (3.7 cm 3 ), the Delta III the second most (3.6 cm 3 ), and the Equinoxe the least (3.3 cm 3 ), with greater bone removed with inferior tilt. The Equinoxe had the most glenoid baseplate surface contact (501.3 mm 2 ), the RSP had the second most (386.0 mm 2 ), and the Delta III had the least (360.6 mm 2 ), with less surface contact occurring with medial wear.