75. BONY INCREASED-OFFSET REVERSE SHOULDER ARTHROPLASTY (BIO RSA): A BIOLOGLIC SOLUTION TO SCAPULAR NOTCHING, PROSTHETIC INSTABILITY AND LIMITED SHOULDER ROTATION

Abstract

Purpose: We hypothesized that lateralization of the RSA, with a glenoid bone graft taken from the osteotomised humeral head, would prevent those problems without increasing torque on the glenoid component by keeping the center of rotation within the glenoid. The objectives of this study were to describe the results of the first 12 patients that underwent a bony increased-offset RSA (BIO RSA).

Method: Thirty-six shoulders in 34 consecutive patients with cuff tear arthritis (mean age 72 years, range 52–86 years) received a BIO RSA, consisted of a RSA incorporating an autogenous humeral head bone graft placed beneath the glenoid baseplate. A baseplate with a lengthened central peg (+25 mm) was inserted in the glenoid vault, securing the bone graft beneath the baseplate and screws. All patients underwent clinical and radiographic (computed tomography) review at a minimum 1-year follow-up.

Results: All patients were satisfied or very satisfied and all had no or slight pain. Mean active elevation increased from 72° to 142° (p< 0.05), external rotation from 10° to 18° (p< 0.05) and internal rotation from L4 to L3 (p> 0.05). Constant Score improved from 27 to 63 points (p< 0.05). The Subjective Shoulder Value (SSV) increased from 27% to 73% (p< 0.05). Radiographically, the graft healed to the native glenoid in all cases and no graft resorption under the baseplate was observed. Complications included one patient with scapular notching (stage 1) and one patient with previous radiotherapy had a deep infection. No postoperative instability, and no glenoid loosening were observed.

Conclusion: The use of an autologous bone graft harvested from the humeral head can lateralize the center of rotation of a RSA while keeping the center of rotation at the glenoid bone-prosthesis interface. The clinical advantages of a BIO RSA are a decrease in scapular notching, enhanced stability and mobility, and improved shoulder contour while keeping the center of rotation at the glenoid bone-prosthesis interface. This bony lateralization allows maintenance of the principles of Grammont and seems to be more appropriate than prosthetic lateralization. These promising early results of this novel procedure warrant further investigation.