Influence of surgical approach on functional outcome in reverse shoulder arthroplasty.

INTRODUCTION: Reverse shoulder arthroplasties (RSA) can be performed using a Deltopectoral (DP) or alternatively a Transdeltoid (TD) approach. HYPOTHESIS: Although the humeral cut is lower by TD approach, this should not affect postoperative functional results. MATERIAL AND METHODS: This retrospective multicentric study evaluated the complete medical records of RSA implanted between October 2003 and December 2008. Inclusion criteria were: follow-up of at least 1 year, a complete file including a comparative radiological work-up making it possible to analyze eventual arm and humeral lengthening. Evaluation of postoperative function was based on Active Anterior Elevation (AAE). RESULTS: We studied 144 RSA in 142 patients. One hundred and nine RSA were implanted by the DP approach and 35 by the TD approach. Mean lengthening of the humerus compared to the controlateral side by DP approach was 0.5±1.3 cm while there was a mean shortening of -0.5±1.0 cm by TD approach (P<0.001). The difference in cut was partially compensated by using thicker polyethylene inserts with the TD approach. Mean arm lengthening compared to the controlateral side was 1.7±1.7 cm by DP approach and 1.2±1.4 cm by TD approach (mean difference 0.5 cm; (95% CI -0.1; 1.2). AAE for RSA by DP approach was 145±22° and 135±29° by TD approach (mean difference 10°, 95% CI -1; 21). DISCUSSION: RSA results in improved AAE because of restored deltoid tension and an increase in the deltoid lever arm. The humeral cut by TD is lower, but this was partially corrected in this study by the use of thicker polyethylene inserts. Nevertheless there is no significant clinical difference in postoperative function between the two approaches.