Abstract
Introduction
Recent literature has shown that RSAs successfully improve pain and functionality, however variability in range of motion and high complication rates persist. Biomechanical studies suggest that tensioning of the deltoid, resulting from deltoid lengthening, improves range of motion by increasing the moment arm. This study aims to provide clinical significance for deltoid tensioning by comparing postoperative range of motion measurements with deltoid length for 93 patients.
Methods
Deltoid length measurements were performed radiographically for 93 patients. Measurements were performed on both preoperative and postoperative x-rays in order to assess deltoid lengthening. The deltoid length was measured as the distance from the infeolateral tip of the acromion to the deltoid tuberosity on the humerus for both pre- and post- x-rays. For preoperative center of rotation measurements, the distance extended from the center of humeral head (estimated as radius of best fit circle) to deltoid length line. For postoperative measurements, the distance was from the center of glenosphere implant to deltoid length line. Forward flexion and external rotation was measured for all patients.
Results
The average preoperative deltoid length was 154.25 mm while the average postoperative deltoid measurements was 178.93 mm. The average preoperative center of rotation as 21.33 mm and the average postoperative center of rotation measurement was 46.75 mm. There was low correlation between deltoid length and center of rotation with either forward flexion or external rotation or outcome scores.
Discussion
Our results suggest that deltoid lengthening does not significantly influence optimizing clinical outcomes for RSAs. Further research is required to determine design parameters and implants positioning to improve RSAs.
