Anatomic and CT scan assessment of Teres Minor: a new index of trophicity.

INTRODUCTION The present study reports the development of a CT assessment protocol for Teres Minor (TM) trophicity. HYPOTHESIS Quantitative reproductible Terres Minor assessment on CT estimates the influence of muscle trophicity on the clinical and radiological results of palliative treatment of irreparable rotator cuff tear. MATERIALS AND METHOD An anatomic study of 30 cadaveric shoulders confirmed a constant anatomic relation between Terres Minor and the inferior pole of the glenoid cavity. This landmark was used to develop a novel CT assessment of TM trophicity. RESULTS The CT assessment showed excellent inter- and intra-observer reproductibility. The protocol defines a trophicity index, T2/G (T2 being TM thickness on axial CT slice, and G the maximum glenoid cavity thickness on axial slice), enabling reproductible TM analysis on preoperative arthro-CT. CONCLUSION The study validated the CT protocol, allowing application in pre- and postoperative assessment of irreparable rotator cuff tear. LEVEL OF EVIDENCE Level IV. Retrospective study.