Background: The isokinetic muscle performance test (IMPT) is a validated and objective method used to evaluate muscle function but it is unknown whether it correlates with severity of rotator cuff tears.
Questions/purposes: We asked whether peak torque and total work deficit on the IMPT correlated with the preoperative manual muscle test (MMT), tear size, fatty degeneration (FD) of cuff, and postoperative cuff integrity in patients after rotator cuff surgery.
Methods: We evaluated 221 patients who had undergone rotator cuff repair; of these 86 had the IMPT and a CT arthrogram (CTA) 1 year after surgery.
Results: We found a correlation (r = 0.125 approximately 0.464) between the preoperative IMPT and MMT. The IMPT deficit was greater in rotator cuff muscles with larger tears and greater degree of FD. Preoperative external and internal rotation deficits on the IMPT were related to the risk of cuff detachment on the postoperative CTA (r = 0.290, 0.319), and the postoperative abduction deficit was greater than 40% of the contralateral side indicating cuff detachment.
Conclusions: The IMPT provides objective and quantitative data for estimating the preoperative status of rotator cuff tear and can provide baseline data for postoperative anatomic assessment in patients with rotator cuff disorders.
Level of evidence: Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.