In lateral epicondylitis, even in the absence of apparent instability, subtle instability can be found under anesthesia. We wanted to ascertain the following: (1) how many elbows surgically treated with lateral epicondylitis showed subtle instability during examination under anesthesia (EUA), (2) how effective magnetic resonance imaging (MRI) was in predicting subtle instability, and (3) if any difference existed in preoperative clinical data between elbows with and without subtle instability during EUA.
One hundred and twenty-two elbows (117 patients) diagnosed with intractable lateral epicondylitis underwent surgical treatment. No elbow showed apparent instability with conventional physical examination. Under general anesthesia, the elbows were examined for subtle instability via fluoroscopy and divided into unstable and stable groups. Potential prognostic factors and functional scores were assessed retrospectively. The MRIs were reviewed again by two radiologists.
Seventeen elbows (unstable group, 13.9%) had subtle instability in EUA, while 105 elbows (stable group, 86.1%) did not. Lateral collateral ligament (LCL) complex injury was noted in the MRIs of 28 elbows. Fifteen elbows showed subtle instability among 28 elbows with abnormal MRI (positive predictive value, 53.6%), while 81 elbows did not show subtle instability among 82 elbows with normal MRI (negative predictive value, 98.7%). The preoperative visual analog scale score was higher in the unstable group than in the stable group (p < 0.001), and a history of multiple corticosteroid injections (≥3) was related to subtle instability in EUA (p = 0.042). Other factors showed no significant differences between both groups.
Subtle instability resulting from LCL complex injury was noted in elbows with lateral epicondylitis. This could be visualized with fluoroscopic EUA, and preoperative MRI could be used to exclude subtle instability. Surgeons should consider checking for subtle instability, especially when patients have a history of multiple corticosteroid injections (≥3) or severe pain and MRI indicates instability.