Evaluation of Contrast Extravasation as a Diagnostic Criterion in the Evaluation of Arthroscopically Proven HAGL/pHAGL Lesions

Purpose. The validity of preoperative MRI in diagnosing HAGL lesions is debated. Various investigations have produced mixed results with regard to the utility of MRI. The purpose of this investigation is to apply a novel method of diagnosing HAGL/pHAGL lesions by looking at contrast extravasation and to evaluate the reliability of such extravasation of contrast into an extra-articular space as a sign of HAGL/pHAGL lesion. Methods. We utilized specific criteria to define contrast extravasation. We evaluated these criteria in 12 patients with arthroscopically proven HAGL/pHAGL lesion. We also evaluated these criteria in a control group. Results. Contrast extravasation occurred in over 83% of arthroscopically positive cases. Contrast extravasation as a diagnostic criterion in the evaluation of HAGL/pHAGL lesions demonstrated a high interobserver degree of agreement. Conclusions. In conclusion, extra-articular contrast extravasation may serve as a valid and reliable sign of HAGL and pHAGL lesions, provided stringent criteria are maintained to assure that the contrast lies in an extra-articular location. In cases where extravasation is not present, the “J” sign, though nonspecific, may be the only evidence of subtle HAGL and pHAGL lesions. Level of Evidence. Level IV, Retrospective Case-Control series. 1. Introduction Current knowledge is mixed with regard to the reliability of MRI for diagnosing HAGL/pHAGL lesions. Specific findings on MRI that have been discussed previously include direct identification of the disrupted ligament, contrast extravasation medial to the humerus, and the “J” sign. This investigation looks at areas of contrast extravasation into anatomical spaces not previously studied, such as the quadrilateral space and intra/paramuscular spaces. This greatly enhanced the diagnostic capability of MRI. While contrast extravasation medial to the humerus has previously been elucidated, this is the first study to prescribe rigorous MRI criteria in order to differentiate true extravasation of contrast from a low-lying axillary pouch or “J” sign. While the “J” sign is not specific for HAGL/pHAGL, it was the only finding in 2 patients in our HAGL/pHAGL cohort, and it may be the only finding in subtle cases. This constitutes the largest series of arthroscopically proven HAGL lesions reported thus far. This is also the only series that evaluates interobserver variability for diagnosing HAGL/pHAGL by MRI criteria and the only study that evaluates a cohort of control patients for comparison to validate the use of an MRI sign of HAGL/pHAGL lesion. Our