Abnormal Translation in SLAP Lesions on Magnetic Resonance Imaging Abducted Externally Rotated View

PurposeThe purpose of this study was to measure in vivo axial-plane translation of the glenohumeral joint by use of magnetic resonance imaging in patients with and without SLAP lesions between the conventional adducted neutral rotation (AD) view and an abducted externally rotated (ABER) view.MethodsSeven patients with an intraoperative SLAP lesion that was unstable and required repair were selected into the SLAP group. Although they did not have normal shoulders, 15 patients were selected into the control or comparison group, most of whom had rotator cuff pathology. The glenohumeral contact point (CP) and humeral head center (HHC) were calculated and compared with the glenoid surface as a relative anterior or posterior translation. The relative posterior translation between the ABER and AD views for each patient was calculated as ΔCP and ΔHHC. These values were compared between the SLAP and control groups.ResultsThere was a significant difference in ΔCP between the SLAP and control groups (3.62 v 0.79 mm of relative posterior translation, P = .005). There was not a similar significant difference found in ΔHHC between the SLAP and control groups (3.19 mm v 1.48 mm of relative posterior translation, P = .14). There was a significant difference between the mean translations of the SLAP-ABER group and the SLAP-AD group for both CP (−3.65 mm v −0.04 mm, P = .008) and HHC (−2.22 mm v +0.97 mm, P = .03). The difference between the control-ABER group and the control-AD group was not as pronounced.ConclusionsThe magnetic resonance imaging ABER view in patients with unstable SLAP lesions requiring repair showed in vivo glenohumeral posterior translation relative to the adducted neutral rotation view of greater than 3 mm.Clinical RelevanceThis finding furthers the understanding of the pathokinematics in SLAP lesions.