Abnormal Translation in SLAP Lesions on Magnetic Resonance Imaging Abducted Externally Rotated View Ankur M. Chhadia, M.D., Benjamin A. Goldberg, M.D., and Mark R. Hutchinson, M.D. Purpose: The purpose of this study was to measure in vivo axial-plane translation of the glenohu- meral 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. Methods: Seven 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 CP and HHC. These values were compared between the SLAP and control groups. Results: There was a significant difference in CP 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 HHC 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. Conclusions: The 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 Relevance: This finding furthers the understanding of the pathokinematics in SLAP lesions. T he humeral head remains well centered on the glenoid with very minimal translation throughout a large rotational range of motion. 1-3 Abnormal trans- lations of the glenohumeral joint can occur with soft- tissue lesions such as anterior-inferior translation with a Bankart lesion or superior translation with rotator cuff tear arthropathy. 3 In addition, soft-tissue contrac- ture or capsulorrhaphy procedures can cause obligate translation. 3-5 SLAP lesions also have been shown in cadaveric models to be associated with pathologic translation and instability. 6-12 One study found in- creased instability in vivo in the anterior-to-posterior directions in patients with SLAP tears with external load application. 13 Further in vivo studies are needed to confirm many of the cadaveric study findings of the pathokinematics in SLAP lesions. It can be difficult to make an accurate diagnosis of a SLAP lesion because of concurrent shoulder pathol- ogy and the lack of high sensitivity and specificity in physical examination and imaging techniques. 14 Ar- throscopy is considered the gold standard tool to di- agnose SLAP lesions. 14 Magnetic resonance imaging (MRI) with or without arthrography is often obtained preoperatively to substantiate the clinical history and examination findings and to evaluate other potential shoulder lesions. 14 MRI obtained with the shoulder in an abducted externally rotated (ABER) view has been From the Department of Orthopaedics, University of Illinois at Chicago, Chicago, Illinois, U.S.A. The authors report no conflict of interest. Received July 25, 2008; accepted June 27, 2009. Address correspondence and reprint requests to Ankur M. Chha- dia, M.D., Department of Orthopaedics, University of Illinois at Chicago, 835 S Wolcott Ave, M/C 844, Chicago, IL 60612, U.S.A. E-mail: chhadia@gmail.com © 2010 by the Arthroscopy Association of North America 0749-8063/10/2601-8436$36.00/0 doi:10.1016/j.arthro.2009.06.028 19 Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 26, No 1 (January), 2010: pp 19-25