CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Number 400, pp. 88–92 © 2002 Lippincott Williams & Wilkins, Inc. 88 Cadaveric Study of Glenohumeral Translation Using Electromagnetic Sensors Mark T. Reis, MD**; James E. Tibone, MD** ,† ; Patrick J. McMahon, MD* ,‡ ; and Thay Q. Lee, PhD* Clinical methods for measuring shoulder trans- lation rely heavily on the experience of the ex- aminer and remain largely subjective, prone to errors of interobserver and intraobserver repro- ducibility. Accurate in vitro methods of measur- ing glenohumeral translation exist. The purpose of the current study was to evaluate the accuracy of computerized electromagnetic spatial sensors applied to the skin, in measuring glenohumeral translation under simulated conditions of a stan- dard shoulder examination. Seven thawed, fresh- frozen shoulder specimens from cadavers were used in the study. Soft tissue and skin were not re- moved. The specimens were mounted to simulate clinical positions of patients having an antero- posterior drawer or load-and-shift test. A series of anterior and posterior displacements were done manually under two conditions. Condition I: Electromagnetic position sensors were taped to skin and held beneath the examiner’s fingers; and Condition II: Sensors were fixed rigidly to pins inserted into the glenoid and humeral head, respectively. Displacement values between condi- tions, within trials, and among specimens were compared for accuracy and reproducibility. Strong agreement was shown between Condition I and Condition II for the anterior and posterior directions (interclass correlation coefficients 0.81 and 0.86, respectively). Simple linear regression revealed a significant association between condi- tions in the anterior and posterior directions. Re- producibility between trials under each condition was extremely high, with interclass correlation coefficients greater than or equal to 0.98 regard- less of direction of displacement or testing condi- tion. The data from the current study show that cutaneous application of electromagnetic posi- tion sensors to the shoulder can accurately and reproducibly measure true glenohumeral trans- lation under testing conditions that mimic a stan- dard, clinical shoulder examination. Despite significant advances in understanding of normal and pathologic glenohumeral transla- tions, the magnitude of these translations in the clinical setting remains difficult to quantify ac- curately. Biomechanical research methods can describe certain glenohumeral motions with precision. The accuracy of electromagnetic spa- tial sensors rigidly fixed to bone in measuring joint displacement has been shown. 5,14 Such measurement techniques are too invasive to be considered for widespread clinical application. In contrast, physical examination techniques for From the *Orthopaedic Biomechanics Laboratory, VA Healthcare System, Long Beach, CA, and University of California, Irvine; the **Kerlan-Jobe Orthopaedic Clinic, Los Angeles, CA; the † University of Southern California Associates; and the ‡ Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA. Reprint requests to Thay Q. Lee, PhD, Orthopaedic Bio- mechanics Laboratory, VA Long Beach Healthcare System (09/151), 5901 East 7th Street, Long Beach, CA 90822.