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Instructional Course Lecture   |    
The Unstable Elbow*†
Shawn W. O'Driscoll, Ph.D., M.D., F.R.C.S.(c)‡; Jesse B. Jupiter, M.D.§; Graham J. W. King, M.D, M.Sc., F.R.C.S.(C)#; Robert N. Hotchkiss, M.D.**; Bernard F. Morrey, M.D.‡
View Disclosures and Other Information
An Instructional Course Lecture, American Academy of Orthopaedic Surgeons
*Printed with permission of the American Academy of Orthopaedic Surgeons. This article, as well as other lectures presented at the Academy's Annual Meeting, will be available in March 2001 in Instructional Course Lectures, Volume 50. The complete volume can be ordered online at www.aaos.org, or by calling 800-626-6726 (8 A.M.-5 P.M., Central time).
†One or more of the authors has received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this article.
‡Mayo Clinic, 200 First Street S.W., Rochester, Minnesota 55905.
§Department of Orthopaedic Surgery, Massachusetts General Hospital, WACC 527, 15 Parkman Street, Boston, Massachusetts 02114.
#Hand and Upper Limb Centre, St. Joseph's Health Centre, 168 Grosvenor Street, London, Ontario N6A 4V2, Canada.
**The Hospital for Special Surgery, 535 East 70th Street, New York, N.Y. 10021.

J Bone Joint Surg Am, 2000 May 01;82(5):724-724
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Extract

The pathoanatomy of an elbow dislocation can be thought of as a disruption of the circle of soft tissue or bone, or both, that begins on the lateral side of the elbow and progresses to the medial side in three stages (Fig. 1-A). In stage 1, the lateral collateral ligament is partially or completely disrupted (the ulnar part is disrupted). This disruption results in posterolateral rotatory subluxation of the elbow, which can reduce spontaneously (Fig. 1-B). Stage 2 involves additional disruption anteriorly and posteriorly. There is an incomplete posterolateral dislocation of the elbow in which the concave medial edge of the ulna rests on the trochlea. On a lateral radiograph of the elbow, the coronoid process appears to be perched on the trochlea. This dislocation can be reduced with use of minimal force or by the patient manipulating his or her own elbow. Stage 3 is subdivided into three parts. In stage 3A, all of the soft tissues around and including the posterior part of the medial collateral ligament are disrupted, leaving only the important anterior band (the anterior medial collateral ligament) intact. This permits posterior dislocation by a posterolateral rotatory mechanism. The elbow pivots on the intact anterior band of the medial collateral ligament. Reduction is accomplished by gentle manipulation of the elbow beginning with supination and valgus stress, temporarily recreating the deformity, followed by application of traction, varus stress, and pronation simultaneously. The intact anterior medial collateral ligament provides stability if the forearm is kept in pronation to prevent posterolateral rotatory subluxation during valgus stress-testing. Stage-3A instability is most commonly seen in the presence of fractures of the radial head and coronoid process. In stage 3B, the entire medial collateral complex is disrupted. Varus, valgus, and rotatory instability are all present following reduction. In stage 3C, the instability is so severe that the elbow can dislocate even when it is immobilized in a cast in 90 degrees of flexion. This degree of instability occurs because the entire distal aspect of the humerus has been stripped of soft tissues. Usually, reduction can be maintained only by flexing the elbow beyond 90 degrees to 110 degrees. The flexor-pronator and common extensor muscle origins are important secondary stabilizers of the elbow. These pathoanatomical stages all correlate with clinical degrees of elbow instability. Most commonly, elbow dislocations involve disruption of both the medial and the lateral collateral ligament and, therefore, are at least stage 21-3.
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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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