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The Journal of Bone and Joint Surgery (American) 84:2029-2038 (2002)
© 2002 The Journal of Bone and Joint Surgery, Inc.

Scientific Article

Kinematic Behavior of the Ankle Following Malleolar Fracture Repair in a High-Fidelity Cadaver Model

James D. Michelson, MD, Andrew J. Hamel, PhD, Frank L. Buczek, PhD and Neil A. Sharkey, PhD

Investigation performed at the Center for Locomotion Studies, The Pennsylvania State University, University Park, Pennsylvania

James D. Michelson, MD
GWUMC Educational Center, George Washington University School of Medicine, 900 23rd Street N.W., Room 6200, Washington, DC 20037. E-mail address: msdjdm{at}gwumc.edu

Andrew J. Hamel, PhD
Center for Locomotion Studies, The Pennsylvania State University, 29 Recreation Building, University Park, PA 16802

Frank L. Buczek, PhD
Motion Analysis Laboratory, Shriners Hospital for Children, 1645 West 8th Street, Erie, PA 16505

Neil A. Sharkey, PhD
Department of Kinesiology, The Pennsylvania State University, 276 Recreation Building, University Park, PA 16802

In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from the Orthopaedic Trauma Association. None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

Background: Previous studies involving axially loaded ankle cadaver specimens undergoing a passive range of motion after fracture have demonstrated rotatory instability patterns consisting of excessive external rotation during plantar flexion. The present study was designed to expand these studies by using a model in which ankle motion is controlled by physiologically accurate motor forces generated through phasic force-couples attached to the muscle-tendon units.

Methods: Eight right unembalmed cadaver feet were tested in a dynamic gait simulator that reproduces the sagittal kinematics of the tibia while applying physiological muscle forces to the tendons of the major extrinsic muscles of the foot. Six-degrees-of-freedom kinematics of the tibia and talus were measured with use of a VICON motion-analysis system. The experimental conditions included all combinations of lateral and medial injury to reproduce the clinical classifications of ankle fracture. Statistical analysis was performed with repeated-measures analyses of variance.

Results: The talus of the intact ankles demonstrated coupled external rotation and inversion relative to the tibia as the ankle plantar flexed. Osteotomy of the fibula, simulating a lateral ankle fracture, slightly but significantly increased external rotation and inversion of the talus (p < 0.001), whereas disruption of either the superficial or the deep deltoid ligament increased talar eversion (p < 0.003) and disruption of the deep deltoid ligament increased internal rotation (p < 0.0001). The aberrant motions were corrected by repair of the injured structure.

Conclusions: The predominant coupled rotation of the talus is external rotation associated with plantar flexion. Following progressive ankle destabilization, talar external rotation and inversion increased.

Clinical Relevance: The clinical decision-making process regarding the treatment of ankle fractures centers on determination of whether the injury is expected to result in abnormal motion, which is thought to predispose to the development of arthritis. The present study demonstrated a remarkable degree of ankle stability during stance phase even when there was severe disruption of medial and lateral structures. This finding suggests that a main determinant of clinical outcome after ankle fracture may be ankle motion during swing phase, when ankle stability is not augmented by the combination of axial loading and active motor control of motion. If swing-phase motion is abnormal, then the ankle may be in a vulnerable position at the point of heel-strike.


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