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Stress Examination of Supination External Rotation-Type Fibular Fractures
Timothy McConnell, MD1; William Creevy, MD1; Paul TornettaIII, MD1
1 Boston University Medical Center, 818 Harrison Avenue, Boston, MA 02118. E-mail address for P. Tornetta III: ptornetta@pol.net
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In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from Aircast, Inc. 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..
Investigation performed at Boston University Medical Center, Boston, Massachusetts

The Journal of Bone and Joint Surgery, Incorporated
J Bone Joint Surg Am, 2004 Oct 01;86(10):2171-2178
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Abstract

Background: Deltoid incompetence in association with an isolated fibular fracture is assumed to be present if there is medial tenderness, ecchymosis, or substantial swelling. We sought to determine whether these soft-tissue indicators predict deltoid incompetence by comparing such findings with the findings on stress radiographs.

Methods: Over a thirty-two-month period, 138 patients who presented acutely with a Weber type-B supination-external rotation (SE) fibular fracture were evaluated for tenderness (in nine locations), ecchymosis, and swelling. Patients who presented with an apparently isolated fibular fracture and an intact ankle mortise (with a medial clear space of =4 mm and no talar subluxation) were evaluated with a stress radiograph to determine deltoid competence. Four groups of patients were identified: those who had an SE2 fracture (defined as those who had a stable ankle on the stress radiograph), those who had a stress (+) SE4 fracture (defined as those who had an unstable ankle on the stress radiograph), those who had an SE4 fracture (defined as those who presented with a wide medial clear space), and those who had a bimalleolar fracture. These four groups were compared with regard to tenderness, swelling, and ecchymosis at the time of initial presentation. Patients with SE2 injuries were allowed immediate weight-bearing.

Results: Of the ninety-seven patients who presented with an isolated fibular fracture and an intact mortise, sixty-one had a stable SE2 injury and thirty-six had an unstable stress (+) SE4 injury. All stable SE2 injuries healed with an intact mortise. Medial tenderness, ecchymosis, and swelling were not predictive of deltoid incompetence (instability).

Conclusions: Stress radiographs allow for the accurate diagnosis of deltoid incompetence in patients with Weber type-B SE fibular fractures and no other osseous injury. Soft-tissue indicators are not accurate predictors of instability. If medial tenderness, ecchymosis, and swelling are used as operative indications, in some cases surgery may be performed on stable ankles.

Level of Evidence: Diagnostic study, Level II-1 (development of diagnostic criteria on basis of consecutive patients [with universally applied reference "gold" standard]). See Instructions to Authors for a complete description of levels of evidence.

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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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    John F. Kragh, Jr., M.D.
    Posted on November 17, 2004
    Radiographic Indicators of Ankle Instability
    Brooke Army Medical Center, Fort Sam Houston, TX 78234-6200

    To the Editor:

    We thank Egol et al. and McConnell et al. for their fine works on deltoid ankle instability with fibula fractures(1,2). We ask them to consider replying to the ideas herein.

    1. Women have smaller radiographic medial clear spaces than men,(3) and the use of an absolute threshold introduces non-random error into measurement of instability. An absolute threshold biases assessment because of patient size.

    2. Magnification variability due radiographic technique introduces error when using an absolute distance measurement on radiographs to represent an anatomical distance.

    3. The operational definition of instability chosen by Egol et al. and used as an indicator by McConnel et al., that is, a medial clear space >4mm on a radiograph during stress examination without anesthesia, led to some determinations of instability that were difficult to explain(1,2). Unstressed radiographic medial clear spaces are reportedly up to 5.5mm in radiographs without fracture and about 8% are >4mm.(4) In cadaver ankles with fibulas excised in simulation of ankle fracture with an intact deltoid ligament, the medial clear space distance increased up to 2mm from the resting distance when stressed due to deltoid laxity at rest.(5) As 4mm may be too low a threshold at rest and up to 2mm more may be added when stressed with the deltoid ligament intact, then laxity may need more consideration in determining instability thresholds. Some of Egol et al.’s patients may have been stressed >4mm yet have had intact superficial and/or deep deltoid ligaments. The 4mm threshold historically is an unstressed threshold, but both recent reports used it as stressed. An explanation of the stressed-unstressed mismatch by the authors may help as these problems with the 4mm absolute threshold may in part explain the difficulties.

    4. Radiographic indicators of ankle instability that address these problems may perform better diagnostically. Conceivably, if the medial clear space is divided by the superior clear space to get a relative index of instability, then the problems of patient size bias, magnification error, and the absolute threshold can be mitigated.

    John F. Kragh, Jr. M.D. LTC(P), MC, USA

    Jon Thompson, M.D. MAJ, MC, USA

    1. Egol KA, Amirtharage M, Tejwani NC, Capla EL, Koval KJ. Ankle stress test for predicting the need for surgical fixation of isolated fibular fractures. J Bone Joint Surg, 86A:2393-405, 2004.

    2. McConnell T, Creery W, Tornetta P III. Stress examination of supination external rotation-type fibular fractures. J Bone Joint Surg, 86A:2171-8, 2004.

    3. Jonsson K. Fredin HO. Cederlund CG. Bauer M. Width of the normal ankle joint. Acta Radiologica: Diagnosis. 25(2):147-9, 1984.

    4. Brage ME, Bennett CR, Whitehurst JB, Getty PJ, Toledano A. Observer reliability in ankle radiographic measurements, Foot Ankle Int, 18:324-9, 1997.

    5. Close JR. Some applications of the functional anatomy of the ankle joint. J Bone Joint Surg, 38A:761-81, 1956.

    James D. Michelson
    Posted on November 02, 2004
    Assessment of the Deltoid Ligament Complex
    George Washington University School of Medicine

    To the Editor,

    I congratulate Drs. McConnell, et al.,(1) on their paper describing a clinical method to evaluate the competence of the deltoid ligament. Since biomechanical ankle instability is determined by the presence of complete medial injury(2-6), assessing the competence of the deltoid complex does, as noted by McConnell, et al., assume primary importance in the treatment of patients with ankle fractures.

    It should be noted, however, that previous work(7) provided the underpinning of this study by demonstrating that the ankle is unstable to valgus stress only when the deep and superficial deltoid ligaments are simultaneously injured. In the earlier study, the need for forceful application of stress was avoided by letting gravity provide gentle stress to the ankle, similar to the gravity stress test for ulnar instability of the elbow. This was accomplished by taking a mortise or antero-posterior radiograph of the ankle while it was held horizontal (medial side uppermost) and supported on a pillow. This radiographic technique was shown to be 100% sensitive and 100% specific for deltoid injury in a cadaver model. Although the work of McConnell has added external rotation to the stress view, it essentially provides the companion clinical study to the previous laboratory investigation. As such, it serves to validate the concept of how to assess the competence of the deltoid ligament complex.

    This is a significant study that points out the importance of assessing the deltoid ligament complex in the treatment of lateral malleolar ankle fractures. Whether one uses the applied external rotation stress method or the gravity stress method, the authors have done well by emphasizing the need to determine deltoid competence, so as to avoid unnecessary surgery in isolated lateral malleolar fractures (3,4).

    Sincerely,

    James Michelson, M.D.

    Reference List

    1. McConnell, T., Creevy, W., and Tornetta, P., III: Stress examination of supination external rotation-type fibular fractures. J Bone Joint Surg. Am. 86-A:2171-2178, 2004.

    2. Michelson, J. D., Ahn, U. M., and Helgemo, S. L.: Ankle Motion Following Simulated Supination-External Rotation Fracture. J. Bone. Joint. Surg. [Am]. 78:1024-1031, 1996.

    3. Michelson, J. D.: Ankle fractures resulting from rotational injuries. J Am. Acad. Orthop. Surg. 11:403-412, 2003.

    4. Michelson, J. D.: Fractures about the ankle. J. Bone Joint Surg. Am. 77:142-152, 1995.

    5. Earll, M., Wayne, J., Brodrick, C., Vokshoor, A., and Adelaar, R.: Contribution of the deltoid ligament to ankle joint contact characteristics: a cadaver study. Foot Ankle Int. 17:317-324, 1996.

    6. Boden, S. D., Labropoulos, P. A., McCowin, P., Lestini, W. F., and Hurwitz, S. R.: Mechanical considerations for the syndesmosis screw. A cadaver. J. Bone Joint Surg. [Am. ]. 71:1548-1555, 1989.

    7. Michelson, J. D., Varner, K. E., and Checcone, M.: Diagnosing deltoid injury in ankle fractures: the gravity stress view. Clin Orthop. 387:178-182, 2001.

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