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Letters to the Editor to:

Scientific Articles:
Timothy McConnell, William Creevy, and Paul Tornetta, III
Stress Examination of Supination External Rotation-Type Fibular Fractures
J Bone Joint Surg Am 2004; 86: 2171-2178 [Abstract] [Full text] [PDF]
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Electronic letters published:

[Read Letter to the Editor] Radiographic Indicators of Ankle Instability
John F. Kragh, Jr., M.D., Jon C. Thompson, M.D., MAJ, MC, USA   (7 December 2004)
[Read Letter to the Editor] Assessment of the Deltoid Ligament Complex
James D. Michelson   (16 November 2004)

Radiographic Indicators of Ankle Instability 7 December 2004
Previous Letter to the Editor Top
John F. Kragh, Jr., M.D.,
LTC(P), MC, USA
Brooke Army Medical Center, Fort Sam Houston, TX 78234-6200,
Jon C. Thompson, M.D., MAJ, MC, USA

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Re: Radiographic Indicators of Ankle Instability

John.Kragh{at}amedd.army.mil John F. Kragh, Jr., M.D., et al.

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.
Assessment of the Deltoid Ligament Complex 16 November 2004
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James D. Michelson,
Orthopaedic Surgeon
George Washington University School of Medicine

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Re: Assessment of the Deltoid Ligament Complex

OrthoPod{at}comcast.net James D. Michelson

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.