Paper #I-5

SYNDESMOSIS SCREW USE IN WEBER C ANKLE INJURIES: THE INFLUENCE OF NUMBER OF CORTICES OF FIXATION ON ANKLE JOINT STABILITY AND RANGE OF MOTION

Markku T. Nousiainen, BA (Hons.), MS, MD

Toronto,ON

Co-Authors

Alison J. McConnell, M.S.

Mohit Bhandari, M.D.

Emil H. Schemitsch, M.D.

Summary

This study investigated the effect of syndesmosis screw fixation on ankle biomechanics in Weber C ankle injuries.

Introduction

Syndesmosis screws are indicated in repairing Weber C ankle fractures if either the fibular fracture is more than 4.5 cm above the tibiotalar joint with an associated deltoid ligament tear or if rigid fixation of bimalleolar fractures cannot be obtained. This study examined the controversial issues of ankle position during screw insertion and the effect number of cortices of fixation has on ankle joint biomechanics.

Methods

Nine pairs of fresh-frozen cadaver legs were stripped, preserving the ankle joint capsule, interosseus membrane, and ligaments about the ankle. After baseline values for maximum ankle dorsiflexion, tibiofibular syndesmosis width, and tibiotalar rotation were obtained under a 700N axial load, a Weber C injury was created. A 3.5 mm fully-threaded cortical screw was inserted through 3 and then 4 cortices; the aforementioned measurements were repeated. Ankles were then externally rotated to failure to determine stiffness.

Results

Syndesmosis width, tibiotalar rotation, maximum ankle dorsiflexion, and failure stiffness were not significantly different between the groups which had either 3 or 4 cortices of fixation. Compared to intact specimens, syndesmosis width and tibiotalar rotation were significantly different when screws were inserted in either plantar- or dorsiflexion.

Conclusion

Ankle joint biomechanics are altered depending on ankle position during screw insertion but not number of cortices of purchase; ankle joint range of motion is not affected by either.