THE EFFECT OF INTRA-OPERATIVE FLUOROSCOPIC STRESS TESTING ON DIAGNOSIS AND MANAGEMENT OF DISTAL TIBIO-FIBULAR SYNDESMOSIS INJURIES

Abstract

This study is designed to evaluate intra-operative stress testing on detection of syndesmosis injuries. We evaluated forty patients with ankle fractures requiring surgery. Their ankles were subjected to stress examinations after each stage of fixation. These were compared to the contralateral side. Biomechanical criteria were used to predict need for syndesmosis fixation. In 42% of the fractures, intra-operative fluoroscopy found an unpredicted syndesmosis injury. In 8% the syndesmosis was intact despite prediction. Medial malleolar fixation was not adequate for syndesmosis fixation as shown by stress testing. These findings may have implications for future diagnosis and treatment of syndesmosis injuries.

This study is designed to evaluate the utility of intra-operative fluoroscopic stress testing in diagnosing tibio-fibular syndesmotic injuries.

Forty skeletally mature patients with unilateral external rotation ankle fractures requiring open reduction and internal fixation were prospectively recruited. Intra-operatively the injured ankle was examined fluoroscopically using external rotation, valgus and anterior drawer stress tests, as well as static antero-posterior, mortise, and lateral ankle views. Stress testing was performed using a standardized force of 37.5 N. Stress testing was done after each stage of fixation (lateral, medial, and syndesmotic). The uninjured contralateral limb was examined as a control, and a 1 mm side to side difference was defined as a positive stress examination.

Intra-operative fluoroscopy detected unpredicted syndesmotic injuries in 42 % of ankle injuries. In all cases, fixation of the medial malleolus did not restore syndesmotic stability. In 8 % of ankle injuries, a syndesmotic injury was predicted but stress testing revealed the syndesmosis intact.

Intra-operative fluoroscopy is a more sensitive modality for detection of otherwise unpredicted syndesmotic injuries compared to criteria based upon static radiographs. Medial malleolar fixation did not add stability to syndesmotic injuries in this study.

Injuries involving the distal tibio-fibular syndesmosis are difficult to detect. Previously, the decision to stabilize the syndesmosis in ankle fractures was based upon biomechanical criteria and static radiography. This and other recent studies challenge this, suggesting fluoroscopic stress testing is a better diagnostic method for these poorly tolerated injuries.

Funding: Synthes Canada, Smith Nephew Richards Inc.