Reducing the Syndesmosis Under Direct Vision: Where Should I Look?

Given the continued debate regarding syndesmotic screw fixation, we reviewed our institution's series of ankle syndesmotic screw insertions: 1) to examine technical aspects of syndesmotic screw fixation; and 2) to identify predictors of function and quality of life utilizing validated instruments. Retrospective observational study (level IV). Three university hospitals. All patients with ankle injuries who received syndesmotic screw fixation at 3 university-affiliated hospitals from 1998 to 2001. A combined hospital database for all 3 university affiliated hospitals was searched to identify all ankle fractures. Potentially eligible patients' charts were hand searched to determine the use of syndesmotic screw fixation. Radiographs from each patient were assessed for final eligibility for study inclusion. Baseline demographic information, fracture type (Lauge-Hansen, AO Weber), radiographic measurements of syndesmotic reduction, type of implants (number of screws, number of cortices, screw size), and screw removal at follow-up were determined. All radiographs were standardized for magnification. Patients also reported return to work, a visual analogue ankle pain score, and completed 2 functional outcomes instruments (Short Musculoskeletal Functional Assessment Index, Olerud and Molander Scale). Return to work, a visual analogue ankle pain score, and 3 functional outcomes instruments (Short Musculoskeletal Functional Assessment Index, Olerud and Molander Scale). Of 425 ankle fractures treated, 51 fractures had syndesmotic screw fixation. Patients were often males (67%), mean age 40.0 +/- 18.0 years, with sedentary occupations (88%), and twisting injuries (80%). Seventy percent of injuries were pronation external rotation injuries, and 30% were supination external rotation injuries. The ankle was dislocated in 45% of cases. The most common constructs for fixation included lateral plates with syndesmotic screws (45%). The majority of constructs included a single 3.5-mm cortical screw through 3 cortices of bone. Based upon postoperative x-rays, 16% of syndesmoses were not reduced. Additionally, 8 patients were deemed have inappropriate/lack of indications for syndesmotic screw insertion. At final follow-up (N = 39 patients, mean 18.1 months), patients achieved good function and quality of life (mean scores: Short Musculoskeletal Functional Assessment functional index = 11.4 +/- 10.6, Short Musculoskeletal Functional Assessment bother index = 13.5 +/- 13.1, Olerud and Molander = 74.1 +/- 23.4, visual analogue pain scale = 1.7 +/- 1.9). The only significant predictor of functional outcome was reduction of the syndesmosis (P = 0.04). This variable alone accounted for 18% of the variation in Short Musculoskeletal Functional Assessment Index physical function scores and 15% of the variance in the Olerud and Molander (running subscale) outcome measure. Our findings suggest: 1) technical aspects of syndesmotic screw fixation vary between surgeons; 2) 16% of syndesmotic screws may have been unnecessary; and 3) despite variability in technique and indications, anatomic reduction of syndesmosis was significantly associated with improved Short Musculoskeletal Functional Assessment Index functional outcome. Larger, prospective studies are needed to further explore our findings.

Diagnosis and reduction of syndesmosis injuries in ankle fractures can be challenging. Previous studies have demonstrated that standard radiographic measurements used to evaluate the integrity of the syndesmosis are inaccurate. The purpose of this study was to determine the adequacy of standard postoperative radiographic measurements in assessing syndesmotic reduction compared to CT and to determine the prevalence of postoperative syndesmotic malreduction in a patient cohort. Twenty-five patients with ankle fractures and syndesmotic instability who had open reduction and syndesmotic fixation were evaluated. All patients had a standard radiographic series postoperatively followed by a CT scan. Radiographic measurements were made by three observers to determine the tibiofibular relationship. Axial CT scan images were judged for quality of reduction of the syndesmosis by measuring the distance between the fibula and the anterior and posterior facets of the incisura. Differences between the anterior and posterior measurements of more than 2 mm were considered incongruous. Six patients (24%) had evidence of postoperative diastasis using the radiographic criteria, four of whom had evidence of malreduction on postoperative CT scan. Conversely, 13 patients (52%) had incongruity of the fibula within the incisura on CT scan (average 3.6 mm, range 2.0 to 8.0 mm), only four of whom had one or more abnormal radiographic measurements. In 10 (77%) of the 13 malreductions seen on CT scan, the posterior measurement was greater, indicating that internal rotation or anterior translation of the fibula may have occurred. Sensitivity of radiographs was 31% and the specificity was 83% compared to CT. Many syndesmoses were malreduced on CT scan but went undetected by plain radiographs. Radiographic measurements did not accurately reflect the status of the distal tibiofibular joint in this series of ankle fractures. Furthermore, postreduction radiographic measurements were inaccurate for assessing the quality of the reduction. Although we did not seek to correlate functional outcomes, the known morbidity of postoperative syndesmotic malreduction should lead to heightened vigilance for assessing accurate syndesmosis reduction intraoperatively.

To examine the correlation between syndesmotic malreduction and functional outcome.