Ankle fractures are among the most common injuries treated by orthopaedic surgeons. Some ankle fractures are associated with syndesmotic injury and an interosseous membrane rupture. The distal tibiofibular syndesmosis consists of a complex of ligaments that provide stability to the distal tibiofibular joint. The anterior and posterior tibiofibular ligaments, together with the interosseous ligament form the syndesmosis, and the inferior transverse tibiofibular ligament is sometimes considered a fourth ligament, but this is a continuation of the posterior tibiofibular ligament. The interosseous membrane and the medial deltoid ligament add further stability to the ankle mortise [
10].
The need for distal tibiofibular syndesmotic fixation after ankle fractures remains controversial despite the abundance of literature concerning the treatment of ankle fractures [
23]. We believe syndesmotic stability should be restored in such combined injuries [
14]. Many surgeons do not perform an open reduction and internal fixation of fractures in the proximal third of the fibula, but rather place one or two syndesmotic screws instead because of the risk of peroneal nerve injury [
8,
21,
23]. The published guidelines for use of a syndesmotic screw in more distal fractures (Weber C fracture of the medial malleolus or deltoid ligament rupture associated with anterior tibiofibular ligament disruption and fibular fracture above the joint) are both conflicting and vague [
3,
15,
18]. The syndesmotic screw or other stabilizing techniques all effectively stabilize the distal tibiofibular syndesmosis to allow ligamentous healing or fibrous union [
24]. Placement of a syndesmotic screw is not without complications and requires an additional operation for removal of the screw. Therefore, it is important to clearly identify which patients will benefit from distal tibiofibular syndesmotic fixation.
The clinical diagnosis of syndesmosis disruption is insensitive and nonspecific in acute ankle fractures because many patients cannot localize the tender spot at the syndesmosis. Radiographic measurements such as tibiofibular overlap and medial and superior clear space are of little value in detecting syndesmotic injury [
1]; even additional quantitative measurement of all syndesmotic parameters with repeated radiographs of the ankle are of little value [
1,
17]. Boden et al. developed radiographic criteria to predict the need for syndesmotic fixation based on cadaveric ankles [
2]. They suggested when rigid medial fixation is achieved, no syndesmotic stabilization is required in the absence of rigid medial fixation if the height of the fibular fracture of more than 4.5 cm above the joint line requires syndesmotic stabilization. These criteria, depending on the proximity of the fibular fracture, suggest a limited rather than routine use of supplemental syndesmotic fixation [
15]. These criteria have been confirmed by Yamaguchi et al. [
26] and Chissell and Jones [
5] in clinical studies of Weber C fractures. Yamaguchi et al. [
26] evaluated patients treated according to the criteria of Boden et al. [
2] and evaluated syndesmotic stability after 1 to 3 years in those not receiving syndesmotic fixation; their data suggested use of the Boden criteria resulted in no late syndesmotic instability. Chissel and Jones [
5] reviewed patients treated by an intraoperative decision and compared that decision with one using the criteria of Boden et al.; they reported 1.6 times more syndesmotic screws were placed based on intraoperative decision than would have been used using the criteria of Boden et al. [
2]. Both authors suggested the criteria of Boden et al. are the “gold standard,” although their data could be interpreted to suggest otherwise since the decision on which syndesmotic stabilization is performed is not clarified: they were merely testing whether their decision-making conformed with the Boden criteria and not the validity of the Boden criteria [
2]. Currently, then, the recommendations for syndesmotic fixation based on the level of the fibular fracture have been based on one cadaveric study and two small clinical series (Table
1) [
2,
5,
26].
Table 1
Studies comparing the level of the fibular fracture with a gold standard as a guideline for syndesmotic stabilization in ankle fractures
| 1989 | US | 23 cadavers | Syndesmotic fixation in ankle fractures is only necessary when the fibular fracture was more than 45 mm from the ankle and rigid medial malleolar fixation was not possible (only deltoid ligament injury) |
| 1994 | US | 21 Weber C | Supports the Boden guidelines, no widening of the mortise followup |
3 syndesmotic screws |
1- to 3-year followup |
| 1995 | UK | 43 Weber C | After stable fixation of a medial malleolar fracture, a diastasis screw is required if the fibular fracture is greater than 15 cm from the joint |
31 syndesmotic screws |
2- to 9-year followup |
van den Bekerom et al. (current study) | 2009 | Netherlands | 62 pronation external rotations | Criteria of Boden et al. are helpful in surgical planning but intraoperative testing is essential |
36 syndesmotic screws |
No followup |
We therefore had two objectives: (1) to compare the height of the fibular fractures in ankles with distal tibiofibular syndesmotic instability with the height of the fibular fracture of the ankles with a stable syndesmosis; and (2) to determine the sensitivity and specificity of the criteria of Boden et al. [
2] using the hook test as the gold standard for assessing instability [
11] in distal pronation external rotation (PER) ankle fractures.