Hidden treat (CC by
Karon Elliott Edleson

The posterior malleolus has long been viewed as an important determinant of outcome after ankle fractures. Earlier observational studies (Verhage et al. (2016) and van Hoff et al. (2015)) suggested worse long-term results when the fragment was incongruent or displaced, which in turn fueled a trend toward more frequent fixation. Against this background, many of us were eager to see the POSTFIX RCT that put that theory to a test and the results were not what many expected.

The trial randomized 81 patients to fixation or no fixation of the posterior malleolus. While 80 patients is on the smaller side, the approach used is considerably more extensive than the standard lateral fibular approach, and one would therefore expect a meaningful clinical benefit if one exists. If a sample size of 200–400 patients would be required to detect an effect, it raises the question whether the true benefit is large enough to justify the more extensive surgery.

That said, Van Hoff et al. studied 130 patients with a mean follow-up of seven years and found a higher degree of osteoarthritis in fractures involving the posterior malleolus, particularly when the step-off exceeded 1 mm. In their study, they did not find evidence that fixation improved outcomes, and they noted that the step-off often persisted even after fixation. This is also supported by Franx et al’s series where thet could not see any effect of posterior malleolar fixation.

In the POSTFIX trial, all patients were treated using the posterolateral approach. While this has long been my preferred approach, one might if there are issues with the approach, Heyes et al found 5% skin necrosis and another 5% with nerve injury.I also wonder whether exposure itself provokes a capsular reaction. It may be worth considering whether a less invasive approach could achieve similar results while reducing soft-tissue trauma.

Despite these uncertainties, it is encouraging to finally see high-quality evidence emerging. I am very much looking forward to the five- and ten-year results.