Weight-Bearing Radiographs Instead of Stress Tests for Ankle Fractures: A New Paradigm with Caveats?

Commentary Choosing a surgical procedure or nonoperative management for ankle fractures can be viewed as an exercise in titrating the balance of risks: the risks of arthritis and nonunion compared with the risks of surgical complications and expense. In their article, Gregersen et al. offer new evidence by which to find that balance. According to traditional teaching, an ankle with a fractured fibula but an intact medial malleolus must be stressed to test the integrity of the deltoid, either by manual force or by gravity. These tests are essentially contrived. They do not approximate the reality of standing or walking. The ankle is not a simple cylindrical joint. The saddle shape of the talar dome tends to create a self-centering force when it is axially loaded. That inherent geometric stability is discounted by unloaded stress tests, but is brought into play by weight-bearing radiographs. The study asks the important question: Is the degree of stability implied by a well-aligned weight-bearing radiograph enough? With some important caveats, the answer is yes. The most important caveat is time. Posttraumatic arthritis is a slowly developing condition. These short-term 2-year follow-up data are promising, but are not definitive to answer the critical question of whether arthritic change will develop over a longer horizon. Small, dynamic subluxations that could lead to cartilage injury over time cannot be excluded by a well-centered radiograph, which is a static test. The second caveat is generalizability. All patients in the trial returned several days after injury for the weight-bearing study. All participants were willing to stand on the fractured limb at that point, even when required to demonstrate the ability to place >50% of their body weight on a scale prior to the radiography. That level of pain tolerance is not likely to be universal, but it is critical to the interpretation of the study. The third caveat is sensation. Patients with peripheral neuropathy of any cause were excluded from the trial. This condition is not confined to patients with diabetes. The prevalence of peripheral neuropathy has been estimated to be 10.4% among adults between the ages of 40 and 69 years and increases to between 26.8% and 39.2% for adults ≥70 years of age1. Posttraumatic activation of neuropathic arthropathy in the ankle is best controlled with early and aggressive instrumentation. Beyond that concern, neuropathy alone could potentially accelerate the development of posttraumatic arthritis in the setting of malunion. Immediate mobilization in a stirrup splint could prove disastrous for this vulnerable population. Lastly, the lessons of the trial should be separated from the confusing previously proposed nomenclature subdividing the Lauge-Hansen system into an “SER4a” group, patients whose fracture proves stable on weight-bearing radiographs but unstable on stress views, and a separate group labeled “SER4b,” patients whose fracture is unstable on both2. It is critical to remember that this study included only patients with rotational Weber B fibular fractures but no other osseous injury. The SER4 category, in general, does not distinguish between patients with additional posterior malleolar or medial malleolar fractures and patients with ligamentous injuries in those areas. The posterior malleolus is a confounding factor and has been increasingly recognized as a source of ankle stability3. This trial must be interpreted simply for what it is: an evaluation of fibular fractures with varying degrees of associated medial and posterior soft-tissue trauma. Modifying the Lauge-Hansen system to fit the outcome of weight-bearing radiographs does not improve clarity or communication. With its limitations recognized, the study by Gregersen et al. has the potential to alter our thinking about which patients require a surgical procedure for this common injury pattern. The study offers substantial support for a nonoperative treatment paradigm, provided that patients match the parameters used in the trial and remain closely monitored through their course. For the younger or more active patient concerned about late arthritic change beyond the 2-year horizon, a clear discussion of what exactly the trial does and does not show is warranted.