Rockwood Adults CH64

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CHAPTER 64 • Ankle Fractures

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B Figure 64-16.  A: A suprasyndesmotic fibular fracture following ORIF. The fibula is imperfectly reduced but although there appears to be a satisfactory tibiofibular overlap (syndesmosis B, Table 64-2) the tibiofib- ular clear space (syndesmosis A, Table 64-2) is wide. B: A CT scan shows malreduction of the syndesmosis.

EVIDENCE-BASED MANAGEMENT OF ANKLE FRACTURES Isolated Lateral Malleolar Fractures Truly isolated lateral malleolar fractures are stable, do not result in tibiotalar incongruence, and can be treated conservatively. Cadaveric studies show that an isolated fracture of the distal fib- ula does not result in abnormal ankle kinematics. 251 Long-term cohort studies have universally reported good results. Bauer et al. 27 reported that 98% of patients with SER 2 fractures show no evidence of osteoarthritis at 30 years post injury, and Kris- tensen and Hanson 200 reported that 95% of patients have good functional outcomes at 21 years. Indeed, surgical intervention in these patients may result in increased pain and worse func- tion, 289 and a recent RCT has confirmed that not only is there no benefit from surgery, it exposes patients to unnecessary compli- cations. 258 Ongoing symptoms may be due to cartilage damage at the time of injury. Hintermann 152 found that 60% of patients with isolated AO type B lateral malleolar fractures had chondral damage to the talus and 50% showed damage to the fibula. Management is aimed at allowing the patient to mobilize rapidly and return to normal function. A number of meth- ods have been shown to be satisfactory including below-knee weight-bearing casts, elasticated bandaging, 306 air stirrup devices, 45 ankle braces 45 and stabilizing shoes. 431 No signifi- cant differences have been found in outcome beyond 3 months between these treatment options. Pragmatically, whichever is most convenient for both surgeon and patient is likely to result in good long-term function. The persistent minor radiographic displacement of the lat- eral malleolus seen in most patients does not impair clinical outcome. 426 Despite this unambiguous clinical evidence, there remains occasional concern as to whether this equates to loss of normal mortise congruence. The SER 2 fracture has a typical

oblique fracture line at the level of the syndesmosis with appar- ent external rotation, posterior translation, and shortening on plain radiographs (see Fig. 64-18A; see Fig. 64-9). Michelson and Harper addressed these concerns in a key investigation, using CT analysis of displacement. 142,248 They showed that for these SER 2 injuries, the distal fibular fragment remains ana- tomically wedded to the talus, which in turn maintains its nor- mal relationship with the tibial plafond. Distal talofibular and tibiotalar alignment is therefore normal. The cause of the appar- ent radiographic malalignment is actually internal rotation of the proximal fibular fragment rather than external rotation of the distal fragment. Moreover, whereas plain radiographs often appear to demonstrate several millimeters of displacement at the fracture site, on CT this is seen to be actually less than 1 mm of displacement, and this is biomechanically unimportant. The other common group of isolated lateral malleolar frac- tures, the SAD 1 fracture, may be considered a part of the spec- trum of ligamentous ankle injuries in adults and managed with functional bracing or casting: Outcomes are comparable to purely ligamentous injuries. 139 While the stable SER2 fracture described above can be man- aged nonoperatively, the combination of a lateral malleolar fracture with failure of the deltoid ligament (one of the two variants of the SER 4 fracture) renders the ankle unstable and usually requires surgery. The diagnosis is made on the basis of obvious deformity of the ankle at the time of presentation or clear displacement of the talus on the presentation radiographs. Management is surgical reduction and fixation of the lateral malleolus with intraoperative assessment of the syndesmosis. Lateral Malleolar Fractures Associated With Clear Instability