Rockwood Adults CH64

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SECTION FOUR • Lower Extremity

the importance of more subtle degrees of abnormality remain uncertain and controversial. Radiographic interpretation is often a clinical judgment made in the light of the individual circumstances of the injury, the clinical features present, and the state of health and functional requirements of the patient. Axial Imaging Neither CT nor MRI is used routinely in the investigation of ankle fractures. CT scanning is helpful in characterizing joint displacement in pilon fractures, assessing the size of a poste- rior malleolar fragment, and in assessing the accuracy of the reduction of the syndesmosis postoperatively (Figs. 64-16 and 64-17). MRI has been used in the experimental setting to assess the integrity of the deep deltoid ligament where this is uncer- tain, but this is not common practice. Additional osteochondral lesions are not infrequently identified on MRI scans, but the importance of these remains uncertain. The vast literature on the treatment of ankle fractures is replete with small heterogeneous case series reporting the outcome of a bewildering variety of management strategies, using disparate outcome assessments. Critical review of this literature suggests that satisfactory outcomes can be obtained with a variety of treatments, but equally that the indiscriminate use of surgery does not necessarily improve outcomes and exposes the patient to additional complications. A satisfactory outcome after ankle fracture can be anticipated when the joint is congruent (the talus is placed anatomically under the plafond) and stable (it remains there until fracture healing). TREATMENT OPTIONS FOR ANKLE FRACTURES

Mortise view

Tibiofibular clear space (A)

Tibiofibular overlap (B) Medial clear space

Ball sign

A

B

Normal

Talocrural angle

Figure 64-14.  Radiographic measurements. See Table 64-2 for expla- nation. The ball sign is explained in Figure 64-15.

and uncertainty. There is substantial variability in “normal” anatomy between individuals, and comparison views of the contralateral side are occasionally helpful. Absolute measure- ments are also affected by magnification, and the degree of axial rotation of the limb. 129 Pneumaticos et al. 304 have demonstrated that, for example, the size of the medial clear space more than doubles depending upon the rotational position of the limb, and there is a significant increase in medial clear space with ankle plantarflexion, a common trap for the unwary. 198,328 More- over, the accuracy of plain radiographic measurements has been questioned in the light of CT studies that have shown that a number of assumptions based on the interpretation of a two-di- mensional radiographs are simply not accurate. 138,149 While both a perfectly normal radiograph, and one with clear displacement, can usually be recognized with confidence,

A

B Figure 64-15.  A: The “ball” sign is described on the AP view as an unbroken curve connecting the recess in the distal tip of the fibula and the lateral process of the talus when the fibula is out to length. B: If the fibula is short and malreduced the ball sign is absent.