CHAPTER 10 Ankle Fractures

Ankle fractures are common, and although joint stability can be regained by adequate reduction and internal fixation of the fracture, some patients have disabling, persistent pain even after joint congruity is completely restored.¹^,² Persistent pain may be associated with exercise or change in the weather, and there may be radiographic evidence of osteoarthritic changes. These features suggest that an articular cartilage lesion or another radiographically nondetectable lesion might have occurred at the time of injury and may be the cause of the pain.

Ankle injuries result from abnormal motion of the talus within the ankle mortise. Fractures of the malleoli can result from impact of the talus on the malleoli caused by rotational or translational forces. Fractures can also occur in tension, and the malleoli can be avulsed because of pull exerted by the intact collateral ligaments to the talus.³^,⁴

Ankle fracture treatment is still based on classification criteria that were created in a time when the ankle was thought to be a simple hinge and only plain radiographs were available to assist diagnosis. This may explain why final results do not always correlate with the extent of bone damage and the reduction and stability achieved. It also suggests the need for specific studies to determine how and to what extent accompanying injuries are predictive factors for outcome in ankle fracture.

Hintermann and coworkers prospectively evaluated the arthroscopic findings in 288 consecutive patients with acute ankle fracture (148 male and 140 female patients; mean age, 45.6 years).⁵ They found that, independent of fracture type, cartilage lesions were most frequently present on the talus and to a lesser extent on the tibia, fibula, and medial malleolus. The frequency and severity of cartilage lesions increased from type B to type C fractures, and there was an increase observed from subgroup 1 to subgroup 3 in both type B and type C fractures. These findings support the belief that the severity of injury directly depends on the height of the fibula fracture. The fact that there was an unexpectedly high incidence of cartilage lesions in all fracture types may explain the observation from daily practice that the final results do not always correlate with the reduction and stability achieved. It seems that the fate of the fractured ankle (i.e., prognosis) may be determined to a significant extent during the accident itself, when the cartilage and other intra-articular and periarticular structures are injured.

Cartilage lesions apparently occur when the talus is rotated or translated in the loaded ankle mortise until the fracture occurs. This is especially true for type C fractures, and it is true to a lesser extent for type B fractures as long as the underlying mechanism is a pronation or rotation movement. Supination trauma, as typically seen in type A fractures, may critically stress the medial half of the joint, but the load forces may not be as high as in pronation or rotation trauma. Taga and colleaues ⁶ found cartilage lesions in the medial joint in 89% of 9 patients evaluated after an acute ankle sprain and in 95% of 22 patients with chronic ankle sprain. They found more cartilage lesions on the distal tibia than on the medial talus. They concluded that these injuries were mainly caused by local stress concentration. They found no correlation between the severity of the cartilage lesion and the degree of instability. This may support the belief that cartilage lesions occur to a significant extent at the time of the acute injury.

A higher incidence of cartilage lesions occurs in female patients than in male patients, and this can be explained by several factors. First, the cartilage may be less resistant to mechanical stress in females.¹ Second, the cartilage may have become more vulnerable with increasing age (because the age of the female patients was significantly higher).⁵ Third, overall muscular and bony strength are lower in females, so that fracture probably occurs during an earlier phase of the injury, and with a higher incidence, exposing the articular surfaces to a higher risk of possible damage. This may be especially true for elderly patients.

Arthroscopy performed directly after ankle fracture can be used to visualize intra-articular lesions that cannot be detected on plain radiographs.⁵^,⁷ Cartilage lesions were found in 79.2% to 90.0% of patients examined arthroscopically.⁵^,⁸ The ligaments could not be identified by arthroscopy in all cases, and there were significant differences among the four ligaments; overall, more injuries to the ligaments were found than expected.⁵ Although its role has not been established in the acute treatment of ankle fractures,⁹ arthroscopy has proved to be valuable for providing detailed knowledge of the fractured ankle.⁵^,¹⁰ It has also been helpful in the treatment of symptomatic osteophytes after ankle fracture.²