The effect of osseous ankle configuration on chronic ankle instability.

BACKGROUND

Chronic ankle instability (CAI) is a common orthopaedic entity in sport. Although other risk factors have been studied extensively, little is known about how it is influenced by the osseous joint configuration.

AIM

To study the effect of osseous ankle configuration on CAI.

DESIGN

Case-control study, level III.

SETTING

Radiological examination with measurement of lateral x rays by an independent radiologist using a digital DICOM/PACS system.

PATIENTS

A group of 52 patients who had had at least three recurrent sprains was compared with an age-matched and sex-matched control group of 52 healthy subjects.

MAIN OUTCOME MEASURES

The radius of the talar surface, the tibial coverage of the talus (tibiotalar sector) and the height of the talar body were measured.

RESULTS

The talar radius was found to be larger in patients with CAI (21.2 (2.4) mm) than in controls (17.7 (1.9) mm; p<0.001, power >95%). The tibiotalar sector, representing the tibial coverage of the talus, was smaller in patients with CAI (80 degrees (5.1 degrees )) than in controls (88.4 degrees (7.2 degrees ); p<0.001, power >95%). No significant difference was observed in the height of the talar body between patients with CAI (28.8 (2.6) mm) and controls (27.5 (4.0) mm; p = 0.055).

CONCLUSION

CAI is associated with an unstable osseous joint configuration characterised by a larger radius of the talus and a smaller tibiotalar sector. There is evidence that a higher talus might also play some part, particularly in women.