Evaluation of periprosthetic lucency after total ankle arthroplasty: helical CT versus conventional radiography.

BACKGROUND: Osteolysis after total ankle arthroplasty (TAA) has become a major concern regarding long-term implant survival. The primary goal of this study was to determine whether CT was more sensitive than plain films in detecting the presence and extent of periprosthetic lucency. A secondary goal was to determine whether lack of syndesmotic fusion was associated with more extensive lucency.
METHODS: Seventeen patients (19 ankles) who had TAA between 2001 and 2003 were consecutively recruited and evaluated as part of a prospective study. Plain radiographs and helical CT with metal-artifact minimization were obtained. Evidence of lucent lesions and syndesmotic fusion was compared using the different imaging techniques.
RESULTS: Of the 19 ankles imaged, a total of 29 lesions were detected by CT, whereas plain radiographs detected 18 lesions. CT detected 21 lesions less than 200 mm(2), of which plain radiographs detected only 11. The mean size of the lesions detected on CT was over three times larger than the size on plain radiographs. With the small sample size used, there were no statistically significant differences between ankles with and without fusion of the syndesmosis and the extent (p = 0.84) and location (p = 0.377) of lucency.
CONCLUSION: CT is a more accurate method for early detection and quantification of periprosthetic lucency than plain radiographs. Accurate evaluation of lucent lesions may identify patients at high risk for lack of syndesmotic fusion with subsequent loosening and implant failure.