Extent of vertical cementing as a predictive factor for radiolucency in revision total knee arthroplasty.

Abstract

Limited information is available regarding the effects of cementing extent on implant stability in patients who have undergone revision total knee arthroplasty (TKA). As such, the goals of this study were: (1) to determine the correlation between the extent of vertical cementing and implant loosening; (2) to determine whether the extent of cementing is a potential predictive factor for radiolucency; and (3) to evaluate the minimal amount of cement needed for a stable implant during revision TKA using a hybrid technique.

One hundred nine stemmed/revision TKAs with a mean follow-up period of 5 years were retrospectively analysed. In each case, a single varus-valgus constrained implant was used and fixed with a hybrid technique. Implant stability was evaluated according to the modified Knee Society radiographic scoring system. The extent of vertical cementing was defined as the longitudinal length from the implant base to the end of the radiopaque line around the stem on radiograph. Its correlation with implant stability was analysed, and the minimal value for a stable implant was evaluated with a receiver operating characteristic (ROC) analysis.

The mean extent of vertical cementing was longer in stable implants (femur: p = 0.001, tibia: p = 0.004) and significantly correlated with implant stability (femur: p < 0.001, tibia: p = 0.001). A logistic regression analysis revealed that the risk of loosening was 8.7-16.1 times higher when the extent of cementing was < 40 mm, which was located at the stem-implant junction of the modular implant. The minimal extent of vertical cementing was estimated to be 60 mm for a stable femoral implant and 50 mm for a tibial implant.

The hybrid fixation technique with a cementing extent > 60 mm for the femur and 50 mm for the tibia was durable at a mean follow-up period of 5 years. Vertical cementing 10-20 mm above the stem-implant junction is recommended when performing revision TKA using this technique.