Risk Factors for Aseptic Loosening After Total Knee Arthroplasty with a Rotating-Hinge Implant: A Case-Control Study.

BACKGROUND

Successful results have been reported in association with the use of a rotating-hinge prosthesis for primary total knee arthroplasty (TKA). The objective of the present study was to identify risk factors for aseptic loosening in patients who underwent primary TKA with rotating-hinge knee prostheses.

METHODS

The records of 1,235 patients who underwent primary TKA with a rotating-hinge prosthesis at our center were evaluated. A total of 125 patients who underwent revision were further evaluated according to the inclusion and exclusion criteria, and 33 patients who underwent revision because of aseptic loosening were then compared with a group of 30 patients who did not require revision surgery. All data, including radiographic measurements, were obtained from records prior to the primary TKA.

RESULTS

On the basis of our review of demographic, anthropometric, clinical, surgical, and radiographic findings, we found that higher body mass index (BMI) was associated with revision. The majority of patients with aseptic loosening had loosening of the femoral component. Furthermore, the inner femoral diameter at 20 cm proximal to the knee joint (on both anteroposterior and lateral images) was found to be predictive of revision among those with aseptic loosening. Receiver operating characteristic curve analysis showed that an inner diameter of the femur of >19 mm on anteroposterior images had a sensitivity of 91% and specificity of 87% for predicting the need for revision surgery in patients with aseptic loosening.

CONCLUSIONS

This is one of few studies that has focused on determining risk factors for the failure of rotating-hinge prostheses following TKA surgery. Our findings indicate that a novel variable, the inner (diaphyseal) diameter of the femur at the point 20 cm proximal to the knee joint, is an extremely reliable predictor of revision surgery in patients with aseptic loosening.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.