Preoperative MRI predicts success of knee procedure for older patients

November 30, 2009

Preoperative meniscal extrusion and the severity of cartilage loss and bone marrow edema can be trusted to predict the outcomes of arthroscopic partial meniscectomy in middle-aged and elderly patients.

Preoperative meniscal extrusion and the severity of cartilage loss and bone marrow edema can be trusted to predict the outcomes of arthroscopic partial meniscectomy in middle-aged and elderly patients.

Radiologist Dr. Richard Kijowski and colleagues at the University of Wisconsin Medical Center in Madison were drawn to study the issue because the success rate of arthroscopic partial meniscectomy (APM) in patients older than 45 years is significantly lower than that for younger patients. Overall, APM is the most common procedure performed during knee arthroscopy, Kijowski noted.

The group monitored the postsurgical experience of 100 patients over age 45 for a year after their surgeries to study the relationship between surgical success and pathology detected with preoperative MRI.

A significant improvement in clinical symptoms after arthroscopy was defined as a 20-point difference between postoperative and preoperative assessments performed using the International Knee Documentation Committee standardized evaluation form.

The investigators found positive clinical outcome correlated inversely with the severity of cartilage loss in the medial femoral condyle and medial tibial plateau, the severity of bone marrow edema in the MFC and lateral femoral condyle, and the severity of meniscal extrusion.

For 75 patients who underwent isolated medial APM, Kijowski and colleagues observed another inverse correlation between clinical outcome and the preoperative severity of cartilage loss and bone marrow edema with the MFC and medial tibial plateau.

For the 15 patients undergoing isolated lateral APM, a statistically significant inverse correlation was established between the severity of cartilage loss in the lateral femoral condyle, the lateral tibial plateau, and bone marrow edema within the lateral femoral condyle.

Enough patients were observed in the study for the UW group to calculate odds ratios for improved outcomes from arthroscopy based on preoperative MRI findings. If bone marrow edema was identified within the medial femoral condyle, the patient was found to have a 15-times likelihood of not significantly improving in the year after surgery compared with patients for whom such symptoms did not appear on their preoperative MRI studies, Kijowski said. If cartilage loss was observed in the medial tibial plateau preoperatively, the patient was six times more likely to not significantly improve than patients without such a loss.

"Clinical outcome is inversely correlated with the severity of cartilage loss and bone marrow edema in the same compartment as the meniscal tear and the severity of the meniscal extrusion," he said.