MRI reduces need for knee arthroscopy

Data from the first study of its kind suggest that MR imaging makes more sense diagnostically than arthroscopy in patients with possible knee pathology. Dutch researchers published results from the multicenter trial in the January issue of Radiology.

Invasive imaging procedures should be restricted to the treatment side of the management algorithm or cases in which noninvasive diagnostic techniques don't work, according to investigators led by Dr. Patrice W.J. Vincken, a radiologist at Leiden University Medical Center.

Vincken and colleagues prospectively assessed 584 patients who underwent MRI over a period of two and a half years. During this time, only patients with positive MR findings for knee abnormalities (group A) went straight to arthroscopy. All others were randomly assigned to undergo either conservative (group B) or arthroscopic (group C) treatment.

Based on the outcomes of patients with negative MR findings, the researchers found that arthroscopy and conservative management shared similar effectiveness and costs.

About 50% of the 584 patients had positive MR findings and joined group A. Groups B and C each made up about a quarter of the sample. On average, the number of patients effectively treated in group B was 5.1% larger than those in group C. The calculated societal costs were lower when using MRI. Albeit not statistically significant, most positive findings fell on the side of noninvasive imaging.

Although the economic analysis - reported in U.S. dollars using the 2005 Dutch consumer price index - was specific to the Netherlands' experience, the outcome could prove similar in other countries where MR scanners are readily available. Data suggest that using a strategy involving MR imaging will significantly reduce societal costs when the prevalence of MR-found abnormalities remains below 75%. The decision to use or not to use the MR imaging strategy goes beyond effectiveness and cost, however, and involves the ability to prevent unnecessary arthroscopy, the researchers said.

"When an arthroscopic procedure is not performed for therapeutic purposes, no health gain can be expected from it. The prolonged morbidity after diagnostic arthroscopy, compared with that after MR imaging, and the risk of complications with arthroscopy may guide the decision of the orthopedic surgeon and the patient to use MR imaging initially," they said.

The study had limitations. Findings, obtained using a 0.5T system, may not extrapolate to countries with different economic and healthcare patterns. In addition, arthroscopic techniques have changed since 2000, when the last arthroscopies were performed in the Dutch study.

Recent studies show, however, that field strength does not significantly affect MR's performance in the detection of meniscal abnormalities, which were the main indication for arthroscopy in this study population.

For more information from the Diagnostic Imaging archives:

MR imaging offers integral view of articular cartilage repair

Radiologic signs more than double sensitivity of MRI of the knee

Radiologists look over their shoulders, knees, and hips

Survey identifies orthopedists' preferences for MR knee reports