MRI may miss over half of knee chondral lesions

Researchers found that 43.6% of all arthroscopic surgeries had defects.

Surgeons using magnetic resonance imaging alone to detect chondral lesions may miss 55% of defects found during arthroscopic procedures, according to Chilean researchers.

In a prospective study of 190 patients undergoing knee arthroscopic surgery, investigators discovered that preoperative MRI only detected chondral lesions in 27 of the 82 cases found during surgery.

The findings show that while MRIs may carry a 100% specificity rate for categorizing these lesions, they are only 45% sensitive to catching them.

“Based on our results, we recommend that the instrumentation for the different cartilage repair for the knee should always be available at the time of the arthroscopic procedure, [due to] the high possibility of finding previously undiagnosed chondral lesions,” said Alex Vaisman, MD, an orthopedic knee and shoulder specialist with the Universidad Del Desarrollo in Santiago, Chile.

Lesion size and age linked

Vaisman and his colleagues also discovered that lesion size highly correlated with patient age (P=.001).

“The direct correlation between age and size of defect suggests an articular degenerative process with age,” he said during his presentation at the 6th Symposium of the International Cartilage Repair Society. Yet, they found no significant correlation between patient age and the number of defects.

Researchers examined 250 consecutive surgeries performed at a single center between March 2003 and February 2004. They included patients with ACL and meniscal tears and excluded cases without preoperative MRIs and osteoarthritis, the researchers wrote in their abstract. A final study cohort of 190 patients included 74 women and 116 men with an average age of 34.8 years. “The time between the MRI and the time of surgery did not exceed one year in all cases,” Vaisman said.

Arthroscopic findings vs. MRI

Surgeons discovered 115 lesions in 82 patients during arthroscopic procedures. “Most of them were single lesions — 72% of them — 23% were two lesions and 5% were three or more lesions at the time of arthroscopy,” Vaisman said. The average lesion measured 1.99 cm², and most lesions occurred in the medial femoral condyle (31%). International Cartilage Repair Society type 2 or 3-A lesions proved the most common, occurring in 62.5% of cases. The rarest lesion they found was 4-B type, he added.

Of the arthroscopically discovered lesions, preoperative MRIs detected defects in 27 patients. “MRI sensitivity is correlated with the type of lesion according to the ICRS classification,” Vaisman said. Researchers discovered that the technique demonstrated the greatest accuracy for type 4 lesions and the least for type 1 defects. Regarding defect location, the imaging showed the greatest sensitivity for targeting patella lesions (53%).

The research highlights the limits of MRIs while exploring the prevalence of knee chondral lesions.

“Chondral defects are a common problem in patients with knee symptoms that require arthroscopic surgery,” Vaisman said. “In our study, we found chondral lesions in 43.6% of 190 arthroscopies.”

For more information:
Figueroa D, Calvo R, Vaisman A. Knee chondral lesions: Incidence and correlation between arthroscopic and magnetic resonance findings. #3c-1. Presented at the 6th Symposium of the International Cartilage Repair Society. Jan. 8-11, 2006. San Diego.