Potential cost savings of MR imaging obtained before arthroscopy of the knee: evaluation of 50 consecutive patients.

OBJECTIVE: We attempted to determine the potential cost savings of prearthroscopic knee MR imaging examinations.

SUBJECTS AND METHODS: This prospective study involved 50 consecutive patients. The patients met the surgical-indications-for-monitoring-appropriateness criteria for knee arthroscopy and underwent MR imaging of the knee before arthroscopy. For all patients, we compared MR imaging and arthroscopic findings. On the basis of a cost of $1000 for each MR imaging examination and $4000 for each diagnostic arthroscopy, we decided that cost-effective MR imaging would require 25% true negativity.

RESULTS: The respective sensitivities and specificities of MR imaging of the knee were 100% and 90% for revealing anterior cruciate ligament interruption, 100% and 84% for revealing posterior cruciate ligament tears, 90% and 97% for revealing medial meniscal tears, 60% and 100% for revealing lateral meniscal tears, and 94% and 93% for revealing composite injury (one or more of these abnormalities). With MR imaging examinations obtained before surgery, we found 21 (42%) of 50 arthroscopies to be unnecessary.

CONCLUSION: Despite stringent clinical criteria used in selecting patients for arthroscopy, 42% of our patients could have been spared surgery on the basis of the anatomy revealed by MR imaging. Our study indicates that MR imaging obtained before arthroscopy of the knee can produce a savings of as much as $680 per MR imaging examination performed on the knee.