Preoperative sizing of meniscal allografts in meniscus transplantation.

The purpose of this study was to determine the accuracy of radiographic and magnetic resonance imaging techniques in preoperative sizing for allograft meniscus transplantation. Twelve cadaveric knee specimens underwent sequential radiographs, magnetic resonance imaging scans, and arthrotomy. Meniscus dimensions were measured in multiple planes for the purpose of determining accuracy of imaging studies in comparison with actual meniscus dimensions. Overall, magnetic resonance imaging proved only slightly more accurate than conventional radiography. The mean difference between magnetic resonance imaging measurements and actual meniscus dimensions was 2.25 +/- 2.04 mm. The mean difference between radiographic measurements and actual meniscus dimensions was 2.35 +/- 1.79 mm. Neither imaging technique was accurate for measuring individual meniscus dimensions, with only 35% of images measuring within 2 mm of actual meniscus dimensions. Using less stringent criteria for accuracy (within 5 mm), radiography and magnetic resonance imaging were 79% and 83% reliable, respectively. Failure to obtain true anteroposterior or lateral images (15 degrees of external and internal rotation) increased measurement inaccuracy. Intraobserver agreement was significantly higher for magnetic resonance imaging than for radiography. Further research into the development of alternative techniques for more reliable meniscus sizing and better understanding of the tolerance for meniscus size mismatch is necessary.