Patellar tendon defect during the first year after anterior cruciate ligament reconstruction: appearance on serial magnetic resonance imaging.

The purpose of this study was to use magnetic resonance imaging to evaluate various parameters of the patellar tendon during the first year after harvest for anterior cruciate ligament (ACL) reconstruction. Twelve consecutive patients were serially imaged on a 1.5 Tesla GE magnet (GE Medical Systems, Milwaukee, WI) with a dedicated knee coil at 3 weeks, 3 months, 6 months, and 1 year after undergoing ACL reconstruction using a central one-third patellar tendon autograft. The tendon defect was not closed primarily, but the paratenon was approximated. The following measurements were performed: tendon width, defect width, cross-sectional area of the tendon, and tendon length. In addition, the patellar bone harvest site was evaluated for healing. The width of the tendon defect decreased by 62% over 12 months (P < .05). Only two patients showed complete closure of the defect. Tendon width was noted to decrease by 6.5% (P=.017). The ratio of defect width to overall tendon width (designated R) decreased by 58% (P < .05). Tendon length was noted to decrease during this by 8% (P=.037). The tendon cross-sectional area was noted to increase by 9% at 1 year, but this was not found to be statistically significant (P=.39). One year after ACL reconstruction using a central one-third patellar tendon, the tendon defect has begun to reconstitute itself but there is still a significant gap. This persistent defect must be taken into consideration when planning revision ACL surgery using reharvest of the central one third of the patellar tendon. The entire tendon also exhibits a reduction in width and length, while cross-sectional area increases slightly. Complete healing of the graft defect can not be assumed at 12 months post-ACL reconstruction.