Laxity and graft fixation after reconstruction of the anterior cruciate ligament. A roentgen stereophotogrammetric analysis of 11 patients.

The sagittal laxity of the knee was measured in 11 consecutive patients with chronic anterior cruciate ligament deficiency before and 1 year after ligament reconstruction with a free bone-tendon-bone graft from the patellar tendon (modified Clancy technique). Tantalum markers were implanted in the femur, in the tibia, and in the graft for roentgen stereophotogrammetric analysis (RSA) of the sagittal laxity and the migration of the bony ends of the graft. The precision in measurements of total anterior-posterior displacement (+/- 2 SD of the differences between repeated measurements) was 2.2 mm. A decrease in total anterior-posterior displacement from 12 mm before reconstruction of 5 mm 1 year postoperatively using a stress load of 150 N was found. The bony ends of the free graft migrated maximally 0.7 mm, implying adequate fixation.