Persistent stability 3 years after reconstruction of the anterior cruciate ligament. A radiostereometric analysis (RSA) of 20 patients.

We measured, by radiostereometric analysis (RSA), the sagittal knee laxity in 20 consecutive patients with chronic anterior cruciate ligament injuries before, 1 year and 3 years after reconstruction with a free bone-patellar tendon-bone graft. The grafts had been perioperatively tensioned, using a 10-15 N load. An increased displacement with increasing load was present before reconstruction, but we found no differences between 100 and 150 N stress load 1 and 3 years after the operation. The total anteroposterior displacement decreased from 12.7 mm before the reconstruction to 5.1 mm 1 year and 5.6 mm 3 years postoperatively, using a stress load of 150 N. Thus, we found both a definite end-point of joint displacement and persistent stability without elongation of the graft with time, when care was taken not to over-constrain the knee by a high initial graft tension.