[MRI study on tendon regeneration after anterior cruciate ligament reconstruction with hamstring tendon autografts]

To evaluate the tendon regeneration after anterior cruciate ligament (ACL) reconstruction with semitendinosus tendon and gracilis tendon autografts by MRI.

Between September 2007 and September 2009, 52 patients undergoing ACL reconstructions with semitendinosus tendon and gracilis tendon autografts were enrolled. There were 29 males and 23 females with an average age of 31.6 years (range, 19-42 years). The left knees were involved in 34 cases and the right knees in 18 cases. The injury was caused by traffic accident in 11 cases, by sports in 38 cases, by heavy pound injury in 2 cases, and by other in 1 case. The time between injury and operation was 6 days to 31 months (median, 11.4 months). Joint pain occurred in 19 cases, joint instability in 28 cases, and joint swelling in 5 cases. The physical examination on admission showed thigh amyotrophy in 7 cases (thigh circumference side-to-side difference > 1 cm) and limitation of joint motion in 2 cases. The results of floating patella test, Lachman test, pivot shift test, and anterior drawer test were positive in 5, 51, 49, and 52 cases, respectively. The range of motion of knee was (127.77 +/- 5.73) degrees, International Knee Documentation Committee (IKDC) score was 49.50 +/- 4.08, and Lysholm score was 52.40 +/- 3.45. Of the patients, 23 were accompanied with medial meniscus tear, 6 with lateral meniscus tear, 2 with plica synovialis, and 1 with loose body.

All incisions healed by first intention. All the patients were followed up 12-18 months (mean, 14.9 months). At 12 months postoperatively, the results of Lachman test and pivot shift test were positive in 1 case, respectively; the results of anterior drawer test were negative in 52 cases. The range of motion of knee was (131.91 +/- 1.81)degrees, Lysholm score was 94.98 +/- 2.77, IKDC score was 93.65 +/- 2.42; and there were significant differences when compared with the preoperative ones (P < 0.05). At 12 months postoperatively, at 90 degrees resisted flexion of the knee, a very distinct fibrous band could be identified on the posteromedial aspect of the knee in 39 cases. MRI showed that both semitendinosus tendon and gracilis tendon regeneration in 10 cases, only semitendinosus tendon regeneration in 29 cases, only gracilis tendon regeneration in 2 cases, and no tendon regeneration in 11 cases. The regeneration rate of the semitendinosus tendon was 75.0% (39/52); the regeneration rate of the gracilis tendon was 23.1% (12/52); and the regeneration rate of the semitendinosus tendon and gracilis tendon was 78.8% (41/52).

MRI results suggest that some of the semitendinosus tendon and gracilis tendon could regenerate after harvested for ACL reconstruction.