According to our previous retrospective studies, the cross-sectional area (CSA) of hamstring or bone-patellar tendon / BTB autografts after the anatomic anterior cruciate ligament reconstruction (ACLR), increased in the early postoperative period and gradually decreased over time and then reached plateau. As the changing pattern might show the remodeling process of the grafts, the pattern could be affected by the difference of the graft material. However, the direct comparison in the pattern between hamstring and BTB grafts was yet to be investigated. Moreover, their CSAs were not compared with those of the contra-lateral ACL. The purpose of this prospective study to pursue the post-ACLR CSAs in both hamstring and BTB autografts, and to compare them with those of the contra-lateral ACL.
Fifty-two patients consented to prospectively take multiple MRI scans after ACL reconstruction with ACLR with hamstring or BTB autografts. Of 52 patients, the hamstring graft was used for 16 patients (HT group) and BTB graft for 36 patients (BTB group). HT group included 2 males and 14 females with a mean age of 37.2 years. BTB group consisted of 21 males and 15 females with a mean age of 22.7 years. Postoperatively, we used 1.5 Tesla MRI to obtain a proton-weighted oblique axial slice that was perpendicular to the long axis of the graft. Bilateral MRI scans were obtained at 2days after the operation to evaluate both normal ACL and the implanted graft. At 6 months, 1, and 2 years the MRI of the graft was obtained. We measured the CSA at the mid-substance of the ACL and graft with the digital software SYNAPSE. The numbers of MRI scans (HT/BTB group) were 16/36, 12/18, 15/24, 12/25. At each period, the % increase of the graft and the ratio of the grafts’ CSA to those of the contra-lateral ACL were calculated
At 2 days, the average CSA of the graft and ACL in Hamstring / BTB was 33.9±4.7 / 29.7±5.5mm2 and 28.3±5.5 / 33.1±8.7mm2 respectively. The mean percent increase of CSA in HT / BTB group at 6 months , 1, and 2 years was 133.8±17.9 / 169.9±36.4, 133.7±16.3 / 176±38.1, 126±15.5 / 164±37.1% respectively. The percent increase of CSA in BTB group was significantly greater than that of HT group at each period. The ratio of the grafts’ CSA to those of the contra-lateral ACL at 2 days, 6 months, 1, and 2 years was 122.2±19.9 / 96.7±39.7, 157.5±35.9 / 171.0±63.5, 167.8±32.9 / 165.3±48.6, 160.7±30.9 / 156.2±43.5% respectively. There was no significant difference between these two groups.
This study demonstrated CSA change pattern over time of both HT and BTB groups was similar to that of our retrospective study. The percent increase of CSA in BTB group was significantly greater than that in HT group. However, there was no significant differences in the ratio of the grafts’ CSA to those of the contra-lateral ACL between the two groups. Hypertrophy of the graft might be controlled by the individual intercondylar space.