RESUMEN
PURPOSE: The purpose was to evaluate the cross-sectional area changes in hamstring tendon autografts up to 5 years after the anatomic triple-bundle anterior cruciate ligament (ACL) reconstruction. METHODS: A total of 178 MRI scans from 139 patients (35 males, 104 females, mean age 30.4 years) with the anatomic triple-bundle ACL reconstructions were obtained to evaluate the cross-sectional area of the ACL grafts. They were classified into seven groups according to the period from reconstruction to MRI evaluation: Group -2 months (m.), Group 3-6 m., Group 7-12 m, Group 1-2 years (y.), Group 2-3 y., Group 3-4 y., and Group 4 y.-. Intra-operatively, the cross-sectional area of the graft was measured directly using a custom-made area micrometre. Post-operatively, the cross-sectional area of the grafts' mid-substance was measured with oblique axial MRI slices perpendicular to the long axis of the grafts using a digital radiology viewing program. The percent increase in the cross-sectional area was calculated by dividing the post-operative cross-sectional area by the intra-operative cross-sectional area. RESULTS: The mean percent increase in the cross-sectional area in Groups -2 m., 3-6 m., 7-12 m., 1-2 y., 2-3 y., 3-4 y., and 4 y.- was 105.7 ± 14.0, 134.9 ± 20.0, 137.3 ± 27.8, 129.4 ± 22.2, 124.1 ± 20.4, 117.8 ± 16.9, and 117.1 ± 17.2 %, respectively. The percent increase in Groups 3-6 m., 7-12 m., and 1-2 y. was significantly greater than in Group -2 m., while that in Group 4 y.- was significantly less than in Group 7-12 m. CONCLUSIONS: The cross-sectional area of the hamstring tendon autografts after the anatomic triple-bundle ACL reconstruction increases over time up to 1 year post-operatively, decreases gradually thereafter, and reaches plateau at around 3 years. LEVEL OF EVIDENCE: Retrospective case series, Level IV.