Objective: The current trends in anterior cruciate ligament (ACL) reconstruction aim not only to restore the position and footprint of the native ACL, but also its shape and biomechanical function. The objective of our study was to determine whether the in vivo shape of the healed graft differs from the native ACL.
Patients and methods: We performed bilateral MRI examinations on patients with successful unilateral ACL reconstruction for an average period of 3 years. The imaging acquisitions were performed using 1.5 T field strength and T2 FSE axial oblique sequence at 2 mm spacing. We than averaged the ratio between the maximum width and thickness as well as the surface area in pixels using ImageJ (National Institutes for Health) and compared it with the native ACLs using the paired t-test.
Results: For both quadrupled hamstrings and B-PT-B neoligaments, the mid-portion area was significantly higher (p < 0.001) than the native contralateral ACL: 41.82/31.39 mm2 and 37.05/32.08 mm2, respectively. The surface area of the neoligaments mid-portion was on average 33.23% higher than the native ACL for the quadrupled hamstrings and 15.49% for the B-PT-B, respectively. The native contralateral ACL was also significantly thinner throughout the mid-portion (p < 0.001) than both B-PT-B and quadrupled hamstrings neoligaments, with a width-thickness ratio of 2.57 vs 1.97 and 2.57 vs 1.39, respectively.
Conclusions: Our study showed that, several years after successful anatomic single bundle ACL reconstruction using an ipsilateral autograft, the mid-portion shape and cross-sectional area are not restored compared to the uninjured contralateral knee. This effect was more prevalent with hamstrings and less prominent when B-PT-B were used.