The role of nanohydroxyapatite based bone graft in preventing tunnel enlargement after ACL reconstruction with hamstrings: MRI study

Introduction Recently, much attention has been focused on tunnel enlargement phenomenon following Anterior Cruciate Ligament (ACL) reconstruction with hamstrings. The aim of the study was to evaluate the efficacy of the nanohydroxiapatite used as a bone graft in the bone tunnels to prevent this phenomenon possibly allowing a better tendon-to-bone integration. Methods Twenty consecutive male patients operated for ACL reconstruction were enrolled in this prospective study and they were randomly assigned to group A (10 patients, nanohydroxiapatite group) and group B (10 patients, control group). All patients underwent Magnetic Resonance Imaging (MRI) exam ten months after surgery with the aim to evaluate the amount of tunnel enlargement, the signal intensity in the central and in the peripheric part of the graft, and around bone the tunnel. Results Clinical evaluations, KT-1000 arthrometer and knee evaluation scales did not show any difference among the two groups. The mean tibial tunnel diameter increased significantly from 9.04± 0.06 mm to 9.68±0.32 mm in group A and from 9.03±0.26 mm to 10±0.5 mm in group B (p<0.05). No differences were detected on the femoral side instead (p>0.05). In all the examined zones, an earlier and significant evidence of progressive signal hyper-intensity of T2-weighted fat-sat images examined was detected in group A compared to group B. Conclusion The use of the nanohydroxyapatite as a bone graft substitute seems to be efficient in preventing enlargement of tibial bone tunnel after ACL reconstruction with the same fixation devices.