2015 ISAKOS Biennial Congress ePoster #1303

Healing of Tibial Bone Tunnels after Bone Grafting for Staged Revision ACL Surgery: A Prospective Computed Tomography Analysis

Ryohei Uchida, MD, PhD, Nshinomiya, Hyogo JAPAN
Yukiyoshi Toritsuka, MD, PhD, Amagasaki, Hyogo JAPAN
Tatsuo Mae, MD, PhD, Suita, Osaka JAPAN
Kenji Ohzono, MD, Amagasaki, Hyogo JAPAN

Department of Orthopaedic Sports Medicine, Seifu Hospital, Sakai, Osaka, JAPAN

FDA Status Not Applicable

Summary: We quantified the healing of tibial bone tunnels after autogenous iliac bone grafting in patients who underwent two-stage revision ACL reconstruction. Bone tunnels were sufficiently healed at 12 weeks after grafting to enable revision ACL reconstruction and a safer bed for fixation of the ACL graft had developed by 24 weeks after bone grafting by CT scanning.

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Abstract:

Introduction

The two-stage revision ACL reconstruction after bone grafting was occasionally performed in case of tunnel dilation or multi revision. However, there have been no reports with chronological and quantitative evaluation of grafted bone healing and the period from bone grating to staged revision ACL reconstruction was unclear. Therefore, the purpose of our study was to quantify healing of tibial bone tunnels after bone grafting in patients who underwent two-stage revision ACL reconstruction.

Methods

Subjects of this study were six consecutive patients who underwent autogenous bone grafting prior to revision ACL reconstruction due to abnormal anterior laxity after primary reconstruction (3 females and 3 males, average age 26 years). Our indications for two-stage surgery are as follows; 1) enlargement of tibial tunnel aperture to more than 20 mm in diameter, 2) overlap of the tibial tunnel aperture on the anatomical ACL footprint by more than half the tunnel diameter. An autogenous iliac bone block was driven into a new bone tunnel up to the articular surface. CT examinations were performed at 3, 12 and 24 weeks after bone grafting. Evaluations were performed on fifteen axial planes, reconstructed using imaging software, at 1 mm intervals from the articular surface perpendicular to the long axis of the tibia using the following four parameters; occupying ratio (OR), union ratio (UR), and bone mineral density (BMD) of grafted bone and side-to-side BMD ratio. Wilcoxon signed rank tests were used for statistical analyses.

Results

Average ORs were 80, 85 and 92%, and average URs were 43, 74 and 87% at 3, 12 and 24 weeks, respectively. Each parameter was significantly increased between 3 and 12, and between12 and 24 weeks. The average BMD was 578 and 626 mg/cm3 at 12 and 24 weeks respectively, with a significantly higher value at 24 weeks. The average side-to-side BMD ratios both at 12 and 24 weeks were more than 100%.

Discussion

This study was the first report to investigate the quantitative and chronological change of healing between tibial tunnel and grafted bone. Judging from changes in the OR and UR values, our results suggest that the grafted bone made gradual bone formation the new tunnels, macroscopically promoting union to the surrounding bone at 12 weeks, and that these changes had further developed at 24 weeks. Regarding BMD, our results suggest that grafted bone strength increased over the same period because BMD accounts for approximately 70% of bone strength. A previous report assumed that good quality bone around the tunnels resulted in reduced residual anterior laxity in patients who underwent two-stage revision ACL reconstruction (Thomas NP et al, Am J Sports Med]) and our results appear to support their assumption. We believed that this study presents important new quantitative data on the optimum period between grafting and reconstruction.

Conclusion

Bone tunnels were relatively sufficient healing at 12 weeks after autogenous iliac bone grafting to enable revision ACL reconstruction. However, it took 24 weeks for grafting bone to become a safer bed for fixation of the ACL graft.