Allograft Bone Dowel Incorporation to Tibial and Femoral Tunnels in Two–Stage Revision Anterior Cruciate Ligament Reconstruction (173)

OBJECTIVES: The purpose of this study was to quantitatively evaluate the radiographic outcomes of allograft dowels used as bone grafts in two-stage revision anterior cruciate ligament reconstruction (ACLR). METHODS: Prospective review of patients who underwent 2-stage revision ACLR with allograft bone dowels. Inclusion criteria were tibial/femoral tunnel diameter of >14 mm on pre-operative computed tomography (CT), overlapping prior tunnels with new tunnels (Figure 1). Allograft dowels were placed during the first stage and arthroscopic assessment of dowels was performed at the second-stage revision (Figure 2). Quantitative analysis of radiographic incorporation rates was performed with the Union Ratio (UR, Figure 3A) and Occupying Ratio (OR, Figure 3B) on post-operative CT scans. Biopsy specimens were obtained to analyze incorporation. RESULTS: 21 patients were included. Second-stage revision surgeries were performed at 6.5 months (SD, 2.1 months) after first-stage revision. All dowels preserved their integrity without any signs of degradation and complete incorporation at the host bone and graft junction at the second stage procedure. The average diameter of the dowels placed in tibial tunnels were greater than those placed in femoral tunnels (16.1 mm [SD, 2.3 mm] vs 12.4 mm [SD, 1.6 mm]; p = < .05). CT scans were obtained at 121 days (SD, 28 days) after the first-stage. There was no difference between the OR of femoral and tibial tunnels (87.6% [SD, 4.8%] vs 85.7% [SD, 10.1%]; p = .484), however, the UR was significantly higher in femoral tunnels (74% [SD, 10.5%] vs 83%[ SD, 6.2%], p = 0.005). Histological examination revealed osseous incorporation between the host bone and allograft dowel (Figure 4). CONCLUSIONS: Allograft bone dowels are a safe graft choice to replenish bone stock in the setting of a staged revision ACL reconstruction and dowels placed in femoral tunnels had a higher healing union ratio. Further studies are warranted to evaluate long-term clinical outcomes in this subset of patients.