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.

Lumbar Intrafacet Bone Dowel Fixation

BACKGROUND: The efficacy of intrafacet bone dowels in promoting lumbar fusion has not been established. A recently published study indicates a low fusion rate, along with device migration. OBJECTIVE: To evaluate the mechanical stability of 2 lumbar facet fixation technologies before and after repeated cyclic loading. METHODS: Six human lumbar specimens were implanted with both types of allograft, one at L2-3 and the other at L4-5, on a randomized basis. All specimens were subjected to pure-moment flexibility testing before and after implantation and after 2500 and 5000 cycles of flexion-extension bending. Each specimen was scanned with computed tomography before and after cyclic loading to measure device migration. RESULTS: Only dowel 1 resulted in a statistically significant reduction in flexion-extension range of motion at the treatment level. This reduction was significant at baseline testing (P = .03) and after 2500 cycles of flexion-extension loading (P = .048) but was not significant after 5000 cycles of loading. One of the bone dowels extruded posteriorly out of the joint space during baseline axial torsion flexibility testing, which was before any cyclic loading. CONCLUSION: The data obtained in this study do not indicate efficacy of fixation for cylindrical bone dowels in the lumbar facet joint. Significant fixation was detected only for one of the devices and was no longer present after a relatively short duration of repeated loading. Furthermore, considerable magnitudes of device migration were detected.