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The Influence of Orthotopic Paraspinal Muscle-Pediculated Bone Flaps on Posterior Spinal Fusion in a Canine Model

Study Design. An experimental animal study with randomized, control design was conducted using a dog model. Objective. To construct a novel posterior lumbar spine fusion model with orthotopic paraspinal muscle-pediculated bone flaps and to compare with the conventional posterolateral lumbar intertransverse process fusion. Summary of Background Data. Previous studies have demonstrated that paraspinal musculature provided important vascular ingrowth into the fusion mass. However, the blood supply of paraspinal muscles was still not sufficiently used in spinal fusion. In this study, we assessed the significant role of orthotopic paraspinal muscle-pediculated bone flaps in the healing of bone graft in spinal fusion. Methods. Thirty-two mongrel dogs were randomly assigned to 2 groups to undergo either posterior spinal fusion with orthotopic paraspinal muscle-pediculated bone flaps (treatment group) or posterolateral intertransverse process fusion (control group) at L5–L6 segment. All the fusions used an autologous bone graft obtained from bilateral posterior iliac crests. The animals were killed at 8 weeks or 16 weeks after surgery. The lumbar spines were evaluated by radiology, histology, and biomechanics. Results. Treatment groups showed an increasing trend on radiographic grades, manual palpation, and biomechanical stiffness compared with control groups at 8 and 16 weeks. Histologic analysis revealed that there was more mature woven bone in the treatment group than the controls at both points. At 8 weeks, the histologic fusion rate was 21.4% in the treatment group, 50% in the control group (P < 0.05); and at 16 weeks the fusion rate was 50% and 87.5% in the control group and the treatment group, respectively (P < 0.05). Conclusion. The use of orthotopic paraspinal musclepediculated bone flaps increased the rate and quality of fusion in the experimental spinal fusion model. This suggested that the novel posterior spinal fusion could be further developed for clinical application.