Efficacy of a synthetic calcium phosphate with submicron surface topography as autograft extender in lapine posterolateral spinal fusion

Abstract

Posterolateral spinal fusion (PLF) is a common procedure in orthopedic surgery that is performed to fuse adjacent vertebrae to reduce symptoms related to spinal conditions. In the current study, a novel synthetic calcium phosphate with submicron surface topography was evaluated as an autograft extender in a validated rabbit model of PLF. Fifty‐nine skeletally mature New Zealand white rabbits were divided into three groups and underwent single‐level intertransverse process PLF at L4‐5 using (1) autologous bone graft (ABG) alone or in a 1:1 combination with (2) calcium phosphate granules (ABG/BCP granules ), or (3) granules embedded in a fast‐resorbing polymeric carrier (ABG/BCP putty ). After 6, 9, and 12 weeks, animals were sacrificed and spinal fusion was assessed by manual palpation, Radiographs, micro‐CT, mechanical testing (12 weeks only), histology, and histomorphometry. Based on all endpoints, all groups showed a gradual progression in bone formation and maturation during time, leading to solid fusion masses between the transverse processes after 12 weeks. Fusion assessments by manual palpation, radiography and histology were consistent and demonstrated equivalent fusion rates between groups, with high bilateral fusion rates after 12 weeks. Mechanical tests after 12 weeks indicated substantially lower range of motion for all groups, compared to non‐operated controls. By histology and histomorphometry, the gradual formation and maturation of bone in the fusion mass was confirmed for each graft type. With these results, we describe the equivalent performance between autograft and a novel calcium phosphate material as an autograft extender in a rabbit model of PLF using an extensive range of evaluation techniques. © 2019 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2080–2090, 2019.

Single level posterolateral lumbar fusion in a New Zealand White rabbit (Oryctolagus cuniculus) model: Surgical anatomy, operative technique, autograft fusion rates, and perioperative care

“…The overall mean fusion rates based on manual palpation and radiographic assessment (Lenke Grade A) for PLF with bilateral iliac crest autograft at a 12 week timepoint were 76.9% and 70.0%, respectively. Our results compare favorably with previous reports using autograft alone in PLF 2‐6 . Riordan et al (2013) reported a meta‐analysis of autograft spinal fusions in 733 rabbits across 56 PLF studies 6 .…”

“…Care was taken to ensure that the corticocancellous bone harvested was free of soft tissue as well as excessive blood which can be a source of variation when quantifying the amount. Sharp dissection was used to remove redundant soft tissue and the graft was morselized into small pieces (<5 mm) 3 (Figure 3). For cases where an alternative graft material was being evaluated, 2 cc (which equates to approximately 1.7 g) of autograft was harvested unilaterally.…”

“…Decortication was performed using a high‐speed pneumatic surgical drill (Midas Rex, Medtronic, Memphis, Tennessee ) with an M‐8 Matchstick Burr. The central portion of the transverse processes were carefully decorticated for a distance of 10 mm from the vertebral body and pars to a level where bleeding bone beds were visually present to the surgeon 3 (Figures 7 and 8). Great care was taken to decorticate the bone, creating a bleeding bone bed in preparation for placement of graft material over the transverse processes.…”

“…The New Zealand White (NZW) ( Oryctolagus cuniculus ) rabbit model of posterolateral lumbar fusion (PLF) has been widely used for spinal fusion research since it was first described by Boden et al 1 The gold standard for successful spinal fusion is traditional autogenous iliac bone graft, which has a reported fusion rate ranging from 50% to 90% 2‐6 . The NZW rabbit PLF model is not stabilized with any posterior fixation and is considered a noninstrumented model that has been used for evaluation of the in vivo performance of bone graft substitutes and biological materials, 2‐5,7 as well as the effect of medications such as opioids, 8 nonsteroidal anti‐inflammatories, 9 and antibiotics 10 on spinal fusion. A complete list of the studies using this model is beyond the scope of this manuscript.…”

Posterior Thoracolumbar Hemivertebra Resection and Fusion with a Biphasic Calcium Phosphate Bone Graft with a Novel Submicron Surface Topography

“…A harvest of local, or iliac crest bone graft in sufficient volume for a multi-level fusion procedure is often prohibitive due to the volume of autograft bone required for each of the levels to be fused, as was the case for the patient described herein. Although synthetic bone graft options have historically performed less well compared to autograft [12], this case exhibits the benefits associated with the use of this biphasic calcium phosphate with needle-shaped submicron surface topography in achieving a reliable and solid fusion.…”