Preliminary documentation of the comparable efficacy of vitoss versus NanOss bioactive as bone graft expanders for posterior cervical fusion

Abstract

Background: Laminectomies with posterior cervical instrumented fusions often utilize bone graft expanders to supplement cervical lamina/iliac crest autograft/bone marrow aspirate (BMA). Here we compared posterior fusion rates utilizing two graft expanders; Vitoss (Orthovita, Malvern, PA, USA) vs. NanOss Bioactive (Regeneration Technologies Corporation [RTI: Alachua, FL, USA]).

Methods: Two successive prospective cohorts of patients underwent 1-3 level laminectomies with 5-9 level posterior cervical fusions to address cervical spondylotic myelopathy (CSM) and/or ossification of the posterior longitudinal ligament (OPLL). The first cohort of 72 patients received Vitoss, while the second cohort or 20 patients received NanOss. Fusions were performed utilizing the Vertex/Rod/Eyelet System (Medtronic, Memphis, TN, USA) with braided titanium cables through the base of intact spinous processes (not lateral mass screws) cephalad and caudad to laminectomy defects. Fusion was documented by an independent neuroradiologist blinded to the study design, utilizing dynamic X-rays and two dimensional computed tomography (2D-CT) studies up to 6 months postoperatively, or until fusion or pseudarthrosis was confirmed at 1 year.

Results: Vitoss and NanOss resulted in comparable times to fusion: 5.65 vs. 5.35 months. Dynamic X-ray and CT-documented pseudarthrosis developed in 2 of 72 Vitoss patients at one postoperative year (e.g. bone graft resorbed secondary to early deep wound infections), while none occurred in the 20 patients receiving NanOss.

Conclusion: In this preliminary study combining cervical laminectomy/fusions, the time to fusion (5.65 vs. 5.35 months), pseudarthrosis (2.7% vs. 0%), and infection rates (2.7% vs. 0%) were nearly comparable sequentially utilizing Vitoss (72 patients) vs. NanOss (20 patients) as bone graft expanders.

Keywords: Autograft; NanOss bioactive; Vitoss; beta-tricalcium phosphate; fusion/pseudarthrosis rates; instrumented fusion; posterior cervical surgery.

Figure 1

This classical midline sagittal T2-weighted MR study showed a marked hyperintense signal in the cervical cord opposite the C5-C6 level and multilevel ventral and dorsolateral compression (shingling of laminae/ossification of the yellow ligament) particularly involving the C4-C5 and C5-C6 levels. This patient successfully underwent a laminectomy of C4, C5, C6 with posterior fusion C2-T2

Figure 2

This classical midline sagittal 2D-CT study documents marked spinal stenosis with CSM accompanied by ventral OPLL (segmental behind the vertebral bodies of C4, C5, C6 with punctate ossification) and marked dorsolateral laminar shingling (e.g., C4, C5, C6 and the leading edge of C7). This patient's myelopathy resolved following a laminectomy of C4-C6 with undercutting of C3 and C7 and posterior C2-T2 fusion

Figure 3

(a) A midline sagittal illustration of multilevel C3-C7 CSM accompanied by both ventral and dorso-lateral compression. (b) Cervical laminectomy C3-C7 for multilevel CSM in the presence of lordosis allows for dorsal cord migration away from ventrally situated osteophytes/pathology.(c) A laminectomy is contraindicated with kyphosis as the cord will fail to migrate posteriorly away from marked ventral compression

Figure 4

Midline Image: Cervical laminectomy C3-C7 is illustrated with medial facetectomy/foraminotomy performed at each intervening level. (a) Filed-down Kerrison punches for posterior cervical surgery. (b). Axial image of ventral cervical osteophyte (c). Down-biting curettes utilized for postero-lateral spur excision (A). Medial facetectomy/foraminotomy for exposure of the nerve root exiting at each level. (B). Use of a nerve hook to dissect/ gently retract the nerve root cephalad/medially in preparation for resection of underlying spur. (C). Use of down-biting curette to remove ventral spur

Figure 5

This 6-month postoperative posterior cervical 2D-CT documented the large fusion mass surrounding the distal intact laminae and spinous processes following the laminectomy of C4 with posterior fusion C2-T2

Figure 6

This parasaggital 2D-CT scan obtained 6 months postoperatively documented bone deposition extending posterolaterally from C2-T2. Also noted was the instrumentation affixed to the spinous processes of C2, C3; this was extended to involve the C7, T1, and T2 spinous processes as well

Figure 7

This 6-month postoperative 2D-CT demonstrated the fusion mass dorsolateral to the facet joints/laminae of C7, T1, and T2

Figure 8

Six-month parasagittal postoperative 2D-CT scan showing the fusion mass/facet fusion from C2-T2

Figure 9

Six-month bone window 2D-CT study showing posterolateral fusion mass overlying the laminae and facet joints at the C6 level. Note the wire/rod complex involving the spinous process of C6