Is lumbar facet fusion biomechanically equivalent to lumbar posterolateral onlay fusion? J Neurosurg Spine 2017 May;26(5):586-593
Date
02/06/2017Pubmed ID
28156207DOI
10.3171/2016.10.SPINE16649Scopus ID
2-s2.0-85018363675 (requires institutional sign-in at Scopus site) 5 CitationsAbstract
OBJECTIVE This study was designed with the following research objectives: 1) to determine the efficacy of facet fusion with recombinant human bone morphogenetic protein-2 (rhBMP-2) on an absorbable collagen sponge (ACS) in an ovine lumbar facet fusion model; 2) to radiographically and histologically compare the efficacy of lumbar facet fusion with rhBMP-2/ACS to facet fusion with an iliac crest bone graft (ICBG); and 3) to biomechanically compare lumbar facet fusion with rhBMP-2/ACS to lumbar posterolateral fusion (PLF) with ICBG. METHODS The efficacies of the 3 treatments to induce fusion were evaluated in an instrumented ovine lumbar fusion model. Eight sheep had 10 cm3/side ICBG placed as an onlay graft for PLF at L2-3. At the adjacent L3-4 level, 0.5 cm3/side ICBG was placed for facet fusion. Finally, 0.5 cm3/side rhBMP-2/ACS (0.43 mg/ml) was placed for facet fusion at L4-5. CT scans were obtained at 2, 4, and 6 months postoperatively with 2 reviewers conducting an evaluation of the 6-month results for all treated spinal levels. All 8 sheep were killed at 6 months, and all posterolateral instrumentation was removed at this time. The spines were then sectioned through L3-4 to allow for nondestructive unconstrained biomechanical testing of the L2-3 and L4-5 segments. All treated spinal levels were analyzed using undecalcified histology with corresponding microradiography. Statistical comparisons were made between the treatment groups. RESULTS The PLF with ICBG (ICBG PLF group) and the rhBMP-2 facet fusion (rhBMP-2 Facet group) treatment groups demonstrated similar levels of stiffness, with the rhBMP-2 Facet group having on average slightly higher stiffness in all 6 loading directions. All 8 levels in the autograft facet fusion treatment group demonstrated CT radiographic and histological fusion. All 8 levels in the rhBMP-2 Facet group showed bilateral CT radiographic and histological fusion. Six of 16 rhBMP-2/ACS-treated facet defects demonstrated small intraosseous hematomas or seromas. Four of the 8 levels (50%) in the ICBG PLF treatment group demonstrated bilateral histological fusion. Three of 8 levels in the ICBG PLF treatment group showed unilateral fusion. One of the 8 levels in the ICBG PLF treatment group demonstrated bilateral histological nonfusion. CONCLUSIONS Both rhBMP-2/ACS and autograft demonstrated 100% efficacy when used for facet fusion in the instrumented ovine model. However, the ICBG PLF treatment group only demonstrated a 50% bilateral fusion rate. Biomechanically, the ICBG PLF and rhBMP-2 Facet groups demonstrated similar stiffness in all 6 loading directions, with the rhBMP-2 Facet group having on average slightly higher stiffness in all directions.
Author List
Toth JM, Foley KT, Wang M, Seim HB 3rd, Simon Turner AAuthors
Jeffrey M. Toth PhD Associate Dean for Research in the School of Dentistry department at Marquette UniversityMei Wang PhD Associate Professor in the Orthopaedic Surgery department at Medical College of Wisconsin
MESH terms used to index this publication - Major topics in bold
Absorbable ImplantsAnimals
Biomechanical Phenomena
Bone Density Conservation Agents
Bone Morphogenetic Protein 2
Bone Transplantation
Collagen
Drug Implants
Female
Ilium
Lumbar Vertebrae
Microradiography
Models, Animal
Recombinant Proteins
Sheep
Spinal Fusion
Tomography, X-Ray Computed
Transforming Growth Factor beta
Treatment Outcome
