Efficacy of silicated calcium phosphate graft in posterolateral lumbar fusion in sheep.
BACKGROUND
Conditions requiring posterior lumbar spinal fusion remain a clinical challenge. Achieving arthrodesis using autogenous bone graft is inconsistent when rigid internal fixation such as transpedicular instrumentation is applied. Synthetic materials, particularly calcium phosphate-based ceramics, have shown promise for spine fusion applications, especially when combined with autograft. Silicate substitution has been shown to enhance the bioactivity of calcium phosphates and may obviate the need for autologous supplementation.


OBJECTIVE
Determine efficacy of silicated calcium phosphate (Si-CaP) compared with autograft to generate solid lumbar fusion.


METHODS
Comparison of healing of instrumented posterolateral lumbar fusion in ewes at 2 and 6 months using Si-CaP or iliac crest autograft.


METHODS
Eighteen skeletally mature ewes underwent implantation of either autograft or Si-CaP in the space spanning the L4-L5 transverse process. In vivo quantitative computed tomography (CT) scans were made at 2-month intervals and after euthanasia. Harvested spine segments were radiographed and biomechanically tested in bending at 6 months. Histological assessments were made at 2 and 6 months.


RESULTS
Animals receiving Si-CaP graft were biomechanically and radiographically equivalent to those receiving autograft. Fusion mass density and volume were higher for the Si-CaP group throughout the healing period. Si-CaP regenerated normal bone tissue morphology, cellularity, and maturation with no inflammatory responses despite the fact that no autograft, bone marrow aspirate, or blood was mixed with the material. Histomorphometrically, fusion mass was higher for Si-CaP and bony bridging was equivalent when compared with autograft treatment.


CONCLUSIONS
Si-CaP was biomechanically, radiographically, and histologically equivalent to autograft in generating a solid, bony, intertransverse process fusion in an ovine model. Both treatment groups achieved 100% bridging fusion after 6 months of healing.
Wheeler
Donna L
DL
Department of Mechanical Engineering, College of Engineering, Orthopaedic Bioengineering Research Laboratory, Colorado State University, A101 Engineering Building, Fort Collins, CO 80523-1374, USA. BiosolutionsConsulting@comcast.net
Jenis
Louis G
LG
Kovach
Matthew E
ME
Marini
Jason
J
Turner
A Simon
AS
D000818:Animals; D001696:Biomechanical Phenomena; D016025:Bone Transplantation / Q000379:methods*; D002130:Calcium Phosphates / Q000627:therapeutic use*; D005260:Female; D008159:Lumbar Vertebrae / Q000601:surgery; D012756:Sheep; D017640:Silicates / Q000627:therapeutic use*; D013123:Spinal Fusion / Q000379:methods*; D014057:Tomography, X-Ray Computed
D002130:Calcium Phosphates; D017640:Silicates; C020243:calcium phosphate