Bone Cements and DBM: Not All the Same Bill Rosenblum, MD Professor, Chief of Orthopaedic Trauma Service Georgia Regents University Bone Graft Functions 1. Void filler – Bone gaps – Cyst excisions – Osseous defects • Surgically created • Traumatic injury 2. Improved healing – Assists healing – May help reduce nonunions Roles of Bone Graft Substitutes • Extender – Very large defects – Multiple-level spinal fusions • Enhancer – Improve success of autogenous bone graft • Substitute – Replace autogenous bone graft The Language of Fracture Healing and Bone Graft Substitutes • Osteogenesis • Osteoconduction • Osteoinduction Osteogenesis • Provides precursor cells (stem cells or osteoprogenitor cells) that can differentiate into bone cells • Osteogenic grafts – Autograft Osteogenesis Cancellous Autograft – “Gold standard” – Increased pain & morbidity – Limited amount – Questionable mechanical properties – Costly • OR time • Surgeon’s fee • Length of stay Osteoinduction • Induces precursor cells to differentiate into bone • Bone morphogenetic proteins (BMPs) – BMP-2 (InFUSE™) – BMP-7 (OP-1™) • Demineralized bone matrix (DBX®) • Autograft Osteoconduction • Provides a 3-D scaffold that aids ingrowth of blood vessels and new bone • Osteoconductive grafts: – Norian® SRS® – Calceon® 6 – Demineralized bone matrix (DBX® Putty, Paste, and Mix) – Autograft Cancellous bone Bone Graft Substitutes • • • • • • • Calcium phosphate Calcium sulfate Collagen based matrices Demineralized bone matrix Hydroxyapatite Tricalcium phosphate Osteoinductive proteins Bone Graft Substitutes • Resorption rates vary widely – Dependant on composition • Calcium sulfate - very rapid • Hydroxyapatite (HA) – very, very slow • Some products may be combined to optimize resorption rate – Also dependant on porosity, geometry Bone Graft Substitutes • Mechanical properties vary widely – Dependant on composition • Calcium phosphate cement has highest compressive strength • Cancellous bone compressive strength is relatively low • Many substitutes have compressive strengths similar to cancellous bone • All designed to be used with internal fixation Making the Right Choice* • Match bone graft substitute to clinical need 1. Void filler 2. Improved healing * Intended for use with appropriate internal or external fixation Ceramics • Injectable pastes of calcium phosphate • Norian® SRS® (Synthes) • Alpha BSM® (Etex/Depuy) • BoneSource® BVF (Stryker/Howmedica) • MIIG (Wright Medical) Osteoconductive Calcium Phosphate • Injectable pastes of calcium and phospate – Norian SRS (Synthes/Stratec) – Alpha BSM (Etex/Depuy) – Callos Bone Void Filler (Skeletal Kinetics) Calcium Phosphate • Injectable • Very high compressive strength once • hardens Some studies of its use have allowed earlier weightbearing and range of motion Void Filler • Calcium sulfate – Calceon® 6 (Synthes) – OsteoSet® (Wright Medical) – MIIG™ (Wright Medical) – BonePlast™ (Interpore Cross) Osteoconductive 2. Void Filler • Beta-tricalcium phosphate – chronOS™ (Synthes) – Vitoss™ (Orthovita) – Conduit™ (Depuy) • Hydroxyapatite – ProOsteon® (Interpore Cross) Osteoconductive Calcium Sulfate • Osteoconductive void filler • Low compressive strength – no structural support • Rapidly resorbs Calcium Sulfate • Pellets • Bead kits • Injectable Calcium Sulfate Indications • Filling cysts or cavitary defects • Back-filling bone graft harvest sites Calcium Sulfate • 58 y/o osteopenic female, supracondylar femur fracture Pre-op Post-op 1 year Hydroxyapatite (ProOsteon®) • Prepared from marine coral that is converted to hydroxyapatite, similar to the mineral composition of bone • Interconnected porous structure closely resembles the porosity of human cancellous bone • Resorption rate – very slow ProOsteon Cancellous Bone Assisted Healing • Autogenous bone graft : “Gold Standard” • Demineralized bone matrix: Offers some fracture healing benefits Osteoinductive Potential Demineralized Bone Matrix • Acid extraction of cadaveric human bone leaving: – Collagen – Noncollagenous proteins – Bone growth factors (BMPs) • Growth factor activity is variable between tissue banks and between donors1 • Some products are terminally sterilized, which may further decrease BMP availability2 1. 2. Han B et al. J Orthop Res. 2003; 21(4):648-54. Ferreira SD et al. Clin Ortho Rel Res. 2001; 388:233-9. Demineralized Bone Matrix • Available in different forms from multiple vendors • DBX® (Synthes/MTF) • Grafton® (Osteotech) • AlloMatrix™ (Wright Medical) • Osteofil™ (RTI/Danek) Demineralized Bone Matrix Gel Paste • Combination Putty products with: • DBM chips • Cancellous bone Strips DBM Applications • Filling well-contained bone defects and cysts • Autologous bone graft expander – For posterolateral spine fusions • Osseous voids and gaps Collagen Based Matrices • Highly purified Type 1 bovine dermal fibrillar collagen • Bone marrow is added to provide bone forming cells • Collagraft (Zimmer) – Collagen / HA / Tricalcium phosphate • Healos (Depuy) – Collagen / HA Tricalcium Phosphate • Wet compressive strength slightly less than cancellous bone • Available as blocks, wedges, and granules • Numerous tradenames – – – – – Vitoss (Orthovita) ChronOS (Synthes) Conduit (DePuy) Cellplex TCP (Wright Medical) Various Theri__ names (Therics) Bone Morphogenetic Proteins • Produced by recombinant technology • Two most extensively studied and commercially available – BMP-2 Genetics Institute – BMP-7 (OP-1) Stryker Biotech BMP-2 for Open Tibial Fractures • Prospective, randomized study • 450 patients • All received IM nail and appropriate soft tissue management • Randomized to 3 treatments at time of definitive wound closure • Placebo • 0.75 mg/ml BMP-2/ACS • 1.50 mg/ml BMP-2/ACS BESTT Study Group, et al. J Bone Joint Surg 84A: 2123, 2002. Results • 44% reduction in risk of nonunion/delayed union with high dose BMP-2 • Significantly faster fracture healing • Significantly fewer – invasive interventions – hardware failures – infections BESTT Study Group, et al. J Bone Joint Surg 84A: 2123, 2002. Bone Graft Substitutes How to Choose? • Is the specific clinical need for: – Injectable application? – Placement before or after internal fixation? – Speed of resorption? – Assisted healing? – Is efficacy proven by scientific studies? Dissolution / Remodeling Rates 4+ yrs Years 4 3 2 6 6 mos 6 mos? 1 1 yr 6 wks 6 wks 0 Autograft Calceon 6 DBX chronOS Norian SRS Review Void filler –Calcium sulfate (Calceon® 6, OsteoSet) –Tricalcium phosphate (chronOS™, Vitoss) –Hydroxyapatite (ProOsteon™) –Calcium phosphate (Norian® SRS®, Alpha BSM) Review Assisted healing – Autogenous bone graft (gold standard) – Demineralized bone matrix Thank You
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