Surgery/Biomechanics: Nonunions - Student Notes PDF

Surgery/Biomechanics: Nonunions Sean T. Grambart DPM FACFAS Differentiate Identify Differentiate between delayed, nonunion and malunion Identify the evaluation of patients with bone healing problems Objectives knowledge of biophysical principles and Demonstrate Demonstrate indications behind the var...

Surgery/Biomechanics: Nonunions Sean T. Grambart DPM FACFAS Differentiate Identify Differentiate between delayed, nonunion and malunion Identify the evaluation of patients with bone healing problems Objectives knowledge of biophysical principles and Demonstrate Demonstrate indications behind the various types of bone stimulators Recognize Recognize types of bone grafts and indications for grafting Nonunion A fracture that is a minimum of 9 months post occurrence and is not healed and has not shown radiographic progression for 3 months Orthopaedic Advisory Panel: Food & Drug Administration, 1986 Fracture that, in the opinion of the treating physician, has no possibility of healing without further intervention 33 Delayed Union Fracture that shows slower progression to healing than anticipated and it’s at risk of non-union without further intervention Shows healing progress over time 4 Malunion Term used to indicate that osseous healing has occurred, but that it has healed in less than an optimal position 5 Hypertrophic Nonunion Atrophic Nonunion Types of Nonunion Oligotrophic Septic Nonunion Pseusoarthrosis 6 Hypertrophic Nonunion Shown by radiographically abundant callus formation There is no bridging bone, and the ends are not united There is adequate blood supply and biology but inadequate stability 7 Elephant’s Foot Horse’s Huff Type of Hypertrophic Nonunions 8 8 Atrophic Nonunion Evidenced by radiographically absent callus Poor biology Lack of blood supply Inadequate fixation? Inadequate joint preparation? 9 Types of Atrophic Nonunion Torsion wedge Comminuted fracture nonunion, necrotic intermediate fragment Defect atrophic nonreactive 10 Oligotrophic Nonunion Combination of atrophic and hypertrophic in that there is incomplete callus formation 11 Septic Nonunion Reduction in blood flow from organisms consuming the nutrition to healthy bone Decreases the new bone formation 12 Pseudoarthrosis Typically has adequate vascularity Excessive motion/instability False joint forms over significant time 13 Types of Bone Healing Direct (Primary) ‘Absolute Stability’ of bony surfaces Close contact of less than 0.15 mm Minimal inter-fragmentary strains of less than 2% Compression lag screw or compression plating 14 Types of Bone Healing Secondary (Indirect) ‘Relative Stability’ of bony surfaces Fracture hematoma formation Inflammation Cellular proliferation and differentiation and Remodeling 15 Factors for Osseous Healing Cellular environment Growth factors Bone matrix Diamond Concept Mechanical stability 16 Etiology of Nonunion Diamond Concept Osteoinductive Mediators Vascular endothelial growth factor (VEGF) also play Platelet-derived growth factor (PDGF) Fibroblast growth factor (FGF) Insulin-like growth factor (IGF) Transforming growth factor beta (TGFβ) Bone morphogenic protein (BMP)-2, 4, 6 and 7 19 Diamond Concept Osteogenic Cells Committed osteoprogenitor cells (periosteum) Undifferentiated multipotent stem cells (MSCs) (bone marrow) Proliferation and differentiation of MSCs, leading to simultaneous hard and soft callus formation Critical in guiding this process are the BMPs 21 21 Osteogenic Cells Committed osteoprogenitor cells (periosteum) Undifferentiated multipotent stem cells (MSCs) (bone marrow) Proliferation and differentiation of MSCs, leading to simultaneous hard and soft callus formation Critical in guiding this process are the BMPs 22 22 Diamond Concept Osteoconductive Matrix Extracellular matrix Scaffold and promoting migration and adhesion of osteoinductive and osteogenic cells to the fracture site With good apposition of bone, necrotic bone at the fracture site serves this purpose If there is insufficient ‘natural’ scaffold, then autograft and/or allograft demineralised bone matrix (DBM) 24 Diamond Concept Mechanical Stability In the presence of appropriate growth factors… Tension encourages fibroblasts Shear encourages chondroblasts Combination of compression/distraction encourages osteoblasts For ossification to occur, the fracture gap must have reduced to an appropriate level Ideally less than 2 mm Anything gap > 6 mm, little callus is seen to form 26 Diamond Concept Risk Factors for Nonunion 28 Diamond Concept Patient Work-Up History Physical Open versus closed Surgery (Type, Fixation) Smoker Diabetes Vascular disease Vitamin D NSAIDs Steroids Pain Sinus tracts Drainage Movement 30 30 Nicotine Use Decreases peripheral oxygen tension Dampens peripheral blood flow Well documented difficulties in wound healing in patients who smoke Increased risk of NONUNION Overall 15% higher 4x Greater Risk 31 31 Nonunion should be considered infected until proven otherwise Dramatic association between deep infection and nonunion Debridement, debridement, debridement Infection Multiple cultures. Identify the bacteria Infectious disease consult is helpful Infected bone requires stability to resolve infection May achieve union in the presence of infection with appropriate treatment 32 Patient Work-Up Lab Work Up Rule-Out Infection Radiographs WBC with Diff ESR CRP CMP Vit D Levels Callus Formation Fixation CT Scan?? 33 33 Communication Treatment Non-operative Operative 34 Non-Operative Treatment Electrical stimulation Ultrasound Extracorporeal shock wave therapy Immoblization 35 Electrical Stimulation Applied mechanical stress on bone generates electrical potentials Compression = electronegative potentials = bone formation Tension = electropositive potentials = bone resorption Basic science suggests e-stim upregulates TGF-β and BMP’s suggesting osteoinduction 36 Contraindications for Electrical Stimulation Synovial pseudoarthrosis Electric stimulation does not addressassociated problems of angulation, malrotation and shortening – deformity!! 37 Ultrasound Piezoelectric transducer generates an acoustic pressure wave Some evidence to show faster healing in fresh fractures Evidence is moderate to poor in quality with conflicting results 38 Extracorporeal Shock Wave Therapy (ESWT) Single impulse acoustic wave with a high amplitude and short wavelength Microtrauma induced in bone thought to stimulate neovascularization and cell differentiation 39 Operative Treatment Debridement and hardware removal Plate osteosynthesis Intramedullary nailing External fixation Autogenous bone graft Bone marrow aspirate Allograft bone Demineralized bone matrix BMP’s Platelet concentrates 40 Autologous Bone Graft Considered the “gold standard” Osteoinductive - proteins and other factors promoting vascular ingrowth and healing Osteogenic – contains viable osteoblasts, progenitor cells, mesenchymal stem cells Osteoconductive - contains a scaffolding for which new bone growth can occur 41 Operative Strategy Define nonunion type Hyper-, oligo-, atrophic, or pseudarthrosis Nonunion location – diaphysis vs metaphysis Infected vs Aseptic Deformity? Patient/host factors Goals and expectations 42 Non-union Crescentic 62 y/o smoker s/p crescentic 2 Month p/o admitted for cellulitis and edema at osteotomy site MRI showed fluid collection Needle aspiration cultured Staph a. (s) IV Abx resolved infection Bone stim at 5 months 43 6 months S/P Crescentic 44 Orthobiologics 52 53 54 55 56 57 58 59 Thank You 60