Bone healing

BONE HEALING

Dr BASSEY, A EORTHOPAEDICS & TRAUMA

UATH, ABUJA

OUTLINE• Introduction• Types of bone healing• Stages of bone healing• Regulation of bone healing• Factors affecting bone healing• Assessment• Complications • Current trends• Conclusion

Introduction

• Bone healing refers to complex and sequential events that occur to restore injured bone to pre-injury state

• Bone injury remains a constant counterpart to human existence, we are able to cope with this due to bone healing. The surgeon must therefore have adequate understanding of its processes, influencing factors and complications in order to achieve optimum outcome

Types of bone healing• Healing by callus formation (indirect,

secondary)• Healing by direct union (primary)

Stages of bone healing• Healing by callus formation– Haematoma formation• Occurs immediately

– Inflammation and cellular proliferation• 8hrs to 1-2weeks• Migration of inflammatory cells (macrophages,

neutrophils, platelets)• Elaboration of cytokines, growth factors, other

mediators• Proliferation and differentiation of mesenchymal stem

cells, migration of fibroblasts and osteoclasts• neovascularization

Stages of bone healing

• Healing by callus formation– Callus formation• 2-3wks to 4-8wks• Osteoclasts mop up dead bone• Collagen matrix formation• Osteoid deposition and mineralisation• Formation of woven bone

– Consolidation• Weeks to 2-3mnths• Lamellar bone formation• Remaining gaps filled by lamellar bone

Stages of bone healing• Healing by callus formation– Remodelling• 2mnths to years• Guided by stress exposure• Osteoclasts are responsible

• Healing by direct union– Occurs in fractures where ends are compressed,

with intervening space <500microns– No callus formation– Gap healing – occurs if space is 200-500microns– Contact healing – occurs if space is <200microns

HAEMATOMA INFLAMMATION CALLUS CONSOLIDATION REMODELLING

Regulation of fracture healing• Local factors– TGF-B– PDGF– FGF– IGF– VEGF– BMP– Cytokines

• Systemic factors– Hormones

Regulation of fracture healing• TGF-B– Promotes proliferatn & diff of stem cells– Stimulates collagen synthesis

• PDGF– Stimulates T1 collagen synth by osteoblast– Stimulates osteoclast resorption

• FGF– Stimulates fibroblast proliferation– Stimulates angiogenesis

• VEGF– Stimulates angiogenesis

Regulation of fracture healing

• IGF– Stimulates bone collagen & matrix synthesis– Inhibits bone collagen degradation

• BMP– Osteoinductive– Stimulates diff of osteoprogenitors to osteoblasts

• Cytokines– IL-1,6 stimulate bone resorption– Chemotaxis and regulation of inflammatory cells

Regulation of fracture healing

• Systemic factors– Growth hormone – acts via IGF– Thyroid hormones – increase bone resorption– Oestrogen – minimises bone resorption

Factors influencing bone healing• Local– Type of bone– # pattern– # site – Soft tissue devitalisation– Soft tissue interposition– Blood supply– Infection– Irradiation

Factors influencing bone healing

• Systemic – Malnutrition– DM– Drugs – NSAIDs, steroids, cytotoxics– Tobacco use– Thyroid disorders– Vitamin deficiency– CNS trauma– HIV

Assessment of fracture healing

• Clinical

• Radiological

Complications • Malunion• Delayed union• Non-union• Infection• Post-traumatic arthritis• Growth abnormalities

Current trends• rBMP– Delivered locally at 10-1000x natural expression– Enhance # healing– Decrease infection in GA IIIa & b #s– Useful in recalcitrant non-unions

• Pulsed electromagnetic field (PEMF)– Used in treatment of nonunions

• Low-intensity pulsed ultrasound (LIPUS)– Increases gene expression, enhances blood flow,

enhances remodelling– Reverses anti-angiogenic effect of nicotine

Conclusion

• Despite major advancement in understanding of bone healing, problems/complications still continue to arise.

• More research is needed in this all-important area if these problems are to be satisfactorily prevented or overcome

Thank you

References

• Apley’s system of orthopaedics and fractures, 9th Ed, pp689 – 692

• http://www.slideshare.net/hardikpawar1/fracture-healing

• http://www.orthobullets.com/basic-science/9009/fracture-healing

• http://www.hughston.com/hha/a.fracture.htm