Bone healing is a complex process that occurs in stages to restore injured bone. It involves formation of a hematoma, inflammation, proliferation of cells, formation of a callus, consolidation into bone tissue, and remodeling. The process is regulated by growth factors and cytokines locally and hormones systemically. Factors like nutrition, disease states, medication, and lifestyle can influence bone healing. Assessment of healing involves clinical and radiological evaluation, and complications may include delayed or non-union of the bone.

1. ‫السالم‬
‫علیکم‬
Lecture no. 5
BONE HEALING & Repair
Mr. Naeem Bukhari
Lecturer, MLT, UOH

2. Contents
֍Introduction
֍Types of bone healing
֍Stages of bone healing
֍Regulation of bone healing
֍Factors affecting bone healing
֍Assessment
֍Complications
֍Current trends
֍Conclusion

3. Introduction
• Bonehealing refers to complex and sequential
events that occur to restore injured bone to pre-
injury state.
• Boneinjury remains aconstant counterpart to
human existence, we are able to cope with this
due to bone healing. Thesurgeon musttherefore
have adequate understanding of its processes,
influencing factors and complications in order to
achieve optimum outcome.

4. Typesof bone healing
⸙ Healing by callus formation (indirect, secondary)
⸙ Healing by direct union(primary)

5. Stagesof bone healing
• Healing by callus formation
– Haematoma formation
• Occursimmediately
– 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 mesenchymalstem
cells, migration of fibroblasts andosteoclasts
• neovascularization

6. Stagesof bone healing
• Healing by callus formation
– Callus formation
• 2-3wks to 4-8wks
• Osteoclasts mop up deadbone
• Collagen matrix formation
• Osteoid deposition andmineralisation
• Formation of wovenbone
– Consolidation
• Weeksto 2-3mnths
• Lamellar bone formation
• Remaining gapsfilled by lamellar bone

7. Stagesof bone healing
• Healing by callus formation
– Remodelling
• 2mnths to years
• Guided by stress exposure
• Osteoclasts are responsible
• Healing by direct union
– Occursin fractures where ends arecompressed,
with intervening space<500microns
– No callus formation
– Gaphealing – occurs if spaceis200-500microns
– Contact healing – occurs if spaceis<200microns

8. HAEMATOMA INFLAMMATION CALLUS CONSOLIDATION REMODELLING

10. Regulation of fracturehealing
• Local factors
– TGF-B
– PDGF
– FGF
– IGF
– VEGF
– BMP
– Cytokines
• Systemicfactors
– Hormones

11. Regulation of fracturehealing
• TGF-B
– Promotes proliferatn & diff of stem cells
– Stimulates collagen synthesis
• PDGF
– Stimulates T1collagen synth by osteoblast
– Stimulates osteoclast resorption
• FGF
– Stimulates fibroblast proliferation
– Stimulates angiogenesis
• VEGF
– Stimulates angiogenesis

12. Regulation of fracturehealing
• IGF
– Stimulates bone collagen & matrixsynthesis
– Inhibits bone collagendegradation
• BMP
– Osteoinductive
– Stimulates diff of osteoprogenitors toosteoblasts
• Cytokines
– IL-1,6 stimulate bone resorption
– Chemotaxis and regulation of inflammatorycells

13. Regulation of fracturehealing
• Systemicfactors
– Growth hormone – acts viaIGF
– Thyroid hormones – increase bone resorption
– Oestrogen – minimises bone resorption

14. Factors influencing bone healing
• Local
– Typeof bone
– # pattern
– # site
– Soft tissuedevitalisation
– Soft tissue interposition
– Blood supply
– Infection
– Irradiation

15. Factors influencing bone healing
• Systemic
– Malnutrition
– DM
– Drugs– NSAIDs,steroids, cytotoxics
– Tobacco use
– Thyroid disorders
– Vitamin deficiency
– CNStrauma
– HIV

16. Assessmentof fracture healing
• Clinical
• Radiological

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

18. Current trends
• rBMP
– Delivered locally at 10-1000x naturalexpression
– Enhance# healing
– Decreaseinfection in GAIIIa & b#s
– Useful in recalcitrantnon-unions
• Pulsedelectromagnetic field (PEMF)
– Usedin treatment of nonunions
• Low-intensity pulsed ultrasound (LIPUS)
– Increasesgene expression, enhances blood flow,
enhances remodelling
– Reversesanti-angiogenic effect of nicotine

19. 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