# Bone Grafting in Orthopaedics > Bone grafting for NEET-PG Orthopaedics: osteogenesis, osteoinduction, osteoconduction, autograft versus allograft, BMP and the Masquelet technique. - Canonical URL: https://prepelephant.com/topics/neet-pg/orthopaedics/bone-grafting-orthopaedics - Exam / course: NEET-PG · Subject: Orthopaedics - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Bone Grafting in Orthopaedics", PrepElephant, https://prepelephant.com/topics/neet-pg/orthopaedics/bone-grafting-orthopaedics ## Direct answer Every nonunion tray and every fusion case asks the same three-part question: does the graft bring living cells, growth signals, or only a scaffold? Osteogenesis means transplanted osteogenic cells (fresh cancellous autograft), osteoinduction means factors that recruit host cells down bone-forming lines (BMPs, demineralised bone matrix), and osteoconduction means a passive scaffold for ingrowth (cancellous matrix, ceramics). Non-vascularised cancellous iliac crest autograft remains the gold standard because it supplies all three properties; allografts and synthetics trade biology for availability and volume. The graft, however, is only the third leg of the stool — stability and vascularity do the other two-thirds of the work. ## What you must remember - **The three properties (the exam's frame):** osteogenesis — living osteoblasts and progenitors, unique to fresh autograft and marrow; osteoinduction — BMP-2, BMP-7 and demineralised bone matrix recruiting mesenchymal cells; osteoconduction — passive scaffolds such as cancellous chips, hydroxyapatite and tricalcium phosphate. - **Autograft menu:** cancellous iliac crest — gold standard, all three properties, fastest incorporation; non-vascularised cortical graft (fibula strut) gives structure but incorporates slowly by creeping substitution; vascularised free fibula for large or hostile defects; reamer-irrigator-aspirator (RIA) harvests large volumes from the femur with less site morbidity. - **Iliac crest donor morbidity:** pain, superior cluneal nerve or lateral femoral cutaneous nerve injury, haematoma, hernia — the reason local bone from decompression and marrow aspirate are popular alternatives. - **Allograft forms:** fresh-frozen (structural strength, osteoconductive, mostly dead cells), freeze-dried (conduction only, weaker), massive structural allografts (complications: nonunion, fracture, infection); no viable cells means incorporation depends entirely on host ingrowth. - **Synthetics:** calcium phosphate ceramics resemble bone mineral and resorb slowly; calcium sulphate resorbs fast and carries antibiotics; none gives structural support alone — they supplement fixation, never replace it. - **BMP reality:** rhBMP-2 has trial support in selected tibial nonunions and spinal fusions, but cost keeps it rare in India; anterior cervical swelling reports limit enthusiasm. - **Masquelet technique (modern viva favourite):** stage 1 — radical debridement and a cement spacer that induces a vascularised "membrane"; stage 2 after six to eight weeks — remove the cement and fill the induced membrane with cancellous graft; the membrane secretes growth factors and blocks fibrous ingrowth. Cement is cheap, which is why the technique flourishes in India. - **By problem:** atrophic nonunion — decortication plus cancellous autograft; contained defects — chips; segmental defects — Masquelet, Ilizarov transport or vascularised graft; infected sites — graft only after infection control. ## Matching graft to defect Three cases fix the logic. First, an atrophic tibial nonunion after nailing: a reamed exchange nail plus decortication and iliac crest chips, because the biology was missing and the graft that carries all three properties is the one to graft with. Second, a 6 cm post-traumatic tibial defect after infected fixation: a Masquelet — debride, cement, wait for the membrane, then graft through it — because a membrane-wrapped autograft outperforms a bare graft in a hostile bed, and the alternative, bone transport, needs months in a frame the patient may not tolerate. Third, a two-level posterior lumbar fusion: local bone from the laminectomy, mixed with a calcium phosphate extender, spares the crest without measurable loss of union in most hands — donor-site morbidity is a price, not a principle. Notice that in all three, fixation and vascularity were settled before graft material was chosen; a graft poured into an unstable or avascular bed is an expensive dressing. ## Conduction is not induction The MCQ "which property does a hydroxyapatite block have?" wants osteoconduction only — no cells, no growth factors — and the follow-up "which graft alone carries osteogenesis?" wants fresh cancellous autograft or marrow. The deeper trap is assuming graft substitutes heal fractures: they scaffold nothing in an unstable bed, and examiners close the loop by asking what completes the triad — fixation and blood supply. Allograft incorporation deserves its own sentence in answers: creeping substitution, host osteoclasts tunnelling into dead matrix, means massive structural grafts stay weak for years — the reason a vascularised graft, despite its donor-site cost, wins for large defects where strength is needed early. ## Frequently asked questions ### What are the three biological properties of a bone graft? Osteogenesis (living bone cells), osteoinduction (growth factors recruiting host cells) and osteoconduction (a scaffold for ingrowth). ### Why is cancellous iliac crest autograft the gold standard? It uniquely provides all three properties — cells, inducive factors and scaffold — and incorporates faster than any substitute. ### What is creeping substitution? The process by which host osteoclasts and osteoblasts slowly replace dead graft matrix with living bone — how cortical and structural allografts incorporate. ### Describe the two stages of the Masquelet technique. Stage 1: debridement plus cement spacer that induces a vascularised membrane; stage 2, six to eight weeks later: remove the cement and pack cancellous autograft inside the membrane. ### Why are calcium sulphate beads used in infected bone defects? They resorb rapidly, can be antibiotic-loaded, and leave space for new bone while delivering high local antibiotic concentrations.