01
Understanding the Problem
When bones fail to heal — the three scenarios
The human body is remarkably equipped to repair broken bone. Within hours of a fracture, a cascade of cellular events begins — haematoma formation, inflammation, periosteal activation, and ultimately callus formation. Under normal circumstances, this process completes within 6–12 weeks. But in a significant minority of patients, this cascade stalls — sometimes permanently.
✅
Expected outcome
Normal Healing
6–12 weeks
Haematoma organises into granulation tissue, cartilaginous callus bridges the gap, and bone remodels to restore mechanical integrity. Predictable with adequate blood supply and stability.
⏳
Complication
Delayed Union
3–6+ months
Healing is occurring but significantly slower than expected. Pain and tenderness persist at the fracture site beyond the normal window. Radiological evidence of incomplete callus. Still treatable non-surgically.
⛔
Established failure
Non-Union
6+ months, no progress
Healing has ceased. Fracture gap persists without bridging callus. Two subtypes: hypertrophic (adequate blood supply, insufficient stability) and atrophic (insufficient biological activity). Requires active intervention.
📐
Defining non-union clinically
The FDA defines non-union as a fracture that is at least 9 months old with no visible healing progress for the last 3 months. Clinically, most specialists act earlier — at 4–6 months without radiological progression — to avoid prolonged disability and the biological window for regenerative therapies closing.
02
Root Causes
Why do fractures stop healing?
Failed fracture healing is rarely the result of a single factor. It is almost always a combination of biological, mechanical, and systemic variables. Understanding which factors are present in a given patient is essential for selecting the right intervention — and BMI therapy is most powerful when the underlying biology is understood and corrected alongside the injection.
🩸
Poor Blood Supply
Adequate vascularity is essential for delivering progenitor cells, oxygen, and growth factors. Fractures of the femoral neck, talus, and scaphoid are high-risk due to tenuous blood supply. Smoking dramatically impairs microvascular healing.
⚙️
Mechanical Instability
Excessive movement at the fracture site disrupts callus formation. Inadequate fixation, early weight-bearing, or implant failure can prevent the mechanical environment needed for ossification.
🦠
Infection
Even low-grade subclinical infection at a fracture site creates an inflammatory milieu that inhibits osteoblast activity. Open fractures, post-surgical cases, and immunocompromised patients are at highest risk.
💊
Systemic Factors
Diabetes, vitamin D deficiency, hypothyroidism, renal disease, and chronic NSAID or steroid use all impair bone healing biology. Nutritional status — particularly protein and calcium — is frequently overlooked.
📏
Large Fracture Gap
Gaps exceeding 2–3mm are harder for callus to bridge. Bone loss from comminution, debridement of infected bone, or atrophic non-union all increase the biological challenge and may require augmentation.
🧬
Depleted Stem Cell Pool
Fracture healing depends on mesenchymal stem cells (MSCs) from the periosteum and bone marrow. Age, prior irradiation, and bone marrow disorders reduce MSC availability — a direct target of BMI therapy.
🚬
Smoking — the most modifiable risk factor
Smokers have a 2–3× increased risk of delayed union and non-union. Nicotine causes direct vasoconstriction of periosteal vessels, reduces osteoblast proliferation, and impairs collagen synthesis. Smoking cessation should be a prerequisite for non-surgical fracture healing programmes — and BMI response rates are substantially better in non-smokers.
03
The Treatment
What is Bone Marrow Injection Therapy?
Bone Marrow Injection (BMI) therapy — also termed Bone Marrow Aspirate Concentrate (BMAC) injection — is a minimally invasive, biologics-based procedure that harnesses the patient's own regenerative cells to stimulate fracture healing. It is founded on the observation that non-healing fractures are often biologically inert — lacking the cellular machinery needed to advance healing — and that this can be corrected by delivering a concentrated bolus of osteoprogenitor cells directly to the fracture site.
Bone marrow, aspirated typically from the posterior iliac crest, is rich in mesenchymal stem cells (MSCs), osteoblast precursors, haematopoietic cells, and growth factors including BMP-2, TGF-β, VEGF, and IGF-1. When concentrated and injected under fluoroscopic or ultrasound guidance into the non-union site, this biological payload can restart the stalled healing cascade.
🩸
Step 01
Aspiration
30–60 ml bone marrow drawn from posterior iliac crest under local anaesthetic. Same-day procedure.
🔬
Step 02
Concentration
Aspirate centrifuged to concentrate MSCs, platelets, and growth factors — typically 6–8× baseline concentration.
🎯
Step 03
Guided Injection
BMAC injected percutaneously into the fracture site under fluoroscopic or ultrasound guidance. Precise targeting is critical.
🦴
Step 04
Healing Response
MSCs differentiate into osteoblasts; growth factors stimulate vascular ingrowth and callus formation over 6–12 weeks.
🔬
The biological mechanism
MSCs delivered to the fracture site respond to local cues — hypoxia, inflammatory mediators, mechanical signals — and differentiate into osteoblasts (bone-forming cells). Simultaneously, the VEGF and PDGF content of BMAC stimulates angiogenesis, restoring the vascular supply that atrophic non-unions often lack. BMP-2 and BMP-7, present in the concentrate, directly upregulate osteoblast gene expression and accelerate mineralised callus formation.
BMI therapy doesn't override biology — it re-engages it. We're taking the patient's own healing potential and delivering it precisely where it's needed, at a concentration the body can no longer achieve naturally at that site.
Dr. Sarish Sharma · Orthopaedic & Fracture Specialist
04
Evidence & Outcomes
What does the evidence show?
BMI therapy for non-union has an evidence base stretching back over three decades, with the landmark work of Connolly et al. in the 1990s demonstrating percutaneous BMAC injection as a viable alternative to surgical bone grafting. Since then, multiple prospective studies, systematic reviews, and comparative trials have refined patient selection and outcomes data.
Overall union rate in tibia non-union
80–87%
Prospective data across multiple centres (Hernigou et al., multiple series)
Pain reduction at 3 months
~70%
Patient-reported outcome measures (VAS pain scores)
Success in hypertrophic non-union
90%+
Best results where vascularity is adequate; mechanical factors corrected
Avoidance of open surgery
75–80%
Proportion of patients avoiding planned surgical bone grafting
| Factor |
BMI / BMAC |
Surgical Bone Graft |
Observation only |
| Invasiveness |
Minimally invasive |
Major surgery |
None, but no action |
| Anaesthesia |
Local / sedation |
General / spinal |
Not required |
| Hospital stay |
Day case |
2–5 days |
None |
| Recovery time |
Days |
Weeks–months |
Ongoing disability |
| Infection risk |
Very low |
Moderate |
None additional |
| Biological activity |
High (autologous MSCs) |
High (structural) |
None added |
| Suitable for repeat |
✓ |
✗ (limited sites) |
✗ |
05
Patient Selection
Who is the right candidate for BMI therapy?
BMI therapy is not appropriate for every non-union — and careful patient selection is the most important determinant of outcome. The procedure works best when the biological deficit (insufficient osteoprogenitor cells) is the primary cause of non-healing, rather than gross mechanical instability or active infection, which must be resolved first.
✓
Established delayed union or non-union — fracture present for 3+ months without progression on serial imaging
✓
Hypertrophic or oligotrophic pattern — adequate vascularity confirmed, biological stimulation is the limiting factor
✓
Adequate mechanical environment — existing fixation is stable, or supplemented with cast/brace immobilisation
✓
No active infection at the fracture site — infection must be eradicated before biological therapy is initiated
✓
Patient willing to address modifiable factors — smoking cessation, vitamin D and nutritional optimisation, diabetes control
✓
Seeking to avoid or delay surgery — particularly elderly, high surgical risk, or patients wishing to preserve bone graft donor sites
⚠️
When BMI is not the answer
Atrophic non-unions with large segmental bone loss, fractures with gross mechanical instability (loose or failed implants), active osteomyelitis, and patients with haematological malignancies affecting the bone marrow are poor candidates. In these cases, surgical options — bone grafting, intramedullary nailing revision, or frame-assisted bone transport — should be the primary discussion.
06
The Patient Journey
What to expect — before, during & after
For patients considering BMI therapy, understanding the full journey removes anxiety and ensures appropriate expectations. The procedure is performed as a day case, typically under local anaesthetic with light sedation, and causes minimal disruption to daily life.
📋
Pre-procedure Assessment
Full review of imaging (X-ray + MRI or CT), blood tests including vitamin D, HbA1c, inflammatory markers, and nutritional screen. Smoking cessation mandatory for 6+ weeks. Systemic conditions optimised.
🏥
Procedure Day
Day case. Local anaesthesia to posterior iliac crest. 30–60 ml aspirate obtained, centrifuged on-site (15–20 minutes). Percutaneous injection under imaging guidance. Total procedural time: 45–60 minutes.
🩹
Immediate Recovery
Soreness at aspiration site (2–4 days). Protected weight-bearing as clinically appropriate. Most patients return to sedentary activity within 48–72 hours. Driving typically restricted for 1 week.
📈
Monitoring & Follow-up
Serial X-rays at 6, 12, and 24 weeks. CT scan at 12 weeks if union uncertain. Pain typically begins improving at 4–6 weeks. Radiological union (bridging callus on 3 cortices) expected at 8–16 weeks in responders.
🔄
Can BMI be repeated?
Yes — and this is one of its important advantages over surgical bone grafting. If the initial injection produces a partial response (some callus formation but incomplete union), a second injection can be administered at 12–16 weeks. Evidence suggests repeat injections are safe and additive in effect, with many cases achieving full union after a second procedure that showed partial response after the first.