Pathology
Wound Healing
Question 90 of 180
Regarding fracture healing, which of the following statements is INCORRECT:
Answer:
- Haematoma formation due to tearing of medullary blood vessels.
- Migration of neutrophils and macrophages into fracture with organisation of haematoma within about 24 hours.
- Capillaries and fibroblasts proliferate forming fibrovascular granulation tissue.
- Osteoblasts deposit large quantities of osteoid collagen in a haphazard way producing a woven bone pattern.
- About 3 weeks post fracture, callus is well established and undergoes remodelling.
- Osteoclastic resorption and osteoblastic osteoid synthesis removes surplus calcified callus, replacing bulky, woven bone with compact, organised, lamellar cortical bone.
Stages of Fracture Healing
Pathology / Wound Healing
Last Updated: 24th April 2019
Bone fractures heal by granulation tissue formation with fibrous repair, followed by new bone formation in the fibrous granulation tissue.
Stages of Bone Healing
- Haematoma Formation (Day 1)
- Haematoma formation due to tearing of medullary blood vessels.
- Blood clot fills gap and swells and lifts periosteum - stretching or tearing cause severe pain and encourage immobilisation.
- Organisation (Days 1-7)
- Migration of neutrophils and macrophages into fracture with organisation of haematoma within about 24 hours.
- Capillaries and fibroblasts proliferate forming fibrovascular granulation tissue.
- Periosteal cells activated by PDGF, FGF and other factors in the blood clot.
- New osteoprogenitor cells (derived from mesenchymal precursor cells) mature into osteoblasts which migrate into granulation tissue.
- Callus Formation (Weeks 2-3)
- Osteoblasts deposit large quantities of osteoid collagen in a haphazard way producing a woven bone pattern.
- Fracture is bridged on outside by external callus (may contain cartilage) and it is bridged in medullary cavity by internal callus (rarely contains cartilage).
- However, direct ossification may occur between fractured ends if they are closely apposed.
- Remodelling (3 weeks-3 months)
- About 3 weeks post fracture, callus is well established and undergoes remodelling.
- Osteoclastic resorption and osteoblastic osteoid synthesis removes surplus calcified callus, replacing bulky, woven bone with compact, organised, lamellar cortical bone.
- Process takes several months.
- Completion
- Formation of new lamellar trabecular bone is complete.
- The marrow space is repopulated to normal by fat and haemopoietic cells.
- Bone is orientated in a direction determined by stresses to which it is exposed with mobilisation.
- However, even after remodelling, cortical irregularities and minor marrow space fibrosis persist at site of fracture.
Complications of Bone Healing
Bones show a great capacity for healing but certain complications can occur:
- Malunion
- Poor anatomical alignment of fractures results in deformity, angulation or displacement
- Delayed union
- This is common and defined as 25% longer than average time
- Non-union
- If union has not occurred within 1 year; the defect is typically filled with fibrous tissue/fibrosus ankylosis
Causes of Complications
Efficient healing requires optimal conditions. Factors that prevent efficient healing are:
- Poor apposition of fractured bone ends
- Inadequate immobilisation
- Interposition of foreign bodies or soft tissues
- Infection
- Corticosteroid therapy
- Poor general nutritional status
- Poor blood supply
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
