Orthopaedics
Bone and Joint Infections
Bone and joint infections for MBBS and NEET-PG: acute and chronic osteomyelitis, sequestrum and involucrum, septic arthritis and spinal tuberculosis, mapped to NMC codes OR3.1 to OR4.1.
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Bone and Joint Infections
Bone and joint infections for MBBS and NEET-PG: acute and chronic osteomyelitis, sequestrum and involucrum, septic arthritis and spinal tuberculosis, mapped to NMC codes OR3.1 to OR4.1.
This chapter covers infections of bone and joints. It works through acute and chronic osteomyelitis and the terms that describe dead and reactive bone, the emergency of septic arthritis, and skeletal tuberculosis with its predilection for the spine, all of which reward early recognition and prompt treatment.
High-yield: Bone and Joint Infections
- Acute osteomyelitis in children commonly affects the metaphysis of long bones because of its sluggish blood flow.
- Staphylococcus aureus is the commonest causative organism of both acute osteomyelitis and septic arthritis.
- Early x-rays in acute osteomyelitis are often normal, and MRI is the most sensitive early investigation.
- A sequestrum is a piece of dead bone, and an involucrum is the new bone that forms around it in chronic osteomyelitis.
- A Brodie abscess is a walled off subacute osteomyelitis that appears as a lytic lesion with a sclerotic rim.
- Septic arthritis is an orthopaedic emergency because pus rapidly destroys articular cartilage.
- The hip and knee are the joints most often affected by septic arthritis.
- Septic arthritis is confirmed by urgent joint aspiration for cell count, Gram stain and culture before antibiotics where possible.
- Treatment of septic arthritis is urgent joint washout with drainage plus systemic antibiotics.
- Skeletal tuberculosis most often involves the spine, where it is called Pott disease.
- Pott disease typically spares the disc early and can lead to a gibbus deformity and a cold abscess that tracks along fascial planes.
- Tuberculosis of the spine can cause paraplegia, known as Pott paraplegia, from cord compression.
- A cold abscess in spinal tuberculosis lacks the classic signs of acute inflammation because it is a chronic caseating process.
- In neonates and infants, septic arthritis of the hip can rapidly destroy the joint and cause permanent deformity if not treated urgently.
Infection essentials
- **Acute osteomyelitis:** Metaphysis of long bones in children, usually Staphylococcus aureus. Early x-ray often normal, MRI most sensitive.
- **Chronic osteomyelitis:** Sequestrum (dead bone), involucrum (reactive new bone), Brodie abscess.
- **Septic arthritis:** Emergency. Aspirate to confirm, then urgent washout and antibiotics.
- **Spinal tuberculosis:** Pott disease: gibbus, cold abscess, risk of Pott paraplegia.
NMC competencies in this chapter
- **OR3.1:** Acute osteomyelitis: aetiology, features and management
- **OR3.2:** Chronic osteomyelitis: sequestrum, involucrum and Brodie abscess
- **OR3.3:** Septic arthritis: diagnosis and emergency management
- **OR4.1:** Skeletal tuberculosis including Pott disease of the spine
Frequently Asked Questions
Why does acute osteomyelitis start in the metaphysis?
The metaphysis of a growing bone has slow, looping blood flow that lets bacteria settle and multiply, so it is the classic starting point in children.
What are a sequestrum and an involucrum?
A sequestrum is a fragment of dead bone in chronic osteomyelitis, and an involucrum is the layer of new living bone the body forms around it.
Why is septic arthritis an emergency?
Pus in a joint contains enzymes that rapidly digest articular cartilage, so a delay of even a day or two can cause permanent joint destruction, which is why urgent washout is needed.
What is Pott disease?
It is tuberculosis of the spine. It can cause a sharp angular deformity called a gibbus, a cold abscess that tracks along tissue planes, and cord compression leading to Pott paraplegia.
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