Musculoskeletal Pathology: Fracture Healing

Introduction to Musculoskeletal Pathology

• Lecture 15 covers musculoskeletal pathology, presented by Dr. Damian McManus.
• Contact information: [email protected].

Fracture Healing Phases

• Four phases exist in fracture healing.
• A fracture callus is a connective tissue mass with hemorrhagic, bony, and cartilaginous elements.
• The callus attempts to bridge the gap in a broken bone.

Initial Phase (Week 1)

• Blood flows from damaged blood vessels immediately after a fracture.
• A hematoma, which is a hemorrhagic swelling, forms from the leaked blood.
• Osteoporosis may be visible on the bone in the left hand side of the slide.

Soft (Provisional) Callus (Week 2)

• Granulation tissue proliferates with new small blood vessels.
• An immature cartilaginous matrix is produced by chondrocytes.
• Immature new bone is produced by osteoblasts.

Bony Callus (Weeks 3 and 4)

• Osteoblasts form new bone.
• Endochondral ossification is the process of cartilage transforming into bone.

Remodelling

• The callus undergoes remodeling and refining over several months.

Arthritis

• Arthritis is defined as pain and inflammation of a joint.
• Osteoarthritis is the most prevalent type of arthritis.
• Pathogenesis includes older age, possible family history, being overweight, or previous injury.
• These factors lead to degeneration, thinning, and fracture of articular cartilage.
• Articular cartilage allows for lubrication, weight distribution, and shock absorption during joint movement.

Osteoarthritis (OA)

• It's described as "wear and tear" arthritis.
• Joint injury or overuse can damage a joint, contributing to the risk of OA.
• The risk of developing OA increases with age.
• Women are more prone to OA than men especially after age 50.
• This condition is characterized by pain in weight-bearing joints that worsens with use and improves with rest.
• X-rays can reveal joint space narrowing and sclerosis.
• Extra weight puts more stress on joints, and obesity has metabolic effects.
• People with family members with OA have a higher chance of developing OA.
• Individuals with hand OA are more likely to develop knee OA.
• Some Asian populations have a lower risk of developing OA.
• Cardinal signs of osteoarthritis are asymmetric joint space narrowing, osteophytes, subchondral sclerosis, and subchondral cysts.
• Heberden's nodes are bony swellings of the distal interphalangeal finger joints
• Bouchard's nodes are similar swellings affecting the proximal interphalangeal finger joints.
• There is the considerable loss of cartilage, the generation of wear particles, and thickening of synovium and capsule disturbances in the subchondral bone

Rheumatoid Arthritis (RA)

• Autoimmune, chronic inflammatory condition primarily affecting the joints, but also potentially involving organs. Common organs are eyes, lungs, heart, blood vessels, and skin.
• Chronic autoimmune synovitis is involved in rheumatoid arthritis.
• Morning stiffness lasting > 30 minutes as well as the symmetric joint involvement and systemic symptoms.
• Rheumatoid factor is an IgM auto-antibody against the Immunoglobulin IgG.
• Anti-cyclic citrullinated peptide (anti-CCP) is another key marker.
• Atlanto-axial subluxation (can result in sudden death if improperly manipulated).
• Rheumatoid nodules are large necrotizing granulomas under the skin.
• Factors contributing to RA include genetic and non-genetic risks, post-translational modifications, and loss of immunotolerance at mucosal sites.
• Extra-articular manifestations include: systemic inflammatory response, skin issues (nodules, ulcers), anemia, eye inflammation, lung or heart inflammation.

Gout

• It involves inflammation of joints and surrounding tissue.
• This caused by deposits of urate crystals.
• Uric acid, derived from RNA, DNA, and purines, is typically excreted by the kidneys and gastrointestinal tract.
• Elevated uric acid levels result from consuming purine-rich foods (liver, anchovies, sardines), kidney disease, diuretics, or alcohol.
• Gouty tophi are nodular masses of monosodium urate crystals in joints, ligaments, tendons, bursae, earlobes, and skin.
• These crystals surrounded by an inflammatory response.
• It is best visualized in alcohol fixed tissues since monosodium urate crystals dissolve in formalin.

Benign Bone Tumours

• Osteoma: a benign surface bone-forming tumor.
• Enchondroma: a benign cartilage-forming tumor inside the medullary cavity of bone.
• Osteochondroma (exostosis): a benign surface bone-forming tumor with a cartilaginous cap.

Malignant Bone Tumours

• Around 500 new bone sarcomas are diagnosed each year in the UK.
• More common in children, teenagers, and young people.
• Pain and loss of function of the affected limb are the main presenting symptoms.
• X-rays might show abnormalities.
• Osteosarcoma: cancerous cells produce immature osteoid, most common site is distal femur , mean age at diagnosis is 15.
• Chondrosarcoma: cancerous cells display cartilaginous differentiation, with a mean age at diagnosis of 50 years.
• Metastatic carcinoma is more common than primary bone tumours.
• Metastatic prostate cancer can be imaged with Bone Scan, MRI, PET, and CT.