Osteoarticular disease Flashcards
What’s an osteon?
The functional unit of compact bone.
Each osteon has concentric layers or lamellae.
What are the different types of bone?
Cortex - compact bone consisting of a parallel arrangement of osteons.
Cancellous- composed of sponge like trabecular bone.
What are the different types of bone formation?
- Intramembranous ossification – flat bones of the skull but also the mandible, maxilla, and clavicles.
- Endochondral ossification- Occurs in long bones and most of the rest of the bones in the body.
What’s Ostero-articular pathology?
Group of diseases that affect the bones and joints. Can be split into four sections:
- Developmental disorders: achondroplasia, Osteogenesis imperfecta, Osteopetrosis
- Generalised disorders: Osteoporosis, Osteomalacia, Skeletal effects of hyperparathyroidism, Paget’s disease
- Neoplastic disease: Bone forming tumours, Cartilage tumours
- Joint disease: Osteoarthrosis
What’s achondroplasia?
A developmental disorder.
The characteristic features are:
Short limbs, Trident hands, Normal trunk length, Contracted base of skull.
• The condition is inherited as an autosomal dominant trait but it is more commonly sporadic (75% of cases) - the result of a new mutation.
• The condition occurs at a rate of about 1/30,000 live births.
• This is the result of restriction of growth in the length of the long bones of the limbs.
What is osteogenesis imperfecta?
• Group of developmental disorders in which there is abnormality in the synthesis of Type 1 collagen which constitutes
about 90% of the organic matrix of bone. • Most cases are caused by mutations in the
COL1A1 and COL1A2 genes.
• There are about 8 types of OI, type 1 is the most common which is mild. This can be autosomal dominant or sporadic.
In the most severely affected individuals the condition is lethal perinatally while in those who are mildly affected there may be little clinical manifestation apart from early onset osteoporosis.
In those who are severely affected and survive into adulthood there is progresive deformity and extreme fragility of the skeleton.
The sclera of the eyes may also appear blue because their thinness allows the pigment layer to show through.
Dentinogenesis Imperfecta: Irregular dentine formation that produces the blue/gray hue. Present in types III and IV OI.
What is osteopetrosis?
Rare inherited developmental disorder. Defect in osteoclastic activity.
The bone turn-over becomes disrupted and this produce dense “stone” bone leading to disappearance of the marrow cavity.
What is osteoporosis?
Osteoporosis is a very common generalised bone disorder. It is the loss of bone mass.
Causes:
1. Disuse: Prolonged bed rest, paralysis
2. Diet: Deficiency of calcium, protein, Vitamin C
3. Drugs: Heparin, steroids
4. Endocrine: Adrenal, testicular or ovarian failure.
5. Post-menopause (this is the most common cause)
The loss of bone mass makes the bone weaker and fractures are common especially: 1. Vertebral crush fractures 2. Fractured neck of femur 3. Fracture of forearm bones.
Normal cancellous bone has thick trabeculae and many connections between trabeculae but in osteoporosis the trabeculae are narrow and widely separated from each other.
What are osteomalacia and rickets?
Both are caused by inadequate mineralisation of existing organic bone matrix.
The main cause is the lack of vitamin D which is a crucial mediator in the mineralisation of bone.
Rickets occurs in the growing skeleton and its major manifestation is mechanical weakness in the long bones of the lower limb which bend and become deformed under the influence of body weight.
Causes:
Intrinsic Vitamin D disturbance, kidney disease, inborn errors of metabolism.
What are the skeletal effects of hyperparathyroidism?
Increases bone resorption, allowing flow of calcium from bone to blood. Currently most patients with hyperparathyroidism reach a diagnosis through the detection of raised plasma calcium.
What is Paget’s disease?
A generalised bone disorder where there’s excessive breakdown and formation of bone, followed by disorganized bone remodeling. It’s a chronic condition. Typically is localized, affecting just one or a few bones. Large portion are asymptomatic. Persons past middle age affected . Increase serum alkaline phosphatase.
Loss of hearing in one or both ears may occur when Paget’s disease affects the skull. Can be seen orally by generalized enlargement of the maxilla and spacing of the teeth.
What’s an osteosarcoma?
A bone forming tumour (a neoplastic disease). • Represent less than 1% of all tumours diagnosed. • In the UK there are around 1000 new cases each year. • About 15% of bone tumours are osteosarcoma. • In 85% of cases patients are under the age of 30. They tend to occur at particular sites in the skeleton with >90% occurring in the metaphyseal part of the bone.
In most cases the tumour is surgically resected following chemotherapy and it is usual to find that most of the tumour is then necrotic.
The tumour is composed of disorganised sheets of malignant osteoblasts, which show pleiomorphism (variation in size and shape).
What is osteoarthritis?
Disorder of synovial joints characterized by cartilage degeneration with secondary changes in the adjacent bone.
This is not a single disease but this is rather common response to a variety of physiologic and metabolic conditions.
Primary arthritis- Unknown aetiology (most common) Generalised or erosive
Secondary arthritis – Occur in joints severely damaged by a previous or existing condition, such as:
Rheumatoid arthritis or gout.
The three main symptoms are:
1- Pain,
2- Morning stiffness and
3- Tendency for the affected joint to gel with immobility
More common in the over 50’s and the obese.
What are the symptoms and causes of TMJ osteoarthritis?
Symptoms: Crepitation, Pain around the ear, Limited movement, Bite shifting.
Causes: Parafunction, Bad occlusion, Trauma, Genetics
What’s the treatment of osteoarthritis?
Exercise, Lifestyle modification, Analgesics (NSAIDS), Intra-articular steroids.
If pain becomes debilitating, joint replacement surgery may be used to improve the quality of life.
