Orthopaedic Deformities: Knee Types

Study Notes

Genu Varum (Bowleg)
- In infants, the most common cause is developmental and physiological
- The deformity corrects itself with growth, usually by age 4
- In children (aged 1.5-2 years), Rickets is the most common cause
- Rickets is associated with systemic signs, symptoms, and laboratory findings
- Rickets treatment is directed towards correcting the cause, typically vitamin D deficiency
- Advanced cases of Rickets may require osteoclasis or osteotomy
- In adults, Osteoarthritis, mal-united fracture, ligamentous injury, and Paget's disease are the main causes
- Treatment for adult bowlegs is surgical correction of the deformity
Genu Valgum (Knock Knees)
- Valgus knee up to age 4 is usually developmental or physiological
- Most cases self-correct by 6-8 years
- Progressive valgus knee after age 4 requires a supracondylar osteotomy of the femur

Normal neck-shaft angle of the proximal femur is 160° at birth, decreasing to 125° in adulthood
Coxa Vara: Angle less than 110°
Coxa Valga: Angle more than 130°
Both lead to gait disability and secondary spinal pain and deformity
Treatment is by corrective subtrochanteric osteotomy

Normal carrying angle is 10-15 degrees of valgus, allowing for objects to be carried alongside the trunk while walking
Cubitus Valgus: Angle above 15 degrees
Cubitus Varus: Angle below 10 degrees
These deformities are corrected surgically through a wedge osteotomy at the lower humerus

Bone Cells:
- Osteoblasts : bone forming cells
- Osteoclasts : bone resorbing cells
Bone Matrix: Osteoid, formed of collagen with calcium salts deposited
Causes of Bone Softening Diseases:
- Defective osteoid formation, e.g., osteogenesis imperfecta
- Defective mineralization of osteoid, e.g., rickets
- Increased bone resorption by osteoclasts, e.g., hyperparathyroidism
- Decreased bone formation by osteoblasts, e.g., osteoporosis

Generalized mesenchymal disorder characterized by:
- Defective osteoid production leading to fragile bone and multiple fractures
- Defective collagen production resulting in joint hyperlaxity and blue sclera
Types:
- Congenital: Still-born or born with multiple fractures
- Infantile: Manifestations early in infancy with multiple fractures
- Tarda: Manifestations develop in late childhood
No specific treatment for the condition
Orthopedic management:
- Preventing fractures and deformities with supportive devices
- Treating current fractures
- Correcting deformities through surgery

Disease of growing bone due to inadequate calcification of bone matrix
Causes:
- Infantile Rickets: Deficient vitamin D intake and lack of sunlight exposure
- Coeliac Rickets: Deficient absorption of fat and vitamin D due to gluten intolerance
- Renal Rickets: Disturbed calcium-phosphorus metabolism due to renal dysfunction
Clinical Picture:
- Bony deformities causing bow legs (genu varum) or knock knees (genu valgum)
- Characteristic signs of infantile rickets include:
  - Boxy-bossy skull
  - Rickety rosary
  - Pigeon chest
  - Harrison sulcus
  - Broad metaphysis
  - Marfan sign
10 Important clinical features in Rickets:
- Delayed closure of fontanelles
- Frontal bossing
- Dental hypoplasia
- Pectus carinatum
- Swelling in wrist and ankle joints
- Wide sutures
- Craniotabes
- Rachitic rosary
- Harrison's sulcus
- Bowing of legs
X-Ray:
- Bone rarefaction (decreased density)
- Broadened and cupped metaphyses with brush border
- Healing shows a line of calcified bone replacing the frayed brush border
Treatment:
- Infantile Rickets: Diet rich in calcium, phosphorus, and vitamin D, sunlight exposure, vitamin D and calcium administration.
- Renal Rickets: High doses of vitamin D (one alpha) and calcium
- Severe deformities may require osteotomy

Primary hyperparathyroidism: Increased parathyroid hormone secretion due to hyperplasia or tumour
Causes increased bone resorption by osteoclasts, leading to:
- Hypercalcemia
- Recurrent renal calculi
- Bone resorption causes cystic changes, bone deformities, and pathological fractures
Treatment: Surgical excision of parathyroid adenoma

Bone mass loss: Reduced bone formation by osteoblasts due to aging and menopause
Common sites affected:
- Vertebral column: Weakens vertebrae, causing collapse, back pain, kyphosis, and wedged or biconcave vertebrae on X-ray
- Proximal femur
- Proximal humerus
- Distal radius (prone to fracture)
Diagnosis: Bone Densitometry (DEXA)
Treatment:
- Diet: Calcium, vitamin D, and proteins
- Exercise: Daily exercise and sunlight exposure
- Medications:
  - Calcium and vitamin D
  - Calcitonin (increases osteoblastic activity)
  - Bisphosphonates (inhibit osteoclastic activity)
  - Hormonal Replacement Therapy (HRT) in some cases