The removal of material, with the generation of wear particles under an applied load and in relative motion
Tribology is the study of wear and lubrication
Adhesion
- bonding of the surfaces when pressed together
- may pull away material from the weaker surface
Abrasion
- asperities on the harder surface cut and plough
Migration of the femoral head past the medial wall of the acetabulum / ilioischial line
Centre edge angle > 40o
Primary
Otto's Disease
- bilateral in one third
- middle aged females
- pain & decreased ROM early
- coxa vara & OA common
- ? causally related to osteomalacia
Decreased tone
- Polio
- Down's syndrome
- spina bifida
Increased tone
- cerbral palsy
- Parkinson's
- CVA
Rare
- case reports only
Acetabular dysplasia not uncommon in this group
Results
THR in dysplastic hips has a higher failure rate
- due to anatomic abnormalities
- due to generally younger age
Restore normal biomechanics and preserve bone stock
Soft tissues
Severe LBP
- most common indication
Ipsilateral knee pain
- less beneficial
Malposition
- especially abduction
Absent abductor mechanism
Flail
Active infection
Insufficient bone stock
LLD
Femur
- removal of femoral head cartilage
- resurfacing with metal
- cemented / uncemented
Acetabulum
- standard technique
Bearing surface
- metal on metal
Relatively young man (40 - 50)
OA
Extraskeletal bone formation in periarticular tissues
- HA crystals within osteoid matrix
Different to calcification
- osteoid matrix laid down
1. Myositis Ossificans
- post traumatic
Top 6 conditions associated with DVT
- stroke
- THR
- multi trauma
- TKR
- hip fracture
- spinal cord injury
Not one of the 12 doctors was an orthopaedic surgeon
Heparin / LMWH / fondaparinux
- confirmed effectiveness