total hip arthroplasty
Arthroplasty
Indications
Patient > 70
Gjertsen et al JBJS Am 2010
- 4335 patients > 70 with displaced subcapital fractures
- minimum 1 year follow up
- 1 year mortality same in each group / 25%
- 22% reoperation in ORIF v 3% in hemiarthroplasty
- more pain / higher dissatisfaction / lower quality life in ORIF group
Options
Hemiarthroplasty
- unipolar monoblock
- unipolar modular
Paget's Disease
Definition
Chronic, non metabolic bone disorder
Characterised by increased bone resorption, bone formation and remodelling
Epidemiology
Rare < 40
1 – 3 % population over 60
M > F
Aetiology
Unknown
Paramyxovirus implicated
- measles
- RSV
- canine distemper virus
Electron Microscope
Uncemented
Goal
Initial press fit
- implant geometry fits the cortical bone in the proximal femur
- good initial mechanical stability
Biological fixation for success
- good press fit
- minimal micromotion
- bony or fibrous tissue ingrowth or ongrowth
Templating
Aim
Reproduce the normal anatomical centre of rotation
Restore femoral offset
Maintain equal leg lengths
Usually template off normal hip
Template
1. LLD
2. Offset
3. Femoral component
4. Acetabular component
5. Osteotomy / femoral seating
Results of Australian Joint Registry
2009 / Revision Rates 8 year
Prosthesis Type All Diagnosis 7 year
Unipolar Monoblock 6.8%
Unipolar Modular 6.8%
Bipolar Hemi 4.2%
Cemented THR 3.8%
Cementless THR 4.4%
Hybrid THR 3.9%
Periprosthetic Fracture
Types
Peri-operative
- incurred during operation
Post operative
- related to osteolysis / trauma / infection
Follow up
1994 National Institutes of Health Consensus on THR
Painful THA
Aetiology
Intrinsic
Infection
Loosening
Thigh pain in uncemented
- micro motion at distal end of stem
- modulus mismatch
Stress fracture / insufficiency fracture
- pubic rami, sacral
Intra-operative fracture
Prosthesis failure
Subtle instability
Extrinsic