- Operation developed by Sir John Charnley in 1960s
- More than 50,000 hip replacements are performed each year in United
Kingdom
- Over one million hips have been replaced worldwide
- Over 100 different types of prosthesis have been used
- The 'gold standard' is the Charnley cemented prosthesis
Principle components
Acetabular component
- Usually made of high density polyethylene
- Biocompatible, low coefficient of friction, low rate of wear
- Ceramic acetabular component have improved surface properties
- Are expensive and have tendency to brittle failure
- Metal cups are obsolete due to high friction, loosening and wear
Femoral component
- Usually made of stainless steel, titanium or cobalt chrome alloy
- Resistant to corrosion with high endurance
- Improved longevity seen with small femoral head
Polymethylmethacrylate cement
- Acts as a filling agent without adhesive properties
- Macrolocking occurs with cement in drilled holes
- Microlocking occurs with cement in interstices of cancellous bone
- Produces an exothermic reaction during preparation
- Addition of barium weakens the cement
- Antibiotic impregnation may increase resistance to infection
- Recently uncemented prostheses have been developed
- Require more exacting insertion technique
- Anchored by interference fit achieved by porous surface or
hydroxyapatite coating
- Uncemented prostheses have a tendency early failure
Indications
- Osteoarthritis
- Rheumatoid arthritis
- Still's disease
- Ankylosing spondylitis
- Congenital dysplastic or dislocated hips
- Paget's disease
- Trauma or avascular necrosis
- Septic arthritis
Contraindications
- Uncontrolled medical problems
- Skeletal immaturity
- Active infection
- Neuropathic joint
- Progressive neurological disease
- Muscle weakness
Aims of surgery
- Patients should have significant pain, functional disturbance and
failed conservative therapy
- The principle aims of surgery are:
- To reduce joint pain
- Improve joint function
Operative technique
- Avoid operation in patients with a septic focus
- Thorough skin preparation with sterile adhesive plastic drapes
- Operating team should wear two pairs of gloves
- Body exhaust suites may be worn
- Laminar air flow should be provided in operative field
- Antibiotic prophylaxis should be given
Specific complications
- Neurovascular injuries
- Leg length discrepancy
- Dislocation
- Infection
- Aseptic loosening
- Implant wear and failure
- Heterotopic ossification
- Femoral fractures
- Trochanteric non-union
- Abductor mechanism weakness
Outcome
- Outcome is affected by many factors including
- Type of implant used
- Underlying diagnosis
- Sex of patient
- Cement type
- Cementing technique
- Surgical approach
Joint resurfacing
- Outcome of joint replacement surgery in less predictable in
- Younger patients
- Those with active life style
- Metal on metal hip resurfacing developed for use in younger patients
- Head of femur preserved which is developed into chamfered cylinder
- Metal head is cemented in place
- Metal cup is placed in acetabulum
- Compared to THR, has lower risk of complications
- Lower risk of dislocation
- Less bone loss
- Lower risk of component loosing
- Short-term results are very encouraging
- Long-term outcome unclear
Bibliography
Clarke I C, Donaldson T, Bowsher J G et al.
Current concepts of metal-on-metal hip resurfacing. Orth Clin
North Am 2005; 36: 143-162.
Grigoris P, Roberts P, Pabousis K et al. The
evolution of hip resurfacing arthroplasty. Orth Clin North Am
2005; 36: 125-134.
Latham J, Treacy R B C, Shetty V D, Villar R N.
To resurface or replace the hip in the under 65-year old. Ann R
Coll Surg Engl 2006; 88: 349-353
Salah K J, Kassim R, Yoon P, Vorlicky L N.
Complications of total hip arthroplasty. Am J Orthop 2002;
31: 485-488.
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