Hip Replacements

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Past (in order to come up with solutions, we need to first understand
the history)
 THA (total hip arthroplasty) one of the most successful
orthopaedic inventions
 In 1925, the American surgeon Marius Smith­Petersen created the first mold 
arthroplasty out of GLASS 
 Despite glass being a biocompatible material, it failed to withstand the great 
forces going through the hip joint and shattered. 
 Marius Smith­Petersen, along with Philip Wiles, later went on to trial the current 
material of choice ­ stainless steel ­ to create the first total hip replacement 
that was fitted to bone with bolts and screws 
 His low friction arthroplasty designed in the early 1960‘s is identical, in principle,
to the prostheses used today. It consisted of three parts
1. a metal femoral stem
2. a polyethylene acetabular component
3. acrylic bone cement 
Present


Metal on Polyethylene (M on PE)
o Most widely used and most followed up
o Cost Effective
o Predictable lifespan
o The main concern for M­on­PE prosthesis is PE debris which creates 
periprosthetic osteolysis by the release of cytokines and proteolytic 
enzymes ultimately leading to implant failure  “aseptic loosing”









 Without infection, no bond formed between prosthetic and bone
o REGENEREX
Metal on Metal (M on M)
o Longer lifespan than M on PE
o Larger femoral head lower # of dislocations
o Metallosis: cobalt and chromium ion blood levels tending to be 3­5 times 
higher than those patients with M­on­PE prostheses
 Potential carcinogenic risk from these metals but no evidence 
supports that claim YET
o OPTIMOM
Ceramic on Ceramic
o hydrophilic prostheses create improved lubrication, therefore low friction 
and low debris particles
o Expensive
o Requires excellent surgeon insertion technique, otherwise
it increases risk of dislocation or devastating wear and tear
o Increase risk of fractures
o Can produce noise
o STRYKER
Hybrid prosthesis
o From a cemented femoral stem and acetabular cup fixed in place with 
cementless techniques. 
o Target group: young, active patients since it prevents
pelvic bone loss
o Poor clinical date for follow up care
Cementless Techniques
o Cementless prosthesis have a specialized coating, hydroxyapatite, that 
allows ingrowth of bone and thus fixation of the prosthesis 
o Cementless techniques allow for easier planning of hip revision surgery, 
particularly in the younger patients, with greater preservation of bone 
tissue

Intraoperative complications
 Nerve damage (0-3%)
 Vascular injury (0.2-0.3%)
 Cement related hypotension (<5%)
Post-operative complications
 Thromboembolic disease= DVT (ranges between 8%  70%)
 Infection (0.4- 1.5%)
 Dislocation (0-2%)
o A posterolateral approach utilizing a posterior capsular
repair can reduce the dislocation rate to less than 1
percent





Osteolysis (long-term issue)
o Osteolysis is a process in which bone is resorbed as a
biologic response to particulate debris.
Aseptic loosening (loss of fixation)
Leg length discrepancy (BIGGEST LAWSUITS AGAINST
SURGEONS)

BEST 3D Printing material
Polyamides
Polyethylene on Ceramic

GOALS
o Cost effective
o Predictable/long lifespan
o Easy follow up care
o Fewer dislocations
o No foreign debris (like PE)
o Comfortable (no noise/low friction/proper
orientation)
Clinical and Medical Risk Assessment
1. Familiarize yourself with the medical conditions that would lead to
the need or desire for the implant described
2. Familiarize yourself with the current standard of care for the
condition
3. Evaluate the medical benefits as compared to the current standard
of care for the implant. How can these benefits be measured?
4. Evaluate the potential risks of the new method as compared to the
current standard of care. How can these risks be mitigated?
5. Is the risk-benefit analysis sufficiently in favor of the new method or
device to convince a practicing doctor to learn and adopt the new
treatment?

***Thursday September 3rd 4-7 pm

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