The shell can be retained in cases involving femoral neck fracture, femoral loosening or impingement.
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March 2010
Causes of failure
"The cause of failure must be carefully assessed prior to the
conversion surgery in order to ensure an optimal THR outcome," Su said.
He noted that femoral neck fracture is the primary cause of short-term
failure in resurfacing procedures. He theorized that the rate of these
fractures could be reduced with improved surgical techniques, careful
patient selection and preoperative evaluation of bone quality.
Inadequate
acetabular fixation or the so-called "slipped cup" is another cause
of early failure, which may also be related to surgical technique.
"The greatest cause of a mid-term failure is femoral component
loosening and osteonecrosis probably plays a role in this," Su said. "I
think that component malposition is going to play a large role in these
mid-term failures as well." He noted that mid-term investigations of
patients with acetabular component malpositioning revealed painful metal
reactivity requiring revision.
Other causes of failure include
metal hypersensitivity and unexplained pain due to impingement,
undetected stress fractures or pseudotumors...
 X-ray of a hip resurfacing with a vertical cup position, leading to edge-loading. Images: Su EP |
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In planning conversion procedures, surgeons have the option of retaining the shell from the hip resurfacing.
"I think this is acceptable for a well-positioned, well-fixed and undamaged shell," Su said. "It is applicable in situations such as, a femoral neck fracture and in a femoral loosening...
..."A full revision is necessary when there is component malposition of chronic duration because there will be damage to the metal components," Su said. "It is also best when there is a question of metal hypersensitivity."
Reference:
- Su E. Surface replacement conversion: Assuring an optimal THR outcome. Paper #44. Presented at the 26th Annual Current Concepts in Joint Replacement Winter Meeting. Dec. 9-12, 2009. Orlando, Fla.
- Edwin P. Su, MD, can be reached at Hospital for Special Surgery, 535 East 70th Street, New York, New York 10021; 212-606-1128;
