Knowing the cause of resurfacing failure can ensure successful conversion to THR by Edwin Su, MD
The shell can be retained in cases involving femoral neck fracture, femoral loosening or impingement.
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…
Images: Su EP
…Shell retention or full revision?
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.”