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Study: Revision rates as high as 35% for dislocation after revision of unstable THA
Dislocation rates increased each year after revision of unstable THAs.
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DALLAS — A recently presented study showed the risk of re-dislocation after revision THA performed for instability increases annually, and at 15 years postoperatively patients have a 35% chance of re-dislocation.
Suenghwan Jo, MD, PhD, who presented the results at the American Association of Hip and Knee Surgeons Annual Meeting, said several surgical factors can be protective against re-dislocation.
“The 15-year cumulative risk of re-dislocation and re-revision after revisions done for instability is 35% and 45%, respectively. Predictors of failure for dislocation and revision are two or more previous surgeries, a head size less than 36 mm and cup revision,” Jo said. “Use of head size less than 36 mm had the highest re-dislocation rate, while use of (a) 36 mm or larger head and a constrained liner had the lower failure rate when the cup was revised.”
Factors: Head size and liner type
The retrospective study analyzed 539 hips in 528 patients who underwent revision THA at a single center during a 10-year period. The average age of the patients was 66 years and average follow-up was 5.5 years.
Jo and colleagues used the Kaplan-Meier method to determine the risk of re-dislocation and re-revision.
In the first year after surgery there is a 7% risk of re-dislocation after revision of an unstable THA, according to Jo.
“There were 86 postoperative dislocations, of which 53 required subsequent revisions for persistent instability. Of hips that did not dislocate, 69 required a revision. An overall revision rate of 539 hips was just over 22%,” he said. “Cumulative risk of re-dislocation increased with time. There was a risk in the first year of surgery, and then certainly increases to an astonishing rate of 35% after 15 years. The Kaplan-Meier curve shows a cumulative risk of any revision in this cohort, and again the data demonstrate a significantly higher revision rate at 15 years of greater than 45%.”
Strategy matters
Surgery strategy also proved a predictor of re-dislocation or re-revision, according to Jo. Patients with two or more previous revisions and the use of a head size smaller than 36 mm had higher chances of re-dislocation or re-revision. The use of a constrained liner in the primary surgery was another risk factor for a re-revision, but was not a risk factor for re-dislocation, he said.
There were no statically significant differences in revision rates for head size smaller than 36 mm and use of constrained liners.
“There are several limitations to the study, and the most important limitation is the bias in the type of treatment used. More than likely, a patient with more severe forms of instability would have been treated with constrained liners and [this] could account for higher risk of failure. In addition, there is a smaller number of 36 mm or larger heads in this study, as a majority were used after the year 2001,” Jo said. – by Robert Linnehan
- Reference:
- Jo S. Paper #25. Presented at: American Association of Hip and Knee Surgeons Annual Meeting; Nov. 6-9, 2014; Dallas.
- For more information:
- Suenghwan Jo, MD, PhD, can be reached at St. Vincent Private Hospital, East Melbourne, 159 Grey St., East Melbourne, VIC 3002 Australia; email: sueng78@gmail.com.
Disclosure: Jo reports no relevant financial disclosures.