Abstract
Dysplasia has long been identified as a high-risk group for total hip replacement(THR). The underlying causes include younger age, underlying joint deformity, and greater tissue laxity. A higher failure rate has also been identified for hip resurfacing arthroplasty (HRA) in these patients. Many experts have advised avoiding HRA in these patients, although comparative studies are not available. We do not practice patient selection, because THR has not been proven any more reliable for these patients. Instead, we have taken the approach of studying the causes of failure and finding methods to improve the results of HRA in dysplasia patients. We have identified three primary failure modes for the young women who typically have dysplasia: failure of initial acetabular ingrowth (FAI), adverse wear related failure (AWRF), and early femoral failure (EFF: femoral neck fracture and head collapse). Improvements in technique to address all of these failure modes were in place by 2008: acetabular components with supplemental fixation for severe deformities (trispike), guidelines and intraoperative x-ray techniques to eliminate malpositioned acetabular components resulting in edge-loading, uncemented femoral fixation and a bone management protocol that has eliminated early femoral failure.
Group I includes 142 cases done before 2008 and Group II includes 168 cases with minimum 2-year follow-up done after this date. Two-year failure rates improved from 5% (8/142) to 0.6% (1/168) and 5-year Kaplan-Meier survivorship improved from 93% to 99%.
In Group II we have had only one failure (femoral neck fracture) in 168 dysplasia cases with 2–5 year follow-up. There have been no failures of acetabular ingrowth, no AWRF, no femoral head collapse, no failures of femoral ingrowth, no femoral loosenings, no dislocations and no nerve palsies. All acetabular components placed since 2008 meet our published RAIL (relative acetabular inclination limit) guidelines, which we have shown to be 99% reliable in avoiding high on levels and AWRF.
Both groups were 70% female. With a mean bearing size 48mm (high-risk for HRA). There was also no differences in DEXA scan T score, BMI, ASA score, length of incision (4 inches) HHS, or patients participating in impact sports (UCLA activity score 9&10). In Group II the mean age was 3 years greater (52), the mean operative time was 20 minutes shorter (96 minutes), estimated blood loss was 120 ml less (140ml) and the mean hospital stay was one day shorter (2 days) probably reflective of greater experience in this single surgeon series.
We have demonstrated that with sufficient surgeon experience and properly designed implants, hip resurfacing can be performed with a failure rate that is lower than most reports on THR for this disorder.
