Originally published by 2 Minute Medicine® (view original article). Reused on AccessMedicine with permission.

1. A hospital with “better than expected” outcomes for implant survival in total hip replacement (THR) used the Exeter V40 femoral stem implant on all patients.

2. No difference in implant survival was found between this hospital and other hospitals, when examining only cases with the Exeter V40 femoral stem.

Evidence Rating Level: 2 (Good)

Study rundown: For patients suffering from end-stage osteoarthritis of the hip, a total hip replacement (THR) offers a safe surgical solution that alleviates pain and re-establishes mobility. THR implants usually survive for 25 years, but statistics from the UK show that there is still variation in how long they last. When there is development of an infection, fracture, or other complications with the implant, a THR revision surgery is needed. Unfortunately, these revision surgeries are less successful than the initial operation in terms of ameliorating pain and mobility, are an inconvenience to patients, are costly to the health system, and are more likely to require further revisions. The current study was based out of England and Wales, where one hospital (the exemplar unit) was consistently found to have higher implant survival rates than other hospitals in the region. Furthermore, despite the numerous types of implants available, this particular hospital used solely the Exeter V40 femoral stem for all THR patients. This was a strength in the study since selection bias was minimized by all patients receiving the same implant, regardless of their age, sex, or other health factors. This study compared rates of THR revision for any cause, between the exemplar unit and hundreds of other hospitals, in order to investigate whether the unit’s success may have been due to the implant used or due to factors specific to the hospital, such as surgical skill and demographics of the patients. Ultimately, the study found that after limiting the analysis to only THRs using the Exeter V40 femoral stem, no difference in survival time was found between the exemplar unit and other hospitals. This suggests that the type of implant used was an important contributor to the success of the exemplar unit. A limitation of the study is that it does not demonstrate causality, especially due to uncontrolled factors such as the surgeons performing the THRs.

In-depth [retrospective cohort study]: This study examined 664 761 THRs done at 461 hospitals in England and Wales, from 2003 to 2017: The maximum follow-up time was 13.9 years. Of these surgeries, 6 230 were done by 83 different surgeons at the exemplar unit: The Royal Devon & Exeter NHS Foundation Trust (RD&E). The average age of patients was 69.9 years (SD 10.1) and 61.1% were female. The results showed that the 10-year cumulative estimate for revision surgery was significantly lower at the RD&E, with 1.7 (95% CI 1.3-2.3) compared to 2.9% at other hospitals (95% CI 2.8-3.0, P < 0.001). When examining only cases with the Exeter V40, the revision estimate was not significantly different, at 2.3% (95% CI 2.2-2.4, P = 0.05). Furthermore, after controlling for confounding factors such as age, sex, and American Society of Anesthesiology (ASA) score, and when only comparing cases using the Exeter V40, there was no difference in survival time after 13.9 years (restricted mean survival time was 0.02 years, 95% CI -0.02-0.07, P = 0.33). Overall, this study showed that the implant type was correlated with lower rates of revision surgery and long-term implant survival for THR surgery.

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