Competing risks survival analysis applied to data from the Australian Orthopaedic Association National Joint Replacement Registry

Abstract

Background and purposeThe Kaplan-Meier (KM) method is often used in the analysis of arthroplasty registry data to estimate the probability of revision after a primary procedure. In the presence of a competing risk such as death, KM is known to overestimate the probability of revision. We investigated the degree to which the risk of revision is overestimated in registry data.Patients and methodsWe compared KM estimates of risk of revision with the cumulative incidence function (CIF), which takes account of death as a competing risk. We considered revision by (1) prosthesis type in subjects aged 75–84 years with fractured neck of femur (FNOF), (2) cement use in monoblock prostheses for FNOF, and (3) age group in patients undergoing total hip arthroplasty (THA) for osteoarthritis (OA).ResultsIn 5,802 subjects aged 75–84 years with a monoblock prosthesis for FNOF, the estimated risk of revision at 5 years was 6.3% by KM and 4.3% by CIF, a relative difference (RD) of 46%. In 9,821 subjects of all ages receiving an Austin Moore (non-cemented) prosthesis for FNOF, the RD at 5 years was 52% and for 3,116 subjects with a Thompson (cemented) prosthesis, the RD was 79%. In 44,365 subjects with a THA for OA who were less than 70 years old, the RD was just 1.4%; for 47,430 subjects > 70 years of age, the RD was 4.6% at 5 years.InterpretationThe Kaplan-Meier method substantially overestimated the risk of revision compared to estimates using competing risk methods when the risk of death was high. The bias increased with time as the incidence of the competing risk of death increased. Registries should adopt methods of analysis appropriate to the nature of their data.

Kaplan-Meier Survival Analysis Overestimates the Risk of Revision Arthroplasty: A Meta-analysis

“…Thus, the use of summary data is a limitation of our study. As a result of a lack of individual patient data, we were unable to examine factors that may have impacted the magnitude RR ¼ Cumulative IncidenceKaplanÀMeier Cumulative IncidenceCompetingÀrisks : * n = 6 studies, 7 strata; Gillam et al [17] estimated the cumulative incidence of revision after THA for three nonmutually exclusive subsets of data; the subset with the largest number of EI included two mutually exclusive strata (patients with osteoarthritis aged \ 70 years, and those aged C 70 years); the subset with the highest rate of CRs included two mutually exclusive strata (cementless Austin Moore prostheses, cemented Thompson prostheses).…”

“…Seven cohort studies compared the Kaplan-Meier and competing-risks methods when estimating the time to revision after joint arthroplasty and were included in our systematic review (j statistic = 1) [6,7,16,17,24,38,41], of which six included enough data to be included in our meta-analysis [6,7,16,17,24,41] (Fig. 1).…”

“…Publication years ranged from 2001 to 2012 (Table 1). Five studies assessed time to revision after partial or total hip arthroplasty (THA) [6,16,17,38,41]; one assessed time to revision after acetabular revision [24] and one assessed time to revision after total knee arthroplasty (TKA) with a megaprosthesis after bone tumor resection [7]. Death was identified as a competing risk in all studies.…”

“…To ensure only mutually exclusive strata from each study were included, we conducted two separate analyses for strata containing: (1) the largest number of events of interest (ie, revisions); and (2) the highest rate of competing risks relative to events of interest (ie, number of competing risks observed/number of events of interest observed). For example, Gillam et al [17] analyzed three subsets of data. The subset with the largest number of events of interest compared the cumulative incidence of revision for patients receiving THA for osteoarthritis who were younger than 70 years old with patients who were aged 70 years and older.…”

“…2A-B Forest plots of RRs compare the cumulative incidence of revision after hip or knee arthroplasty obtained using the KaplanMeier method versus competing-risks method for seven strata (six studies*) containing (A) the highest ratio of competing events to events of interest; and (B) the largest number of revisions. *Gillam et al [17] estimated the cumulative incidence of revision after THA for three nonmutually exclusive subsets of data. The subset with the largest number of events of interest included two mutually exclusive strata: patients with osteoarthritis aged \ 70 years and patients with osteoarthritis aged C 70 years.…”