Martin Christopher T, Callaghan John J, Gao Yubo, Pugely Andrew J, Liu Steve S, Warth Lucian C, Goetz Devon D
Department of Orthopaedic Surgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, 01008 JPP, Iowa City, IA, 52242, USA.
Des Moines Orthopaedic Surgeons, West Des Moines, IA, USA.
Clin Orthop Relat Res. 2016 Feb;474(2):402-7. doi: 10.1007/s11999-015-4260-7.
A patient who dies during the followup period of a study about total hip arthroplasty (THA) cannot subsequently undergo a revision. The presence of competing events (such as deaths, in a study on implant durability) violates an assumption of the commonly used Kaplan-Meier (KM) survivorship approach. In that setting, KM-based estimates of revision frequencies will be high relative to alternative approaches that account for competing events such as cumulative incidence methods. However, the degree to which this difference is clinically relevant, and the degree to which it affects different ages of patient cohorts, has been poorly characterized in orthopaedic clinical research.
QUESTIONS/PURPOSES: The purpose of this study was to compare KM with cumulative incidence survivorship estimators to evaluate the degree to which the competing event of death influences the reporting of implant survivorship at long-term followup after THA in patients both younger than and older than 50 years of age.
We retrospectively reviewed 758 cemented THAs from a prospectively maintained single-surgeon registry, who were followed for a minimum of 20 years or until death. Revision rates were compared between those younger than or older than age 50 years using both KM and cumulative incidence methods. Patient survivorship was calculated using KM methods. A total of 21% (23 of 109) of the cohort who were younger than 50 years at the time of THA died during the 20-year followup period compared with 72% (467 of 649) who were older than 50 years at the time of surgery (p < 0.001).
In the cumulative incidence analysis, 19% of the younger than age 50 years cohort underwent a revision for aseptic causes within 20 years as compared with 5% in the older than age 50 years cohort (p < 0.001). The KM method overestimated the risk of revision (23% versus 8.3%, p < 0.001), which represents a 21% and 66% relative increase for the younger than/older than age 50 years groups, respectively.
The KM method overestimated the risk of revision compared with the cumulative incidence method, and the difference was particularly notable in the elderly cohort. Future long-term followup studies on elderly cohorts should report results using survivorship curves that take into account the competing risk of patient death. We observed a high attrition rate as a result of patient deaths, and this emphasizes a need for future studies to enroll younger patients to ensure adequate study numbers at final followup.
Level III, therapeutic study.
在一项关于全髋关节置换术（THA）的研究随访期内死亡的患者，随后无法接受翻修手术。竞争事件的存在（如在一项关于植入物耐久性的研究中的死亡事件）违反了常用的Kaplan-Meier（KM）生存分析方法的一个假设。在这种情况下，相对于考虑竞争事件的替代方法（如累积发病率方法），基于KM的翻修频率估计会偏高。然而，在骨科临床研究中，这种差异在临床上的相关程度以及对不同年龄患者队列的影响程度，一直没有得到很好的描述。
问题/目的：本研究的目的是比较KM法与累积发病率生存估计器，以评估死亡这一竞争事件对50岁及以下和50岁以上患者THA术后长期随访中植入物生存率报告的影响程度。
我们回顾性分析了来自一位外科医生前瞻性维护的登记系统中的758例骨水泥型THA病例，这些病例至少随访20年或直至死亡。使用KM法和累积发病率法比较50岁及以下和50岁以上患者的翻修率。使用KM法计算患者生存率。在THA时年龄小于50岁的队列中，共有21%（109例中的23例）在20年随访期内死亡，而手术时年龄大于50岁的队列中这一比例为72%（649例中的467例）（p < 0.001）。
在累积发病率分析中，50岁及以下队列中有19%在20年内因无菌性原因接受了翻修，而50岁以上队列中这一比例为5%（p < 0.001）。KM法高估了翻修风险（分别为23%和8.3%，p < 0.001），这分别代表50岁及以下/50岁以上组相对增加了21%和66%。
与累积发病率法相比，KM法高估了翻修风险，且这种差异在老年队列中尤为明显。未来针对老年队列的长期随访研究应使用考虑患者死亡竞争风险的生存曲线报告结果。我们观察到因患者死亡导致的失访率很高，这强调未来研究需要纳入更年轻的患者，以确保最终随访时有足够的研究样本量。
III级，治疗性研究。
