School of Physical Therapy, Faculty of Health Sciences, Western University, London, Canada.
Fowler Kennedy Sport Medicine Clinic, London, Canada.
Health Qual Life Outcomes. 2023 Sep 12;21(1):104. doi: 10.1186/s12955-023-02186-y.
The International Knee Documentation Committee Subjective Knee Form (IKDC) is the most highly recommended patient reported outcome measure for assessing patients with anterior cruciate ligament (ACL) injuries and those undergoing ACL reconstruction (ACLR) surgery. The IKDC was developed as a unidimensional instrument for a variety of knee conditions. Structural validity, which determines how an instrument is scored, has not been definitively confirmed for the IKDC in respondents with ACL injuries, and in fact an alternative two-factor/subscale structure has been proposed in this population. The purpose of this study was to determine the most appropriate structure and scoring system for the IKDC in young active patients following ACL injury.
In total, 618 young patients deemed at high risk of graft rupture were randomized into the Stability 1 trial. Of the trial participants, 606 patients (98%) completed a baseline IKDC questionnaire used for this analysis. A cross sectional retrospective secondary data analysis of the Stability 1 baseline IKDC data was completed to assess the structural validity of the IKDC using exploratory and confirmatory factor analyses. Factor analyses were used to test model fit of the intended one-factor structure, a two-factor structure, and alternative four-factor and bifactor structures (i.e., a combination of a unidimensional factor with additional specific factors) of the IKDC, in a dataset of young active ACL patients.
The simple one-factor and two-factor structures of the IKDC displayed inadequate fit in our dataset of young ACL patients. A bifactor model provided the best fit. This model contains one general factor that is substantially associated with all items, plus four secondary, more specific content factors (symptoms, activity level, activities of daily living, and sport) with generally weaker associations to subsets of items. Although the single-factor model did not provide unambiguous support to unidimensionality of the IKDC based on fit indices, the bifactor model supports unidimensionality of the IKDC when covariance between items with similar linguistic structure, response options, or content are acknowledged.
Overall, findings of a bifactor model with evidence of a reliable general factor well defined by all items lends support to continue interpreting and scoring this instrument as unidimensional. This should be confirmed in other samples. Clinically, based on these findings, the IKDC can be represented by a single score for young active patients with ACL tears. A more nuanced interpretation would also consider secondary factors such as sport and activity level.
The Stability 1 trial for which these data were collected was registered on ClinicalTrial.gov (NCT02018354).
国际膝关节文献委员会主观膝关节评分（IKDC）是评估前交叉韧带（ACL）损伤患者和接受 ACL 重建（ACLR）手术患者的最推荐的患者报告结果测量工具。IKDC 作为一种用于各种膝关节疾病的一维工具而开发。结构效度（决定仪器如何评分）尚未在 ACL 损伤患者的 IKDC 中得到明确确认，实际上，在该人群中已经提出了替代的两因素/子量表结构。本研究的目的是确定 ACL 损伤后年轻活跃患者 IKDC 的最合适结构和评分系统。
共有 618 名被认为有较高前交叉韧带断裂风险的年轻患者被随机分配到稳定性 1 试验中。在该试验参与者中，有 606 名患者（98%）完成了用于此分析的基线 IKDC 问卷。对稳定性 1 基线 IKDC 数据进行横断面回顾性二次数据分析，使用探索性和验证性因子分析评估 IKDC 的结构效度。因子分析用于测试 IKDC 的预期单因素结构、双因素结构以及替代的四因素和双因素结构（即一维因素与其他特定因素的组合）在年轻活跃 ACL 患者数据集的模型拟合。
在我们的年轻 ACL 患者数据集，IKDC 的简单单因素和双因素结构显示出不合适的拟合。双因素模型提供了最佳的拟合。该模型包含一个与所有项目都有很大关联的一般因素，以及四个次要的、更具体的内容因素（症状、活动水平、日常生活活动和运动），与项目的子集关联较弱。虽然基于拟合指数，单因素模型没有提供 IKDC 一维性的明确支持，但当承认具有相似语言结构、响应选项或内容的项目之间的协方差时，双因素模型支持 IKDC 的一维性。
总体而言，具有所有项目可靠的一般因素的双因素模型的发现支持继续将该工具解释和评分作为一维。这应在其他样本中得到证实。从临床角度来看，根据这些发现，对于 ACL 撕裂的年轻活跃患者，IKDC 可以用一个单一的分数来表示。更细致的解释还可以考虑运动和活动水平等次要因素。
这些数据所来源于的稳定性 1 试验在 ClinicalTrials.gov 上注册（NCT02018354）。
