Evaluation of intra- and interobserver reliability in the assessment of the \u2018critical trochanter angle\u2019

Sebastian Serong,Ivica Zovko,Marcel Haversath,Moritz Schutzbach,Marcus Jäger,Stefan Landgraeber

doi:10.1186/s40001-020-00469-4

Abstract

BackgroundThe recently described ‘critical trochanter angle’ (CTA) is a novel parameter in the preoperative risk assessment of stem malalignment in total hip arthroplasty. As its reproducibility needs to be evaluated, the given study aims to investigate intra- and interobserver reliability. It is hypothesized that both analyses justify the clinical use of the CTA.MethodsA total of 100 pelvic radiographs obtained prior to total hip arthroplasty were retrospectively reviewed by four observers with different levels of clinical experience. The CTA was measured twice by each observer at different occasions in the previously described technique. Intra- and interobserver reliability was evaluated using intraclass correlation coefficients (ICC) with confidence intervals (CI) and the Bland–Altman approach.ResultsThe mean CTA in both measuring sequences was 20.58° and 20.78°. The observers’ means ranged from 17.76° to 25.23°. Intraobserver reliability showed a mean difference of less than 0.5° for all four observers (95% limit of agreement: − 7.70–6.70). Intraobserver ICCs ranged from 0.92 to 0.99 (CI 0.88–0.99). For interobserver variation analysis, ICCs of 0.83 (CI 0.67–0.90) and 0.85 (CI 0.68–0.92) were calculated.ConclusionAnalyses concerning intra- and interobserver reliability in the assessment of the CTA showed ‘very good’ and ‘good’ results, respectively. In view of these findings, the use of the CTA as an additional preoperative parameter to assess the risk of intraoperative stem malalignment seems to be justified.

Highlights

The recently described ‘critical trochanter angle’ (CTA) is a novel parameter in the preoperative risk assessment of stem malalignment in total hip arthroplasty
Preoperative planning is mandatory when performing total hip arthroplasty (THA) because it reduces the risk of inaccurate biomechanical reconstruction and may prevent over- and undersizing of implant components [1,2,3]
The mean difference between both test series of all observers was less than 0.5° with the 95% limits of agreement ranging from -7.70° to 6.77°

Summary

Introduction

The recently described ‘critical trochanter angle’ (CTA) is a novel parameter in the preoperative risk assessment of stem malalignment in total hip arthroplasty. Serong et al Eur J Med Res (2020) 25:67 preoperative risk assessment of stem malalignment [11]. This novel geometric angle does not measure the trochanter overhang alone, but the overhang in relation to the femur shaft axis. It is independent of the individual size of the hip. Varus stem alignment of two degrees and more had a sensitivity of 90% and a specificity of 80% in patients with a preoperative CTA of 22.75° or less [11]

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Results

Discussion

Conclusion