Subjective Analysis of the Filling of an Acetabular Osteolytic Lesion Following Percutaneous Cementoplasty: Is It Reliable?

Purpose: To study the interobserver agreement for the analysis of lesion filling following cementoplasty of an acetabular osteolytic lesion, and investigate how subjective analysis compares to volumetric analysis.

Materials And Methods: A total of 21 acetabular osteolysis were retrospectively analysed on pre- and immediate post-cementoplasty CT-scans by two senior interventional radiologists and one resident using a 4 grade scale to quantify lesion filling (F): F ≤ 25%, 25% < F ≤ 50%, 50% < F ≤ 75% or F > 75%. Volumetric analysis (F) was performed with the delineation of the osteolysis and the cement using regions of interest. The interobserver agreement for F was evaluated using the Fleiss' Kappa test for the 4 grade scale and for a simplified 2 grades scale (F ≤ 50% and F > 50%). The performance of F versus F (considered as the gold standard) was then evaluated for each reader using the calculation of accuracy and error to reference for the 4 grades scale and accuracy, sensitivity, specificity, positive predictive value and negative predictive value for the 2 grade scale.

Results: Interobserver agreement was considered as very low (< 0.2) for the 4 grade scale analysis and as low (> 0.2 and < 0.4) for the 2 grade scales analysis with kappa factors of 0.196 and 0.36 respectively. Compared to volumetric analysis, the overall accuracy of the 4- and 2- grade scales were 36.5% and 60% respectively.

Conclusion: Subjective evaluation of cement filling of an acetabular osteolytic lesion is associated with poor interobserver agreement and overestimation of the percentage compared to volumetric analysis.