Dual-Energy CT Assessment of Distal Femur Bone quality for Preventing Early Failure in Cementless Total Knee Arthroplasty.

BACKGROUND

With the increasing utilization of newer-generation cementless total knee arthroplasty (TKA), the preoperative prediction of bone quality has emerged as a significant concern. Recognizing such limitations of central bone mineral density, attention has turned to Hounsfield units (HU), a measure of the standardized linear attenuation coefficient in computed tomography (CT) imaging, known for its ability to estimate bone marrow density specifically around the knee joint. Consequently, this study aims to investigate the correlation between preoperative dual-energy CT (DECT) HU measurements of the distal femur and the actual bone strength. We hypothesized that DECT-derived HU would (1) significantly correlate with biomechanical bone strength and (2) serve as a reliable tool for identifying suitable candidates for cementless TKA.

MATERIALS AND

METHODS

In this prospective study, 190 knees that underwent primary posterior stabilized TKA between May 2022 and May 2023 were included. HU of the distal femur was assessed using DECT scan, which utilizes material decomposition to differentiate bone from soft tissue or bone marrow, providing more accurate bone quality assessment than conventional CT, and the actual bone strength of the corresponding bone fragment was measured using an indentation test that serves as a validated surrogate for traditional compression testing. The association between HU and actual bone strength was evaluated using correlation and linear regression analyses. To further assess its diagnostic utility in identifying candidates for cementless TKA, receiver operating characteristic (ROC) curve analysis with calculation of the area under the curve (AUC) was performed to determine both accuracy and the optimal cutoff value.

RESULTS

The DECT HU value in coronal plane showed significant correlations with bone strength measured by indentation testing (r = 0.67, p < 0.01). In linear regression analysis, coronal HU was independently predictive of bone strength (β = 0.62, R² = 0.45, p < 0.01). Furthermore, coronal HU showed good discriminative ability for identifying candidates suitable for cementless TKA (AUC = 0.82, 95% CI 0.766-0.880), with an optimal cutoff of 72 HU yielding sensitivity of approximately 73% and specificity of 74%.

CONCLUSIONS

This study demonstrates that DECT HU is a promising marker for periarticular bone quality, given its strong correlation with distal femoral bone strength and excellent performance in predicting suitability for cementless TKA. However, considering our simplified model, ethnic diversity, and CT scanner variability, these factors should be taken into account before using this threshold as a definitive clinical guide.

LEVEL OF EVIDENCE: II; Prospective diagnostic study.