# Central Bone Mineral Density Is Not a Reliable Surrogate for Assessing Suitable Bone Strength for Cementless Total Knee Arthroplasty

## TL;DR

This study shows that central bone mineral density is not a reliable indicator of bone strength for cementless knee replacement surgery, especially in Asian women.

## Contribution

The study demonstrates that central BMD is not a reliable predictor of distal femoral bone strength for cementless TKA.

## Key findings

- No significant differences in bone strength were found between osteopenia and osteoporosis groups.
- A significant portion of patients with normal cBMD were unsuitable for cementless TKA.
- cBMD had low sensitivity and specificity for predicting cementless TKA suitability.

## Abstract

Background/Objectives: Central bone mineral density (cBMD) is widely utilized for assessing bone quality, but its reliability as a predictor of knee bone strength for cementless total knee arthroplasty (TKA) remains unclear. This study aimed to determine whether cBMD reliably estimates bone strength suitable for cementless fixation. Methods: 188 patients scheduled for TKA underwent preoperative cBMD assessment of the lumbar spine and femoral neck. During surgery, femoral bone specimens were collected for indentation tests. We compared distal femoral bone strength among osteoporosis classification groups (normal, osteopenia, osteoporosis) and examined the distribution of cementless suitable versus cemented mandatory cases with chi-square tests. ROC analysis evaluated cBMD’s diagnostic performance in predicting cementless TKA suitability, with AUC, sensitivity, and specificity calculated for both measurement sites. Results: No significant differences in distal femoral bone strength existed between osteopenia and osteoporosis groups (p = 0.845 for lumbar spine, p = 0.857 for femoral neck). Among patients with normal cBMD, 35.4% (lumbar spine) and 30.7% (femoral neck) were unsuitable for cementless TKA, whereas 30.8% and 45.0% of osteoporotic patients, respectively, had adequate bone strength for cementless fixation. The AUC values for predicting cementless suitability were 0.656 (lumbar spine) and 0.669 (femoral neck), with sensitivity and specificity below 0.75 for both measurements. Conclusions: Central BMD does not reliably represent distal femoral bone strength and demonstrates inadequate predictive capability for identifying appropriate candidates for cementless TKA in this predominantly Asian female cohort. Future multi-center, multi-ethnic studies are needed to enhance generalizability.