# Medial cortical bone thickness of the tibial diaphysis in osteoarthritis is related to lower extremity alignment and tibial morphology

## TL;DR

This study found that osteoarthritic knees have thicker medial cortical bone in the tibia compared to healthy knees, linked to alignment and tibial shape.

## Contribution

The study identifies a novel relationship between tibial cortical bone thickness, lower extremity alignment, and tibial morphology in osteoarthritis.

## Key findings

- OA group showed thicker medial cortical bone in the proximal tibia compared to lateral areas.
- The medial-to-lateral cortical bone thickness ratio was significantly higher in OA knees than in healthy knees.
- Proximal-medial cortical bone thickness correlated with femorotibial angle and medial compartment inclination in OA patients.

## Abstract

The purpose of this study was to clarify (1) the differences in cortical bone thickness (CBT) of the tibial diaphysis between healthy and osteoarthritic knees and (2) the influences of the femorotibial angle (FTA) and inclination of the medial compartment of the proximal tibia (MCT) on tibial CBT.

The study assessed 60 subjects with varus knee osteoarthritis (OA) (22 males and 38 females; mean age, 74 ± 7 years) and 53 healthy elderly subjects (28 males and 25 females; mean age, 70 ± 6 years). Three-dimensional estimated CBT of the tibial diaphysis was automatically calculated for 2752–11,296 points using high-resolution measurements from CT. The standardized CBT was assessed in 24 regions by combining six heights and four areas. Additionally, the association between the CBT, each FTA, and MCT inclination was investigated.

The OA group showed a thicker CBT in the medial areas than in the lateral areas of the proximal tibia, while the healthy group had a thicker lateral CBT. The medial-to-lateral ratio of the proximal tibia was significantly higher in the OA group than in the healthy group. The proximal-medial CBT correlated with FTA and MCT inclinations in the OA group.

This study demonstrated that varus osteoarthritic knees showed a different trend of proximal-medial CBT with associations in FTA and MCT inclination from healthy knees, possibly due to medial load concentration.