The inclination of the tibial component has an impact on fracture stability in unicompartmental knee arthroplasty: an artificial bone study

TL;DR

Slight varus positioning of tibial components in knee surgery increases fracture resistance, reducing the risk of periprosthetic fractures.

Contribution

Demonstrates that 3° varus inclination improves fracture load in unicompartmental knee arthroplasty using an artificial bone model.

Findings

A 3° varus position increased fracture load by 34% compared to neutral positioning.

No further significant increase in fracture load was observed at 6° varus.

The mobile meniscal bearing may improve load distribution and fracture resistance.

Abstract

Periprosthetic fractures (PPFs) following unicompartmental knee arthroplasty (UKA) are a significant clinical challenge. Tibial component positioning may influence fracture risk, but the biomechanical effects of varus inclination on fracture loading remain unclear.

We investigated the effect of tibial component varus inclination on fracture load using the Oxford® Partial Knee implant system, synthetic tibiae and a dynamic loading model. Tibial components were implanted at neutral (0°), 3° and 6° varus angles. Vertical loading was applied until fracture and fracture loads were compared between groups.

A 3° varus position significantly increased fracture load by 34% compared to neutral (p < 0.05). No further statistically significant increase was observed at 6° varus. The dynamic model suggested that the mobile meniscal bearing may contribute to an improved load distribution, thereby increasing fracture resistance.

Slight varus inclination of the tibial component in UKA increases the medial tibial fracture load, potentially reducing the risk of PPF. Our findings highlight the biomechanical advantages of controlled varus positioning and provide insight into optimizing implant alignment.

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