Precise bone cut is fundamental in total knee arthroplasty. However, notching of anterior femoral is not uncommon in clinical practice. Reviewing the article, notching and its complication may reach up to 30% and 2.5%, and there is scanty study of notching on the femoral strength. We therefore conduct the finite element analysis to elucidate the effect of notching on femoral mechanical strength. The computerized tomography images were used as the basis to develop the knee model, which was assumed mainly to consist of cortical and cancellous bones. For the implant joint, Zimmer data was considered partly as the basis to develop the model. This study investigated the femoral improper cut effect on the surgery with a static standing condition. The results show that the anterior femoral cut should be undercut 2 mm to overcut 1 mm during the surgery, in order to prevent bone materials from yielding. The exposure of the cancellous bone may cause bone materials to yield when the femur overcut was 2 mm; the cancellous bone may load too much and result in a fracture when the undercut was 3 mm. The effect of undercut, which was rarely discussed, was particularly addressed in our study. Precise femoral cut is crucial for the longevity of total knee arthroplasty.

Background: Polyethylene (PE) wear is a major contributor to implant loosening following total knee arthroplasty (TKA). Advanced bearings are therefore required in TKA to reduce or eliminate wear-related loosening. A recently introduced bearing that combines oxidized zirconium with highly cross-linked PE has been shown to drastically reduce wear in in vitro settings, due to its improved tribological characteristics in both tibial and femoral components. However, there are no data on its cost-effectiveness.

Data and Methods: A Markov model was developed to assess the cost-effectiveness of this low-wear bearing from a German societal perspective. The model population was derived from a registry of 75,000 patients requiring TKA. The model allocated patients to receive either a low-wear or standard articulation, and followed them until death. Revisions and re-revision were included. Input values were derived from registry databases or from published reports in the literature. Threshold analysis and probabilistic sensitivity analysis were conducted to estimate model robustness.

Results: The low-wear articulation prevented 24 (2.4 percent) revisions and 8 (0.8 percent) re-revisions. The total incremental cost-effectiveness ratio (ICER) of the low-wear articulation was EUR 16,474 per quality-adjusted life-year (QALY). For patients aged less than 55 years, an ICER of EUR 653 per QALY was observed. For patients aged over 75 years, this value was EUR 83,300. Threshold and probabilistic sensitivity analysis indicated that these findings were reasonably robust.

Conclusion: Low-wear articulations may be considered cost-effective, although the cost effectiveness is age-dependent, with the cost per QALY being significantly lower for younger people than for older people.