Accuracy of a novel extramedullary femoral alignment guide system in primary total knee arthroplasty

Introduction

We aimed to assess the accuracy of a new extramedullary guide system for achieving appropriate femoral component alignment in total knee arthroplasty (TKA) and to determine whether it differed between patients operated on by different surgeons.

Materials and methods

We performed 100 consecutive primary TKAs in 100 patients using a newly developed extramedullary guide, the “S guide”; 50 were performed by author KM at A Hospital, and 50 by author NM at B Hospital. All patients received the Vanguard RP mobile-bearing prosthesis (Biomet Japan, Tokyo, Japan). We assessed the coronal and sagittal alignment of the femoral component with the mechanical axis using plane radiographs. Data were analyzed statistically using Prism 5.0 software, and a p value of <0.05 was regarded as indicating significance.

Results

The mean postoperative coronal alignment angle of the femoral component (α) was 0.1° ± 1.4°, with no significant differences between A Hospital and B Hospital (p = 0.67), and 98 % of patients had an α deviating by less than 3° from the mechanical axis. The mean postoperative sagittal alignment angle of the femoral component (γ) was 1.7° ± 1.7°, with no significant differences between the groups (p = 0.61), and 86 % of patients had a γ deviating by less than 3° from the mechanical axis.

Conclusions

This study shows that the S-guide is reliable for use in TKA.