Abstract
Introduction
Accurate alignment and sizing of the femoral component in total knee arthroplasty (TKA) is important for stability and functional outcomes. In relation to the shape of the distal femur, it has been reported that the medial-lateral (ML) femur width in women is narrower than that in men for the same antero-posterior (AP) length. In addition, it has been noted that the elevation of the anterior condyle in women is lower than that in men. Therefore, in TKA for women, it is suggested that a medial or lateral overhanging femoral component can cause pain or limit the range of motion (ROM). As a result, a gender-specific implant for women has been developed. However, there are few studies addressing the morphological dimensions of the distal shape of the femur in the Japanese population. The objective of this study was to reveal the appropriateness of using gender-specific implant for Japanese women.
Methods
This study was based on 40 women (40 knees) and 40 men (40 knees) who had primary preoperative osteoarthritis of the knee. The average height was 161.2 cm for men and 149.4 cm for women. The average weight was 68.0 kg for men and 58.5 kg for women. These are significantly different. Resection of the distal femur for TKA was simulated with preoperative computed tomography (CT) data. The ML width on the anterior and distal cut surface, the ML width at the surgical epicondylar axis (SEA) level, the maximum AP length at the medial and lateral condyle, and the AP length after resection were measured. These values were compared between men and women, and compatibility with NexGen LPS-Flex and Gender Solution Femur (GSF) (Zimmer, Warsow, Ind) was evaluated.
Results
On the anterior cut surface, the average ML width was 54.0 mm for men and 47.0 mm for women. There was a significant difference between them (P<0.01). The aspect ratio (AP/ML) at the SEA level and the resected distal surface was 0.74 and 0.65 for men and 0.76 and 0.70 for women, respectively. There were significant differences between them (P<0.01).
Discussion and Conclusion
In general, the aspect ratio of the distal femur in the Japanese population was smaller than that in the Caucasian population. However, the femoral distal shape in women was narrower than that in men for the same AP length in the Japanese population. As the AP size increased, the femoral component in women tended to overhang the ML width. Therefore, the use of a gender-specific implant for women was suggested. In contrast, there were some cases in which the femoral component tended to be undersized compared with the ML width in men. [Fig. 1] For Japanese women, the use of a gender-specific component should be considered. Additionally, there is a need for further investigation of gender-specific components in men.
