Introduction

Traditional methods of component positioning in total hip replacement (THR) utilize mechanical alignment guides which estimate position relative to the plane of the operating room table. However, variations in pelvic tilt alter the relationship between the anatomic plane of the pelvis and that of the table such that components placed in optimal position relative the table may not land within the classic anatomic “safe zone” described by Lewinnek. It has been suggested that navigation software should incorporate adjustments for the degree of pelvic tilt. Current imageless navigation software has this capability, however there is a paucity of data regarding the accuracy of this technology.

Several studies have suggested that, in TKR, gender specific-prostheses are needed to accommodate anatomic differences between males and females. This study was performed to examine whether gender is a factor contributing to the variability of the size, shape and orientation of the patellofemoral sulcus.

3D computer models of the femur were reconstructed from CT scans of 20 male and 20 female femora. The patellofemoral groove was quantified by measuring landmarks at 10 degree increments around the epicondylar axis. The orientation of the groove was defined by the tracking path generated by a sphere moving from the top of the groove to the intercondylar notch. To assess the influence of gender on the shape of the distal femur, all morphologic parameters were normalized for differences in bone size.

Overall, the distal femur was 15% larger in males compared to females. The male condyles were 4% wider than the female for constant AP depth (p=0.13). When normalized for bone size, there was no gender difference in most patello-femoral dimensions, including the length, width, angle or tilt of the sulcus. Female femora had a less prominent medial anterior ridge (p=0.07), and a larger normalized radius of curvature of the tracking path (p=0.03). In addition, the orientation of the sulcus differed by 1–2 degrees in both the coronal and axial planes. Overall, gender explained 4.7% of the anatomic variation of the parameters examined, varying from 0 to 15.9%.

The size, shape and orientation of the patello-femoral groove are highly variable.

While the patello-femoral morphology of male and female femora are very similar, some of the anatomic variability is related to gender, particularly the prominence of the medial ridge and the sulcus radius of curvature. The biomechanical and clinical significance of these differences after TKA have yet to be determined.