MODIFICATIONS OF THE GEOMETRY OF THE UPPER END OF THE FEMUR IN PRIMARY HIP ARTHRITIS

Abstract

Aim: The evaluation and guantification of radiologic parameters observed in the late stages of hip arthritis.

Materials and Methods : The present study concerns the retrospective evaluation of the preoperative X-rays of 80 patients affected from primary hip arthritis only on one side in an advanced stage, that were treated in our department with total hip arthroplasty. From the present study we excluded patients with hip arthritis secondary to trauma, rheumatoid arthritis or congenital hip dislocation. The onset of the symptoms ranged between six months and twenty years (mean time5, 6 years).

We evaluated the following parameters:

• Neck-shaft angle

• The thickening of the Calcar

• The Bone loss-sedimentation of the head of the femur

• The cortex thickness at the level of the lesser trochanter

• The distance-on the axis of the femur’s neck-between the rotation center of the hip and the point where the above axis crosses the transtrochanteric line.

These parameters were measured from two idependent observers. Every single measurement was done twice from both observersjn order to estimate the interobserver and the intraobserver error. The measurements were done in both hips of the patients-the affected and the healthy one-on an A-P pelvis radiogramm.

Results: From the above measurements, it results that in hip arthritis the neck-shaft angle changes (it becomes varous).The calcar was found thickened in the affected hip in a mean value of 1,45mm. The thickness of the cortex at the level of the lesser trochanter was found greater in the non-affected side in a mean value of 0,7mm. The bone loss of the femur head was approximately 2,5mm. The distance between the rotation center of the hip and the point at which the neck axis crosses the transtrochanteric line was found greater in the non-affected side, in a mean value of 3,12mm.

Conclusions: The modifications observed in hip arthritis that concern the load transmission across the neck of the femur result in changes that can be radiologically identified and measured. In the first place the thickness of the calcar is influenced, as it does the distance between the rotation center of the hip and the trochanteric line. In the advanced stages of hip arthritis the sedimentation (bone loss) of the femur head can also be measured.