[Sagittal changes induced by knee arthroplasty: a radiologic study]

Abstract

Purpose of the study: To quantify the modifications occurring on the femoral side, after Total Knee Arthroplasty, we describe a method of measurements in the sagittal plane on standardized X-rays.

Material and methods: We report the clinical and radiologic results of a prospective study of 80 cases of Total Knee Arthroplasty performed with the same prosthesis. We eliminated twenty cases with incorrect X-rays. Measurements were done on 60 preoperative X-rays and 60 postoperative X-rays. The aim of the measure was to quantify the modifications induced by the prosthesis on the trochlear groove and on the tibio-femoral joint line in full extension and in flexion, to eliminate individual femoral diameter was used as a reference in order to cancel variations in X-rays magnification. We first validated the two perpendicular reference axis on which we based all the measurements.

Results: No significative difference was found on the position of the tibio-femoral joint line in flexion. The tibio-femoral joint line in extension was significantly moved distally. The prosthesis was placed too distally, therefore we changed the operative procedure. No significative difference was found on the position of the anterior trochlear groove.

Discussion: With this method, the anatomic variations of the femoral profiles can be quantified, therefore, further prosthesis shapes can be improved. Radiological follow-up of knee prosthesis and comparison of the influence of different prosthesis can be made by these measures.