[Determination of the axis after totalendoprosthesis of the knee: functional X-ray photography as golden standard]

Abstract

Aim: To examine the question of which X-ray photography technique should be given preference after implantation of total endoprosthesis of the knee.

Method: 20 patients (age 74.1; 12 men, 8 women) with total endoprosthesis of the knee (Type Sigma, PFC, Johnson and Johnson) because of primary athrosis. Postoperatively X-ray photographs of the whole leg in standing and 40 x 20 a. p. in a flat position were taken. The angles of the axis were determined and the information analysed.

Results: By means of X-ray photography of the whole leg we obtained the following angles: caput-collum-diaphyse 125 +/- 4.3 degrees, femur/basis of the knee 83.2 +/- 2.6 degrees, mechanical femur axis/basis of the knee 89.3 +/- 1.8 degrees, tibia/basis of the talus 89.2 +/- 2.2 degrees. With the 40 x 20 a. p. X-ray photographs we determined the following angles: femur/basis of the knee 82.3 +/- 3.1 degrees, basis of knee/tibia 92.2 +/- 3,6 degrees. Correlating the angles of femur/basis of the knee and basis of the knee/tibia were relations of 0.42 (p < 0.05) and 0.27 (p < 0.05).

Conclusion: For gaining information about the axis of the leg under functional conditions, one should give preference to X-ray photography of the whole leg.