THE INFLUENCE OF FIXED ROTATIONAL DEFORMITIES OF THE FEMUR ON THE PATELLOFEMORAL CONTACT PRESSURES IN HUMAN CADAVER KNEES

Patellofemoral contact pressures resulting from fixed rotational defor mities of the femur were studied in human cadaver knees. The increase in the degree of fixed rotational deformities of the femur results in a nonlinear increase in patellofemoral contact pressures on the contra lateral facets of the patella (i.e., external rotational deformity res ulted in a contact pressure increase on the medial facet, and internal rotational deformity resulted in a contact pressure increase on the l ateral facet of the patella). With the initial isometric tension of 20 0 N in the quadriceps tendon for 30 degrees, 60 degrees, 90 degrees, a nd 120 degrees knee flexion, the peak contact pressure showed no signi ficant differences between the medial and lateral facets of the patell a in its anatomic position. At 20 degrees of rotational deformity of t he femur, only a slight increase was noted for the tension in the quad riceps tendon and the patellofemoral contact pressures on the contrala teral facets of the patella. However, at 30 degrees rotational deformi ty of the femur, both the external and internal rotational deformity o f the femur showed a significant increase in the tension of the quadri ceps tendon and the patellofemoral contact pressures on contralateral facets of the patella. The greatest increase in patellofemoral contact pressures was observed at 30 degrees and 60 degrees knee flexion for both the external and internal rotational deformity of the femur. The external rotational deformity of the femur for all knee flexion angles showed significantly higher peak patellofemoral contact pressure incr eases on the medial facet of the patella as compared with the lateral patellofemoral contact pressure increase resulting from internal rotat ional deformity of the femur.