Effects of different heights of simulated joint lines on patellofemoral joint contact pressure in total knee arthroplasty / 第二军医大学学报

ABSTRACT

Objective: To discuss the effects of different joint line heights on patellofemoral joint (PFJ) contact pressure at different knee flexion angels in human cadaveric total knee arthroplasty. Methods: Seven normal fresh-frozen human cadaveric knees with intact joint cartilage were tested on an Instron 8501 testing machine with a load of 30 kg. The load of quadriceps tendon was adjusted to balance the specimen at the desired angles. Total knee arthroplasty were performed with femurs of increased lengths (i. e. the heights of joint line were +2 mm, +4 mm, and +6 mm) and tibial plateaus of different heights. The peak PFJ contact pressure was measured with Fuji pressure-sensitive film before and after total knee arthroplasty. Results: After total knee arthroplasty, at knee flexion angles of 60°, 90° and 120°, the peak contact pressures of lateral PFJ facet were significantly higher when the heights of joint line were +4 mm and +6 mm than those when the heights of joint line were 0 and +2 mm (P<0.05); at knee flexion angles of 30°, 60°, 90° and 120° the peak contact pressure of medial PFJ facet were significantly higher when the heights of joint line were +6 mm than those when the heights of joint line were 0, +2 mm, and +4 mm (P<0.05). Conclusion: The peak PFJ contact pressure increases if the height of joint line is elevated by more than 4 mm in total knee arthroplasty, so the variation of joint line should be controled within 4 mm in total knee arthroplasty.