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Kinematic gender differences in knees change after total knee arthroplasty
Differences seen between men’s and women’s healthy knees were not present following TKA.
Recent research reveals kinematic differences between healthy knees in men and women, and that these differences change greatly after total knee replacement with non-gender-specific implants.
Investigators analyzed three studies examining patients with normal knees and those who underwent total knee arthroplasty (TKA) before the advent of gender-specific prostheses. They discovered that during the first 60° of flexion, the lateral condyle of normal knees in women had a more posterior pattern of motion compared to men’s knees (P<.05), while the medial condyle was more anterior than those of men’s knees.
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They also found that normal women’s knees displayed a unique axial rotation pattern with more internal rotation (P=.005) compared to normal knees in men. However, the research revealed that after TKA, the women’s knees showed similar kinematic and axial rotation patterns to men’s knees.
Normal knees in women also demonstrated 4° more weight-bearing range of motion (P<.01) vs. the healthy knees of men, but knees in women who had TKAs showed 3° less weight-bearing range of motion compared to men’s knees following TKA. An analysis of patella tilt angles in deep flexion showed more similar kinematic patterns between men’s post-TKA knees and men’s normal knees, while a comparison of women’s normal and post-TKAs showed a loss of patella rotation. Similarly, women’s knees showed a greater change in patellofemoral contact patterns in early flexion.
“We find that the nonimplanted female knee is statistically different than the male knee,” Richard D. Komistek, PhD, said during his presentation at the Tenth Annual Insall Scott Kelly Institute Sports Medicine and Total Knee & Hip Symposium.
“It has a unique motion pattern, but the females are losing almost 7° more weight-bearing range of motion [after total knee replacement]. They are losing their ‘more’ internal axial rotation pattern and we’re seeing a change in the patellofemoral kinematic patterns.”
Images: Komistek RD |
Three studies
Komistek and his colleagues conducted two studies examining normal knees. They first analyzed the in vivo kinematics of 10 women and 10 men while another study tested the weight-bearing range of motion of 167 people.
A final study examining deep knee bending consisted of 321 TKA patients with 10 different prostheses.
An analysis of the normal knees illustrated a distinct pattern of motion in the women’s knees.
“We looked at the pattern of motion, the lateral condyle vs. the medial condyle, and the females seemed to stay more posterior throughout flexion for the first 60°,” Komistek said. “But on the medial side, the females experienced more anterior contact than the males did. This was statistically different, especially in the first 60° of flexion.”
However, the investigators found that after a TKA, men and women exhibited similar kinematic, patterns, he said.
“But before an implant, there was a visual and statistical difference.”
While the investigators found similar overall axial rotation between the normal knees in men and women (15.9° vs. 14.1°), they discovered that women’s knees remained more internally rotated then those in men.
“During the first 60° of knee flexion, the female nonimplanted knee exhibited a distinct axial rotation pattern where the knee remained more internally rotated than the male knee,” Komistek said. “After an implant, the females have lost their internal rotation pattern and have become more externally rotated compared to the males’ knees.”
Statistically significant results
A study of 167 patients with nonimplanted knees demonstrated more average weight-bearing range of motion in women (154° vs. 158°). But after an implant, the females exhibited 3° less weight-bearing range of motion, Komistek said.
Patella tilt angles in deep flexion also showed a greater change in deep flexion between the pre- and post-TKA knees in women, while the patterns between normal post-TKA knees in men were similar in pattern and magnitude.
“With respect to patellofemoral contact, we derived an interesting finding from full extension to 50° of flexion. Males exhibit a similar contact pattern on average, and for most subjects, this finding was consistent with all TKAs we analyzed,” Komistek said. “But the females, for some reason, were exhibiting a change of their patellofemoral contact pattern, where they experienced a more superior contact position after TKA.”
Komistek noted that the impact of gender-specific knee implants on female kinematics remains unknown. “In the future, we want to address this with the new gender knee to see if it will play a significant role and allow patients to get back to their kinematic patterns,” he said.
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For more information:Reference:
- Richard D. Komistek, PhD, is the Fred M. Roddy chaired professor in biomedical engineering and co-center director of the Center for Musculoskeletal Research at the University of Tennessee. He can be reached at 301 Perkins Hall, Knoxville, TN 37996; 865-974-4159; e-mail: rkomiste@utk.edu. He has indicated that he is a consultant for Zimmer Inc.
- Komistek RD. Gender TKA: Are there kinematic differences? Presented at the Tenth Annual Insall Scott Kelly Institute Sports Medicine and Total Knee and Hip Symposium. Sept. 14-16, 2007. New York.