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High-flexion and gender differences in total knee arthroplasty: Korean-population study questions benefits
Young-Hoo Kim, MD, answers 4 Questions about the use of specialized implants in a specific patient population.
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For this month’s interview, I have asked Young-Hoo Kim, MD, to share some aspects of his and his colleagues’ recent study looking to see if there are additional benefits in the Korean population when using a hyper-flex and gender-specific knee. Ideally, this study should be duplicated in different ethnic groups as the authors’ findings from this recent study challenge some claims made to date.
I have been told that the hyper-flex knee was especially beneficial in the Asian population and justified the additional premium charges. To date, gender-sizing and hyperflexion designs have yet to establish improved outcomes in several different populations. Kim and colleagues’ study of simultaneous bilateral knee replacements of two designs provides a good side-by-side comparison in his study population.
This type of data continues to challenge the “premium charges” on recently introduced knee replacements by all distributors. It is up to the companies and designers to demonstrate these new knee designs and nuances merit higher prices documented by scientific outcomes to substantiate their claims.
Douglas W. Jackson, MD
Chief Medical Editor
Douglas W. Jackson, MD: How did you design your study to compare these two knees?
 Young-Hoo Kim |
Young-Hoo Kim, MD: We enrolled 85 patients (170 knees) who had sequential simultaneous bilateral total knee arthroplasty. The patients were then randomized to receive a standard or gender-specific NexGen LPS-Flex (Zimmer) prosthesis. This was accomplished with use of a sealed study number envelope, which was opened in the operating room before the skin incision was made.
Jackson: What was your follow-up period and what comparisons did you evaluate?
Kim: The mean duration of follow-up was 2.13 years (range 2 to 2.3 years). Knee Society knee scores, Hospital for Special Surgery knee scores, WOMAC scores, radiographic results, and aspect ratio o the distal femur and femoral component were evaluated and compared in the two groups.
Jackson: What conclusions did you draw from your excellent study?
Kim: We can conclude that early clinical and radiographic outcomes, range of knee motion, patient satisfaction, revision rates, and complication rates were similar in both groups. However, the duration of follow-up was short and we can draw no conclusions about the advantage of gender-specific NexGen LPS-Flex prosthesis with regard to long-term function.
Jackson: How did this information affect the choice of prosthesis in your institution?
Kim: We choose a proper size of standard total knee prosthesis for both male and female patients.
Reference:
- Kim YH, Chio J, Kim JS. Comparison of a standard and a gender-specific posterior-cruciate-substituting high-flexion total knee prosthesis: A prospective, randomized, short-term outcome study. J Bone Joint Surg (Am). 2010; 92:1911-1920. doi: 10.2106/JBJS.1.00910
- Young-Hoo Kim, MD, is a professor and clinical director of The Joint Replacement Centre of Korea, Ewha Womans University, School of Medicine, MokDong Hospital, 911-1 MokDong, YangChun-Gu, Seoul 158-710, Korea. He can be reached at younghookim@ewha.ac.kr.
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