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Optimizing Flexion in Total Knee Replacement
The Canadian Orthopaedic Association has invited our commercial partners to submit articles to the COA Bulletin that describe some of the research and development that is currently being undertaken by industry in search for new and innovative devices in orthopaedics. The following article has been submitted by DePuy, a Johnson & Johnson Company.
The COA does not recommend or endorse any specific products that may be presented or mentioned in this article.
Design Specific Increase in Range of Motion with the PFC Sigma RP-F TKR:
A Matched -Pair Study
Chitranjan S. Ranawat, M.D.
New York, NY
A.S. Ranawat, M.D.
S.K. Gupta
B. Zikria
J. Zikria
Introduction
The new PFC Sigma RP-F knee has been designed to permit 155º of flexion after TKR without compromising wear, polyethylene contact stresses, patello-femoral tracking, or stability by utilizing a third articulating condyle in the post-cam mechanism. This study explores the question of whether component design can influence postoperative ROM after TKR independent of preoperative ROM.
Materials and Methods
From July 2004 to March 2005, 50 posterior-stabilized PFC RP-F knees were performed in 45 patients who were matched to 50 RP knees in 45 patients for age, sex, BMI, preoperative diagnosis, duration of follow-up and preoperative ROM as shown in Table 1. Clinical and radiographic analysis was done according to criteria defined by The Knee Society.
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P.F.C. Sigma RP-F
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P.F.C. Sigma PS RP
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p value
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Number of TKA
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50
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50
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Follow-up (months)
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6.6 (range 3-12)
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8 (range 3-12)
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Age (years)
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67 (range 48-84)
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68.5 (range 48-89)
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0.5
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BMI
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28 (range 20.9-36.8)
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28.7 (range 22.1-41)
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0.5
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Sex M:F
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10:35
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10:35
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Preop diagnosis
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Osteoarthritis 50
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Osteoarthritis 50
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Mean Preop ROM
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110º (60º-130º)
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110º (70º-130º)
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0.4
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Mean Postop ROM
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122º (range 90º-150º)
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126º (90º-130º)
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.04
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Increase in ROM if Preop ROM < 120º
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15º
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7º
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.04
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Discussion
This study is the first to suggest that patients with less motion have more to gain from the RP-F design. This was most apparent in patients with less than 120º of motion. With the new PFC Sigma RP-F design, greater knee ROM after TKR can be achieved independent of the patient's preoperative ROM. Future primary TKRs may need to incorporate the design features of the RP-F knee to maximize potential ROM.
Financial Disclosure: e - DePuy Ortho
C. Ranawat paper presented at the AAOS, March 2006
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