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High-Flexion Knee Designs: More Hype than Hope?
The Journal of Arthroplasty Vol. 21 No. 4 Suppl. 1 2006
High-Flexion Knee Designs: More Hype than Hope? In the Affirmative Merrill A. Ritter, MD
Abstract: The range of motion after a total knee arthroplasty may be the result of design, preoperative range of motion, culture, and psychological concerns. Theoretically, a high flex–type total knee shortens the radius posteriorly at the cost of flexion stability, tibial and patellar stresses, and possible wear. Preoperative range of motion is the biggest indicator of postoperative range of motion. Cultural effects may play an effect. Until found clinically different, the range of motion after a total knee arthroplasty is dependent primarily upon preoperative range of motion. Key words: range of motion, high flex, total knee arthroplasty. n 2006 Elsevier Inc. All rights reserved.
Today, there is an ever increasing drive to increase the range of motion after total knee arthroplasty. Some cultures all but demand it, some surgeons feel their technique enhances it, and many companies state that their design promotes it. In a large study of our own, we concluded that range of motion after a total knee arthroplasty was primarily due to the preoperative range of motion and much less so to a younger age, female sex, and release of the posterior osteophytes [1]. These were noted using one total knee design, the AGC (Biomet, Warsaw, Ind). One further observation was that the largest gains in range of motion had nothing to do with the surgical technique [1]. What, then, can we say from what we know today?
Materials and Methods Between 1983 and 2000, we performed 4727 AGC total knee arthroplasties. We evaluated the effect preoperative factors, such as age, sex, diagnosis, deformity, and range of motion, and intraoperative factors, such as the degrees of medial, lateral, and posterior releases, as well as the range of motion at the end of the procedure, had upon the postoperative range of motion. There were 3 major surgical changes during this time. From 1983 to 1990, we used extramedullary instruments, ligament tensioning, and no external rotation of the femoral component; from 1990 to 1996, we used intramedullary instruments and posterior referencing without external rotation of the femoral component; and from 1996 to 2001, we used intramedullary instruments and externally rotated the femoral component 38 to 58.
From the Center for Hip and Knee Surgery, St. Francis Hospital, 1199 Hadley Road, Mooresville, IN 46158. Submitted August 10, 2005; accepted February 7, 2006. No benefits or funds were received in support of the study. Reprint requests: Merrill A. Ritter, MD, The Center for Hip and Knee Surgery, 1199 Hadley Road, Mooresville, IN 46158. n 2006 Elsevier Inc. All rights reserved. 0883-5403/06/1906-0004$32.00/0 doi:10.1016/j.arth.2006.02.088
Results Of the patients who had total knee arthroplasty, 41.7% flexed more than 1208, 14.3% more than 1258, and 5.4% more than 1308 (Fig. 1). The only factors that could affect the range of motion by
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More - Flexion Knee Designs: More Hype than Hope ! Ritter 41
2003 felt that the present high flex–type knees all shortened the posterior radius by removing more bone, thus leading to instability and possibly increased patellar and tibial stresses. Yoshina between 1987 and 1997 noted that they were able to get 11% to 20% of their Japanese population to squat fully [5,6]. There may be no doubt that, theoretically, the new high-flex designs should help gain or increase range of motion after total knee arthroplasty; however, these new designs may do this at the risk of instability and possible wear. With that said, I believe that the range of motion acquired after a total knee arthroplasty is more related to the patient and not the design of the implant or the surgical technique. Fig. 1. Two-year AGC total knee arthroplasty (range of motion, 08-1458). No medial, lateral, or anterior-posterior instability.
more than 108 was the preoperative range of motion and, to a lesser degree, the intraoperative range of motion. Still, statistically, age, sex, posterior osteophyte release, and release of the deep medial collateral ligament in large deformities had a minor effect, but nothing to the degree that the preoperative range of motion would demonstrate. None of the postoperative changes from 1983 to 2001 had any effect upon the postoperative range of motion.
Discussion Agaki et al [2] in 2000 evaluated the Bisurface total knee arthroplasty and found the average range of motion was 1248; however, 20% were loose and 2% were revised because of instability. Allen et al [3] in 2002 compared the Legacy and the LPS flex and found no difference between the 2 groups as regarded range of motion. Ranawat [4] in
References 1. Ritter MA, Harty LD, Davis KE, et al. Predicting range of motion after total knee arthroplasty: clustering, loglinear regression, and regression tree analysis. J Bone Joint Surg Am 2003;85-A:1278. 2. Agaki M, Nakamura T, Matsusue Y, et al. The Bisurface total knee replacement: a unique design for flexion. Four-to-nine year follow-up study. J Bone Joint Surg Am 2000;82:1626. 3. Allen DG, Beers C, Trammell R. Postoperative evaluation of the Nexgen legacy posterior stabilized LPS flex implants. La Societe Internationale de Chiragie Orthopedic et de Traumalologic/La Societe Internationale de Recherche Orthopedic et de Traumalologic, XXII World Congress, San Diego 2002;542. 4. Ranawat CS. Design may be counterproductive in optimizing flexion after TKR. Clin Orthop 2003; 416:174. 5. Soshino S, Shoji H, Komagamine M. Full flexion after total knee replacement in rheumatoid arthritis. Int Orthop 1990;14:13. 6. Yoshina S, Nakamura H, Shiga H, et al. Recovery of full flexion after total knee replacement in rheumatoid arthritis. Int Orthop 1997;21:98.
High-Flexion Knee Designs: More Hype than Hope? In the Affirmative Merrill A. Ritter, MD
Abstract: The range of motion after a total knee arthroplasty may be the result of design, preoperative range of motion, culture, and psychological concerns. Theoretically, a high flex–type total knee shortens the radius posteriorly at the cost of flexion stability, tibial and patellar stresses, and possible wear. Preoperative range of motion is the biggest indicator of postoperative range of motion. Cultural effects may play an effect. Until found clinically different, the range of motion after a total knee arthroplasty is dependent primarily upon preoperative range of motion. Key words: range of motion, high flex, total knee arthroplasty. n 2006 Elsevier Inc. All rights reserved.
Today, there is an ever increasing drive to increase the range of motion after total knee arthroplasty. Some cultures all but demand it, some surgeons feel their technique enhances it, and many companies state that their design promotes it. In a large study of our own, we concluded that range of motion after a total knee arthroplasty was primarily due to the preoperative range of motion and much less so to a younger age, female sex, and release of the posterior osteophytes [1]. These were noted using one total knee design, the AGC (Biomet, Warsaw, Ind). One further observation was that the largest gains in range of motion had nothing to do with the surgical technique [1]. What, then, can we say from what we know today?
Materials and Methods Between 1983 and 2000, we performed 4727 AGC total knee arthroplasties. We evaluated the effect preoperative factors, such as age, sex, diagnosis, deformity, and range of motion, and intraoperative factors, such as the degrees of medial, lateral, and posterior releases, as well as the range of motion at the end of the procedure, had upon the postoperative range of motion. There were 3 major surgical changes during this time. From 1983 to 1990, we used extramedullary instruments, ligament tensioning, and no external rotation of the femoral component; from 1990 to 1996, we used intramedullary instruments and posterior referencing without external rotation of the femoral component; and from 1996 to 2001, we used intramedullary instruments and externally rotated the femoral component 38 to 58.
From the Center for Hip and Knee Surgery, St. Francis Hospital, 1199 Hadley Road, Mooresville, IN 46158. Submitted August 10, 2005; accepted February 7, 2006. No benefits or funds were received in support of the study. Reprint requests: Merrill A. Ritter, MD, The Center for Hip and Knee Surgery, 1199 Hadley Road, Mooresville, IN 46158. n 2006 Elsevier Inc. All rights reserved. 0883-5403/06/1906-0004$32.00/0 doi:10.1016/j.arth.2006.02.088
Results Of the patients who had total knee arthroplasty, 41.7% flexed more than 1208, 14.3% more than 1258, and 5.4% more than 1308 (Fig. 1). The only factors that could affect the range of motion by
40
More - Flexion Knee Designs: More Hype than Hope ! Ritter 41
2003 felt that the present high flex–type knees all shortened the posterior radius by removing more bone, thus leading to instability and possibly increased patellar and tibial stresses. Yoshina between 1987 and 1997 noted that they were able to get 11% to 20% of their Japanese population to squat fully [5,6]. There may be no doubt that, theoretically, the new high-flex designs should help gain or increase range of motion after total knee arthroplasty; however, these new designs may do this at the risk of instability and possible wear. With that said, I believe that the range of motion acquired after a total knee arthroplasty is more related to the patient and not the design of the implant or the surgical technique. Fig. 1. Two-year AGC total knee arthroplasty (range of motion, 08-1458). No medial, lateral, or anterior-posterior instability.
more than 108 was the preoperative range of motion and, to a lesser degree, the intraoperative range of motion. Still, statistically, age, sex, posterior osteophyte release, and release of the deep medial collateral ligament in large deformities had a minor effect, but nothing to the degree that the preoperative range of motion would demonstrate. None of the postoperative changes from 1983 to 2001 had any effect upon the postoperative range of motion.
Discussion Agaki et al [2] in 2000 evaluated the Bisurface total knee arthroplasty and found the average range of motion was 1248; however, 20% were loose and 2% were revised because of instability. Allen et al [3] in 2002 compared the Legacy and the LPS flex and found no difference between the 2 groups as regarded range of motion. Ranawat [4] in
References 1. Ritter MA, Harty LD, Davis KE, et al. Predicting range of motion after total knee arthroplasty: clustering, loglinear regression, and regression tree analysis. J Bone Joint Surg Am 2003;85-A:1278. 2. Agaki M, Nakamura T, Matsusue Y, et al. The Bisurface total knee replacement: a unique design for flexion. Four-to-nine year follow-up study. J Bone Joint Surg Am 2000;82:1626. 3. Allen DG, Beers C, Trammell R. Postoperative evaluation of the Nexgen legacy posterior stabilized LPS flex implants. La Societe Internationale de Chiragie Orthopedic et de Traumalologic/La Societe Internationale de Recherche Orthopedic et de Traumalologic, XXII World Congress, San Diego 2002;542. 4. Ranawat CS. Design may be counterproductive in optimizing flexion after TKR. Clin Orthop 2003; 416:174. 5. Soshino S, Shoji H, Komagamine M. Full flexion after total knee replacement in rheumatoid arthritis. Int Orthop 1990;14:13. 6. Yoshina S, Nakamura H, Shiga H, et al. Recovery of full flexion after total knee replacement in rheumatoid arthritis. Int Orthop 1997;21:98.