HIFLEX KNEE PROSTHESIS – DOES HIGH FLEXION TRANSLATES INTO IMPROVED FUNCTION
PREVIEW
Total joint replacement is the most technologically advanced solution for arthritic pain, however a search for a better functional and durable prosthesis still continues. The original Total Condylar design was very successful in terms of pain relief and durability but the average post op flexion achieved was only around 900 to 950 [1-7]. Even though this may be enough for most of the daily activities in the western world [8], Asians and particularly Indians require higher flexion for most of their daily social habits and customs [9]. In the recent times a number of additional design modifications have been introduced to achieve this goal [10, 11]. However how much impact this increase in the flexion has on patient satisfaction is yet to be determined.
RECENT LITERATURE
Minoda et al [2009] analysed range of motion of standard and hi-flex cruciate retaining prosthesis prospectively [12]. They had 89 knees with standard and 87 knees with high flexion CR total knee prostheses [both Next Gen brands]. Differences in age, gender, diagnosis, preoperative ROM of the knee, and Knee Society Score between the 2 groups were not statistically significant. At 12-month follow-up, average ROM was 112.0° ± 12.6° for standard, and 115.3° ± 13.4° for high-flexion CR prosthesis (P = .101). They found no significant differences between groups with regard to ROM, clinical, or radiographic parameters.
Seon et al [2009] analysed 100 knees with 50 knees in each category of Hi-flex and standard total knee prosthesis [13]. At the time of the final follow-up, the average maximal non-weight-bearing flexion was 135.3⁰ for the knees in the high-flexion group and 134.3⁰ for the knees in the standard group; the difference was not significant. Moreover, no significant difference was found between the groups in terms of weight-bearing flexion (124.8⁰ in the high-flexion group and 123.7⁰ in the standard group) and the number of knees that allowed kneeling and sitting cross-legged. The average Hospital for Special Surgery knee score was 94.4 points in the high-flexion group and 92.4 points in the standard group; the difference was not significant. The Western Ontario and McMaster Universities Osteoarthritis Index scores also showed no significant difference between the groups. Thus no functional difference was noted in two groups.
Nutton et al [2008] performed prospective randomised comparison of the functional outcome in patients receiving either a NexGen LPS-Flex or the standard design [14]. The study included total of 56 patients, half of whom received Hi-flex and standard knee prosthesis each. They found that there was no significant difference in outcome, including the maximum knee flexion, between patients receiving the standard and high flexion designs of this implant.
Gupta et al [2006] reported a significant improvement in the post-operative range of movement using a high flexion rotating platform design when compared with a standard design of rotating-platform TKR [15]. Similarly, Bin and Nam [2007] found a significant improvement in knee flexion at one year after operation in patients receiving a high flexion design compared with a standard knee replacement, particularly in patients with a pre-operative range of flexion of less than 90° [16].
Kim, Sohn and Kim [2005] were unable to show a significant improvement in knee flexion using a NexGen LPS-Flex knee replacement [17]. In their study, the standard design was used in one knee and high flexion prosthesis in the other. After a mean of 2.1 years the mean range of movement was 136° in the standard design and 139° in the high flexion design, compared with a mean preoperative range of movement of 126° and 127°, respectively. In their Asian population, the pre-operative range of movement was greater than in the present series, despite which they were unable to demonstrate any advantage in using a high flexion design over the standard version. Other studies from Asian centers have failed to show an improvement in knee flexion using a high flexion design [18, 19]. This is in contrast with expectations that the Asian population will be more satisfied with the Hi-flex designs.
Menegheni et al [2007]retrospectively reviewed 511 TKAs in 370 patients fitted with posterior cruciate ligament–substituting prosthesis (NexGen Legacy, Zimmer, Warsaw, Ind) of a traditional design (not designed for high flexion) [20]. The mean follow-up was 3.7 years (range, 2-8 years). Regression analysis determined the effect of obtaining high flexion (>125°) on Knee Society, stair, function, and pain scores. Of 511 TKAs, 340 (66.5%) obtained range of motion greater than 115°, and 63 (12.3%) TKAs obtained high flexion greater than 125°. There was no difference between the patients who obtained flexion greater than 115° and those who obtained high flexion greater than 125° in Knee Society scores (P = .34) and function scores (P = .57). Patients with greater than 125° of flexion are 1.56 times more likely to demonstrate optimal stair function (P = .02). Obtaining flexion greater than 125° after TKA does not offer a benefit in overall knee function. However, obtaining a high degree of flexion appears to optimize stair climbing.
LITERATURE REVIEWS
First metaanalysis done by Gandhi et al was published in 2009 January [21]. They studied 6 studies that met with their inclusion criteria. They concluded that High-flexion implant design improves overall ROM as compared to traditional implants but offers no clinical advantage over traditional implant designs in primary knee arthroplasty.
Murphy et al [2009] performed a systematic review of published trials designed to determine if there is a significant increase in ROM or function in patients who receive a high-flexion TKA compared to those who receive a standard TKA [22]. Nine studies fitting the inclusion criteria were analysed. They concluded that there was insufficient evidence of improved range of motion or functional performance after high-flexion knee arthroplasty.
CONCLUSION
The literature produces a very conflicting picture with most of the independent studies concluding that the Hiflex design features do not translate into improved function. How a randomized study in population such as Indian population, for whom squatting and cross legged sitting is quite important, will be more indicative
REFERENCES
1. Ewald FC. The Knee Society total knee arthroplasty roentgenographic evaluation and scoring system. Clin Orthop Relat Res 1989;248:9-12.
2. Insall J, Scott WN, Ranawat CS. The total condylar knee prosthesis: A report of two hundred and twenty cases. J Bone Joint Surg Am 1979;61:173-80
3. Insall JN, Ranawat CS, Aglietti P, Shine J. A comparison of four models of total knee-replacement prostheses. J Bone Joint Surg Am 1976;58:754-65.
4. Insall J, Ranawat CS, Scott WN, Walker P. Total condylar knee replacement: Preliminary report 1976. Clin Orthop Relat Res 2001;388:3-6.
5. Ranawat CS. The patellofemoral joint in total condylar knee arthroplasty: Pros and cons based on five- to ten-year follow-up observations. Clin Orthop Relat Res 1986;205:93-9.
6. Ranawat CS, Boachie-Adjei O. Survivorship analysis and results of total condylar knee arthroplasty: Eight- to 11-year follow-up period. Clin Orthop Relat Res 1988;226:6-13.
7.Ranawat CS, Rose HA. Clinical and radiographic results of total-condylar knee arthroplasty: A 3- to 8-year follow-up. In Total- Condylar Knee Arthroplasty: Techniques, Results, and Complications. In: Ranawat CS, editor. New York: Springer; 1985. p. 140-
8. Rowe PJ, Myles CM, Walker C, Nutton R. Knee joint kinematics in gait and other functional activities measured using flexible electrogoniometry: How much knee motion is sufficient for normal daily life? Gait Posture 2000;12:143-55.
9. Mulholland SJ, Wyss UP. Activities of daily living in non-Western cultures: Range of motion requirements for hip and knee joint implants. Int J Rehabil Res 2001;24:191-8.
10. Argenson JN, Komistek RD, Mahfouz M, Walker SA, Aubaniac JM, Dennis DA. A high flexion total knee arthroplasty design replicates healthy knee motion. Clin Orthop Relat Res 2004;428:174-9.
11. Li G, Most E, Sultan PG, Schule S, Zayontz S, Park SE, et al. Knee kinematics with a high-flexion posterior stabilized total knee prosthesis: An in vitro robotic experimental investigation. J Bone Joint Surg Am 2004;86:1721-9.
12. Minoda Y, Aihara M, Sakawa A, Fukuoka S, Hayakawa K, Ohzono K. Range of motion of standard and high-flexion cruciate retaining total knee prostheses. J Arthroplasty. 2009 Aug;24(5):674-80.
13. Seon JK, Park SJ, Lee KB, Yoon TR, Kozanek M, Song EK. Range of motion in total knee arthroplasty: a prospective comparison of high-flexion and standard cruciate-retaining designs. J Bone Joint Surg Am. 2009 Mar 1;91(3):672-9.
14. Nutton RW, van der Linden ML, Rowe PJ, Gaston P, Wade FA. A prospective randomised double-blind study of functional outcome and range of flexion following total knee replacement with the NexGen standard and high flexion components. J Bone Joint Surg Br. 2008 Jan;90(1):37-42.
15. Gupta SK, Ranawat AG, Shah V, et al. The PFC Sigma RP-F TKA design for improved performance: a matched-pair study. Orthopedics 2006;29(Suppl):49-52.
16. Bin SI, Nam TS. Early results of high-flex total knee arthroplasty: comparison study at 1 year after surgery. Knee Surg Sports Traumatol Arthrosc 2007;15:350-6.
17. Kim YH, Sohn KG, Kim JS. Range of motion of standard and high-flexion posterior stabilized total knee prostheses: a prospective, randomized study. J Bone Joint Surg [Am] 2005;86-A:1470-5.
18. Seon JK, Song EK, Lee JY. Comparison of range of motion of high-flexion prosthesis and mobile bearing prosthesis in total knee arthroplasty. Orthopedics 2005;28(Suppl):1247-50.
19. Huang HT, Su JY, Wang GJ. The early result of high-flexion total knee arthroplasty: a minimum of two years of follow-up. J Arthroplasty 2005;20:674-9.
20. Meneghini RM, Pierson JL, Bagsby D, Ziemba-Davis M, Berend ME, Ritter MA. Is there a functional benefit to obtaining high flexion after total knee arthroplasty? J Arthroplasty. 2007 Sep;22(6 Suppl 2):436
21. Gandhi R, Tso P, Davey JR, Mahomed NN. High-flexion implants in primary total knee arthroplasty: a meta-analysis. Knee. 2009 Jan;16(1):14-7.
22. Murphy M, Journeaux S, Russell T. High-flexion total knee arthroplasty: a systematic review. Int Orthop. 2009 Aug;33(4):887-93.
Saturday, August 15, 2009
HIFLEX KNEE PROSTHESIS – DOES HIGH FLEXION TRANSLATES INTO IMPROVED FUNCTION
PREVIEW
Total joint replacement is the most technologically advanced solution for arthritic pain, however a search for a better functional and durable prosthesis still continues. The original Total Condylar design was very successful in terms of pain relief and durability but the average post op flexion achieved was only around 900 to 950 [1-7]. Even though this may be enough for most of the daily activities in the western world [8], Asians and particularly Indians require higher flexion for most of their daily social habits and customs [9]. In the recent times a number of additional design modifications have been introduced to achieve this goal [10, 11]. However how much impact this increase in the flexion has on patient satisfaction is yet to be determined.
RECENT LITERATURE
Minoda et al [2009] analysed range of motion of standard and hi-flex cruciate retaining prosthesis prospectively [12]. They had 89 knees with standard and 87 knees with high flexion CR total knee prostheses [both Next Gen brands]. Differences in age, gender, diagnosis, preoperative ROM of the knee, and Knee Society Score between the 2 groups were not statistically significant. At 12-month follow-up, average ROM was 112.0° ± 12.6° for standard, and 115.3° ± 13.4° for high-flexion CR prosthesis (P = .101). They found no significant differences between groups with regard to ROM, clinical, or radiographic parameters.
Seon et al [2009] analysed 100 knees with 50 knees in each category of Hi-flex and standard total knee prosthesis [13]. At the time of the final follow-up, the average maximal non-weight-bearing flexion was 135.3⁰ for the knees in the high-flexion group and 134.3⁰ for the knees in the standard group; the difference was not significant. Moreover, no significant difference was found between the groups in terms of weight-bearing flexion (124.8⁰ in the high-flexion group and 123.7⁰ in the standard group) and the number of knees that allowed kneeling and sitting cross-legged. The average Hospital for Special Surgery knee score was 94.4 points in the high-flexion group and 92.4 points in the standard group; the difference was not significant. The Western Ontario and McMaster Universities Osteoarthritis Index scores also showed no significant difference between the groups. Thus no functional difference was noted in two groups.
Nutton et al [2008] performed prospective randomised comparison of the functional outcome in patients receiving either a NexGen LPS-Flex or the standard design [14]. The study included total of 56 patients, half of whom received Hi-flex and standard knee prosthesis each. They found that there was no significant difference in outcome, including the maximum knee flexion, between patients receiving the standard and high flexion designs of this implant.
Gupta et al [2006] reported a significant improvement in the post-operative range of movement using a high flexion rotating platform design when compared with a standard design of rotating-platform TKR [15]. Similarly, Bin and Nam [2007] found a significant improvement in knee flexion at one year after operation in patients receiving a high flexion design compared with a standard knee replacement, particularly in patients with a pre-operative range of flexion of less than 90° [16].
Kim, Sohn and Kim [2005] were unable to show a significant improvement in knee flexion using a NexGen LPS-Flex knee replacement [17]. In their study, the standard design was used in one knee and high flexion prosthesis in the other. After a mean of 2.1 years the mean range of movement was 136° in the standard design and 139° in the high flexion design, compared with a mean preoperative range of movement of 126° and 127°, respectively. In their Asian population, the pre-operative range of movement was greater than in the present series, despite which they were unable to demonstrate any advantage in using a high flexion design over the standard version. Other studies from Asian centers have failed to show an improvement in knee flexion using a high flexion design [18, 19]. This is in contrast with expectations that the Asian population will be more satisfied with the Hi-flex designs.
Lastly Menegheni et al [2007]retrospectively reviewed 511 TKAs in 370 patients fitted with posterior cruciate ligament–substituting prosthesis (NexGen Legacy, Zimmer, Warsaw, Ind) of a traditional design (not designed for high flexion) [20]. The mean follow-up was 3.7 years (range, 2-8 years). Regression analysis determined the effect of obtaining high flexion (>125°) on Knee Society, stair, function, and pain scores. Of 511 TKAs, 340 (66.5%) obtained range of motion greater than 115°, and 63 (12.3%) TKAs obtained high flexion greater than 125°. There was no difference between the patients who obtained flexion greater than 115° and those who obtained high flexion greater than 125° in Knee Society scores (P = .34) and function scores (P = .57). Patients with greater than 125° of flexion are 1.56 times more likely to demonstrate optimal stair function (P = .02). Obtaining flexion greater than 125° after TKA does not offer a benefit in overall knee function. However, obtaining a high degree of flexion appears to optimize stair climbing.
LITERATURE REVIEWS
First metaanalysis done by Gandhi et al was published in 2009 January [21]. They studied 6 studies that met with their inclusion criteria. They concluded that High-flexion implant design improves overall ROM as compared to traditional implants but offers no clinical advantage over traditional implant designs in primary knee arthroplasty.
Murphy et al [2009] performed a systematic review of published trials designed to determine if there is a significant increase in ROM or function in patients who receive a high-flexion TKA compared to those who receive a standard TKA [22]. Nine studies fitting the inclusion criteria were analysed. They concluded that there was insufficient evidence of improved range of motion or functional performance after high-flexion knee arthroplasty.
CONCLUSION
The literature produces a very conflicting picture with most of the independent studies concluding that the Hiflex design features do not translate into improved function. How a randomized study in population such as Indian population, for whom squatting and cross legged sitting is quite important, will be more indicative
REFERENCES
1. Ewald FC. The Knee Society total knee arthroplasty roentgenographic evaluation and scoring system. Clin Orthop Relat Res 1989;248:9-12.
2. Insall J, Scott WN, Ranawat CS. The total condylar knee prosthesis: A report of two hundred and twenty cases. J Bone Joint Surg Am 1979;61:173-80
3. Insall JN, Ranawat CS, Aglietti P, Shine J. A comparison of four models of total knee-replacement prostheses. J Bone Joint Surg Am 1976;58:754-65.
4. Insall J, Ranawat CS, Scott WN, Walker P. Total condylar knee replacement: Preliminary report 1976. Clin Orthop Relat Res 2001;388:3-6.
5. Ranawat CS. The patellofemoral joint in total condylar knee arthroplasty: Pros and cons based on five- to ten-year follow-up observations. Clin Orthop Relat Res 1986;205:93-9.
6. Ranawat CS, Boachie-Adjei O. Survivorship analysis and results of total condylar knee arthroplasty: Eight- to 11-year follow-up period. Clin Orthop Relat Res 1988;226:6-13.
7.Ranawat CS, Rose HA. Clinical and radiographic results of total-condylar knee arthroplasty: A 3- to 8-year follow-up. In Total- Condylar Knee Arthroplasty: Techniques, Results, and Complications. In: Ranawat CS, editor. New York: Springer; 1985. p. 140-
8. Rowe PJ, Myles CM, Walker C, Nutton R. Knee joint kinematics in gait and other functional activities measured using flexible electrogoniometry: How much knee motion is sufficient for normal daily life? Gait Posture 2000;12:143-55.
9. Mulholland SJ, Wyss UP. Activities of daily living in non-Western cultures: Range of motion requirements for hip and knee joint implants. Int J Rehabil Res 2001;24:191-8.
10. Argenson JN, Komistek RD, Mahfouz M, Walker SA, Aubaniac JM, Dennis DA. A high flexion total knee arthroplasty design replicates healthy knee motion. Clin Orthop Relat Res 2004;428:174-9.
11. Li G, Most E, Sultan PG, Schule S, Zayontz S, Park SE, et al. Knee kinematics with a high-flexion posterior stabilized total knee prosthesis: An in vitro robotic experimental investigation. J Bone Joint Surg Am 2004;86:1721-9.
12. Minoda Y, Aihara M, Sakawa A, Fukuoka S, Hayakawa K, Ohzono K. Range of motion of standard and high-flexion cruciate retaining total knee prostheses. J Arthroplasty. 2009 Aug;24(5):674-80.
13. Seon JK, Park SJ, Lee KB, Yoon TR, Kozanek M, Song EK. Range of motion in total knee arthroplasty: a prospective comparison of high-flexion and standard cruciate-retaining designs. J Bone Joint Surg Am. 2009 Mar 1;91(3):672-9.
14. Nutton RW, van der Linden ML, Rowe PJ, Gaston P, Wade FA. A prospective randomised double-blind study of functional outcome and range of flexion following total knee replacement with the NexGen standard and high flexion components. J Bone Joint Surg Br. 2008 Jan;90(1):37-42.
15. Gupta SK, Ranawat AG, Shah V, et al. The PFC Sigma RP-F TKA design for improved performance: a matched-pair study. Orthopedics 2006;29(Suppl):49-52.
16. Bin SI, Nam TS. Early results of high-flex total knee arthroplasty: comparison study at 1 year after surgery. Knee Surg Sports Traumatol Arthrosc 2007;15:350-6.
17. Kim YH, Sohn KG, Kim JS. Range of motion of standard and high-flexion posterior stabilized total knee prostheses: a prospective, randomized study. J Bone Joint Surg [Am] 2005;86-A:1470-5.
18. Seon JK, Song EK, Lee JY. Comparison of range of motion of high-flexion prosthesis and mobile bearing prosthesis in total knee arthroplasty. Orthopedics 2005;28(Suppl):1247-50.
19. Huang HT, Su JY, Wang GJ. The early result of high-flexion total knee arthroplasty: a minimum of two years of follow-up. J Arthroplasty 2005;20:674-9.
20. Meneghini RM, Pierson JL, Bagsby D, Ziemba-Davis M, Berend ME, Ritter MA. Is there a functional benefit to obtaining high flexion after total knee arthroplasty? J Arthroplasty. 2007 Sep;22(6 Suppl 2):436
21. Gandhi R, Tso P, Davey JR, Mahomed NN. High-flexion implants in primary total knee arthroplasty: a meta-analysis. Knee. 2009 Jan;16(1):14-7.
22. Murphy M, Journeaux S, Russell T. High-flexion total knee arthroplasty: a systematic review. Int Orthop. 2009 Aug;33(4):887-93.
PREVIEW
Total joint replacement is the most technologically advanced solution for arthritic pain, however a search for a better functional and durable prosthesis still continues. The original Total Condylar design was very successful in terms of pain relief and durability but the average post op flexion achieved was only around 900 to 950 [1-7]. Even though this may be enough for most of the daily activities in the western world [8], Asians and particularly Indians require higher flexion for most of their daily social habits and customs [9]. In the recent times a number of additional design modifications have been introduced to achieve this goal [10, 11]. However how much impact this increase in the flexion has on patient satisfaction is yet to be determined.
RECENT LITERATURE
Minoda et al [2009] analysed range of motion of standard and hi-flex cruciate retaining prosthesis prospectively [12]. They had 89 knees with standard and 87 knees with high flexion CR total knee prostheses [both Next Gen brands]. Differences in age, gender, diagnosis, preoperative ROM of the knee, and Knee Society Score between the 2 groups were not statistically significant. At 12-month follow-up, average ROM was 112.0° ± 12.6° for standard, and 115.3° ± 13.4° for high-flexion CR prosthesis (P = .101). They found no significant differences between groups with regard to ROM, clinical, or radiographic parameters.
Seon et al [2009] analysed 100 knees with 50 knees in each category of Hi-flex and standard total knee prosthesis [13]. At the time of the final follow-up, the average maximal non-weight-bearing flexion was 135.3⁰ for the knees in the high-flexion group and 134.3⁰ for the knees in the standard group; the difference was not significant. Moreover, no significant difference was found between the groups in terms of weight-bearing flexion (124.8⁰ in the high-flexion group and 123.7⁰ in the standard group) and the number of knees that allowed kneeling and sitting cross-legged. The average Hospital for Special Surgery knee score was 94.4 points in the high-flexion group and 92.4 points in the standard group; the difference was not significant. The Western Ontario and McMaster Universities Osteoarthritis Index scores also showed no significant difference between the groups. Thus no functional difference was noted in two groups.
Nutton et al [2008] performed prospective randomised comparison of the functional outcome in patients receiving either a NexGen LPS-Flex or the standard design [14]. The study included total of 56 patients, half of whom received Hi-flex and standard knee prosthesis each. They found that there was no significant difference in outcome, including the maximum knee flexion, between patients receiving the standard and high flexion designs of this implant.
Gupta et al [2006] reported a significant improvement in the post-operative range of movement using a high flexion rotating platform design when compared with a standard design of rotating-platform TKR [15]. Similarly, Bin and Nam [2007] found a significant improvement in knee flexion at one year after operation in patients receiving a high flexion design compared with a standard knee replacement, particularly in patients with a pre-operative range of flexion of less than 90° [16].
Kim, Sohn and Kim [2005] were unable to show a significant improvement in knee flexion using a NexGen LPS-Flex knee replacement [17]. In their study, the standard design was used in one knee and high flexion prosthesis in the other. After a mean of 2.1 years the mean range of movement was 136° in the standard design and 139° in the high flexion design, compared with a mean preoperative range of movement of 126° and 127°, respectively. In their Asian population, the pre-operative range of movement was greater than in the present series, despite which they were unable to demonstrate any advantage in using a high flexion design over the standard version. Other studies from Asian centers have failed to show an improvement in knee flexion using a high flexion design [18, 19]. This is in contrast with expectations that the Asian population will be more satisfied with the Hi-flex designs.
Lastly Menegheni et al [2007]retrospectively reviewed 511 TKAs in 370 patients fitted with posterior cruciate ligament–substituting prosthesis (NexGen Legacy, Zimmer, Warsaw, Ind) of a traditional design (not designed for high flexion) [20]. The mean follow-up was 3.7 years (range, 2-8 years). Regression analysis determined the effect of obtaining high flexion (>125°) on Knee Society, stair, function, and pain scores. Of 511 TKAs, 340 (66.5%) obtained range of motion greater than 115°, and 63 (12.3%) TKAs obtained high flexion greater than 125°. There was no difference between the patients who obtained flexion greater than 115° and those who obtained high flexion greater than 125° in Knee Society scores (P = .34) and function scores (P = .57). Patients with greater than 125° of flexion are 1.56 times more likely to demonstrate optimal stair function (P = .02). Obtaining flexion greater than 125° after TKA does not offer a benefit in overall knee function. However, obtaining a high degree of flexion appears to optimize stair climbing.
LITERATURE REVIEWS
First metaanalysis done by Gandhi et al was published in 2009 January [21]. They studied 6 studies that met with their inclusion criteria. They concluded that High-flexion implant design improves overall ROM as compared to traditional implants but offers no clinical advantage over traditional implant designs in primary knee arthroplasty.
Murphy et al [2009] performed a systematic review of published trials designed to determine if there is a significant increase in ROM or function in patients who receive a high-flexion TKA compared to those who receive a standard TKA [22]. Nine studies fitting the inclusion criteria were analysed. They concluded that there was insufficient evidence of improved range of motion or functional performance after high-flexion knee arthroplasty.
CONCLUSION
The literature produces a very conflicting picture with most of the independent studies concluding that the Hiflex design features do not translate into improved function. How a randomized study in population such as Indian population, for whom squatting and cross legged sitting is quite important, will be more indicative
REFERENCES
1. Ewald FC. The Knee Society total knee arthroplasty roentgenographic evaluation and scoring system. Clin Orthop Relat Res 1989;248:9-12.
2. Insall J, Scott WN, Ranawat CS. The total condylar knee prosthesis: A report of two hundred and twenty cases. J Bone Joint Surg Am 1979;61:173-80
3. Insall JN, Ranawat CS, Aglietti P, Shine J. A comparison of four models of total knee-replacement prostheses. J Bone Joint Surg Am 1976;58:754-65.
4. Insall J, Ranawat CS, Scott WN, Walker P. Total condylar knee replacement: Preliminary report 1976. Clin Orthop Relat Res 2001;388:3-6.
5. Ranawat CS. The patellofemoral joint in total condylar knee arthroplasty: Pros and cons based on five- to ten-year follow-up observations. Clin Orthop Relat Res 1986;205:93-9.
6. Ranawat CS, Boachie-Adjei O. Survivorship analysis and results of total condylar knee arthroplasty: Eight- to 11-year follow-up period. Clin Orthop Relat Res 1988;226:6-13.
7.Ranawat CS, Rose HA. Clinical and radiographic results of total-condylar knee arthroplasty: A 3- to 8-year follow-up. In Total- Condylar Knee Arthroplasty: Techniques, Results, and Complications. In: Ranawat CS, editor. New York: Springer; 1985. p. 140-
8. Rowe PJ, Myles CM, Walker C, Nutton R. Knee joint kinematics in gait and other functional activities measured using flexible electrogoniometry: How much knee motion is sufficient for normal daily life? Gait Posture 2000;12:143-55.
9. Mulholland SJ, Wyss UP. Activities of daily living in non-Western cultures: Range of motion requirements for hip and knee joint implants. Int J Rehabil Res 2001;24:191-8.
10. Argenson JN, Komistek RD, Mahfouz M, Walker SA, Aubaniac JM, Dennis DA. A high flexion total knee arthroplasty design replicates healthy knee motion. Clin Orthop Relat Res 2004;428:174-9.
11. Li G, Most E, Sultan PG, Schule S, Zayontz S, Park SE, et al. Knee kinematics with a high-flexion posterior stabilized total knee prosthesis: An in vitro robotic experimental investigation. J Bone Joint Surg Am 2004;86:1721-9.
12. Minoda Y, Aihara M, Sakawa A, Fukuoka S, Hayakawa K, Ohzono K. Range of motion of standard and high-flexion cruciate retaining total knee prostheses. J Arthroplasty. 2009 Aug;24(5):674-80.
13. Seon JK, Park SJ, Lee KB, Yoon TR, Kozanek M, Song EK. Range of motion in total knee arthroplasty: a prospective comparison of high-flexion and standard cruciate-retaining designs. J Bone Joint Surg Am. 2009 Mar 1;91(3):672-9.
14. Nutton RW, van der Linden ML, Rowe PJ, Gaston P, Wade FA. A prospective randomised double-blind study of functional outcome and range of flexion following total knee replacement with the NexGen standard and high flexion components. J Bone Joint Surg Br. 2008 Jan;90(1):37-42.
15. Gupta SK, Ranawat AG, Shah V, et al. The PFC Sigma RP-F TKA design for improved performance: a matched-pair study. Orthopedics 2006;29(Suppl):49-52.
16. Bin SI, Nam TS. Early results of high-flex total knee arthroplasty: comparison study at 1 year after surgery. Knee Surg Sports Traumatol Arthrosc 2007;15:350-6.
17. Kim YH, Sohn KG, Kim JS. Range of motion of standard and high-flexion posterior stabilized total knee prostheses: a prospective, randomized study. J Bone Joint Surg [Am] 2005;86-A:1470-5.
18. Seon JK, Song EK, Lee JY. Comparison of range of motion of high-flexion prosthesis and mobile bearing prosthesis in total knee arthroplasty. Orthopedics 2005;28(Suppl):1247-50.
19. Huang HT, Su JY, Wang GJ. The early result of high-flexion total knee arthroplasty: a minimum of two years of follow-up. J Arthroplasty 2005;20:674-9.
20. Meneghini RM, Pierson JL, Bagsby D, Ziemba-Davis M, Berend ME, Ritter MA. Is there a functional benefit to obtaining high flexion after total knee arthroplasty? J Arthroplasty. 2007 Sep;22(6 Suppl 2):436
21. Gandhi R, Tso P, Davey JR, Mahomed NN. High-flexion implants in primary total knee arthroplasty: a meta-analysis. Knee. 2009 Jan;16(1):14-7.
22. Murphy M, Journeaux S, Russell T. High-flexion total knee arthroplasty: a systematic review. Int Orthop. 2009 Aug;33(4):887-93.
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