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.
Sunday, June 14, 2009
BASIC SCIENCES- Artificial cartilage in Joint Replacement
NEW AVENEUS IN JOINT REPLACEMENT – THE CUTTING EDGE
What is the best alternative to joint cartilage…. Metal on polyethylene, metal on metal, ceramic on ceramic, metal on ceramic??
How about artificial cartilage!!
A search for new options has begun in early 21st century to have a more natural and biological bearing surface having better durability than the present ones. Present bearing surfaces still have problems of debris and osteolysis although recent advances have surely decreased the incidence [1].
A new direction was unveiled when a Japanese team at Hokkaido University in Japan discovered what is called a double network hydrogels [2]. Hydrogels are materials that are 80% - 90% water held in a polymer network. These can be easily broken apart like gelatin. The Japanese team added a second polymer to the gel and to their surprise the new material called double network gels had incredible strength that rivaled natural cartilage [3,4,5]. The gel had the pliancy of gelatin but would not break even when deformed more than 1000%.
Work using the national institute of standard and technology neutron scattering technology is exploring the structure of the gel to discover the molecular level toughening mechanism, to allow for more precise designing of next generation of these hydrogels being both rigid and tough at the same time. The key feature of these interpenetrating gels is a strong but easily compressed fibrous network, which is filled with a weak but viscous and difficult-to compress “gel” that traps water in the fiber matrix. This feature is akin to the structure of cartilage, ligament, tendon, and other soft connective tissue. As a result of the similarity between these manufactured gels and natural cartilage, they are sometimes called "Biomimetic gels"—that is, of a structure that mimics the natural tissue [1]. Researchers hope to design a synthetic cartilage that could endure year after year under the rigors of body before needing to be replaced. However there is still much time required to explore this option and to study practicality of in-vivo use.
A second interesting research comes from field of nanotechnology. Nano materials are typically between 0.1 and 100 Nanometers in size with 1 nm being equivalent to 1 billionth of a meter. This is a scale at which the basic functions of the biological world operate. Increased surface area and weird quantum effects at atomic scale provide substances with unusual physical and chemical properties. Considering that the healthy human joint cartilage surface is covered with a nanometer-scaled phospholipid layer [6], grafting a phospholipid-like layer on the liner surface may realize an ideal lubricity resembling the physiological joint surface.Chen et al [7] have developed biocompatible molecular nanobrushes that slide past each other with friction coefficients that match those of cartilage. In some respects, they perform even better: the brushes remain highly effective even at pressures of 7.5 megapascals. Cartilage performs well only up to around 5 megapascals – a natural limit because joint pressure only rarely exceeds that level.
Each 60-nanometre-long brush filament has a polymer backbone from which small molecular groups stick out. Those synthetic groups are very similar to the lipids found in cell membranes and although they're neutral overall, they are positively charged at one end and negatively charged at the other. In a watery environment, each of these molecular groups attracts up to 25 water molecules through electrostatic forces, so the filament as a whole develops a slick watery sheath. These sheathes ensure that the brushes are lubricated as they rub past each other, even when firmly pressed together to mimic the pressures at bone joints. This extreme lubrication is attributed primarily to the strong hydration of the phosphorylcholine-like monomers that make up the robustly attached brushes, and may have relevance to a wide range of human-made aqueous lubrication situations.
Jennifer Elisseeff, a professor of engineering and orthopaedic surgery at Johns Hopkins University in Baltimore, who was not involved with the study, says the new material is an "important step forward" for joint lubrication studies.
A team led by Hiroshi Kawaguchi at the University of Tokyo in Japan has already tried earlier versions of these nanobrushes to coat the polyethylene surfaces of artificial joints 2004 [8]. The team found that the hydrophilic molecules creating very effective lubricating water layer in the artificial joints. Tests in a hip-joint simulator found that the coated polyethylene showed an astonishing 40 times less wear than the uncoated version. Later in 2006 the team investigated the nanobrushes for clinical application [9]. They investigated the stability of the 2-methacryloyloxyethyl phosphorylcholine grafting during sterilization and the wear resistance of the sterilized liner during longer loading comparable to clinical usage. Radiographic spectroscopy confirmed the stability of the 2-methacryloyloxyethyl phosphorylcholine polymer on the liner surface after the gamma irradiation. They used a hip wear simulator up to 1 x 10(7) cycles to test sterilized cross-linked polyethylene liners with and without 2-methacryloyloxyethyl phosphorylcholine grafting. The 2-methacryloyloxyethyl phosphorylcholine grafting markedly decreased the friction, the production of wear particles, and the wear of the liner surface.
In 2009 the same Japanese team has used a better version of nanobrushes called poly(2 methacryloyloxyethyl phosphorylcholine (MPC)) (PMPC) to coat the joints [10]. They studied the effect of cross linking the polyethylene with or without PMPC coating and also studied PMPC coated Co–Cr alloy and alumina ceramic femoral heads in the hip joint simulator. They concluded that the PMPC grafting for obtaining super-lubrication on the PE liner is more efficient than the cross-linking of the PE liner and the change of the femoral head materials for extending longevity of artificial hip joints. The development of this nanotechnology in the biomaterials science would improve the quality of care of patients having joint replacement and have a substantial public health impact. A large-scale clinical trial is now underway to further study this HORIZON.
References
1. Muehleman C, Connor D, Fyhrie DP, Marsh JL, Anderson D. On the Horizon From the ORS. J Am Acad Orthop Surg. 2009 Jul;17(7):473-6.
2. http://www.arthritis.org/gel-artificial-cartilage.php.
3.Yasuda K, Ping Gong J, Katsuyama Y, et al: Biomechanical properties of hightoughness double network hydrogels. Biomaterials 2005;26:4468-4475.
4. Yang-Ho N, Katsuyama Y, Kuwabara R, et al: Toughening of hydrogels with double network structure. e-Journal of SurfaceScience and Nanotechnology 2005;3:8-11.
5. Azuma C, Yasuda K, Tanabe Y, et al: Biodegradation of high-toughness double network hydrogels as potential materials for artificial cartilage. J Biomed Mater Res A 2007;81:373-380. Medline
6. Kirk TB, Wilson AS, Stachowiak GW. The morphology and composition of the superficial zone of mammalian articular cartilage. J Orthopaedic Rheumatol 1993;6:21–8.
7. Chen M, Briscoe WH, Armes SP, Klein J. Lubrication at physiological pressures by polyzwitterionic brushes. Science. 2009 Mar 27;323(5922):1698-701.
8. Moro T, Takatori Y, Ishihara K, Konno T, Takigawa Y, Matsushita T, Chung UI, Nakamura K, Kawaguchi H. Surface grafting of artificial joints with a biocompatible polymer for preventing periprosthetic osteolysis. Nature Materials. 2004 Nov;3(11):829-36
9. Moro T, Takatori Y, Ishihara K, Nakamura K, Kawaguchi H. 2006 Frank Stinchfield Award: grafting of biocompatible polymer for longevity of artificial hip joints. Clin Orthop Relat Res. 2006 Dec;453:58-63.
10. Moro T, Kawaguchi H, Ishihara K, Kyomoto M, Karita T, Ito H, Nakamura K, Takatori Y. Wear resistance of artificial hip joints with poly(2-methacryloyloxyethyl phosphorylcholine) grafted polyethylene: comparisons with the effect of polyethylene cross-linking and ceramic femoral heads. Biomaterials. 2009 Jun;30(16):2995-3001
Saturday, June 13, 2009
SPINE- Bone Morphogenic Proteins and Spinal Fusion
Bone Morphogenic Proteins and Spinal Fusion:
Written By - Dr Prakash Nayak, MS Ortho
Editor - Dr Ashok Shyam, MS Ortho
Research into Bone morphogenetic protein, or BMP, has seen a flurry of events in last decade. They seem to provide a better way to achieve spinal fusion with more success and less complications. An up-to-date review of role of BMPs in spinal fusion is reported below
SPINAL FUSION.....
Spinal fusion has always been a challenge. The success of this procedure is limited by morbidity from iliac crest bone graft harvest and a non-union rate that ranges from 10% to 40% [1,2]. This is due to the high forces borne by the spine and the instability rendered by surgery. Advances in spinal instrumentation have improved spinal fusion rates but not eliminated non union or spinal pseudoarthroses which often affects final surgical outcomes in 10% to 15% [2,3]. Traditionally autografts and allografts have been the mainstay for spinal fusions. The limited availability of autograft, significant morbidity (reported to be as high as 30%) and the variability in fusion success rate remain issues [4,5]. The osteoinductive and limited osteoconductive capacity of Allograft (mineralized or demineralised) is highly variable [6,7]. Various modalities used for enhancing fusion have included electrical stimulation, low intensity ultrasound and demineralised bone matrix (DBM).These have not been effective and their viability as a good alternative is questionable [8,9]. BMPs seem to answer all these difficult questions
UNVEILING OF A NEW HORIZON
The unique ability of devitalized bone to induce a cellular response resulting in new bone was observed and researched extensively by an orthopedic surgeon, Dr. Marshall Urist in the 1960s [10,11]. He subsequently extracted these organic components of bone using chaotropic agents, and named them “bone morphogenetic protein.”
In the 1980s, the proteins were individually identified and reproduced.
After numerous animal studies using BMP, it was used for the first time in 1997 in a clinical trial of patients undergoing spinal fusion. 10 of the 11 patients enrolled in the study had successful fusions within 3 months of surgery, all without the unpleasant side effects of bone grafting.
HOW DO THEY WORK
Bone morphogenic proteins (BMPs) are a heterogenic group of transforming growth factors (TGF). Recently up to 20 subtypes have been identified, their genes sequenced and cloned. Many have significant osteogenic effects and promote both intramembranous and endochondral ossification. BMPs work by stimulating mesenchymal stem cells through a complex system of second messengers, which are yet to be identified. Bone formed by BMPs is histologically and biomechanically identical to normal bone and undergoes normal fracture healing and remodelling10. Over a range of concentrations, rhBMP-2 results in endochondral bone formation including mesenchymal cell infiltration, differentiation of the cells into chondrocytes, removal of the cartilage, formation of bone, population of the bone with bone marrow elements, and ultimately normal remodeling of the bone [12].
MODE OF APPLICATION
Presently the BMPs are commercially produced by Recombinant deoxyribonucleic acid technology offering unlimited supply and substantial control over purity and reproducible activity [13]. One important problem is to find an efficient delivery system for BMPs. The ideal carrier system will retain and release the BMP in a controlled fashion, be biocompatible, not interfere with normal bony healing, be porous to promote osteoconductivity, be biomechanically strong, be easy to apply, and be easy to manufacture. Buffer delivered factors do not work in human beings as sufficient local retention of factors does not take place [14].Current delivery systems include following
1 calcium phosphate cements have been used as both injectable and implantable formulations of delivery.
2. Demineralised bone matrix, one of the first collagen-based carriers evaluated for BMP delivery had the major disadvantages of potential immunogenicity, risk of disease transmission15.
3.The synthetic polymers eliminate the possibility of disease transmission associated with natural polymers [16].
4.Newer Viral vector systems deliver the cDNA of BMPs for osteogenic factors to cells at the site of orthopedic repair [17,18].
The combination of polyetheretherketone (PEEK) cage and rhBMP-2 has evolved as a front runner. PEEK cages are reported to be the ideal spacers, because they share the same modulus of elasticity as bone [19,20]. They are nonresorbable and elicit minimal cellular response when placed in vitro and in vivo [21].
COMMERCIAL ASPECTS
Two BMP products are commercially available for clinical use, BMP-2 (INFUSE,
Medtronic, Memphis, Tennessee) and BMP-7 (OP-1 Putty, Stryker, Kalamazoo,
Michigan). BMP-2 is approved for anterior lumbar interbody fusion in skeletally mature patients and BMP-7 received a humanitarian use device approval in 2003 for revision intertransverse lumbar fusion in compromised patients [22],without the need for autologous graft. Although BMP is FDA approved for use only in the lumbar spine, recent work has focused on applications at other spine levels, including use in cervical interbody fusion [23]. The decision to use BMP to increase bony-fusion rates may decrease the need for a revision fusion procedure; therefore, cost-effectiveness analyses must be include d in longitudinal outcomes analysis .The preliminary data shows that from a payer perspective, the upfront price of BMP is likely to be entirely offset by reductions in pain, complications of autograft and fusion failures. Additionally, by eliminating the need to harvest the autograft, anaesthesia time and surgeons’ fees would be offset [24]. Less obvious cost offsets include decreased blood loss and obviated treatment of donor site complications as well as potentially decreased transfusion requirements and shortened hospital length of stay.
PRESENT SCENARIO
Specific guidelines for rhBMP-2 and rhBMP-7 use are lacking because of the limited availability of randomized controlled clinical trials and its diverse use in many spinal applications. Mechanisms of delivery, carrier type, graft position, surgical location, and variations in BMP concentration may differ from one surgery to the next. Adverse events linked to either rhBMP-2 or rhBMP-7 use include ectopic bone formation, bone resorption or remodelling at the graft site, hematoma, neck swelling, and painful seroma [25]. The cascade of major phases involved in the healing of bone include an initial acute inflammatory response, a resorptive phase, subperiosteal and endosteal proliferation, bone formation, consolidation, and finally remodeling by osteoclast and osteoblast activity. In the process of fusion, rhBMP-2 causes a phase of increased resorption. During this period the cage is prone to migration and subsidence may occur [26].Neck swelling and hematoma have been significantly associated with the off label use of BMP in cervical spine surgeries. Other potential theoretical concerns include carcinogenicity and teratogenic effects.
HOW SAFE ARE THEY
FDA Public Health Notification- issued July 2008 [27]
Regulatory Status of rhBMP
FDA has approved the use of two rhBMPs for well-defined medical conditions in limited patient
populations:
rhBMP-2 (contained in InFuse Bone Graft) has received premarket approval for fusion of
the lumbar spine in skeletally mature patients with degenerative disc disease (DDD) at
one level from L2-S1 and for healing of acute, open tibial shaft fractures stabilized with an
IM nail and treated within 14 days of the initial injury. rhBMP-2 is also approved for
certain oral and maxillofacial uses.
rhBMP-7 (referred to as OP-1 and contained in OP-1 Implant and OP-1 Putty) has
received humanitarian device exemption approval as an alternative to autograft in
recalcitrant long bone nonunions where use of autograft is unfeasible and alternative
treatments have failed. It is also approved as an alternative to autograft in compromised
patients requiring revision posterolateral (intertransverse) lumbar spinal fusion for whom
autologous bone and bone marrow harvest are not feasible or are not expected to
promote fusion. Examples of compromising factors include osteoporosis, smoking and
diabetes.
Both rhBMPs are contraindicated for all uses in patients who are skeletally immature (<18 size="5">Future prospects
A randomised control trial is needed to outline the role of BMPs in spinal fusion and to study the complications and financial aspects of this modality of treatment
References:
1. Bridwell KH, Sedgewick TA, O’Brien MF, et al. The role of fusion and instrumentation in the treatment of degenerative spondylolisthesis with spinal stenosis. J Spinal Disord 1993;6:461–72.
2. McGuire RA, Amundson GM. The use of primary internal fixation in spondylolisthesis. Spine 1993;18:1662–72.
3. West JL III, Bradford DS, Ogilvie JW. Results of spinal arthrodesis with pedicle screw plate fixation. J Bone Joint Surg Am 1991;73:1179–84.
4. Arrington ED, Smith WJ, Chambers HG, et al. Complications of iliac crest bone graft harvesting. Clin Orthop 1996;329:300–9.
5.Banwart JC, Asher MA, Hassanein RS. Iliac crest bone graft harvest donor site morbidity: A statistical evaluation. Spine 1995;20:1055–60.
6.Boden SD. Bioactive factors for bone tissue engineering. Clin Orthop 1999;367(Suppl):S84–94.
7.Boden SD, Sumner DR. Biologic factors affecting spinal fusion and bone regeneration. Spine 1995;20:102S–12S
8. Meril AJ. Direct current stimulation of allograft in anterior and posterior lumbar interbody fusions. Spine 1994;19:2393–8.
9.Mooney V. A randomized double-blind prospective study of the efficacy of pulsed electromagnetic fields for interbody lumbar fusions. Spine 1990;15:708–12.
10.Urist MR. Bone. Formation by autoinduction. Science 1965;150:893–9.
11.Urist MR, Mikulski A, Lietze A. Solubilized and insolubilized bone morphogenetic protein. Proc Natl Acad Sci USA 1979;76:1828–32.
12. Scott D. Boden:Overview of the Biology of Lumbar Spine Fusion and Principles for Selecting a Bone Graft Substitute;SPINE Volume 27, Number 16S, pp S26–S31.
13.McKay B, Sandhu HS. Use of recombinant human bone morphogenetic protein-2 in spinal fusion applications. Spine (Phila Pa 1976). 2002 Aug 15;27(16 Suppl 1):S66-85.
14.Howard Seeherman, John Wozney, Rebecca Li:Bone Morphogenetic Protein Delivery Systems:SPINE Volume 27, Number 16S, pp S16–S23
15.Jarcho M. Calcium phosphate ceramics as hard tissue prosthetics. Clin Orthop 1981;157:259–78.
16.Hollinger JO, Brekke J, Gruskin E, et al. Role of bone substitutes. Clin Orthop 1996;324:55–65.
17.Franceschi RT, Wang D, Krebsbach PH, et al. Gene therapy for bone formation: In vitro and in vivo osteogenic activity of an adenovirus expressing BMP7. J Cell Biochem 2000;78:476–86.
18.Helm GA, Alden TD, Sheehan JP, et al. Bone morphogenetic proteins and bone morphogenetic protein gene therapy in neurological surgery: A review. Neurosurgery 2000;46:1213–22.
19.Matge G. Cervical cage fusion with 5 different implants: 250 cases. Acta Neurochir. 2002;144:539–550.
20. Brantigan JW, Steffee AD. A carbon fiber implant to aid interbody lumbar fusion. Two year clinical results in the first 26 patients. Spine. 1993;18:2106–2117.
21. Boakye M, Mummaneni PV, Garrett M, et al. Anterior cervical discectomy and fusion involving a polyetheretherketone spacer and bone morphogenetic protein. J Neurosurg Spine. 2005;2:521–525.
22. US Food and Drug Administration. OP-1 Putty -H020008 [Web page].
23.Vaccaro AR, Whang PG, Patel T, et al. The safety and efficacy of OP-1 (rhBMP-7) as a replacement for iliac crest autograft for posterolateral lumbar arthrodesis: minimum 4-year follow-up of a pilot study. Spine J. 2008;8(3):457-465.
24.Ackerman SJ, Mafilios MS, Polly DW Jr: Economic evaluation of bone morphogenetic protein versus autogenous iliac crest bone graft in single-level anterior lumbar fusion: an evidence-based modeling approach:Spine (Phila Pa 1976). 2002 Aug 15;27(16 Suppl 1):S94-9.
25.Benglis D, Wang MY, Levi AD.A Comprehensive review of the safety profile of Bone Morphogenic Protein in Spine surgery:Neurosurgery 62[ONS Suppl 2]:ONS423–ONS431, 2008.
26.Cahill, Kevin S. MD, PhD, MPH; Chi, John H. MD, MPH; Day, Arthur MD; Claus, Elizabeth B. MD, PhD. Prevalence, Complications, and Hospital Charges Associated With Use of Bone-Morphogenetic Proteins in Spinal Fusion Procedures. JAMA. 302(1):58-66, July 1, 2009.
27. FDA Public Health Notification. Life-threatening complications associate with recombinant human bone morphogenetic protein in cervical spine fusion. Available at: http://www.personalinjurylawyeramerica/. com/pdf/20080701-fda-infuse.pdf. Accessed July 1, 2008
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