Comparison Between Standard and High-Flexion Posterior-Stabilized Rotating-Platform Mobile-Bearing Total Knee Arthroplasties
A Randomized Controlled Study
Won Chul Choi, MD1, Sahnghoon Lee, MD, PhD1, Sang Cheol Seong, MD, PhD1, Jong Hun Jung, MD1 and Myung Chul Lee, MD, PhD1
1 Department of Orthopaedic Surgery, Seoul National University Hospital, 101 Daehang-ro, Jongno-gu, Seoul 110-744, South Korea.
The Journal of Bone and Joint Surgery (American) 0:JBJS.I.01122-jbjs.I01122 (2010)
This prospective randomised study did not find any difference in standard rotating platform TKA and high flexion rotation platform TKA
A recent meta-analysis suggests that there is no difference in Range of motion in standard Vs high flexion TKA.
1. R. Mehin, ; R. S. Burnett, ; P. M. A. Brasher, Journal of Bone and Joint Surgery – British Volume, Vol 92-B, Issue 10, 1429-1434.
High flexion TKR ..Is it just a hype??Write your views
HIGH FLEXION TKR IS A MYTH. RPF is one of the classical examples of how hype and money muscle can sustain a product. For me its not the range of movement but the survival of the prosthesis thats shown definite data favoring LCS (RP). i cant see anything favoring RPF, Rotating platform (meniscal bearing), or any merit in the age old debate of CR vs PS
consistently the survival analysis of LCS (RP) is shown to be better than other types of fixed and even mobile bearings like meniscal bearing or the much hyped (but no fact base) RPF .…wht u guys think bt it?
most of the studies that show that mobile bearing and fixed bearing have comparable long term outcome have a fault in built in them as either they tend to use meniscal bearing designs in mobile bearing group which tilts the balance in favour in fixed bearing or they do a follow up less than 15 yrs and say both FB and LCS (RP) are same.. i find the results of LCS (RP) to be the best in all well done studies
1)Twenty-Year Evaluation of Meniscal Bearing and Rotating Platform Knee
Replacements ; Frederick F. Buechel, ;Michael J. Pappas, ; CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Number 388, pp. 41–50..by the parents of LCS..ok, there could be a surgeon bias we could argue ; but 20 yrs is follow up
2)Mobile-Bearing Total Knee Arthroplasty; Better Than a Fixed-Bearing?Zachary D et al 2009 review article in journal of arthroplasty shows superiority of LCS (RP) but erratically puts meniscal bearing along with mobile bearing and makes it as good as FB
3) The cox et al, study that Hitesh has put up earlier in the same site, just look at studies cited in clinical trials section…. they have given 10 clinical trials…none exept two has a mean follow up more than 5 yrs!..now thats not a time period for analyzing half life of a knee !!! of the other two, one has used meniscal bearing and the next shows no diff at 13 yrs…
plus there’s always the problem of extra bone loss in the RPF design (from posterior condyle) which compromises the bone stock for revision
Regarding High Flex:
my boss dr Rajesh Maniar is one of the co designers of RPF(Rotating platform with high flex) along with dr CS Ranawat.
He does an RPF only when:
1. he is very sure that his posterior cut will not injure the MCL.
2. and when pre OP ROM is good
There is a multicentric trial with Dr Maniar and Dr CSR going on high flex.
the RPF(J and J) designers suffered the greatest blow with Dr Han’s paper in JBJS b, reporting early femoral component loosening with Nex gen LPS FLex(Zimmer).
they reported early femoral component loosening in 38% of knees
J Bone Joint Surg Br. 2007 Nov;89(11):1457-61.
High incidence of loosening of the femoral component in legacy posterior stabilised-flex total knee replacement.
Han HS, Kang SB, Yoon KS
there is another recent paper suggesting high rate of femoral component loosening,
where deep flexion was allowed.Also from Korea. Again with LPS Flex
Three- to six-year follow-up results after high-flexion total knee
arthroplasty: can we allow passive deep knee bending?
Sung-Do Cho • Yoon-Seok Youm • Ki-Bong Park
Knee Surg Sports Traumatol Arthrosc
DOI 10.1007/s00167-010-1218-x
The pendulum of doing or not doing an RPF is now swinging towards not doing the RPF except in well selected cases. Is it the range of motion in an RPF knee that is important or is it the evidence that there is improved function. Much of the papers quoted above do say that the net function achieved is not more than of a non high flex knee .
Loosening and the extra posterior bone cut are of concern here definitely. A recent paper from Orthopedics argues that a significant increase in range of motion can be achieved by using a high flex insert only without altering basic cuts and without altering the bone cuts or the metallic components.
ORTHOPEDICS September 2010;33(9):667.
Can High-Flexion Tibial Inserts Improve Range of Motion After Posterior Cruciate-Retaining Total Knee Arthroplasty?
by Bradley D. Crow, MD; Julie C. McCauley, MPHc; Kace A. Ezzet, MD
available at
http://www.orthosupersite.com/view.aspx?rid=67564
The modified insert has some modifications into the CR insert design as follows
“The standard insert has a slightly raised posterior lip, whereas the high-flexion insert is recessed downward at the posterior margin to facilitate femoral rollback in flexion and eliminate impingement of the femoral component on the back of the polyethylene during rollback. Other design modifications of the high-flexion insert include a more beveled (lower) anterior margin to minimize impingement of the patellar tendon on the front of the insert during high-flexion, a deepened PCL notch, and 1 more degree of posterior slope built onto the surface of the insert. The standard insert has 4° of posterior slope; the high-flexion insert has 5° of posterior slope. The high-flexion insert also has a more conforming anterior surface to help prevent paradoxical (anterior) motion of the femur during flexion.”
now the satisfactory flexion achieved in these cases by the authors was not a function of altering bone cuts but simply altering the insert geometry.
IS THE KNEE FLEXION A COMPONENT OF PATIENT SATISFACTION
A number of papers talk about knee flexion being an essential component of the satisfaction from knee replacement especially in the younger population undergoing TKA. This is believed to be the USP behind the marketing of the RPF devices.
some recent papers on this subject
1) Does Greater Knee Flexion Increase Patient Function and Satisfaction After Total Knee Arthroplasty?
Brandon N. Devers BA, , Michael A. Conditt PhD†, Miranda L. Jamieson BASc†, Matthew D. Driscoll BA, Philip C. Noble PhD‡ and Brian S. Parsley MD
Received 8 February 2009; accepted 19 February 2010. Available online 21 April 2010.
Journal of Arthroplasty (2010) in press
available at http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WHB-4YX0BNP-2&_user=3976312&_coverDate=04/21/2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1520816659&_rerunOrigin=google&_acct=C000057952&_version=1&_urlVersion=0&_userid=3976312&md5=b44e851affd6bad44d0ab2eb02566ee4&searchtype=a
Abstract
The purpose of this study was to determine whether high flexion leads to improved benefits in patient satisfaction, perception, and function after total knee arthroplasty (TKA). Data were collected on 122 primary TKAs. Patients completed a Total Knee Function Questionnaire. Knees were classified as low (?110°), mid (111°-130°), or high flexion (>130°). Correlation between knee flexion and satisfaction was not statistically significant. Increased knee flexion had a significant positive association with achievement of expectations, restoration of a “normal” knee, and functional improvement. In conclusion, although the degree of postoperative knee flexion did not affect patient satisfaction, it did influence fulfillment of expectations, functional ability, and knee perception. This suggests that increased knee flexion, particularly more than 130°, may lead to improved outcomes after TKA.
2) this paper is a paper from Chennai from a colleague of ours
Is extreme flexion of the knee after total knee replacement a prerequisite for patient satisfaction?
Karthik Narayan, George Thomas and Ravi Kuma
INTERNATIONAL ORTHOPAEDICS
Volume 33, Number 3, 671-674, DOI: 10.1007/s00264-008-0557-4
The focus of this study was to evaluate the functional result and to specifically ascertain whether the absence of the ability to squat and sit cross-legged altered the patient’s satisfaction level after a successful standard total knee replacement. Squatting and sitting cross-legged are common practices in Asia. These activities are not possible following standard total knee replacement. Patients were followed-up for a minimum of 12 months post surgery. Their level of satisfaction was assessed using a Likert scale. The Knee Society Score (KSS) was used to assess range of motion and function of the knee. Twenty-one out of 25 patients were satisfied with the surgical result in spite of an inability to squat. Deep knee flexion may not be an essential prerequisite for patient satisfaction after total knee replacement, even in a population where squatting and sitting cross-legged are part of the normal lifestyle.
3) J Arthroplasty. 2008 Oct;23(7 Suppl):6-10.
High-flexion total knee arthroplasty.
Long WJ, Scuderi GR.
Abstract
High-flexion total knee arthroplasty is considered flexion beyond 125 degrees . Certain activities and a number of workplace demands benefit from this greater range of motion. Some cultures and religions place more emphasis on deep knee flexion. Important patient factors include preoperative motion, body mass index, and previous knee surgery. Component design modifications focus on lengthening the radius of curvature through the posterior condyles, increasing the posterior condylar offset, recessing the tibial insert, lengthening the trochlear groove, and altering the cam-post design. These changes allow increased femoral rollback, translation, and thus clearance in deep flexion. Surgical techniques focus on soft tissue balancing, component sizing and position, removal of impinging osteophytes, and reestablishment of the flexion gap. A number of outcome studies have demonstrated benefits for high flexion after standard total knee and high-flexion designs.
So the Potential benefits of achieving a high Flexion in the face of the wear patterns shown in the studies quoted by Hitesh , need to be reexamined. Though the definition of high flexion itself varies from 120 to 125 to 130 degrees, the increased range of motion using the high flex insert above in Crow et all was about 120 degrees only.
Narayan et al also have disproved that function and satisfaction is essentially determined by range of flexion
Now looking at a meta analysyis in 2008 in the British JBJS
J Bone Joint Surg Br. 2010 Oct;92(10):1429-34.
Does the new generation of high-flex knee prostheses improve the post-operative range of movement?: a meta-analysis.
Mehin R, Burnett RS, Brasher PM.
Abstract
A new generation of knee prostheses has been introduced with the intention of improving post-operative knee flexion. In order to evaluate whether this goal has been achieved we performed a systematic review and meta-analysis. Systematic literature searches were conducted on MEDLINE and EMBASE from their inception to December 2007, and proceedings of scientific meetings were also searched. Only randomised, clinical trials were included in the meta-analysis. The mean difference in the maximum post-operative flexion between the ‘high-flex’ and conventional types of prosthesis was defined as the primary outcome measure. A total of five relevant articles was identified. Analysis of these trials suggested that no clinically relevant or statistically significant improvement was obtained in flexion with the ‘high-flex’ prostheses. The weighted mean difference was 2.1° (95% confidence interval -0.2 to +4.3; p = 0.07).
In effect we come down to four basic problems that we are far from achieving a solution for
1) Is high flexion really necessary
2) Is high flexion directly correlated to functional outcome
3) are the posterior condylar and extra cuts essential, to sacrifice so much extra bone to achieve higher flexion, or would the new high flex inserts eventually pave the way.
4) There is eventually a role of many confounding factors like preoperative range of motion and patient profiles which may affect eventual range achieved.
The jury is still out
No more doubts. High flexion, rotating platform, LCS – none of them have results as good as PFC Sigma and Genesis II. Look at the joint registry data from Sweden, Norway, UK and Australia and the facts will be clearer than before.