Low Contact Stress (LCS) knee. ..... personnel, local criteria for revision, and center volume .... rotating-platform low contact stress mobile-bearing total knee.
The Journal of Arthroplasty Vol. 28 No. 1 2013
Long-Term Clinical Outcomes and Survivorship After Total Knee Arthroplasty Using a Rotating Platform Knee Prosthesis A Meta-Analysis Colin D.J. Hopley, MEng, MBA, MPH,* Lawrence S. Crossett, MD,y and Antonia F. Chen, MD, MBAy
Abstract: A systematic search identified 29 papers reporting survivorship and clinical and function Knee Society Scores (KSS) of 6437 total knee replacements using the Low Contact Stress (LCS) Rotating Platform (RP) mobile bearing knee. Low Contact Stress RP survivorship and KSS outcomes were compared with non-LCS knees in the Swedish knee registry at comparable time periods and in 2 independent systematic reviews of knee arthroplasty outcomes. There is a substantial body of mainly observational evidence supporting the LCS RP knee. Knee Society Score outcomes were comparable for LCS RP and non-LCS RP knees at up to 15 years of follow-up, with mean clinical and function scores ranging from 72 to 96 and 58 to 90, respectively. Survivorship of LCS RP knees up to 14 years was higher than that for all knees in the Swedish Knee Registry. Keywords: rotating platform, mobile bearing, total knee arthroplasty, meta-analysis, survivorship, Low Contact Stress (LCS) knee. © 2013 Elsevier Inc. All rights reserved.
The Low Contact Stress (LCS) knee system was first introduced in 1977 and is a mobile bearing implant where the polyethylene insert, which is fully congruent in gait, rotates about the tibial axis [1]. This allows a decoupling of the rotational forces, which reduces loosening forces in the proximal tibia and decreases wear by allowing unidirectional motion [1]. It was first made available with 2 different types of polyethylene inserts: the rotating platform bicruciate sacrificing insert (RP) and the mensical bearing bicruciate retaining insert (MB). Subsequently, a third bearing insert, the anterior posterior glide (AP Glide) posterior cruciate retaining insert, has also been introduced. Of the 2 bearing inserts originally developed, the LCS Rotating Platform (LCS RP) is still in regular use in 2012. Since its introduction, it has been largely unchanged and is the only design of
mobile-bearing total knee arthroplasty (TKA) that has over 30 years of clinical use. It can be considered as a benchmark of mobile bearing TKA performance and is supported by a large body of publications and has more than 20 years of clinical follow-up [2]. During its life, the modifications to the LCS RP knee have largely been limited to the introduction of deep dish inserts, the use of gamma vacuum sterilized polyethylene, a narrower anterior flange, and an extended femoral component. Given the high prevalence and increasing incidence of knee arthritis and TKA procedures worldwide, it is imperative that decisions regarding TKA prostheses are informed by reliable and generalizable evidence [3,4]. A previous study by Cathrothers et al reviewed publications that reported on all mobile bearing designs comparing the performance of LCS MB Knees, LCS AP Glide knees, PFC Sigma Rotating Platform knees (DePuy, Warsaw, IN), and LCS RP knees [5]. This found a trend for higher survivorship with the rotating platform knees than with LCS MB knees, where PFC Sigma RP and LCS RP knees were grouped together. The objectives of this review were to identify and synthesize the best available evidence regarding key clinical outcomes and survivorship in primary TKA for the LCS RP knee prostheses, selected as the single best performing version of the LCS mobile
From the *DePuy International Ltd., Leeds, UK; and yUniversity of Pittsburgh, Pittsburgh, PA, USA. Supplementary material available at www.arthroplastyjournal.org. Submitted November 22, 2011; accepted April 21, 2012. The Conflict of Interest statement associated with this article can be found at http://dx.doi.org/10.1016/j.arth.2012.04.026. Reprint requests: Antonia F. Chen, MD, MBA, University of Pittsburgh, 6326 Marchand Street, Pittsburgh, PA 15206, USA. © 2013 Elsevier Inc. All rights reserved. 0883-5403/2801-0012$36.00/0 http://dx.doi.org/10.1016/j.arth.2012.04.026
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TKA Using a Rotating Platform Knee Prosthesis Hopley et al
bearing knee system. We compared our findings to well-established results from other predominantly fixed bearing knee prostheses available in national joint registries on contemporary cohorts of TKAs, and systematic reviews of TKA as a class.
Materials and Methods Literature Search A systematic search was conducted on EMBASE and Medline on-line databases for articles published in any language between 1980 and 2012 that reported the postoperative Knee Society Scores (KSS) or survivorship for the LCS RP knee. The search terms included, knee, arthroplasty, LCS, low contact stress, mobile bearing, RP, rotating platform, mensical bearing, and AP Glide. This search was supplemented with manual searches of national joint registries and the bibliographies of located studies and a review of studies. For comparison purposes, searches were conducted of national joint registry reports for survivorship data on generalizable cohorts of TKA and for systematic reviews of TKA as a class summarizing the postoperative KSS in journal articles on TKA with designs other than the LCS knee. Study Selection Studies of all designs reporting outcomes of TKA using the LCS knee with rotating platform insert in primary TKA were eligible for inclusion. Key outcomes of interest were KSS knee function and pain [6] and cumulative revision rates (CRR). There were no minimal requirements for the number of patients or knees, or duration of follow-up. National joint registry data sets on the survivorship of TKA as a class were included as a comparison if the performance of the LCS knee could be separated or if a comparison population contained less than 3% LCS knees. Systematic reviews of TKA as a class that reported the KSS for TKA with designs other than the LCS knee were included as a comparison of clinical performance. Reviews that included data on LCS knees were only eligible if the KSS of non-LCS studies could be extracted separately. Database Development Two independent reviewers extracted data from each eligible LCS RP and non–LCS RP paper using a data extraction sheet developed for this review. Differences in data were resolved by discussion. The data extracted included patient demographics, mean follow-up intervals, patient attrition, clinical outcomes, revision rates, or survivorship for the longest follow-up intervals available. Complications that involved further surgery were identified and classified according to the reason for reoperation. Studies were appraised for quality according to their study design [7].
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Statistical Methods Results for LCS RP treatment groups were pooled across all eligible studies and compared indirectly with the best available published evidence on non-LCS TKA prostheses. LCS RP platform CRR data and KSS were meta-analyzed using random effects models in which between study variation was accounted for using the Dersimonian and Laird method [8,9]. Studies were weighted using the inverse variance method and the variance of survivorship in each study was calculated using Greenwood's formula [8]. The variance/SDs of KSS were extracted directly from the studies or estimated from the range or interquartile range when reported. When no such information was available, the pooled SD of KSS from studies that did report it was used. When analyzing revision rates, the pooled CRR of the LCS RP knee from studies reporting survivorship at 2, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 17, 18, and 20 years was estimated. At each time interval, data were included from LCS RP studies that reported results at that time and where CRR data could be extracted for preceding time points; this was also used in the meta-analysis at those time points. Asymmetric estimates of the 95% upper and lower confidence limits of the survivorship were also estimated using the method described by Kalbfleisch et al [10]. Survivorship was converted to CRR by the following simple calculation: CRR% = 100 − survivorship (%). In many survivorship studies, only the number of patients entered into the study and the average length of follow-up was included. To account for patient attrition, when estimating the variance of CRR, it was assumed that all patients had a minimum 2-year follow-up, which was the minimum average follow-up in the studies, and that the number of patients at risk of revision in each study decreased by 5% with each year after surgery. The Swedish Knee Registry reports a consistent improvement in the survivorship of total knee replacements implanted over 5-year time periods between 1976 and 2009, attributed to improvements in surgical technique, implant design, and patient selection [11]. As the LCS RP survivorship studies cover a wide time frame from 1980 to 2005, they were stratified into 2 groups of studies: contemporary studies and older studies, determined by surgical date in the studies. Studies with knees mainly implanted before and after 1990 were classified as older and contemporary studies, respectively. To provide further insight, the reasons for revision reported by the LCS RP survivorship studies were analyzed. The crude incidence of each type of revision was calculated as the number of each type of revision divided by the number of knees entered into each study. In this analysis, all the survivorship studies from all dates were grouped together with a subgroup of studies with at least 10 years of follow-up. When pooling LCS RP postoperative Knee Society (KS) knee and function scores, studies were grouped according
70 The Journal of Arthroplasty Vol. 28 No. 1 January 2013 to average length of follow-up. Scores were also pooled across all studies. These were compared with non-LCS postoperative scores published in systematic reviews of TKA, grouped and analyzed using the same method. Although some studies reported KSS at multiple time points, in the analysis stratified for time, Bonferroni adjustment for multiplicity was used and resulted in individual 99% confidence intervals [12]. Preoperative KSS was infrequently reported in the LCS RP studies. To provide some insight on these scores when reported, the weighted average of preoperative KSS was also calculated using the number of knees as the basis of the weighting. As variances were based on estimates of sample size and SDs, rather than calculating P values for differences, any differences were considered to be potentially significant if the 95% confidence intervals of the survivorship or KSS with LCS RP did not coincide with those of the comparison groups.
Results LCS Studies and Patients The electronic and manual searches yielded a total of 29 eligible papers on 28 groups of TKA patients involving 6437 knees treated with the LCS knee with a rotating platform insert (Fig. 1). Of these, 14 papers reported both survivorship (or cumulative revision rates) and postoperative KSS [2,13-25], 6 reported survivorship only [26-31], and 9 papers reported clinical outcomes using KSS only [32-40]. Excluded references included reviews, commentaries, studies not using LCS RP knees in a primary TKA setting,
or outcomes of interest. Eleven papers double-reported outcomes in the same set of patients. Of the 29 papers included in the review, 5 papers [20-22,39,40] contributed 4 LCS RP groups from 4 level I randomized controlled trials. There were 13 groups from 9 level II nonrandomized comparative studies and 2 level III retrospective controlled studies [14,18,19,26,27,29,30,32,33,37,38]. The remaining 11 groups were from 11 case series reported in 13 publications [2,13,15-17,23-25,28,31,34-36]. There were three citations for one study [2,15,16] due to reporting of KSS results at 3 different time points. In the LCS RP groups where indication was reported, most of the patients had osteoarthritis (OA) except in one where 50% of patients had rheumatoid arthritis (RA). OA as an indication for surgery was the diagnosis in more than 80% of knees in 21 groups and less than 80% of knees in 3 groups, and was not reported in 4 groups. The average age of the patients ranged from 60 to 75 years in 25 of the LCS RP groups, was 58 years in one group, and was not reported in 2 groups. More than 60% of patients were women in 18 LCS RP groups, less than 60% women in 5 groups, and was not reported in 5 groups. The proportion of patients who were lost to follow-up and had an unknown outcome was less than 10% in all but one group [35]. Fixation was cemented in 11 groups, cementless in 11 groups, cemented and cementless in 5 groups, and not reported in 1 group. Postoperative KS knee scores were reported in 21 publications with 20 groups that totaled 2698 LCS RP knees with up to 20 years of follow-up. There were 15
Fig. 1. Flow diagram of the literature search.
TKA Using a Rotating Platform Knee Prosthesis Hopley et al
publications that reported postoperative KS function scores in 2391 LCS RP knees up to 20 years of follow-up. The studies reporting survivorship of the LCS RP knee were stratified into 2 groups determined by the surgical dates in the study. Six studies reported survivorship on 6 groups of LCS RP knees including 3462 knees implanted between 1981 and 1997 and were classified as older studies [2,18,26,28,29,31]. Twelve studies reporting survivorship on 12 groups of LCS RP knees including 2145 knees implanted between 1988 and 2005 were classified as contemporary studies [13,14,17,19-25,27,30]. In the LCS RP studies reporting survivorship, 17 following 5867 knees reported reasons for revision. Of these, 8 studies had mean follow-up greater than 10 years (1939 knees). Comparators The Agency for Healthcare Research and Quality (AHRQ) and the Ontario reviews were 2 recent independent systematic reviews of TKA that were identified and selected to compare KS knee and functional scores with the LCS RP Knee [41,42]. These reviews were limited to 41 studies, with at least 100 TKAs published between 1995 and 2005, and reported postoperative KS knee and function scores in 56 non-LCS groups in 11 737 and11 581 knees respectively. In all the ARHQ and Ontario review groups, the indication for surgery was OA in more than 80% of knees in 43 groups, less than 80% of knees in 12 groups, and not reported in 1 group. In studies that reported the indication for surgery, most of the patients had OA, except in one where all the patients had RA. The average age of patients ranged from 60 to 75 years in 51 of these groups, was below 55 in 2 groups, and was not reported in another 3. More than 60% of patients were women in 34 groups, less than 60% women in 14 groups, and was not reported in 8 groups. In all groups, the baseline patient characteristics were similar except in 4 groups, where 3 had more men than women, and the diagnosis was RA in all patients for one study. Seven national joint registries were identified [11,4348]. Five were excluded as they either had no survivorship results or reported survivorship on all knees including significant proportions of LCS knees (7%-23%) [42-46]. For the comparison, we used the survivorship data extracted from the graphs published in the Swedish Knee Arthroplasty Registry on 12 129 knees implanted in patients with OA between 1991 and 1995 and 94 418 knees implanted between 1996 and 2009 as the time points that most closely approximate the LCS study dates [11]. More than 94% of implants in this Registry were fixed-bearing and cemented designs, and there were only 269 LCS knees (0.3%) from 1996 and 2009. Clinical Outcomes: KSS A review of reported preoperative KSS does not indicate a difference in preoperative or postoperative scores
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between the LCS RP studies and the AHRQ and Ontario review studies. The preoperative KS knee scores for the LCS RP studies ranged from 21 to 57 (weighted mean, 34) and, for function scores, ranged from 29 to 49 (weighted mean, 39). The KS knee scores reported preoperatively in the AHRQ and Ontario reviews were ranged from 21 to 68 (weighted mean, 39), and the function scores ranged from 28 to 64 (weighted mean, 48). For all LCS RP studies, the postoperative KS knee scores ranged from 72 to 96, and the KS function ranged from 58 to 90 (indicating good to excellent results) for follow-up to 21 years. In non-LCS knee studies in the AHRQ and Ontario review, KS knee scores ranged from 68 to 97, and KS function ranged from 51 to 94 (Figs. 2 and 3 and Tables 1 and 2; available online at www. arthroplastyjournal.org). Stratifying by length of followup, the pooled postoperative KSS were only higher on average in the LCS RP studies at 2 to 3 years and 7 to 10 years for knee scores and 2 to 3 years and 13 to 15 years for function scores. None of the differences in KSS between the groups at any time point were significant, as all the confidence intervals estimated by meta-analysis intersect. In both data sets, there was no apparent association between mean length of study follow-up and the reported KS knee or function scores. The pooled postoperative KS knee and function scores in all the LCS RP studies, without stratification for time, were 89 (95% CI, 85-93) and 78 (95% CI, 72-84). The pooled postoperative KS knee and function scores in all the non-LCS RP studies in the AHRQ and Ontario reviews were 88 (95% CI, 84-92) and 74 (95% CI, 7277), respectively. Revision Rates and Survivorship The long-term pooled revision rates with the LCS RP knee implanted between 1981 and 1997 and 1988 and 2005 were lower (ie, higher survivorship) on average than that of TKAs reported in the Swedish Knee Registry for knees implanted between 1991 and 1995 and 1996 and 2009, respectively. When comparing older data sets (LCS RP knees implanted between 1981 and 1997 and Swedish Registry between 1991 and 1995), the revision rate difference appeared to be significant only at 7 years after surgery (Table 3; available online at www.arthroplastyjournal.org). For the comparison of contemporary data sets (LCS RP knees implanted in 1988-2005 and Swedish Registry in 1996-2009), the difference in revision rates was significant at all time points between 5 and 10 years, since the 95% confidence intervals of survivorship did not intersect (Table 4). Five studies reported survivorship of 98.3%, 98%, 96.5%, 92.1%, and 76% at 15 years with LCS RP knees and two reported survivorship of 98.3% and 96.5% at 18 years. The longest reported survivorship with the LCS RP knee was 96.5% at 20 years.
72 The Journal of Arthroplasty Vol. 28 No. 1 January 2013
Fig. 2. Knee Society Knee Scores of LCS RP and AHRQ and Ontario non-LCS knees.
In all the LCS RP survivorship studies, the most common reasons for revision were wear osteolysis and loosening (64/5539, 1.2%). There were 47/5539 revisions (0.8%) for instability, which included both
instability and spin out. Other common reasons for revision were infection (0.5%), insufficient surgery (0.3%), and patella-related complications (0.7%). Excluding studies with less than 10 years mean follow-up
Fig. 3. Knee Society function scores of LCS RP and AHRQ and Ontario non-LCS knees.
TKA Using a Rotating Platform Knee Prosthesis Hopley et al
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Table 4. Survivorship—LCS Knees Implanted in 1988 to 2005 and Swedish Knee Registry Knees Implanted in 1996 to 2009 Ref
Author
Bearing Type
LCS with rotating platform 23 O'Brien Rotating platform 30 Stiehl JB Rotating platform 24 Papachristou G Rotating platform 14 Bhan S Rotating platform 19 Kim YH Rotating platform 13 Ali MS Rotating platform 25 Specchiulli F Rotating platform 20 Kim YH Rotating platform 27 Cho Rotating platform 17 Esftathopoulos Rotating platform 22 Kim Rotating platform 21 Kim Rotating platform Pooled survivorship LCS with rotating platform, % Upper 95% confidence interval Lower confidence interval All knees Sweden 1996-2009 Upper 95% confidence interval Lower 95% confidence interval
No. of Knees 600 44 251 32 196 109 93 62 68 423 107 160 2145
99,418
Survivorship % 2y
5y
6y
7y
100.0 100.0 99.2
98.5 100.0 98.1
98 100.0
98 100.0
100 99.1
100 99.1
94 100 99.1
100 99.1
8y
9y
10 y
97.8
97.8
97.8
99.1
99.1
99.1
12 y
15 y
Date of Implantation 1993-1996 1990-2000 1995-2000 1996-1998 1996-1998 1988-1996 1993-1998 (est) 1994-1996 1995-2000 1995-2005 2000 1992-1995 1988-2005
88 97 100
100 100
100 99.5
100 99.4
100 99 97.2
100 98.6
100 98.6
100 98
99.9 *
99.2 †
99.0 †
98.7 †
98.3 †
98.3 †
98.1 †
96.3
98 98.0
100.0 95.7 98.5 * 98.6 98.4
99.6 98.4 97.5 † 97.7 97.3
99.4 98.1 97.3 † 97.5 97.1
99.2 97.8 97.0 † 97.2 96.7
98.9 97.3 96.8 † 97.0 96.3
98.9 97.3 96.5 † 96.7 95.8
98.8 97.1 96.0 † 96.5 95.0
98.4 91.6
99.4 93.7 1996-2009
* Not significant. † Significant.
did not substantially change the crude incidence of each type of revision. In these studies, the incidence of osteolysis and loosening was 28/1956 (1.4%), and the incidence of instability was 27/1956 (1.4%).
Discussion This study demonstrates that there is a large amount of primarily observational evidence suggesting that TKA with LCS RP implants is associated with clinical outcomes equivalent to fixed-bearing knee prostheses. More importantly, however, there is also a large body of evidence supporting the long-term survivorship of LCS RP implants. For all years of surgery, the pooled survivorship of LCS implants was 94% to 97% at 12 years with several studies reporting 96% to 98% survivorship at up to 18 years. A previous systematic review compared the survivorship of the LCS RP knee to the cruciate-retaining LCS Meniscal Bearing Knee (LCS MB knee) [5]. This identified a trend for better survivorship of the LCS RP at 10 years and was statistically significant at 15 years [5]. Our review has identified additional studies and is the first to compare the LCS RP, the best performing version of the LCS knee, with generalizable data from predominantly fixed-bearing total knee replacements. Although this review includes a substantial body of evidence, it should be noted that there is little evidence available that provides a direct, quantitative comparison of LCS RP knees to other types of TKA implants. This problem is not unique to LCS RP knees as it is difficult, if not impossible, to randomize and adequately control surgical implant studies. Using semi-contemporary and approximately matched con-
trol patients from high quality sources, we have been able to generate a useful comparative assessment in this review. The LCS RP knee survivorship results were sorted into 2 periods according to surgical date: 1981 to 1997 and 1988 to 2005. While these intervals do not exactly match the reporting intervals in the Swedish Knee Registry, implantation intervals were matched as closely as possible for analysis purposes. When in doubt, LCS RP knee results were always compared to the more recent Swedish Registry results to provide a more rigorous comparison. For roughly comparable patients and time periods of implantation, the pooled CRR of the LCS RP knee was lower on average than the CRR of the Swedish Knee Registry at all reporting times out to 9 and 12 years (Figs. 4 and 5). The survivorship in more contemporary studies (19882005) was substantially higher than older studies, a similar improvement to that reported in the Swedish Registry during a similar time frame. Although we did not give a precise calculation of statistical significance, the pooled variance of survivorship across all LCS RP studies does suggest that the revision rate in the LCS RP studies was significantly lower than in the Swedish registry at 7 and out to 10 years follow-up in the older and more recent data sets, respectively. The confidence intervals we estimated for the pooled LCS RP survivorship were based on some modest assumptions about patient attrition using asymmetric ranges. The random effects model estimated that the 95% confidence interval of the 20 years survivorship in the Callaghan study was + 2.75% to − 12.1% [2]. This was larger than the
74 The Journal of Arthroplasty Vol. 28 No. 1 January 2013
Fig. 4. Cumulative revision rate—LCS RP knees implanted in 1981 to 1997 and Swedish Registry Knees implanted in 1991 to 1995.
actual value reported in the paper (± 3.9%). This gives validity to the finding that some differences in survivorship were significant.
In the older data set with over 7 years of follow-up, the difference in survivorship of LCS RP knees and the Swedish Registry TKAs did not appear to be significant.
Fig. 5. Cumulative revision rate—LCS RP knees implanted in 1988 to 2005 and Swedish Registry Knees implanted in 1996 to 2009.
TKA Using a Rotating Platform Knee Prosthesis Hopley et al
There are few studies with longer follow-up, and with the 5% reduction of patients at each time point we imposed, there were consequently few patients in the sample at the longer time points. In the meta-analysis of older LCS RP knees, it appears that survivorship improved with time between 12 and 16 years. This occurred because the pooled estimate of survivorship at 12, 14, and 15 years included 3 studies that reported lower survivorship at those time points than two studies that reported survivorship beyond 16 years. This is potentially an indication of some performance bias favoring studies with longer follow-up. This type of performance bias was not evident in the contemporary studies, as the survivorship was fairly consistent with no evidence of heterogeneity across them. Tibial wear, osteolysis, and loosening are all failure modes that the rotating platform design seeks to address by optimizing wear through design. They were the most common reasons for revisions when combined, accounting for approximately one third of the revisions identified in the LCS RP survivorship studies. In the subgroup of studies with at least 10 years of mean follow-up, some with up to 20 years, the number of these revisions remained low, despite all these studies using older grades of polytheylene with inferior wear properties. This suggests that the rate of revision for osteolysis, wear, and loosening remains low in the second decade after surgery. Many of the remaining revisions were accounted for by spin out of the tibial insert or instability, but the overall incidence was low. A systematic review reported complications after TKA with all types of mobile bearing knee, including the LCS RP knee, the LCS MB knee, and the Sigma Rotating Platform knees [49]. This review compared contemporary and older studies of mobile bearing knees and found a substantially lower incidence of revisions related to instability, including spin out and dislocation, in the contemporary studies which is attributed to improvements in surgical technique and implant design. Although there was some difference in survival of LCS RP knees and the Swedish knee registry, the analysis is not based on direct comparison data, but on an aggregation of observational data. We are unable to fully adjust for potential differences in patient selection for different implants, outcome ascertainment and follow-up, learning curves and experience of surgical personnel, local criteria for revision, and center volume and care pathway effects, among other potential confounding sources. Between the LCS RP studies and the Registry patient gender, diagnosis and surgery time periods were generally similar, but not identical. In the Swedish registry, 65% of patients were women. In the LCS RP studies, the proportion of women varied from 15% to 94%, and the mean patient age ranged from 60 to 77 years. There may also be performance bias favoring the LCS RP knee as studies published in peer-reviewed
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publications are typically conducted by experienced surgeons, whereas the comparison data for survivorship from a national joint registry reports the performance of all grades of surgeons. Mitigating some of these factors, it should be noted that Swedish Registry data may represent a particularly rigorous comparison. The survivorship data was only on patients where the diagnosis was OA, and these patients have higher survivorship than patients with RA [14]. The LCS RP data sets included both OA and RA patients, with most having OA. A review of the Norwegian Swedish and Danish knee arthroplasty registries also found that the survivorship of TKA in Sweden was substantially higher than in Norway or Denmark, suggesting that the Swedish orthopedic community is further along the learning curve than these other 2 countries and that good practice is widespread in Sweden [50]. Despite this, it is difficult to conclude that the identified differences in survivorship are treatment effects of the LCS RP implant. The long-term clinical outcomes reported with the LCS RP knee appear to be comparable to those reported for TKA as a class, represented by the AHRQ and Ontario reviews. There were no statistically significant differences in the KS knee and function scores pooled across all the studies, or at any follow-up time, denoted by the confidence intervals estimated by random effects metaanalysis. However, the variability of pre- and postoperative scores in individual studies makes interpretation challenging, and the comparison with the AHRQ and Ontario review has similar limitations to the survivorship analysis. In addition, when data was missing, assumptions were made on the SDs of KSS that may have led to imprecision. These were either estimated from the ranges or calculated to be the pooled SDs from all the studies. Using pooled SDs was necessary for 6 of 20 LCS RP groups and 7 of 54 non-LCS groups but did allow a larger data set to be included. To control preoperative clinical and function performance, it may have been preferable to analyze the difference in the pre- and postoperative KSS. This was not possible as the preoperative KSS were only reported infrequently in the LCS RP studies. The large number of studies and knees followed up in the analysis may in part mitigate these limitations and give some assurance on the findings regarding clinical performance of the LCS RP knee compared with the class of TKA.
Conclusion The survivorship of the LCS rotating platform TKA, reported in peer-reviewed literature, appears to be higher out to 10 years follow-up relative to generalizable reports from the Swedish Knee Registry. Very high survivorship has now been reported out to 20 years with a very low incidence of wear related revision in the second decade. The LCS RP knee also has comparable
76 The Journal of Arthroplasty Vol. 28 No. 1 January 2013 long-term clinical outcomes, as reflected in KSS, to those reported in the recent AHRQ and Ontario systematic reviews of TKA implants as a class. Definite conclusions are impeded by the restriction of this review to mainly observational data and the existence of several confounding factors that could not be controlled for.
Acknowledgments The authors wish to thank Dr Candace Gunnarsson of S2 Solutions, Inc, for advice and assistance with the protocol and analysis plan for this project; Jack Williams of Aston University Birmingham, England, for assistance with data extraction; and John Leopold of DePuy, Inc, Warsaw, IN, for guidance on the statistical methods.
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14. Bhan S, Malhotra R, Kiran EK, et al. A comparison of fixed-bearing and mobile-bearing total knee arthroplasty at a minimum follow-up of 4.5 years. J Bone Joint Surg Am 2005;87:2290. 15. Callaghan JJ, Squire MW, Goetz DD, et al. Cemented rotating-platform total knee replacement. A nine to twelve-year follow-up study. J Bone Joint Surg Am 2000;82:705. 16. Callaghan JJ, O'Rourke MR, Iossi MF, et al. Cemented rotating-platform total knee replacement: a concise follow-up, at a minimum of fifteen years, of a previous report. J Bone Joint Surg Am 2005;87:1995. 17. Esftathopoulos N, Mavrogenis A, Lallos S, et al. 10-Year evaluation of the cementless Low contact stress rotating platform total knee arthroplasty. J Long Term Eff Med Implants 2009;19:255. 18. Huang CH, Ma HM, Lee YM, et al. Long-term results of Low contact stress mobile-bearing total knee replacements. Clin Orthop Relat Res 2003;416:265. 19. Kim YH, Kim JS. Comparison of anterior-posterior-glide and rotating-platform low contact stress mobile-bearing total knee arthroplasties. J Bone Joint Surg Am 2004;86:1239. 20. Kim YH, Kim JS, Choi Y. Osteolysis after unidirectional and multidirectional mobile bearing total knee arthroplasty in young patients. J Arthroplasty 2009;24:586. 21. Kim YH, Yoon SH, Kim JS. The long-term results of simultaneous fixed bearing and mobile-bearing total knee replacements performed in the same patient. J Bone Joint Surg Br 2007;89:1317. 22. Kim YH, Kim J-S, Park J-W, Joo J-H. Comparison of the Low Contact Stress and Press Fit Condylar rotatingplatform mobile-bearing prostheses in total knee arthroplasty a prospective randomized study. J Bone Joint Surg Am 2011;93:1001. 23. O'Brien S, Spence D, Ogonda L, et al. LCS mobile bearing total knee arthroplasty without patellar resurfacing. Does the unresurfaced patella affect outcome? Survivorship at a minimum 10-year follow-up. Knee 2011. 24. Papachristou G, Plessas S, Sourlas J, et al. Cementless LCS rotating-platform knee arthroplasty in patients over 60 years without patella replacement: a mid-term clinicaloutcome study. Med Sci Monit 2006;12:CR264. 25. Specchiulli F, Gabrieli R, Borsetti D, et al. Midterm results of mobile-bearing knee replacements. J Orthop Trauma 2007;8:123. 26. Buechel FF. Long-term followup after mobile-bearing total knee replacement. Clin Orthop Relat Res 2002;404:40. 27. Cho WS, Youm YS, Ahn SC, et al. What have we learned from LCS mobile bearing knee system? Knee Surg Sports Traumatol Arthrosc 2010;18:1345. 28. Sorrells RB, Voorhorst PE, Murphy JA, et al. Uncemented rotating-platform total knee replacement: a five to twelve-year follow-up study. J Bone Joint Surg Am 2004;86:2156. 29. Stiehl JB, Hamelynck K, Voorhorst P. International multicentre survivorship analysis of mobile bearing total knee arthroplasty. Orthopedics 2006;30:190. 30. Stiehl JB, Voorhorst PE. Total knee arthroplasty with a mobile-bearing prosthesis comparison of retention and sacrifice of the posterior cruciate ligament in cementless implants. Am J Orthop 1999;28:223.
TKA Using a Rotating Platform Knee Prosthesis Hopley et al 31. Tarkin IS, Bridgeman JT, Jardon OM, et al. Successful biologic fixation with mobile-bearing total knee arthroplasty. J Arthroplasty 2005;20:481. 32. Abu-Rajab RB, Watson WS, Walker B, et al. Periprosthetic bone mineral density after total knee arthroplasty. J Bone Joint Surg Br 2006;88:606. 33. Chiu KY, Ng TP, Tang WM, et al. Bilateral total knee arthroplasty: one mobile-bearing and one fixed-bearing. J Orthop Surg 2001;9:45. 34. Hooper G, Rothwell A, Frampton C. The low contact stress mobile-bearing total knee replacement: a prospective study with a minimum follow up of ten years. J Bone Joint Surg Br 2009;91-B:58. 35. Jung Y, Jung H, Kwak J. Comparison of the clinical outcomes after total knee arthroplasty with PFC Sigma RP-F verses LCS. J Bone Joint Surg Br 2010;92(S1): 128. 36. Maini P, Kailey P, Talwar N. Hybrid fixation in rotating platform mobile bearing total knee arthroplasty using low contact stress knee. Indian J Orthop 2006;40:219. 37. Shah K, Smith J, Jones B, et al. Bilateral total knee replacement under a single anaesthetic, using a cementless implant is not unsafe. Knee Surg Sports Traumatol Arthrosc 2007;15:269. 38. Vasdev A, Kumar S, Chadda G, et al. Fixed- versus mobilebearing total knee arthroplasty in Indian patients. J Orthop Surg 2009;17:179. 39. Woolson ST, Northrop GD. Mobile- vs. fixed-bearing total knee arthroplasty: a clinical and radiologic study. J Arthroplasty 2004;19:135. 40. Woolson S, Epstein N, Huddleston J. Long-term comparison of mobile-bearing vs fixed-bearing total knee arthroplasty. J Arthroplasty 2011;26:1219. 41. Kane R, Saleh K, Wilt TJ, et al. Total knee replacement. Evidence report/technology assessment. Number 86. AHRQ Publication No. 04-E006-2. Rockville (Md): Agency for Healthcare Research and Quality; 2003 [cited 2005
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Feb. 2]. http://www.ahrq.gov/downloads/pub/evidence/ pdf/knee/knee.pdf. (accessed January 30, 2008). The Medical Advisory Secretariat Ministry of Health and Long-Term Care Canada: Total Knee Replacement Health Technology Literature Review June 2005. Publications of the National Agency for Medicines 2/2008. The 2006 Implant Yearbook on Orthopaedic Endoprostheses Finnish Arthroplasty Register. http://www.nam.fi/ instancedata/prime_product_julkaisu/laakelaitos/embeds/ julkaisut_laitteet_ja_tarvikkeet_J082_Endopr_2006.pdf. Accessed 12/10/09. The Department of Epidemiology Aarhus University Hospital. DanskKnæalloplastikregisterÅrsrapport 2011. https://www.sundhed.dk/content/cms/99/4699_%C3% A5rsrapport2011-dkr-final.pdf. Accessed 24/02/12. Department of Orthopaedic Surgery Haukeland University Hospital. The Norwegian Arthroplasty Register Annual Report 2010. http://nrlweb.ihelse.net/eng/default. htm#Publications. Accessed 24/02/12. Australian Orthopaedic Association National Joint Replacement Registry. Annual Report. Adelaide: AOA; 2011 http://www.dmac.adelaide.edu.au/aoanjrr/publications. jsp. Accessed 24/02/12. New Zealand Orthopaedic Association. The New Zealand Joint Registry, twelve year report, January 1999 to December 2010. http://www.cdhb.govt.nz/NJR/reports/ A2D65CA3.pdf. Accessed: 24/02/12. The NRR Centre Hemel Hempstead. National Joint Registry for England and Wales Annual Report 2011. http://www.njrcentre.org.uk/njrcentre/AbouttheNJR/ Publicationsandreports/Annualreports/tabid/86/Default. aspx. Accessed 24/02/12. Hopley C, Crosett L. Systematic review of complications in TKA mobile bearing knees. J ASTM Int 2011;1:8. Robbertsson O, Bizjajeva S, Fenstad A-M, et al. Knee arthroplasty in Denmark, Norway, and Sweden a pilot study from the Nordic Arthroplasty Register Association. Acta Orthop 2010;81:82.
TKA Using a Rotating Platform Knee Prosthesis Hopley et al
77.e1
Table 1. Knee Society Scores of LCS with Rotating Platform No. of Preoperative Postoperative No. of Knees Clinical Mean Mean % Preoperative Postoperative Function Function Ref Author Knees Follow-Up Follow-Up, y Age, y Female % OA Knee Score Knee Score Score Score 35 Jung 110 56 1 NR NR NR NR 94 NR 62.6 33 Chiu 16 16 2 68 88% 88% 51 85 47 71 32 Abu-Rajab 18 18 2 71 44% 100% NR 85 NR 79 32 Abu-Rajab 20 20 2 69 55% 100% NR 86 NR 81 36 Maini 100 98 3 67 100% 85% 30 92 43 80 34 Hooper NR 82 3 NR NR NR NR NR 44.2 63.0 39 Woolson 60 57 3.4 69 55% 77% 42 92 NR 77 38 Vasdev 60 60 3.5 63 50% 100% 40 91 NR NR Pooled scores at final review mean 2-3-year follow-up 91 * 76 * 37 Shah 180 172 5 73 67% 82% NR 78 NR 62 37 Shah 174 171 5 72 63% 80% NR 76 NR 60 24 Papachristou 251 251 5.7 68 85% 87% 21 88 31 79 14 Bhan 34 32 6 63 69% 50% 35 90 NR NR 19 Kim 196 190 6.4 64 94% 85% 26.9 89 NR NR Pooled scores at final review, mean 5-6-year follow-up 86 * 67 * 13 Ali 109 87 6.8 69 64% 86% NR 86 NR 65 22 Kim 112 107 7.4 67 100% 100% NR 96 NR NR 34 Hooper NR 82 7 NR NR NR NR NR 44 60 15 Callaghan 119 66 9.7 70 60% 88% 30 90 44 75 25 Specchiulli 93 93 9.5 70 NR 81% 57 87 40 90 17 Efstathopoulos 423 420 10 73 79% 97% 42 90 44 79 Pooled scores at final review, mean 7-10-year follow-up 92 * 79 * 40 Woolson 60 31 11 66 55% 77% NR 93 NR 68 23 Obrien 600 365 11 71 65% 91% NR 85 NR 74 20 Kim 65 62 11 58 85% 90% 26 90 30 81 18 Huang 322 267 12 62 NR NR NR 72 NR 85 Pooled scores at final review, mean 11-12-year follow-up 84 * 78 * 21 Kim 160 146 13 70 95% 94% 26 90 29 83 16 Callaghan 119 39 15 70 60% 88% 43 85 49 58 Pooled scores at final review, 13-15-year follow-up 89 * 79 * 2 Callaghan 119 26 21 70 60% 88% 43 89 49 67 Pooled scores at final review, mean 21-year follow-up 89 67 * Not significant.
77.e2 The Journal of Arthroplasty Vol. 28 No. 1 January 2013 Table 2. Knee Society Scores of Non-LCS AHRQ and Ontario Reviews AHRQ and Ontario No. of Knees Preoperative Postoperative Review Studies No. of Clinical Mean Mean Sex Diagnosis Preoperative Postoperative Function Function [41,42] Knees Follow-Up Follow-Up, y Age, y (% Women) (% OA) Knee Score Knee Score Score Score Matsueda 2000 169 169 Matsueda 2000 167 167 Cohen 1997 172 172 Cohen 1997 100 100 Bert 2001 264 90 Brander 2003 149 149 Deshmukh 180 130 2002 Bourne 1995 50 50 Bourne 1995 50 48 Elke 1995 415 300 Elke 1995 61 43 Meding 2003 329 329 Meding 2003 4891 4891 Mokris 1997 126 105 Pooled outcome 1-year mean follow-up Bourne 1995 50 50 Bourne 1995 50 48 Heck 1998 330 268 Lin 2002 53 53 Lin 2002 69 69 Jenny 1998 32 32 Jenny 1998 93 93 Rand 1996 277 251 Elke.1995 415 300 Elke.1995 61 43 Meding 2003 329 329 Meding 2003 4891 4891 Yang 2001 109 109 Hube 2002 297 276 Konig 1998 398 276 Pooled outcome 2-3-year mean follow-up Mokris 1997 126 105 Gioe 2000 111 103 Gioe 2000 102 97 Title 2001 74 74 Title 2001 74 74 Pooled outcome 4-year mean follow-up Bullens 2001 126 100 Ranawat 1997 150 125 Healy 2002 103 95 Meding 2003 329 329 Meding 2003 4891 4891 Harwin 1998 241 241 Harwin 1998 109 109 Rinta Kiika 102 102 1996 Mont 1999 121 118 Mont 1999 121 118 Brown 2001 500 500 Brown 2001 36 36 O Rourke 2002 145 78 O Rourke 2002 31 9 Bankes 2003 198 198 Sansone 2004 125 110 Martin 1997 378 306 Pooled outcome 5-6-year mean follow-up Indelli 2002 100 92 Meding 2003 329 329
0.5 0.5 0.5 0.5 1 1 1
67 70 70 69 72 66 69
71% 67% 62% 62% 70% 55% 53%
83% 91% 79% 81% NR 100% 100%
52 51 53 55 41 45 23
90 90 89 87 85 90 79
46 47 43 47 45 46 42
74 75 63 60 71 75 63
1 1 1 1 1 1 1
72 68 75 69 70 70 69
70% 46% 80% 81% 52% 60% 62%
100% 100% 100% 0% 94% 91% 92%
37 41 28 21 47 39 50
41 44 53 40 41 49 41
2 2 2 2 2 2 2 2 3 3 3 3 3 3 3
72 68 70 68 70 69 69 69 75 69 70 70 69 66 71
70% 46% 63% NR NR 69% 69% 62% 80% 81% 52% NR 85% 55% 79%
100% 100% 100% 100% 100% 80% 80% 100% 100% 0% 94% 91% 95% 88% 100%
37 41 35 NR NR 50 41 40 28 21 47 39 37 NR 29
4 4 4 4 4
69 69 69 63 63
62% 4% 4% 72% 72%
92% 92% 92% 82% 82%
50 38 35 43 44
5 5 5 5 5 5 5 5
67 70 70 70 70 65 65 67
NR NR NR 52% NR 58% 58% 77%
61% 83% 100% 94% 91% 100% 0% 76%
33 44 52 47 39 42 32 49
82 82 89 90 88 77 95 88 * 81 87 68 94 94 89 90 89 89 85 88 79 79 NR 82 85 * 97 84 85 95 97 96 * 84 93 92 87 75 92 86 77
70 71 70 70 74 86 94 77 * 67 76 69 85 84 80 79 81 70 70 76 89 64 91 72 74 * 88 74 72 86 92 85 * 52 78 75 73 84 90 68 64
5 6 6 6 6 6 7 6 7
70 70 68 68 69 76 69 72 67
62% 62% 68% 68% 59% NR 63% 53% 74%
96% 96% 89% 89% 93% 90% 80% 95% 66%
52 52 51 54 30 34 29 33 28
42 42 NR NR 50 64 31 45 49
8 7
69 70
85% 52%
100% 94%
41 47
94 94 90 91 85 87 76 82 88 88 * 94 80
41 44 41 NR NR 41 38 46 53 40 41 49 44 52 46 41 56 57 31 30 29 40 50 41 49 52 28 43
48 41
70 70 NR NR 79 79 75 74 72 78 * 79 70
TKA Using a Rotating Platform Knee Prosthesis Hopley et al
77.e3
Table 2 (continued) AHRQ and Ontario No. of Knees Preoperative Postoperative Review Studies No. of Clinical Mean Mean Sex Diagnosis Preoperative Postoperative Function Function [41,42] Knees Follow-Up Follow-Up, y Age, y (% Women) (% OA) Knee Score Knee Score Score Score Meding 2003 AHRQ and Ontario Review Studies [41,42]
4891
No. of Knees
4891
7
70
NR
91%
39
75
49
80
No. of knees Preoperative Postoperative clinical Mean Mean Sex Diagnosis Preoperative Postoperative Function Function Follow-Up follow-Up, y Age, y (% Women) (% OA) Knee Score Knee Score Score Score
Elke 1995 415 300 7 Elke 1995 61 43 7 Healy 2002 56 47 8 Shih 2004 186 186 9 Shih 2004 41 41 9 Joshi 2003 110 25 10 Cloutier 2001 163 107 10 Ewald 1999 539 306 10 Duffy 1998 61 55 10 Duffy 1998 59 51 10 Pooled outcome 7-10-year mean follow-up Rodriguez 1996 145 104 13 Miyasaka 1996 108 60 14 Goldberg 2004 124 98 14 Sextro 2001 168 66 16 Gill 2000 254 116 17 Pooled outcome 13-17-year mean follow-up
75 69 71 65 65 84 67 63 54 65
80% 81% NR 89% 89% 69% 74% NR 50% 51%
100% 0% 100% 100% 100% 100% 75% 46% 76% 82%
28 21 44 68 67 40 33 42 33 32
52 61 62 65 68
88% 85% 51% 61% 65%
0% 35% 100% 65% 100%
NR 28 31 33 39
87 77 91 91 90 86 91 82 88 92 86 * NR 89 91 88 90 90 *
53 40 45 61 58 39 44 37 52 45
66 65 75 89 87 51 82 68 66 72 81 * 55 69 85 51 58 74 *
28 30 28 49 44
* Not significant.
Table 3. Survivorship—LCS Knees Implanted in 1981 to 1997 and Swedish Knee Registry Knees Implanted in 1991 to 1995 Ref
Author
Bearing No. of Type Knees 2 y
LCS with rotating platform 28 Sorrells Rotating RB, platform 18 Huang C Rotating platform 2 Callaghan Rotating J platform 29 Stiehl Rotating platform 26 Buechel F Rotating platform 31 Tarkin I Rotating platform Pooled survivorship with rotating platform % Estimated upper confidence interval Estimated lower confidence interval All Knees Sweden 1991-1995 Estimated upper confidence interval Estimated upper confidence interval * Not significant. † Significant.
Survivorship % 5y
6y
7y
8y
9y
10 y
12 y
14 y
15 y
16 y
17 y
18 y
Date of 20 y Implantation
528
96
96
95.5
95.5
95
94
93
89.5
1984-1994
322
99
99
99
99
98.5
98
97
95.5
92.1
92.1
119
100
100
100
99
98
98
98
98
98
96.5
2254
98.5
97.5
97
96
95.5
95
94
90
88
169
100
100
100
100
98.3
98.3
98.3
98.3
98.3
98.3
98.3
98.30 98.3
1981-1990
70
96
96
95
93
87
87
87
85
80
76
76
75
1984-1986
3462
98.8 * 98.4 * 98.1 * 98.1† 96.8 * 96.3 * 95.6 * 94.1 * 93.9 * 95.6 * 97.7 * 97.7 * 97.7 * 96.5 * 1981-1997
1985-1990 96.5
96.5
96.5
96.5
1985-1988 1981-1997
99.5
99.3
99.2
99.2
98.1
97.8
97.2
96.8
97.7
97.4
99.4
99.4
99.4
99.3
97.2
96.4
95.8
95.8
94.5
94.0
93.1
89.0
84.8
92.5
91.7
91.7
91.7
84.4
97.8 * 96.5 * 95.8 * 95.2† 95.0 * 94.8 * 94.5 * 93.5 * 93.0 * 92.8 * 92.0 * 92.0 * 91.2 * 98.3
97.0
96.3
95.7
95.5
95.3
95.0
94.0
93.8
93.6
92.8
92.8
92.5
97.3
96.0
95.3
94.7
94.5
94.3
94.0
93.0
92.3
92.1
91.3
91.3
89.9
1991-1995
