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High rate of tibial debonding and failure in a popular knee replacement: A cause for concern
THEKNE-02907; No of Pages 10 The Knee xxx (xxxx) xxx
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The Knee
High rate of tibial debonding and failure in a popular knee replacement: A cause for concern David Keohane a,⁎, Fiachra Power a, Emmet Cullen a, Aoife O'Neill b, Eric Masterson a a b
Department of Orthopaedics, University Hospital Limerick, Limerick, Ireland Department of Biostatistics, University of Limerick, Limerick, Ireland
a r t i c l e
i n f o
Article history: Received 11 November 2018 Received in revised form 27 June 2019 Accepted 2 October 2019 Available online xxxx
a b s t r a c t Background: Total knee arthroplasty (TKA) is a common orthopedic procedure with 975,739 performed in the UK between 2003 and 2016. The two most common prosthetics used are P. F.C. Sigma and NexGen. The aim of this study is to compare the experience of a single fellowship-trained arthroplasty surgeon at a single dedicated orthopedic hospital using both of these prosthetics over a 17-year period. Methods: This study was carried out as a retrospective review. Information was gathered from a database of primary TKAs and revision TKAs, as well as medical records, correspondence and operative notes. Results: A total of 1,511 TKAs were performed between 1999 and 2015 – with a further followup period of 2 years. There were 1,161 consecutive P.F.C. primary TKAs done from 1999 to April 2013, after which, 350 consecutive NexGen primary TKAs were performed. Between 2015 and 2017, 26 NexGen revisions were required. 23 (6.6%) of the NexGen knees were carried out for aseptic loosening. The average time for revision from the NexGen index surgery was 30.4 months. The failures all presented similarly – with the tibial component having collapsed into varus and radiographic lucency noted under the implant. Conclusion: In spite of changes in orthopedic practice and advances in implant technology over the time period of this study, we would not expect this level of implant failure from a surgeon who had no previous significant issues with aseptic loosening using a different prosthetic. Usage of the NexGen knee has been discontinued at this center. © 2019 Elsevier B.V. All rights reserved.
1. Background Total Knee Arthroplasty (TKA) is a common orthopedic procedure, which is illustrated by the fact that there were 975,739 performed in the UK between 2003 and 2016 [1] and more than 1500 done in 2016 in Ireland [2]. According to the UK National Joint Registry report for 2016; 133,343 of these TKAs were NexGen knees — making it the second most implanted brand of knee prosthesis used in the UK after the Press Fit Condylar (P.F.C.) Sigma Bicondylar Knee [1]. Over 96% of all primary TKAs are done for the purpose of pain relief in patients suffering from osteoarthritis of the knee [1]. Surgical intervention is, for the most part, only considered when pain has progressed despite the best efforts of conservative and medical management. TKA is an effective treatment option with significant improvements seen in pain and mobility in the majority of patients. However, complications or implant failures can arise necessitating revision surgery. There were 24,399 revisions of a knee prosthesis performed between 2003 and 2016 in the UK [1]. This equates to 1,000,138 primary and revision procedures done over this 14-year period. Therefore, revisions made up 2.4% of all knee procedures re-
⁎ Corresponding author. E-mail addresses: [email protected], (D. Keohane), [email protected]. (A. O'Neill).
https://doi.org/10.1016/j.knee.2019.10.001 0968-0160/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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corded. There is a 0.40%, 1.52%, 2.17%, and 3.39% probability risk of undergoing a revision TKA within one, three, five, and 10 years, respectively, post index surgery [1]. This headline revision rate is representative of all TKAs performed and specific revision rates vary according to demographic and patient-related factors. Patient age at the time of index surgery has been shown to be a significant factor with regard to the need for future revision TKA [1]. Younger patients are more likely to have a higher level of physical activity post-operatively and to survive reaching the lifetime expectancy of the prosthesis. For example, a male under 55 years of age has a near 12% cumulative risk of requiring a revision in a 13-year post-operative period whereas an 80-year-old has a less than 1.5% chance of requiring revision arthroplasty over the same period [1]. The reported NexGen revision rates are 0.38%, 1.42%, and 2.15% at one, three, and five years, respectively [1]. Specifically, the NexGen Posterior Stabilized Fixed (cemented) has revision rates of 0.44%, 1.61%, and 2.54% at years one, three, and five [1]. A variety of reasons for failure of TKA have been described in the literature including infection, aseptic loosening, pain, instability, implant wear, mal-alignment, osteolysis, dislocation, peri-prosthetic fracture, and implant fracture [1]. Infection is the most common cause of failure in the first year (1.64 per 1000 patient years). For every subsequent year, however, the main cause is aseptic loosening (1.27 per 1000 patient years) [1]. The NexGen LPS/LPS-Flex knee system (Zimmer Biomet; Warsaw, IN) was introduced to the market in 1995 as a successor to the Insall-Burstein and Miller-Galante knee systems. The Miller-Galante implants were routinely supplied with a Polymethyl Methacrylate (PMMA) pre-coat. Therefore, the NexGen tibial baseplate was offered with and without pre-coat options. According to a personal communication between the lead author and a representative of Zimmer Biomet, approximately four million NexGen knees have been implanted worldwide from 2004 to 2018 — 81% of these have been with pre-coated tibial trays and 19% were non-coated tibial trays. The UK National Joint Registry (NJR) does not analyze pre-coated and non-pre-coated tibial baseplates separately. A study published by Bini et al. in 2013 looked at the rate of aseptic revision between pre-coated and non-pre-coated NexGen tibial baseplates. Their study covered 16,548 primary NexGen TKAs over a nine-year period [3]. Eighty-four percent of the TKAs used a pre-coated tibial baseplate with the remaining 16% using a non-pre-coated baseplate [3]. The pre-coated baseplate had a revision rate of 0.12% for aseptic loosening versus a rate of 0% for the non-pre-coated baseplate [3]. There is no published English language literature reporting a benefit to using a PMMA pre-coat on the tibial baseplate. The specific tibial baseplate used in this study, as part of the LPS-Flex knee system implanted, was the “NexGen Stemmed Nonaugmentable Tibial Component Option”. This component is not compatible with a stem extension and does not have a PMMA pre-coat. It is made from wrought titanium (Ti-6Al-4V) alloy. The P.F.C. Sigma tibial baseplate used in this study also does not have a PMMA pre-coat option meaning neither tibial baseplates used in this study had a PMMA pre-coat. Prior to 2005, the PFC tibial baseplate was made of titanium, but a cobalt chrome plate was introduced that year and was subsequently used in this study. Both NexGen and P.F.C. introduced a cross-linked polyethylene component over the time period covered by this study. This paper describes the experience of a single surgeon using the P.F.C. and the NexGen LPS Flex knee system over a 17-year period. 2. Methods A retrospective single surgeon review of all of the TKAs using the NexGen LPS system and the P.F.C. Sigma Posterior Cruciate Ligament (PCL) Substitute system was undertaken. All index cases were performed by, or under the direct supervision of, a single fellowship trained arthroplasty surgeon in a dedicated specialist orthopedic hospital in Ireland — this ensured a consistent standard for each procedure. A prospectively maintained database of primary TKAs was accessed for relevant case information, and a second database relating to revision NexGen TKAs was also interrogated. Of the 26 NexGen revisions, the lead surgeon did 24. Another surgeon performed the remaining two. Additional information was sourced from medical records, correspondence, original operative notes, and from a review of patient radiographs. The national Hospital Inpatient Enquiry (HIPE) database was queried to identify every revision that was done over this time period by the lead surgeon. Between January 1999 and December 2015, 1570 index TKAs were performed by the lead author — as per Table 1. The P.F.C. Sigma PCL Substitute was used almost exclusively between January 1, 1999 and April 15, 2013 and a total of 1161 cases were done during this period. From April 17, 2013 to December 31, 2015, the Zimmer NexGen Complete was then used almost exclusively, and a total of 350 cases were done in this time. The decision to change from the P.F.C. to the NexGen was not made because of any concerns about the performance of the P.F.C. prosthetic. The published results of the P.F.C. and the NexGen were both excellent. The change was prompted by changes in the distributorships of the implants in Ireland.
Table 1 Total volume of TKAs performed from January 1999 to December 2015 by implant system. Knee system
Number of cases
P.F.C. Sigma PCL Substitute Zimmer NexGen Complete Other Total
1161 (74%) 350 (22%) 59 (4%) 1570
Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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The total number of patients included in this cohort is 1266. This equates to 1511 index TKAs (1161 [76.8%] P.F.C. and 350 [23.2%] NexGen) carried out between January 1999 and December 2015. The demographic split of these patients is presented in Table 2. There were insufficient numbers of the other implant types performed by the lead surgeon to make a meaningful comparative analysis. A median para-patellar approach was used from 1999 to 2010. A subvastus approach was used in all primary procedures from 2010 onwards — this approach is used as it is quadriceps sparing, it is associated with less post-operative pain and faster patient recovery. The tibia was prepared with a 16.7-mm cemented stemmed tibial drill and tibial broach impactor as per the manufacturers recommended surgical technique. Palacos cement, which is high viscosity, was used in all cases with both prosthetics. The manufacturer recommends separate mixes of cement for the femur and the tibia; however, we only used a single mix. The cementing technique employed was identical for the P.F.C. and the NexGen implants, and had been successfully employed for the P.F.C. knee over the previous 15 years. This involved applying cement to the cut surface of the tibia and digital pressurization of cement into the intra-medullary canal. No cement was applied directly to the undersurface of either tibial component. This is consistent with the cementing guidelines for the P.F.C. knee. The original surgical guidelines for the NexGen knee gave no specific instructions as to the preferred cementing technique. Current guidelines suggesting application of cement to the undersurface of the tibial component were only produced at a later date. There was minimal variation in the surgical times. A standardized post-operative care pathway for knee arthroplasty was followed for all patients. Plain film radiographs were obtained and reviewed by the lead surgeon on post-operative day one to allow for assessment of prosthesis position and to out-rule occult peri-prosthetic fractures (note: full-length limb x-rays are not done as standard post-operatively). The General Practitioner (GP) removed the surgical clips between 10 and 14 days post-op, and the patient is brought back for clinical review six weeks post-operatively. If no issues were identified, patients were discharged to their GP. Nurse specialists follow up with patients two years after their surgery. For this research, all of the original day-one post-operative x-rays for the patients that required revisions for aseptic loosening were retrospectively reviewed by an independent consultant radiologist in conjunction with the lead author. Descriptive statistics were carried out on data at the patient level and also using the operation as the unit of analysis. Categorical data were described as counts and percentages. Continuous data were described using means and standard deviations. Differences in clinical and demographic variables by ‘knee type’ (NexGen and P.F.C. sigma) and ‘revision required’ (yes, no) were tested using Pearson's Chi-square tests for categorical variables and independent sample t-tests for continuous data. Kaplan–Meier estimates of survival and survival curves were used to account for varying lengths of follow-up for patients. The total time period of analysis was from January 1, 1999 to December 31, 2017 (note: for this study, no index TKAs carried out after December 2015 were included but a further two-year period was granted for follow-up of index procedures), with the event of interest being requiring a revision surgery in that time period. Cox regression analysis was used to further investigate the risk of revision by knee type (controlling for age). A 5% level of significance was used for all statistical tests. Cramer's V and Cohan's D effect sizes were used to measure the size of the effect, with v = 0.1 representing a small effect, 0.3 medium, and 0.5 large for Cramer's V and d = 0.2 representing a small effect, 0.5 medium, and 0.8 large for Cohan's D. All statistical analysis was undertaken using SPSS Version 22 and R software. 3. Results Of the 1511 primary TKAs, 35 (2.3%) required revision — regardless of cause. Demographic differences between those who required a revision and those who did not are presented in Table 3. There was a statistically significant difference in age between the non-revision and revision groups (p ≤ .001) — with those who had a revision being younger on their index procedure date (62.8 years at operation compared to 68.7 years). There was no statistically significant difference in the male/female breakdown when both groups were compared against one another (p = .92), or the left/right/bilateral operation type breakdown when both groups were compared (p = .75). A total of 1161 P.F.C. Sigma PCL Substitute TKAs were included in this study for comparative failure rate analysis. Nine failures of this implant were noted when the index procedure occurred between January 1, 1999 and December 31, 2015, with an additional two years for follow-up — resulting in 10 revision procedures. Two of these related to peri-prosthetic fractures and one case related to septic arthritis requiring a two-stage revision. This left six (0.5%) cases of aseptic loosening of the implanted prosthetic. The lead author performed a total of 350 NexGen TKAs between April 2013 and December 2015 — 26 of which were revised as of December 31, 2017. Of these 26 revisions, three had biopsy and swab confirmed septic arthritis of the replaced knee joint (one Table 2 Descriptive statistics on patients (n = 1266 patients). N (%)⁎ Sex Had two separate joints operated on Age (at end of study)
Males Females No Yes (different date) Yes (same date)
528 (41.7%) 738 (58.3%) 1021 (80.6%) 205 (16.2%) 40 (3.2%) 76.7 (10.9)
⁎ Except age, where mean (SD) are presented
Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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Table 3 Demographic and operation type by revision (n = 1511 operations).
Sex Age (at op. date) Operation Type
Males Females Mean (SD) Right Left Bilateral
Total N = 1511 (%)
No revision N = 1476 (97.7%)
Revision N = 35 (2.3%)
617 (40.8%) 894 (59.2%) 68.6 (9.3 years) 787 (52.1%) 684 (45.3%) 40 (2.6%)
603 (40.9%) 873 (59.1%) 68.7 (9.3 years) 771 (52.2%) 666 (45.1%) 39 (2.6%)
14 (40.0%) 21 (60.0%) 62.8 (9.5 years) 16 (45.7%) 18 (51.4%) 1 (2.9%)
p-Value (effect size⁎) 0.92 (0.003) b0.001 (0.63) 0.75 (0.02)
⁎ Cramer's V effect size, except age where Cohen's D was used.
of these patients had a history of septic arthritis post previous arthroscopy). This gives a total of 23 (6.6%) revisions for aseptic loosening out of 350 implanted NexGen knees. This gives us a total of 35 (2.3%) patients requiring a revision for all causes, and 29 (1.9%) patients requiring a revision for aseptic loosening out of a total cohort of 1511 patients. Differences in demographics and clinical variables by knee type are presented in Table 4. There was a statistically significant difference in rates of revision between the two knee types (p b .001), with those given a NexGen knee more likely to require a revision (7.4% compared to 0.8% for P.F.C. sigma knees). There was no statistically significant difference in the male/female breakdown per knee type when the two groups were compared against each other. Similarly, there was no statistically significant difference in age between the two groups. There was a statistically significant difference between the two groups by split of operation type, but this is due to the higher number of bilateral procedures that were done in the P.F.C. group versus the NexGen group (3.2% versus 0.9%). The months of follow-up are significantly short in NexGen knee over the P.F.C. knee as it was used more recently (mean of 38.2 months vs. 126.8 for P.F.C., p b .001). 3.1. Survival analysis — Kaplan–Meier estimate of survival There was a high level of censoring due to only 35 patients requiring revision surgery out of the total 1511 knee operations. The date of one of the revisions was unknown and thus was not included in the survival analysis. Figure 1 shows the probability of knee failure for both NexGen knees and P.F.C. sigma knees. It can be seen that although NexGen has not been in use as long as P.F.C., there is a lower probability of surviving without revision for this knee type in comparison to P.F.C. sigma knees. 3.2. Survival analysis — Cox regression analysis Cox regression analysis was used to further explore the survival rate of the knee types, accounting for age (Table 5). Those with NexGen knees were more likely to require revision (adjusted hazard ratio [HR] = 30.2, 95% confidence interval [CI] = 10.3, 88.7) in comparison to patients receiving a P.F.C. knee. Older age at initial operation was associated with being less likely to require revision (Table 5). 3.3. Aseptic loosening of NexGen patients The demographics of the total NexGen knee type and the 23 aseptic loosening revision cohort are presented in Table 6. The average time from the primary procedure to revision for aseptic loosening for the 22 NexGen knees (unknown date of one aseptic revision so it was excluded) was 30.4 months. The retrospective review of all of the day-one post-operative x-rays for patients who went on to develop aseptic loosening did not show any issues with implant position, prosthetic alignment, or cement (note: standing full-length images were not available, Table 4 Demographics, operation type, and revision by knee type (n = 1511 operations).
Sex Age (at Operation date) Operation Type Revision Months of follow-up
Males Females Mean (SD) Right Left Bilateral No Yes Mean (SD)
Total N = 1511 (%)
P.F.C. Sigma PCL substitute N = 1161 (%)
Zimmer NexGen N = 350 (%)
617 (40.8%) 894 (59.2%) 68.6 (9.3 years) 787 (52.1%) 684 (45.3%) 40 (2.6%) 1476 (97.7%) 35 (2.3%) 106.3 (56.2 months)
460 (39.6%) 701 (60.4%) 68.7 (9.3 years) 611 (52.6%) 513 (44.2%) 37 (3.2%) 1152 (99.2%) 9 (0.8%) 126.8 (47.6 months)
157 (44.9%) 193 (55.1%) 68.2 (9.4 years) 176 (50.3%) 171 (48.9%) 3 (0.9%) 324 (92.6%) 26 (7.4%) 38.2 (9.7 months)
p-Value (effect size⁎) 0.08 (0.05) 0.36 (0.06) 0.03 (0.09) b0.001 (0.19) b0.001 (2.58)
⁎ Cramer's V effect size, except age and months where Cohen's D was used.
Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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Figure 1. Kaplan Meier estimate of survival.
however the medial distal femoral angle [MDFA] and medial proximal tibial angle [MPTA] were noted as being satisfactory with neutral alignment in the coronal plane). All of these patients were discharged from routine orthopedic care, and their early recovery was satisfactory. Patients typically started to experience symptoms of medial tibial pain with supra-patellar swelling from a combination of effusion and synovial thickening. Symptoms typically commenced at 12 to 24 months post-operatively. Inflammatory markers were normal in all cases, and no case required pre-operative aspiration. Radiographs of symptomatic knee replacements initially showed subtle bone loss on the medial tibia with a tilt of the tibial component always into a varus alignment. This tilt into varus became more obvious as time progressed. The cement mantle surrounding the stem of the tibial implant remained firmly bonded to bone in all cases. There were however small fractures in the cement on the medial side of the stem, which allowed it to tilt into varus. Figure 2 contains a set of four images for the same patient. The top row illustrates day-one post-operative anterioposterior and lateral images of a typical TKA who subsequently developed aseptic loosening of the tibial component. This radiograph demonstrates an intact cement mantle (both under the tibial component and around the keel), neutral coronal alignment, and no positioning issue with the prosthetics. The bottom row illustrates the same knee pre-revision. While no full-limb images were taken after the index surgery or prior to the revision surgery (which is a limitation of the study), an obvious varus deformity is demonstrated between the femoral and tibial components in the TKA. The tibial component has collapsed medially with lucency noted under the lateral aspect. These images were taken no more than six weeks before the revision procedure.
3.4. Intra-operative findings at the time of revision TKA In all cases, the tibial component was loose and could be removed without instrumentation. This is illustrated in Figure 3. The third image in Figure 3 illustrates an intact cement mantle after removal of the tibial component. In a subset of cases, a small volume of cement was still attached to some aspect of the undersurface of the tibial component. Intra-operative deep tissue biopsies and culture swabs were negative for any growth.
Table 5 Adjusted risk of revision for all patients (n = 1161).
Age – ≥65 years - b65 years Knee type – NexGen - P.F.C. sigma
Hazard ratio (95% CI)
p-Value
0.26 (0.13, 0.52) reference
b0.001
30.2 (10.3, 88.7) reference
b0.001
Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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Table 6 Breakdown of NexGen primary and revision cohort by gender, op. side and age.
Gender Operation Type
Male Female Left Right Bilateral
Mean age at operation (SD) Time from index surgery to revision in months (SD)
Total NexGen (n = 350)
Aseptic loosening revision group (n = 23)
157 (45%) 193 (55%) 170 (48%) 177 (51%) 3 (1%) 68.2 (9.4) N/A
9 (39%) 14 (61%) 16 (70%) 7 (30%) N/A 61.9 (7.8) 30.4 (9.7)⁎
⁎ Values for 22 revisions for aseptic loosening where revision date is known.
4. Discussion As per the UK NJR, infection/septic arthritis is the most common cause of revision in the first year following TKA with aseptic loosening being both the second most common cause in the first year and the leading overall cause for revision overall [1]. This is consistent with the findings of Schorer et al. and Sharkey et al. who also examined the etiology of revision TKAs, and confirmed that aseptic loosening is the most common cause overall [4] [5]. While our overall all-cause revision rate of 2.3% is in line with the UK revision rate of 2.4% [1] — our revisions are disproportionally skewed towards the smaller NexGen cohort of patients. We found that patients who are younger at the time of their index surgery are statistically more likely to require a revision than a patient who is older at the time of their index surgery. This finding is consistent with the UK NJR [1]. As per Table 4, there is a statistically significant difference in the number of all-cause revision operations between the two knee types (p b .001), with those given a NexGen knee more than nine times likely to require a revision for any cause (7.4% of NexGen TKAs required revision compared to 0.8% for P.F.C. TKAs). No differences in gender or age at operation were observed between the two knee types. There was aseptic loosening of the tibial component in 23 patients (6.6% of 350 NexGen TKAs) with an average revision time of 30.4 months. The femoral component had failed and required revision in one of these cases. This compares very unfavorably to all-cause revision figures of 0.44%, 1.61%, and 2.54% at years one, three, and five listed in the NJR for the NexGen Posterior Stabilized Fixed (cemented) knee [1]. Therefore, our NexGen cohort of 350 patients had an average failure rate of more than four times the expected rate at the three-year post-op point. While it would not be unexpected to see a small increase in the number of revisions required when a surgeons changes to a new implant with a new set of instruments due to the learning curve effect, we would not expect it to be this large. Also, we would expect to see the revisions front-loaded over the time period that the NexGen knee was used — which is not what we experienced. Out of our 23 patients who required a revision for aseptic loosening; six of them had their primary procedure in 2013, 10 of them in 2014, and seven of them in 2015. The lead author's role in every one of this study's TKAs ensured a consistent operative standard and the appropriate surgical approach. Between 2005 and 2017, the lead author performed a total of 103 TKA revisions — averaging eight per year. Out of these 103 procedures, the lead author performed the primary TKA in 52 of them. Out of this 52, nine were conversions of unicondylar knees to full TKA. Twenty-six of these procedures were on NexGen knees. Therefore, the lead author only performed 17 revision procedures on 14 non-NexGen knees (which includes the 10 revision procedures on nine P.F.C. knees in this paper) over a 13-year time period when he performed the primary TKA — giving a revision rate of less than two procedures per year. This includes revisions for traumatic peri-prosthetic fractures, two-stage revisions for septic arthritis, and other revision causes. The revision rate increased significantly once he started using the NexGen knee — 15 NexGen knees were revised in 2017 for aseptic loosening. This increase in revision rate has led the lead author to cease use of the NexGen knee. Orthopedics has changed in many ways from when the lead surgeon started using the P.F.C. prosthetic in 1999 to the present day. The changes in surgical technique over the years by the lead surgeon include a move from medial parapatellar to subvastus approach in 2010, the use of peri-articular local anesthetic for post-operative pain control since 2011 and the retention of the infrapatellar fat pad since 2015. None of these could be expected to contribute to pre-mature tibial component failure. No changes in typical patient profile were noted over the duration of the study. While there have been improvements to manufacturing techniques and materials used in orthopedics over the years covered by this study, such as the use of ceramic femoral components or different alloys like zirconium, we do not believe that this played a role in what we see in this study. Personal communications with NexGen have confirmed that manufacturing techniques such as machining from the raw material forging and applying the grit blast undersurface have remained the same over this time period. They also confirmed that there have been no changes to the specifications related to the blast surface on the underside of the tibial component. Personal communications with P.F.C. confirmed that they updated their manufacturing technique in 2005 to accommodate new cobalt chromium tibial trays and a new locking mechanism on the tibial tray for the polyethylene. There were no changes to the undersurface of the tibial component — including the stem, the keel or the finish [6]. Both of these companies introduced crosslinked polyethylene inserts in the mid-2000s which are now used as standard. We would not expect these to be contributing factors to aseptic loosening of the tibial components. Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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Figure 2. (Top Row) Day 1 Post-operative AP and lateral images of TKA; (Bottom Row) Pre-revision AP and lateral images of TKA.
Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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Figure 3. Intra-operative images of the removal of the tibial baseplate with an intact cement mantle remaining.
Other authors have identified increased rates of tibial loosening with the NexGen knee. Arsoy et al. reported aseptic loosening of the tibial component in 25 (1.9%) of their patients, with a median time to revision of 39 months [7]. In total, they implanted 1337 NexGen knees, using the three-degree-fluted (no PMMA pre-coat) tibial component [7] (launched in 2001). They reported five-year survivorship free of revision for any reason of 95.1%, and five-year survivorship free from tibial debonding of 97.8% [7]. Their five-year revision figure for aseptic debonding (2.2%) was in line with the all cause revision figure reported in the NJR (2.54%), and their all-cause revision figure at five years (4.9%) was nearly double the reported NJR figure (2.54%). Similarly, Foran et al. had a cohort of 529 TKAs using the NexGen knee, specifically the Minimally Invasive Surgery (MIS) tibial component with an undersurface pre-coat of PMMA [8]. They reported aseptic loosening in 1.5% of their cohort of patients with a median time to revision of 17 months [8]. They make no mention of overall revision rate for their cohort of patients. Both of these reports document a similar pattern of failure to what we experienced — clinically, nearly all patients had a combination of either knee pain exacerbated by weight bearing (following a pain-free post-operative period) and/or joint effusions [7,8]. Radiographic findings were satisfactory post-op, but lucencies were observed on follow-up radiographs between the tibial component and cement — most commonly in the medial and/or lateral tibial plateau, with subsidence of the tibial component into varus deformity [7,8]. Intra-operatively, the tibial component was loose and did not require instrumentation to be removed [7,8] — and in some cases the PMMA pre-coat on the MIS tibial component was absent completely [8]. Research published by Bonutti et al. report similar tibial debonding issues with the Attune knee [9]. Their search for aseptic failure of TKAs, particularly tibial component loosening at the cement interface, from three hospital databases yielded 13 patients (15 knees) with a mean age of 61 years [9]. All of these patients presented with similar clinical findings and subsequently had the same intraoperative findings as our cohort of revision patients [9]. Radiographically, only two of their 15 knees had evidence of radiolucency [9]. However, it should be noted that Bonutti failed to identify the total number of cases included in the overall cohort, which is a limitation of the study. According to Sharkey et al. “Loosening of the prosthesis is related to TKA component fixation methodology” [4]; however, there is no agreement in the literature as to whether cemented or uncemented is the best fixation method for function and survival [10]. A separate paper by Hazelwood et al. attributes early aseptic loosening in 11 (0.36%) patients, out of a cohort of 3048, to the use of ‘High Viscosity Cement’ (HVC) [11]. All nine patients surveyed (note: two patient declined survey involvement) had similar presentations to what we experienced — clinically, radiographically, and intra-operatively [11]. Two of these failures used the Palacos cement that was used in our patient cohort. The other seven used other types of cement. A recent article by Billi et al. looked at techniques for strengthening the tibial tray-cement bond using Palacos and Simplex cement. It compared multiple different variables, but overall it found that cement should be applied early, contamination of the surface should be avoided and both the keel and plateau should be cemented [12]. As can be seen by the x-rays in Figure 2, the keel was cemented in our NexGen TKAs. The timing of the cement was significant — early cementing (using Palacos) increased the mean strength by 72%, whereas late cementing decreased mean strength by 73% [12]. One interesting, and potentially relevant finding, is that bone marrow contamination of cement-tray interface reduced the mean strength of the interface by up to Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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94% with Palacos cement [12], and it is recommended that cement be added to the undersurface of the tibial tray and around the keel in order to mitigate this risk. It should be noted that this finding was not statistically significant and was a result of in vitro testing. It may be relevant to our study as adding cement to the undersurface of the tibial component is part of the manufacturer guidelines for cementing the NexGen tibial component, although it is not a recommendation for the P.F.C. tibial component. It should also be noted that cement can clearly be seen around the keel of the NexGen tibial component in Figure 2 above. Our study, along with Arsoy et al. use the NexGen LPS knee system with a non-coated tibial baseplate, whereas Foran et al. use a PMMA pre-coated baseplate. The same clinical, radiographical, and intra-operative findings were seen consistently in all three studies. Because of these findings, our concerns are focused on three areas: the tibial component itself, the cement (Palacos) used or the interaction at the tibial component-cement interface. From personal communication with a NexGen representative, we know that 81% of NexGen tibial components have a pre-coat with the remaining 19% not having a pre-coat. The registry data are not specific for pre-coated or non-pre-coated components. Our high revision rate of NexGen knees due to aseptic loosening only affects 19% of the overall NexGen volume meaning that the registry data may be somewhat misleading. As there are multiple published research articles dealing with tibial debonding and aseptic loosening across multiple NexGen tibial components, we can also hypothesize that there is an issue with the undersurface of the tibial tray and the cement mantle. At present, we are at a loss as to why we experienced these tibial issues. We followed the original cementing guidelines for the NexGen implant — although they were subsequently updated to include an extra cementing step. We believe that there are four subgroups that have not been analyzed on an individual basis: 1. Cement on bone only, no pre-coat on tibial component, 2. Cement on bone only, pre-coat on tibial component, 3. Cement on bone and the implant, no pre-coat on tibial component, and 4. Cement on bone and the implant, pre-coat on tibial component. This paper shows poor results for the first group with the NexGen knee. We believe that more research needs to be done on a detailed molecular level to assess this interaction between cement and component, particularly in relation to contamination with in vivo substances and the potential mitigation with adding of cement to the undersurface of the tibial component. We also believe more research needs to be done into micro-motion between the tibial tray and the cement mantle. The lead author was prompted to publish his results because of an unacceptably high rate of tibial component failures, which is at odds with much of the published data to date. 5. Strengths and limitations of this study Strengths of this research include that to the best of our knowledge, this is the first paper which compares two widely used prosthetic knee replacements where variables such as institution, surgeon, and surgical approach have been controlled as much as possible. There are several limitations to this study. Full-length limb x-rays were not done post-operatively after the primary procedure or pre-operatively before the revision. These would be necessary to confirm limb alignment and to categorically rule out any potential limb deformity. It should be noted that the femur was instrumented when the original femoral cuts were made — which would be difficult if a femoral deformity was present. An extra-medullary jig was used to align the tibial component to the ankle — again, making a tibial deformity unlikely. This paper was written retrospectively when the high rate of failure rate was noticed — therefore, it is limited by the imaging that already exists for the cohort of patients and the data that were captured about the procedure at the time of the procedure. The cohort of NexGen knees is smaller than the P.F.C. cohort — however, because of the high failure rate experienced, it was not prudent to continue using this prosthetic. As this paper was written retrospectively, there was no dedicated follow-up for individual patients; therefore, all individuals were assumed to be alive at the end of the study, and no account for deaths were made. Another limitation is that we are assuming that all of the patients in which the index procedure was done by the lead surgeon was referred back to the same lead surgeon when they experienced issues with their prosthetic — it is highly likely that there are patients that were referred to a different surgeon for which we have no visibility or knowledge. This means that we have potentially underestimated the number of knees affected both with the P.F.C. and the NexGen implants. We are also assuming that the index TKA database we are using is complete, and that the HIPE data extracted on TKA revisions are accurate. We acknowledge the fact that this is a widely used prosthetic that has been on the market for over 20 years with no similar excessively high failure rate in the published literature to date. We also acknowledge that the NexGen Option tibial baseplate has a positive Orthopedic Data Evaluation Panel (ODEP) rating [13]. We do, however, note that the registry data does not differentiate between pre-coated and non-pre-coated tibial components — which may potentially explain our results. 6. Conclusion In conclusion, we are left in a situation whereby an experienced arthroplasty surgeon had an unacceptably high rate of tibial component failure that was at variance with published results of this device. This failure rate resulted in use of the prosthetic being discontinued at our hospital. Surgical technique was as per manufacturer's recommendations with the exception that cement was only put on the bony surface and not on the implant. Perhaps this is a contributing factor. It also highlights the need for arthroplasty registries to separately analyze the results of pre-coated and non-pre-coated devices to see if this is a factor. Since returning to the P.F.C. prosthetic in 2016, the lead author has had no new instances of tibial failure with it. Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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Acknowledgments We would like to acknowledge the staff at University Hospital Limerick and Croom orthopedic hospital for their assistance in retrieving archived patient charts.
Funding source No funding was received for this work, and the authors have no financial interest in its publication.
References [1] Registry UNJ. NJR 14th annual report. http://www.njrreports.org.uk/Portals/0/PDFdownloads/NJR%2014th%20Annual%20Report%202017.pdf; 2017. [UK National Joint Registry; 2017]. [2] Executive HS. Knee replacement. http://www.hse.ie/eng/health/az/K/Knee-replacement/Recovering-from-a-knee-replacement.html; 2017. [3] Bini SA, Chen Y, Khatod M, Paxton EW. Does pre-coating total knee tibial implants affect the risk of aseptic revision? Bone Joint J 2013;95-B(3):367–70. [4] Sharkey PF, Lichstein PM, Shen C, Tokarski AT, Parvizi J. Why are total knee arthroplasties failing today–has anything changed after 10 years? J Arthroplasty 2014; 29(9):1774–8. [5] Schroer WC, Berend KR, Lombardi AV, Barnes CL, Bolognesi MP, Berend ME, et al. Why are total knees failing today? Etiology of total knee revision in 2010 and 2011. J Arthroplasty 2013;28(8 Suppl):116–9. [6] DePuy. DePuy sigma fixed bearing brochure. DePuy; 2010 Available from: http://synthes.vo.llnwd.net/o16/LLNWMB8/US Mobile/Synthes North America/Product Support Materials/Brochures/DPY_Sigma_Fixed_Bearing_Brochure_0612-65-508.pdf. [7] Arsoy D, Pagnano MW, Lewallen DG, Hanssen AD, Sierra RJ. Aseptic tibial debonding as a cause of early failure in a modern total knee arthroplasty design. Clin Orthop Relat Res 2013;471(1):94–101. [8] Foran JR, Whited BW, Sporer SM. Early aseptic loosening with a precoated low-profile tibial component: a case series. J Arthroplasty 2011;26(8):1445–50. [9] Bonutti PM, Khlopas A, Chughtai M, Cole C, Gwam CU, Harwin SF, et al. Unusually high rate of early failure of tibial component in ATTUNE total knee arthroplasty system at implant-cement interface. J Knee Surg 2017;30(5):435–9. [10] Gandhi R, Tsvetkov D, Davey JR, Mahomed NN. Survival and clinical function of cemented and uncemented prostheses in total knee replacement: a meta-analysis. J Bone Joint Surg Br 2009;91(7):889–95. [11] Hazelwood KJ, O'Rourke M, Stamos VP, McMillan RD, Beigler D, Robb WJ. Case series report: early cement-implant interface fixation failure in total knee replacement. Knee 2015;22(5):424–8. [12] Billi F, Kavanaugh A, Schmalzried H, Schmalzried TP. Techniques for improving the initial strength of the tibial tray-cement interface bond. Bone Joint J 2019;101B(1_Supple_A):53–8. [13] ODEP. Orthopaedic data evaluation panel. http://www.odep.org.uk/product.aspx?pid=43412019.
Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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The Knee
High rate of tibial debonding and failure in a popular knee replacement: A cause for concern David Keohane a,⁎, Fiachra Power a, Emmet Cullen a, Aoife O'Neill b, Eric Masterson a a b
Department of Orthopaedics, University Hospital Limerick, Limerick, Ireland Department of Biostatistics, University of Limerick, Limerick, Ireland
a r t i c l e
i n f o
Article history: Received 11 November 2018 Received in revised form 27 June 2019 Accepted 2 October 2019 Available online xxxx
a b s t r a c t Background: Total knee arthroplasty (TKA) is a common orthopedic procedure with 975,739 performed in the UK between 2003 and 2016. The two most common prosthetics used are P. F.C. Sigma and NexGen. The aim of this study is to compare the experience of a single fellowship-trained arthroplasty surgeon at a single dedicated orthopedic hospital using both of these prosthetics over a 17-year period. Methods: This study was carried out as a retrospective review. Information was gathered from a database of primary TKAs and revision TKAs, as well as medical records, correspondence and operative notes. Results: A total of 1,511 TKAs were performed between 1999 and 2015 – with a further followup period of 2 years. There were 1,161 consecutive P.F.C. primary TKAs done from 1999 to April 2013, after which, 350 consecutive NexGen primary TKAs were performed. Between 2015 and 2017, 26 NexGen revisions were required. 23 (6.6%) of the NexGen knees were carried out for aseptic loosening. The average time for revision from the NexGen index surgery was 30.4 months. The failures all presented similarly – with the tibial component having collapsed into varus and radiographic lucency noted under the implant. Conclusion: In spite of changes in orthopedic practice and advances in implant technology over the time period of this study, we would not expect this level of implant failure from a surgeon who had no previous significant issues with aseptic loosening using a different prosthetic. Usage of the NexGen knee has been discontinued at this center. © 2019 Elsevier B.V. All rights reserved.
1. Background Total Knee Arthroplasty (TKA) is a common orthopedic procedure, which is illustrated by the fact that there were 975,739 performed in the UK between 2003 and 2016 [1] and more than 1500 done in 2016 in Ireland [2]. According to the UK National Joint Registry report for 2016; 133,343 of these TKAs were NexGen knees — making it the second most implanted brand of knee prosthesis used in the UK after the Press Fit Condylar (P.F.C.) Sigma Bicondylar Knee [1]. Over 96% of all primary TKAs are done for the purpose of pain relief in patients suffering from osteoarthritis of the knee [1]. Surgical intervention is, for the most part, only considered when pain has progressed despite the best efforts of conservative and medical management. TKA is an effective treatment option with significant improvements seen in pain and mobility in the majority of patients. However, complications or implant failures can arise necessitating revision surgery. There were 24,399 revisions of a knee prosthesis performed between 2003 and 2016 in the UK [1]. This equates to 1,000,138 primary and revision procedures done over this 14-year period. Therefore, revisions made up 2.4% of all knee procedures re-
⁎ Corresponding author. E-mail addresses: [email protected], (D. Keohane), [email protected]. (A. O'Neill).
https://doi.org/10.1016/j.knee.2019.10.001 0968-0160/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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corded. There is a 0.40%, 1.52%, 2.17%, and 3.39% probability risk of undergoing a revision TKA within one, three, five, and 10 years, respectively, post index surgery [1]. This headline revision rate is representative of all TKAs performed and specific revision rates vary according to demographic and patient-related factors. Patient age at the time of index surgery has been shown to be a significant factor with regard to the need for future revision TKA [1]. Younger patients are more likely to have a higher level of physical activity post-operatively and to survive reaching the lifetime expectancy of the prosthesis. For example, a male under 55 years of age has a near 12% cumulative risk of requiring a revision in a 13-year post-operative period whereas an 80-year-old has a less than 1.5% chance of requiring revision arthroplasty over the same period [1]. The reported NexGen revision rates are 0.38%, 1.42%, and 2.15% at one, three, and five years, respectively [1]. Specifically, the NexGen Posterior Stabilized Fixed (cemented) has revision rates of 0.44%, 1.61%, and 2.54% at years one, three, and five [1]. A variety of reasons for failure of TKA have been described in the literature including infection, aseptic loosening, pain, instability, implant wear, mal-alignment, osteolysis, dislocation, peri-prosthetic fracture, and implant fracture [1]. Infection is the most common cause of failure in the first year (1.64 per 1000 patient years). For every subsequent year, however, the main cause is aseptic loosening (1.27 per 1000 patient years) [1]. The NexGen LPS/LPS-Flex knee system (Zimmer Biomet; Warsaw, IN) was introduced to the market in 1995 as a successor to the Insall-Burstein and Miller-Galante knee systems. The Miller-Galante implants were routinely supplied with a Polymethyl Methacrylate (PMMA) pre-coat. Therefore, the NexGen tibial baseplate was offered with and without pre-coat options. According to a personal communication between the lead author and a representative of Zimmer Biomet, approximately four million NexGen knees have been implanted worldwide from 2004 to 2018 — 81% of these have been with pre-coated tibial trays and 19% were non-coated tibial trays. The UK National Joint Registry (NJR) does not analyze pre-coated and non-pre-coated tibial baseplates separately. A study published by Bini et al. in 2013 looked at the rate of aseptic revision between pre-coated and non-pre-coated NexGen tibial baseplates. Their study covered 16,548 primary NexGen TKAs over a nine-year period [3]. Eighty-four percent of the TKAs used a pre-coated tibial baseplate with the remaining 16% using a non-pre-coated baseplate [3]. The pre-coated baseplate had a revision rate of 0.12% for aseptic loosening versus a rate of 0% for the non-pre-coated baseplate [3]. There is no published English language literature reporting a benefit to using a PMMA pre-coat on the tibial baseplate. The specific tibial baseplate used in this study, as part of the LPS-Flex knee system implanted, was the “NexGen Stemmed Nonaugmentable Tibial Component Option”. This component is not compatible with a stem extension and does not have a PMMA pre-coat. It is made from wrought titanium (Ti-6Al-4V) alloy. The P.F.C. Sigma tibial baseplate used in this study also does not have a PMMA pre-coat option meaning neither tibial baseplates used in this study had a PMMA pre-coat. Prior to 2005, the PFC tibial baseplate was made of titanium, but a cobalt chrome plate was introduced that year and was subsequently used in this study. Both NexGen and P.F.C. introduced a cross-linked polyethylene component over the time period covered by this study. This paper describes the experience of a single surgeon using the P.F.C. and the NexGen LPS Flex knee system over a 17-year period. 2. Methods A retrospective single surgeon review of all of the TKAs using the NexGen LPS system and the P.F.C. Sigma Posterior Cruciate Ligament (PCL) Substitute system was undertaken. All index cases were performed by, or under the direct supervision of, a single fellowship trained arthroplasty surgeon in a dedicated specialist orthopedic hospital in Ireland — this ensured a consistent standard for each procedure. A prospectively maintained database of primary TKAs was accessed for relevant case information, and a second database relating to revision NexGen TKAs was also interrogated. Of the 26 NexGen revisions, the lead surgeon did 24. Another surgeon performed the remaining two. Additional information was sourced from medical records, correspondence, original operative notes, and from a review of patient radiographs. The national Hospital Inpatient Enquiry (HIPE) database was queried to identify every revision that was done over this time period by the lead surgeon. Between January 1999 and December 2015, 1570 index TKAs were performed by the lead author — as per Table 1. The P.F.C. Sigma PCL Substitute was used almost exclusively between January 1, 1999 and April 15, 2013 and a total of 1161 cases were done during this period. From April 17, 2013 to December 31, 2015, the Zimmer NexGen Complete was then used almost exclusively, and a total of 350 cases were done in this time. The decision to change from the P.F.C. to the NexGen was not made because of any concerns about the performance of the P.F.C. prosthetic. The published results of the P.F.C. and the NexGen were both excellent. The change was prompted by changes in the distributorships of the implants in Ireland.
Table 1 Total volume of TKAs performed from January 1999 to December 2015 by implant system. Knee system
Number of cases
P.F.C. Sigma PCL Substitute Zimmer NexGen Complete Other Total
1161 (74%) 350 (22%) 59 (4%) 1570
Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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The total number of patients included in this cohort is 1266. This equates to 1511 index TKAs (1161 [76.8%] P.F.C. and 350 [23.2%] NexGen) carried out between January 1999 and December 2015. The demographic split of these patients is presented in Table 2. There were insufficient numbers of the other implant types performed by the lead surgeon to make a meaningful comparative analysis. A median para-patellar approach was used from 1999 to 2010. A subvastus approach was used in all primary procedures from 2010 onwards — this approach is used as it is quadriceps sparing, it is associated with less post-operative pain and faster patient recovery. The tibia was prepared with a 16.7-mm cemented stemmed tibial drill and tibial broach impactor as per the manufacturers recommended surgical technique. Palacos cement, which is high viscosity, was used in all cases with both prosthetics. The manufacturer recommends separate mixes of cement for the femur and the tibia; however, we only used a single mix. The cementing technique employed was identical for the P.F.C. and the NexGen implants, and had been successfully employed for the P.F.C. knee over the previous 15 years. This involved applying cement to the cut surface of the tibia and digital pressurization of cement into the intra-medullary canal. No cement was applied directly to the undersurface of either tibial component. This is consistent with the cementing guidelines for the P.F.C. knee. The original surgical guidelines for the NexGen knee gave no specific instructions as to the preferred cementing technique. Current guidelines suggesting application of cement to the undersurface of the tibial component were only produced at a later date. There was minimal variation in the surgical times. A standardized post-operative care pathway for knee arthroplasty was followed for all patients. Plain film radiographs were obtained and reviewed by the lead surgeon on post-operative day one to allow for assessment of prosthesis position and to out-rule occult peri-prosthetic fractures (note: full-length limb x-rays are not done as standard post-operatively). The General Practitioner (GP) removed the surgical clips between 10 and 14 days post-op, and the patient is brought back for clinical review six weeks post-operatively. If no issues were identified, patients were discharged to their GP. Nurse specialists follow up with patients two years after their surgery. For this research, all of the original day-one post-operative x-rays for the patients that required revisions for aseptic loosening were retrospectively reviewed by an independent consultant radiologist in conjunction with the lead author. Descriptive statistics were carried out on data at the patient level and also using the operation as the unit of analysis. Categorical data were described as counts and percentages. Continuous data were described using means and standard deviations. Differences in clinical and demographic variables by ‘knee type’ (NexGen and P.F.C. sigma) and ‘revision required’ (yes, no) were tested using Pearson's Chi-square tests for categorical variables and independent sample t-tests for continuous data. Kaplan–Meier estimates of survival and survival curves were used to account for varying lengths of follow-up for patients. The total time period of analysis was from January 1, 1999 to December 31, 2017 (note: for this study, no index TKAs carried out after December 2015 were included but a further two-year period was granted for follow-up of index procedures), with the event of interest being requiring a revision surgery in that time period. Cox regression analysis was used to further investigate the risk of revision by knee type (controlling for age). A 5% level of significance was used for all statistical tests. Cramer's V and Cohan's D effect sizes were used to measure the size of the effect, with v = 0.1 representing a small effect, 0.3 medium, and 0.5 large for Cramer's V and d = 0.2 representing a small effect, 0.5 medium, and 0.8 large for Cohan's D. All statistical analysis was undertaken using SPSS Version 22 and R software. 3. Results Of the 1511 primary TKAs, 35 (2.3%) required revision — regardless of cause. Demographic differences between those who required a revision and those who did not are presented in Table 3. There was a statistically significant difference in age between the non-revision and revision groups (p ≤ .001) — with those who had a revision being younger on their index procedure date (62.8 years at operation compared to 68.7 years). There was no statistically significant difference in the male/female breakdown when both groups were compared against one another (p = .92), or the left/right/bilateral operation type breakdown when both groups were compared (p = .75). A total of 1161 P.F.C. Sigma PCL Substitute TKAs were included in this study for comparative failure rate analysis. Nine failures of this implant were noted when the index procedure occurred between January 1, 1999 and December 31, 2015, with an additional two years for follow-up — resulting in 10 revision procedures. Two of these related to peri-prosthetic fractures and one case related to septic arthritis requiring a two-stage revision. This left six (0.5%) cases of aseptic loosening of the implanted prosthetic. The lead author performed a total of 350 NexGen TKAs between April 2013 and December 2015 — 26 of which were revised as of December 31, 2017. Of these 26 revisions, three had biopsy and swab confirmed septic arthritis of the replaced knee joint (one Table 2 Descriptive statistics on patients (n = 1266 patients). N (%)⁎ Sex Had two separate joints operated on Age (at end of study)
Males Females No Yes (different date) Yes (same date)
528 (41.7%) 738 (58.3%) 1021 (80.6%) 205 (16.2%) 40 (3.2%) 76.7 (10.9)
⁎ Except age, where mean (SD) are presented
Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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Table 3 Demographic and operation type by revision (n = 1511 operations).
Sex Age (at op. date) Operation Type
Males Females Mean (SD) Right Left Bilateral
Total N = 1511 (%)
No revision N = 1476 (97.7%)
Revision N = 35 (2.3%)
617 (40.8%) 894 (59.2%) 68.6 (9.3 years) 787 (52.1%) 684 (45.3%) 40 (2.6%)
603 (40.9%) 873 (59.1%) 68.7 (9.3 years) 771 (52.2%) 666 (45.1%) 39 (2.6%)
14 (40.0%) 21 (60.0%) 62.8 (9.5 years) 16 (45.7%) 18 (51.4%) 1 (2.9%)
p-Value (effect size⁎) 0.92 (0.003) b0.001 (0.63) 0.75 (0.02)
⁎ Cramer's V effect size, except age where Cohen's D was used.
of these patients had a history of septic arthritis post previous arthroscopy). This gives a total of 23 (6.6%) revisions for aseptic loosening out of 350 implanted NexGen knees. This gives us a total of 35 (2.3%) patients requiring a revision for all causes, and 29 (1.9%) patients requiring a revision for aseptic loosening out of a total cohort of 1511 patients. Differences in demographics and clinical variables by knee type are presented in Table 4. There was a statistically significant difference in rates of revision between the two knee types (p b .001), with those given a NexGen knee more likely to require a revision (7.4% compared to 0.8% for P.F.C. sigma knees). There was no statistically significant difference in the male/female breakdown per knee type when the two groups were compared against each other. Similarly, there was no statistically significant difference in age between the two groups. There was a statistically significant difference between the two groups by split of operation type, but this is due to the higher number of bilateral procedures that were done in the P.F.C. group versus the NexGen group (3.2% versus 0.9%). The months of follow-up are significantly short in NexGen knee over the P.F.C. knee as it was used more recently (mean of 38.2 months vs. 126.8 for P.F.C., p b .001). 3.1. Survival analysis — Kaplan–Meier estimate of survival There was a high level of censoring due to only 35 patients requiring revision surgery out of the total 1511 knee operations. The date of one of the revisions was unknown and thus was not included in the survival analysis. Figure 1 shows the probability of knee failure for both NexGen knees and P.F.C. sigma knees. It can be seen that although NexGen has not been in use as long as P.F.C., there is a lower probability of surviving without revision for this knee type in comparison to P.F.C. sigma knees. 3.2. Survival analysis — Cox regression analysis Cox regression analysis was used to further explore the survival rate of the knee types, accounting for age (Table 5). Those with NexGen knees were more likely to require revision (adjusted hazard ratio [HR] = 30.2, 95% confidence interval [CI] = 10.3, 88.7) in comparison to patients receiving a P.F.C. knee. Older age at initial operation was associated with being less likely to require revision (Table 5). 3.3. Aseptic loosening of NexGen patients The demographics of the total NexGen knee type and the 23 aseptic loosening revision cohort are presented in Table 6. The average time from the primary procedure to revision for aseptic loosening for the 22 NexGen knees (unknown date of one aseptic revision so it was excluded) was 30.4 months. The retrospective review of all of the day-one post-operative x-rays for patients who went on to develop aseptic loosening did not show any issues with implant position, prosthetic alignment, or cement (note: standing full-length images were not available, Table 4 Demographics, operation type, and revision by knee type (n = 1511 operations).
Sex Age (at Operation date) Operation Type Revision Months of follow-up
Males Females Mean (SD) Right Left Bilateral No Yes Mean (SD)
Total N = 1511 (%)
P.F.C. Sigma PCL substitute N = 1161 (%)
Zimmer NexGen N = 350 (%)
617 (40.8%) 894 (59.2%) 68.6 (9.3 years) 787 (52.1%) 684 (45.3%) 40 (2.6%) 1476 (97.7%) 35 (2.3%) 106.3 (56.2 months)
460 (39.6%) 701 (60.4%) 68.7 (9.3 years) 611 (52.6%) 513 (44.2%) 37 (3.2%) 1152 (99.2%) 9 (0.8%) 126.8 (47.6 months)
157 (44.9%) 193 (55.1%) 68.2 (9.4 years) 176 (50.3%) 171 (48.9%) 3 (0.9%) 324 (92.6%) 26 (7.4%) 38.2 (9.7 months)
p-Value (effect size⁎) 0.08 (0.05) 0.36 (0.06) 0.03 (0.09) b0.001 (0.19) b0.001 (2.58)
⁎ Cramer's V effect size, except age and months where Cohen's D was used.
Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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Figure 1. Kaplan Meier estimate of survival.
however the medial distal femoral angle [MDFA] and medial proximal tibial angle [MPTA] were noted as being satisfactory with neutral alignment in the coronal plane). All of these patients were discharged from routine orthopedic care, and their early recovery was satisfactory. Patients typically started to experience symptoms of medial tibial pain with supra-patellar swelling from a combination of effusion and synovial thickening. Symptoms typically commenced at 12 to 24 months post-operatively. Inflammatory markers were normal in all cases, and no case required pre-operative aspiration. Radiographs of symptomatic knee replacements initially showed subtle bone loss on the medial tibia with a tilt of the tibial component always into a varus alignment. This tilt into varus became more obvious as time progressed. The cement mantle surrounding the stem of the tibial implant remained firmly bonded to bone in all cases. There were however small fractures in the cement on the medial side of the stem, which allowed it to tilt into varus. Figure 2 contains a set of four images for the same patient. The top row illustrates day-one post-operative anterioposterior and lateral images of a typical TKA who subsequently developed aseptic loosening of the tibial component. This radiograph demonstrates an intact cement mantle (both under the tibial component and around the keel), neutral coronal alignment, and no positioning issue with the prosthetics. The bottom row illustrates the same knee pre-revision. While no full-limb images were taken after the index surgery or prior to the revision surgery (which is a limitation of the study), an obvious varus deformity is demonstrated between the femoral and tibial components in the TKA. The tibial component has collapsed medially with lucency noted under the lateral aspect. These images were taken no more than six weeks before the revision procedure.
3.4. Intra-operative findings at the time of revision TKA In all cases, the tibial component was loose and could be removed without instrumentation. This is illustrated in Figure 3. The third image in Figure 3 illustrates an intact cement mantle after removal of the tibial component. In a subset of cases, a small volume of cement was still attached to some aspect of the undersurface of the tibial component. Intra-operative deep tissue biopsies and culture swabs were negative for any growth.
Table 5 Adjusted risk of revision for all patients (n = 1161).
Age – ≥65 years - b65 years Knee type – NexGen - P.F.C. sigma
Hazard ratio (95% CI)
p-Value
0.26 (0.13, 0.52) reference
b0.001
30.2 (10.3, 88.7) reference
b0.001
Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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Table 6 Breakdown of NexGen primary and revision cohort by gender, op. side and age.
Gender Operation Type
Male Female Left Right Bilateral
Mean age at operation (SD) Time from index surgery to revision in months (SD)
Total NexGen (n = 350)
Aseptic loosening revision group (n = 23)
157 (45%) 193 (55%) 170 (48%) 177 (51%) 3 (1%) 68.2 (9.4) N/A
9 (39%) 14 (61%) 16 (70%) 7 (30%) N/A 61.9 (7.8) 30.4 (9.7)⁎
⁎ Values for 22 revisions for aseptic loosening where revision date is known.
4. Discussion As per the UK NJR, infection/septic arthritis is the most common cause of revision in the first year following TKA with aseptic loosening being both the second most common cause in the first year and the leading overall cause for revision overall [1]. This is consistent with the findings of Schorer et al. and Sharkey et al. who also examined the etiology of revision TKAs, and confirmed that aseptic loosening is the most common cause overall [4] [5]. While our overall all-cause revision rate of 2.3% is in line with the UK revision rate of 2.4% [1] — our revisions are disproportionally skewed towards the smaller NexGen cohort of patients. We found that patients who are younger at the time of their index surgery are statistically more likely to require a revision than a patient who is older at the time of their index surgery. This finding is consistent with the UK NJR [1]. As per Table 4, there is a statistically significant difference in the number of all-cause revision operations between the two knee types (p b .001), with those given a NexGen knee more than nine times likely to require a revision for any cause (7.4% of NexGen TKAs required revision compared to 0.8% for P.F.C. TKAs). No differences in gender or age at operation were observed between the two knee types. There was aseptic loosening of the tibial component in 23 patients (6.6% of 350 NexGen TKAs) with an average revision time of 30.4 months. The femoral component had failed and required revision in one of these cases. This compares very unfavorably to all-cause revision figures of 0.44%, 1.61%, and 2.54% at years one, three, and five listed in the NJR for the NexGen Posterior Stabilized Fixed (cemented) knee [1]. Therefore, our NexGen cohort of 350 patients had an average failure rate of more than four times the expected rate at the three-year post-op point. While it would not be unexpected to see a small increase in the number of revisions required when a surgeons changes to a new implant with a new set of instruments due to the learning curve effect, we would not expect it to be this large. Also, we would expect to see the revisions front-loaded over the time period that the NexGen knee was used — which is not what we experienced. Out of our 23 patients who required a revision for aseptic loosening; six of them had their primary procedure in 2013, 10 of them in 2014, and seven of them in 2015. The lead author's role in every one of this study's TKAs ensured a consistent operative standard and the appropriate surgical approach. Between 2005 and 2017, the lead author performed a total of 103 TKA revisions — averaging eight per year. Out of these 103 procedures, the lead author performed the primary TKA in 52 of them. Out of this 52, nine were conversions of unicondylar knees to full TKA. Twenty-six of these procedures were on NexGen knees. Therefore, the lead author only performed 17 revision procedures on 14 non-NexGen knees (which includes the 10 revision procedures on nine P.F.C. knees in this paper) over a 13-year time period when he performed the primary TKA — giving a revision rate of less than two procedures per year. This includes revisions for traumatic peri-prosthetic fractures, two-stage revisions for septic arthritis, and other revision causes. The revision rate increased significantly once he started using the NexGen knee — 15 NexGen knees were revised in 2017 for aseptic loosening. This increase in revision rate has led the lead author to cease use of the NexGen knee. Orthopedics has changed in many ways from when the lead surgeon started using the P.F.C. prosthetic in 1999 to the present day. The changes in surgical technique over the years by the lead surgeon include a move from medial parapatellar to subvastus approach in 2010, the use of peri-articular local anesthetic for post-operative pain control since 2011 and the retention of the infrapatellar fat pad since 2015. None of these could be expected to contribute to pre-mature tibial component failure. No changes in typical patient profile were noted over the duration of the study. While there have been improvements to manufacturing techniques and materials used in orthopedics over the years covered by this study, such as the use of ceramic femoral components or different alloys like zirconium, we do not believe that this played a role in what we see in this study. Personal communications with NexGen have confirmed that manufacturing techniques such as machining from the raw material forging and applying the grit blast undersurface have remained the same over this time period. They also confirmed that there have been no changes to the specifications related to the blast surface on the underside of the tibial component. Personal communications with P.F.C. confirmed that they updated their manufacturing technique in 2005 to accommodate new cobalt chromium tibial trays and a new locking mechanism on the tibial tray for the polyethylene. There were no changes to the undersurface of the tibial component — including the stem, the keel or the finish [6]. Both of these companies introduced crosslinked polyethylene inserts in the mid-2000s which are now used as standard. We would not expect these to be contributing factors to aseptic loosening of the tibial components. Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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Figure 2. (Top Row) Day 1 Post-operative AP and lateral images of TKA; (Bottom Row) Pre-revision AP and lateral images of TKA.
Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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Figure 3. Intra-operative images of the removal of the tibial baseplate with an intact cement mantle remaining.
Other authors have identified increased rates of tibial loosening with the NexGen knee. Arsoy et al. reported aseptic loosening of the tibial component in 25 (1.9%) of their patients, with a median time to revision of 39 months [7]. In total, they implanted 1337 NexGen knees, using the three-degree-fluted (no PMMA pre-coat) tibial component [7] (launched in 2001). They reported five-year survivorship free of revision for any reason of 95.1%, and five-year survivorship free from tibial debonding of 97.8% [7]. Their five-year revision figure for aseptic debonding (2.2%) was in line with the all cause revision figure reported in the NJR (2.54%), and their all-cause revision figure at five years (4.9%) was nearly double the reported NJR figure (2.54%). Similarly, Foran et al. had a cohort of 529 TKAs using the NexGen knee, specifically the Minimally Invasive Surgery (MIS) tibial component with an undersurface pre-coat of PMMA [8]. They reported aseptic loosening in 1.5% of their cohort of patients with a median time to revision of 17 months [8]. They make no mention of overall revision rate for their cohort of patients. Both of these reports document a similar pattern of failure to what we experienced — clinically, nearly all patients had a combination of either knee pain exacerbated by weight bearing (following a pain-free post-operative period) and/or joint effusions [7,8]. Radiographic findings were satisfactory post-op, but lucencies were observed on follow-up radiographs between the tibial component and cement — most commonly in the medial and/or lateral tibial plateau, with subsidence of the tibial component into varus deformity [7,8]. Intra-operatively, the tibial component was loose and did not require instrumentation to be removed [7,8] — and in some cases the PMMA pre-coat on the MIS tibial component was absent completely [8]. Research published by Bonutti et al. report similar tibial debonding issues with the Attune knee [9]. Their search for aseptic failure of TKAs, particularly tibial component loosening at the cement interface, from three hospital databases yielded 13 patients (15 knees) with a mean age of 61 years [9]. All of these patients presented with similar clinical findings and subsequently had the same intraoperative findings as our cohort of revision patients [9]. Radiographically, only two of their 15 knees had evidence of radiolucency [9]. However, it should be noted that Bonutti failed to identify the total number of cases included in the overall cohort, which is a limitation of the study. According to Sharkey et al. “Loosening of the prosthesis is related to TKA component fixation methodology” [4]; however, there is no agreement in the literature as to whether cemented or uncemented is the best fixation method for function and survival [10]. A separate paper by Hazelwood et al. attributes early aseptic loosening in 11 (0.36%) patients, out of a cohort of 3048, to the use of ‘High Viscosity Cement’ (HVC) [11]. All nine patients surveyed (note: two patient declined survey involvement) had similar presentations to what we experienced — clinically, radiographically, and intra-operatively [11]. Two of these failures used the Palacos cement that was used in our patient cohort. The other seven used other types of cement. A recent article by Billi et al. looked at techniques for strengthening the tibial tray-cement bond using Palacos and Simplex cement. It compared multiple different variables, but overall it found that cement should be applied early, contamination of the surface should be avoided and both the keel and plateau should be cemented [12]. As can be seen by the x-rays in Figure 2, the keel was cemented in our NexGen TKAs. The timing of the cement was significant — early cementing (using Palacos) increased the mean strength by 72%, whereas late cementing decreased mean strength by 73% [12]. One interesting, and potentially relevant finding, is that bone marrow contamination of cement-tray interface reduced the mean strength of the interface by up to Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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94% with Palacos cement [12], and it is recommended that cement be added to the undersurface of the tibial tray and around the keel in order to mitigate this risk. It should be noted that this finding was not statistically significant and was a result of in vitro testing. It may be relevant to our study as adding cement to the undersurface of the tibial component is part of the manufacturer guidelines for cementing the NexGen tibial component, although it is not a recommendation for the P.F.C. tibial component. It should also be noted that cement can clearly be seen around the keel of the NexGen tibial component in Figure 2 above. Our study, along with Arsoy et al. use the NexGen LPS knee system with a non-coated tibial baseplate, whereas Foran et al. use a PMMA pre-coated baseplate. The same clinical, radiographical, and intra-operative findings were seen consistently in all three studies. Because of these findings, our concerns are focused on three areas: the tibial component itself, the cement (Palacos) used or the interaction at the tibial component-cement interface. From personal communication with a NexGen representative, we know that 81% of NexGen tibial components have a pre-coat with the remaining 19% not having a pre-coat. The registry data are not specific for pre-coated or non-pre-coated components. Our high revision rate of NexGen knees due to aseptic loosening only affects 19% of the overall NexGen volume meaning that the registry data may be somewhat misleading. As there are multiple published research articles dealing with tibial debonding and aseptic loosening across multiple NexGen tibial components, we can also hypothesize that there is an issue with the undersurface of the tibial tray and the cement mantle. At present, we are at a loss as to why we experienced these tibial issues. We followed the original cementing guidelines for the NexGen implant — although they were subsequently updated to include an extra cementing step. We believe that there are four subgroups that have not been analyzed on an individual basis: 1. Cement on bone only, no pre-coat on tibial component, 2. Cement on bone only, pre-coat on tibial component, 3. Cement on bone and the implant, no pre-coat on tibial component, and 4. Cement on bone and the implant, pre-coat on tibial component. This paper shows poor results for the first group with the NexGen knee. We believe that more research needs to be done on a detailed molecular level to assess this interaction between cement and component, particularly in relation to contamination with in vivo substances and the potential mitigation with adding of cement to the undersurface of the tibial component. We also believe more research needs to be done into micro-motion between the tibial tray and the cement mantle. The lead author was prompted to publish his results because of an unacceptably high rate of tibial component failures, which is at odds with much of the published data to date. 5. Strengths and limitations of this study Strengths of this research include that to the best of our knowledge, this is the first paper which compares two widely used prosthetic knee replacements where variables such as institution, surgeon, and surgical approach have been controlled as much as possible. There are several limitations to this study. Full-length limb x-rays were not done post-operatively after the primary procedure or pre-operatively before the revision. These would be necessary to confirm limb alignment and to categorically rule out any potential limb deformity. It should be noted that the femur was instrumented when the original femoral cuts were made — which would be difficult if a femoral deformity was present. An extra-medullary jig was used to align the tibial component to the ankle — again, making a tibial deformity unlikely. This paper was written retrospectively when the high rate of failure rate was noticed — therefore, it is limited by the imaging that already exists for the cohort of patients and the data that were captured about the procedure at the time of the procedure. The cohort of NexGen knees is smaller than the P.F.C. cohort — however, because of the high failure rate experienced, it was not prudent to continue using this prosthetic. As this paper was written retrospectively, there was no dedicated follow-up for individual patients; therefore, all individuals were assumed to be alive at the end of the study, and no account for deaths were made. Another limitation is that we are assuming that all of the patients in which the index procedure was done by the lead surgeon was referred back to the same lead surgeon when they experienced issues with their prosthetic — it is highly likely that there are patients that were referred to a different surgeon for which we have no visibility or knowledge. This means that we have potentially underestimated the number of knees affected both with the P.F.C. and the NexGen implants. We are also assuming that the index TKA database we are using is complete, and that the HIPE data extracted on TKA revisions are accurate. We acknowledge the fact that this is a widely used prosthetic that has been on the market for over 20 years with no similar excessively high failure rate in the published literature to date. We also acknowledge that the NexGen Option tibial baseplate has a positive Orthopedic Data Evaluation Panel (ODEP) rating [13]. We do, however, note that the registry data does not differentiate between pre-coated and non-pre-coated tibial components — which may potentially explain our results. 6. Conclusion In conclusion, we are left in a situation whereby an experienced arthroplasty surgeon had an unacceptably high rate of tibial component failure that was at variance with published results of this device. This failure rate resulted in use of the prosthetic being discontinued at our hospital. Surgical technique was as per manufacturer's recommendations with the exception that cement was only put on the bony surface and not on the implant. Perhaps this is a contributing factor. It also highlights the need for arthroplasty registries to separately analyze the results of pre-coated and non-pre-coated devices to see if this is a factor. Since returning to the P.F.C. prosthetic in 2016, the lead author has had no new instances of tibial failure with it. Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001
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Acknowledgments We would like to acknowledge the staff at University Hospital Limerick and Croom orthopedic hospital for their assistance in retrieving archived patient charts.
Funding source No funding was received for this work, and the authors have no financial interest in its publication.
References [1] Registry UNJ. NJR 14th annual report. http://www.njrreports.org.uk/Portals/0/PDFdownloads/NJR%2014th%20Annual%20Report%202017.pdf; 2017. [UK National Joint Registry; 2017]. [2] Executive HS. Knee replacement. http://www.hse.ie/eng/health/az/K/Knee-replacement/Recovering-from-a-knee-replacement.html; 2017. [3] Bini SA, Chen Y, Khatod M, Paxton EW. Does pre-coating total knee tibial implants affect the risk of aseptic revision? Bone Joint J 2013;95-B(3):367–70. [4] Sharkey PF, Lichstein PM, Shen C, Tokarski AT, Parvizi J. Why are total knee arthroplasties failing today–has anything changed after 10 years? J Arthroplasty 2014; 29(9):1774–8. [5] Schroer WC, Berend KR, Lombardi AV, Barnes CL, Bolognesi MP, Berend ME, et al. Why are total knees failing today? Etiology of total knee revision in 2010 and 2011. J Arthroplasty 2013;28(8 Suppl):116–9. [6] DePuy. DePuy sigma fixed bearing brochure. DePuy; 2010 Available from: http://synthes.vo.llnwd.net/o16/LLNWMB8/US Mobile/Synthes North America/Product Support Materials/Brochures/DPY_Sigma_Fixed_Bearing_Brochure_0612-65-508.pdf. [7] Arsoy D, Pagnano MW, Lewallen DG, Hanssen AD, Sierra RJ. Aseptic tibial debonding as a cause of early failure in a modern total knee arthroplasty design. Clin Orthop Relat Res 2013;471(1):94–101. [8] Foran JR, Whited BW, Sporer SM. Early aseptic loosening with a precoated low-profile tibial component: a case series. J Arthroplasty 2011;26(8):1445–50. [9] Bonutti PM, Khlopas A, Chughtai M, Cole C, Gwam CU, Harwin SF, et al. Unusually high rate of early failure of tibial component in ATTUNE total knee arthroplasty system at implant-cement interface. J Knee Surg 2017;30(5):435–9. [10] Gandhi R, Tsvetkov D, Davey JR, Mahomed NN. Survival and clinical function of cemented and uncemented prostheses in total knee replacement: a meta-analysis. J Bone Joint Surg Br 2009;91(7):889–95. [11] Hazelwood KJ, O'Rourke M, Stamos VP, McMillan RD, Beigler D, Robb WJ. Case series report: early cement-implant interface fixation failure in total knee replacement. Knee 2015;22(5):424–8. [12] Billi F, Kavanaugh A, Schmalzried H, Schmalzried TP. Techniques for improving the initial strength of the tibial tray-cement interface bond. Bone Joint J 2019;101B(1_Supple_A):53–8. [13] ODEP. Orthopaedic data evaluation panel. http://www.odep.org.uk/product.aspx?pid=43412019.
Please cite this article as: D. Keohane, F. Power, E. Cullen, et al., High rate of tibial debonding and failure in a popular knee replacement: A cause for concern, The Knee, https://doi.org/10.1016/j.knee.2019.10.001