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Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_9 | Pages 83 - 83
17 Apr 2023
Tawy G McNicholas M Biant L
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Total knee arthroplasty (TKA) aims to alleviate pain and restore joint biomechanics to an equivalent degree to age-matched peers. Zimmer Biomet's Nexgen TKA was the most common implant in the UK between 2003 and 2016. This study compared the biomechanical outcomes of the Nexgen implant against a cohort of healthy older adults to determine whether knee biomechanics is restored post-TKA. Patients with a primary Nexgen TKA and healthy adults >55 years old with no musculoskeletal deficits or diagnosis of arthritis were recruited locally. Eligible participants attended one research appointment. Bilateral knee range of motion (RoM) was assessed with a goniometer. A motorised arthrometer (GENOUROB) was then used to quantify the anterior-posterior laxity of each knee. Finally, gait patterns were analysed on a treadmill. An 8-camera Vicon motion capture system generated the biomechanical model. Preliminary statistical analyses were performed in SPSS (α = 0.05; required sample size for ongoing study: n=21 per group). The patient cohort (n=21) was older and had a greater BMI than the comparative group (n=13). Patients also had significantly poorer RoM than healthy older adults. However, there were no inter-group differences in knee laxity, walking speed or cadence. Gait kinematics were comparable in the sagittal plane during stance phase. Peak knee flexion during swing phase was lower in the patient group, however (49.0° vs 41.1°). Preliminary results suggest that knee laxity and some spatiotemporal and kinematic parameters of gait are restored in Nexgen TKA patients. While knee RoM remains significantly poorer in the patient cohort, an average RoM of >110° was achieved. This suggests the implant provides sufficient RoM for most activities of daily living. Further improvements to knee kinematics may necessitate additional rehabilitation. Future recruitment drives will concentrate on adults over the age of 70 for improved inter-group comparability


Bone & Joint Open
Vol. 3, Issue 6 | Pages 495 - 501
14 Jun 2022
Keohane D Sheridan GA Masterson E

Aims. Total knee arthroplasty (TKA) is a common and safe orthopaedic procedure. Zimmer Biomet's NexGen is the second most popular brand of implant used in the UK. The primary cause of revision after the first year is aseptic loosening. We present our experience of using this implant, with significant concerns around its performance with regards early aseptic loosening of the tibial component. Methods. A retrospective, single-surgeon review was carried out of all of the NexGen Legacy Posterior Stabilized (LPS) TKAs performed in this institute. The specific model used for the index procedures was the NexGen Complete Knee System (Legacy Knee-Posterior Stabilized LPS-Flex Articular Surface, LPS-Flex Femoral Component Option, and Stemmed Nonaugmentable Tibial Component Option). Results. Between 2013 and 2016, 352 NexGen TKAs were carried out on 331 patients. A total of 62 TKAs have been revised to date, giving an all-cause revision rate of 17.6% at a minimum of five years. Three of these revisions were due to infection. Overall, 59 of the revisions were performed for aseptic loosening (16.7%) of the tibial component. The tibial component was removed intraoperatively without instrumentation due to significant tibial debonding between the implant-cement interface. Conclusion. While overall, we believe that early aseptic loosening is multi-factorial in nature, the significantly high aseptic revision rate, as seen by an experienced fellowship-trained arthroplasty surgeon, has led us to believe that there is a fundamental issue with this NexGen implant design. Continued implant surveillance and rigorous review across all regions using this particular implant is warranted based on the concerning findings described here. Cite this article: Bone Jt Open 2022;3(6):495–501


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_13 | Pages 19 - 19
7 Aug 2023
Langton D Bhalekar R Wells S Nargol M Waller S Wildberg L Tilley S Nargol A
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Abstract. Introduction. At our national explant retrieval unit, we identified an unusual pattern of backside-deformation on polyethylene (PE) inserts of contemporary total-knee-replacements (TKRs). The PE backside's margins were inferiorly deformed in TKRs with central-locking trays. We reported that this backside-deformation appeared to be linked to tray debonding. Moreover, recent studies have shown high-rate of tray debonding in PS NexGen TKRs. Therefore, we hypothesised that backside deformation on PS inserts may be more than on CR inserts. Methodology. We used peer-reviewed techniques to analyse changes in the bearing (wear rate) and backside surfaces (deformation) of PE inserts using coordinate measuring machines [N=61 NexGen (CR-39 and PS-22) TKRs with non-augmented-trays]. Multiple regression was used to determine which variable had the greatest influence on backside-deformation. The amount of cement cover on trays was quantified as a %of the total surface using Image-J software. Results. There was no statistically significant difference (p=0.238) in median (IQR) wear rate of the CR PEs 18 (12–28) mm. 3. /year and PS PEs 14 (8–20) mm. 3. /year. The PE backside-deformation median (IQR) of PS [297(242–333) µm] was significantly higher (p=0.011), when compared with CR [241(161–259) µm]. Multiple regression modelling showed that duration in-vivo (p=0.037), central-clearance between insert and tray (p<0.001) and constraint (p=0.003) were significantly associated with PE backside-deformation. 27(69%) of CR and 20(91%) PS exhibited ≤10% of cement cover on tray. Conclusion. This explant study showed backside-deformation on PS inserts was more than on CR inserts. Therefore, indicating a high-rate of tibial tray debonding in PS compared to CR NexGen TKRs


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_3 | Pages 78 - 78
1 Jan 2016
Nakano N Matsumoto T Muratsu H Matsushita T Takayama K Kawakami Y Nagai K Kuroda R Kurosaka M
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Patients planning to undergo total knee arthroplasty (TKA), especially in Asian and Middle Eastern countries, usually expect to be able to perform activities requiring knee flexion such as sitting cross-legged or kneeling with ease after the surgery. Postoperative range of motion (ROM) can be affected by multiple factors such as the patient's gender, age, preoperative ROM, diagnosis, the surgeon's technique, the pre- and post-operative rehabilitation program, and the design of the prosthesis. Among these, the choice of the prosthesis depends on the surgeon's preference. As a result, several trials and studies have been conducted to improve postoperative ROM by modifying prosthesis design. The present study aimed to examine the results of TKA with the NexGen LPS-Flex system (Zimmer, Warsaw, Indiana), which is one of several high-flexion total knee prostheses that were designed to achieve a wide ROM for osteoarthritis in the valgus knee. A total of 27 primary TKAs in 26 osteoarthritis patients with valgus knee deformities (femorotibial angle (FTA) ≤ 170°) were performed using the NexGen LPS-Flex fixed prosthesis between July 2003 and December 2011. The patients included 2 men (7.7%, 2 knees) and 24 women (92.3%, 25 knees) with a mean age of 72.6 years (range, 59 to 83 years) at the time of the surgery. The mean duration of follow-up after surgery was 50.1 months (range, 24 to 126 months). Knee Society Knee Score (KSKS), Knee Society Function Score (KSFS), maximum flexion angle, maximum extension angle, and radiological femorotibial angle (FTA) were evaluated pre- and post-operatively. The mean preoperative KSKS and KSFS were 42.6 points (SD 7.5) and 41.1 points (SD 8.6), respectively, which improved after surgery to 82.2 points (SD 8.2) and 80.9 points (SD 7.6), respectively (P < 0.01). The maximum flexion angle improved from 109.1° (SD 23.1) to 117.3° (SD 12.4) postoperatively, but it did not reach statistical significance (P = 0.097). The preoperative maximum extension angle improved from −9.7° (SD 10.8) to −3.6° (SD 4.9) postoperatively (p < 0.05). The mean radiological FTA was 166.4° (SD 4.2; range: 155° − 170°) preoperatively and 172.4° (SD 2.7; range: 168° − 178°) at the final follow-up, and the difference was statistically significant (P < 0.01). None of the patients had undergone revision surgery by the final follow-up. As a conclusion, the results of the present study showed that the use of NexGen LPS-Flex implant in TKA for knee osteoarthritis with valgus deformity produced a satisfactory improvement in the clinical and radiological outcomes. Further studies on the outcomes of other prosthesis are needed to determine whether the NexGen LPS-Flex implant is advantageous for osteoarthritis patients with valgus knees who undergo TKA, and further large-scale studies with longer term follow-up are necessary to verify our results


Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_I | Pages 85 - 85
1 Mar 2006
Mai S Siebert W
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Introduction The NexGen-CR-Knee System ( Zimmer, Inc.) was developed for cruciate ligament retaining TKA, preserving as much of the function of the normal knee as possible. It was cleared by the FDA in 1995. Prerequisites are good bone quality and intact ligaments. It is part of a modular system for primary and some revision cases with a large selection of sizes, augmentation blocks and stem extensions. Material In the Orthopedic Center in Kassel about 1500 NexGen Cr devices were implanted and documented since October 1998. The 5-in-1 milling system was used and all components were cemented. Prospective evaluation pre-, intra- and postoperatively, at 1, 2 and 5 years was performed with a low drop out rate. 232 consecutive cases will have the 5 year data. The outcome will be presented, among others the Knee Society Score (function & knee), range of motion, complications and reasons for revisions. Comparison with the worldwide register of this implant is made. Conclusion The NexGen CR Knee Solution implants and the technique of implantation appear to be very successful in mid term results. It is a good basis for further developments such as highly crosslinked Polyethylene and the new CR Flex design


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_II | Pages 274 - 274
1 May 2009
Damilano M Fiammengo M Lancione V Caresio M Indemini E
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Aim of the study: The aim of our study is to provide a clinical and x-ray review of the Nexgen tantalum tibial plate prosthesis which have been implanted from 2004 to 2007 at our department, evaluating the short term osteointegration of the tantalum surface. Instruments and methods: 17 Nexgen PTG have been implanted without sacrifice of the posterior ligament with tantalum tibial plateau. The tibial component is constituted by a tantalum and polythene monoblock: it is implanted a press-fit through two pegs. The evaluation has been conducted with a minimum of 12 months follow-up. We considered a total of 13 prosthesis implanted in 12. The average patients age is 59.9 years (SD of 3.5 years) and within the range 52–67 years. 77% of the prosthesis (10 prosthesis) has been implanted in female patients. In 100% of situations, the pathology at the origin of the implementation was the primary gonar-thritis. For the clinic evaluation we used the HSS scheme; for the X-ray evaluation we used the “Knee Society TKA Roentgenographic evaluation and scoring system”. Results: clinical evaluation: the average HSS score we got at control (using the average score after 3months, 6months, 1 year and at present) is 91.7 (OS +/−7.6). The difference between the pre-surgery and at control score is about 27.6 scores. At check up every patient was free from pain with a complete operational recovery (11.19/12 scores). Nobody was using aids. The average pre-surgery articolarity was about 93 degrees, at check up we measured an average inflection extension of about 114.1 degrees. All the score differences between pre-surgery and post-surgery are statistically significant (P< =0.001). To conduct our study we used the statistical program SAS (v.8, Sas inc., North Carolina, USA). X-ray evaluation: we didn’t find any unstuck part, neither periprosthesis osteolysis nor prosthesis mobilisation. We didn’t find any periprosthesis radiolucency line bigger than 1mm and none of the previous ones had any complication at control. The absence of pain (subjective evaluation) and absence of radiolucency lines (an objective evaluation) represent two indirect parameters that we considered valid to evaluate the osteointegration of the implant. Discussion: The improvement of the surgical technique, either technical either instrumental, associated with a lower degree of pain, let us suggest that the prosthesis implantation is indicated also in young patients with high operational demands, who need a fast and complete operational recovery. For the same reason, it’s important to guarantee a good osteointegration and a long survival of the implant, with maximum care of bond tissue, forecasting a subsequent review surgery. The features of tantalum seem to respond pretty well at these requirements, being quite similar in terms of structural characteristics to the spongious bond. The reliability of the material is assured by its use in the prosthesis surgery since a couple of years ago. The design of the prosthesis is convenient in order to save at most the bond tissue. The high friction coefficient against the bone and the physical and mechanical features of the tantalum tibial plateau guarantee a fast osteointegration of the prosthesis. Although it’s proven that the implant survival with or without cost of the posterior ligament is the same, the prosthesis without cost of the posterior ligament has been chosen because the maintenance of the patient ligament offers an intrinsic knee stability. The optimal clinical and x-ray results, even if they are at short term, considered as indices of a good osteointe-gration, push us to believe that the use of the tantalum tibial plateau could be a good solution for any young patient with a gonarthrosis


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_4 | Pages 13 - 13
1 Jan 2016
Song IS Shin SY
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Purpose. The purpose of this study is toevaluate the clinical and radiologic results after high flexiontotal knee arthroplasty, Lospa. ®. (Corentec Inc.) with 10mm cutting of posterior femoral condyle and LPS-Flex. ®. (Zimmer Inc.) with 12.5mm cutting of posterior femoral condyle.(Fig. 1). Materials and Methods. We prospectively compared 205 knees in 128 patients who underwent arthroplasty usingLospa. ®. (groupA) and 63 knees in 48 patients who underwentarthroplasty using NexGen LPS-Flex. ®. (group B) from September 2010 to March 2012 at Department of Orthopaedic Surgery, Sun General Hospital (Daejeon, Korea). Mean follow-up period was 33 months(24–42) in group A and 33months(23–45) in group B, and mean age was 69.5 in group A, 70.4 in group B. The radiologic analysis included the change of mechanical axis deviation and femoro-tibial angle, implant position (α,β,γ,δ)(Fig 2). The clinical results were evaluated according to Hospital for special surgery (HSS), Knee society score (KSS), and range of motion. Results. Mechanicalaxis deviations were change in varusfrom 34.8 mm to 2.6 mm(P=0.02) in group A, and change in varusfrom 32.9mm to 3.1mm(P=0.03) in group B; no statistically significant difference was observed between them (P=0.12). Femoro-tibial angles were varus 4.3° to valgus 6.6°(P=0.02) in group A, and varus 3.9° to valgus 5.7°(P=0.03) in group B;no statistically significant difference was observed between them(P=0.27). Implant positions were α=96.3°, β=90.7°, γ=1.0°, δ=88.2° in group A, and α=97.1°, β=90.3°, γ=1.5°, δ=88.9° in group B; no statistical significance in implant position was observed between the two groups (P=0.23 in α, P=0.19 in β, P=0.14 in γ, P=0.15 in δ). Mean HSS improved from 48.5 to 93.6 (P=0.02) in group A, and from 51.5 to 89.7(P=0.03) in group B; no statistical significal difference was observed between the two groups(P=0.12). Mean KSS improved from 55.1 to 93.4(P=0.03) in group A, and from 48.2 to 92.2(P=0.02) in group B; no statistical significal difference was observed between the two groups(P=0.12). Range of motion improved from 106.4°to 123.2°(P=0.01) in group A, and from 105.0° to 125.0° (P=0.03) in group B; no statistical significal difference was observed between the two groups(P=0.16). Conclusions. Lospa. ®. total knee arthroplasty showed excellent earlyradiologic, clinical results and no statistically significant difference in the results was observed between Lospa. ®. and LPS-Flex. ®.


Orthopaedic Proceedings
Vol. 102-B, Issue SUPP_2 | Pages 33 - 33
1 Feb 2020
Knowlton C Wimmer M
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INTRODUCTION. The specific factors affecting wear of the ultrahigh molecular weight polyethylene (UHMWPE) tibial component of total knee replacements (TKR) are poorly understood. One recent study demonstrated that lower conforming inserts produced less wear in knee simulators. The purpose of this study is to investigate the effect of insert conformity and design on articular surface wear of postmortem retrieved UHMWPE tibial inserts. METHODS. Nineteen NexGen cruciate-retaining (NexGen CR) and twenty-five NexGen posterior-stabilized (NexGen PS) (Zimmer) UHWMPE tibial inserts were retrieved at postmortem from fifteen and eighteen patients respectively. Articular surfaces were scanned at 100×100μm using a coordinate measuring machine (SmartScope, OGP Inc.). Autonomous mathematical reconstruction of the original surface was used to calculate volume loss and linear penetration maps of the medial and lateral plateaus. Wear rates for the medial, lateral and total articular surface were calculated as the slope of the linear regression line of volume loss against implantation time. Volume loss due to creep was estimated as the regression intercept. Student t-tests were used to check for significant. RESULTS. The NexGen CR and NexGen PS patient groups were approximately the same age at time of implantation (mean±SD: 72.1±9.9 and 68.7±8.8 years respectively, p=0.260) and implantation times were not significantly different (8.7±3.1 and 9.1±3.7 years, p=0.670). Both groups showed high variability in wear scars. No significant difference in wear rates on the total surface (mean±SE: 11.89±5.01 mm. 3. /year vs. 11.09±4.18 mm. 3. /year, p=0.905). However, NexGen CR components showed significantly higher volume loss due to creep than NexGen PS components (70.22±47.07 mm. 3. vs. 31.30±41.15 mm. 3. , p=0.007). These results were reflected on the medial and lateral sides, with no significant differences in wear rates on the medial side (p=0.856) or lateral side (p=0.633) and higher volume losses due to creep associated with the NexGen CR components. While NexGen CR and NexGen PS showed a near equal mean percentage of volume loss on the medial side (CR: 52.4±11.7%, PS: 52.5±11.6%), a paired t-test showed that NexGen PS components showed a higher volume loss on the medial side (p=0.056), NexGen CR components did not (p=0.404). DISCUSSION. The combination of higher conformity and more kinematic constraint in NexGen CR components may create larger contact areas with higher stresses, leading to higher volume loss due to creep observed in this study. However, these factors did not produce increased wear rates in the population. Constrained components may maintain more loading on medial side and limit sliding distance on lateral side, causing more wear medially. Total wear rates were very similar and resembled the previously reported rate of 12.9 ± 5.97 mm. 3. /year for retrieved Miller-Galante II (Zimmer) components, which features a near flat articulating surface. These findings indicate that materials factors may be most important in producing wear and that higher conformity alone does not decrease wear. For any figures or tables, please contact authors directly


Bone & Joint Open
Vol. 5, Issue 4 | Pages 277 - 285
8 Apr 2024
Khetan V Baxter I Hampton M Spencer A Anderson A

Aims. The mean age of patients undergoing total knee arthroplasty (TKA) has reduced with time. Younger patients have increased expectations following TKA. Aseptic loosening of the tibial component is the most common cause of failure of TKA in the UK. Interest in cementless TKA has re-emerged due to its encouraging results in the younger patient population. We review a large series of tantalum trabecular metal cementless implants in patients who are at the highest risk of revision surgery. Methods. A total of 454 consecutive patients who underwent cementless TKA between August 2004 and December 2021 were reviewed. The mean follow-up was ten years. Plain radiographs were analyzed for radiolucent lines. Patients who underwent revision TKA were recorded, and the cause for revision was determined. Data from the National Joint Registry for England, Wales, Northern Island, the Isle of Man and the States of Guernsey (NJR) were compared with our series. Results. No patients in our series had evidence of radiolucent lines on their latest radiological assessment. Only eight patients out of 454 required revision arthroplasty, and none of these revisions were indicated for aseptic loosening of the tibial baseplate. When compared to data from the NJR annual report, Kaplan-Meier estimates from our series (2.94 (95% confidence interval (CI) 1.24 to 5.87)) show a significant reduction in cumulative estimates of revision compared to all cemented (4.82 (95% CI 4.69 to 4.96)) or cementless TKA (5.65 (95% CI 5.23 to 6.10)). Our data (2.94 (95% CI 1.24 to 5.87)) also show lower cumulative revision rates compared to the most popular implant (PFC Sigma Cemented Knee implant fixation, 4.03 (95% CI 3.75 to 4.33)). The prosthesis time revision rate (PTIR) estimates for our series (2.07 (95% CI 0.95 to 3.83)) were lower than those of cemented cases (4.53 (95% CI 4.49 to 4.57)) from NJR. Conclusion. The NexGen trabecular (tantalum) cementless implant has lower revision rates in our series compared to all cemented implants and other types of cementless implants, and its use in younger patients should be encouraged. Cite this article: Bone Jt Open 2024;5(4):277–285


Orthopaedic Proceedings
Vol. 92-B, Issue SUPP_I | Pages 172 - 172
1 Mar 2010
Kim Y
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The high-flex total knee arthroplasty system was introduced to enhance knee flexion and to facilitate tibiofemoral articulation at high-flexion by the design modification of an increased thickness of the posterior wall of the femoral component by 2 mm compared with the standard total knee prosthesis. However, several clinical studies on the effectiveness of designs intended to provided high flexion following total knee arthroplasty have produced conflicting results. We performed a prospective, randomized study to compare the ranges of motion of the high-flex and standard total knee replacements in patients who were managed with simultaneous bilateral total knee arthroplasty. This study comprised of three independent groups of patients. The first group: Fifty patients (mean age, 68 years old) received a standard NexGen LPS prosthesis in one knee and a NexGen LPS-Flex prosthesis in the contralateral knee. Two patients were men, and 48 were women. At a mean of 2.1 years postoperatively, the patients were assessed clinically and radiographically with use of the knee-rating systems of the KS and HSS. The second group: Fifty-four patients (mean age 69.7 years) received a NexGen CR prosthesis in one knee and a NexGen CR-Flex prosthesis in the contralateral knee. Five patients were men, and 49 were women. The minimum follow-up was 3 years (mean, 3.1 years). At each follow-up, the WOMAC score and range of knee motion were evaluated and patients were assessed clinically and radiographically with use of the knee-rating systems of the KS and HSS. The third group: Two hundred and fifty patients (mean age, 71.6 years) received a NexGen CR-Flex knee prosthesis in one knee and a NexGen LPS-Flex knee prosthesis in the contrallateral knee. Ten patients were men and 240 were women. At each follow-up (mean follow-up, 2.3 years) the patients were assessed clinically and radiographically with use of the knee-rating systems of the KS and HSS. The first group: The mean postoperative HSS knee score was 90 points for the knees treated with the NexGen LPS prosthesis and 89.4 points for those treated with the NexGen LPS-Flex prosthesis. At the time of the final follow-up, the knees with the NexGen LPS prosthesis had a mean range of motion of 135.8° (range, 105° to 150°) and those with a NexGen LPS-Flex prosthesis had a mean range of motion of 138.6° (range, 105° to 150°). No knee had aseptic loosening, revision, or osteolysis. The second group: The mean postoperative KS and HSS knee scores were 93.7 and 89 points, respectively in the knees with a NexGen CR prosthesis and those were 93.9 and 90 points, respectively in the knees with a NexGen CR-Flex prosthesis. The mean postoperative WOMAC score was 22 points. Postoperatively, the mean non-weight and weight bearing ranges of motion were 131° (range, 90° to 150°) and 115° (range, 75° to 145°), respectively in the knee with a NexGen CR prosthesis and those were 133° (range, 90° to 150°) and 118 (range, 75° to 145°), in the knees with a NexGen CR-Flex prosthesis. Patients satisfaction and radiographic results were similar in both groups. No knee had aseptic loosening, revision, or osteolysis. The third group: The mean postoperative KS and HSS knee scores were 95 and 90 points, respectively in the knees with a NexGen CR-Flex prosthesis and those were 95 and 91 points, respectively in the knees with a NexGen LPS-Flex prosthesis. Postoperatively, the mean non-weight and weight bearing ranges of motion were 133° (range, 90° to 145°) and 118° (range, 75° to 135°), respectively in the knees with a NexGen CR-Flex prosthesis and those were 135° (range, 85° to 140°) and 122° (range, 70° to 135°), respectively in the knees with a NexGen LPS-Flex prosthesis. No knee had aseptic loosening, revision, or osteolysis. After a minimum follow-up of two years, we found no significant differences among the first, second and the third groups with regard to range of knee motion, or clinical and radiographic results


Orthopaedic Proceedings
Vol. 102-B, Issue SUPP_1 | Pages 91 - 91
1 Feb 2020
Baral E Purcel R Wright T Westrich G
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Introduction. Long term data on the survivorship of cemented total knee arthroplasty (TKA) has demonstrated excellent outcomes; however, with younger, more active patients, surgeons have a renewed interest in improved biologic fixation obtained from highly porous, cementless implants. Early designs of cementless total knees systems were fraught with high rates of failure for aseptic loosening, particularly on the tibial component. Prior studies have assessed the bone ingrowth extent for tibial tray designs reporting near 30% extent of bone ingrowth . (1,2). While these analyses were performed on implants that demonstrated unacceptably high rates of clinical failure, a paucity of data exists on the extent on bone ingrowth in contemporary implant designs with newer methods for manufacturing the porous surfaces. We sought to evaluate the extent of attached bone on retrieved cementless tibial trays to determine if patient demographics, device factors, or radiographic results correlate to the extent of bone ingrowth in these contemporary designs. Methods. Using our IRB approved retrieval database, 17 porous tibial trays were identified and separated into groups based on manufacturer: Zimmer Natural Knee (1), Zimmer NexGen (10), Stryker Triathlon (4) and Biomet Vanguard Regenerex (2). Differences in manufacturing methods for porous material designs were recorded. Patient demographics and reason for revision are described in Table 1. Radiographs were used to measure tibiofemoral alignment and the tibial mechanical axis alignment. Components were assessed using visual light microscopy and Photoshop to map bone ingrowth extent across the porous surface. ImageJ was used to threshold and calculate values for bone, scratched metal, and available surface for bone ingrowth (Fig. 1). Percent extent was determined as the bone ingrowth compared to the surface area excluding any scratched regions from explantation. Statistics were performed among tray designs as well as between the lateral and medial pegs, if designs had pegs available for bony ingrowth. Results. Mean bone ingrowth extent was 51.4% for the tibial tray for the entire cohort. Bone ingrowth extent was statistically greater in the Zimmer NexGen design (63.8%; p=.027) compared to the other three designs (Table 2). Four sets of pegs were excluded from analysis due to lack of porous coatings or pegs having been removed at revision surgery. Across all designs, the medial peg had 45.2% ingrowth and the lateral peg had 66.1% ingrowth. The medial peg for the NexGen design had significantly less bone ingrowth compared to the lateral peg (58.7% vs. 75.4%; p=0.044). No significant differences were found in tibiofemoral alignment or tibial mechanical axis alignment between the implant groups. No significant differences were found among implants revised for aseptic loosening versus any other reason for revision (54% vs 30%; p=.18). Discussion. Our results demonstrate high rates of bone ingrowth extent in contemporary designs, further supporting porous design rationales and a role for additive manufacturing to form enhanced porosity. We plan on exploring staining techniques to confirm our visual inspection. Contemporary designs have shown successful rates for improved longevity for cementless total knee systems. For any figures or tables, please contact the authors directly


Orthopaedic Proceedings
Vol. 102-B, Issue SUPP_1 | Pages 113 - 113
1 Feb 2020
Wimmer M Ngai V Kunze J Cip J Laurent M Jacobs J
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Introduction. Ideally, standardized wear testing protocols replicate the in vivo motions and forces of TKR patients. In a previous study with 30 TKR patients, two distinct in vivo gait patterns emerged, one characterized as having low anteroposterior (AP-L) motion and the other high anteroposterior (AP-H) motion. The aim of this study was to determine the effect of the two in vivo-determined gait patterns on total and backside insert wear in comparison with the ISO standard 14243-3. In order to differentiate and accurately quantify topside and backside wear, a novel technique was employed where different lanthanide tracers are incorporated into the polyethylene during manufacture. Materials and Methods. Components from the Zimmer NexGen CR Knee Replacement System were used. Europium (Eu) and Gadolinium (Gd)-stearates were mechanically mixed with GUR1050 UHMWPE resin to obtain two tracer-UHMWPE resins containing 49.1±1.5 ppm Eu and 68.8±1.6 ppm Gd, respectively. 12 grams of the Eu-doped resin was placed on the bottom, 10 grams of virgin GUR1050 resin was placed in the middle, and 10 grams of Gd-doped resin was placed on the top to mold NexGen CR tibial inserts. The backside was then machined to interlock with the tibial baseplate. The minimum insert thickness was 10 mm. All inserts were packaged in nitrogen and gamma sterilized. The wear test was conducted on a 4-station knee simulator in displacement-control mode. Simulator input was obtained from ISO 14243-3 and from gait of 30 NexGen TKR subjects, previously categorized into low (AP-L) and high (AP-H) anteroposterior motion groups. Per station, each insert was sequentially subjected to ISO, AP-L, AP-H motion for 2 Mc at 1 Hz. Subsequently, the ISO profile was repeated. Tibial inserts were weighed and lubricant samples were taken after every 0.5 Mc interval. Knowing the Eu and Gd concentrations from ICP-MS analysis, and normalizing those to the concentrations in the polyethylene inserts, the localized (Eu – backside; Gd – topside) wear was calculated. Wear particle analysis was conducted following established protocols. Results. For all tested liners (n=4 + soak) during the three tested motion profiles, the chemically calculated wear correlated closely with the gravimetrically determined wear (R. 2. »0.8), with slopes not different from 1. Both in vivo motion groups displayed higher wear rates than the ISO group following the order of the AP motion amplitudes (Figure). Backside wear for ISO constituted 2.76% ± 0.90% (mean ± SE) of the total wear, increasing significantly to 15.8 ± 3.2% for AP-L and further increasing to 19.3 ± 0.95% for AP-H (p<.001). The mean wear particle sizes were under 200 nm for all three motion patterns, being largest for the AP-H gait protocol (Table). Discussion. Both in vivo motion groups displayed higher wear rates than the group tested per ISO standard 14243-3. Interestingly backside wear was affected the most and increased 4.5 to 6-fold over ISO. Testing for the proportion of backside wear across various activities of daily living may therefore be an important consideration in evaluating knee prostheses wear and could be facilitated by this new tracer technology. For any figures or tables, please contact the authors directly


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXVII | Pages 525 - 525
1 Sep 2012
Kumar V Garg B Malhotra R
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Introduction. We compared standard NexGen Cruciate substituting-flex prosthesis with gender-specific NexGen Cruciate substituting flex prosthesis in patients undergoing bilateral total knee arthroplasty with regard to Coverage of the bone by femoral component, Clinical outcome, Radiographic outcome, Survival and complication rates, with special emphasis on patellofemoral complications. Material & Methods. 30 female patients with osteo-arthritis of the knees with similar deformity and preoperative range of motion were randomized to have one knee replaced with a gender non-specific Nexgen Cruciate substituting (Zimmer) prosthesis and the other with Gender Cruciate substituting (Zimmer) prosthesis. Follow-up clinical evaluation was done at 6, and 12 months postoperatively and then at yearly interval using “Knee Society” Recommendations. Clinical assessment of the patellofemoral joint of the replaced knees was done with the help of “Hospital for Special Surgery” patellar scoring system. The overall patient satisfaction after surgery was evaluated with use of the British Orthopaedic Association patient satisfaction score. Results. The mean age was 63.8 years (range 49–76 years). 14 patients had standard NexGen Cruciate substituting-flex gender knee prosthesis on right side and 16 patients had on left side. On the other sides, standard NexGen Cruciate substituting-flex prosthesis implant was used. Preop Clinical findings were similar in both groups. The average Preop range of motion was identical in both the groups. The average follow up was 2.5 years (2–3.8 years). The mean post-operative Knee Society knee scores were 88,90,94, (70 to 100) and 87,92, 93 (70 to 100) points and the function scores were 83,85,88 (60 to 100) and 84.86.88 (60 to 100) points for the standard implants and the gender-specific designs, respectively at 6 months, 1 year and 2 year follow up. Mean improvement in patella score was 65, 71.1 and 73.3 points in Gender group at the end of 6 month, 1 yr and 2 yr respectively as compared to 65.6, 71.1 and 72.2 in Nexgen group. No patient had malpositioning of components or radiolucencies at the end of 2 year follow up. Mean improvement in BOA functional score was 20.6, 22.6 and 24.1 points in Gender group at the end of 6 months, 1 year and 2 year respectively as compared to 20.7, 21.8 and 23.2 in Nexgen group. In those with a standard prosthesis, the femoral component was closely matched in 30 knees, overhung in 17 and undercovered the bone in 13. In those with a gender-specific prosthesis, it was closely matched in 45 knees and undercovered the bone in 15. Conclusion. Although gender specific knee matched the femoral anatomy of Indian female knees better than the standard nexgen Knee, we found no significant differences between the two groups with regard to the clinical and radiological results, patient satisfaction or complication rate


Bone & Joint Research
Vol. 11, Issue 5 | Pages 252 - 259
1 May 2022
Cho BW Kang K Kwon HM Lee W Yang IH Nam JH Koh Y Park KK

Aims. This study aimed to identify the effect of anatomical tibial component (ATC) design on load distribution in the periprosthetic tibial bone of Koreans using finite element analysis (FEA). Methods. 3D finite element models of 30 tibiae in Korean women were created. A symmetric tibial component (STC, NexGen LPS-Flex) and an ATC (Persona) were used in surgical simulation. We compared the FEA measurements (von Mises stress and principal strains) around the stem tip and in the medial half of the proximal tibial bone, as well as the distance from the distal stem tip to the shortest anteromedial cortical bone. Correlations between this distance and FEA measurements were then analyzed. Results. The distance from the distal stem tip to the shortest cortical bone showed no statistically significant difference between implants. However, the peak von Mises stress around the distal stem tip was higher with STC than with ATC. In the medial half of the proximal tibial bone: 1) the mean von Mises stress, maximum principal strain, and minimum principal strain were higher with ATC; 2) ATC showed a positive correlation between the distance and mean von Mises stress; 3) ATC showed a negative correlation between the distance and mean minimum principal strain; and 4) STC showed no correlation between the distance and mean measurements. Conclusion. Implant design affects the load distribution on the periprosthetic tibial bone, and ATC can be more advantageous in preventing stress-shielding than STC. However, under certain circumstances with short distances, the advantage of ATC may be offset. Cite this article: Bone Joint Res 2022;11(5):252–259


Orthopaedic Proceedings
Vol. 102-B, Issue SUPP_1 | Pages 4 - 4
1 Feb 2020
Oni J Yi P Wei J Kim T Sair H Fritz J Hager G
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Introduction. Automated identification of arthroplasty implants could aid in pre-operative planning and is a task which could be facilitated through artificial intelligence (AI) and deep learning. The purpose of this study was to develop and test the performance of a deep learning system (DLS) for automated identification and classification of knee arthroplasty (KA) on radiographs. Methods. We collected 237 AP knee radiographs with equal proportions of native knees, total KA (TKA), and unicompartmental KA (UKA), as well as 274 radiographs with equal proportions of Smith & Nephew Journey and Zimmer NexGen TKAs. Data augmentation was used to increase the number of images available for DLS development. These images were used to train, validate, and test deep convolutional neural networks (DCNN) to 1) detect the presence of TKA; 2) differentiate between TKA and UKA; and 3) differentiate between the 2 TKA models. Receiver operating characteristic (ROC) curves were generated with area under the curve (AUC) calculated to assess test performance. Results. The DCNNs trained to detect KA and to distinguish between TKA and UKA both achieved AUC of 1. In both cases, heatmap analysis demonstrated appropriate emphasis of the KA components in decision-making. The DCNN trained to distinguish between the 2 TKA models also achieved AUC of 1. Heatmap analysis of this DCNN showed emphasis of specific unique features of the TKA model designs for decision making, such as the anterior flange shape of the Zimmer NexGen TKA (Figure 1) and the tibial baseplate/stem shape of the Smith & Nephew Journey TKA (Figure 2). Conclusion. DCNNs can accurately identify presence of TKA and distinguish between specific designs. The proof-of-concept of these DCNNs may set the foundation for DCNNs to identify other prosthesis models and prosthesis-related complications. For any figures or tables, please contact the authors directly


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_16 | Pages 47 - 47
1 Nov 2018
Keohane D Power F Cullen E O'Neill A Masterson E
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Total knee arthroplasty (TKA) is a common orthopaedic procedure with over 1,500 done in 2016 in Ireland alone. 96% of all TKAs are due to pain in the knee associated with osteoarthritis. According to the UK National Joint Registry (NJR), there is a 0.47%, 1.81%, 2.63% and 4.34% probability risk of undergoing a revision TKA within one, three, five and ten years respectively post-index surgery. 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. The NexGen Posterior Stabilised Fixed has NJR revision rates of 0.44%, 1.61% and 2.54% at years one, three and five respectively. A retrospective review was carried out of 350 NexGen TKAs that were performed directly by, or under the supervision of, a fellowship trained arthroplasty surgeon in a dedicated orthopaedic hospital between April 2013 and December 2015. 26 (7.4%) of these were revised as of 31 December 2017. Three were for septic arthritis with the remaining 23 (6.6%) for aseptic loosening. Patients typically started to experience symptoms of medial tibial pain with supra-patellar swelling from a combination of effusion and synovial thickening at 12–24 months. Inflammatory markers were normal in all cases. Radiographs of symptomatic knee replacements showed bone loss on the medial tibia with a tilt of the tibial component into a varus alignment. The high number of revisions of this particular prosthetic has led to its use being discontinued at this centre


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_34 | Pages 99 - 99
1 Dec 2013
Kawano T Ihara H Tsurusaki S
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[Introduction]. One of the modern design total knee arthroplasty (TKA) system, the NexGen Legacy posterior-stabilized (LPS) Flex prosthesis, has been in use at our hospital since 2001. Between 2006 and 2011, NexGen LPS-Flex primary TKA were mainly performed in combination with a cemented short-keeled minimally invasive version tibial tray (MIS tibial component) instead of the traditional NexGen stemmed tibial tray. We observed some cases required early revision of isolated tibial component in primary TKA performed in this period. Therefore, our objectives were to report the series of this revision cases and to consider this failure mechanism. [Patients & Methods]. A total of 526 primary TKAs were performed using a NexGen LPS-Flex prosthesis and MIS tibial component during five-year period at our hospital. The mean age was 74 years at the time of the index procedure. We assessed revision rate of this tibial tray in this study and described clinical course of the revision cases. We also examined the clinical and radiographic features which could be associated with the failure. [Results]. The mean duration of follow-up was 2.5 years and there were 13 knees received tibial component revision during this period. Twelve knees were diagnosed with osteoarthritis and one knee with rheumatoid arthritis. The duration between primary TKA and revision averaged at 3.3 years, and the mean age at the second procedure was 67 years. TKAs were performed without applying the tibial central extension stem in all 13 knees, and thick polyethylene insert like 17 or 20 mm were selected for seven and 14 mm for five of 13 knees, that were the typical features on the primary TKA. Postoperative course of all 13 cases was uneventful and 10 of 13 knees achieved deep knee flexion over at 125 degrees. Prerevision radiographs showed characteristic pattern with tibial tray debonding at the cement-implant interface and subsidence into varus and flexion in all 13 knees. In all cases, intraoperative findings revealed a grossly loose tibial component with most of the cement mantle still attached to the bone. No case exhibited signs of macroscopic polyethylene wear and femoral component loosening. [Discussion]. The most common reason for failure of TKA is infection followed by implant loosening, polyethylene wear, and instability. Several studies document survival rates of over 90% up to 20 years with modern TKA designs using a cemented stemmed tibial component. Although failure of the tibial component was more prevalent in some early TKA designs, in recent years, failure of tibial fixation has been a rare cause of revision. Our experience with early aseptic loosening of this tibial component has suggested the low-profile design with no central stem as a cause for accelerated failure. Furthermore, other factors associated with increased this failure could include a thicker insert and postoperative achievement of high flexion


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_12 | Pages 34 - 34
1 Oct 2018
Padgett DE Kahlenberg CA Joseph AD
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Introduction. Hip and knee replacements are being performed at increasing rates and currently account for one of the largest procedure expenditures in the Medicare budget. Outcomes of total knee replacement (TKR) depend on surgeon, patient and implant factors. The impact that the specific implants might have on patient-reported outcomes is unknown. The primary purpose of this study was to evaluate the patient-reported functional outcomes and satisfaction after primary total knee arthroplasty in patients with osteoarthritis who underwent TKR using five different brands of posterior-stabilized implants. Specifically, the aim was to evaluate for any difference in patient-reported outcomes based on implant brand used. The hypothesis was that there would be no difference in functional outcome that could be attributed to the implant used in primary TKR. Methods. Using our institution's total joint arthroplasty registry, we identified 4,135 patients who underwent total knee replacement (TKR) using one of the five most common implant brands used at our institution. These included Biomet Vanguard (N=211 patients), Depuy/Johnson&Johnson Sigma (N=221), Exactech OptetrakLogic (N=1,507), Smith & Nephew Genesis II (N=1,414), and Zimmer NexGen (N=779). Only posterior-stabilized primary TKRs in patients with osteoarthritis were included. Patients were evaluated preoperatively using the Knee Osteoarthritis Outcomes Score (KOOS), Lower Extremity Activity Scale (LEAS), and Short Form-12 (SF-12). Demographics including age, body mass index (BMI), Charleston Comorbidity Index (CCI), ASA physical status classification, sex, and smoking status were collected. Postoperatively, 2-year KOOS, LEAS, SF-12, and satisfaction scores were compared between implant groups. Results. At 2-year follow-up, patient-reported outcome scores were available for a total of 4,069 patients. In multiple regression analysis which separately compared each implant group to the aggregate of all others, after accounting for age, BMI, CCI, ASA status, and sex, there were no clinically significant differences in KOOS score changes from baseline to 2-year follow-up between any of the implants. In 2-year satisfaction, >80% of patients in each implant group were satisfied in all domains measured. In the multivariate regression model, patients in the NexGen group had the highest likelihood of being satisfied (OR 1.63, p=0.006) and OptetrakLogic patients had the lowest likelihood of being satisfied (OR 0.60, P<0.001) although these differences were below the minimal clinically important thresholds. Conclusion. TKR provides patient satisfaction and improvement in function regardless of implant type. While some implant systems had higher outcome scores than others, these differences were all below clinically significant thresholds. Whether these differences are a function of surgeon expertise or implant design is unknown. Future research should focus on identifying specific design elements that contribute to improved patient outcomes. Healthcare administrators may find the similarities in clinical outcomes to be a useful consideration when negotiating implant purchasing contracts


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_I | Pages 148 - 148
1 Mar 2008
Dunbar M Wilson D Hennigar A Amirault D Reardon G Gross M
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Purpose: To investigate the stability of an uncemented Trabecular Metal (TM) tibial component we used maximum total point motion (MTPM) as determined with RSA to compare micromotion at the tibial component/bone interface between the uncemented Nexgen TM monoblock and cemented Nexgen cobalt chrome modular knee prostheses. Methods: A power calculation determined that a minimum sample size of 40 (20/group) was required. Sixty-seven patients with primary osteoarthritis of the knee were randomized to receive the Nexgen TM monoblock (n=34; 20 female; mean age=66 years; mean BMI=32) or cobalt chrome modular (n=33; 19 female; mean age=65 years; mean BMI=33) posterior stabilized knees. Four experienced knee surgeons followed a standardized surgical technique (PCL resection, patella resurfacing, RSA bead placement in polyethylene and tibia) and post-operative protocol (CPM as tolerated, no drains, WBAT). SF-36, WOMAC, PCS, KSCRS were administered to all patients pre-operatively and at 6, 12 and 24 months post-operatively and BMI was recorded. Within 4 days of surgery and at 6, 12 and 24 months post-operatively patients underwent bi-planar x-rays. Results: The TM group had greater initial migration but appeared stabilized at 1 year. There were 2 significant subgroups in the TM group based on migration at 6 months: one group had mean values of 2.1 mm while the other had mean values of 0.4 mm which was comparable to the modular group (0.6 mm). There was no significant migration between 6 and 12 months for both implants indicating good fixation to the proximal tibia. There were no differences between groups in the outcome measures, age and BMI. Conclusions: There was no difference in MTPM between groups at 1 year post-op and all knees appeared well fixed to the proximal tibia by 6 months postop. The Nexgen TM monoblock tibial component seemed to be prone to greater initial migration but it does not appear to compromise long-term bony in-growth and fixation. Long-term survivorship of the TM tibial component should be the same or better than a cemented cobalt chrome tray. Funding: Other Education Grant. Funding Parties: Unrestricted grant from Zimmer Inc


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_IV | Pages 435 - 436
1 Nov 2011
Cho S Youm Y Jung C Park K
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The purpose of this prospective study was to investigate the necessity of gender-specific design in total knee arthroplasty (TKA) for Korean women. One hundred and seventeen women (151 knees) who underwent primary TKA by one surgeon with Nexgen. ®. LPS (Zimmer, Warsaw, IN) were evaluated. The mean age was 70 (range 52–80) years. The size of the implant was determined by considering anteroposterior (AP) dimension and the amount of posterior condylar resection. Size C was used in 72 knees, size D in 57 and size E in 22. We measured the mediolateral (ML) widths of distal femur at four points (anterior, distal anterior, distal posterior, posterior) intraoperatively after bone cutting, and compared them with the ML widths of the corresponding femoral implants. The ML/AP ratio was calculated in each size group. The mean ML widths of the distal femur checked at all four points were larger than those of the implants. The ML/AP ratio of the distal femur decreased as the size increased from C to E, especially that of the anterior point. Overhanging occurred in 7 cases (4.6%, size C -2 cases, size D -2 cases, E -3 cases) : Nexgen. ®. LPS implant was used in 5 cases because there was only minimal antero-lateral overhanging, resulting in no postoperative problem such as pain or limited motion. Gender-specific design was used in only 2 cases (1.3%, size D -1 case, size E -1 case) with trochlear dysplasia due to general overhanging. In conclusion, gender-specific design of Nexgen. ®. TKA was rarely necessary in 117 Korean women(151 knees); overhanging occurred in 7 knees (6 women) and gender-specific design was used in only two knees (1.3%) with trochlear dysplasia. Further research is obviously mandatory to assess the necessity of gender-specific design