NexGen LPS-Flex Research Articles

Preoperative predictors of implant size in patients undergoing total knee arthroplasty: a retrospective cohort study

BackgroundTraditionally, the size of total knee arthroplasty (TKA) components is predicted by preoperative radiographic templating, which is of limited accuracy. This study aimed to evaluate the role of demographic data and ankle volume in predicting implant size in TKA candidates.MethodsIn a retrospective study, 415 patients who underwent TKA at a single institution were included. The mean age of the patients was 67.5 ± 7.1 years. The mean BMI of the patients was 31.1 ± 4.7 kg/m2. TKA implants were Zimmer Biomet NexGen LPS-Flex Knee in all cases. The demographic data included age, sex, height, weight, BMI, ethnicity, and ankle volume. Ankle volume was assessed with the figure-of-eight method. Multivariate linear regression analysis was used for predicting factors of implant size.ResultsMultivariate linear regression analysis showed that the Sex (β:1.41, P < 0.001), height (β:0.058, P < 0.001), ankle volume (β:0.11, P < 0.001), and Age (β:0.017, P = 0.004) were significant predictors of tibial component size. Sex (β:0.89, P < 0.001), height (β:0.035, P < 0.001), and ankle volume(β:0.091, P < 0.001) were significant predictors of femoral component size in the multivariate analysis.ConclusionDemographic data, adjunct with the ankle volume, could provide a promising model for preoperative prediction of the size of tibial and femoral components in TKA candidates.

Total knee arthroplasty coronal alignment and tibial base stress-a new numerical evaluation.

Total knee arthroplasty (TKA) is one of the most frequently performed orthopedic procedures. The correct positioning and alignment of the components significantly affects prosthesis survival. Considering the current controversy regarding the target of postoperative alignment of TKA, this study evaluated the tension at tibial component interface using two numerical methods. The stress of the prosthesis/bone interface of the proximal tibial component was evaluated using two numerical methods: the finite element method (FEM) and the new meshless method: natural neighbor radial point interpolation method (NNRPIM). The construction of the model was based on Zimmers NexGen LPS-Flex Mobile® prosthesis and simulated the forces by using a free-body diagram. Tibiofemoral mechanical axis (TFMA) for which a higher number of nodes are under optimal mechanical tension is between 1° valgus 2° varus. For values outside the interval, there are regions under the tibial plate at risk of bone absorption. At the extremities of the tibial plate of the prosthesis, both medial and lateral, independent of the alignment, are under a low stress. In all nodes evaluated for all TFMA, the values of the effective stresses were higher in the NNRPIM when compared with the FEM. Through this study, we can corroborate that the optimal postoperative alignment is within the values that are currently considered of 0 ± 3° varus. It was verified that the meshless methods obtain smoother and more conservative results, which may make them safer when transposed to the clinical practice.

Is Highly Cross-Linked Polyethylene Safe for Use in High-Flexion Posterior Stabilized Total Knee Arthroplasty?

BackgroundApplication of highly cross-linked polyethylene (HXLPE) to a posterior cruciate-substituting total knee arthroplasty (TKA) might add the risk of fracture and failure of the tibial polyethylene insert. The purpose of this study is to evaluate the long-term (up to 19 years) clinical and radiographic results of posterior cruciate-substituting TKAs with HXLPE or conventional polyethylene. MethodsThis study analyzed the results of 1,217 patients (444 men and 773 women; mean age of 65 ± 7 years, range, 31-85) (2,434 knees) who had received a NexGen LPS-Flex prosthesis with a conventional tibial insert in one knee and the same prosthesis with an HXLPE tibial insert in the contralateral knee. The mean duration of follow-up was 17 years (range, 15-19). ResultsThe 2 groups did not differ significantly (P > .05) with regard to the clinical and radiographic results. No knee in either group had a fracture of the tibial polyethylene post or failure of the locking mechanism of the tibial polyethylene insert or osteolysis. Twenty-eight knees (2.3%) in the HXLPE group and 26 knees (2.1%) in the conventional polyethylene group were revised. The estimated survival rate at 17 years was 97.7% in the HXLPE group and 97.9% in the conventional polyethylene group. ConclusionThe data suggest that clinical and radiographic findings at a mean of 17 years after posterior cruciate-substituting TKA are the same for patients treated with HXLPE and those treated with conventional polyethylene.

The influence of alignment in long-term functional outcome of total knee arthroplasty.

This study aimed to analyze long-term survival rate and clinical outcomes of a NexGen LPS knee system. The effect of component alignment parameters on clinical scores and patient satisfaction was also investigated. Between June 2002 and January 2010, 204 knees of 152 patients underwent total knee arthroplasty with NexGen LPS-Flex knee system with fix bearings. The mean follow-up was 13.2 (range, 10 to 18 years). The relationship between radiologic and clinical results was investigated with component angles. Outlier angles were determined according to cutoff values of alpha, beta, gamma, and delta angles on the radiographs taken immediately after the operation. Knees were classified based on existing outliers they have as "No Outliers" (Group 1), "Single Outliers" (Group 2), and "Multiple Outliers" (Group 3). Revision surgery was required for ten patients, and the overall survival rate was 95.1% at the last follow-up. "Single Outliers" did not show a clinically significant difference in functional scores compared to the "No Outliers" group. However, KSKS and FJS-12 were significantly lower in "Multiple Outliers" knees (p: 0.039 and 0.019, respectively). NexGen LPS-Flex knee system has satisfactory results with 95.1% implant survival in 13.2 years. FJS-12 measurements at the end of the follow-up demonstrate a favourable result of the fixed bearing design. On two plane X-ray evaluations, components malaligned with two or more outliers in the same knee deteriorate patient satisfaction and clinical results.

Biomechanical effect of anatomical tibial component design on load distribution of medial proximal tibial bone in total knee arthroplasty

AimsThis 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).Methods3D 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.ResultsThe 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.ConclusionImplant 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.

Short- to Mid-Term Clinical Outcomes of Posterior-Stabilized Cementless Total Knee Arthroplasty with Trabecular Metal Components.

ObjectiveThis study aimed to evaluate the short- to mid-term clinical results of posterior-stabilized trabecular metal total knee arthroplasty (TKA) with cementless fixation of all components and investigate the radiographic changes of tibial and patellar components and cut bone surfaces over time.MethodsWe retrospectively collected the data of 128 knees from 88 consecutive patients who had undergone initial TKA with NexGen LPS-Flex TM implants. A total of 66 knees from 45 patients (mean ± standard deviation age: 70.3 ± 7.5 years) met the selection criteria, which had been employed cementless fixation of all parts and at least 3 years of postoperative follow-up duration. Clinical evaluations included range of motion, conventional knee score, function score, postoperative complications, and revision. For radiological evaluations, the bone contact surface of each implant was divided into 7 zones for tibial component and 2 zones for patellar component. Each region was examined immediately after surgery, at 6 and 12 months, and then every year afterwards.ResultsThe mean observation period of 45 subjects was 4.2 years. Adequate fixation of tibial components was maintained during follow-up, although the patellar components of 2 knees required revision after repeated falls. No loosening was observed in any implants. The initial gap in tibial components disappeared in all knees, and a reactive line remained in 4 knees. There were no revisions, except for 2 cases, which were ascribed to patellar component fracture caused by repeated falls.ConclusionCementless posterior-stabilized trabecular metal TKA appears to be a good surgical option. Longer-term examination for revision cases is required to validate our results.

Effects of different prosthetic instrumentations on tibial bone resection in total knee arthroplasty

Our aim was to assess the accuracy of the obtained posterior tibial slope (PTS) with a fixed angle cutting block. 247 TKAs in 213 patients were reviewed. We included 104 Legion Prosthesis, 76 U2 Knee Prosthesis, 46 NexGen LPS-Flex Prosthesis, and 21 Vanguard Knee System products. Preoperative and postoperative PTS were measured via expanded lateral tibia radiographs. For postoperative PTS, the Legion group had significantly smaller slopes than the U2 Knee group and Vanguard group. However, there was no significant difference between the Legion and NexGen groups, and no significant difference among the NexGen, U2 Knee, and Vanguard groups. Multiple linear regression showed that the different tibial lengths and preoperative PTS had statistically significant effects on postoperative PTS. However, there were weak correlations between the tibial length and PTS, and between preoperative and postoperative PTS. For TKA, although the PTS is not completely consistent with the angle of the cutting block, using conventional tibial bone resection technology with different tibial cutting instrumentations provided by various manufacturers in TKA can obtain safe PTS.

Mobile-bearing insert used with total knee arthroplasty does not rotate on the tibial tray during a squatting activity: a cross-sectional study

BackgroundTotal knee arthroplasty (TKA) is commonly performed around the world. Implant designs include fixed-bearing and mobile-bearing. Mobile-bearing design was developed as a rotating platform that allows axial rotation of the insert around the longitudinal axis. This phenomenon may limit full exploitation of the characteristics of the mobile-bearing insert, which may cause wearing and reduce longevity. However, there is limited knowledge on rotational behavior of the polyethylene mobile-bearing insert under weight-bearing conditions. We aimed at determining the rotational motion of each component at full extension and flexed positions during a squatting activity after TKA.MethodsThis study was a cross-sectional study (level 4) involving patients with severe knee osteoarthritis scheduled to receive TKA. We examined 13 knees of 11 patients after mobile-bearing TKA (NexGen LPS-Flex, Zimmer Inc.) at 10 weeks and 1 year postoperatively. Four identical metallic beads were embedded into the insert. Wide-base squatting was chosen for analyses. Three-dimensional in vivo poses of the prostheses were created using a 3D-to-2D registration technique. During flexion, rotation of the femoral component relative to the insert (FEM/INS) and tibial component (FEM/TIB) as well as insert rotation relative to the tibial component (INS/TIB) were computed. Repeated measure 2-way ANOVA and post hoc test was used.ResultsIn the fully extended position, FEM/INS was significantly smaller than INS/TIB both at 10 weeks (− 0.3° vs. 6.3°, p = .013) and 1 year (− 0.8° vs. 4.9°, p = .011), respectively. During the squatting activity, rotation motions of FEM/TIB, FEM/INS, INS/TIB were 5.7°, 5.9°, and 1.8° at 10 weeks and 6.3°, 5.5°, and 1.6° at 1 year, respectively. Rotation motion of FEM/INS was significantly greater than that of INS/TIB at both 10 weeks (p < .001) and 1 year (p < .001).ConclusionsThe mobile-bearing insert enhances the compatibility of FEM/INS in extension; the amount of INS/TIB rotation is significantly smaller than that of FEM/INS during a squatting activity. This information will inform surgeons to take caution to perform TKA with a fixed insert in which 6.3° of rotational offset would be added to the rotational alignment at FEM/INS at full extension.Trial registrationUMIN-CTR, UMIN000024196. Retrospectively registered on 9 September 2016.

Midterm Outcome of Total Knee Arthroplasty in East Coast Population of Hospital Tengku Ampuan Afzan Kuantan

Introduction: Total knee replacement (TKR) is an excellent advancement in medical treatment which gives good joint function and pain relief for degenerative diseases of joint since it was introduced in Malaysia since 1970. The purpose of this study was to evaluate the midterm functional outcome of patients undergone TKR using the NexGen LPS Flex prosthesis between January 2005 until April 2006 in primary osteoarthritis patients in our local east coast population. Materials and Methods: Forty six patients, 87% female (n=40) and 13% male (n=6), aged 54 to 81 (mean, 69±5.69) years underwent primary TKR using the hi-flex knee prosthesis (Zimmer) performed by two different surgeons were followed up for a minimal of five years. All used the same technique of surgery, medial parapatellar incision, cruciate substitute and cemented. Assesment were made based on the quality of life outcome score (SF-36) and the Oxford-12 knee scoring system questionnaires. Results: Oxford-12 revealed that patients had mild problems in terms of function and pain with the average function and pain score of 14.35±4.21 and 9.28±3.01 compared to a maximum possible score of 35 and 25 respectively. For eight health domains of SF-36, patients had the highest score (i.e. good health) for role emotional (RE), followed by mental health (MH), and social functioning (SF). This resulted in a higher score for mental component summary (MCS) than physical component summary (PCS). Since a low score of Oxford-12 indicates a better state of health compared to high score for SF-36, negative correlation between them was expected. Conclusion: The NexGen LPS-Flex TKR had good midterm functional outcome. Overall, TKR were found to be effective in terms of improvement in health-related quality-of-life dimensions.

Five cases of tibial post fracture in posterior stabilized total knee arthroplasty using Prolong highly cross-linked polyethylene

BackgroundFracture of a polyethylene tibial post after a posterior stabilized total knee arthroplasty (PS-TKA) is an uncommon but severe complication. We report five cases of non-traumatic fracture of a tibial polyethylene post that occurred with Prolong highly cross-linked polyethylene with the NexGen LPS-Flex total knee prosthesis. MethodsA Joint Reconstruction database for a high volume arthroplasty unit was used to identify all cases of revision of Prolong polyethylene used in PS-TKA. Five cases were identified as being revised because of a broken tibial post. ResultsAll five cases presented with a combination of sudden and increasing pain, instability and giving way, in previously well-functioning TKAs. There was no history of trauma or precipitating incident. Mean time from primary TKA to presentation and diagnosis of post fracture was 67.7 months (range 24–108). All five cases were successfully treated by revision, in the form of a liner exchange to a standard ultra-high molecular weight polyethylene (UHMWPE) bearing of the same thickness. The five cases occurred from a consecutive series of 955 total PS-TKAs with Prolong. This gives a conservative estimate of the frequency of this complication of 0.52%. This would give a risk of a tibial post fracture in approximately one in every 200 TKAs with this specific implant and bearing combination. ConclusionsTo our knowledge, this is the first report of a non-traumatic fracture to the tibial post with this bearing type. We would advocate against the routine use of Prolong highly crosslinked polyethylene in PS-TKA.

Impingement of the patellar component against the tibial post depends on the design of the post-cam mechanism: Comparison between 12 posterior stabilized total knee prostheses

BackgroundPatella–post impingement (PPI), contact of the patellar component with the tibial post, occurs during deep knee flexion after posterior stabilized total knee arthroplasty (TKA). In a previous pilot study, only two product lines were investigated. The aim of this study was to compare PPI between 12 contemporary posterior stabilized knee prostheses. MethodsTwelve posterior stabilized knee prostheses were implanted in full-length sawbone models of the femur and tibia using a navigation system. The distance between the lower edge of the patellar component and the cut surface of the tibia was defined as the tibial–patellar clearance (TPC), which represents the length of the patellar tendon. The TPC was set from 20 to 40 mm and the knee was moved from full extension to deep flexion while the knee angle at which PPI occurred (PPI angle) was recorded. ResultsThe PPI angle differed between prostheses (P < 0.05). Shorter TPCs resulted in smaller PPI angles and longer TPCs resulted in larger PPI angles (P < 0.05). To achieve more than 130° of flexion without PPI, the TPC should be prepared at a minimum of 20 mm for the NexGen LPS-Flex, Persona PS, Legion PS, and Evolution PS, 22 mm for the Attune RP and Journey II, 24 mm for the Triathlon PS, PFC Sigma PS, and Attune PS, and 26 mm for the NRG PS, Vanguard PS, and Vanguard RP. ConclusionsThe design of the tibial post significantly affects the PPI angle. To avoid PPI during deep flexion, appropriate TPC should be prepared during surgery.

Contraintes de contact articulaire fémorotibial dans les prothèses totales de genou à plateau fixe

BackgroundRotational allowance at the tibiofemoral joint would be required during deep flexion. However, the amount of flexion and rotation has not been investigated in modern total knee arthroplasty (TKA) designs. The present study aimed to determine the contact stress in five posterior-stabilized fixed-bearing TKA designs. HypothesisWe hypothesized that the contact area and stresses at the tibiofemoral articular surfaces vary according to the type of implant design and tested condition. Materials and methodsThe contact area and mean and peak contact stresses at the tibiofemoral articular surfaces were determined when a compressive load of 1200N was applied to a NexGen LPS Flex, Scorpio NRG, Genesis II, PFC Sigma, and Foundation implant. Measurements were performed at 0° and 45° flexion with 0°, 5°, 10°, and 15° rotation, and at 90° and 135° flexion with 0, 5°, 10°, 15°, and 20° rotation. ResultsThe LPS Flex showed that the femoral component could not achieve 20° rotation at 135° flexion. The Scorpio NRG showed less than 20MPa of contact stress at all conditions. The Genesis II showed higher contact stress than 20MPa at 135° flexion with 20° rotation. The PFC Sigma showed that the femoral component could not achieve >10° rotation at any flexion angle. The Foundation showed more than 20MPa of contact stress at 90° flexion with 20° rotation and at 135° flexion with 10°, 15°, and 20° rotation. DiscussionSurgeons should be more aware of the variable contact conditions of the tibiofemoral articular surfaces in individual TKA designs. Level of evidenceLevel IV, basic science study.

Total Knee Arthroplasty With Patellar Retention: The Severity of Patellofemoral Osteoarthritis Did Not Affect the Clinical and Radiographic Outcomes

BackgroundThe purpose of this study is to compare the clinical and radiographic outcomes of total knee arthroplasty (TKA) with patellar retention in accordance with the severity of patellofemoral arthritis. MethodsWe retrospectively reviewed patients who underwent TKA with patellar retention using the NexGen LPS or LPS-flex system between September 2010 and May 2015. The radiographic severity of patellofemoral arthritis was categorized according to the Iwano classification system, and subjects were divided into mild (stage 0-I) and moderate to severe (stage II-IV) groups. Clinical outcomes were evaluated using the Hospital for Special Surgery score, Knee Society Score, function score, Western Ontario and McMaster Universities Osteoarthritis Index, and Feller score. Radiographic outcomes were assessed using the congruence angle, patellar tilt angle, and lateral patellar displacement. The minimum follow-up for clinical and radiographic evaluation was 2 years. Clinical and radiographic outcomes were compared between the 2 groups preoperatively and at the time of the last follow-up. ResultsFour hundred seventy-four knees were enrolled and assigned to mild (n = 208) or moderate to severe (n = 266) groups. The preoperative Feller score was significantly lower in the moderate to severe group (P = .030), whereas the postoperative clinical and radiographic results did not differ significantly between the 2 groups. ConclusionClinical and radiographic outcomes did not differ in accordance with the severity of patellofemoral arthritis after a minimum 2 years of follow-up of patients treated with TKA with patellar retention. Good outcomes were obtained with patellar retention in TKA, even in patients with advanced patellofemoral osteoarthritis.

Variable tibiofemoral articular contact stress in fixed-bearing total knee arthroplasties.

Rotational allowance at the tibiofemoral joint would be required during deep flexion. However, the amount of flexion and rotation has not been investigated in modern total knee arthroplasty (TKA) designs. The present study aimed to determine the contact stress in five posterior-stabilized fixed-bearing TKA designs. We hypothesized that the contact area and stresses at the tibiofemoral articular surfaces vary according to the type of implant design and tested condition. The contact area and mean and peak contact stresses at the tibiofemoral articular surfaces were determined when a compressive load of 1200N was applied to a NexGen LPS Flex, Scorpio NRG, Genesis II, PFC Sigma, and Foundation implant. Measurements were performed at 0° and 45° flexion with 0°, 5°, 10°, and 15° rotation, and at 90° and 135° flexion with 0, 5°, 10°, 15°, and 20° rotation. The LPS Flex showed that the femoral component could not achieve 20° rotation at 135° flexion. The Scorpio NRG showed less than 20MPa of contact stress at all conditions. The GenesisII showed higher contact stress than 20MPa at 135° flexion with 20° rotation. The PFC Sigma showed that the femoral component could not achieve >10° rotation at any flexion angle. The Foundation showed more than 20MPa of contact stress at 90° flexion with 20° rotation and at 135° flexion with 10°, 15°, and 20° rotation. Surgeons should be more aware of the variable contact conditions of the tibiofemoral articular surfaces in individual TKA designs. Level IV, basic science study.

Radiographic evaluation of tibial component alignment in total knee arthroplasty following extramedullary and intramedullary tibial referencing

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; Long term survivorship of total knee arthroplasty (TKA) is significantly dependant on prostheses alignment. The debate on optimal referencing for femoral component is largely resolved with Intra-medullary jigs reproducing superior alignment. However there is still a contention about whether intramedullary or extramedullary jigs are better for tibial referencing. This study aims to compare the accuracy of tibial component alignment in TKA using intramedullary and extramedullary tibial referencing jigs.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; Between December 2012 and September 2014, 66 primary conventional cemented TKAs were performed using Nexgen-LPS Flex (Zimmer) implants in 55 patients, 50-80 y old (mean 65.54 y) with osteoarthritis/rheumatoid arthritis. Intramedullary and extramedullary tibial referencing was used in alternate patients undergoing TKA after excluding patients with BMI &lt;span style="text-decoration: underline;"&gt;&amp;gt;&lt;/span&gt;35 kg/m&lt;sup&gt;2&lt;/sup&gt;, knee deformity &lt;span style="text-decoration: underline;"&gt;&amp;gt;&lt;/span&gt;15&lt;sup&gt;0&lt;/sup&gt;,excessive tibial bowing, previous fractures/surgeries/retained metalwork around knee. Postoperatively, tibial component alignment (TCA) in coronal plane was assessed using AP radiograph of leg. A 3&lt;sup&gt;º&lt;/sup&gt; cutoff from neutral mechanical axis (i.e., 90&lt;sup&gt;o&lt;/sup&gt;±3&lt;sup&gt;o&lt;/sup&gt;) was considered acceptable.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; The intramedullary group (n=33) had 4 outliers (TCA &amp;gt;93&lt;sup&gt;º&lt;/sup&gt; or &amp;lt;87&lt;sup&gt;º&lt;/sup&gt;) whereas the extramedullary group (n=33) had 7 outliers (p=0.511). The difference in mean TCA between intramedullary and extramedullary groups was not statistically significant [90.70±2.43 and 90.55±2.17 (p=0.790)]. There were no significant per-operative/post-operative complications in either group.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; We conclude that both intramedullary and extramedullary tibial referencing guides can be used to achieve desired tibial component alignment (90±3&lt;sup&gt;º&lt;/sup&gt;) in TKA. However the surgeon should appreciate the benefits and deficiencies of either types of tibial referencing and use whichever is suited in a particular case. &lt;/p&gt;

The mid term functional outcomes of NexGen legacy posterior stabilized flex fixed bearing total knee replacement in primary osteoarthritis

Introduction: To evaluate the midterm functional outcomes of patients who had undergone total knee replacement (TKR) using posterior stabilized (PS) fixed bearing system from January 2005 until April 2006 for primary osteoarthritis of the knees. Methods: A retrospective study was done on forty-six patients, 87% female (n= 40) and 13% male (n=6), aged 54 to 81 years old (mean 69 ± 5.69) who had undergone primary TKR using the NexGen LPS-Flex Zimmer Warsaw. The patients were followed up for at least five years. A medial parapatellar approach and cemented posterior stabilized fixed bearing TKR system were used performed by one of two arthroplasty surgeons. All patients followed the same rehabilitation protocol post-operatively. Assessments were done using Oxford-12 knee scoring questionnaire to evaluate knee function and SF-36 to assess quality of life outcomes. Results: Oxford knee score revealed patients had lower (better) than average scores in terms of function (score 14.35 ± 4.21 out of 35) and pain (score 9.28 ± 3.01 out of 25). Analysis on the quality of life outcome score with SF-36 revealed a higher (better) score for mental component summary (MCS) relative to physical component summary (PCS). Patients had the highest score for role emotional (RE), followed by mental health (MH), and social functioning (SF). Conclusions: The NexGen LPS-Flex TKR produced a good functional outcome with minimal pain in the operated knee with better mental compared to physical health of patients in the midterm period post-total knee replacement.

Total knee arthroplasty using NexGen LPS-flex® improves clinical outcomes without early loosening: minimum 6-year follow-up results.

BackgroundThe authors analyzed clinical and radiological 6-year follow-up results after total knee arthroplasty (TKA) with NexGen LPS-flex® and implant survivorship.MethodsThe medical records of 80 patients that underwent 122 TKAs using NexGen LPS-flex® from February 2005 to November 2008 and followed up for at least 6 years were reviewed. The Internal Knee Documentation Committee (IKDC) subjective form, Western Ontario and McMaster Universities Arthritis Index (WOMAC), and Knee Injury and Osteoarthritis Outcome Score (KOOS) scores and preoperative and postoperative ranges of motion (ROMs) were recorded. Radiological assessments were performed by simple radiography preoperatively, immediately postoperatively, and at the final follow-up.ResultsAt the last follow-up visits, average ROM improved from 115.0° (80°–135°) to 131.76° (80°–150°), average IKDC subjective score from 30.54 (13–48) to 53.53 (31–80), average WOMAC score from 59.81 (35–90) to 15.98 (1–47), and average KOOS score from 75.33 (38–115) to 115.0 (52–174). The clinical results of 66 knees that had >130° of postoperative flexion and 56 knees that had <130 of postoperative flexion were compared. Radiolucent lines were found in 7 knees in those with a flexion angle of >130° and in 6 knees in those with a flexion angle of <130°, but the lines did not progress and meaningful loosening was not observed. Similarly, the occurrences of radiolucent lines in those with a flexion angle of >130° or <130° were not significantly different (p > 0.05).ConclusionsTKA with NexGen LPS-flex® showed satisfactory clinical improvements, including high flexion, and no early loosening was found at 6-year follow-up visits.

Mid-term survivorship of Mini-keel™ versus Standard keel in total knee replacements: Differences in the rate of revision for aseptic loosening

IntroductionTo reduce the size of the surgical incision, modular mini-keel tibial components have been developed with or without extensions for the Nexgen™ MIS Tibial Component. Although a smaller component could theoretically result in defective fixation, this has never been evaluated in a large comparative series. Thus, we performed the following case control study to: (1) evaluate intermediate-term survival of a modular “mini-keel” tibial component compared to a reference standard keel component from the same line of products (Nexgen LPS-Flex Tibial Component, Zimmer); (2) to identify any eventual associated factors if the frequency of loosening was increased. HypothesisThe rate of revision for aseptic tibial loosening is comparable for both components. Materials and methodsThis comparative, retrospective, single center series of 459 consecutive total knee arthroplasties (TKA) was performed between 2007 and 2010: with 212 modular “mini-keel” (MK) tibial components and 247 “standard” (S) components. Survival, rate of revision for aseptic tibial loosening and identification of a radiolucent line were analyzed at the final follow-up. ResultsAfter a median follow-up of 5years, the rate of revision for tibial aseptic loosing was significantly higher in the MK group with 12 cases (5.7%) and 4 cases in the S group (1.6%) (P=0.036). The use of the MK component appears to be a prognostic factor for surgical revision (hazard ratio=3.86 (1.23–11.88), P=0.02) but not for the development of a radiolucent line (HR=1.75 (0.9–3.4), P=0.097). The mean delay before revision was 38months (8–64) in the MK group and 15.2months (8–22) in the S group (P=0.006). Individual factors, such as gender, body mass index (BMI) and pre- or postoperative alignment were not prognostic factors for revision or radiolucent lines. ConclusionThe modular “mini-keel” tibial component was associated with a greater risk of revision for tibial component loosening. Level of evidenceCase control study, III.

Performing high flexion activities does not seem to be crucial in developing early femoral component loosening after high-flexion TKA.

BackgroundIt is still unclear whether high flexion (HF) activities correlated with the early loosening of the femoral component and whether HF activities are possible. We investigated what is the capability for performing various HF activities, and whether high flexion activities increase the chance of aseptic loosening after HF-TKA.MethodsWe retrospectively analysed 260 patients who underwent HF-TKA using the NexGen LPS Flex between 2001 and 2009. The mean follow-up was 6.7 years (range, 5–13). We evaluated range of motion, Knee Society scores, WOMAC, and serial radiographs for aseptic loosening. Responses to questions on individual HF activities were recorded on 5-point Likert scales based on difficulty (0–4). Patients were divided two groups based on their responses to squatting and kneeling, which were important weight-bearing HF activities in Asian population (HF group vs. non-HF group) for comparisons of aseptic loosening and clinical outcomes.ResultsMore than 80 % of patients positively responded for various HF activities. The capability of HF activities showed that cross-legged sitting, squatting, and kneeling were 97.7, 51.1 and 52.7 % at the latest follow-up, respectively. Aseptic loosening was identified in two tibial components (0.8 %) but none in femoral components in non-HF group. There was no significant difference of aseptic loosening based on HF activities (0.8% vs. 0%, p = 0.063).ConclusionsThe results of this study suggest that HF activities do not seem to be associated with aseptic loosening of femoral component after HF-TKA.

High-Flexion Total Knee Arthroplasty Using NexGen LPS-Flex System: Minimum 5-year Follow-up Results.

PurposeThis study is to report clinical and radiological results of high-flexion total knee arthroplasty (TKA) using NexGen LPS-flex system at a minimum 5-year follow-up, and to analyze the implant survivorship based on the results.Materials and MethodsA total of 80 patients (118 knees) who underwent patellar preserving TKA using NexGen LPS-flex implant between February 2007 and February 2008 and could be followed for minimum 5 years were reviewed. The range of motion (ROM), hip-knee-ankle angle, Knee Society Knee score (KSKS), and Knee Society Function score (KSFS) were assessed preoperatively and at the last follow-up and analyzed. Implant position of the femoral and tibial components on the immediate postoperative and last follow-up X-rays were compared.ResultsThe mean ROM was 110.2°±14.5° (range, 60° to 140°) preoperatively and 132.4°±5.2° (range, 90° to 145°) at the last follow-up. KSKS was 36.9°±6.4° preoperatively and 94.2°±3.2° at the last follow-up. KSFS was 30.5°±5.7° preoperatively and 93.7°±4.1° at the last follow-up. There was no statistically significant change in the implant position measured as α, β, γ, and δ angles at the last follow-up compared to the immediate postoperative values. Radiolucent lines were observed in 13 knees (11%) on the last follow-up X-rays. Revision TKA was performed due to aseptic implant loosening in 1 knee (0.84%), and the survival rate at the 5th postoperative year was 99.2%.ConclusionsThe clinical and radiological outcomes of high-flexion TKA using NexGen LPS-Flex implant design were satisfactory with 99.2% implant survival rate after 5 years of protected activities of daily living.