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William H Harris - One of the best experts on this subject based on the ideXlab platform.
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factors affecting cement strains near the tip of a cemented Femoral Component
Journal of Arthroplasty, 1997Co-Authors: Daniel M Estok, Tracy E Orr, William H HarrisAbstract:Abstract A generic three-dimensional finite-element model of the upper half of the femur containing a cemented Femoral stem of a total hip arthroplasty was developed to study those factors influencing cement strains near the tip of a cemented Femoral Component. This generic model was verified through another three-dimensional finite-element model that had been created based on the precise geometry of a cadaver femur implanted with a contemporary cemented Femoral Component. This cadaveric Femoral reconstruction had been created with strain gauges embedded in the cement mantle and was then loaded under conditions simulating single leg stance and stairclimbing. By use of the cement strains measured experimentally in the cadaver femur, and comparison of them with those obtained from the finite-element model of that cadaver femur, it was possible to establish proper material properties, boundary conditions, and loading conditions for the generic model. The generic model was then modified parametrically to determine those factors that influence the strains occurring within the cement mantle near the tip of a cemented Femoral Component. These models suggest that the single factor that most adversely influenced peak strains at or near the tip of the prosthesis was a thin cement mantle. This effect was present both when the cement mantle was reduced in thickness and when a similar effect occurred by virtue of a varus or valgus placement of the stem. Factors that decreased the peak cement strains near the tip of the Femoral stem included a more flexible stem and thicker cement mantles. This effect of a more flexible stem could be obtained by changing the modulus of the metal implant, by uniformly reducing the thickness of the stem, or by tapering the stem within the same bone geometry. Thicker cement mantles reduced both the axial and the shear strains occurring at the tip of the prosthesis. The presence or absence of a hole in the tip of the prosthesis per se, as for a centralizer, had no significant effect on the peak cement strains seen around the tip of the prosthesis; however, truncating the tip of the prosthesis from a hemisphere to a flat profile, which resulted in a sharp corner at the tip of the prosthesis, produced a 35% increase in cement strains at the tip as a result of a stress concentration effect. Thus, the common way of modifying the tip to have a hole for a centralizer, which involved truncating the tip, increased the cement strains occurring near the tip of the prosthesis.
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in vitro measurement of strain in the bone cement surrounding the Femoral Component of total hip replacements during simulated gait and stair climbing
Journal of Orthopaedic Research, 1996Co-Authors: Daniel O Oconnor, Dennis W. Burke, Murali Jasty, Ronald C Sedlacek, William H HarrisAbstract:The strains in the cement mantle surrounding the cemented Femoral Component of a total hip replacement were measured in vitro, using strain gauges embedded within the cement mantle adjacent to the Femoral Component in femurs from cadavers under physiologic loads simulating both single-limb stance and stair-climbing. Cement strains in the most proximal portion of the cement mantle were measured with and without full contact of the collar of the Femoral stem on the cortex of the medial portion of the Femoral neck during both loading conditions. To our knowledge, these are the first studies to contrast by direct measurement the strain profile in the cement mantle of a cemented Femoral Component under simulated stair-climbing with that occurring under simulated single-limb stance. They extend the findings from finite element analyses and from clinical specimens retrieved at autopsy in identifying those regions of the cement mantle most likely to fail. At two specific foci, the magnitude of the strain in the cement mantle approaches values that could lead to early fatigue failure of the cement. The two regions in which the strains were highest (greater than 1,000 microstrain) were the most proximal portions of the cement mantle and near the tip of the Femoral Component. Although these two regions are recognized areas of high strain and also common sites of cement debonding and cement mantle failure, the strain-gauge studies showed that the magnitude of cement strains in the proximal portion of the cement mantle were highest during stair-climbing; in contrast, high strains at the tip region occurred in both gait and stair-climbing. Contact between the collar and the medial portion of the Femoral neck reduced the strain in the proximal portion of the cement mantle not only in single-limb stance but in stair-climbing as well. The level of strain recorded in these studies for a simulated person weighing 115 pounds (52 kg) could lead to cement fracture during extended in vivo service life of a cemented Femoral Component, from either single-limb stance or stair-climbing. This risk would be increased if a void or defect existed in the cement mantle at these sites. Moreover, the increase in strain in the cement mantle was linear with increases in body weight between 100 and 200 pounds (45 and 91 kg) of spinal load, indicating that strains in a heavy patient could readily exceed the fatigue limit of the cement, particularly if a stress riser such as a pore in the cement or a sharp corner of the prosthesis were present. These data reemphasize the need to continue efforts to develop methods to strengthen bone cement and to reduce those factors that increase the strain in the cement mantle of cemented Femoral Components of total hip arthroplasty, particularly proximally and near the tip.
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revision of the Femoral Component of a total hip arthroplasty with the calcar replacement Femoral Component results after a mean of 10 8 years postoperatively
Journal of Bone and Joint Surgery American Volume, 1996Co-Authors: Jeffrey R Mclaughlin, William H HarrisAbstract:Patients who have major loss of bone in the region of the medial aspect of the Femoral neck, shortening of the limb, or a high center of the hip joint constitute a special challenge for surgeons performing revision total hip replacements. The use of a so-called calcar-replacement Femoral Component is one approach to these problems. Of forty-eight hips (forty-four patients) that had been treated consecutively with a total revision arthroplasty with insertion of a calcar-replacement Femoral Component with cement, thirty-eight hips (thirty-five patients) were followed for a mean of 10.8 years (range, 5.8 to 16.6 years). Ten of the forty-eight hips did not qualify for this study, including nine hips in eight patients who had died before the minimum five-year duration of follow-up and one hip in a patient who had refused follow-up. Of the thirty-eight hips that were followed, seven (18 per cent) had had a repeat revision because of aseptic loosening of the Femoral Component, one (3 per cent) had been revised again because of lysis around a well fixed Femoral Component, and an additional four (11 per cent) had a Component that was loose according to radiographic criteria. Thus, twenty-six (68 per cent) of the thirty-eight index Femoral Components were rigidly fixed according to radiographic criteria, and thirty (79 per cent) were still in place. The clinical results were very good for the thirty hips that had not been revised. The mean Harris hip-rating for these patients increased from 50 points preoperatively to 84 points at the most recent follow-up evaluation.
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revision total hip arthroplasty with use of so called second generation cementing techniques for aseptic loosening of the Femoral Component a fifteen year average follow up study
Journal of Bone and Joint Surgery American Volume, 1996Co-Authors: William F Mulroy, William H HarrisAbstract:We reviewed the results in a consecutive series of forty-three unselected hips (forty-one patients) after revision of the Femoral Component, because of aseptic loosening, with use of so-called second-generation cementing techniques. This series was previously reported on after average follow-up intervals of six and 11.7 years; we now report the results after an average duration of follow-up of 15.1 years (range, 14.2 to 17.5 years). None of the eight patients (eight hips) who had died before this review had had a reoperation. Over the course of the study period, repeat revision was done after four (11 per cent) of the thirty-six index procedures that were the first Femoral revision and after three of the seven that were a second or third revision. Of the thirty-five hips in the thirty-three surviving patients, seven (20 per cent) had a repeat revision of the Femoral Component because of aseptic loosening. The average age at the time of the index revision for this group of patients was fifty-one years. This young age has been associated with distinctly poorer results after revision. In two additional hips (two patients), there was radiographic evidence of loosening of the Femoral Component. Therefore, the rate of loosening of the Femoral Component was 26 per cent (nine of thirty-five hips) at an average of 15.1 years. These results support the concept that so-called second-generation cementing techniques have decreased the prevalence of aseptic loosening after Femoral revision, compared with the shorter-term results that have been reported after revision with use of so-called first-generation cementing techniques.
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Femoral Component Offset Its Effect on Strain in Bone-Cement
Journal of Arthroplasty, 1993Co-Authors: J. Rod Davey, Dennis W. Burke, Daniel O. O'connor, William H HarrisAbstract:Abstract The magnitude of the offset of the Femoral prosthesis strongly influences the mechanics of the hip following a total hip arthroplasty. An increased offset increases the moment arm of the abductor muscles. This reduces the abductor force required for normal gait and, consequently, reduces the resultant force across the hip joint. These factors are advantageous. However, increased offset also increases the bending moment on the implant, which could adversely increase the strain in the medial cement mantle. to evaluate the relative advantages and disadvantages of these conflicting results of increasing the offset of the Femoral Component the authors measured in vitro in cadaver femora the effect of differing offsets of the Femoral Component on strain in the cement mantle. After testing the intact femora, the authors cemented Femoral prostheses in place and quantified the abductor force, resultant force, and strain in the cement mantle under loading conditions simulating single limb stance at different Femoral offset levels. The reduction in both abductor and resultant force was substantial with increased Femoral Component offset, but the strain in the cement of the proximal medial portion of the cement mantle was not significantly increased
Nico Verdonschot - One of the best experts on this subject based on the ideXlab platform.
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a preclinical numerical assessment of a polyetheretherketone Femoral Component in total knee arthroplasty during gait
Journal of Experimental Orthopaedics, 2017Co-Authors: Lennert De Ruiter, Dennis Janssen, Nico Verdonschot, Adam BriscoeAbstract:Conventional total knee replacement designs show high success rates but in the long term, the stiff metal Components may affect bone quality of the distal femur. In this study we introduce an all-polymer total knee replacement device containing a PEEK Femoral Component on an UHMWPE tibial implant and study its mechanical integrity, fixation, and stress shielding of the periprosthetic femur. The implant was analysed in finite element simulations of level gait, adopted from the ISO 14243-1 standard. Mechanical integrity of the implant and underlying cement mantle were tested, and the fixation strength of the cement-implant interface was studied. Stress shielding was assessed based on strain energy density distributions in the distal femur. We compared PEEK and CoCr implants for mechanical performance and fixation, and compared both versions against an intact case to determine the change in bone strain energy density. The mechanical integrity of the PEEK and CoCr Components was similar in magnitude, but differences in stress patterns were found. Moreover, the cement mantle was loaded more heavily in the CoCr configuration. Under similar interface properties, the CoCr-cement interface was more at risk of failure than the PEEK-cement interface. The bone strain energy density distribution of the PEEK implant was similar to the intact case, while the CoCr implant showed signs of stress shielding, and a different distribution than the intact and PEEK models. During gait, the PEEK Femoral Component performed similarly to CoCr, with no added risk for the cement mantle. The reduction in stress shielding for PEEK was evident and confirms the potential reduction in long-term loss of bone stock for this all-polymer knee implant.
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does high flexion total knee arthroplasty promote early loosening of the Femoral Component
Journal of Orthopaedic Research, 2011Co-Authors: J Zelle, Dennis Janssen, Jolanda Van Eijden, Maarten C De Waal Malefijt, Nico VerdonschotAbstract:High-flexion knee replacements have been developed to accommodate a large range of motion (RoM > 120°). Knee implants that allow for higher flexion may be more sensitive to Femoral loosening as the knee load is relatively high during deep knee flexion, which could result in an increased failure potential at the implant–cement interface of the Femoral Component. A 3D finite element knee model was developed including a posterior-stabilized high-flexion knee replacement to analyze the stress state at the Femoral implant–cement interface during a full squatting movement (RoM ≤ 155°). During deep flexion (RoM > 120°), tensile and shear stress concentrations were found at the implant–cement interface beneath the proximal part of the anterior flange. Particularly, the shear stresses at this interface location increased during high flexion, from a peak stress of 4.03 MPa at 90° to 6.89 MPa at 140° of flexion. Tensile stresses were substantially lower, having a peak stress of 0.72 MPa at 100° of flexion. Using data from earlier interface strength experiments, none of the interface beneath the anterior flange was predicted to fail in the normal flexion range (RoM ≤ 120°), whereas the prediction increased to 2.2% of the interface during deeper knee flexion. Thigh-calf contact reduced the knee forces, interface load, and failure risk beyond 140–145° of flexion. Based on the more critical stresses at the Femoral fixation site between 120° and 145° of flexion, we conclude that the Femoral Component has a higher risk of loosening at high-flexion angles. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 976–983, 2011
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Femoral Component revision with use of impaction bone grafting and a cemented polished stem
Journal of Bone and Joint Surgery American Volume, 2005Co-Authors: Willem B Schreurs, Nico Verdonschot, J Chris J Arts, Pieter Buma, T J J H Slooff, J W M GardeniersAbstract:BACKGROUND: The purpose of this study was to evaluate the clinical and radiographic outcomes of revision of the Femoral Component of a hip arthroplasty with use of an impaction bone-grafting technique and a cemented polished stem. METHODS: Thirty-three consecutive Femoral reconstructions that were performed between March 1991 and February 1996 with use of the X-change Femoral revision system, fresh-frozen morselized allograft, and a cemented polished Exeter stem were followed prospectively. Femoral bone stock defects were classified according to the Endoklinik classification. The average age of the patients at the time of the Femoral Component revision was sixty-three years. No patient was lost to follow-up, which was performed at a minimum of eight years, but eight patients had died. None of the deaths was related to the surgery. RESULTS: No Femoral reconstruction had been rerevised at a mean of 10.4 years postoperatively. There was one unrecognized intraoperative fracture, which healed following nonoperative treatment. There were three postoperative Femoral fractures, all through cortical defects at the level of the tip of the prostheses. All fractures healed after plate fixation, and all Femoral implants were left in situ. The average subsidence of the stem within the cement mantle was 3 mm; seven stems migrated 5 mm. The average Harris hip score improved from 49 points prior to surgery to 85 points (range, 68 to 100 points) at the time of this review. Subsidence did not affect the Harris hip score. Kaplan-Meier analysis, with an end point of Femoral revision for any reason, showed a survival rate of 100% (one-sided 95% confidence interval, 100% to 91.3%). CONCLUSIONS: Femoral revision with use of an impaction bone-grafting technique and a cemented polished stem resulted in an excellent prosthetic survival rate at eight to thirteen years postoperatively. The major problem that occurred was a Femoral fracture in four patients.
Johan Bellemans - One of the best experts on this subject based on the ideXlab platform.
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is adapted measured resection superior to gap balancing in determining Femoral Component rotation in total knee replacement
Journal of Bone and Joint Surgery-british Volume, 2012Co-Authors: Thomas Luyckx, Jan Victor, Tom Peeters, Hilde Vandenneucker, Johan BellemansAbstract:Obtaining a balanced flexion gap with correct Femoral Component rotation is one of the prerequisites for a successful outcome after total knee replacement (TKR). Different techniques for achieving this have been described. In this study we prospectively compared gap-balancing versus measured resection in terms of reliability and accuracy for Femoral Component rotation in 96 primary TKRs performed in 96 patients using the Journey system. In 48 patients (18 men and 30 women) with a mean age of 65 years (45 to 85) a tensor device was used to determine rotation. In the second group of 48 patients (14 men and 34 women) with a mean age of 64 years (41 to 86), an 'adapted' measured resection technique was used, taking into account the native rotational geometry of the femur as measured on a pre-operative CT scan. Both groups systematically reproduced a similar external rotation of the Femoral Component relative to the surgical transepicondylar axis: 2.4° (SD 2.5) in the gap-balancing group and 1.7° (SD 2.1) in the measured resection group (p = 0.134). Both gap-balancing and adapted measured resection techniques proved equally reliable and accurate in determining Femoral Component rotation after TKR. There was a tendency towards more external rotation in the gap-balancing group, but this difference was not statistically significant (p = 0.134). The number of outliers for our 'adapted' measured resection technique was much lower than reported in the literature.
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Femoral Component loosening in high flexion total knee replacement an in vitro comparison of high flexion versus conventional designs
Journal of Bone and Joint Surgery-british Volume, 2011Co-Authors: P Bollars, Jp Luyckx, Bernardo Innocenti, Luc Labey, Jan Victor, Johan BellemansAbstract:High-flexion total knee replacement (TKR) designs have been introduced to improve flexion after TKR. Although the early results of such designs were promising, recent literature has raised concerns about the incidence of early loosening of the Femoral Component. We compared the minimum force required to cause Femoral Component loosening for six high-flexion and six conventional TKR designs in a laboratory experiment. Each TKR design was implanted in a Femoral bone model and placed in a loading frame in 135° of flexion. Loosening of the Femoral Component was induced by moving the tibial Component at a constant rate of displacement while maintaining the same angle of flexion. A stereophotogrammetric system registered the relative movement between the Femoral Component and the underlying bone until loosening occurred. Compared with high-flexion designs, conventional TKR designs required a significantly higher force before loosening occurred (p < 0.001). High-flexion designs with closed box geometry required significantly higher loosening forces than high-flexion designs with open box geometry (p = 0.0478). The presence of pegs further contributed to the fixation strength of Components. We conclude that high-flexion designs have a greater risk for Femoral Component loosening than conventional TKR designs. We believe this is attributable to the absence of Femoral load sharing between the prosthetic Component and the condylar bone during flexion.
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the influence of malrotation of the Femoral Component in total knee replacement on the mechanics of patelloFemoral contact during gait an in vitro biomechanical study
Journal of Bone and Joint Surgery-british Volume, 2010Co-Authors: Christophe Verlinden, Luc Labey, Johan Bellemans, Pieter Uvin, Jeanphilippe Luyckx, Hilde VandenneuckerAbstract:Malrotation of the Femoral Component is a cause of patelloFemoral maltracking after total knee arthroplasty. Its precise effect on the patelloFemoral mechanics has not been well quantified. We have developed an in vitro method to measure the influence of patellar maltracking on contact. Maltracking was induced by progressively rotating the Femoral Component either internally or externally. The contact mechanics were analysed using Tekscan. The results showed that excessive malrotation of the Femoral Component, both internally and externally, had a significant influence on the mechanics of contact. The contact area decreased with progressive maltracking, with a concomitant increase in contact pressure. The amount of contact area that carries more than the yield stress of ultra-high molecular weight polyethylene significantly increases with progressive maltracking. It is likely that the elevated pressures noted in malrotation could cause accelerated and excessive wear of the patellar button.
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an algorithm for the surgical treatment of periprosthetic fractures of the femur around a well fixed Femoral Component
Journal of Bone and Joint Surgery-british Volume, 2009Co-Authors: Kristoff Corten, Johan Bellemans, F Vanrykel, Reynders P Frederix, J P Simon, Paul BroosAbstract:The use of plate-and-cable constructs to treat periprosthetic fractures around a well-fixed Femoral Component in total hip replacements has been reported to have high rates of failure. Our aim was to evaluate the results of a surgical treatment algorithm to use these lateral constructs reliably in Vancouver type-B1 and type-C fractures. The joint was dislocated and the stability of the Femoral Component was meticulously evaluated in 45 type-B1 fractures. This led to the identification of nine (20%) unstable Components. The fracture was considered to be suitable for single plate-and-cable fixation by a direct reduction technique if the integrity of the medial cortex could be restored. Union was achieved in 29 of 30 fractures (97%) at a mean of 6.4 months (3 to 30) in 29 type-B1 and five type-C fractures. Three patients developed an infection and one construct failed. Using this algorithm plate-and-cable constructs can be used safely, but indirect reduction with minimal soft-tissue damage could lead to shorter times to union and lower rates of complications.
Shuichi Matsuda - One of the best experts on this subject based on the ideXlab platform.
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excessive flexed position of the Femoral Component was associated with poor new knee society score after total knee arthroplasty with the bi surface knee prosthesis
Journal of Bone and Joint Surgery-british Volume, 2020Co-Authors: Kohei Nishitani, Naoki Umatani, Shinichi Kuriyama, Shinichiro Nakamura, Shuichi MatsudaAbstract:Aims This study aimed to evaluate the association between the sagittal alignment of the Femoral Component in total knee arthroplasty (TKA) and new Knee Society Score (2011KSS), under the hypothesis...
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mid and long term results of Femoral Component revision using the cement in cement technique average 10 8 year follow up study
Journal of Orthopaedic Science, 2016Co-Authors: Yaichiro Okuzu, Koji Goto, Yutaka Kuroda, Shuichi MatsudaAbstract:Abstract Background Few reports are available on the long-term outcomes of Femoral Component revision by using the cement-in-cement technique. We report the mid- and long-term results of Femoral Component revision in total hip arthroplasty using the cement-in-cement technique. Methods Between April 1996 and June 2009, 62 consecutive total hip arthroplasties with Femoral Component revision were performed in 57 patients by using the cement-in-cement technique. We retrospectively reviewed the cases with a follow-up period of at least five years. Three patients died, and two were lost to follow-up. Thus, 52 patients (57 hips), comprising 51 women and one man, were followed for average 10.8 years. Results The mean Japanese Orthopaedic Association hip score improved from 57.6 points (range, 28–95 points) preoperatively to 79.8 points (range, 52–98 points) at one year postoperatively and to 77.4 points (range, 59–96 points) at the final follow up. Three revisions of the Femoral Component were necessary. One of the causes for the revision was a periprosthetic infection that occurred 20 months postoperatively. Another was aseptic loosening that occurred 99 months postoperatively and required revision of the acetabular Component. The well-fixed Femoral Component was revised using the cement-in-cement technique at time of the acetabular revision. The third case was aseptic loosening of the Femoral Component that occurred 84 months postoperatively. The five-, 10-, and 15-year survival rates for the Femoral re-revision due to any reason were 98.4%, 94.0%, and 94.0%, respectively. Conclusion Use of the cement-in-cement technique for revision total hip arthroplasty resulted in good mid- and long-term radiological and clinical outcomes.
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internal rotation of Femoral Component affects functional activities after tka survey with the 2011 knee society score
Journal of Arthroplasty, 2014Co-Authors: Shinya Kawahara, Shigetoshi Okamoto, Hiroyuki Nakahara, Ken Okazaki, Shuichi Matsuda, Yukihide IwamotoAbstract:Abstract The 2011 Knee Society Knee Scoring System (KSS) was developed as a new patient-derived outcome measure to better characterize satisfaction, expectations, and physical activities after total knee arthroplasty. The rotational alignment of the Femoral and tibial Components was assessed with computed tomography in 75 patients (92 knees), and its effect on the scores of the KSS was evaluated. Internal rotation of the Femoral Component relative to the surgical epicondylar axis significantly decreased the score of functional activities and slightly decreased the score of satisfaction. Femoral Component malrotation did not affect the scores of symptoms and expectations. Tibial Component malrotation did not affect any of the scores of the 2011 KSS. Surgeons should avoid internal rotation of the Femoral Component to preserve functional activities.
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upsizing the Femoral Component increases patelloFemoral contact force in total knee replacement
Journal of Bone and Joint Surgery-british Volume, 2012Co-Authors: Shinya Kawahara, Hiroyuki Nakahara, Shuichi Matsuda, Shingo Fukagawa, Hiromichi Mitsuyasu, Hidehiko Higaki, Takeshi Shimoto, Yukihide IwamotoAbstract:In posterior stabilised total knee replacement (TKR) a larger Femoral Component is sometimes selected to manage the increased flexion gap caused by resection of the posterior cruciate ligament. However, concerns remain regarding the adverse effect of the increased anteroposterior dimensions of the Femoral Component on the patelloFemoral (PF) joint. Meanwhile, the gender-specific Femoral Component has a narrower and thinner anterior flange and is expected to reduce the PF contact force. PF contact forces were measured at 90°, 120°, 130° and 140° of flexion using the NexGen Legacy Posterior Stabilized (LPS)-Flex Fixed Bearing Knee system using Standard, Upsized and Gender Femoral Components during TKR. Increasing the size of the Femoral Component significantly increased mean PF forces at 120°, 130° and 140° of flexion (p = 0.005, p < 0.001 and p < 0.001, respectively). No difference was found in contact force between the Gender and the Standard Components. Among the patients who had overhang of the Standard Component, mean contact forces with the Gender Component were slightly lower than those of the Standard Component, but no statistical difference was found at 90°, 120°, 130° or 140° of flexion (p = 0.689, 0.615, 0.253 and 0.248, respectively). Upsized Femoral Components would increase PF forces in deep knee flexion. Gender-specific implants would not reduce PF forces.
Seung Baik Kang - One of the best experts on this subject based on the ideXlab platform.
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high incidence of loosening of the Femoral Component in legacy posterior stabilised flex total knee replacement
Journal of Bone and Joint Surgery-british Volume, 2007Co-Authors: Seung Baik Kang, Kang Sup YooAbstract:We have examined the results obtained with 72 NexGen legacy posterior stabilised-flex fixed total knee replacements in 47 patients implanted by a single surgeon between March 2003 and September 2004. Aseptic loosening of the Femoral Component was found in 27 (38%) of the replacements at a mean follow-up of 32 months (30 to 48) and 15 knees (21%) required revision at a mean of 23 months (11 to 45). We compared the radiologically-loose and revised knees with those which had remained well-fixed to identify the factors which had contributed to this high rate of aseptic loosening. Post-operatively, the mean maximum flexion was 136° (110° to 140°) in the loosened group and 125° (95° to 140°) in the well-fixed group (independent t -test, p = 0.022). Squatting, kneeling, or sitting cross-legged could be achieved by 23 (85%) of the loosened knees, but only 22 (49%) of the well-fixed knees (chi-squared test, p = 0.001). The loosened Femoral Components were found to migrate into a more flexed position, but no migration was detected in the well-fixed group. These implants allowed a high degree of flexion, but showed a marked rate of early loosening of the Femoral Component, which was associated with weight-bearing in maximum flexion.
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high incidence of loosening of the Femoral Component in legacy posterior stabilised flex total knee replacement
Journal of Bone and Joint Surgery-british Volume, 2007Co-Authors: Hyuk Soo Han, Seung Baik Kang, Kang Sup YoonAbstract:We have examined the results obtained with 72 NexGen legacy posterior stabilised-flex fixed total knee replacements in 47 patients implanted by a single surgeon between March 2003 and September 2004. Aseptic loosening of the Femoral Component was found in 27 (38%) of the replacements at a mean follow-up of 32 months (30 to 48) and 15 knees (21%) required revision at a mean of 23 months (11 to 45). We compared the radiologically-loose and revised knees with those which had remained well-fixed to identify the factors which had contributed to this high rate of aseptic loosening. Post-operatively, the mean maximum flexion was 136 degrees (110 degrees to 140 degrees) in the loosened group and 125 degrees (95 degrees to 140 degrees) in the well-fixed group (independent t-test, p = 0.022). Squatting, kneeling, or sitting cross-legged could be achieved by 23 (85%) of the loosened knees, but only 22 (49%) of the well-fixed knees (chi-squared test, p = 0.001). The loosened Femoral Components were found to migrate into a more flexed position, but no migration was detected in the well-fixed group. These implants allowed a high degree of flexion, but showed a marked rate of early loosening of the Femoral Component, which was associated with weight-bearing in maximum flexion.
