Article

A Prospective Randomized Controlled Trial Comparing Medial-Pivot versus Posterior-Stabilized Total Knee Arthroplasty

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Abstract

Background The medial-pivot (MP) system for total knee arthroplasty (TKA) aims to restore more natural “ball and socket” knee kinematics compared to the traditional posterior-stabilized (PS) implants for TKA. The objective of this study was to determine if there was any difference in functional outcomes between patients undergoing MP-TKA versus PS-TKA. Methods This prospective randomized control trial consisted of 43 patients undergoing MP-TKA versus 45 patients receiving a single radius PS TKA design. The primary outcome was post-operative range of motion (ROM). Secondary outcomes included the Western Ontario and McMaster Universities Arthritis Index (WOMAC), Oxford Knee Score (OKS), Knee Society Score (KSS), and radiological outcomes. All study patients were followed-up for two years after surgery. Results Patients undergoing MP-TKA had comparable ROM at one-year (114.6° ± 16.3° vs. 111.3° ± 17.8° respectively, p = 0.88) and two-years after surgery (114.9° ± 15.5° vs. 114.9° ± 16.4° respectively, p = 0.92) compared to PS-TKA. There were also no differences in WOMAC (26.8 ± 19.84 vs. 22.0 ± 12.03 respectively, p = 0.14), OKS (42.7 ± 8.1 vs. 42.3 ± 6.7 respectively, p = 0.18), and KSS clinical scores (82.9 ± 16.96 vs. 81.42 ± 10.45 respectively, p = 0.12) and KSS functional scores (76.2 ± 18.81 vs. 73.93 ± 8.53 respectively, p = 0.62) at two-years follow-up. There was no difference in post-operative limb alignment or complications. Conclusion This study demonstrated excellent results in both the single-radius PS-TKA design and MP-TKA design. No differences were identified at 2-year follow-up with respect to post-operative ROM and PROMs.

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... Moreover, patient-reported outcome measures, postoperative limb alignment or complications offered no statistically significant differences. [55] Therefore, as these two RCTs yielded quite heterogeneous results, future studies with larger patient collectives will be necessary to confirm the significance of these findings from previous RCTs. ...
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Introduction The aim of this study was to compare the use of mobile-bearing, fixed-bearing, posterior-stabilized (PS) and medial pivot design to describe epidemiological differences and subsequent outcomes. Materials and methods A systematic literature search was performed using the NORE website to identify the relevant arthroplasty registers. Inclusion criteria were the following: (1) reports had to be publicly available, (2) reports had to be written in German or English language, (3) differentiation between mobile- and fixed-bearing, posterior-stabilized, and if possible, medial pivot designs had to be possible from the present reports, and (4) data had to be reported for at least three consecutive years and the latest report had to be from the year 2020 to retrieve recent data. Results Six registries (England and Wales, Australia, Norway, New Zealand, Germany, Switzerland) offered sufficient data according to the inclusion criteria. In all countries, the dominant type of bearing used for total knee arthroplasty (TKA) was fixed-bearing, with percentages ranging from 60.8% to 84.1% in 2018, 63.6% to 85.7% in 2019 and 66.2% to 87.4% in 2020. A large variation was observed concerning mobile-bearing design, which showed a range from 2.8% to 39.2% in 2018, 2.6% to 36.4% in 2019 and 2.9% to 33.8% in 2020. Some variation was found regarding the use of PS TKA, as its percentage frequency ranged from 9.7% to 29.2% in 2018, 9.8% to 29.4% in 2019 and 10.1% to 28.5% in 2020. Medial pivot design had a share of 9.1% in 2018, 8.6% in 2019 and 8.4% in 2020 in Australia, while it only accounted for 1.4% in 2018, 2.1% in 2019 and 2.5% in 2020 in Germany. Conclusion The comparison of arthroplasty registers from England and Wales, Australia, Norway, New Zealand, Germany and Switzerland revealed large differences regarding the application of posterior-stabilized designs, but also common ground considering the overwhelming use of fixed-bearing inserts, which, when inserted correctly, eradicate the potential complication of bearing dislocation. Arthroplasty registers offer a real-world clinical perspective with the aim to improve quality and patient safety.
Article
Introduction: Randomized controlled trials (RCTs)are regarded as highest level of scientific evidence. There is belief that while prospective randomized control trials (PRCTs) are the gold standard for evaluating efficacy of interventions, there are very few conducted on lower extremity joint arthroplasty. However, there was a more than adequate amount (n=197) of published RCTs in knee arthroplasty during the 2021 calendar year. Therefore, we studied RCTs on knee arthroplasties for 2021 and assessed them for overall study topic reasons (i.e., devices as well as prostheses, rehabilitation, pain control, blood loss [tranexamic acid], and other), which were then subcategorized by: (1) country of origin; (2) sample size; and (3)whether or not they were follow-up studies. After this, we specifically focused on the studies (n=26) concerning devices or prostheses. Methods: A search of PubMed on “knee arthroplasty” specifying “RCT” using their search function and dates between January 1, 2021 to December 24, 2021 resulted in the analyzed reports. A total of 17.3% reports analyzed rehabilitation methods while 28.4% studied pain control. A total of 20.3% examined blood loss topics and 20.8% investigated other topics. Results: We found that 26 studies (13.2%) involved prosthetic design and implantation. Overall, only 15% knee arthroplasty RCTs were conducted in the United States, the mean total final sample size was 133±146 patients, and 7% were follow-up studies. None of the prostheses studies were performed in the United States, and the mean total final sample size of all of these studies was 86±54 patients, and 23% were follow-up studies. Total knee arthroplasty prospective RCTs were not performed in the United States. Conclusion: The authors believe that other study designs, such as database or registry analyses, are also appropriate in this rapidly advancing field of joint arthroplasty for the continuing evaluation and approval of new prostheses and techniques, while we await more PRCTs in our field.
Article
Background: Studies of clinical outcomes that compare the Medial Pivot design (MP) with the Posterior-Stabilized design (PS) were controversial. The meta-analysis was performed to summarize existing evidence, aiming to determine whether MP was superior to PS prosthesis. Methods: Search strategies followed the recommendations of the Cochrane collaboration. Electronic searches such as PubMed, Embase, Web of Science, and Cochrane were systematically searched for publications concerning medical pivot and posterior stabilized prosthesis from the inception date to April 2021. Authors also manually checked and retrieved a reference list of included publications for potential studies, which the electronic searches had not found. Two investigators independently searched, screened, and reviewed the full text of the article. Disagreements generated throughout the process were resolved by consensus, and if divergences remain, they were arbitrated by a third author. Subsequently, patients were divided into the MP and PS groups. Results: This study included 18 articles, comprising a total of 2614 patients with a similar baseline. The results showed the PS group had a higher risk of the patellar clunk or crepitus. However, the theoretical advantages of MP prosthesis could not translate to the difference in knee function, clinical complications, revision rate and satisfaction. Similarly, the shape and mechanism of prostheses could not affect the implant position and postoperative alignment. Conclusions: The MP prosthesis can reduce the patellar clunk or crepitus rate. However, choices between the MP and PS prosthesis would not affect knee function, clinical complications, revision rate, patient satisfaction, implant position, and postoperative alignment.
Article
Background Multiple options are available for the tibial insert in total knee arthroplasty (TKA). A systematic review (SR) and network meta-analysis (NMA) to compare available randomized controlled trials (RCTs) could assist with decision making. We aim to show that designs with increased conformity may improve function and satisfaction without an increase in complications though posterior stabilized (PS) inserts will likely have more flexion. Methods A search of MEDLINE, EMBASE, and the Cochrane Library was performed. Studies were limited to RCTs evaluating cruciate retaining (CR), PS, anterior stabilized (AS), medial pivot (MP), bicruciate retaining (BR), and bicruciate stabilizing (BCS) inserts. Mean differences (MD) were used for patient reported outcome measures (PROMs) and odds ratios (OR) for reoperation rates and MUA. A systematic review was performed for satisfaction. Results 27 trials were identified. The NMA showed no difference from a statistical or clinical standpoint for PROMs evaluated. There was a statistical difference for increased flexion for PS knees (3 degrees p 0.04). There were no differences in the MUA or reoperation rates. There was insufficient information to determine if a specific insert improved satisfaction. Discussion The results of this NMA show no statistical or clinical difference in PROMs. There was higher flexion for PS knees though the amount was not clinically significant. There was insufficient data for conclusions on patient satisfaction. Therefore, the surgeon should evaluate the clinical situation to determine the best insert rather than choose and insert based on functional scores, patient satisfaction, or complication rates.
Article
Background Instability after primary TKA is a frequent reason for revision surgery. Other mechanisms of failure must be ruled out before an in-depth analysis of instability.DiagnosticsDiagnostic tools for instability consist of medical history, clinical examination, and imaging. The clinical examination must focus primarily on the extent of the instability, the location of the instability and the levels of instability. Varus and valgus stress radiographs in the mediolateral plane in extension and flexion, as well as anteroposterior stress images (drawer) are mandatory. In addition, the underlying cause (or a combination of causes) must be defined. Possible causes include malalignment, component malposition (rotation), bony and ligamentous insufficiencies and implant-associated instabilities.TherapyOnce the mechanism of failure is understood in detail, various therapeutic options are available. Conservative therapy is only considered in patients where there is borderline instability, and the patient has adequate compensatory options in daily life. Some authors postulate the need for 3 months of conservative therapy in every case before possible surgery. Isolated inlay exchange is usually only a compromise and shows failure rates of up to 60%. Partial component exchange requires some preconditions and is technically demanding.ResultsIf the indication is correct, the results are consistently comparable with those after full component revision. In the case of full component revision, attention must be paid to the degree of constraint to achieve stability but also to avoiding over-treatment (too highly constrained TKA with an probability of loosening). In general, the results after revision surgery are worse in cases of instability than in cases of exchange surgery due to aseptic loosening or patellar abnormalities but better than in cases of infection or arthrofibrosis.
Article
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Aims: The outcome of total knee arthroplasty (TKA) is not always satisfactory. The purpose of this study was to identify satisfaction and biomechanical features characterising the gait of patients who had undergone TKA with either an anatomical single radius design or a medial pivot design. We hypothesised that the latter would provide superior function. Patients and methods: This is a study of a subset of patients recruited into a prospective randomised study of a single radius design versus a medial pivot design, with a minimum follow-up of one year. Outcome measurements included clinical scores (Knee Society Score (KSS) and Oxford Knee Score (OKS)) and gait analysis using an instrumented treadmill. Results: There was no statistically significant difference between the two groups for both the KSS and OKS. There was also no statistical significance in cadence, walking speed, stride length and stance time, peak stride, mid support and push-off forces. Conclusion: This study corroborates a previous study by the same authors that showed equally good results in clinical outcome and gait between the conventional single radius and medial pivot designs under stringent testing conditions. Cite this article: Bone Joint J 2018;(1 Supple A)100-B:76-82.
Article
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Background: Medial pivot (MP) type total knee arthroplasty (TKA) implants are designed with a highly congruent medial tibiofemoral articulation. Compared with the cam-and-post design of the posterior-stabilized (PS) TKA, the MP-TKA design has been hypothesized to better replicate the natural kinematics of the knee. We compared the MP-TKA and PS-TKA designs, with our primary outcome measures being range of motion (ROM) and patient-reported satisfaction. Methods: This study was a retrospective comparison between the 2 groups (76 MP-TKA vs 88 PS-TKA). ROM was collected preoperatively, 6 weeks, 6 months, and 1 year postoperatively. The Forgotten Joint Score-12 (FJS-12) scores were collected at a minimum of 1 year postoperatively. Results: There was no statistically significant difference in age, gender, or body mass index between the groups. We found a statistical difference in preoperative ROM (MP = 120.3°, PS = 112.8°, P = .002). There was no difference in ΔROM at 6 weeks (MP = -12.36, PS = -3.79, P = .066), 6 months (MP = -4.23, PS = 2.73, P = .182), or 1 year (MP = .17, PS = 3.31, P = .499). Patients who underwent the MP-TKA scored significantly better than the PS-TKA on the FJS-12 score (MP = 59.72, PS = 44.77, P = .007). Conclusion: We found that patients who underwent the MP-TKA scored better on the FJS than those who underwent the PS-TKA; particularly with regard to deep knee flexion and stability of the prosthesis. The MP-TKA design may offer improved patient outcomes because of its highly congruent medial tibiofemoral articulation.
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Objectives: This systematic review and meta-analysis was conducted to determine the mid-to long-term clinical outcomes for a medial-pivot total knee replacement (TKR) system. The objectives were to synthesise available survivorship, Knee Society Scores (KSS), and reasons for revision for this system. Methods: A systematic search was conducted of two online databases to identify sources of survivorship, KSS, and reasons for revision. Survivorship results were compared with values in the National Joint Registry of England, Wales, and Northern Ireland (NJR). Results: A total of eight studies that included data for 1146 TKRs performed in six countries satisfied the inclusion/exclusion criteria. Pooled component survivorship estimates were 99.2% (95% CI, 97.7 to 99.7) and 97.6% (95% CI, 95.8 to 98.6) at five and eight years, respectively. Survivorship was similar or better when compared with rates reported for all cemented TKRs combined in the NJR and was significantly better than some insert types at mid-term intervals. The weighted mean post-operative KSS was 87.9 (73.2 to 94.2), in the excellent range. Similar cumulative revision rates and KSS were reported at centres in the United States, Europe, and Asia. Conclusions: The subject system was associated with survivorship and KSS similar or better than that reported for other TKR systems.
Article
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Purpose The ADVANCE® Medial Pivot Knee System was designed with a highly congruent medial compartment and a less conforming lateral compartment to more closely mimic the kinematics of the normal knee. The purpose of this study was to evaluate the midterm clinical and radiographic outcomes of this total knee arthroplasty (TKA) system. Methods Between January 1998 and December 2006, 421 primary TKAs were performed in 373 subjects using this system and a surgical technique that resects the posterior cruciate ligament. Of these, 365 TKAs in 320 subjects were available for a follow-up visit occurring at a mean of 5.3 years. Subjects were evaluated using Knee Society Scores, range of motion, and radiographic review. Results The average Knee Society clinical score was 95.5 at final follow-up, with 358 (98 %) TKAs having excellent or good results. Range of motion increased from a preoperative mean of 115 to 119° at final follow-up. Component survivorship, excluding revisions for infection or trauma, was 96.6 % at five years. Conclusions This study demonstrates subjects implanted with the ADVANCE® Medial Pivot Knee System achieved satisfactory clinical and radiographic midterm outcomes.
Article
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A knee design with a ball-and-socket articulation of the medial compartment has a femoral rollback profile similar to the native knee. Compared to a conventional, posterior-stabilized knee design, it provides AP stability throughout the entire ROM. However, it is unclear whether this design difference translates to clinical and functional improvement. We asked whether the medially conforming ball-and-socket design differences would be associated with (1) improved ROM; and (2) improved American Knee Society, WOMAC, Oxford Knee, SF-36, and Total Knee Function Questionnaire scores compared to a conventional, fixed-bearing posterior-stabilized TKA. We enrolled 82 patients in a single-center, single-blinded, randomized, controlled trial comparing the medially conforming ball-and-socket design knee prosthesis to a posterior-stabilized total knee prosthesis. Our primary end point was ROM. Our secondary end points were American Knee Society, WOMAC, Oxford Knee, SF-36, and Total Knee Function Questionnaire scores. All patients were followed at 1 and 2 years. The mean ROM was 100.1° and 114.9° in the posterior-stabilized and medially conforming ball-and-socket groups, respectively. The physical component scores of SF-36 and Total Knee Function Questionnaire were better in the medially conforming ball-and-socket group. We found no difference in American Knee Society, WOMAC, and Oxford Knee scores. Both implant designs similarly relieved pain and improved function. The medially conforming ball-and-socket articulation provided better high-end function as reflected by the Total Knee Function Questionnaire. Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
Article
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Unlabelled: Despite substantial advances in primary TKA, numerous studies using historic TKA implants suggest only 82% to 89% of primary TKA patients are satisfied. We reexamined this issue to determine if contemporary TKA implants might be associated with improved patient satisfaction. We performed a cross-sectional study of patient satisfaction after 1703 primary TKAs performed in the province of Ontario. Our data confirmed that approximately one in five (19%) primary TKA patients were not satisfied with the outcome. Satisfaction with pain relief varied from 72-86% and with function from 70-84% for specific activities of daily living. The strongest predictors of patient dissatisfaction after primary TKA were expectations not met (10.7x greater risk), a low 1-year WOMAC (2.5x greater risk), preoperative pain at rest (2.4x greater risk) and a postoperative complication requiring hospital readmission (1.9x greater risk). Level of evidence: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
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The Swedish Knee Arthroplasty Registry (SKAR) has recorded knee arthroplasties prospectively in Sweden since 1975. The only outcome measure available to date has been revision status. While questionnaires on health outcome may function as more comprehensive endpoints, it is unclear which are the most appropriate. We tested various outcome questionnaires in order to determine which is the best for patients who have had knee arthroplasty as applied in a cross-sectional, discriminative, postal survey. Four general health questionnaires (NHP, SF-12, SF-36 and SIP) and three disease/site-specific questionnaires (Lequesne, Oxford-12, and WOMAC) were tested on 3600 patients randomly selected from the SKAR. Differences were found between questionnaires in response rate, time required for completion, the need for assistance, the efficiency of completion, the validity of the content and the reliability. The mean overall ranks for each questionnaire were generated. The SF-12 ranked the best for the general health, and the Oxford-12 for the disease/site-specific questionnaires. These two questionnaires could therefore be recommended as the most appropriate for use with a large knee arthroplasty database in a cross-sectional population.
Article
Aims Between 15% and 20% of patients remain dissatisfied following total knee arthroplasty (TKA). The SAIPH knee system (MatOrtho, Surrey, United Kingdom) is a medial ball and socket TKA that has been designed to replicate native knee kinematics in order to maximize the range of movement, stability, and function. This system is being progressively introduced in a stepwise fashion, with this study reporting the mid-term clinical and radiological outcomes. Patients and Methods A retrospective review was undertaken of the first 100 consecutive patients with five-year follow-up following SAIPH TKA performed by the senior authors. The data that were collected included the demographics of the patients, clinical findings, the rate of intraoperative ligamentous release, patient-reported outcome measures (PROMS), radiological assessment, complications, and all-cause revision. Revision data were cross-checked with a national registry. Results A total of 100 TKAs in 92 patients were included. Three patients died (three TKAs) and a further two TKAs were revised. Of the remaining 95 TKAs, five-year follow-up data were available for 81 TKAs (85%) in 87 patients. There were significant improvements in all PROMs and high satisfaction. The mean ROM at final follow-up was from 0° (full extension) to 124° flexion. There were seven major complications (7%): one infection, two deep vein thromboses, one cerebrovascular event, and two patients with stiffness requiring a manipulation under anaesthesia. Two patients required a lateral retinacular release to optimize patellar tracking in valgus knees; no additional ligament releases were performed in any patient. Radiological analysis demonstrated no evidence of implant-related complications. Conclusion These results demonstrate satisfactory clinical and radiological outcomes at five years following a medial ball and socket TKA. The complication and revision rates are consistent with those previously reported for patients undergoing TKA. These results demonstrate the safety and efficacy of the SAIPH Knee TKA system and support its wider use.
Article
Background: The WOMAC score is a validated outcome measure for use in patients undergoing TKA. Defining meaningful changes in the WOMAC score is important for sample-size calculations in clinical research and for interpreting published studies. However, inconsistencies among published studies regarding key definitions for changes in the WOMAC score after TKA potentially could result in incorrectly powered studies and the misinterpretation of clinical research results. Questions/purposes: (1) To identify the minimum clinically important difference (MCID) for the total WOMAC score and its components 1 year after TKA using an anchor-based methodology. (2) To define the minimum important change (MIC) and the minimum detectable change with 95% confidence (MDC95) for the total WOMAC score and its components 1 year after TKA. Methods: Between 2003 and 2013, 3641 patients underwent primary TKA at one center. Of those, 460 patients (13%) were excluded from this retrospective study for prespecified reasons (mainly secondary OA and bilateral surgery), and 592 patients (16%) were either lost to followup or could not be included because of incomplete questionnaires. WOMAC scores were recorded preoperatively and at 1 year postoperatively. Patient demographics and preoperative Short Form-12 and WOMAC scores were no different for the 16% of patients who were lost to followup or failed to complete 1-year questionnaires and the study cohort (n = 2589). At 1 year, patients were asked "How much did the knee replacement surgery improve the quality of your life?" Their responses were recorded as: a great improvement, moderate improvement, little improvement, no improvement at all, or the quality of my life is worse. The MCID was defined as the difference in the mean change in the WOMAC score between patients with no improvement compared with those with little improvement according to the anchor question. The MIC was defined as the change in the WOMAC score relative to the baseline score for patients who reported a little improvement in their quality of life. The MDC is the smallest change for an individual who is likely to be beyond the measurement error of the scoring tool and represents true change rather than variability in the scoring measure; we report it with 95% confidence bounds defining real change rather than variability in the scoring measure (MDC95). We calculated this with distribution-based methods for the whole cohort. Patients recording a little improvement (n = 211) and no improvement (n = 115) were used as anchor responses to calculate the MCID (using regression analysis to adjust for potential confounding variables such as age, gender, BMI and preoperative Short Form-12 or WOMAC scores) and the MIC (using receiver operative characteristics curves). Results: After adjusting for confounding variables such as age, gender, BMI as well as preoperative Short Form-12 and WOMAC scores, the MCID was 11 for pain, 9 for function, 8 for stiffness and 10 for the total WOMAC score. The MIC was 21 for pain, 16 for function, 13 for stiffness and 17 for the total WOMAC score. The MDC95 was 23 for pain, 11 for function, 27 for stiffness and 12 for the total WOMAC score. Conclusions: The MCID and MIC for the WOMAC score represent the smallest meaningful effect sizes when comparing the outcome of two groups (difference in mean change between the groups) or when assessing a cohort (a change in score for the group) after TKA, respectively, helping the reader to distinguish between a clinically important effect size and a mere statistical difference. We determined that the error in measurement (based on the MDC95) for the function component and total WOMAC scores were less than the MIC, which suggests changes beyond the MIC are clinically real and not due to uncertainty in the score. These parameters are essential to interpret TKA outcomes research and to ensure clinical research studies are amply powered to detect meaningful differences. Future studies using the WOMAC score to assess TKA outcomes should report not only the statistical significance (a p value) but also the clinical importance using the reported MCID and MIC values. Level of evidence: Level III, diagnostic study.
Article
Objectives: This systematic review and meta-analysis was conducted to determine the mid- to long-term clinical outcomes for a medial-pivot total knee replacement (TKR) system. The objectives were to synthesise available survivorship, Knee Society Scores (KSS), and reasons for revision for this system. Methods: A systematic search was conducted of two online databases to identify sources of survivorship, KSS, and reasons for revision. Survivorship results were compared with values in the National Joint Registry of England, Wales, and Northern Ireland (NJR). Results: A total of eight studies that included data for 1146 TKRs performed in six countries satisfied the inclusion/exclusion criteria. Pooled component survivorship estimates were 99.2% (95% CI, 97.7 to 99.7) and 97.6% (95% CI, 95.8 to 98.6) at five and eight years, respectively. Survivorship was similar or better when compared with rates reported for all cemented TKRs combined in the NJR and was significantly better than some insert types at mid-term intervals. The weighted mean post-operative KSS was 87.9 (73.2 to 94.2), in the excellent range. Similar cumulative revision rates and KSS were reported at centres in the United States, Europe, and Asia. Conclusions: The subject system was associated with survivorship and KSS similar or better than that reported for other TKR systems.
Article
Background: Despite the theoretical advantage of a knee design that can more reliably replicate the medial pivot (MP) of the natural knee, only a few clinical studies have compared the clinical results between the MP prosthesis and another design of prosthesis. We compared the midterm results of total knee arthroplasty (TKA) using an MP prosthesis vs a posterior-stabilized prosthesis via a matched-pair analysis; we included results related to patellofemoral joint symptoms. Methods: The midterm clinical and radiographic results of 125 consecutive patients (150 knees) who underwent a TKA with the ADVANCE MP prosthesis were compared with those of a control group who had undergone a primary TKA with a posterior-stabilized prosthesis. Results: Values of the Knee Society's Knee Scoring System, Western Ontario and McMaster Universities Osteoarthritis Index, and Kujala and Feller scoring systems, as well as the range of motion after TKA, did not significantly differ between the 2 groups. No differences in femorotibial angle and component position, including the patella component, were observed between the 2 groups. No significant differences in the change of patella tilt angle and the postoperative patellar translation were observed between the 2 groups. Conclusion: Patients with the MP prosthesis experienced satisfactory pain relief and a functional recovery, providing results similar to those of the posterior-stabilized prosthesis, including the resolution of patellofemoral joint symptoms.
Article
Postoperative stiffness is a relatively uncommon issue in total knee arthroplasty (TKA). However, it can be a debilitating complication when it occurs. Manipulation under anesthesia (MUA) is commonly used as the primary treatment modality following failed physiotherapy. The Advance medial pivot knee (Wright Medical Technology) was created in an effort to prevent stiffness postoperatively and increase range of motion. The Evolution medial pivot knee is a second-generation design that builds on the technology of the Advance knee. This article presents a retrospective review of prospectively collected data on 881 primary medial pivot knees (592 Advance knees, 289 Evolution knees). It was theorized that the design changes made to the Evolution knees might contribute toward reducing the need for MUA. It was found that the Evolution knees required significantly fewer manipulations under anesthesia (p = .036). The design modifications made to the Evolution knees may have contributed to the lower rate of MUA.
Article
Although good overall results have been reported with TKA, certain problems and limitations remain, primarily due to postoperative differences in joint kinematics, when compared with the normal knee. ADVANCE® Medial-Pivot TKA involves replicating the medial pivoting behavior observed in normal knees. Here, we aimed to investigate the clinical and radiological results and complications of TKA using this implant, at mid-term follow-up. From January 2001 to March 2012, we retrospectively selected 76 patients (85 knees; mean age at operation, 70.2±8.1years; range, 51-88years) with a mean follow-up period of 93.1±14.3months (range, 72-132months). Indications for TKA included primary degenerative osteoarthritis (60 knees), rheumatoid arthritis (22 knees), osteonecrosis (two knees), and osteoarthritis following high tibial osteotomy (one knee). The clinical and radiographic results were evaluated. Kaplan-Meier survivorship analysis indicated a success rate of 98.3% (95% confidence interval, 96.6-99.9%). Comparison of pre- and postoperative knee extension angles and ranges of motion showed significant improvement postoperatively, in both the Knee Society Scores (KSS) and Knee Society Functional Scores (KSFS) (p<0.05). In one case, radiographic assessment indicated implant loosening due to infection; however, despite this complication, significant improvement of postoperative varus or valgus deformity angles were noted in all cases (p<0.05). Patients undergoing ADVANCE® Medial-Pivot TKA achieved excellent clinical and radiographic results without any implant-related failures at mid-term follow-up. Level of evidence: Level IV.
Article
Substantial postoperative stiffness requiring manipulation is a well-recognized complication of total knee replacement. This study sought to determine whether the Medial-Pivot (MP) knee (Wright Medical, Memphis, TN) or the Double-High (DH) knee (Wright Medical) is more often associated with manipulation under anesthesia (MUA) for post-total knee arthroplasty (TKA) knee stiffness. It was hypothesized that manipulation rates would be similar. Retrospective review of 755 TKA patients showed that 4.1% required MUA, which is comparable to the literature. Manipulation by MUA for DH and MP knees was generally successful, with an average overall improvement in knee flexion of nearly 30°. MP and DH knees appear to have a lower than average prevalence of post-TKA knee stiffness requiring manipulation when compared with the literature. The number of MP and DH knees requiring MUA did not appear to differ substantially.
Article
There is conflicting evidence about the merits of mobile bearings in total knee replacement, partly because most randomised controlled trials (RCTs) have not been adequately powered. We report the results of a multicentre RCT of mobile versus fixed bearings. This was part of the knee arthroplasty trial (KAT), where 539 patients were randomly allocated to mobile or fixed bearings and analysed on an intention-to-treat basis. The primary outcome measure was the Oxford Knee Score (OKS) plus secondary measures including Short Form-12, EuroQol EQ-5D, costs, cost-effectiveness and need for further surgery. There was no significant difference between the groups pre-operatively: mean OKS was 17.18 (sd 7.60) in the mobile-bearing group and 16.49 (sd 7.40) in the fixed-bearing group. At five years mean OKS was 33.19 (sd 16.68) and 33.65 (sd 9.68), respectively. There was no significant difference between trial groups in OKS at five years (-1.12 (95% confidence interval -2.77 to 0.52) or any of the other outcome measures. Furthermore, there was no significant difference in the proportion of patients with knee-related re-operations or in total costs. In this appropriately powered RCT, over the first five years after total knee replacement functional outcomes, re-operation rates and healthcare costs appear to be the same irrespective of whether a mobile or fixed bearing is used. Cite this article: Bone Joint J 2013;95-B:486–92.
Article
The Oxford knee score (OKS) is a validated and widely accepted disease-specific patient-reported outcome measure, but there is limited evidence regarding any long-term trends in the score. We reviewed 5600 individual OKS questionnaires (1547 patients) from a prospectively-collected knee replacement database, to determine the trends in OKS over a ten-year period following total knee replacement. The mean OKS pre-operatively was 19.5 (95% confidence interval (CI) 18.8 to 20.2). The maximum post-operative OKS was observed at two years (mean score 34.4 (95% CI 33.7 to 35.2)), following which a gradual but significant decline was observed through to the ten-year assessment (mean score 30.1 (95% CI 29.1 to 31.1)) (p < 0.001). A similar trend was observed for most of the individual OKS components (p < 0.001). Kneeling ability initially improved in the first year but was then followed by rapid deterioration (p < 0.001). Pain severity exhibited the greatest improvement, although residual pain was reported in over two-thirds of patients post-operatively, and peak improvement in the night pain component did not occur until year four. Post-operative OKS was lower for women (p < 0.001), those aged < 60 years (p < 0.003) and those with a body mass index > 35 kg/m ² (p < 0.014), although similar changes in scores were observed. This information may assist surgeons in advising patients of their expected outcomes, as well as providing a comparative benchmark for evaluating longer-term outcomes following knee replacement. Cite this article: Bone Joint J 2013;95-B:45–51.
Article
Four-hundred forty patients underwent staged bilateral total knee arthroplasty using a different prosthesis on each side. Prostheses used were anterior-posterior cruciate-retaining (ACL-PCL), posterior cruciate-retaining (PCL), Medial Pivot (MP), posterior cruciate-substituting (PS), and mobile bearing (MB). At the 2-year evaluation, we asked "Which is your better knee overall?" Responses were as follows: 89.1% preferred the ACL-PCL to the PS and 76.2% preferred the MP to the PS. The ACL-PCL and the MP were preferred equally. The MP was preferred over the PCL by 76.0%, and 61.4% preferred the MP over the MB. The PS and PCL were preferred equally. Range of motion, pain relief, alignment, and stability did not vary significantly by prosthesis used. Patients with bilateral total knee arthroplasties preferred retention of both cruciates with use of the ACL-PCL prosthesis or substituting with an MP prosthesis.
Article
We describe the survivorship of the Medial Rotation total knee replacement (TKR) at ten years in 228 cemented primary replacements implanted between October 1994 and October 2006, with their clinical and radiological outcome. This implant has a highly congruent medial compartment, with the femoral component represented by a portion of a sphere which articulates with a matched concave surface on the medial side of the tibial insert. There were 78 men (17 bilateral TKRs) and 111 women (22 bilateral TKRs) with a mean age of 67.9 years (28 to 90). All the patients were assessed clinically and radiologically using the American Knee Society scoring systems. The mean follow-up was for six years (1 to 13) with only two patients lost to follow-up and 34 dying during the period of study, one of whom had required revision for infection. There were 11 revisions performed in total, three for aseptic loosening, six for infection, one for a periprosthetic fracture and one for a painful but well-fixed replacement performed at another centre. With revision for any cause as the endpoint, the survival at ten years was 94.5% (95% CI 85.1 to 100), and with aseptic loosening as the endpoint 98.4% (95% CI 93 to 100). The mean American Knee Society score improved from 47.6 (0 to 88) to 72.2 (26 to 100) and for function from 45.1 (0 to 100) to 93.1 (45 to 100). Radiological review failed to detect migration in any of the surviving knees. The clinical and radiological results of the Medial Rotation TKR are satisfactory at ten years. The increased congruence of the medial compartment has not led to an increased rate of loosening and continued use can be supported.
Article
The Advance Medial Pivot Total Knee Arthroplasty (Wright Medical Technology, Arlington, Tennessee, USA) has been designed to reproduce modern ideas of knee kinematics. We report a prospective clinical outcome study of 284 arthroplasties in 225 consecutive patients with a mean follow-up of 6.7 years (range 4 to 9 years). For evaluation, both objective and subjective clinical rating systems and serial radiographs were used. At final follow-up, 10 (4.4%) patients (10 knees) only were lost from follow-up and four (1.8%) patients (five knees) had died for reasons unrelated to the surgery with their knees performing well. There was an 82% compliance in the intervals of follow-up evaluation. All patients showed a statistically significant improvement (p=0.01) in the Knee Society clinical rating system, WOMAC questionnaire, SF-12 questionnaire, and Oxford knee score. The majority of patients (92%) were able to perform age-appropriate activities with a mean knee flexion of 117 degrees (range 85 degrees to 135 degrees) at final follow-up. Survival analysis showed a cumulative success rate of 99.1% at 5 years. Two (0.7%) arthoplasties, in which patient selection and surgical errors were identified, were revised due to aseptic loosening, one due to infection and one due to a traumatic dislocation. This study demonstrates satisfactory mid-term clinical results for this knee design.
Article
Development or retention of abnormal gait patterns after total knee arthroplasty may be related to the predictable pattern of further deterioration of other lower extremity joints. The purpose of this study was to determine whether gait mechanics are abnormal after total knee arthroplasty by conducting a systematic review of the literature. Articles were identified by searching the following electronic databases: PubMed, Cinahl, Web of Science: 221 references were retrieved. The titles and abstracts were reviewed to identify studies that potentially met the inclusion criteria. These articles were retrieved for further assessment. Ten articles met the inclusion criteria and were included in the review. There was a lack of common variables across the studies. Studies indicated smaller peak knee flexion during weight acceptance and less knee flexion excursion in total knee arthroplasty subjects compared to controls. Knee angle at foot strike was generally similar in arthroplasty groups compared to controls. Maximum external knee flexion moment was generally lower in arthroplasty groups compared to controls. Conflicting results were found for other knee moments. Several other stance phase variables were reported by individual studies only. Peak knee flexion and knee flexion excursion during weight acceptance are smaller in the operated knee following total knee arthroplasty compared to healthy controls. There may also be a smaller peak knee flexion moment after arthroplasty compared to controls. Knee mechanics in the operated knee are not normal after total knee arthroplasty. Abnormal gait mechanics may predispose the individual to further joint degeneration, particularly in the nonoperated knee. Further research should focus on the effects of unilateral total knee arthroplasty on the nonoperated knee.
Article
The objective was to determine the clinically important difference (CID) from primary total hip replacement (THR) and total knee replacement (TKR) surgeries using the Western Ontario McMaster University (WOMAC) osteoarthritis index. WOMAC scores were collected at decision for and 1 year after surgery (n=2,709). Transition ratings (15-point scale) were obtained at 1 year for pain and function, as well as a global assessment of willingness to go through surgery again. A "good deal better" defined the positive CID. WOMAC change scores for transition ratings and willingness to go through surgery again were evaluated using receiver operating characteristic curves. Patient characteristics within transition rating categories were examined. For THR, the positive CIDs were 41 of 100 for pain and 34 of 100 for function. The negative CIDs were 35 and 33, respectively. For TKR, the positive CIDs were 36 for pain and 33 for function. The negative CIDs were 30 and 25, respectively. Change scores for willingness to go through surgery again validated CID values. Postoperative complications decreased the likelihood of a positive CID. Improvement that is "a good deal better" is an appropriate threshold for the THR/TKR positive CID. Attaining a positive CID is negatively related to postoperative complications.
Article
Contemporary posterior cruciate-retaining total knee designs have provided pain relief and improved knee function but have failed to reproduce the kinematics and stability of the normal nonarthritic knee. The Medial Pivot total knee design features a near constant radius of curvature of the femoral component. The tibial surface is highly congruent and asymmetric, permitting a medial pivot motion during knee flexion. The purpose of the current study was to analyze and compare the gait kinematics of the Sigma posterior cruciate-retaining total knee implant, the Advance Traditional posterior cruciate-retaining total knee implant, and the Advance Medial Pivot knee implant using fluoroscopic analysis. In vivo kinematics were determined for 15 clinically successful total knee arthroplasties. Five knee implants were evaluated from each group. The authors analyzed the kinematics of knee motion during the stance phase of gait for each patient. On average, subjects with the Medial Pivot knee implant had a medial pivot motion. Both posterior cruciateretaining designs had a paradoxical roll forward of the tibia on femur during knee flexion and had greater excursion of both condyles during knee flexion than the medial pivot design. Nine of 10 of the posterior cruciate-retaining designs had condylar lift-off averaging 1.7 mm whereas only one Medial Pivot knee implant had condylar lift-off measuring 1.1 mm.
Article
A summation analysis of more than 70 individual kinematic studies involving normal knees and 33 different designs of total knee arthroplasty (TKA) was done with the objective of analyzing implant design variables that affect knee kinematics. Eight hundred eleven knees (733 subjects) were analyzed either during the stance phase of gait or a deep knee bend maneuver while under fluoroscopic surveillance. Fluoroscopic videotapes then were downloaded onto a workstation computer and anteroposterior (AP) femorotibial translational patterns were determined using an automated three-dimensional model fitting technique. The highest magnitude of translation was found in the normal and ACL-retaining TKA groups. Paradoxical anterior femoral translation during deep flexion was most commonly observed in PCL-retaining TKA. Substantial variability in kinematic patterns was observed in all groups. The least variability during gait was observed in mobile-bearing TKA designs, whereas posterior-stabilized TKA designs (fixed or mobile-bearing) showed the least variability during a deep knee bend. A medial pivot kinematic pattern was observed in only 55% of knees during deep knee flexion. Kinematic patterns of fixed versus mobile-bearing designs were similar with the exception of mobile-bearing TKA during gait in which femorotibial contact remained relatively stationary with minimal AP femorotibial translation.
Article
Satisfaction with the outcome of total knee arthroplasty is highly variable, with a small but significant percentage of patients reporting dissatisfaction with the procedure. The purpose of this study was to determine which factors contribute to patient satisfaction with total knee replacement (TKR), and their relative importance. At a minimum of 1 year post unilateral primary TKR, 253 patients completed a self-administered, validated "Knee Function Questionnaire," which examined each patient's participation in a broad range of activities involving the knee, their level of satisfaction, and the extent to which TKR had fulfilled their expectations. The association between function, expectation and satisfaction was examined using univariate and multivariate logistic regression. Seventy-five percent of patients were either "satisfied" or "very satisfied" with their knee replacement, while 14% were "dissatisfied" or "very dissatisfied." Satisfaction correlated significantly (p < 0.001) with age less than 60, absence of residual symptoms, fulfillment of expectations, and absence of functional impairment. Satisfaction with TKR is primarily determined by patients' expectations, and not their absolute level of function. Real improvements in the outcome of TKA must address prevention of residual pain, stiffness and swelling, and each patient's preoperative concept of the likely outcome of these procedures.
Article
Many studies suggest patient factors influence TKA outcomes, but the reported data are controversial, due perhaps in part to using only postoperative scores rather than change in scores from pre- to postoperatively. We examined the effect of gender, age, diagnosis, and obesity on changes in pre- to postoperative outcome measures (Knee Society clinical rating, WOMAC, and SF-12) in a cohort of 843 consecutive knee arthroplasties in 728 patients who received the same implant (Genesis II, Smith & Nephew, Memphis, TN). Minimum followup was 5 years (mean, 9.5 years; range, 5-11 years). Kaplan Meier survivorship was 98% +/- 0.007 with any reoperation as an end point. Male and female patients had similar increases in postoperative scores. Diagnosis and obesity made no difference in postoperative increases. However, less improvement occurred in health-related quality-of-life outcomes scores with advancing age.
Article
The objective of this study was to investigate the hypothesis that the increased constraint of a medial rotational knee promotes earlier loosening of the prosthesis. All patients with a Freeman-Samuelson 1000 knee arthroplasty (medial pivot design), (group 1), or a Freeman-Samuelson Modular knee arthroplasty, (group 2), with a minimum follow-up of 2 years (mean follow-up 4 years) were identified from our unit's arthroplasty database, and matched as closely as possible for age, length of follow-up and pre-operative diagnosis. Standardised anteroposterior and lateral radiographs were analysed for component migration and radiolucent lines as recommended by the Knee Society. There were 48 knees in each group. There were no failures in group 2. There was one failure requiring revision of the tibial component in group 1. There was no significant difference in overall radiolucent line scores between the two groups (p=0.66, at 5 years). Progressive radiolucent lines were detected in similar numbers of patients in both groups (FS1000 8/48, FSM 7/48, p=0.84). Our early radiological survey suggests that the increased constraint of the medial pivot knee prosthesis does not result in an increased incidence of radiographic loosening.
Article
Although the design features of the Medial Pivot fixed-bearing prosthesis reportedly improve kinematics compared with TKAs using fixed-bearings, clinical improvements have not been reported. We asked whether the clinical and radiographic outcomes, ranges of motion of the knee, patient satisfaction, and complication rates would be better in knees with a Medial Pivot fixed-bearing prosthesis than in those with a PFC Sigma mobile-bearing prosthesis. We compared the results of 92 patients who had a Medial Pivot fixed-bearing prosthesis implanted in one knee and a PFC Sigma mobile-bearing prosthesis implanted in the other. There were 85 women and seven men with a mean age of 69.5 years (range, 55–81 years). The minimum followup was 2 years (mean, 2.6 years; range, 2–3 years). The patients were assessed clinically and radiographically using the rating systems of the Hospital for Special Surgery and the Knee Society at 3 months, 1 year, and annually thereafter. Contrary to expectations, we found worse early clinical outcomes, smaller ranges of knee motion, less patient satisfaction, and a higher complication rate for the Medial Pivot fixed-bearing prosthesis than for the PFC Sigma mobile-bearing prosthesis. Level of Evidence: Level I, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
The New Zealand Joint Registry Seventeen Year Report January 1999 to December 2015
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