Article

Survival analysis of joint replacements

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Abstract

Survival analysis is a powerful tool for analysing the results of total joint replacement, but it has major drawbacks when the failure rates are very low. We have reviewed 35 recent survival analyses of joint replacements to assess the magnitude of these problems and make recommendations as to how they may be avoided.

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... In a survival analysis of joint replacement it is assumed that such patients have the same outcome as those who continue to be reviewed. 1,2 Some of the patients lost to follow-up, however, may be dissatisfied with their treatment and stop attending clinics for this reason. [1][2][3][4][5] There is therefore probably a higher rate of failure in these patients than in those who continue to be followed up. ...
... 1,2 Some of the patients lost to follow-up, however, may be dissatisfied with their treatment and stop attending clinics for this reason. [1][2][3][4][5] There is therefore probably a higher rate of failure in these patients than in those who continue to be followed up. Consequently, survival analysis, as currently performed, provides an over-optimistic picture of results. ...
... In a recent review of survival analyses, the rate of loss to follow-up was quoted in only half of the papers reviewed and was approximately 5%. 2 In those which did not mention loss to follow-up, the rates were probably higher. The annual revision rate after joint replacement is approximately 1%. ...
Article
Survival analysis of joint replacement relies on the assumption that surgical procedures in patients lost to follow-up have the same chance of failing as those in patients who continue to be assessed. Our study questions that assumption. During the 16-year follow-up of 2268 patients who had received total hip replacements 142 (6%) were lost to follow-up. The cumulative loss at 15 years was 20%. At their last assessment, patients who subsequently failed to attend for follow-up had significantly worse pain, range of movement and opinion of their progress (p < 0.001) and significantly worse radiological features than a matched control group (p < 0.01). Patients lost to follow-up have a worse outcome than those who continue to be assessed. Consequently, a survival analysis that does not take into account such patients is likely to give falsely optimistic results. It is therefore essential that vigorous attempts are made to minimise loss to follow-up, and that the rate of such loss is quoted. The overall loss to follow-up disguises the magnitude of the problem, which is best quantified by a cumulative rate of follow-up. The reliability of a study can be assessed by a loss-to-follow-up quotient, calculated by the number of failures: the lower the quotient the more reliable the data. Ideally, the quotient should be less than 1.
... [3][4][5]8,[22][23][24] Failure of the patellar component tends to occur early, [25][26][27] whereas the femoral and tibial components present problems later. 13,15,19,21 Improvements have been made after careful evaluation of various designs over long periods, 3,9,28 but an analysis of the failure of individual components in modular systems would be helpful. The results of using prostheses which accommodate excision or substitution of the posterior cruciate ligament are available, 4,5,8,23,24 but little information has been published on the long-term outcome of systems with lower 7,9 or higher 1,2 conformity which retain the ligament. ...
... For survivorship analysis, the actuarial lifetable method, as described by Armitage, 34 was used with calculation of the numbers at risk and the survival rates at annual intervals. The 95% confi dence limits were calculated by the method of Rothman 35 as used by Murray et al. 28 ...
... 4,10,44 If these factors are constant in each series, life-table analysis and survivorship curves are useful in comparing different designs of prosthesis. 28,34,35 The correlation of survivorship with individual components enables the identifi cation of mechanisms of failure and allows selective improvement of components in a modular system. This led us to abandon metal-backed patellae in favour of a three-lug all-polyethylene component and to move from a fl at-on-fl at sagittal articulation to a more conforming design. ...
Article
A consecutive series of 235 total knee arthroplasties using the PFC system was followed prospectively for at least ten years in 186 patients. The operation was for osteoarthritis in 150 knees, for rheumatoid arthritis in 83, and for Paget’s disease and femoral osteonecrosis in one knee each. At the latest review 56 patients had died, fi ve were too ill to assess and three could not be traced. The PFC knee replacement utilised was a nonconforming posterior-cruciate-retaining prosthesis with a polyethylene insert which is fl at in the sagittal plane. The patella was resurfaced using a metal-backed component in 170 cases, but later in the series we used an all-polyethylene component in 22 knees; 43 patellae were not resurfaced. The survival without need for reoperation for any reason was 90% at ten years. Nineteen revisions were component-related due to failure of nine metal-backed patellae, nine polyethylene inserts, and one unresurfaced patella; two reoperations were for synovectomy (one for recurrent haemarthrosis and one for recurrent rheumatoid synovitis) and three were for metastatic joint infection. There were no revisions for aseptic loosening of femoral or tibial components, or the all-polyethylene patellar replacement. The PFC system provides good and predictable results in tricompartmental arthritis of the knee. Loosening appeared to be negligible, but there were wear-related problems in 8%. The change from a metal-backed patella and an increase in the contact area of the tibial insert should provide further improvement by minimising wear.
... Long-term outcome is usually meas ured as time to revision, using survival analysis. This too is liable to distortion which makes comparison of outcome difficult (Murray, Carr and Bulstrode 1993). Our aim was to reviewall the designsof THR available in the UK, and to assess how much is known about their clinical performance. ...
... Orthopaedic surgeons therefore see many prob lems and are keen to develop better implants. There is also considerable financial incentive for companies to modify implants or to introduce completely new designs every few years (Sarmiento 1991 ;Bulstrode et al 1993). This tenden cy is clearly shown by the fact that 50% of the available designs of implants have been introduced in the last five years. ...
... This evidence is weak; other factors, particularly surgeon-dependent ones, may be responsible for the good results (Malchau et al 1993). The only valid method of comparing implants and identifying other important vari ables, especially those which are surgeon-and technique related is to organise and perform randomised multicentre trials (Bulstrode et al 1993). ...
Article
To assist surgeons to select a total hip replacement (THR) we present comparative information on all such implants on the market in the UK. We identified 62 different primary THRs, manufactured by 19 companies; half had been introduced in the last five years, and only 30% have any results published in peer-reviewed journals. The prices range from 250 pounds to 2000 pounds, and the two cheapest implants have the longest reported follow-up. The number of THR implants available in the UK, and presumably the rest of the world, is rapidly increasing, but there is little or no scientific evidence that the newer, more expensive, implants are better than established designs. Some will undoubtedly be worse. We believe that this situation is unsatisfactory and make recommendations for improvement, in particular that preference be given to implants with good results in published peer-reviewed long-term clinical trials.
... In these analyses, reoperation or revision surgery due to any reason or due to some more specified reason are usually used as a failure or event variable. Although numerous survival analysis methods are available, the two most popular methods used to assess survival in TJA studies are the Kaplan-Meier (KM) method and Cox proportional hazards regression analysis [3]. The KM method is considered the gold standard for analyzing the survival of joint prostheses [4]. ...
... The issue of poor reporting quality of orthopedic studies was raised in 1993 when it was noted that results were reported without a proper presentation of methods. For example, life-table analysis was not used in one third of the studies, patients at risk were not presented and survival curves were not provided [3]. Based on the results of our review, it seems that poor reporting of the methodology used still exists among the recent TJA literature. ...
Article
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Background Survival analysis and effect of covariates on survival time is a central research interest. Cox proportional hazards regression remains as a gold standard in the survival analysis. The Cox model relies on the assumption of proportional hazards (PH) across different covariates. PH assumptions should be assessed and handled if violated. Our aim was to investigate the reporting of the Cox regression model details and testing of the PH assumption in survival analysis in total joint arthroplasty (TJA) studies. Methods We conducted a review in the PubMed database on 28th August 2019. A total of 1154 studies were identified. The abstracts of these studies were screened for words “cox and “hazard*” and if either was found the abstract was read. The abstract had to fulfill the following criteria to be included in the full-text phase: topic was knee or hip TJA surgery; survival analysis was used, and hazard ratio reported. If all the presented criteria were met, the full-text version of the article was then read. The full-text was included if Cox method was used to analyze TJA survival. After accessing the full-texts 318 articles were included in final analysis. Results The PH assumption was mentioned in 114 of the included studies (36%). KM analysis was used in 281 (88%) studies and the KM curves were presented graphically in 243 of these (87%). In 110 (45%) studies, the KM survival curves crossed in at least one of the presented figures. The most common way to test the PH assumption was to inspect the log-minus-log plots ( n = 59). The time-axis division method was the most used corrected model ( n = 30) in cox analysis. Of the 318 included studies only 63 (20%) met the following criteria: PH assumption mentioned, PH assumption tested, testing method of the PH assumption named, the result of the testing mentioned, and the Cox regression model corrected, if required. Conclusions Reporting and testing of the PH assumption and dealing with non-proportionality in hip and knee TJA studies was limited. More awareness and education regarding the assumptions behind the used statistical models among researchers, reviewers and editors are needed to improve the quality of TJA research. This could be achieved by better collaboration with methodologists and statisticians and introducing more specific reporting guidelines for TJA studies. Neglecting obvious non-proportionality undermines the overall research efforts since causes of non-proportionality, such as possible underlying pathomechanisms, are not considered and discussed.
... 4 Many designs are available today having excellent or good outcome at mid-term and long-term follow-up with a 90-99% survivorship. [5][6][7][8][9][10] The PFC-Sigma TKA(Depuy Johnson & Johnson) is extensively implanted worldwide. Although various studies worldwide have reported outcomes and survivorship analysis of the PFC-Sigma prosthesis [11][12][13] , there is no such reported study from this part of the country. ...
... Most series of TKAs report survivorship of 90-99% at 10 years. [5][6][7][8][9][10] The PFC-Sigma has a reported survivorship of 97% by Clayton et al. 13 after 5 years and 99.6% by Dalury et al. after a mean follow-up of 87 months. 12 Although this study is too short it shows similar survival rate after a mean followup of 2 years, during which there were no problems with polyethylene wear, osteolysis and loosening of the prosthesis. ...
... Hakulinen and Abeywickrama (1985) 2 introduced a package to survival analysis. Murray et al. (1993) 3 provided a survival analysis of joint replacements. Leggat et al. (1998) 4 presented the noncompliance in hemodialysis: predictors and survival analysis. ...
... Hakulinen and Abeywickrama (1985) 2 introduced a package to survival analysis. Murray et al. (1993) 3 provided a survival analysis of joint replacements. Leggat et al. (1998) 4 presented the noncompliance in hemodialysis: predictors and survival analysis. ...
Article
Full-text available
Introduction: This paper studies risk factors which can have effects on the survival time of lung cancer patients during the treatment. Methods: The Cox proportional-hazards model has been applied for investigating the association between the survival time of patients and the predictors such as age, gender, the weight of patients, meal, the ECOG, and Karnofsky scores. Results: In the study, we find that the ECOG score, the Karnofsky score evaluated by doctors and the gender are the top three factors that significantly affect the hazard rate. Also, we utilize the estimated model to predict survival probability for the patients. Conclusion: In this article, we intentionally present a complete and detailed guide on how to perform a R-based package in survival analysis step by step as well as how to interpret all output results.
... Results are presented in numbers and percentages for the qualitative variables and in mean ± standard deviation and range for the quantitative variables. The Kaplan-Meier method was used to estimate the survival of the prosthesis [15]. The endpoint of this survival was taken as removal or revision of the prosthesis. ...
... A number of limitations must be acknowledged with this work. Similar to much of the existing literature, this is a retrospective case series looking at relatively small patient numbers [2,[5][6][7][8][9][10][11][12][13]15]. To ensure greater than 5 years of follow-up, a number of patients who had received the implant more recently, or had died during the study period, were also excluded thus further limiting our patient numbers. ...
Article
Full-text available
Introduction There is a paucity of survival data reporting the medium to long-term outcome of the LINK® Endo-Model® rotational hinge total knee arthroplasty (ERH-TKA). Such information is essential when counselling patients and predictors of survival would help inform patients of their likely outcome. Materials and methods A series of patients, who received an ERH-TKA, with a minimum follow-up of 5 years, were retrospectively identified from an established arthroplasty database. Data were collected from paper and electronic patient records. This included patient demographics, indication for surgery, complication rates and revision status. Our primary outcome of interest was joint implant survival. Results One hundred patients underwent an ERH-TKA over an 11-year period. There were 66 females and 34 males, with a mean age of 73.8 years and 67.6 years, respectively. Indications were classified into primary (n = 41), aseptic revision (n = 47) and two-stage infective revision (n = 12). The median follow-up was 8.2 (range 5–12) years. One-year implant survival amongst the cohort was 99%, falling to 95% at 5 years. Overall, there were eight revisions during the follow-up period. Considering only cases of aseptic failure, survival was 97% at 5 years and all failures occurred amongst revision cases. Implant failure was greater following revision arthroplasty but this was not statistically significant (p = 0.97). Cox regression analysis identified male sex to be the only independent predictor of failure (hazard ratio 1.75, 95% CI 1.04–31.82, p = 0.04) after adjusting for confounding variables. Conclusions The ERH-TKA has a good medium- to long-term survival rate but male patients are nearly twice as likely to undergo revision, compared to females, and should be made aware of this preoperatively.
... Revision is relatively uncommon after modern TKRs and inaccuracies may arise from loss to follow-up and the small numbers involved. 2 In many studies, more patients are lost to follow-up than are revised, and therefore survival analysis may give a falsely optimistic assessment of the outcome. 3 The low rates of revision make it difficult to distinguish between different types of TKR. ...
... Endpoints which are more common than revision would be more valuable in survival analysis. 2 Many different factors can be assessed after joint replacement including pain, range of movement, walking and the radiological appearance. In a recent review of THR, pain was found to be the best single outcome measure, in that it had the highest correlation with patient satisfaction and subsequent revision, and could be used as an endpoint in survival analysis. ...
Article
The results of total knee replacement (TKR) are commonly assessed by survival analysis using revision as the endpoint. We have used the assessment of pain by a patient-based questionnaire as an alternative. In one hospital, 1429 TKRs were inserted by 66 surgeons between 1987 and 1993. The survival at seven years, with revision as the endpoint, was 97.5% (CI 94 to 100). There were no significant differences between the three different types of implant used, the AGC, the IB2 and the Nuffield Knee. When the endpoint was the development of moderate pain, the survival at seven years for the AGC knee was 72% and that for the IB2 was similar. Significantly more patients (p = 0.007) with the Nuffield Knee, however, had developed moderate pain. Using revision as the endpoint, it is difficult to discriminate between the various types of TKR, but this can be achieved using pain. In this investigation 30% of the patients reported moderate pain at some stage by seven years from operation.
... Life tables were produced with numbers of implants entering each year and yearly revisions and deaths, to give annual and cumulative survival rates (Table I). 13 Kaplan-Meier survival curves were then produced for both implants and patients ( Figure 1). ...
Article
Full-text available
Aims Despite multiple trials and case series on hip hemiarthroplasty designs, guidance is still lacking on which implant to use. One particularly deficient area is long-term outcomes. We present over 1,000 consecutive cemented Thompson’s hemiarthroplasties over a ten-year period, recording all accessible patient and implant outcomes. Methods Patient identifiers for a consecutive cohort treated between 1 January 2003 and 31 December 2011 were linked to radiographs, surgical notes, clinic letters, and mortality data from a national dataset. This allowed charting of their postoperative course, complications, readmissions, returns to theatre, revisions, and deaths. We also identified all postoperative attendances at the Emergency and Outpatient Departments, and recorded any subsequent skeletal injuries. Results In total, 1,312 Thompson’s hemiarthroplasties were analyzed (mean age at surgery 82.8 years); 125 complications were recorded, necessitating 82 returns to theatre. These included 14 patients undergoing aspiration or manipulation under anaesthesia, 68 reoperations (5.2%) for debridement and implant retention (n = 12), haematoma evacuation (n = 2), open reduction for dislocation (n = 1), fixation of periprosthetic fracture (n = 5), and 48 revised stems (3.7%), for infection (n = 13), dislocation (n = 12), aseptic loosening (n = 9), persistent pain (n = 6), periprosthetic fracture (n = 4), acetabular erosion (n = 3), and metastatic bone disease (n = 1). Their status at ten years is summarized as follows: 1,180 (89.9%) dead without revision, 34 (2.6%) dead having had revision, 84 (6.6%) alive with the stem unrevised, and 14 (1.1%) alive having had revision. Cumulative implant survivorship was 90.3% at ten years; patient survivorship was 7.4%. Conclusion The Thompson’s stem demonstrates very low rates of complications requiring reoperation and revision, up to ten years after the index procedure. Fewer than one in ten patients live for ten years after fracture. This study supports the use of a cemented Thompson’s implant as a cost-effective option for frail hip fracture patients. Cite this article: Bone Jt Open 2022;3(9):710–715.
... Details will be presented in Section "Data preprocessing". Also it is important that we need to specify the right-censoring types existing in the data, different types of right-censoring records sometimes could be the result of different risk factors hence have different underlying empirical distribution, therefore the type of right-censoring needs to be addressed during the analysis of survival data 23 . Therefore, the remaining right-censored data will be all of individual-B type from Fig. 2, as we assume that all the right-censored maintenance records are from the components that have been running from the installation date till now without any failures. ...
Article
Full-text available
In recent years there is a data surge of industrial and business data. This posses opportunities and challenges at the same time because the wealth of information is usually buried in complex and frequently disconnected data sets. Predictive maintenance utilizes such data for developing prognostic and diagnostic models that allow the optimization of the life cycle of machine components. In this paper, we address the modeling of the prognostics of machine components from mobile work equipment. Specifically, we are estimating survival curves and hazard rates using parametric and non-parametric models to characterize time dependent failure probabilities of machine components. As a result, we find the presence of different types of censoring masking the presence of different populations that can cause severe problems for statistical estimators and the interpretations of results. Furthermore, we show that the obtained hazard functions for different machine components are complex and versatile and are best modeled via non-parametric estimators. However, notable exceptions for individual machine components can be found amenable for a Generalized-gamma and Weibull model.
... Survivorship of the DFA was established using Kaplan-Meier curves with revision as the endpoint. 28 Survival was calculated for the entire cohort as well as for each category of surgical indication. All p-values for parametric data were calculated using independent-samples t-test or analysis of variance (ANOVA), and all nonparametric data were calculated using the Mann-Whitney U test. ...
Article
Full-text available
Aims Endoprosthetic reconstruction with a distal femoral arthroplasty (DFA) can be used to treat distal femoral bone loss from oncological and non-oncological causes. This study reports the short-term implant survivorship, complications, and risk factors for patients who underwent DFA for non-neoplastic indications. Methods We performed a retrospective review of 75 patients from a single institution who underwent DFA for non-neoplastic indications, including aseptic loosening or mechanical failure of a previous prosthesis (n = 25), periprosthetic joint infection (PJI) (n = 23), and native or periprosthetic distal femur fracture or nonunion (n = 27). Patients with less than 24 months’ follow-up were excluded. We collected patient demographic data, complications, and reoperations. Reoperation for implant failure was used to calculate implant survivorship. Results Overall one- and five-year implant survivorship was 87% and 76%, respectively. By indication for DFA, mechanical failure had one- and five-year implant survivorship of 92% and 68%, PJI of 91% and 72%, and distal femur fracture/nonunion of 78% and 70% (p = 0.618). A total of 37 patients (49%) experienced complications and 27 patients (36%) required one or more reoperation. PJI (n = 16, 21%), aseptic loosening (n = 9, 12%), and wound complications (n = 8, 11%) were the most common complications. Component revision (n = 10, 13.3%) and single-stage exchange for PJI (n = 9, 12.0 %) were the most common reoperations. Only younger age was significantly associated with increased complications (mean 67 years (SD 9.1)) with complication vs 71 years (SD 9.9) without complication; p = 0.048). Conclusion DFA is a viable option for distal femoral bone loss from a range of non-oncological causes, demonstrating acceptable short-term survivorship but with high overall complication rates. Cite this article: Bone Jt Open 2022;3(3):173–181.
... Kaplan-Meier methodology and a life table was used to investigate implant survival. 20,21 Log rank and Cox regression analysis were used to identify factors associated with implant survival. A p-value of ⩽0.05 determined statistical significance. ...
Article
Aims Primary aim was to determine survival of a cemented acetabular component with bulk roof autograft with a minimum of 12 years follow-up. The secondary aim was to determine the clinical outcome. Methods A cohort of 62 consecutive patients (74 hips) undergoing cemented total hip arthroplasty with acetabular bulk roof autograft for acetabular dysplasia were retrospectively identified. The group consisted of 57 female patients (67 hips) and 5 male patients (7 hips) with a mean age at operation of 45 years. No patient was lost to follow-up, however 9 patients died had during the study period. The Oxford Hip Score (OHS), Forgotten Joint Score (FJS), EuroQol 5-Dimensional Score (EQ-5D), Short Form (SF-12) physical score and patient satisfaction were used to assess clinical outcome for patients with a surviving prosthesis. Results The median follow-up was 16.6 (13.4–19.1) years. 6 revisions were performed during the follow-up period, all of which were due to aseptic loosening of the acetabular component. The all-cause Kaplan Meier survival rate for the acetabular component was 99% at 10 years, 95% at 15 years and 83% at 20 years. Neither age, gender, femoral osteotomy or polyethylene (UHMW vs. cross-linked) were significant predictors of aseptic revision of the acetabular component. There were no case of graft resorption and all grafts were radiologically incorporated. 45 patients were available for functional assessment at a mean follow-up of 18.2 years. The mean OHS was 37.8, FJS was 55.7, EQ5D was 0.73, and SF-12 physical component was 43.2. No patient was dissatisfied, with 2 patients reporting a neutral satisfaction, 7 stating they were satisfied and the remaining 36 were very satisfied. Conclusions A cemented acetabular component with bulk roof autograft for dysplasia offers excellent survival with good to excellent functional outcome with high patient satisfaction in the medium- to long-term.
... The data become unreliable when there are fewer than ten hips in the tail of the survival curve. 26 Moreover, the correlations between the AVN grade and OA grade at follow-up, between the AVN grade and HHS, and between AVN grade and WOMAC score were calculated. ...
Article
Full-text available
Purpose Late-diagnosed dislocated hips underwent open reduction, Dega osteotomy, and proximal femoral osteotomy between 1968 and 1988. The objectives of this study are to assess the survival of hips into adulthood, clinical and radiological outcome, patients’ life perspectives and the risk factors of failure. Methods An assessment of 67 hips treated when younger than five years (<age 5yr. group) and 71 hips in the group aged older than five years (+age 5yr.) was performed. All cases were evaluated clinically and radiographically, and survival was assessed, considering hip replacement as endpoints for failure (abbreviation HR+ refers to hips that underwent hip replacement surgery; HR- refers to hips that have not been replaced at the follow-up). The fertility rate and the social security disability benefits (SSDB) recipiency percentage were calculated. Results The 40-year survival rates were 73% (95% confidence (CI) 71% to 76%) in the <age 5yr. group, 54% (95% CI 51% to 57%) in the +age 5yr. group, 70% (95% CI 67% to 73%) in one-sided dislocations and 57% (95% CI 54% to 60%) in bilateral dislocations. At follow-up, the median Harris hip and Western Ontario and McMaster Universities Osteoarthritis scores were 90.0 and 13.0 (<age 5yr. group, HR-), 74.0 and 28.0 (+age 5yr. group, HR-), 90.0 and 16.0 (<age 5yr. group, HR+) and 84.5 and 11.5 (+age 5yr. group, HR+), respectively. The operation normalized the radiological parameters. The correlation between the grade of femoral head avascular necrosis (AVN) at a median 2.6 years after the operation and the grade of osteoarthritis at follow-up was 0.38 (p < 0.001). The fertility rate was 1.54. In total, 16.0% (aged under five years) and 38.5% (aged over five years) of patients were receiving SSDB (p = 0.003). Conclusion Early failure risk factors are older age at the surgical procedure, high AVN grade and bilateral hip involvement. Still, the results facilitate hip reposition whenever technically manageable, even in teenagers. Level of evidence III
... The accrual of patients over the course of a study masks both the magnitude and temporal characteristics of variables of interest since standard statistical measures based upon the whole group contain time-related biases. Lifetable (actuarial) or Kaplan-Meier methods can be used to accommodate these effects but even here serious errors can be generated under certain conditions [1][2][3][4]. Regarding cochlear implant revision surgery, published papers contain information on both overall incidence rates and surgical details but time relevant information is, in the main, limited. Although efforts have been made to improve reporting standards, comparing results from different studies and sources is difficult and considered by some to be an almost impossible task [5,6]. ...
Article
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The aim of this study was to determine the magnitude of the risks associated with cochlear implantation. Results from a pool of thirty clinical studies involving cochlear implantation in over 6300 children were obtained from an internet search. The relevant data were transformed to a common time base (patient time) to allow an evaluation of events following implantation. The main outcome measure was cumulative survival probability for all-cause revision surgery. Over 10 years this was estimated to be 0.71. Thus, at 10 years post-implantation close to 30% of children with unilateral implants will have undergone revision surgery. This figure is considerably greater than that commonly reported for overall revision rates and illustrates the importance of interpreting results with respect to the relevant time frame. When non and low-use is incorporated into the analysis the above figure rises to about 37% of children affected. The findings raise concerns about the information provided to both individuals and regulatory bodies regarding the risks associated with cochlear implantation. The consequences for bilateral implantation are apparent. Our recommendations are i) a full disclosure to parents and children of the true magnitude of the risks and ii) for a body with significant expertise in reliability and systems engineering, and no conflicts of interest, to play a major role in the regulatory management of this service.
... Kaplan-Meier (KM) survival analysis was performed to generate survivorship curves with 95 confidence intervals (CIs), with the endpoints of re-operations for any reason. Besides, a worst-case KM curve was also performed, where all patients lost to follow-up were considered as a failure [24]. A two-tailed paired t test was performed to evaluate the differences between pre-operative and post-operative (last follow-up) Knee Society score, ROM, WOMAC, and OKS. ...
Article
Purpose Total knee arthroplasty (TKA) is a cost-effective surgery with a survival rate higher than 90% after 15 years. Nevertheless, patients are unsatisfied in more than 15% of cases. Medial pivot (MP) prosthetic designs were introduced in late 90’s with the aim to reproduce natural knee kinematics. The purpose of this study is to evaluate the survivorship and clinical outcomes of a novel design of MP knee with a minimum follow-up of five years. Methods This is a retrospective review of all patients who underwent primary TKA using the K-Mod dynamic congruence implant (Gruppo Bioimpianti, Peschiera Borromeo, Milan, Italy) between 2012 and 2013 at a single institution. A total of 339 patients (351 knees) were included with a mean age of 74 years (range 41–89). The Knee Society score, the global range of movement, the Western Ontario and McMaster Universities Osteoarthritis score, Forgotten Joint score, and the short-term form 12 health survey were collected. FJS and SF-12 were collected only post-operatively. Radiographic outcomes were evaluated according to the Knee Society’s roentgenographic evaluation system. Kaplan-Meyer (KM) curves were performed to evaluate implant survivorship. A two-tailed paired t test was performed to evaluate the differences between pre-operative and post-operative score. Results A total 297 patients (315 knees) were available for clinical and radiographic analysis, and the mean follow-up was 66.4 months. A total of 17 patients (17 knees 5.4%) experienced a post-operative complication, and a reoperation was performed in five patients (5 knees 1.6%). Four patients had a periprosthetic joint infection, and two patients had a post-traumatic periprosthetic femoral fracture. The KM survivorship at five years was 98.2% (95% CI 0.96 to 0.99) for revision for any reason. There was a statistically significant improvement (p < 0.05) in all the objective and subjective outcomes measured. Conclusion The K-Mod dynamic congruence design has shown an excellent clinical, radiographic, and patient-reported outcome in primary TKAs.
... From these diverse examples, it becomes clear that survival analysis can be applied to many problems in different fields. Specifically, survival analysis is utilized in biology, medicine, engineering, marketing, social sciences or behavioral sciences [1][2][3][4][5][6][7][8][9]. Due to the widespread usage of this method across different fields, there are several synonyms used. ...
Article
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The modeling of time to event data is an important topic with many applications in diverse areas. The collective of methods to analyze such data are called survival analysis, event history analysis or duration analysis. Survival analysis is widely applicable because the definition of an ’event’ can be manifold and examples include death, graduation, purchase or bankruptcy. Hence, application areas range from medicine and sociology to marketing and economics. In this paper, we review the theoretical basics of survival analysis including estimators for survival and hazard functions. We discuss the Cox Proportional Hazard Model in detail and also approaches for testing the proportional hazard (PH) assumption. Furthermore, we discuss stratified Cox models for cases when the PH assumption does not hold. Our discussion is complemented with a worked example using the statistical programming language R to enable the practical application of the methodology.
... The end point was defined as radiographic evidence of acetabular cup loosening. A separate survival analysis for the worst-case scenario was performed, which included the five patients (five knees) lost during follow-up or who died and which assumed all prosthesis failed in the year of their withdrawal [32]. The independent sample Student's t test was used to compare age, body mass index, follow-up period, position of the acetabular component, migration of the acetabular component and total wear. ...
Article
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Introduction Acetabular revision arthroplasty using jumbo cups for moderate-to-severe acetabular defects has varied outcomes. We evaluated the clinical and radiological outcomes of acetabular revision arthroplasty using a press-fitted jumbo cup and sought to identify factors that influence outcomes during intermediate follow-up. Materials and methods Eighty patients (47 men, 33 women; 80 hips) who underwent acetabular revision arthroplasty using press-fitted jumbo cups were included. The mean follow-up period was 10.4 years. Harris hip score (HHS), presence of groin pain, radiographic results, and Kaplan–Meier survival curves were evaluated. Implant design and surgery-related and patient-related factors were assessed to identify influential factors for cup loosening. Migration and wear analyses were performed using Einzel-Bild-Röntgen-Analyse software. Results The mean preoperative HHS of 53 had improved to 77 at the final follow-up (p = 0.005). Nine patients experienced groin pain. Acetabular cup loosening was observed in seven cups (8.7%), and one jumbo cup was replaced with a reinforcement cage. The survival rate of the acetabular cup was 91% at 16 years according to the Kaplan–Meier analysis. Osteolysis was identified around the cup in six cases (7.5%). Acetabular cup loosening occurred more frequently in patients with conventional polyethylene liners than in those with highly cross-linked polyethylene liners (p = 0.045). The mean total migration was 1.52 mm, and the mean total wear was 0.98 mm. There was a positive correlation between total migration and total wear (p = 0.023; Spearman’s rho = 0.388). The mean wear rate of the patients with the cup inclination angle < 50° was significantly lower than those with the cup inclination angle > 50° (p = 0.001). There were four cases of complications (three dislocations and one infection) that did not require revision surgery. Conclusion Press-fitted jumbo cups for acetabular revision arthroplasty exhibited encouraging results during follow-up for an average of 10 years. Use of highly cross-linked polyethylene liners and proper placement of the acetabular component with an inclination angle < 50° may contribute to better clinical outcomes after acetabular revision arthroplasty with jumbo cups.
... Total Knee Arthroplasty (TKA) has been proven to be a safe and reliable surgical procedure, relying on extensive literature on approaches [1,2], surgical techniques [3,4], physiotherapy [5] and clinical follow-up [6]. The improvements made to optimize the knee procedure were obtained with the help of statistical evidence [7,8]. ...
Article
Background: Bilateral cases, representing at least 25% of total knee arthroplasties (TKA), could convey a statistical bias linked to dependency. Registries allow exploring this issue, susceptible to question surgeon validated protocols. Do bilateral total knee arthroplasties behave differently than unilateral knees in terms of implant survival? Hypothesis: Bilateral TKA have a better survival than unilateral TKA. Patients and methods: A number of 14,652 bilateral and 27,440 unilateral TKAs were compared. Influencing factors were tested with hazard ratios applied on bilateral knees. Results: Bilateral knees had a better survival (p<0.001). Delay between first and second side surgeries had an influence on survival of the first knee: if below a year, the first knee survival was superior to the second knee; more than three years between both arthroplasties significantly decreased the survival of the first implant. If the first knee was revised, the hazard ratio for revision of the second implant was 3.5. Discussion: Series should include separate evaluations of bilateral cases, because they have a better survival than unilateral knees. A long delay between both knee replacements could impact both implant survivals. Level of Evidence III, Cohort Comparative Study.
... Dichotomous variables were assessed using Chi square test. Kaplan-Meier methodology [12] and a life table were used to investigate implant survival [13]. Patients reaching the end of their period of follow-up were censored and deaths were recorded as the primary endpoint. ...
Article
Background: The low contact stress (LCS) mobile-bearing total knee replacement (TKR) was designed to minimise polyethylene wear, aseptic loosening and osteolysis. However, registry data suggests there is a significantly greater revision rate associated. The primary aim of this study was to assess long-term survivorship of the LCS TKR performed at a single high-volume centre. Secondary aims were to assess survival by mechanism of failure and identify predictors of revision. Methods: During a 13-year period (1993-2006) 1091 LCS TKRs were performed by two senior surgeons. Thirty-three with incomplete data were excluded. The patients were retrospectively identified from an arthroplasty register. Mean age was 69 (range 30-96) years. Five hundred seventy-seven TKRs were performed in females, 481 in males. Mean follow-up was 14 years (SD 4.3). Results: There were 59 revisions during the study period: 14 (23.7%) for infection, 18 (30.5%) for instability, and 27 (45.8%) for polyethylene wear. Three hundred ninety-two patients died. All-cause survival at 10 years was 95% (95%CI 91.7-98.3) and at 15 years was 93% (95%CI 88.6-97.8). Survival at 10 years according to mechanism of failure was: infection 99% (95%CI 94-100%), instability 98% (95%CI 94-100%), and polyethylene wear 98% (95%CI 92-100). Of the 27 with polyethylene wear, only 19 (70.4%) had osteolysis requiring component revision, the other eight (29.6%) had polyethylene exchanges. Cox regression analysis identified younger age as the only predictor of revision (HR 0.96, 95%CI 0.94-0.99, p = 0.003), with a four percent decreased risk of revision for each increase in year of age. Conclusions: The LCS TKR demonstrates excellent long-term survivorship with a low rate of revision for osteolysis, however this risk is increased in younger patients.
... Dichotomous variables were assessed using a Chi-square test. Kaplan-Meier methodology and a life table were used to investigate survival [6,7]. Cox regression analysis was used to identify independent predictors of survival, entering all variables that were significant or demonstrated a trend towards on univariate analysis. ...
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Background: The primary aim of this study was to identify independent predictors of long-term survivorship after high tibial osteotomy (HTO). The secondary aims were to describe the functional outcome of surviving HTO 10-20 years after surgery. Methods: A retrospective cohort of 223 HTO that were performed for the treatment of medial osteoarthritis was identified. Details were recorded from the patient notes. All surviving patients were contacted and asked to complete a Tegner Activity Scale, Lysholm Knee Score and rate pain using the Visual Analogue Scale (VAS). Survival analysis was performed, using conversion to arthroplasty as the definition of failure. Results: The mean age was 54 years (24-80 years). There were 123 (55.2%) in males and 100 (44.8%) in females. The mean BMI was 27.2 (SD 3.9). Twenty (9%) patients were lost to follow-up. The mean follow-up was 12 (SD 4) years. Survival at 10 years was 75 and 55% at 15 years and less than 40% at 20 years. Cox regression analysis demonstrated age of 50 years or more, female gender and surgical technique to be significant independent predictors of failure. The median Tegner score was 3 (inter-quartile range (IQR) 1-3). The mean Lysholm score was 75.5 (SD 18.4). The median VAS was 5 (IQR 0-6). Conclusions: The medium- to long-term survival and functional outcome after HTO was good to excellent at 10-20 years of follow-up. Age, gender, surgeon and surgical technique were identified as independent predictors of failure.
... This is an improvement over the early results reported for hand packing and other early cementing techniques (Table VIII); we have confirmed recent reports of better femoral results with improved cementing techniques and more experience (Tables IX and X). [17][18][19][20][21][22][23][24][25][26] We have now abandoned the use of cement for revision surgery on the acetabulum, but continue to use it for femoral reconstruction, especially in older patients. ...
Article
We performed 83 consecutive cemented revision total hip arthroplasties in 77 patients between 1977 and 1983 using improved cementing techniques. One patient (two hips) was lost to follow-up. The remaining 76 patients (81 hips) had an average age at revision of 63.7 years (23 to 89). At the final follow-up 18 hips (22%) had had a reoperation, two (2.5%) for sepsis, three (4%) for dislocation and 13 (16%) for aseptic loosening. The incidence of rerevision for aseptic femoral loosening was 5.4% and for aseptic acetabular loosening 16%. These results confirm that cemented femoral revision is a durable option in revision hip surgery when improved cementing techniques are used, but that cemented acetabular revision is unsatisfactory.
... Survivorship analysis. Survivorship analysis was studied by a life table 18,19 with failure defined as a revision. For schematic representation, a time unit of four months was used. ...
Article
We performed 88 primary ball-and-socket arthroplasties of the trapeziometacarpal joint in 84 patients (69 women and 15 men) with a mean age of 61 years (37 to 81). Cemented de la Caffinière prostheses were implanted in 43 joints from 1988 to 1991 and 45 cementless Ledoux implants were used between 1992 and 1994. Of the 61 surviving prostheses still in situ, 51 were reviewed clinically and radiologically with a mean follow-up of 25 months for the Ledoux and 63 months for the de la Caffinière implant. The survival rate for the Ledoux prosthesis was 58.9% at 16 months and for the de la Caffinière implant 66.4% at 68 months. Loosening occurred in 15% of the Ledoux stems, in 46% of the Ledoux cups, in 24% of the de la Caffinière stems and in 28% of the de la Caffinière cups. Both prostheses behaved similarly, and it is clear that a constrained ball-and-socket prosthesis is not suitable for the trapeziometacarpal joint.
... Revisions have been generally used as the point of failure, and there is no agreement whether the presence of significant pain or loss to follow-up should be regarded as a failure. Murray, Carr and Bulstrode 19 suggested that the development of significant pain without radiological evidence of loosening should be classed as partial failure, and Scuderi and Insall 20 emphasised that cases lost to follow-up should also be considered as failures. Russotti and Harris 21 placed the cup proximally in the false acetabulum to avoid a thick cement mantle. ...
Article
We performed Charnley total hip arthroplasties on 64 patients (71 hips) between 1976 and 1984 for moderate congenital acetabular dysplasia in which a superolateral cement thickness of less than 20 mm was expected when the cup was placed in the true acetabulum at an angle of 45°. Of these, 59 hips were examined 10 to 17 years after operation; 37 (group A) had been operated on between 1976 and 1982 using Charnley’s original technique of cementing the acetabulum and 22 (group B) between 1983 and 1984 using more modern techniques. In group A, aseptic loosening of the socket was observed in ten hips (27.0%) and the 17-year survival rate was 81.5%. In group B, loosening was noted in only one socket (4.5%) and the 13-year survival rate was 100%. The improved techniques produced significantly better long-term results in fixation of the cup in dysplastic hips without bone grafting.
... We used the life-table method of survival analysis, 5,12 with endpoints defined by different levels of pain (Table VII). Survival curves were derived for each type of implant until the number of patients in the group fell below ten, 8 and confidence limits were calculated. ...
Article
We have assessed the relative value of various outcome measures after THR, by the analysis of follow-up data from over 2000 patients. They had been reviewed clinically and radiologically six months after operation, at one year, and then every two years, some for 16 years. At each review their pain level, stiffness and opinion of progress were scored and a radiograph taken. We found that pain level was the most informative outcome as a predictor of revision and correlated well with the patients’ opinions. We made a comparison between the six types of implant in the series, using survival analysis and log-rank testing with different pain levels as endpoints. This analysis revealed differences which were not detected by survival analysis using the traditional endpoint of revision. We therefore recommend the use of different levels of pain as the main outcome measures after total hip replacement.
... A survival analysis was constructed using a life table (Table I), with the effective number at risk and confidence intervals calculated. 4,5 Survivorship was defined as either not awaiting revision or having had a revision and with a MDP pain score of 5 or 6. ...
Article
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We describe the clinical and radiological outcome of 100 consecutive total hip replacements in 86 patients using the JRI Furlong hydroxyapatite-coated femoral component. The follow-up was 100% at a mean of ten years (9.0 to 12.0). All 54 living patients (62 hips) were examined annually. Their mean Merle d’Aubigné score was 5.8/5.6/4.6. A total of 32 patients had died. Their notes at the last annual assessment recorded a similar outcome to that of the living patients. Radiographs showed no radiolucent lines around any femoral component and there were no signs of impending failure. One patient required excision arthroplasty, but the femoral component had been bonded satisfactorily. There have been no other revisions of femoral components. Our findings suggest that the hydroxyapatite coating gives a satisfactory prosthesis-bone interface which is preferable to any other system.
... Statistical survivorship analysis was undertaken by the construction of life tables and calculation of annual cumulative rates. 9,10 The 95% confidence intervals were calculated according to the Wilson quadratic method. 11 Clinical results were graded according to the Merle d'Aubigné scoring system 12 as modified by Charnley. ...
Article
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Although about 200 000 cementless Zweymüller-Alloclassic total hip arthroplasties (THAs) were carried out worldwide in the last decade, the survival analysis of these prostheses was not available in the 2000 report of the Swedish national hip arthroplasty registry. We report a prospective survivorship analysis of 200 consecutive grit-blasted cementless Alloclassic primary THAs carried out since 1988. Using surgical, clinical and radiological endpoints for the stem and the threaded cup the ten-year survivorship was 91.5% for reoperation for any cause, 96.4% for hip pain (Merle d’Aubigné score < 5 points, clinical failure), 99.4% for definite aseptic loosening (radiological failure) and 99.3% for revision for aseptic loosening. Using the Swedish registry criteria of primary osteoarthritis and revision for aseptic loosening as the endpoint, the survival rate of 99.1% at ten years for the subgroup of 157 Alloclassic THAs in osteoarthritis compares favourably with that of the best modern cemented hip replacements reported in the Swedish arthroplasty registry.
... The endpoints include: failure defined as reoperation for any reason, including aseptic loosening, recurrent dislocation, infection, periprosthetic fracture, excision of ectopic bone or cement (Fig. 5); revision for aseptic loosening of the stem (Fig. 6); revision for aseptic loosening of the cup (Fig. 7); pain grading of t3 (Fig. 8); 25 and localised endosteal femoral lysis (Fig. 9) since this is held to be a poor prognostic feature in cemented hip arthroplasty. 26 Since the fate of every implant is known, the lost-to-follow-up quotient is 0 and a survivorship based on the 'worst-case scenario' 27 would be the same as that shown in Figure 5. Confidence limits were calculated for the survivorship curves in Figures 5 and 8 using the Peto equation, 9,28 and for those in Figures 6, 7 and 9, the Years since operation Survivorship (%) 4 to 5 3 to 4 2 to 3 1 to 2 0 to 1 ure was low. Since the patients in this series remain under regular review and their current status is known, all the survivorship curves, except those with the endpoints of localised osteolysis and a pain grading of t3, extend to 10 to 12 years. ...
Article
We describe our experience with the implantation of 325 Exeter Universal hips. The fate of every implant was known. The procedures were undertaken by surgeons of widely differing experience. At follow-up at 12 years, survivorship with revision of the femoral component for aseptic loosening as the endpoint was 100% (95% CI 98 to 100). Survivorship with revision of the acetabular component for aseptic loosening as the endpoint was 96.86% (95% CI 93.1 to 98.9) and that with any reoperation as the endpoint 91.74% (95% CI 87.7 to 95.8). No adverse features have emerged as a consequence of the modular connection between the head and neck of the implant.
... Although such methods allow for different lengths of follow-up, they are sensitive to the choice of endpoint and patients lost to follow-up are considered to have the same rate of failure as those who complete the trial. 10 The risk ratios were calculated using Cox's regression analysis. The risk ratio of a variable is expressed after adjusting for the effect of other explanatory variables in the model. ...
Article
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A total of 10474 unicompartmental knee arthroplasties was performed for medial osteoarthritis in Sweden between 1986 and 1995. We sought to establish whether the number of operations performed in an orthopaedic unit affected the incidence of revision. Three different implants were analysed: one with a high revision rate, known to have unfavourable mechanical and design properties; a prosthesis which is technically demanding with a known increased rate of revision; and the most commonly used unicompartmental device. Most of the units performed relatively few unicompartmental knee arthroplasties per year and there was an association between the mean number carried out and the risk of later revision. The effect of the mean number of operations per year on the risk of revision varied. The technically demanding implant was most affected, that most commonly used less so, and the outcome of the unfavourable design was not influenced by the number of operations performed. For unicompartmental arthroplasty, the long-term results are related to the number performed by the unit, probably expressing the standards of management in selecting the patients and performing the operation.
Article
Moisture induced stress tester (MIST) has been recently developed which aims to simulate stripping due to repeated pore pressure generation. In the current work, asphalt mixes containing recycled asphalt pavement (RAP) (in proportion of 0, 10, 20, 30 and 40% by weight) were subjected to varying stress cycles of MIST (0, 1000, 2000, 3500, 5000, 10,000 cycles) and indirect tensile (IDT) strength test was conducted on such mixes. AC30 was used for control mix whereas AC10 was adopted for RAP mixes. The results of IDT strength tests assisted in computing the failure times and such times were analysed using survival analysis based on Kaplan Meier (KM) estimator and Cox Proportional Hazards (CPH) model. The results indicated that survival analysis can be effectively utilised to analyse the IDT strength test results. It was observed that increasing stress cycles of MIST increase the time to failure whereas RAP is expected to reduce the time to failure. Moreover, KM estimator indicated that RAP reduces the survival of asphalt mixes. Hazard ratio (HR^) computed using CPH model shows a decrease with the increase in RAP proportion. Both MIST tensile strength ratio (M−TSR) and HR^ revealed that RAP leads to an improvement in moisture damage resistivity of asphalt mixes. Hence, HR^ has the potential to be an effective indicator of moisture damage susceptibility of asphalt mixes. Also, “Good” and negative correlation was observed to exist between M−TSR and HR^. The current study is expected to further enhance our understanding regarding moisture induced damage of asphalt mixes and assist in effectively screening good mixes from poor ones.
Article
Time to event data occur commonly in orthopedics research and require special methods that are often called “survival analysis.” These data are complex because both a follow-up time and an event indicator are needed to correctly describe the occurrence of the outcome of interest. Common pitfalls in analyzing time to event data include using methods designed for binary outcomes, failing to check proportional hazards, ignoring competing risks, and introducing immortal time bias by using future information. This article describes the concepts involved in time to event analyses as well as how to avoid common statistical pitfalls.
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COVID-19 is a viral disease that became a pandemic representing a very great challenge worldwide. The purpose of this article is to analyze COVID-19 patients' data based on time-to-event analysis and identify the factors that affect the recovery time from COVID-19. The datasets that are used in this study are for cases that are clinically diagnosed and confirmed where the date of onset is recorded in Wuhan and elsewhere in China from Jan 1 to Feb 11, 2020. We used the regression imputation technique to replace the missing dates in the onset-symptoms based on the dates of the report. We fitted the Kaplan-Meier estimator and Cox regression model to our data. The predictor variables (factors) that we used are age, sex, and onset time to hospitalization. The results show that the young age group is better than the old age group in recovering from COVID-19 (the p-value of the log-rank is 0.00012) and at any time 1.9 as many patients in the young age group are having an event (recovery) proportionally to the old age group. Also, the results show that there is a non-significant difference between male and female groups in recovering from COVID-19 (the p-value of the log-rank is 0.63). The results also show that the early time to hospitalization group can recover from COVID-19 better than the late time to hospitalization group (the p-value of the log-rank is 0.0052). This study demonstrates the association of recovery time from COVID-19 with age, sex, and time to hospitalization.
Article
Abstract Aims: We present the results, in terms of survival, clinical outcome, and radiological appearance at 20 years, in a cohort of 225 cemented Exeter Universal femoral components (Stryker, Newbury, UK) implanted in 207 patients, at a district general hospital. Methods: All patients in this study had a total hip arthroplasty (THA) using an Exeter Universal femoral component with a cemented (n = 215) or cementless (n = 10) acetabular component. Clinical and radiological data were collected prospectively at one year, five years, and every five years thereafter. Patients lost to radiological and clinical follow-up (five) were cross-referenced with National Joint Registry (NJR) data and general practitioner (GP) records to assess whether they had undergone revision for any reason. Results: During this period of study 144 patients (157 hips) died (69.78%). Two patients were lost to follow-up, leaving 61 patients (66 hips) available for review (29.33%). Of the 225 hips, three underwent revision for femoral failure with osteolysis. One underwent femoral component revision for treatment of a periprosthetic fracture. Eight underwent revision of the acetabular component only for loosening. Two hips had both components revised, when components were found to be loose at time of revision for acetabular loosening, though no radiological femoral osteolysis. Two patients underwent revision for infection. Using femoral loosening as an endpoint, the survival of the Exeter Universal femoral component was 98.7% (n = 220, 95% confidence interval (CI) 96.1% to 100%) at 20 to 22 years. Survival with an endpoint of revision for any reason was 92.6% (n = 209, 95% CI 89.4 to 95.55), with a 'worst-case scenario' (considering two patients lost to follow-up to have failed), the overall survival rate was 91.7% (n = 207, 95% CI 87.8 to 95.9) at 20 to 22 years. Conclusion: Our results confirm excellent long-term results for the cemented Exeter Universal femoral componentimplanted outside of the originating centre. Cite this article: Bone Joint J 2020;102-B(10):1319-1323
Article
Background We assessed the survivorship of a proximally hydroxyapatite coated, double tapered, titanium-alloy femoral stem in a single centre, at an average follow up of 12.5 years (10.1 - 15.8). The majority of stems were inserted as part of a Metal on Metal (MoM) Total Hip Replacement (THR). Methods Data was collected prospectively in a local database. A retrospective review was performed of all patients undergoing a primary THR with the prosthesis between 2003 and 2010. Primary outcome was revision of the stem for any cause. Analysis was also performed for stem revision for aseptic loosening, stem revision in the MoM setting and a worst case scenario whereby lost to follow up were presumed to have failed. True stem failure was considered if revision occurred for a stem related complication. Results 1,465 stems were included (1310 patients, 155 bilateral). The bearing surface was cobalt chrome on cobalt chrome in 1351 cases (92%). Seven hips were lost to follow up. Thirty-two stems (31 part of a MoM THR) underwent revision for any cause. Kaplan Meier survival analysis demonstrates an overall 97.4% survivorship. Subset analysis demonstrates 100% survivorship for aseptic loosening, 97.3% in the MoM setting and 96.7% for the worst case senario. Of the 32 cases of stem revision, only 13 were classified as ’true’ stem failure. Conclusion This study represents the largest cohort of this uncemented femoral component with a minimum follow-up longer than 10 years. Our results demonstrate excellent long-term survivorship even in the presence of a challenging MoM environment.
Article
Aims: The Fassier Duval (FD) rod is a third-generation telescopic implant for children with osteogenesis imperfecta (OI). Threaded fixation enables proximal insertion without opening the knee or ankle joint. We have reviewed our combined two-centre experience with this implant. Methods: In total, 34 children with a mean age of five years (1 to 14) with severe OI have undergone rodding of 72 lower limb long bones (27 tibial, 45 femoral) for recurrent fractures with progressive deformity despite optimized bone health and bisphosphonate therapy. Data were collected prospectively, with 1.5 to 11 years follow-up. Results: A total of 24 patients (33%) required exchange of implants (14 femora and ten tibiae) including 11 rods bending with refracture. Four (5%) required reoperation with implant retention. Loss of proximal fixation in the femur and distal fixation in the tibia were common. Four patients developed coxa vara requiring surgical correction. In total, 13 patients experienced further fractures without rod bending; eight required implant revision. There was one deep infection. The five-year survival rate, with rod revision as the endpoint, was 63% (95% confidence interval (CI) 44% to 77%) for femoral rods, with a mean age at implantation of 4.8 years (1.3 to 14.8), and 64% (95% CI 36% to 82%) for tibial rods, with a mean age at implantation of 5.2 years (2.0 to 13.8). Conclusion: FD rods are easier to implant but do not improve on the revision rates reported for second generation T-piece rods. Proximal femoral fixation is problematic in younger children with a partially ossified greater trochanter. Distal tibial fixation typically fails after two years. Future generation implants should address proximal femoral and distal tibial fixation to avoid the majority of complications in this series. Cite this article: Bone Joint J 2020;102-B(8):1048-1055.
Article
Background This study aimed to evaluate the complications and long-term survival of primary total hip arthroplasty (THA) performed by low-volume surgeons at a low-volume hospital. We also determined the relationship between complications and revisions. Methods This retrospective cohort study included 220 THAs in 194 patients treated at our institution between 1998 and 2008, who received a minimum of a 10-year follow-up. The median annual THA volume at this hospital was 23 procedures (range, 11–32), and the annual volume per surgeon ranged from 1 to 19. We investigated the 90-day mortality and rates of periprosthetic joint infections, dislocations, and periprosthetic fractures up to the last visit (median follow-up, 11.8 years). Kaplan–Meier survival was calculated with revision as the end point. Results Postoperative infections, dislocations, and fractures at any time during the follow-up period were reported for one hip (0.5%), 23 hips (9.8%), and four hips (1.8%), respectively. One death occurred within the first 90 days postoperatively. Fifteen hips required revision surgery, and the survival rate was 95.5% at 5 years and 94.1% at 10 years. Of 10 hips that required early revision surgery within 5 years after the index surgery, nine were revisions to address recurrent dislocation. Conclusion The risk of dislocation was high. A high number of patients who underwent THA by low-volume surgeons required early revision due to dislocation. To achieve optimal long-term survivorship, low-volume surgeons should consider measures to reduce the risk of dislocation.
Thesis
This retrospective study of 1149 of cemented intra-medullary stemmed Stanmore bone tumour lower limb massive endo-prostheses, identified that aseptic loosening was the most common form of implant related failure. Revision for aseptic loosening occurred in 14.5% of the 1149 cases. The probability of surviving aseptic loosening for 10 year for proximal femoral, distal femoral and proximal tibial replacements was 87.9%, 65.1% and 51.5% respectively. Patients at greatest risk of loosening were young patients with a distal femoral or proximal tibial replacement, or patients with extensive resections of the distal femur or proximal tibia. Those patients with short proximal femoral resections were at greater risk than those with extensive resections. Clinical and radiographic evaluations of patients were poor predictors of loosening. However, there was a correlation between pain and radiographic radiolucent lines. This study provided impetus to develop three new method of improving implant fixation. These were - 1. enhanced fixation of cemented intra-medullary stemmed replacements using porous beaded collars or hydroxyapatite coated collars. Bony bridging did not occur with porous collared replacements but did with 81.8% of hydroxyapatite coated replacements. 2. uncemented intra-medullary fixation using press-fit, hydroxyapatite coated custom-made stems. After laboratory and cadaveric studies, a clinical trial of 20 patients was undertaken. Early radiographic results of target groups were encouraging. 3. extra-cortical fixation using hydroxyapatite coated extra-cortical plates. Inspired by the first Stanmore replacements, extra-cortical plated fixation was investigated using a goat model. Histological results of mid-shaft tibial replacements identified osseointegrated encompassed plates. The success of the animal model, led to the insertion of an extra-cortical plated distal femoral endo-prosthesis. All three methods of improving the fixation showed encouraging results. The acceptance and increasing use of enhanced methods of fixation has reinforced the value of this work.
Article
Background Total knee arthroplasty is successful elective orthopaedic procedure with an increasing numbers being undertaken. Original knee replacements used an all-polyethylene tibia, however with concerns over tibial loosening the trend moved towards the metal-backed variety. Modern designs providing more conformity and changes in manufacturing of the polyethylene make it an equivalent but cheaper option. Method We analysed the medium term outcome in 1092 patients with an all-polyethylene tibial component in their total knee replacement. Results Twenty-six patients had further surgery on their knee for a variety of reasons. Assessing re-operation for any reason, the seven year survival rate was 96.96% with an overall infection rate was 0.37%. Seven year survival analysis using aseptic loosing as a criteria was 99.28%. Both the SF-12 physical score and WOMAC score significantly improved and was sustained at seven years. Body mass did not correlate to either outcomes or complications. Conclusion An all-polyethylene tibia in a total knee replacement has good outcome data, high patient satisfaction with good survivorship in the medium term, coupled with potential cost-saving benefits.
Article
Aim: Clinical practice is moving away from treating meniscal tears in patients with osteoarthritis unless there are mechanical symptoms. This study assessed the risk of needing further surgery for osteoarthritis in the 5 years following partial meniscectomy in different age groups and different grades of knee osteoarthritis. Methods: All partial meniscectomies were performed by the senior author during a 31-month period. Data were collected and analyzed retrospectively using electronic patients' records and imaging database. Patients who had previous arthroscopy, anterior cruciate ligament pathology, discoid meniscus or were less than 34 years old were excluded from the study. Range of follow-up was 3 to 5 years. Osteoarthritis was classified intra-operatively using the Outerbridge classification. Knees that needed further surgical treatment in the form of joint replacement or osteotomy were considered as failures. The population was split into three groups according to their age (35-54, 55-64 and 65+). Survival analysis was calculated using the life table method. Results: 207 knees were included. In the 35-54 age group, patients with no/mild OA had a survival rate of 97.59% and the severe OA group had a survival rate of 73.5%. In the 55-64 age group, these figures were 100% and 73.6%, respectively. In the >65 age group, the survival rates were 100% and 65%, respectively. Conclusion: Our study shows that patients with no/mild OA should be considered for APM. Patient's with meniscal tears and severe OA should be counseled on the outcomes and risks of further surgery after an APM.
Article
Background: There is variable evidence regarding survivorship beyond 20 years of total hip arthroplasties in young patients. We report the long-term results of the Exeter cemented hip system in patients ≤50 years at minimum of 20 years. Methods: Clinical and radiological outcomes of 130 consecutive total hip arthroplasties in 107 patients aged 50 years or younger at primary operation were reviewed; 77% had a diagnosis other than osteoarthritis. All patients were followed at 5-year intervals, no patients were lost to follow-up, and the status of every implant is known. Results: Mean age at surgery was 41.8 (17-50) years. Mean follow-up was 22.0 (20.0-26.1) years. There were 79 hips surviving, 14 hips (11 patients) deceased, and 37 hips revised. Reasons for revision: 29 hips for aseptic cup loosening (26 stems revised using cement-in-cement, three left in-situ); three stems for femoral osteolysis, two related to acetabular polyethylene wear (14.1 and 17.0 years), one with Gaucher's disease (21.1 years); one broken stem (12.9 years); one cup for instability (4.3 years-stem revised using cement-in-cement); and two hips with infection (8.5 and 23.8 years). There were no cases of aseptic loosening of the Exeter stem. There were no radiologically loose stems although eight patients had radiological evidence of loosening of the cemented cup. Survivorship at 22 years was 74.9% for revision for all causes and 96.3% for revision of the stem for aseptic loosening or lysis. Conclusion: The Exeter cemented stem has excellent survivorship at minimum 20 years in young patients. Acetabular component survivorship was less favorable, but the advent of highly cross-linked polyethylene may improve this in the long term.
Article
Survival analysis is a set of methods used to study the time between enrollment in a study and the occurrence of an event of interest. Two methods are commonly used: actuarial life tables and the Kaplan–Meier approach for survival analysis. A good understanding of both these methods is useful when reading and appraising the literature concerning prognostic and interventional studies. Kaplan–Meier curves are widely used as they enable analysis of incomplete sets of data (i.e. after patients withdraw from studies or are lost to follow up). This review explains these two methods and gives practical examples of their use.
Article
Purpose: The purpose of the current review was to estimate failure rates of trapeziometacarpal (TMC) implants and compare against failure rates of nonimplant techniques for surgical treatment of TMC joint (basal thumb joint) arthritis. Methods: A systematic review was conducted to identify articles reporting on thumb implant arthroplasty and on nonimplant arthroplasty techniques for treatment of base of thumb arthritis in the English literature. The collected data were combined to calculate failure rates per 100 procedure-years. Failure was defined by the requirement for a secondary salvage procedure. The failure rates between different implant and nonimplant arthroplasty groups were compared directly and implants with higher than anticipated failure rates were identified. Results: One hundred twenty-five articles on implant arthroplasty and 33 articles on the outcome of nonimplant surgical arthroplasty of the TMC joint were included. The implant arthroplasty failure rates per 100 procedure-years were total joint replacement (2.4), hemiarthroplasty (2.5), interposition with partial trapezial resection (4.5), interposition with complete trapezial resection (1.7), and interposition with no trapezial resection (4.5). The nonimplant arthroplasty failure rates per 100 procedure-years were: trapeziectomy (0.49), joint fusion (0.52), and trapeziectomy with ligament reconstruction ± tendon interposition (0.23). Conclusions: Several implant designs (arthroplasties) had high rates of failure due to aseptic loosening, dislocation, and persisting pain. Furthermore, some implants had higher than anticipated failure rates than other implants within each class. Overall, the failure rates of nonimplant techniques were lower than those of implant arthroplasty. Type of study/level of evidence: Therapeutic IV.
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Aims: The primary aim of this study was to compare the knee-specific functional outcome of patellofemoral arthroplasty with total knee arthroplasty (TKA) in the management of patients with patellofemoral osteoarthritis. Patients and methods: A total of 54 consecutive Avon patellofemoral arthroplasties were identified and propensity-score-matched to a group of 54 patients undergoing a TKA with patellar resurfacing for patellofemoral osteoarthritis. The Oxford Knee Score (OKS), the 12-Item Short-Form Health Survey (SF-12), and patient satisfaction were collected at a mean follow up of 9.2 years (8 to 15). Survival was defined by revision or intention to revise. Results: There was no significant difference in the mean OKS (p > 0.60) or SF-12 scores (p > 0.28) between the groups. There was a lower rate of satisfaction at the final follow-up for the TKA group (78% vs 87%) but this was not statistically significant (odds ratio 0.56, p = 0.21). Length of stay was significantly shorter (p = 0.008) for the Avon group (difference 1.8 days, 95% confidence interval (CI) 0.4 to 3.2). The ten-year survival for the Avon group was 92.3% (95% CI 87.1 to 97.5) and for the TKA group was 100% (95% CI 93.8 to 100). This difference was not statistically significant (log-rank test, p = 0.10). Conclusion: Patients undergoing an Avon patellofemoral arthroplasty have a shorter length of stay, and a functional outcome and rate of satisfaction that is equal to that of TKA. The benefits of the Avon arthroplasty need to be balanced against the increased rate of revision when compared with TKA.
Article
Purpose Proximal femoral replacements (PFRs) have been recently utilized in complex revision arthroplasties where proximal femoral bone is compromised. The purpose of this study is to evaluate the clinical outcomes, complications, and survivorship of PFRs as a salvage treatment for severe bone loss after non-oncologic revision total hip arthroplasty. Methods This is a retrospective review of all patients who underwent femoral revision surgery using a single design PFR between 2004 and 2013 at our institution. Forty patients (41 hips) were included with a mean age of 64 years (29–90). According to Paprosky classification, 15 femurs had type IIIB defect, and 26 had type IV defect. Patients were followed for a mean of five years (2–10). The average length of reconstruction was 150 mm (81–261). A Kaplan–Meier analysis was used to determine the survival of the PFR. Results A total of nine patients (9 PFRs, 22%) were re-operated upon. Three re-operations were for infection, two for dislocation, two for aseptic loosening, and two for periprosthetic fracture. The survivorship at five years was 95.1% for revision of the femoral stem for aseptic loosening. We did not find length of the segmental reconstruction or the indication for revision, to be a risk factor for implant failure or re-revision. Conclusions Proximal femoral replacements have shown an acceptable survivorship in non-oncologic revision hip arthroplasties for severe proximal femoral bone loss. The frequent use of constrained liners may decrease the risk of dislocation due to the loss of the abductor mechanism encountered in these complex reconstructions.
Article
Sixty-eight young patients (74 prostheses), mean age 43 years (standard deviation 7. 7) at the time of the index operation, with a Zweymüller cementless total hip prosthesis were evaluated with a mean follow-up time of 75 months (SD 15.7). At follow-up, the mean Harris Hip Score was 94 (SD 8.1). Six stem prostheses had vertical subsidence and nine cups showed signs indicating possible loosening. The Oxford Hip Score averaged 19 points (SD 8.7). Revision surgery was performed for septic loosening (n=3 stem and cup prostheses), for aseptic loosening of the cup (n=2), and for a traumatic periprosthetic fracture (n=1 stem). Worst case survival analysis for aseptic loosening of the cup showed a probability for revision of 3% (Cl95 0 - 7.2%) with a cumulative survival of 96% (Cl95 100 - 90.3%) after 84 months. For the stem prostheses the probability for revision was 1% (Cl95 0 - 4.3%) after 114 months with a cumulative survival of 99% (Cl95 100 - 95.8%) after 72 months. Worst case cumulative survival for any reason of revision was 94.5% (Cl95 99.9 - 89.2%) after 81 months. Promising results of the Zweymüller cementless hip prosthesis for the younger patient were obtained, although longer follow-up will be necessary.
Article
Background: Oxidised zirconium has the wear properties of ceramic with the breakage resistance of metal. This results in less wear and is of benefit to younger, higher demand patients. We report the short- to mid-term survival of 103 Profix zirconium total knee replacements performed in patients under 50years of age at time of surgery. Methods: Data was collected prospectively and survival analysis undertaken with strict end points used. SF (Short Form) 12 and WOMAC (Western Ontario and McMaster University) scores were recorded at pre-operatively and at twelve months, one, three, five, seven and ten years. Results: The average age at operation was 43.21years (range 20-50years) with a mean follow-up of 8.56years (range five to 15years). No patients died with one patient lost to follow-up after seven year review. The mean WOMAC score improved from 53 to 29, and the mean SF12 physical component improved from 29 to 36. The five year survivorship for implant related complications was 99.03% (95% CI 94.64-100.0) due to tibial component aseptic loosening at year one. Reoperation for any cause at five years including stiffness was 94.09% (95% CI 88.69-98.11). Forty-four patients were at least ten years post-operative at the time of analysis, with no aseptic loosening of either component giving 10year femoral component survival of 100% and all cause revision of 95.4%. The only zirconium femoral failure was at 12years. Conclusions: Our data shows excellent mid-term survivorship of oxidised zirconium total knee replacements in younger, higher demand patients.
Article
Background: We report 15-year survival, clinical, and radiographic follow-up data for the Press-Fit Condylar Sigma total knee arthroplasty. Methods: Between October 1998 and October 1999, 235 consecutive TKAs were performed in 203 patients. Patients were reviewed at a specialist nurse-led clinic before surgery and at 5, 8-10, and 15 years postoperatively. Clinical outcomes, including Knee Society Score, were recorded prospectively at each clinic visit, and radiographs were obtained. Results: Of our initial cohort, 99 patients (118 knees) were alive at 15 years, and 31 patients (34 knees) were lost to follow-up. Thirteen knees (5.5%) were revised; 5 (2.1%) for infection, 7 (3%) for instability, and 1 (0.4%) for aseptic loosening. Cumulative survival with the end point of revision for any reason was 92.3% at 15 years and with revision for aseptic failure as the end point was 94.4%. The mean Knee Society Score knee score was 77.4 (33-99) at 15 years, compared with 31.7 (2-62) preoperatively. Of 71 surviving knees for which X-rays were available, 12 (16.9%) had radiolucent lines and 1 (1.4%) demonstrated clear radiographic evidence of loosening. Conclusion: The Press-Fit Condylar Sigma total knee arthroplasty represents a durable, effective option for patients undergoing knee arthroplasty, with excellent survival and good clinical and radiographic outcomes at 15 years.
Article
We reviewed 264 consecutive primary total hip replacements in 244 patients in which the Harris-Galante I porous-coated acetabular component had been used. The mean follow-up was 95 months (69 to 132). In 221 arthroplasties a 32 mm ceramic head had been used, and in the other 43 one of cobalt-chrome alloy. There were 124 women and 120 men with a mean age at operation of 56.8 years (21 to 83). Survival analysis of the acetabular components was performed using the following definitions of failure: 1) infection; 2) removal because of aseptic loosening; 3) removal for any cause; and 4) a worst-case analysis including removal of the cup or infection or loss to follow-up. Two well-fixed cups had been removed because of deep infection and three, similarly sound cups had been exchanged at the time of femoral revision. None of the acetabular components had required revision for aseptic loosening. After 11 years survival was 97.7% using the worst-case criterion. Radiological analysis of 187 acetabular components at a mean of 82 months (41 to 132) revealed no case of aseptic loosening. Pelvic osteolysis was seen in only one patient, but was not progressive and showed signs of regression. The results using these acetabular components are encouraging but the need for regular follow-up remains since complications such as significant wear of the liner, massive osteolysis of the pelvis, aseptic loosening and late infection may increase in the second decade.
Article
We reviewed retrospectively 25 hip arthroplasties in 25 patients with sickle-cell haemoglobinopathy and osteonecrosis. The mean age of the ten women and 15 men at the onset of hip symptoms was 25 years, and at surgery 30 years (16 to 45); 66% had either SS or S-thal disease, 20% sickle-cell trait, and the remainder SC disease. The mean follow-up was 8.6 years (two to 18). Fourteen (40%) of the arthroplasties had been revised at a mean of 7.5 years after the primary procedure and nine other hips were either radiographically and/or symptomatically loose. The overall complication rate was 49% and the infection rate 20%. The risk-to-benefit ratio of hip arthroplasty in sickle-cell haemoglobinopathy is high.