human
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Surgery and other invasive therapies are complex interventions , the assessment of which is challenged by factors that depend on operator , team , and setting , such as learning curves , quality variations , and perception of equipoise . We propose recommendations for the assessment of surgery based on a five-stage description of the surgical development process . We also encourage the widespread use of prospect i ve data bases and registries . Reports of new techniques should be registered as a professional duty , anonymously if necessary when outcomes are adverse . Case series studies should be replaced by prospect i ve development studies for early technical modifications and by prospect i ve research data bases for later pre-trial evaluation . Protocol s for these studies should be registered publicly . Statistical process control techniques can be useful in both early and late assessment . R and omised trials should be used whenever possible to investigate efficacy , but adequate pre-trial data are essential to allow power calculations , clarify the definition and indications of the intervention , and develop quality measures . Difficulties in doing r and omised clinical trials should be addressed by measures to evaluate learning curves and alleviate equipoise problems . Alternative prospect i ve design s , such as interrupted time series studies , should be used when r and omised trials are not feasible . Established procedures should be monitored with prospect i ve data bases to analyse outcome variations and to identify late and rare events . Achievement of improved design , conduct , and reporting of surgical research will need concerted action by editors , funders of health care and research , regulatory bodies , and professional societies We report a prospect i ve , stratified study of 60 PCA-cups and 60 RM-polyethylene cups which have been followed for a median time of 90 months , with annual radiography .  The radiological migration of cups was measured by the computer-assisted EBRA method . A number of threshold migration rates from 1 mm in the first year to 1 mm in five years have been assessed and related to clinical ly determined revision rates . A total of 28 cups showed a total migration of 1 mm or more within the first two years ; 13 of these cups have required revision and been exchanged . The survival curves of cups which had previously shown early migration were considerably different from those without early migration . For cups with a migration of less than 1 mm within the first two years the mean survival at 96 months was 0.96 + /- 0.02 ; for migrating cups , it was 0.63 + /- 0.11 ( log-rank test , p=0.0001 ; chi-square value=39.4 ) . Early migration is a good predictor for late loosening of hip sockets The IDEAL framework describes the stages of evaluation for surgical innovations . This paper considers the role of observational studies in the exploration and assessment stages . At the exploration stage , the surgical intervention is usually more widely used , and observational studies should collect prospect i ve data from multiple surgeons , deal with factors such as case mix and learning , and prepare for a definitive evaluation at the next stage of assessment . Although a r and omised controlled trial is preferable , a high quality observational study would be acceptable if a r and omised trial is not feasible or , on rare occasions , deemed unnecessary The complexity of surgical procedures often poses challenges for conducting a rigorous and comprehensive evaluation . This paper considers the final two IDEAL stages of surgical innovation . Surgical r and omised controlled trials are often challenging to undertake and require careful consideration of the intervention definition , who should deliver it , and the impact of surgeon and patient preferences . In the long term study stage , better monitoring of surgical procedures is needed , along with improved surveillance of devices Background Due to its collarless , double-tapered polished design , the Exeter femoral stem is known to migrate distally in the first 5 years after implantation . However , its long-term migration pattern has not been investigated . Patients and methods 39 consecutive patients ( 41 total hip arthroplasties ) received a cemented Exeter stem and had prospect i ve clinical and RSA follow-up . Patients were evaluated postoperatively at 6 , 12 , 26 , and 52 weeks , and annually thereafter . Short-term results have been reported . In this study , the mean length of follow-up was 9.4 years ( SD 3.2 years ) . No patients were lost to follow-up . 15 patients died during follow-up . Results No stems were revised . In 4 stems , fractures of the cement mantle were noted within the first 3 postoperative years . In 3 stems , this result ed in a complete circumferential cement mantle discontinuity . For the 37 well-performing stems , continuous but small migration was measured between 2 and 12 years of follow-up . Continued subsidence of 0.08 mm/year ( 95 % CI : 0.05–0.12 , p < 0.001 ) was seen in combination with continued rotation in retroversion of 0.07 ° /year ( 95 % CI : 0.02–0.12 , p = 0.01 ) . At 10 years of follow-up , mean subsidence was 2.1 ( SD 1.2 ) mm and mean retroversion was 1.8 ° ( SD 2.0 ) . Two-thirds of this occurred during the first 2 postoperative years . In the 3 stems with a complete circumferential cement fracture , a sudden and disproportionately high increase in subsidence was measured in the time period of occurrence . Interpretation The Exeter femoral stem continues to migrate during the first decade after implantation . Absolute stability is not required for good long-term survival if this is compatible with the design of the implant The  vertical migration of four configurations of a proximal femoral prosthesis , followed for up to nine years , was measured on st and ard radiographs . The same implant was used without cement ( group 1 ) and with cement ( group 2 ) . The migration of both groups was linear from six months onwards . The mean migration rate and the incidence of late aseptic loosening were both greater in group 1 . Survival analysis of the two groups , however , showed no statistically significant difference . In both groups , hips later destined for revision migrated more rapidly from the initial postoperative period onwards , than did the remainder . A threshold migration of 1.2 mm/year during the first two years after implantation detected hips likely to fail with a specificity of 86 % and a sensitivity of 78 % . This ' migration test ' was applied to the results in two further groups of patients in which a modified femoral prosthesis had been implanted without hydroxyapatite coating ( group 3 ) and with hydroxyapatite coating  ( group 4 ) . The test distinguished between the four groups and suggested that at least two fixation procedures should be ab and oned . We conclude that vertical migration measured on st and ard radiographs in the first two years after implantation can be used to predict late aseptic loosening . New prosthetic configurations should be evaluated by migration measurements before their general release . Our observations support the view that one cause of late aseptic loosening is imperfect initial fixation BACKGROUND The use of highly cross-linked polyethylene is now commonplace in total hip arthroplasty . Hip simulator studies and short-term in vivo measurements have suggested that the wear rate of highly cross-linked polyethylene is significantly less than that of conventional ultra-high molecular weight polyethylene . However , long-term data to support its use are limited . The aim of this study was to compare the intermediate-term steady-state wear of highly cross-linked polyethylene compared with that of conventional ultra-high molecular weight polyethylene acetabular liners in a prospect i ve , double-blind , r and omized controlled trial with use of radiostereometric analysis . METHODS Fifty-four patients were r and omized to receive hip replacements with either conventional ultra-high molecular weight polyethylene acetabular liners ( Zimmer ) or highly cross-linked polyethylene liners ( Longevity ; Zimmer ) . All patients received a cemented , collarless , polished , tapered femoral component ( CPT ; Zimmer ) and an uncemented acetabular component ( Trilogy ; Zimmer ) . Clinical outcomes were assessed and the three-dimensional penetration of the head into the socket was determined for a minimum of seven years . Linear regression was used to calculate the steady-state wear rate following the creep-dominated penetration seen during the first year . RESULTS At a minimum of seven years postoperatively , the mean total femoral head penetration was significantly lower in the highly cross-linked polyethylene group ( 0.33 mm ; 95 % confidence interval [ CI ] , ±0.10 mm ) than it was in the ultra-high molecular weight polyethylene group ( 0.55 mm ; 95 % CI , ±0.10 mm ) ( p = 0.005 ) . The mean steady-state wear rate  of highly cross-linked polyethylene was 0.005 mm/yr ( 95 % CI , ±0.015 mm/yr ) , compared with 0.037 mm/yr ( 95 % CI , ±0.019 mm/yr ) for conventional ultra-high molecular weight polyethylene ( p = 0.007 ) . No patient in the highly cross-linked polyethylene group had a wear rate above the osteolysis threshold of 0.1 mm/yr , compared with 9 % of patients in the ultra-high molecular weight polyethylene group . CONCLUSIONS This study demonstrates that highly cross-linked polyethylene has a significantly lower steady-state wear rate compared with that of conventional ultra-high molecular weight polyethylene . Longer-term follow-up is required to determine if this will translate into improved clinical performance and longevity of these implants BACKGROUND Excessive early migration of femoral stems following total hip arthroplasty and tibial components following total knee arthroplasty is associated with their long-term survival and allows reliable early evaluation of implant performance . However , a similar relationship involving acetabular components following hip arthroplasty has not been evaluated . This prospect i ve , long-term study with clinical and Roentgen stereophotogrammetric analysis ( RSA ) follow-up establishes the existence of this relationship and its associated diagnostic performance . METHODS Thirty-nine consecutive patients ( forty-one hips ) who underwent total hip arthroplasty with a cemented Exeter stem and a cemented Exeter all-polyethylene cup had prospect i ve clinical and RSA follow-up . Patients were evaluated postoperatively at six weeks , at three , six , and twelve months , and annually thereafter . Conventional anteroposterior and lateral radiographs were made at six weeks and at two , five , and ten years postoperatively as well as when indicated . The mean duration of follow-up ( and st and ard deviation ) was 9.4 ± 3.2 years . No patients were lost to follow-up ; fifteen patients died during the follow-up period . RESULTS Eleven acetabular components were observed to be loose on conventional radiographs after a mean of seventy-six months ( range , twelve to 140 months ) . During the first two postoperative years , the failed acetabular components showed markedly greater and more rapid cranial translation and sagittal rotation . Both cranial translation ( hazard ratio = 19.9 [ 95 % confidence interval , 4.94 to 80.0 ] , p < 0.001 ) and sagittal rotation ( hazard ratio = 11.1 [ 95 % confidence interval , 2.83 to 43.9 ] , p = 0.001 ) were strong risk factors for late aseptic loosening . Eight of the eleven failed components showed a distinctive pattern of excessive cranial translation combined with excessive sagittal rotation . The associated diagnostic performance of two-year cranial translation and /or sagittal rotation for predicting late aseptic loosening of the acetabular component was good ( area under the receiver operating characteristic curve , 0.88 [ 95 % confidence interval , 0.74 to 1.00 ; p < 0.001 ] and 0.84 [ 95 % confidence interval , 0.68 to 1.00 ; p = 0.001 ] , respectively ) . CONCLUSIONS Early migration , as measured by RSA at two years postoperatively , has good diagnostic capabilities for the detection of acetabular components at risk for future aseptic loosening , and this method appears to be an appropriate means of assessing the performance of new implants or implant-related changes Background  Acetabular screw cups  seem to give high primary stability . We analyzed the migration and loosening behavior of a first-generation screw cup in a longterm follow-up . Patients and methods We examined 92 uncemented titanium alloy conical screw cups prospect ively .  Implant migration was assessed with a digital high-precision method ( EBRA ) with an accuracy of 1.0 mm . Results After mean 11 ( 0.5–18 ) years , 87 patients were available for examination and 5 patients had died . 32 implants had been revised and 7 cases showed radiographic evidence of loosening . The 10-year survival rate was 71 % . Migration of more than 1 mm occurred in 53 hips . Implant survival was strongly associated with an annual migration of greater than 0.2 mm . Interpretation The long-term behavior of this cup is not satisfactory . In spite of extraordinarily high primary implant stability , secondary osseointegration of this cup often fails . The annual migration rate represents a valid parameter for prediction of implant survival Roentgen stereophotogrammetry was used to measure the migration of the centre of the femoral head in 84 cemented Lubinus SP I hip arthroplasties ( 58 primary operations , 26 revisions ) . Four to seven years later , seven femoral components had been revised because of painful loosening . These implants showed greater subsidence , medial migration and posterior migration during the first two postoperative years than did the hips which had not been revised . Six months after operation , subsidence of more than 0.33 mm combined with a total migration of more than 0.85 
    Output:
    
agent
Patient Reported Outcome Measures ( PROMs ) at six months have been investigated but have not been vali date d against long-term outcomes .
EBRA can be used to investigate acetabular wear but not femoral migration .
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Surgery and other invasive therapies are complex interventions , the assessment of which is challenged by factors that depend on operator , team , and setting , such as learning curves , quality variations , and perception of equipoise . We propose recommendations for the assessment of surgery based on a five-stage description of the surgical development process . We also encourage the widespread use of prospect i ve data bases and registries . Reports of new techniques should be registered as a professional duty , anonymously if necessary when outcomes are adverse . Case series studies should be replaced by prospect i ve development studies for early technical modifications and by prospect i ve research data bases for later pre-trial evaluation . Protocol s for these studies should be registered publicly . Statistical process control techniques can be useful in both early and late assessment . R and omised trials should be used whenever possible to investigate efficacy , but adequate pre-trial data are essential to allow power calculations , clarify the definition and indications of the intervention , and develop quality measures . Difficulties in doing r and omised clinical trials should be addressed by measures to evaluate learning curves and alleviate equipoise problems . Alternative prospect i ve design s , such as interrupted time series studies , should be used when r and omised trials are not feasible . Established procedures should be monitored with prospect i ve data bases to analyse outcome variations and to identify late and rare events . Achievement of improved design , conduct , and reporting of surgical research will need concerted action by editors , funders of health care and research , regulatory bodies , and professional societies We report a prospect i ve , stratified study of 60 PCA-cups and 60 RM-polyethylene cups which have been followed for a median time of 90 months , with annual radiography .  The radiological migration of cups was measured by the computer-assisted EBRA method . A number of threshold migration rates from 1 mm in the first year to 1 mm in five years have been assessed and related to clinical ly determined revision rates . A total of 28 cups showed a total migration of 1 mm or more within the first two years ; 13 of these cups have required revision and been exchanged . The survival curves of cups which had previously shown early migration were considerably different from those without early migration . For cups with a migration of less than 1 mm within the first two years the mean survival at 96 months was 0.96 + /- 0.02 ; for migrating cups , it was 0.63 + /- 0.11 ( log-rank test , p=0.0001 ; chi-square value=39.4 ) . Early migration is a good predictor for late loosening of hip sockets The IDEAL framework describes the stages of evaluation for surgical innovations . This paper considers the role of observational studies in the exploration and assessment stages . At the exploration stage , the surgical intervention is usually more widely used , and observational studies should collect prospect i ve data from multiple surgeons , deal with factors such as case mix and learning , and prepare for a definitive evaluation at the next stage of assessment . Although a r and omised controlled trial is preferable , a high quality observational study would be acceptable if a r and omised trial is not feasible or , on rare occasions , deemed unnecessary The complexity of surgical procedures often poses challenges for conducting a rigorous and comprehensive evaluation . This paper considers the final two IDEAL stages of surgical innovation . Surgical r and omised controlled trials are often challenging to undertake and require careful consideration of the intervention definition , who should deliver it , and the impact of surgeon and patient preferences . In the long term study stage , better monitoring of surgical procedures is needed , along with improved surveillance of devices Background Due to its collarless , double-tapered polished design , the Exeter femoral stem is known to migrate distally in the first 5 years after implantation . However , its long-term migration pattern has not been investigated . Patients and methods 39 consecutive patients ( 41 total hip arthroplasties ) received a cemented Exeter stem and had prospect i ve clinical and RSA follow-up . Patients were evaluated postoperatively at 6 , 12 , 26 , and 52 weeks , and annually thereafter . Short-term results have been reported . In this study , the mean length of follow-up was 9.4 years ( SD 3.2 years ) . No patients were lost to follow-up . 15 patients died during follow-up . Results No stems were revised . In 4 stems , fractures of the cement mantle were noted within the first 3 postoperative years . In 3 stems , this result ed in a complete circumferential cement mantle discontinuity . For the 37 well-performing stems , continuous but small migration was measured between 2 and 12 years of follow-up . Continued subsidence of 0.08 mm/year ( 95 % CI : 0.05–0.12 , p < 0.001 ) was seen in combination with continued rotation in retroversion of 0.07 ° /year ( 95 % CI : 0.02–0.12 , p = 0.01 ) . At 10 years of follow-up , mean subsidence was 2.1 ( SD 1.2 ) mm and mean retroversion was 1.8 ° ( SD 2.0 ) . Two-thirds of this occurred during the first 2 postoperative years . In the 3 stems with a complete circumferential cement fracture , a sudden and disproportionately high increase in subsidence was measured in the time period of occurrence . Interpretation The Exeter femoral stem continues to migrate during the first decade after implantation . Absolute stability is not required for good long-term survival if this is compatible with the design of the implant The  vertical migration of four configurations of a proximal femoral prosthesis , followed for up to nine years , was measured on st and ard radiographs . The same implant was used without cement ( group 1 ) and with cement ( group 2 ) . The migration of both groups was linear from six months onwards . The mean migration rate and the incidence of late aseptic loosening were both greater in group 1 . Survival analysis of the two groups , however , showed no statistically significant difference . In both groups , hips later destined for revision migrated more rapidly from the initial postoperative period onwards , than did the remainder . A threshold migration of 1.2 mm/year during the first two years after implantation detected hips likely to fail with a specificity of 86 % and a sensitivity of 78 % . This ' migration test ' was applied to the results in two further groups of patients in which a modified femoral prosthesis had been implanted without hydroxyapatite coating ( group 3 ) and with hydroxyapatite coating  ( group 4 ) . The test distinguished between the four groups and suggested that at least two fixation procedures should be ab and oned . We conclude that vertical migration measured on st and ard radiographs in the first two years after implantation can be used to predict late aseptic loosening . New prosthetic configurations should be evaluated by migration measurements before their general release . Our observations support the view that one cause of late aseptic loosening is imperfect initial fixation BACKGROUND The use of highly cross-linked polyethylene is now commonplace in total hip arthroplasty . Hip simulator studies and short-term in vivo measurements have suggested that the wear rate of highly cross-linked polyethylene is significantly less than that of conventional ultra-high molecular weight polyethylene . However , long-term data to support its use are limited . The aim of this study was to compare the intermediate-term steady-state wear of highly cross-linked polyethylene compared with that of conventional ultra-high molecular weight polyethylene acetabular liners in a prospect i ve , double-blind , r and omized controlled trial with use of radiostereometric analysis . METHODS Fifty-four patients were r and omized to receive hip replacements with either conventional ultra-high molecular weight polyethylene acetabular liners ( Zimmer ) or highly cross-linked polyethylene liners ( Longevity ; Zimmer ) . All patients received a cemented , collarless , polished , tapered femoral component ( CPT ; Zimmer ) and an uncemented acetabular component ( Trilogy ; Zimmer ) . Clinical outcomes were assessed and the three-dimensional penetration of the head into the socket was determined for a minimum of seven years . Linear regression was used to calculate the steady-state wear rate following the creep-dominated penetration seen during the first year . RESULTS At a minimum of seven years postoperatively , the mean total femoral head penetration was significantly lower in the highly cross-linked polyethylene group ( 0.33 mm ; 95 % confidence interval [ CI ] , ±0.10 mm ) than it was in the ultra-high molecular weight polyethylene group ( 0.55 mm ; 95 % CI , ±0.10 mm ) ( p = 0.005 ) . The mean steady-state wear rate  of highly cross-linked polyethylene was 0.005 mm/yr ( 95 % CI , ±0.015 mm/yr ) , compared with 0.037 mm/yr ( 95 % CI , ±0.019 mm/yr ) for conventional ultra-high molecular weight polyethylene ( p = 0.007 ) . No patient in the highly cross-linked polyethylene group had a wear rate above the osteolysis threshold of 0.1 mm/yr , compared with 9 % of patients in the ultra-high molecular weight polyethylene group . CONCLUSIONS This study demonstrates that highly cross-linked polyethylene has a significantly lower steady-state wear rate compared with that of conventional ultra-high molecular weight polyethylene . Longer-term follow-up is required to determine if this will translate into improved clinical performance and longevity of these implants BACKGROUND Excessive early migration of femoral stems following total hip arthroplasty and tibial components following total knee arthroplasty is associated with their long-term survival and allows reliable early evaluation of implant performance . However , a similar relationship involving acetabular components following hip arthroplasty has not been evaluated . This prospect i ve , long-term study with clinical and Roentgen stereophotogrammetric analysis ( RSA ) follow-up establishes the existence of this relationship and its associated diagnostic performance . METHODS Thirty-nine consecutive patients ( forty-one hips ) who underwent total hip arthroplasty with a cemented Exeter stem and a cemented Exeter all-polyethylene cup had prospect i ve clinical and RSA follow-up . Patients were evaluated postoperatively at six weeks , at three , six , and twelve months , and annually thereafter . Conventional anteroposterior and lateral radiographs were made at six weeks and at two , five , and ten years postoperatively as well as when indicated . The mean duration of follow-up ( and st and ard deviation ) was 9.4 ± 3.2 years . No patients were lost to follow-up ; fifteen patients died during the follow-up period . RESULTS Eleven acetabular components were observed to be loose on conventional radiographs after a mean of seventy-six months ( range , twelve to 140 months ) . During the first two postoperative years , the failed acetabular components showed markedly greater and more rapid cranial translation and sagittal rotation . Both cranial translation ( hazard ratio = 19.9 [ 95 % confidence interval , 4.94 to 80.0 ] , p < 0.001 ) and sagittal rotation ( hazard ratio = 11.1 [ 95 % confidence interval , 2.83 to 43.9 ] , p = 0.001 ) were strong risk factors for late aseptic loosening . Eight of the eleven failed components showed a distinctive pattern of excessive cranial translation combined with excessive sagittal rotation . The associated diagnostic performance of two-year cranial translation and /or sagittal rotation for predicting late aseptic loosening of the acetabular component was good ( area under the receiver operating characteristic curve , 0.88 [ 95 % confidence interval , 0.74 to 1.00 ; p < 0.001 ] and 0.84 [ 95 % confidence interval , 0.68 to 1.00 ; p = 0.001 ] , respectively ) . CONCLUSIONS Early migration , as measured by RSA at two years postoperatively , has good diagnostic capabilities for the detection of acetabular components at risk for future aseptic loosening , and this method appears to be an appropriate means of assessing the performance of new implants or implant-related changes Background  Acetabular screw cups  seem to give high primary stability . We analyzed the migration and loosening behavior of a first-generation screw cup in a longterm follow-up . Patients and methods We examined 92 uncemented titanium alloy conical screw cups prospect ively .  Implant migration was assessed with a digital high-precision method ( EBRA ) with an accuracy of 1.0 mm . Results After mean 11 ( 0.5–18 ) years , 87 patients were available for examination and 5 patients had died . 32 implants had been revised and 7 cases showed radiographic evidence of loosening . The 10-year survival rate was 71 % . Migration of more than 1 mm occurred in 53 hips . Implant survival was strongly associated with an annual migration of greater than 0.2 mm . Interpretation The long-term behavior of this cup is not satisfactory . In spite of extraordinarily high primary implant stability , secondary osseointegration of this cup often fails . The annual migration rate represents a valid parameter for prediction of implant survival Roentgen stereophotogrammetry was used to measure the migration of the centre of the femoral head in 84 cemented Lubinus SP I hip arthroplasties ( 58 primary operations , 26 revisions ) . Four to seven years later , seven femoral components had been revised because of painful loosening . These implants showed greater subsidence , medial migration and posterior migration during the first two postoperative years than did the hips which had not been revised . Six months after operation , subsidence of more than 0.33 mm combined with a total migration of more than 0.85 
    Output:
    