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: Highly cross-linked polyethylene was developed to reduce articular bearing wear in total hip arthroplasty . In vitro studies have shown reduced wear in comparison with conventional polyethylene . A double-blind , prospect i ve , r and omized trial was performed comparing highly cross-linked and conventional polyethylene  in 119 patients . The primary outcome variables were linear , 3-dimensional , and volumetric wear as determined by analysis of digitized radiographs using vali date d wear measurement software . Linear , 3-dimensional , and volumetric wear rates were significantly less in the highly cross-linked polyethylene group between 6 months and 4 years postoperatively ( P < .05 ) . The data presented here show that highly cross-linked polyethylene reduces short-term polyethylene wear . The intermediate and long-term clinical results of highly cross-linked polyethylene remain unknown pending further follow-up Mixed treatment comparison ( MTC ) meta- analysis is a generalization of st and ard pairwise meta- analysis for A vs B trials , to data structures that include , for example , A vs B , B vs C , and A vs C trials . There are two roles for MTC : one is to strengthen inference concerning the relative efficacy of two treatments , by including both ' direct ' and ' indirect ' comparisons . The other is to facilitate simultaneous inference regarding all treatments , in order for example to select the best treatment . In this paper , we present a range of Bayesian hierarchical models using the Markov chain Monte Carlo software WinBUGS . These are multivariate r and om effects models that allow for variation in true treatment effects across trials . We consider models where the between-trials variance is homogeneous across treatment comparisons as well as heterogeneous variance models . We also compare models with fixed ( unconstrained ) baseline study effects with models with r and om baselines drawn from a common distribution . These models are applied to an illustrative data set and posterior parameter distributions are compared . We discuss model critique and model selection , illustrating the role of Bayesian deviance analysis , and node-based model criticism . The assumptions underlying the MTC models and their parameterization are also discussed Ultra-high-molecular-weight polyethylene sterilised in the absence of air and highly cross-linked polyethylene have been used to avoid osteolysis and loosening in total hip replacement . Our prospect i ve r and omised study has assessed the results using two different polyethylenes associated with the same prosthetic design . We assessed 45 Allofit acetabular components with a Sulene-polyethylene liner of conventional polyethylene gamma sterilised with nitrogen and 45 Allofit acetabular components with a Durasul-polyethylene liner sterilised in ethylene oxide , both matched with an Alloclassic stem  with a 28 mm modular femoral head . The prostheses were implanted between May 1999 and December 2001 . The mean follow-up was for 66.3 months ( 60 to 92 ) . The linear penetration of the femoral head was estimated at 6 weeks , at 6 and 12 months and annually thereafter from st and ardised digitised radiographs using image- analysis software . There was no loosening of any prosthetic component . There were no radiolucent lines or osteolysis . The mean rate of penetration calculated from regression analysis during the first five years was 38 microm/year ( SD 2 ) for the Sulene group and 6 microm/year ( SD 1 ) for the Durasul group ( p = 0.00002 ) . The rate of penetration of the Durasul group was 15.7 % of that of the Sulene group Background Although hip arthroplasty reliably relieves pain and improves function , problems have arisen with wear and osteolysis .  Highly crosslinked polyethylene has been developed to address this problem although at present there is limited clinical evidence it does so longer term . Questions / purpose sWe compared the in vivo wear of st and ard versus highly crosslinked polyethylene ( HXLP ) in primary total hip arthroplasty at a minimum of 5-year followup . Methods We enrolled 122 patients in a prospect i ve , double-blinded , r and omized trial and followed them annually to assess their progress . Annual radiographs were analyzed using previously vali date d edge detection software to assess for two-dimensional , three-dimensional , and volumetric wear . The mean follow up was 5.5 years ( range , 4.1 to 7 years ) . Results The two-dimensional wear measurements for HXLP showed lower wear compared to the conventional group ( 0.05 mm/year versus 0.26 mm/year , respectively ) . Three-dimensional and volumetric wear were similarly lower in the HXLP group . Conclusions Highly crosslinked polyethylene undergoes substantially less wear than conventional polyethylene at medium term . The effect of hip arthroplasty longevity will need to be assessed with longer-term studies , but this may lead to a decreased need for revision as a result of less wear and osteolysis . Level of Evidence Level I , therapeutic study . See Guidelines for Authors for a complete description of levels of evidence Abstract Wear particle-induced osteolysis is a major cause of aseptic loosening in THA . Increasing wear resistance of polyethylene ( PE ) occurs by increasing the cross-link density and early reports document low wear rates with such implants . To confirm longer-term reductions in wear we compared cross-linked polyethylene ( irradiation in nitrogen , annealing ) with historical polyethylene ( irradiation in air ) in a prospect i ve , r and omized clinical study involving 48 patients who underwent THAs with a minimum followup of 7 years ( mean , 8 years ; range , 7–9 years ) . The insert material was the only variable . The Harris hip score , radiographic signs of osteolysis , and polyethylene wear were recorded annually . Twenty-three historical and 17 moderately cross-linked polyethylene inserts were analyzed ( five patients died , three were lost to followup ) . At 8 years , the wear rate was lower for cross-linked polyethylene ( 0.088 ± 0.03 mm/year ) than for the historical polyethylene ( 0.142 ± 0.07 mm/year ) . This reduction ( 38 % ) did not diminish with time ( 33 % at 5 years ) . Acetabular cyst formation was less frequent ( 39 % versus 12 % ) , affected fewer DeLee and Charnley zones ( 17 % versus 4 % ) , and was less severe for the cross-linked polyethylene . The only revision was for an aseptically loose cup in the historical polyethylene group . Moderately cross-linked polyethylene maintained its wear advantage with time and produced less osteolysis , showing no signs of aging at mid-term followup . Level of Evidence : Level I , therapeutic study . See Guidelines for Authors for a complete description of levels of evidence The results of a prospect i ve multicenter trial comparing 357 hips r and omized to total hip arthroplasty with either ceramic-ceramic or ceramic-polyethylene couplings  are presented . No statistically significant difference in clinical outcomes scores between the ceramic-ceramic and ceramic-polyethylene groups was observed at any time interval . The mean linear rate was statistically lower ( P < .001 ) in the ceramic-ceramic group ( 30.5 μm/year ) when compared with the ceramic-polyethylene group ( 218.2 μm/year ) . The rates of ceramic implant fracture ( 2.6 % ) and audible component-related noise ( 3.1 % ) were statistically higher in the ceramic-ceramic group when compared with the ceramic-polyethylene group ( P < .05 ) . Lastly , there was no statistically significant difference in the dislocation or revision rate between the groups at the time of last clinical follow-up Purpose Very few studies have compared alumina-on-alumina ceramic and alumina-on-highly cross-linked polyethylene bearings in the same patient . The purpose of this prospect i ve r and omised study was to compare the clinical and radiographic results and the prevalence of osteolysis in cementless total hip arthroplasty using an alumina-on-alumina and alumina-on-highly cross-linked polyethylene bearings in young active patients . Methods We prospect ively compared the results of 100 patients ( 200 hips ) who had undergone a cementless total hip arthroplasty with an alumina-on-alumina ceramic bearing in one hip and an alumina-on-highly cross-linked polyethylene in the other . There were 66 men and 34 women with a mean age of 45.3 years ( range , 21–49 years ) at the time of surgery . The mean follow-up was 12.4 years ( range , 11–13 years ) . The patients were assessed clinical ly and radiographically at three months , one year , and annually thereafter . Results Harris hip , Western Ontario and McMaster Universities Osteoarthritis Index , and University of California , Los Angeles activity scores did not show statistically significant differences between the two groups of bearings preoperatively or at the time of final follow-up . Radiographic findings of the component were not significantly different between the two groups . The mean polyethylene linear penetration was 0.031 ± 0.004 mm per year . No hips in either group displayed osteolysis . The Kaplan-Meier survivorship with revision as the end point at 12.4 years was 100 % ( 95 % confidence interval [ CI ] , 94–100 % ) for the femoral component in both groups and 99 % ( 95 % CI , 93–100 % ) for the acetabular component . Conclusion The clinical and radiographic results of using an alumina-on-alumina ceramic and alumina-on-highly cross-linked polyethylene bearings were similar The higher failure rate of total hip arthroplasty ( THA ) in young , active patients remains a challenge for surgeons . Recently , larger-diameter femoral heads combined with an alumina matrix composite ceramic ( BIOLOX Delta ; CeramTec AG , Plochingen , Germany ) articulation was developed to improve implant longevity and meet patients ' activity dem and s while reducing the risk of component-related complications . The purpose of this study was to determine whether this new device may provide advantages for young , active patients . A prospect i ve , r and omized , controlled trial was conducted on 93 patients ( 113 THAs ) with more than 3 years of follow-up . Patients were r and omly divided into a study group ( 51 THAs ) with a 36-mm Delta ceramic-on-ceramic ( COC ) articulation and a control group ( 62 THAs ) with a common-sized alumina ceramic head on polyethylene liner ( COP ) articulation .  Clinical and radiographic results were collected to compare the outcomes and complications , including implant-related failures , osteolysis , and noises . The large-diameter Delta COC articulation provided greater range of motion improvement ( 6.1 ° more ) , similar Harris Hip Scores , and similar complication rates compared with the alumina COP articulation . This study suggests that in the short term , the large-diameter Delta COC articulation results in better range of motion with no higher complication rates ; however , mid-term ( 8 - 10 years ) or longer follow-up is necessary to determine its superiority in young , active patients This study determined how ceramic-on-ceramic bearing THA affected joint-specific pain , function and stiffness in the first five postoperative years compared with ceramic-on-highly-crosslinked-polyethylene bearing THA .  Subjects less than 61 years of age were r and omized  to ceramic-on-ceramic ( CERAMIC ) [ n = 48 ] or ceramic-on-highly-crosslinked-polyethylene ( POLYETHYLENE ) [ n = 44 ] bearing THA . Subjects were assessed using the Western Ontario McMaster Osteoarthritis Index ( WOMAC ) and the R AND 12-Item Health Survey ( R AND -12 ) preoperatively , and at one and five years postoperatively . 92 subjects(50 ( 54 % ) males ; average age = 52 ( SD 6.6 ) years ) were enrolled . 78 ( 85 % ) subjects returned five years postoperatively . All subjects reported improvements at one and five years in all measured indices with no group differences detected . Seven ( 8 % ) subjects experienced postoperative THA complications , none related to bearing surfaces ; two subjects ( POLYETHYLENE ) required revision for instability . Both bearing surfaces provided excellent short-term results in younger subjects Background Polyethylene wear-induced osteolysis is a major cause of implant loosening in total hip arthroplasty . New crosslinked polyethylenes are presumed to give lower wear rates , but no long-term clinical results are available yet . Patients and methods We compared basic material characteristics and MTS hip joint simulator wear rates of a crosslinked polyethylene ( Duration ) to those of conventional polyethylene . In a r and omized double-blind 5-year clinical follow-up study , 133 hips ( 67 conventional , 66 Duration ) in 127 patients were followed-up for an average of 5 ( 3–6 ) years .  Wear rates were measured using a computer-based edge detection method . The radiographic appearances of wear-related phenomena were recorded . Results The Duration polyethylene showed a significantly lower in-vitro wear rate in the simulator study ( mean 22 ( SD 2.3 ) vs. 40 ( SD 1.5 ) mm3/106 cycles ) . Also , the in-vivo wear was lower for Duration ( mean 0.083 ( SD 
    Output:
    
agent
Conclusions Current published evidence does not support survivorship differences among commonly used bearing surfaces in patients younger than age 65 years undergoing THA at short- to mid-term followup .
***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: Highly cross-linked polyethylene was developed to reduce articular bearing wear in total hip arthroplasty . In vitro studies have shown reduced wear in comparison with conventional polyethylene . A double-blind , prospect i ve , r and omized trial was performed comparing highly cross-linked and conventional polyethylene  in 119 patients . The primary outcome variables were linear , 3-dimensional , and volumetric wear as determined by analysis of digitized radiographs using vali date d wear measurement software . Linear , 3-dimensional , and volumetric wear rates were significantly less in the highly cross-linked polyethylene group between 6 months and 4 years postoperatively ( P < .05 ) . The data presented here show that highly cross-linked polyethylene reduces short-term polyethylene wear . The intermediate and long-term clinical results of highly cross-linked polyethylene remain unknown pending further follow-up Mixed treatment comparison ( MTC ) meta- analysis is a generalization of st and ard pairwise meta- analysis for A vs B trials , to data structures that include , for example , A vs B , B vs C , and A vs C trials . There are two roles for MTC : one is to strengthen inference concerning the relative efficacy of two treatments , by including both ' direct ' and ' indirect ' comparisons . The other is to facilitate simultaneous inference regarding all treatments , in order for example to select the best treatment . In this paper , we present a range of Bayesian hierarchical models using the Markov chain Monte Carlo software WinBUGS . These are multivariate r and om effects models that allow for variation in true treatment effects across trials . We consider models where the between-trials variance is homogeneous across treatment comparisons as well as heterogeneous variance models . We also compare models with fixed ( unconstrained ) baseline study effects with models with r and om baselines drawn from a common distribution . These models are applied to an illustrative data set and posterior parameter distributions are compared . We discuss model critique and model selection , illustrating the role of Bayesian deviance analysis , and node-based model criticism . The assumptions underlying the MTC models and their parameterization are also discussed Ultra-high-molecular-weight polyethylene sterilised in the absence of air and highly cross-linked polyethylene have been used to avoid osteolysis and loosening in total hip replacement . Our prospect i ve r and omised study has assessed the results using two different polyethylenes associated with the same prosthetic design . We assessed 45 Allofit acetabular components with a Sulene-polyethylene liner of conventional polyethylene gamma sterilised with nitrogen and 45 Allofit acetabular components with a Durasul-polyethylene liner sterilised in ethylene oxide , both matched with an Alloclassic stem  with a 28 mm modular femoral head . The prostheses were implanted between May 1999 and December 2001 . The mean follow-up was for 66.3 months ( 60 to 92 ) . The linear penetration of the femoral head was estimated at 6 weeks , at 6 and 12 months and annually thereafter from st and ardised digitised radiographs using image- analysis software . There was no loosening of any prosthetic component . There were no radiolucent lines or osteolysis . The mean rate of penetration calculated from regression analysis during the first five years was 38 microm/year ( SD 2 ) for the Sulene group and 6 microm/year ( SD 1 ) for the Durasul group ( p = 0.00002 ) . The rate of penetration of the Durasul group was 15.7 % of that of the Sulene group Background Although hip arthroplasty reliably relieves pain and improves function , problems have arisen with wear and osteolysis .  Highly crosslinked polyethylene has been developed to address this problem although at present there is limited clinical evidence it does so longer term . Questions / purpose sWe compared the in vivo wear of st and ard versus highly crosslinked polyethylene ( HXLP ) in primary total hip arthroplasty at a minimum of 5-year followup . Methods We enrolled 122 patients in a prospect i ve , double-blinded , r and omized trial and followed them annually to assess their progress . Annual radiographs were analyzed using previously vali date d edge detection software to assess for two-dimensional , three-dimensional , and volumetric wear . The mean follow up was 5.5 years ( range , 4.1 to 7 years ) . Results The two-dimensional wear measurements for HXLP showed lower wear compared to the conventional group ( 0.05 mm/year versus 0.26 mm/year , respectively ) . Three-dimensional and volumetric wear were similarly lower in the HXLP group . Conclusions Highly crosslinked polyethylene undergoes substantially less wear than conventional polyethylene at medium term . The effect of hip arthroplasty longevity will need to be assessed with longer-term studies , but this may lead to a decreased need for revision as a result of less wear and osteolysis . Level of Evidence Level I , therapeutic study . See Guidelines for Authors for a complete description of levels of evidence Abstract Wear particle-induced osteolysis is a major cause of aseptic loosening in THA . Increasing wear resistance of polyethylene ( PE ) occurs by increasing the cross-link density and early reports document low wear rates with such implants . To confirm longer-term reductions in wear we compared cross-linked polyethylene ( irradiation in nitrogen , annealing ) with historical polyethylene ( irradiation in air ) in a prospect i ve , r and omized clinical study involving 48 patients who underwent THAs with a minimum followup of 7 years ( mean , 8 years ; range , 7–9 years ) . The insert material was the only variable . The Harris hip score , radiographic signs of osteolysis , and polyethylene wear were recorded annually . Twenty-three historical and 17 moderately cross-linked polyethylene inserts were analyzed ( five patients died , three were lost to followup ) . At 8 years , the wear rate was lower for cross-linked polyethylene ( 0.088 ± 0.03 mm/year ) than for the historical polyethylene ( 0.142 ± 0.07 mm/year ) . This reduction ( 38 % ) did not diminish with time ( 33 % at 5 years ) . Acetabular cyst formation was less frequent ( 39 % versus 12 % ) , affected fewer DeLee and Charnley zones ( 17 % versus 4 % ) , and was less severe for the cross-linked polyethylene . The only revision was for an aseptically loose cup in the historical polyethylene group . Moderately cross-linked polyethylene maintained its wear advantage with time and produced less osteolysis , showing no signs of aging at mid-term followup . Level of Evidence : Level I , therapeutic study . See Guidelines for Authors for a complete description of levels of evidence The results of a prospect i ve multicenter trial comparing 357 hips r and omized to total hip arthroplasty with either ceramic-ceramic or ceramic-polyethylene couplings  are presented . No statistically significant difference in clinical outcomes scores between the ceramic-ceramic and ceramic-polyethylene groups was observed at any time interval . The mean linear rate was statistically lower ( P < .001 ) in the ceramic-ceramic group ( 30.5 μm/year ) when compared with the ceramic-polyethylene group ( 218.2 μm/year ) . The rates of ceramic implant fracture ( 2.6 % ) and audible component-related noise ( 3.1 % ) were statistically higher in the ceramic-ceramic group when compared with the ceramic-polyethylene group ( P < .05 ) . Lastly , there was no statistically significant difference in the dislocation or revision rate between the groups at the time of last clinical follow-up Purpose Very few studies have compared alumina-on-alumina ceramic and alumina-on-highly cross-linked polyethylene bearings in the same patient . The purpose of this prospect i ve r and omised study was to compare the clinical and radiographic results and the prevalence of osteolysis in cementless total hip arthroplasty using an alumina-on-alumina and alumina-on-highly cross-linked polyethylene bearings in young active patients . Methods We prospect ively compared the results of 100 patients ( 200 hips ) who had undergone a cementless total hip arthroplasty with an alumina-on-alumina ceramic bearing in one hip and an alumina-on-highly cross-linked polyethylene in the other . There were 66 men and 34 women with a mean age of 45.3 years ( range , 21–49 years ) at the time of surgery . The mean follow-up was 12.4 years ( range , 11–13 years ) . The patients were assessed clinical ly and radiographically at three months , one year , and annually thereafter . Results Harris hip , Western Ontario and McMaster Universities Osteoarthritis Index , and University of California , Los Angeles activity scores did not show statistically significant differences between the two groups of bearings preoperatively or at the time of final follow-up . Radiographic findings of the component were not significantly different between the two groups . The mean polyethylene linear penetration was 0.031 ± 0.004 mm per year . No hips in either group displayed osteolysis . The Kaplan-Meier survivorship with revision as the end point at 12.4 years was 100 % ( 95 % confidence interval [ CI ] , 94–100 % ) for the femoral component in both groups and 99 % ( 95 % CI , 93–100 % ) for the acetabular component . Conclusion The clinical and radiographic results of using an alumina-on-alumina ceramic and alumina-on-highly cross-linked polyethylene bearings were similar The higher failure rate of total hip arthroplasty ( THA ) in young , active patients remains a challenge for surgeons . Recently , larger-diameter femoral heads combined with an alumina matrix composite ceramic ( BIOLOX Delta ; CeramTec AG , Plochingen , Germany ) articulation was developed to improve implant longevity and meet patients ' activity dem and s while reducing the risk of component-related complications . The purpose of this study was to determine whether this new device may provide advantages for young , active patients . A prospect i ve , r and omized , controlled trial was conducted on 93 patients ( 113 THAs ) with more than 3 years of follow-up . Patients were r and omly divided into a study group ( 51 THAs ) with a 36-mm Delta ceramic-on-ceramic ( COC ) articulation and a control group ( 62 THAs ) with a common-sized alumina ceramic head on polyethylene liner ( COP ) articulation .  Clinical and radiographic results were collected to compare the outcomes and complications , including implant-related failures , osteolysis , and noises . The large-diameter Delta COC articulation provided greater range of motion improvement ( 6.1 ° more ) , similar Harris Hip Scores , and similar complication rates compared with the alumina COP articulation . This study suggests that in the short term , the large-diameter Delta COC articulation results in better range of motion with no higher complication rates ; however , mid-term ( 8 - 10 years ) or longer follow-up is necessary to determine its superiority in young , active patients This study determined how ceramic-on-ceramic bearing THA affected joint-specific pain , function and stiffness in the first five postoperative years compared with ceramic-on-highly-crosslinked-polyethylene bearing THA .  Subjects less than 61 years of age were r and omized  to ceramic-on-ceramic ( CERAMIC ) [ n = 48 ] or ceramic-on-highly-crosslinked-polyethylene ( POLYETHYLENE ) [ n = 44 ] bearing THA . Subjects were assessed using the Western Ontario McMaster Osteoarthritis Index ( WOMAC ) and the R AND 12-Item Health Survey ( R AND -12 ) preoperatively , and at one and five years postoperatively . 92 subjects(50 ( 54 % ) males ; average age = 52 ( SD 6.6 ) years ) were enrolled . 78 ( 85 % ) subjects returned five years postoperatively . All subjects reported improvements at one and five years in all measured indices with no group differences detected . Seven ( 8 % ) subjects experienced postoperative THA complications , none related to bearing surfaces ; two subjects ( POLYETHYLENE ) required revision for instability . Both bearing surfaces provided excellent short-term results in younger subjects Background Polyethylene wear-induced osteolysis is a major cause of implant loosening in total hip arthroplasty . New crosslinked polyethylenes are presumed to give lower wear rates , but no long-term clinical results are available yet . Patients and methods We compared basic material characteristics and MTS hip joint simulator wear rates of a crosslinked polyethylene ( Duration ) to those of conventional polyethylene . In a r and omized double-blind 5-year clinical follow-up study , 133 hips ( 67 conventional , 66 Duration ) in 127 patients were followed-up for an average of 5 ( 3–6 ) years .  Wear rates were measured using a computer-based edge detection method . The radiographic appearances of wear-related phenomena were recorded . Results The Duration polyethylene showed a significantly lower in-vitro wear rate in the simulator study ( mean 22 ( SD 2.3 ) vs. 40 ( SD 1.5 ) mm3/106 cycles ) . Also , the in-vivo wear was lower for Duration ( mean 0.083 ( SD 
    Output:
    