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 This prospect i ve r and omized study aims to compare the outcome between an alumina ceramic-on-ceramic ( CC ) articulation with a ceramic on ultra-high-molecular-weight polyethylene articulation ( CP ) .  Fifty-six hips in 55 patients with mean age 42.2 ( range , 19 - 56 ) each received uncemented components , a 28-mm alumina head with r and omization of acetabular liner .  Mean St Michael 's outcome score for each group with up to 10 years follow-up ( median , 8 years ; range , 1 - 10 ) was 22.8 and 22.9 , respectively ( P = .819 ) . Wear was identified in all but 1 CP replacement , but only 12 of the 23 CC . Mean wear in the CP group was 0.11 mm/y and 0.02 mm/yr in the CC group ( P < .001 ) . Other than significantly greater wear in the polyethylene group , there was no significant difference in midterm outcome between the 2 groups Wear and osteolysis continue to be major reasons for revision surgery in THA .  Ceramic-on-ceramic bearings eliminate polyethylene wear debris . The newest generation of these bearings incorporate nanosized , yttria-stabilized tetragonal zirconia particles producing an alumina matrix composite . We asked whether this new material would perform as well as a conventional bearing in terms of functional hip scores , radiographic migration and osteolysis , complications and survival . As part of a US FDA investigational device exemption study ( G000075 ) , we conducted an initial prospect i ve safety study of 21 alumina matrix composite femoral heads articulating on alumina liners followed by a prospect i ve , r and omized study with 44 more of these articulations and 45 zirconia femoral heads on polyethylene liners .  The minimum followup for all patients was 26 months ( mean , 73 months ; range , 26–108 months ) . Harris hip scores and radiographic findings were similar in the two groups as was survivorship ( trial 95 % versus control 93 % ) . There were three reoperations in the trial group and three in the control group . A fractured head retrieval showed a 33 % monoclinic transformation with an increase in surface roughness from 3 to 5 nm at the main wear zone . While our numbers were insufficient to compare device-related complications , the trial device performed as well as the control device in terms of reoperation , and clinical and radiographic outcome . The alumina matrix composite femoral head on an alumina liner provided high survivorship . Level of Evidence : Level II , therapeutic study . See Guidelines for Authors for a complete description of levels of evidence 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 We carried out a prospect i ve r and omised study design ed to compare the penetration rate of acetabular polyethylene inserts of identical design but different levels of cross-linking at a minimum of four years follow-up . A total of 102 patients ( 102 hips ) were r and omised to receive either highly cross-linked Durasul , or contemporary Sulene polyethylene inserts at total hip replacement .  A single blinded observer used the Martell system to assess penetration of the femoral head . At a mean follow-up of 4.9 years ( 4.2 to 6.1 ) the mean femoral head penetration rate was 0.025 mm/year ( SD 0.128 ) in the Durasul group compared with 0.106 mm/year ( SD 0.109 ) in the Sulene group ( Mann-Whitney test , p = 0.0027 ) . The mean volumetric penetration rate was 29.24 mm(3)/year ( SD 44.08 ) in the Durasul group compared with 53.32 mm(3)/year ( SD 48.68 ) in the Sulene group . The yearly volumetric penetration rate was 55 % lower in the Durasul group ( Mann-Whitney test , p = 0.0058 ) . Longer term results are needed to investigate whether less osteolysis will occur 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 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 % ( 
    Output:
    
agent
The present evidence indicated the similar performance in survivorship among CoC , CoPc , CoPxl and MoPxl bearing implants , and that all likely have superiority compared with the MoM and MoPc bearing implants in THA procedures .
***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 This prospect i ve r and omized study aims to compare the outcome between an alumina ceramic-on-ceramic ( CC ) articulation with a ceramic on ultra-high-molecular-weight polyethylene articulation ( CP ) .  Fifty-six hips in 55 patients with mean age 42.2 ( range , 19 - 56 ) each received uncemented components , a 28-mm alumina head with r and omization of acetabular liner .  Mean St Michael 's outcome score for each group with up to 10 years follow-up ( median , 8 years ; range , 1 - 10 ) was 22.8 and 22.9 , respectively ( P = .819 ) . Wear was identified in all but 1 CP replacement , but only 12 of the 23 CC . Mean wear in the CP group was 0.11 mm/y and 0.02 mm/yr in the CC group ( P < .001 ) . Other than significantly greater wear in the polyethylene group , there was no significant difference in midterm outcome between the 2 groups Wear and osteolysis continue to be major reasons for revision surgery in THA .  Ceramic-on-ceramic bearings eliminate polyethylene wear debris . The newest generation of these bearings incorporate nanosized , yttria-stabilized tetragonal zirconia particles producing an alumina matrix composite . We asked whether this new material would perform as well as a conventional bearing in terms of functional hip scores , radiographic migration and osteolysis , complications and survival . As part of a US FDA investigational device exemption study ( G000075 ) , we conducted an initial prospect i ve safety study of 21 alumina matrix composite femoral heads articulating on alumina liners followed by a prospect i ve , r and omized study with 44 more of these articulations and 45 zirconia femoral heads on polyethylene liners .  The minimum followup for all patients was 26 months ( mean , 73 months ; range , 26–108 months ) . Harris hip scores and radiographic findings were similar in the two groups as was survivorship ( trial 95 % versus control 93 % ) . There were three reoperations in the trial group and three in the control group . A fractured head retrieval showed a 33 % monoclinic transformation with an increase in surface roughness from 3 to 5 nm at the main wear zone . While our numbers were insufficient to compare device-related complications , the trial device performed as well as the control device in terms of reoperation , and clinical and radiographic outcome . The alumina matrix composite femoral head on an alumina liner provided high survivorship . Level of Evidence : Level II , therapeutic study . See Guidelines for Authors for a complete description of levels of evidence 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 We carried out a prospect i ve r and omised study design ed to compare the penetration rate of acetabular polyethylene inserts of identical design but different levels of cross-linking at a minimum of four years follow-up . A total of 102 patients ( 102 hips ) were r and omised to receive either highly cross-linked Durasul , or contemporary Sulene polyethylene inserts at total hip replacement .  A single blinded observer used the Martell system to assess penetration of the femoral head . At a mean follow-up of 4.9 years ( 4.2 to 6.1 ) the mean femoral head penetration rate was 0.025 mm/year ( SD 0.128 ) in the Durasul group compared with 0.106 mm/year ( SD 0.109 ) in the Sulene group ( Mann-Whitney test , p = 0.0027 ) . The mean volumetric penetration rate was 29.24 mm(3)/year ( SD 44.08 ) in the Durasul group compared with 53.32 mm(3)/year ( SD 48.68 ) in the Sulene group . The yearly volumetric penetration rate was 55 % lower in the Durasul group ( Mann-Whitney test , p = 0.0058 ) . Longer term results are needed to investigate whether less osteolysis will occur 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 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 % ( 
    Output:
    