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: Flaws in the design , conduct , analysis , and reporting of r and omised trials can cause the effect of an intervention to be underestimated or overestimated . The Cochrane Collaboration ’s tool for assessing risk of bias aims to make the process clearer and more Background and purpose Femoral deformity associated with osteoarthritis is a challenge for both the surgeon and the implant . Many of the patients with these deformities are young . St and ard implants can be difficult to fit into these femurs . We prospect ively evaluated the outcome of custom uncemented femoral stems in young patients . Methods 61 consecutive patients ( 72 hips ) underwent surgery for osteoarthritis because of femoral deformity at a mean age of 35 ( 22–40 ) years . The patients received a CT3D-A custom-made femoral stem and an uncemented cup . The mean follow-up time was 14 ( 10–16 ) years . 2 patients died at 7 and 8 years after surgery , otherwise , none of the patients were lost to follow-up . Results At follow-up , the femoral prosthesis had not been revised in 59 patients ( 70 hips ) . 3 patients ( 3 hips ) had required revision surgery due to loosening of the acetabular component ; 2 hips were awaiting revision surgery for loosening of the acetabular cup . There were no cases of dislocation or infection . At review , all stems were considered stable according to the radiographic criteria . No migration or subsidence was observed on plain radiographs . Interpretation Our results are comparable to published results of custom stems regarding survival and outcome . Considering the young age and the deformities in this series of uncemented custom femoral stems , and the fact that there was follow-up of up to 16 years , the survival is remarkable . This technique appears to be a reasonable alternative in younger patients with femoral deformities Background The use of highly crosslinked polyethylene ( HXLPE ) is now commonplace for total hip arthroplasty . Hip simulator studies and short-term in vivo measurements suggest that the wear rate of some types of HXLPE is significantly less than conventional ultrahigh-molecular-weight polyethylene ( UHMWPE ) . However , there are few long-term data to support its use . Questions / purpose sThe aim of this study was to measure the long-term steady-state wear of HXLPE compared with UHMWPE liners in a prospect i ve , double-blind , r and omized controlled trial using radiostereometric analysis . Methods Fifty-four patients were r and omized to receive hip arthroplasties with either UHMWPE liners or HXLPE liners .  Complete followup was available on 39 of these patients ( 72 % ) . All patients received the same cemented stem and an uncemented acetabular component . Three-dimensional penetration of the head into the socket was determined at 10 years using a radiostereometric analysis system , which has an in vivo accuracy of < 0.1 mm . Oxford Hip Scores were compared between the groups . Results At 10 years there was significantly less wear of HXLPE ( 0.003 mm/year ; 95 % confidence interval [ CI ] , ± 0.010 ; SD 0.023 ; range , −0.057 to 0.074 ) compared with UHMWPE ( 0.030 mm/year ; 95 % CI , ± 0.012 ; p < 0.001 ; SD 0.0.27 ; range , −0.001 to 0.164 ) . The volumetric penetration from 1 to 10 years for the UHMWPE group was 98 mm3 ( 95 % CI , ± 46 mm3 ; SD 102 mm3 ; range , −4 to 430 mm3 ) compared with 14 mm3 ( 95 % CI , ± 40 mm3 ; SD 91 mm3 ; range , −189 to 242 mm3 ) for the HXLPE group ( p = 0.01 ) . Conclusions This study demonstrates that HXLPE has little detectable steady-state in vivo wear . This may result in fewer reoperations from loosening ; however , careful clinical followup into the second decade still needs to be performed . Level of Evidence Level I , therapeutic study . See the Guidelines for Authors for a complete description of levels of evidence Background Anatomic short femoral prostheses with a prominent lateral flare have the potential to reduce stress-shielding in the femur through a more physiological stress distribution to the proximal femur . We present the design rationale of a new short uncemented , proximally fixed anatomic femoral implant and the study design of a prospect i ve multi-centre trial to collect long-term patient outcome and radiographic follow up data . Methods A prospect i ve surveillance study ( trial registry NCT00208555 ) in four European centres ( UK , Italy , Spain and Germany ) with a follow up period of 15 years will be executed . The recruitment target is 200 subjects , patients between the ages of 18 and 70 admitted for primary cementless unilateral THA will be included . The primary objective is to evaluate the five-year survivorship of the new cementless short stem .  The secondary objectives of this investigation are to evaluate the long term survivorship and the clinical performance of the implant , the impact on the subjects health related Quality of Life and the affect of the prosthesis on bone mineral density . Peri- and postoperative complications will be registered . Clinical and radiographic evaluation of prosthesis positioning will be done post-operatively and at 3 , 6 , 12 , 24 , 60 , 120 and 180 months follow up . Discussion Shortening of the distal stem can maximise bone and soft tissue conservation . New stem types have been design ed to improve the limitations of traditional implants in primary THA . A new , uncemented femoral short stem is introduced in this paper . A long-term follow up study has been design ed to verify stable fixation and to research into the clinical outcome . The results of this trial will be presented as soon as they become available There have been comparatively few studies of the incidence of osteolysis and the survival of hybrid and cementless total hip replacements ( THRs ) in patients younger than 50 years of age . We prospect ively review ed 78 patients ( 109 hips ) with a hybrid THR having a mean age of 43.4 years ( 21 to 50 ) and 79 patients ( 110 hips ) with a cementless THR with a mean age of 46.8 years ( 21 to 49 ) . The patients were evaluated clinical ly using the Harris hip score , the Western Ontario and McMaster Universities ( WOMAC ) osteoarthritis score and the University of California , Los Angeles ( UCLA ) activity score .  Radiographs and CT scans were assessed for loosening and osteolysis . The mean follow-up was for 18.4 years ( 16 to 19 ) in both groups . The mean post-operative Harris hip scores ( 91 points versus 90 points ) , the mean WOMAC scores ( 11 points versus 13 points ) and UCLA activity scores ( 6.9 points versus 7.1 points ) were similar in both groups . The revision rates of the acetabular component ( 13 % versus 16 % ) and the femoral component ( 3 % versus 4 % ) , and the survival of the acetabular component ( 87 % versus 84 % ) and the femoral component ( 97 % versus 96 % ) were similar in both groups . Although the long-term fixation of the acetabular metallic shell and the cemented and cementless femoral components was outst and ing , wear and peri-acetabular osteolysis constitute the major challenges of THR in young patients Background Because the clinical and radiographic performance of an ultrashort anatomic cementless stem has been investigated in only two r and omized controlled studies , well- design ed trials should aim for a thorough comparison of the outcomes of ultrashort anatomic cementless and conventional anatomic cementless stems . Questions / purpose sThe purpose s of this study were to compare ( 1 ) the clinical results , including Harris hip score , thigh pain , and WOMAC index score , ( 2 ) radiographic results , ( 3 ) bone mineral density ; and ( 4 ) proportions of patients undergoing revision of a THA using an ultrashort anatomic cementless stem versus a conventional anatomic cementless stem  in the same patients who underwent bilateral sequential THAs under the same anesthetic . Methods Two hundred patients ( mean age , 53 years ; range , 26–54 years ) who underwent bilateral sequential THAs received an ultrashort anatomic cementless stem in one hip and a conventional anatomic cementless stem in the contralateral hip . From January 2004 to December 2005 , we performed 524 same-day bilateral short and conventional anatomic cementless THAs  in 262 patients , of whom 212 ( 81 % ) participated in this study . Five patients were lost to followup before 2 years , five were lost between 2 to 10 years , and two were lost between 10 to 13 years , leaving 200 patients . Patients who had end-stage bilateral hip disease and were younger than 55 years were selected for inclusion . The predominant diagnoses were osteonecrosis ( 118 patients , 59 % ) and osteoarthritis ( 44 patients , 22 % ) . One hundred thirty-eight were men and 62 were women . At the time of each followup , the patients were assessed clinical ly and radiographically . In addition , each patient completed the WOMAC and the University of California Los Angeles ( UCLA ) activity scores . The minimum followup was 10 years ( mean , 11.8 years ; range , 10–13 years ) . Followups were done in person , with all images and followup clinic notes . Based on the power analysis , we estimated a sample size of 178 hips was needed in each group to detect a 3-point difference in the Harris hip score with 80 % power . Results At the latest followup , there were no differences between the two groups regarding the mean Harris hip scores ( 94 versus 94 points ; p = 0.189 ) , mean WOMAC scores ( 17 versus 16 points ; p = 0.191 ) , or mean UCLA activity scores ( 9 versus 9 points ; p = 0.381 ) . Two patients in the ultrashort stem group and one patient in the conventional stem group had severe ( 9 points ) thigh pain , and 30 patients ( 15 % ) in the conventional stem group had mild thigh pain ( 2 or 3 points ) after vigorous exercise . Bone mineral density in the ultrashort and conventional stem groups , respectively , was greater in the ultrashort stem group than in the conventional stem group . Bone mineral density in Zone 1 at 12 years was 3.29 versus 1.88 g/cm2 ( p = 0.021 ) , and 2.97 versus 0.91 g/m2 in Zone 7 ( p = 0.001 ) . With the numbers available , there were no differences between the stem design s in terms of the proportion undergoing revision ( one hip , 0.5 % , in the short-stem group versus one hip , 0.5 % , in the conventional group ; p = 1.881 ) . Conclusions At followup into the second decade , ultrashort stems showed no differences from conventional cementless stems in terms of vali date d outcomes scores or fixation , although less stress shielding was observed . Reduction of stress shielding may reduce the long-term risk of periprosthetic fracture , but this was not shown in our study .Level of Evidence Level I , therapeutic study We investigated the efficacy of combining highly cross-linked polyethylene with ceramic heads on further reduction in polyethylene wear compared with the combination with cobalt-chromium heads via PolyWare computer-assisted method . A prospect i ve cohort study was performed on 102 cementless total hip arthroplasties using Longevity ( Zimmer , Warsaw , Ind ) highly cross-linked polyethylene liners . Either  26-mm zirconia heads or 26-mm cobalt-chromium heads were r and omly used in 51 hips each . At a mean follow-up of 6.7 years , no significant differences were identified between the groups for total penetration rate and steady-state wear rate . Osteolysis was not observed in any hips in either group . In conclusion , no advantage was seen for the 26-mm zirconia head compared with the 26-mm cobalt-chromium head in this period Background The number of total hip arthroplasties in patients under 30 years is increasing over the years . Almost all of them will face at least one or more future revisions in their life . Therefore , the implant used should have a high survival rate , and needs to be easily revisable result ing in a low re-revision rate . Several studies have evaluated the outcome of total hip arthroplasties in patients under 30 years . However , only a few reported on the follow-up outcome of 10 years or more . In addition , none of these reports published data of the subsequent revisions of these implants within their original report . Methods We studied historically prospect i ve collected data of 48 consecutive patients ( 69 hips ) younger than 30 years , treated with a cemented primary total hip prosthesis between 1988 and 2004 . Since the last evaluation of this cohort , two patients were lost to follow-up . For all hip revisions in this cohort , again cemented implants were used , mostly in combination with bone impaction grafting .  Kaplan-Meier survival curves at 10- and 15 years for the primary total hip arthroplasties and revisions were determined . Results The mean age at time of primary surgery was 25 years ( range , 16 to 29 
    Output:
    
agent
Conclusion Total hip arthroplasty in patients younger than 55 years provides reliable outcomes at up to 10 years .
***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: Flaws in the design , conduct , analysis , and reporting of r and omised trials can cause the effect of an intervention to be underestimated or overestimated . The Cochrane Collaboration ’s tool for assessing risk of bias aims to make the process clearer and more Background and purpose Femoral deformity associated with osteoarthritis is a challenge for both the surgeon and the implant . Many of the patients with these deformities are young . St and ard implants can be difficult to fit into these femurs . We prospect ively evaluated the outcome of custom uncemented femoral stems in young patients . Methods 61 consecutive patients ( 72 hips ) underwent surgery for osteoarthritis because of femoral deformity at a mean age of 35 ( 22–40 ) years . The patients received a CT3D-A custom-made femoral stem and an uncemented cup . The mean follow-up time was 14 ( 10–16 ) years . 2 patients died at 7 and 8 years after surgery , otherwise , none of the patients were lost to follow-up . Results At follow-up , the femoral prosthesis had not been revised in 59 patients ( 70 hips ) . 3 patients ( 3 hips ) had required revision surgery due to loosening of the acetabular component ; 2 hips were awaiting revision surgery for loosening of the acetabular cup . There were no cases of dislocation or infection . At review , all stems were considered stable according to the radiographic criteria . No migration or subsidence was observed on plain radiographs . Interpretation Our results are comparable to published results of custom stems regarding survival and outcome . Considering the young age and the deformities in this series of uncemented custom femoral stems , and the fact that there was follow-up of up to 16 years , the survival is remarkable . This technique appears to be a reasonable alternative in younger patients with femoral deformities Background The use of highly crosslinked polyethylene ( HXLPE ) is now commonplace for total hip arthroplasty . Hip simulator studies and short-term in vivo measurements suggest that the wear rate of some types of HXLPE is significantly less than conventional ultrahigh-molecular-weight polyethylene ( UHMWPE ) . However , there are few long-term data to support its use . Questions / purpose sThe aim of this study was to measure the long-term steady-state wear of HXLPE compared with UHMWPE liners in a prospect i ve , double-blind , r and omized controlled trial using radiostereometric analysis . Methods Fifty-four patients were r and omized to receive hip arthroplasties with either UHMWPE liners or HXLPE liners .  Complete followup was available on 39 of these patients ( 72 % ) . All patients received the same cemented stem and an uncemented acetabular component . Three-dimensional penetration of the head into the socket was determined at 10 years using a radiostereometric analysis system , which has an in vivo accuracy of < 0.1 mm . Oxford Hip Scores were compared between the groups . Results At 10 years there was significantly less wear of HXLPE ( 0.003 mm/year ; 95 % confidence interval [ CI ] , ± 0.010 ; SD 0.023 ; range , −0.057 to 0.074 ) compared with UHMWPE ( 0.030 mm/year ; 95 % CI , ± 0.012 ; p < 0.001 ; SD 0.0.27 ; range , −0.001 to 0.164 ) . The volumetric penetration from 1 to 10 years for the UHMWPE group was 98 mm3 ( 95 % CI , ± 46 mm3 ; SD 102 mm3 ; range , −4 to 430 mm3 ) compared with 14 mm3 ( 95 % CI , ± 40 mm3 ; SD 91 mm3 ; range , −189 to 242 mm3 ) for the HXLPE group ( p = 0.01 ) . Conclusions This study demonstrates that HXLPE has little detectable steady-state in vivo wear . This may result in fewer reoperations from loosening ; however , careful clinical followup into the second decade still needs to be performed . Level of Evidence Level I , therapeutic study . See the Guidelines for Authors for a complete description of levels of evidence Background Anatomic short femoral prostheses with a prominent lateral flare have the potential to reduce stress-shielding in the femur through a more physiological stress distribution to the proximal femur . We present the design rationale of a new short uncemented , proximally fixed anatomic femoral implant and the study design of a prospect i ve multi-centre trial to collect long-term patient outcome and radiographic follow up data . Methods A prospect i ve surveillance study ( trial registry NCT00208555 ) in four European centres ( UK , Italy , Spain and Germany ) with a follow up period of 15 years will be executed . The recruitment target is 200 subjects , patients between the ages of 18 and 70 admitted for primary cementless unilateral THA will be included . The primary objective is to evaluate the five-year survivorship of the new cementless short stem .  The secondary objectives of this investigation are to evaluate the long term survivorship and the clinical performance of the implant , the impact on the subjects health related Quality of Life and the affect of the prosthesis on bone mineral density . Peri- and postoperative complications will be registered . Clinical and radiographic evaluation of prosthesis positioning will be done post-operatively and at 3 , 6 , 12 , 24 , 60 , 120 and 180 months follow up . Discussion Shortening of the distal stem can maximise bone and soft tissue conservation . New stem types have been design ed to improve the limitations of traditional implants in primary THA . A new , uncemented femoral short stem is introduced in this paper . A long-term follow up study has been design ed to verify stable fixation and to research into the clinical outcome . The results of this trial will be presented as soon as they become available There have been comparatively few studies of the incidence of osteolysis and the survival of hybrid and cementless total hip replacements ( THRs ) in patients younger than 50 years of age . We prospect ively review ed 78 patients ( 109 hips ) with a hybrid THR having a mean age of 43.4 years ( 21 to 50 ) and 79 patients ( 110 hips ) with a cementless THR with a mean age of 46.8 years ( 21 to 49 ) . The patients were evaluated clinical ly using the Harris hip score , the Western Ontario and McMaster Universities ( WOMAC ) osteoarthritis score and the University of California , Los Angeles ( UCLA ) activity score .  Radiographs and CT scans were assessed for loosening and osteolysis . The mean follow-up was for 18.4 years ( 16 to 19 ) in both groups . The mean post-operative Harris hip scores ( 91 points versus 90 points ) , the mean WOMAC scores ( 11 points versus 13 points ) and UCLA activity scores ( 6.9 points versus 7.1 points ) were similar in both groups . The revision rates of the acetabular component ( 13 % versus 16 % ) and the femoral component ( 3 % versus 4 % ) , and the survival of the acetabular component ( 87 % versus 84 % ) and the femoral component ( 97 % versus 96 % ) were similar in both groups . Although the long-term fixation of the acetabular metallic shell and the cemented and cementless femoral components was outst and ing , wear and peri-acetabular osteolysis constitute the major challenges of THR in young patients Background Because the clinical and radiographic performance of an ultrashort anatomic cementless stem has been investigated in only two r and omized controlled studies , well- design ed trials should aim for a thorough comparison of the outcomes of ultrashort anatomic cementless and conventional anatomic cementless stems . Questions / purpose sThe purpose s of this study were to compare ( 1 ) the clinical results , including Harris hip score , thigh pain , and WOMAC index score , ( 2 ) radiographic results , ( 3 ) bone mineral density ; and ( 4 ) proportions of patients undergoing revision of a THA using an ultrashort anatomic cementless stem versus a conventional anatomic cementless stem  in the same patients who underwent bilateral sequential THAs under the same anesthetic . Methods Two hundred patients ( mean age , 53 years ; range , 26–54 years ) who underwent bilateral sequential THAs received an ultrashort anatomic cementless stem in one hip and a conventional anatomic cementless stem in the contralateral hip . From January 2004 to December 2005 , we performed 524 same-day bilateral short and conventional anatomic cementless THAs  in 262 patients , of whom 212 ( 81 % ) participated in this study . Five patients were lost to followup before 2 years , five were lost between 2 to 10 years , and two were lost between 10 to 13 years , leaving 200 patients . Patients who had end-stage bilateral hip disease and were younger than 55 years were selected for inclusion . The predominant diagnoses were osteonecrosis ( 118 patients , 59 % ) and osteoarthritis ( 44 patients , 22 % ) . One hundred thirty-eight were men and 62 were women . At the time of each followup , the patients were assessed clinical ly and radiographically . In addition , each patient completed the WOMAC and the University of California Los Angeles ( UCLA ) activity scores . The minimum followup was 10 years ( mean , 11.8 years ; range , 10–13 years ) . Followups were done in person , with all images and followup clinic notes . Based on the power analysis , we estimated a sample size of 178 hips was needed in each group to detect a 3-point difference in the Harris hip score with 80 % power . Results At the latest followup , there were no differences between the two groups regarding the mean Harris hip scores ( 94 versus 94 points ; p = 0.189 ) , mean WOMAC scores ( 17 versus 16 points ; p = 0.191 ) , or mean UCLA activity scores ( 9 versus 9 points ; p = 0.381 ) . Two patients in the ultrashort stem group and one patient in the conventional stem group had severe ( 9 points ) thigh pain , and 30 patients ( 15 % ) in the conventional stem group had mild thigh pain ( 2 or 3 points ) after vigorous exercise . Bone mineral density in the ultrashort and conventional stem groups , respectively , was greater in the ultrashort stem group than in the conventional stem group . Bone mineral density in Zone 1 at 12 years was 3.29 versus 1.88 g/cm2 ( p = 0.021 ) , and 2.97 versus 0.91 g/m2 in Zone 7 ( p = 0.001 ) . With the numbers available , there were no differences between the stem design s in terms of the proportion undergoing revision ( one hip , 0.5 % , in the short-stem group versus one hip , 0.5 % , in the conventional group ; p = 1.881 ) . Conclusions At followup into the second decade , ultrashort stems showed no differences from conventional cementless stems in terms of vali date d outcomes scores or fixation , although less stress shielding was observed . Reduction of stress shielding may reduce the long-term risk of periprosthetic fracture , but this was not shown in our study .Level of Evidence Level I , therapeutic study We investigated the efficacy of combining highly cross-linked polyethylene with ceramic heads on further reduction in polyethylene wear compared with the combination with cobalt-chromium heads via PolyWare computer-assisted method . A prospect i ve cohort study was performed on 102 cementless total hip arthroplasties using Longevity ( Zimmer , Warsaw , Ind ) highly cross-linked polyethylene liners . Either  26-mm zirconia heads or 26-mm cobalt-chromium heads were r and omly used in 51 hips each . At a mean follow-up of 6.7 years , no significant differences were identified between the groups for total penetration rate and steady-state wear rate . Osteolysis was not observed in any hips in either group . In conclusion , no advantage was seen for the 26-mm zirconia head compared with the 26-mm cobalt-chromium head in this period Background The number of total hip arthroplasties in patients under 30 years is increasing over the years . Almost all of them will face at least one or more future revisions in their life . Therefore , the implant used should have a high survival rate , and needs to be easily revisable result ing in a low re-revision rate . Several studies have evaluated the outcome of total hip arthroplasties in patients under 30 years . However , only a few reported on the follow-up outcome of 10 years or more . In addition , none of these reports published data of the subsequent revisions of these implants within their original report . Methods We studied historically prospect i ve collected data of 48 consecutive patients ( 69 hips ) younger than 30 years , treated with a cemented primary total hip prosthesis between 1988 and 2004 . Since the last evaluation of this cohort , two patients were lost to follow-up . For all hip revisions in this cohort , again cemented implants were used , mostly in combination with bone impaction grafting .  Kaplan-Meier survival curves at 10- and 15 years for the primary total hip arthroplasties and revisions were determined . Results The mean age at time of primary surgery was 25 years ( range , 16 to 29 
    Output:
    