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: Purpose Bone loss around uncemented femoral components is suspected to precede implant loosening and contribute to problems in revision surgery .  Short-stemmed cementless femoral components are design ed to preserve proximal femoral bone stock and ultimately the longevity of the prosthesis . Methods With quantitative computed tomography-assisted osteodensitometry , we prospect ively analyzed femoral cortical and cancellous bone density ( BD ) and contact area changes of an uncemented collum femoris preserving stem ( n = 38 ) 10 days , 1 , 3 and 7 years post-operatively . Results Seven years post-operatively  , cancellous BD ( mg CaHA/mL ) had decreased by as much as −66 % and cortical BD by up to −27 % at the metaphyseal portion of the femur ; the decrease was progressive between the 1- and 3-year examinations and halted thereafter . Contact area ( in % out of a possible 100 % ) decreased proximally between the 1- and 3-year follow-up . Conclusion Proximal cortical and cancellous bone density loss and decrease of contact area indicate that metaphyseal fixation can not be achieved . The lack of cortical BD loss and increase of contact area values below the trochanter minor suggest diaphyseal fixation Purpose On the basis of positive clinical results with mid- and long-term follow-up using the Mayo short stem , the Metha neck-preserving stem ( BBraun , Aesculap , Tuttlingen , Germany ) was introduced . The purpose of this study was to vali date the implant design by direct acquisition of bone remodelling data from total hip arthroplasty ( THA ) recipients using dual-energy X-ray absorptiometry ( DEXA ) . Methods After power analysis , 25 patients were included in this prospect i ve study . Patients were examined clinical ly and underwent DEXA examinations preoperatively and postoperatively at one week , six months and one and two years after THA . Gruen zones were adapted to the short stem design ( R1–R7 ) . Results The Harris Hip Score ( HHS ) increased significantly by 31 points . No stem had to be revised . Bone mineral density ( BMD ) in the greater trochanter decreased significantly from 0.78 g/cm2 postoperatively to 0.72 g/cm2 two years after surgery . Marginal changes were seen in the lateral distal regions ( R4–R5 ) . In the minor trochanter region , BMD increased significantly after two years by 12.9 % . In the calcar region , BMD exceeded the baseline value by 6.1 % two years after implantation . Conclusions Stress shielding seems to occur at the greater trochanter due to the vast cross-section of the implant . However , the aim of proximal load transfer of the Metha stem seems to be partially achieved . DEXA analysis revealed a concentrated load distribution on the medial portion of the femur , which is an important region to guarantee long-term implant survival Aim Tissue sparing hip prostheses are becoming more and more popular especially for the treatment of younger patients . The objective of this study was to evaluate the clinical and radiological results after insertion of a tissue sparing hip prosthesis . Method In 47 consecutive non-selected patients ( 50 hips ) , the clinical and radiographic results of cementless total hip arthroplasty using a collum femoris preserving stem , a pressfit cup and an alumina – polyethylene pairing were prospect ively evaluated . The mean age at index-surgery was 58 ( 36–82 ) years , there were 38 women and 9 men . After a mean follow-up of 6.8 years ( minimum 6.1 years ) , two patients had died and one patient underwent revision surgery due to aseptic loosening of the stem . Results The overall survival rate of the acetabular component was 100 % and of the femoral component 98 % . The mean Harris hip score at follow-up was 94 points . Conclusion The mid-term survival with this type of total hip arthroplasty is excellent and compares equal with uncemented straight stems in this age group The CFP stem represents a short collared neck-retaining stem with very proximal metaphyseal anchoring along the calcar combined with up-to- date metallurgy . Despite theoretical advantages , the stability and clinical outcome are unknown . We prospect ively measured the migration pattern of this new stem and cup . Twenty-six patients ( 26 hips ) with a mean age of 54 years ( range , 40 - 66 years ) underwent THA  and were followed for 2 years with  radiostereometry , radiographs , and clinical scores . The stem showed some early retroversion ( mean , SEM 0.6 ° , 0.3 ) , but stabilized before 1 year . Subsidence ( 0.05 mm , 0.06 ) and varus-valgus tilting ( 0.03 ° , 0.01 ) were low . We observed no bone loss in the calcar region . Factors related to patients , implant design , and implantation did not predict migration patterns . The two-dimensional wear of the ceramic/conventional articulation was 0.09 mm at 2 - 24 months . The low migration of this short neck preserving stem suggests a favorable long-term outcome but longer followup is needed to substantiate this prediction . This design might become an alternative to st and ard stems and hip resurfacing . Level of Evidence : Therapeutic Level IV . See The Guidelines for Authors for a complete description of levels of evidence This prospect i ve study reports the clinical and radiological results of a single-surgeon series using the Mayo conservative hip stem in a district hospital . 30 total hip arthroplasties were performed in 26 physically active patients . There were 18 women and 8 men , with a mean age of 57.4 years ( range 36–79 ) . 4 cases were bilateral . The operation was performed for severe primary or secondary osteoarthritis of the hip . Duration of follow-up ranged from 67–87 months ( mean 81 months ) . There were no early complications relating to the surgical procedure . There was one case of traumatic fracture of the femur during rehabilitation , while late complications included two cases of late infection ( 4 months and 16 months after surgery ) both revised in two-stage procedures . There was considerable improvement in Merle d'Aubigne score following surgery . There were no revisions for aseptic loosening , but we identified 2 implants with significant radiolucent lines and subsidence six years after the index operation . Neither patient experienced pain in the hip or restriction of activity . Therefore , the aseptic loosening survival rate was 100 % ( end point = revision operation ) . Taking radiological loosening as the end point survivorship was 93.3 % . The use of the Mayo short stem component in active patients may preserve bone and enable subsequent revision operations to proceed using primary implants . Our results suggest that conservative design s of this type may be of benefit in selected individuals Between 4/5/99 and 5/20/2002 , our university performed 31 total hip arthroplasties in 27 young patients utilizing a conservative hip prosthesis developed at the Mayo Clinic . Eleven patients underwent Bipolar replacement , while the remaining twenty required an acetabular component . The patients ranged in age from 25 to 50 ( mean of 39.9 ) . The mean follow up was 12.4 months ( range 4.5 - 27 ) . Twenty-eight hips were treated for AVN secondary to RA , HIV , ETOH abuse , and SLE ; while two underwent THA for OA secondary to trauma , and one for JRA . Three patients were lost to follow up at less than 6 months and were excluded from the study . The patients were followed for a minimum of 6 months utilizing the  Harris hip score  , the  Charnley hip score  , and  radiographic evaluation including subsidence , radiolucency , and calcar resorption . Four patients ( 13 % ) had subsidence ranging from 1 to 3 mm at the most recent visit . One patients ( 3.2 % ) had radiographic evidence of radiolucency measuring 2 mm . Nine patients ( 29 % ) developed 1 - 3 mm of calcar resorption . No hips required revision . Thirty patients had improvement in their Harris hip score and Charnley hip score . The one patient who decreased his score had developed AVN secondary to ETOH abuse . Three hips had an intra-operative complication of lateral cortex penetration and required circlage wiring . Comparisons were made utilizing Multiple Logistic Regression to determine if preoperative BMI , Dorr score , and gender had an impact on the postoperative hip scores or degree of osteolysis , subsidence , and calcar resorption . Although the Harris hip score and Charnley hip scores significantly improved postoperatively , the preoperative BMI , Dorr score , and gender did not correlate with patient outcome . Our patients improved clinical ly in pain level , function and ROM . Further follow up will reveal if this component truly preserves bone stock for ease of future revision Hip resurfacing ( HR ) and neck sparing prostheses ( NSP ) have been advocated for the treatment of arthritis in younger patients . Some complications following HR have been documented in the recent literature , but NSP are not yet supported by clinical follow-up studies of sufficient duration . We present an assessment of the neck sparing “ Biodynamic ” prosthesis .  153 patients were evaluated in a longitudinal cohort prospect i ve study , with survival analysis , clinical score and radiographic assessment of stability and osteointegration at 41.8 months average follow up . Survival and clinical outcome were similar to most traditional prostheses in the literature . On radiographic analysis we recorded good neck preservation and osteointegration . Only two stem failures were recorded . Poor clinical outcome was related to misalignment of prostheses implanted during the ‘ learning curve ’ . The NSP system described may be a good alternative to HR for younger patients . The system is characterized by good survival and clinical and radiographic outcome combined with bone stock preservation AIM The short-term results of a prospect i ve , consecutive series of 50 cementless modular short hip stem endoprostheses  are reported . METHOD 48 cases were available for clinical and radiological follow-up at an average time of 2.4 years post-op . One patient did not consent to a follow-up investigation , 1 early revision was necessary 4 weeks post-op after a fall precipitating a periprosthetic fracture . RESULTS The average age at the time of THA was 54 years and the Harris hip score reached 95 points at the time of follow-up . One implant had aseptic loosening and 1 implant was revised due to a failure of the modular titanium neck adapter . An equal number of patients received modular neck adapters with neutral or 7.5 degrees retroversion . No 140 degrees neck and no anteverted neck adapters were used . Radiological results of the 2/3 porous coated hip stem showed a metaphyseal bone remodelling with hypertrophies in coated Gruen zones 3 ( 17 % ) and 6 ( 46 % ) and marked spot welds and increased bone density ( 86 % ) in the distal area of the coating . Primary implant migration between 2 and 10 mm was present in 7 cases due to a low osteotomy and implant position combined with an implant undersizing and lack of proximal-lateral support . At the time of the last follow-up these cases had no clinical symptoms with an average HHS of 96 points and with full bony integration . CONCLUSION Our results support the use of the investigated short hip stem for THA when the femoral bone quality and morphology support the metaphyseal anchoring concept . The surgical technique must avoid a stem position without proximal-lateral cortical contact to the femoral osteotomy , as this reduces primary implant stability . Further follow-up is necessary to vali date the long-term success of this procedure The aim of this study was to determine whether  femoral neck preserving total hip arthroplasty  would become less difficult and more efficient during the first 20 cases and to identify potential pitfalls during the introduction of this procedure . The difficulty and efficiency of the initial 20 procedures performed by four surgeons was prospect ively determined by analysing a total of 68 video recordings using time-action analysis . This method measures the duration and efficiency of individual actions needed for a surgeon to achieve his or her goal . Afterwards , we review ed all actions with a long duration and discussed possible causes of delay with the surgeons to identify possible pitfalls . We found a decrease of difficulty and an increase of efficiency during the first 20 cases and a more consistent execution after the initial five cases . Estimating the correct osteotomy level and stem curvature was often difficult , which result ed in a variable stem position . Radiologic analysis demonstrated a tendency for varus position and increased leg length throughout the series , even after the surgeons demonstrated technical proficiency The changes of the periprosthetic bone density were examined with DEXA in 81 patients over a period of 1 year after implantation of cementless total hip endoprosthesis . Four types of endoprostheses ( Vision 2000/Duraloc , ALPHA-Fit/ALPHA-Lock Plus , CLS/Allofit , Mayo/Trilogy ) were implanted . Information on the changes of the periprosthetic bone density depending on the type of the prosthesis and the bony situation at the femur before operation was expected from these measurements . In all types of stems the strongest reduction of the bone density was found in the region of the calcar femoris , and the smallest changes were found distally and medially of the tip of the prostheses . In the prosthesis with shorter stem the change of the bone density was altogether clearly lower than in prostheses with longer stem . With increasing size of the prosthesis with proximally porous coating made from cobalt-chrome alloy , proximal atrophy was observed more frequently , whilst in the prosthesis made from titanium alloy with completely rough-blasted surface the distal hypertrophy increased . A 
    Output:
    
agent
These studies did not show a satisfactory overall survival rate
***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: Purpose Bone loss around uncemented femoral components is suspected to precede implant loosening and contribute to problems in revision surgery .  Short-stemmed cementless femoral components are design ed to preserve proximal femoral bone stock and ultimately the longevity of the prosthesis . Methods With quantitative computed tomography-assisted osteodensitometry , we prospect ively analyzed femoral cortical and cancellous bone density ( BD ) and contact area changes of an uncemented collum femoris preserving stem ( n = 38 ) 10 days , 1 , 3 and 7 years post-operatively . Results Seven years post-operatively  , cancellous BD ( mg CaHA/mL ) had decreased by as much as −66 % and cortical BD by up to −27 % at the metaphyseal portion of the femur ; the decrease was progressive between the 1- and 3-year examinations and halted thereafter . Contact area ( in % out of a possible 100 % ) decreased proximally between the 1- and 3-year follow-up . Conclusion Proximal cortical and cancellous bone density loss and decrease of contact area indicate that metaphyseal fixation can not be achieved . The lack of cortical BD loss and increase of contact area values below the trochanter minor suggest diaphyseal fixation Purpose On the basis of positive clinical results with mid- and long-term follow-up using the Mayo short stem , the Metha neck-preserving stem ( BBraun , Aesculap , Tuttlingen , Germany ) was introduced . The purpose of this study was to vali date the implant design by direct acquisition of bone remodelling data from total hip arthroplasty ( THA ) recipients using dual-energy X-ray absorptiometry ( DEXA ) . Methods After power analysis , 25 patients were included in this prospect i ve study . Patients were examined clinical ly and underwent DEXA examinations preoperatively and postoperatively at one week , six months and one and two years after THA . Gruen zones were adapted to the short stem design ( R1–R7 ) . Results The Harris Hip Score ( HHS ) increased significantly by 31 points . No stem had to be revised . Bone mineral density ( BMD ) in the greater trochanter decreased significantly from 0.78 g/cm2 postoperatively to 0.72 g/cm2 two years after surgery . Marginal changes were seen in the lateral distal regions ( R4–R5 ) . In the minor trochanter region , BMD increased significantly after two years by 12.9 % . In the calcar region , BMD exceeded the baseline value by 6.1 % two years after implantation . Conclusions Stress shielding seems to occur at the greater trochanter due to the vast cross-section of the implant . However , the aim of proximal load transfer of the Metha stem seems to be partially achieved . DEXA analysis revealed a concentrated load distribution on the medial portion of the femur , which is an important region to guarantee long-term implant survival Aim Tissue sparing hip prostheses are becoming more and more popular especially for the treatment of younger patients . The objective of this study was to evaluate the clinical and radiological results after insertion of a tissue sparing hip prosthesis . Method In 47 consecutive non-selected patients ( 50 hips ) , the clinical and radiographic results of cementless total hip arthroplasty using a collum femoris preserving stem , a pressfit cup and an alumina – polyethylene pairing were prospect ively evaluated . The mean age at index-surgery was 58 ( 36–82 ) years , there were 38 women and 9 men . After a mean follow-up of 6.8 years ( minimum 6.1 years ) , two patients had died and one patient underwent revision surgery due to aseptic loosening of the stem . Results The overall survival rate of the acetabular component was 100 % and of the femoral component 98 % . The mean Harris hip score at follow-up was 94 points . Conclusion The mid-term survival with this type of total hip arthroplasty is excellent and compares equal with uncemented straight stems in this age group The CFP stem represents a short collared neck-retaining stem with very proximal metaphyseal anchoring along the calcar combined with up-to- date metallurgy . Despite theoretical advantages , the stability and clinical outcome are unknown . We prospect ively measured the migration pattern of this new stem and cup . Twenty-six patients ( 26 hips ) with a mean age of 54 years ( range , 40 - 66 years ) underwent THA  and were followed for 2 years with  radiostereometry , radiographs , and clinical scores . The stem showed some early retroversion ( mean , SEM 0.6 ° , 0.3 ) , but stabilized before 1 year . Subsidence ( 0.05 mm , 0.06 ) and varus-valgus tilting ( 0.03 ° , 0.01 ) were low . We observed no bone loss in the calcar region . Factors related to patients , implant design , and implantation did not predict migration patterns . The two-dimensional wear of the ceramic/conventional articulation was 0.09 mm at 2 - 24 months . The low migration of this short neck preserving stem suggests a favorable long-term outcome but longer followup is needed to substantiate this prediction . This design might become an alternative to st and ard stems and hip resurfacing . Level of Evidence : Therapeutic Level IV . See The Guidelines for Authors for a complete description of levels of evidence This prospect i ve study reports the clinical and radiological results of a single-surgeon series using the Mayo conservative hip stem in a district hospital . 30 total hip arthroplasties were performed in 26 physically active patients . There were 18 women and 8 men , with a mean age of 57.4 years ( range 36–79 ) . 4 cases were bilateral . The operation was performed for severe primary or secondary osteoarthritis of the hip . Duration of follow-up ranged from 67–87 months ( mean 81 months ) . There were no early complications relating to the surgical procedure . There was one case of traumatic fracture of the femur during rehabilitation , while late complications included two cases of late infection ( 4 months and 16 months after surgery ) both revised in two-stage procedures . There was considerable improvement in Merle d'Aubigne score following surgery . There were no revisions for aseptic loosening , but we identified 2 implants with significant radiolucent lines and subsidence six years after the index operation . Neither patient experienced pain in the hip or restriction of activity . Therefore , the aseptic loosening survival rate was 100 % ( end point = revision operation ) . Taking radiological loosening as the end point survivorship was 93.3 % . The use of the Mayo short stem component in active patients may preserve bone and enable subsequent revision operations to proceed using primary implants . Our results suggest that conservative design s of this type may be of benefit in selected individuals Between 4/5/99 and 5/20/2002 , our university performed 31 total hip arthroplasties in 27 young patients utilizing a conservative hip prosthesis developed at the Mayo Clinic . Eleven patients underwent Bipolar replacement , while the remaining twenty required an acetabular component . The patients ranged in age from 25 to 50 ( mean of 39.9 ) . The mean follow up was 12.4 months ( range 4.5 - 27 ) . Twenty-eight hips were treated for AVN secondary to RA , HIV , ETOH abuse , and SLE ; while two underwent THA for OA secondary to trauma , and one for JRA . Three patients were lost to follow up at less than 6 months and were excluded from the study . The patients were followed for a minimum of 6 months utilizing the  Harris hip score  , the  Charnley hip score  , and  radiographic evaluation including subsidence , radiolucency , and calcar resorption . Four patients ( 13 % ) had subsidence ranging from 1 to 3 mm at the most recent visit . One patients ( 3.2 % ) had radiographic evidence of radiolucency measuring 2 mm . Nine patients ( 29 % ) developed 1 - 3 mm of calcar resorption . No hips required revision . Thirty patients had improvement in their Harris hip score and Charnley hip score . The one patient who decreased his score had developed AVN secondary to ETOH abuse . Three hips had an intra-operative complication of lateral cortex penetration and required circlage wiring . Comparisons were made utilizing Multiple Logistic Regression to determine if preoperative BMI , Dorr score , and gender had an impact on the postoperative hip scores or degree of osteolysis , subsidence , and calcar resorption . Although the Harris hip score and Charnley hip scores significantly improved postoperatively , the preoperative BMI , Dorr score , and gender did not correlate with patient outcome . Our patients improved clinical ly in pain level , function and ROM . Further follow up will reveal if this component truly preserves bone stock for ease of future revision Hip resurfacing ( HR ) and neck sparing prostheses ( NSP ) have been advocated for the treatment of arthritis in younger patients . Some complications following HR have been documented in the recent literature , but NSP are not yet supported by clinical follow-up studies of sufficient duration . We present an assessment of the neck sparing “ Biodynamic ” prosthesis .  153 patients were evaluated in a longitudinal cohort prospect i ve study , with survival analysis , clinical score and radiographic assessment of stability and osteointegration at 41.8 months average follow up . Survival and clinical outcome were similar to most traditional prostheses in the literature . On radiographic analysis we recorded good neck preservation and osteointegration . Only two stem failures were recorded . Poor clinical outcome was related to misalignment of prostheses implanted during the ‘ learning curve ’ . The NSP system described may be a good alternative to HR for younger patients . The system is characterized by good survival and clinical and radiographic outcome combined with bone stock preservation AIM The short-term results of a prospect i ve , consecutive series of 50 cementless modular short hip stem endoprostheses  are reported . METHOD 48 cases were available for clinical and radiological follow-up at an average time of 2.4 years post-op . One patient did not consent to a follow-up investigation , 1 early revision was necessary 4 weeks post-op after a fall precipitating a periprosthetic fracture . RESULTS The average age at the time of THA was 54 years and the Harris hip score reached 95 points at the time of follow-up . One implant had aseptic loosening and 1 implant was revised due to a failure of the modular titanium neck adapter . An equal number of patients received modular neck adapters with neutral or 7.5 degrees retroversion . No 140 degrees neck and no anteverted neck adapters were used . Radiological results of the 2/3 porous coated hip stem showed a metaphyseal bone remodelling with hypertrophies in coated Gruen zones 3 ( 17 % ) and 6 ( 46 % ) and marked spot welds and increased bone density ( 86 % ) in the distal area of the coating . Primary implant migration between 2 and 10 mm was present in 7 cases due to a low osteotomy and implant position combined with an implant undersizing and lack of proximal-lateral support . At the time of the last follow-up these cases had no clinical symptoms with an average HHS of 96 points and with full bony integration . CONCLUSION Our results support the use of the investigated short hip stem for THA when the femoral bone quality and morphology support the metaphyseal anchoring concept . The surgical technique must avoid a stem position without proximal-lateral cortical contact to the femoral osteotomy , as this reduces primary implant stability . Further follow-up is necessary to vali date the long-term success of this procedure The aim of this study was to determine whether  femoral neck preserving total hip arthroplasty  would become less difficult and more efficient during the first 20 cases and to identify potential pitfalls during the introduction of this procedure . The difficulty and efficiency of the initial 20 procedures performed by four surgeons was prospect ively determined by analysing a total of 68 video recordings using time-action analysis . This method measures the duration and efficiency of individual actions needed for a surgeon to achieve his or her goal . Afterwards , we review ed all actions with a long duration and discussed possible causes of delay with the surgeons to identify possible pitfalls . We found a decrease of difficulty and an increase of efficiency during the first 20 cases and a more consistent execution after the initial five cases . Estimating the correct osteotomy level and stem curvature was often difficult , which result ed in a variable stem position . Radiologic analysis demonstrated a tendency for varus position and increased leg length throughout the series , even after the surgeons demonstrated technical proficiency The changes of the periprosthetic bone density were examined with DEXA in 81 patients over a period of 1 year after implantation of cementless total hip endoprosthesis . Four types of endoprostheses ( Vision 2000/Duraloc , ALPHA-Fit/ALPHA-Lock Plus , CLS/Allofit , Mayo/Trilogy ) were implanted . Information on the changes of the periprosthetic bone density depending on the type of the prosthesis and the bony situation at the femur before operation was expected from these measurements . In all types of stems the strongest reduction of the bone density was found in the region of the calcar femoris , and the smallest changes were found distally and medially of the tip of the prostheses . In the prosthesis with shorter stem the change of the bone density was altogether clearly lower than in prostheses with longer stem . With increasing size of the prosthesis with proximally porous coating made from cobalt-chrome alloy , proximal atrophy was observed more frequently , whilst in the prosthesis made from titanium alloy with completely rough-blasted surface the distal hypertrophy increased . A 
    Output:
    