until today , total hip arthroplasty ( tha ) procedure has been recognized as the wonderful procedure in terms of patient 's satisfaction . thanks to the advent of large diameter femoral head , we can lower a probability of dislocation after tha . large diameter femoral heads provide a means of reducing the risk of dislocation , but increases in wear debris have prevented the widespread use of this option in primary articulation3,4 ) . highly cross - linked polyethylene was introduced for use in primary tha to reduce periprosthetic osteolysis due to a reduction in wear debris . early and intermediate - term results of primary tha using highly cross - linked polyethylene bearing surfaces are promising4,5 ) . base on these findings , we hypothesized that tha conducted using a 36-mm femoral head paired with highly cross - linked polyethylene would show low rates of dislocation and no appreciable wear debris . however , it is unclear whether these lower wear rates are really achieved in korean population over long time beyond 7 years . accordingly , the purpose of this study was to evaluate the clinical and radiographic midterm results of primary tha using a large diameter femoral head on highly cross - linked polyethylene ( minimum 7-year follow - up ) . we retrospectively reviewed 73 patients ( 74 hips ) that underwent tha with a large diameter femoral head on highly cross - linked polyethylene between july 2004 and february 2007 ( table 1 ) . we had also 2 cases of pathologic femoral neck fracture due to benign bone tumor . mean patient age was 62 years ( range , 21 - 86 years ; 37 males and 36 females ) , and mean follow - up was 96 months ( range , 84 - 122 months ) ( table 2 ) . a cementless acetabular cup with a porous coating ( trilogy ; zimmer inc . , warsaw , in , usa ) and a highly cross - linked polyethylene liner with an inner diameter of 36 mm ( longevity : zimmer inc . ) was placed in all patients . acetabular components had a average outer diameter of 54.7 mm ( range , 50 - 62 mm ) . the polyethylene liners were machined from gur 1050 polyethylene , which had been pre - heated and cross - linked with a 9.5 mrad electron - beam . the preforms were then melted to eliminate the remaining free radicals and sterilized using a gas plasma . components were used in 66 case underwent cementless femoral fixation ( fig . 1 ) and versys ( zimmer inc . ) if cementless femoral stem had a unstable fixation intraoperatively , we used cemented femoral fixation regardless of patient 's age . all cementless stems were inserted using standard press fit techniques to insure longitudinal and rotational stability , and all cemented femoral stems were inserted using meticulous third generation cementing techniques . all surgical procedures were performed by one surgeon ( mrc ) using a modified harding 's approach with the patient in the lateral position . prophylactic antibiotics were administrated to all 73 patients , and the same post - operative protocol was used in all . patients were allowed to sit on the first postoperative day and stand with support , according to ability , after blood drainage removal . no range of motion ( rom ) limitation was present immediately after surgery , and no abduction pillow was used in any patient . patients were followed at 6 weeks , and at 3 , 6 , and 12 months postoperatively . in addition , modified harris hip scores ( hhs ) and merle d'aubigne and postel score were determined . modified hhs were classified as excellent ( 91 - 100 ) , good ( 81 - 90 ) , fair ( 71 - 80 ) , or poor ( 61 - 70 ) , and the merle d'aubigne and postel scores were used to categorize patients to six grades according to level of pain ( 1 - 6 ) , mobility ( 1 - 6 ) , and the ability to walk ( 1 - 6 ) . in cases that underwent uncemented fixation , 's method6 ) , and in cases that underwent cemented fixation , femoral components were assessed the amount of cement filling using barrack et al . all radiographic examinations included an anteroposterior view of the pelvis centered over the pubis , and axial view by a shoot through lateral of the hip . acetabular cup abduction angles were measured using engh et al.8 ) and kennedy et al's9 ) methods . acetabular cup anteversion angles were measured using widmer's10 ) method and it also calculated using polyware pro three - dimensional ( 3d ) distal version 5.10 software ( drafware developers inc . , vevay , in , usa ) . the evidence of linear radiolucencies , bony ingrowth , fracture , and osteolysis were determined using sequential radiographic views , which also allowed comparative assessments of component position versus immediate postoperative views to determine the presence of component migration and/or loosening . penetrations of femoral heads into polyethylene liners were calculated as two - dimensional linear penetrations on anteroposterior radiographs of the pelvis using polyware pro 3d distal version 5.10 software . in this program , wear rate is calculated through the 3-point marked on edges of the femoral head and acetabular cup using serial plain radiograph ( fig . the mean total femoral head penetration was calculated by determining the magnitude of femoral head penetration shown first postoperative and final follow - up radiographs , and normalizing with respect to the duration of radiographic follow - up . the total penetration rate of the femoral head into the acetabular polyethylene is a result of the plastic creep and wear of the liner . to separate the early bedding - in process from steady - state wear , we also calculated mean total femoral head penetration shown by first post - operative and one - year radiographs and by one - year and final follow - up radiographs . average modified hhs at final follow - up was 887.5 ( range , 81 - 96 ) , and it was better than ' good ' in all cases , and merle d'aubigne and postel scores were more than 15 ( range , 15 - 18 ) in all cases . but we could guess who had better previous hip functional scores had a tendency to earn the better post operation functional hip scores . radiographic final follow - up exams showed stable fixation in all patients with uncemented femoral components , and barrack type a or b in all patients with cemented femoral components . mean acetabular cup inclination and anteversion were 50.1(range , 35-58 ) and 23.6(range , 5-38 ) , respectively . there was no radiographic evidence of osteolysis in the pelvis or proximal femur , and no acetabular cup or femoral stem failing due to aseptic loosening ( table 3 ) . she sustained car accident and had a injury of femoral head posterior dislocation with acetabular fracture . anteversion of the index cup was 8. the patient underwent isolated acetabular revision just after second dislocation , and has done routine indoor activity well since then . in all patients , average femoral head penetration during the first postoperative year ( predominantly representing polyethylene creep ) was 0.0710.034 mm / year , and the average steady - state wear rate determined using radiographs taken at one - year postoperatively and at latest follow - up was 0.0510.022 mm / year . larger diameter femoral heads are believed to be less prone to dislocation and facilitate higher roms2 ) . however , the widespread adoption of larger diameter femoral heads against conventional polyethylene is limited by the risk of accelerated wear and resulting osteolysis . the development of a new cross - linked polyethylene with improved wear characteristics , according to early laboratory and clinical studies , could reduce the risk of wear . hip simulator studies have also demonstrated very low wear rates for even larger heads when a highly cross - linked polyethylene liners are used4,11 ) . in other case of using 36- and 40-mm femoral head with a highly cross - linked polyethylene liner , martell had a result of 0.075 mm / year wear rate in 5 to 8 years follow - up12 ) . our institute outcome is comparable with this result . in the present study , even though one patient experienced a hip dislocation , patient satisfaction was high due to no rom or hip posture limitation during the early post - operative period . however , despite the stability advantage observed during this study , the occurrences of this dislocation indicates the importance of proper orientation of the acetabular and femoral components during surgery13 ) . polyethylene thickness is considered an important wear rate factor , a patient must have a 50 mm diameter acetabulum to allow a 36-mm femoral head to be used . when we used 50 mm diameter of acetabulum , the polyethylene thickness was 5.8 mm . on basis many opinions advocate that even though diameter of liner is just only 3 mm , this can be used without concerns of problematic wear increase relatively14 ) , our research have used that implant system . furthermore , now us food and drug administration approved the use of more than 3 mm diameter of liner . even though insuring adequate polyethylene thickness may or may not be an issue with highly cross - linked polyethylene , this evidence concerns the increased wear rates of thin ultra high molecular weight polyethylene ( uhwpe ) liners11,15,16 ) . the early bedding - in of the femoral head resulting from plastic creep and other factors can confound early measurements of wear . estok et al.17 ) reported a femoral head penetration resulting from creep of -0.1 mm for both conventional and highly cross - linked polyethylene . in the present study , the magnitude of femoral head penetration during the first postoperative year was 0.0710.034 mm / year . on the other hand , steady - state wear rate was 0.0510.022 mm / year . and , average femoral head penetration during entire follow - ups was 0.0580.013 mm / year . however , it should be noted that the present study has limited statistical power because the cohort was not prospectively randomized . also , we have some limitations in measuring wear rate . as to method of wear measurement , radiostereometric analysis ( rsa ) however , many radiographic in vivo studies of polyethylene wear in tha are restricted to measurements on plain radiographs because the rsa set - up is expensive and not widely available . polyware software does not supply the accuracy required , and for such situations we recommend rsa . for assessment of medium - term or long - term wear measurements in larger groups of patients , it is known as the polyware method is optimal , simple , and in relatively close agreement with the gold standard of rsa . nonetheless , the mid - terms results of primary tha with a 36 mm diameter femoral head on highly cross - linked polyethylene in patients was found to be comparable with in vitro laboratory hip simulation studies , and was found to be associated with high patient satisfaction due to no rom or hip posture limitations during the early post - operative period . however , further follow - up studies are required to evaluate long - term wear - rates , the development of osteolysis , and the problem of the tribocorrosion developed between artificial head and neck of the stem . primary tha with a 36 mm diameter femoral head on highly cross - linked polyethylene was found to produce the low wear rates of 0.0580.013 mm / year which comparable to previous in vitro laboratory hip simulation studies . in particular , patient satisfaction was high due to no rom or hip posture limitation during the early postoperative period .
purposewe evaluate the clinical and radiographic midterm results of primary total hip arthroplasty ( tha ) using a 36 mm diameter femoral head on highly cross - linked polyethylene ( minimum 7-year follow - up).materials and methodswe retrospectively reviewed 73 patients ( 74 hips ) that underwent primary tha with a 36 mm diameter femoral head on highly cross - linked polyethylene between july 2004 and february 2007 . 
 clinical follow - ups included specific measurements like modified harris hip scores ( hhs ) and merle d'aubigne and postel score . for radiologic evaluations , together with position of acetabular cup at 6 weeks later of post - operation , we separately calculated the penentrations of femoral heads into polyethylene liners during post - operation and one year later check - ups , and during one year later check - ups and final check-ups.resultsthere were no complications except for one case of dislocation . 
 average modified hhs at final follow - up was 887.5 ( range , 81 - 96 ) , and merle d'aubigne and postel scores were more than 15 ( range , 15 - 18 ) . 
 mean acetabular cup inclination and anteversion were 50.1(range , 35-58 ) and 23.6(range , 5-38 ) , respectively . 
 average femoral head penetration during the first postoperative year was 0.0710.034 mm / year , and steady - state wear rate determined using radiographs taken at one - year postoperatively and at latest follow - up was 0.0510.022 mm / year . 
 average femoral head penetration during entire follow - ups was 0.0580.013 mm / year.conclusionprimary tha with a large diameter femoral head on highly cross - linked polyethylene was found to produce the results comparable to previous in vitro laboratory hip simulation studies . 
 and we also find out good scores in terms of patient 's functionality .