hip arthroplasty is one of the most frequently performed orthopedic procedures with high scores of success while its most common complication is aseptic loosening of the acetabular component , which may result from host bone loss or even from pelvis discontinuity . the purpose of the study was to evaluate results in patients after revision acetabular arthroplasty with reconstruction rings and allografts . retrospective data was collected from 69 revisions of acetabular components , performed in a group of 69 treated patients ( the mean age 65.1 years ) . before surgery , the patients had bone defects of type iib ( n = 5 ) , iic ( n = 20 ) , iiia ( n = 27 ) or iiib ( n = 17 ) , according to paprosky et al . the mean followup period of the patients was 7.2 years ( range 3 - 19 years ) . a kaplan  meier analysis showed that a 3- and 10 year survival rate was 92.8% and 84.8% respectively , using further revision for any reason of the acetabular device as an end point . four patients presented with ring loosening , one with a loose acetabular polyethylene cup , two hips demonstrated recurrent dislocations and one patient was with deep infection . regarding the remaining 61 patients without re - revision surgery , the mean harris hip score improved from 30.5 to 73.8 points . a modified , antiprotrusion cage provides an acceptable survival rate and radiological results , but complications could still be expected . it seems that the observed massive bone loss with pelvic discontinuity and an insufficient fixation of the cage to the ischium may result in implant loosening . stable fixation of the ischial ring flange with screws is an essential condition to expect a good outcome . hip arthroplasty is one of the most frequently performed orthopedic procedures with high scores of success while its most common complication is aseptic loosening of the acetabular component , which may result from host bone loss or even from pelvis discontinuity.12 in revision hip arthroplasty , reconstruction rings are commonly used for the acetabular restoration of massive bone stock losses.34 the purpose of the study was to analyze results of acetabular cup revision with reconstruction rings - recon ring ( shell ) ( aesculap / bbraun , tuttlingen , germany ) . 69 patients ( 11 men and 58 women with unilateral cup loosening ) with revision surgeries of acetabular component using reconstruction rings between january 1993 and november 2009 were included in the study . the mean age of patients at the time of surgery was 65.1 years ( range 30.7 - 88.4 years ) . four patients passed away during the followup for other reasons , but there were no signs of loosening in that group . those patients were included in the study and results from the last followup were analyzed . the initial diagnoses before primary hip arthroplasty included : idiopathic coxarthrosis ( n = 35 ) , rheumatoid arthritis ( n = 10 ) , femoral neck fracture ( n = 10 ) , dysplastic coxarthrosis ( n = 11 ) and avascular necrosis ( n = 3 ) . it was the first acetabular revision for 40 patients , the second one for 19 , the third one for 6 and the fourth for 1 patient . all the patients presented with bone defect of type iib ( n = 5 ) , iic ( n = 20 ) , iiia ( n = 27 ) or iiib ( n = 17 ) , according to paprosky et al.2 [ table 1 ] . paprosky et al.2 ( 1994 ) classification of acetabular defects the size of reconstruction ring ( recon ring ( shell ) ( aesculap / bbraun , tuttlingen , germany ) was determined before the operation , using templates and the most recent radiographs of the hip . all the hips were operated from the anterolateral approach in the supine position , through ilio - tibial band , then between the rectus femoris muscle and the gluteus medius muscle . acetabular host bone stock was thoroughly debrided from soft scar tissue , and sclerotic areas were perforated by multiple 2 mm drill holes . once the preparation of the acetabulum was completed , the acetabular bed was examined to evaluate bone defects and to determine if its bone stock could provide an adequate mechanical support for the cage and its flanges . following acetabular bone loss assessment ( if bone stock was inadequate to give support for acetabular cup only ) , the final measurement of ilioischial reconstruction ring was performed . one of the three available ring sizes ( 54 mm , 58 mm or 64 mm ) was chosen and fixed to the bony acetabulum . depending on implant size and host bone quality , as many cancellous screws as possible were used to fix the cage into the bone . special attention was paid to cross the screws fixed in the ilium and to anchor lower part of the cage to ischium . having achieved bone support of the cage , the remaining space between the bone acetabulum and the spherical dome of the ring was filled with cancellous , morselized allografts.5 grafts were introduced through a hole in ring dome . the chips were impacted with a metal impactor and a mallet in all type iii defects and in 12 cases of iic defects with a deep lack of the medial acetabular wall . a frozen , cancellous , morselized allograft was used in 21 cases and morselized femoral head allografts in 35 cases . in 13 cases of revisions , the reconstruction rings were used alone , without the grafts , due to the proper , full support of the cage dome in the ilium ( all iib defects and 8 iic ) . in the case of the allografts from the femoral head , each graft was first defrozen and then divided into 79 mm chips of the cancellous bone . all the allografts , used for that procedure , were sterilized by radiation and picked up from the local bone bank . no massive structural bone grafts nor other fixation techniques ( plates ) or tantalum augments were used anytime . when the ring was stabilized , a standard polyethylene cup was implanted and fixed with cement in proper inclination and anteversion . all the patients were postoperatively followedup , both clinically and radiographically , every 3 months for 1 year and then every 6 months . harris hip score ( hhs)6 was applied for clinical assessment before operation and at followup visits . the ten point visual analog scale for pain ( vas ) score was used to evaluate pain before surgery and at the last followup visit . the actual position of the acetabular cup and of the ring was evaluated in each radiograph . radiolucent signs around the acetabulum were analyzed in each of the three zones of delee and charnley.7 shapiro the wilcoxon signed rank test was used to determine whether there was a statistically significant difference between preoperative and postoperative ( last followup ) hhs , as well as between preoperative and postoperative ( last followup ) vas scale . the survival rate analysis was performed by the kaplan  meier method , using the need for further revision of the acetabular device as an end point.8 statistical analyses were performed , using the statgraphics plus program for windows 5.1 ( statpoint technologies , inc . , usa ) and p < the research project was approved by the bioethics commission at our institution ( protocol no . rnn/2/12/ke ) . written informed consent for participation in the study was obtained from participants . in 61 , out of the 69 hip implants , stability was confirmed at the last followup with need for revision surgery . in those 61 cases , no migration of the ring or cup was observed . a kaplan  meier analysis showed a 3-year and 10-year survival rate in 92.8% and 84.8% , of the patients respectively , using further revision for any reason of the acetabular component as an end point . in those cases , the average clinicoradiological followup was 7.2 years ( range 3 - 19 years ) [ table 2 ] . in three cases , radiolucency was found in zone 3 , according to delee and charnley , without clinical symptoms or radiological features of loosening . eight patients demonstrated implant related complications [ table 3 , figures 1 and 2 ] , one with an iliac flange of the ring fracture in the reconstruction ring at screw hole level , together with cracked screws [ case 1 in table 3 ] . the failure was probably caused by material fatigue in consequence of multicyclic plastic implant deformities in the process of loosening . the iliac flange of the cage was well fixed to the bone , while the ischial flange became loose , and the dome had no sufficient bone support . clinical and demographic data of 8 patients with acetabulum related complications the roentgenogram in anteroposterior projection of patient hip with an iliac flange fracture in the reconstruction ring at screw hole level , together with 3 cracked screws the roentgenogram in anteroposterior projectionof patient hip with a fixing screw fractures in the other three of the rings [ cases 2 , 3 and 4 in table 3 ] , evaluated in our series , failure fixation was noted , in both cases with cracking of screws , medial implant migration and inferior flange of the cage loosening . resorption of bone grafts above the ring dome and subsequent bone loss were recorded in each case on radiographs . an additional fixation failure of the ischial flange of the ring resulted in the whole implant instability . the above mentioned four cases of compromised stability , massive bone stock losses with pelvic discontinuity were found . during subsequent revisions of the patients , the good quality of the previously implanted bone grafts the grafts were still well incorporated into the host bone . in one of the cases , a consecutive revision was done without reconstruction ring application as the bone stock status allowed for cementless cup fixation with a solid bone graft . in the remaining three patients , reconstruction rings and bone grafts in one , socket malposition developed with cup reorientation . in the second one , a femoral neck adapter ( merete , the bioball company , germany ) was used as the identified dislocation was related to poor quality muscles around the hip . one patient had a deep infection , treated by removal and debridement of acetabular implants [ case 8 in table 3 ] . other complications in those revision surgeries included nerve palsy : four peroneal and 2 femoral . both femoral and three peroneal palsies resolved between 2 weeks and 9 months while one was permanently maintained . a considerable number of the patients after revision hip arthroplasty demonstrated large acetabular bone defects , extensive scaring and muscle loss . the application of bruch - schneider antiprotrusion cage is a durable solution , provided those proper indications and techniques are used . the survival rate , when using these implants , ranges from 83% to 95% at mid - and long term followup.491011121314151617181920 in most series , the average hhs ranges from 70 to 83.410131520 the success rate of acetabular revision operations , defined as stable , functional hip , amounted to 61 , out of 69 patients in our series . we are aware that the hhs does not fully reflect reconstruction success as many of the patients had 2 or more joint surgeries in the past . the mean functional score of 73.8 , presented in our study , is not fully satisfactory , when comparing to primary hip arthroplasty . however , patients revealed a significant functional improvement in the operated joints , comparing with the preoperative status . given the criteria of nondislocating and nonmigrating hip , the success rate in the series of goodman et al.10 was 76% . the percentage would have been even higher , having added the cases , in which both the reconstruction ring and the bone graft were left in situ . schlegel et al.4 noted that the 5-year and 8-year survival rate after revisions with reinforcement ring was 95% and 90% respectively . the mean hhs in that series was 70 . in the study of regis et al.14 hhs was 75 at 11.7 years on the average and the survival rate achieved 87.5% . symeonides et al.16 described 89% survival during maximum 21-year in 57 patients . the results of peters et al.12 are also encouraging . clinically , 80% of their patients functioned as , at least , community ambulators and 80% sensed mild or no pain . in 14% of hips , jones et al.11 reported a 95% survival and significant functional improvement after 9 year , using the burch schneider antiprotrusio cage . using the in built roentgen analyse they found some evidence of implant migration above 1 mm in all the cases , but there was no evidence of radiological loosening and no screws were found to be broken . the aseptic loosening rate , reported in the literature , ranges from 0% to 18% in mid and long term results.491011121314151617181920 in the revision operations of the acetabulum in our series , 11.6% of the patients had implant related problems : reconstruction ring loosening , cup loosening , dislocation or deep infection . four of our patients demonstrated a loose reinforcement ring ( with its fracture in one case ) . in all those hips , massive bone loss was found during revision operation with concomitant pelvis discontinuity . the implant fractures in the iliac part were secondary to instability of the ischial flange and the ring dome . it seems that in the most severe cases of pelvic discontinuity , implants do not restore stability and get loose , first in the ischial part . then , cracking of proximal screws or of the ring may be expected , with secondary bone graft lysis . other potential causes of loosening  high body mass index , patient 's noncompliance and specially too early full weight bearing were also possible , however , difficult to prove on the basis of our material . loosening of the acetabular cup is a rare complication , seen in one of our cases . that problem has also been described by goodman et al.10 postoperative dislocation is another issue , sometimes observed after this kind of surgery . even if the positioning of implants , seen on postoperative radiographs , is satisfactory , the hip joint surrounding muscles may be a week or damaged during previous operations . in our opinion , this is the main factor that may lead to postoperative hip dislocation . in the study of goodman et al.10 the rate of complications after the use of antiprotrusion , cages was higher than in our series . among their 61 cases , 5 rings lost fixation , 3 rings cracked , 3 acetabular cups were loose , 7 hips were dislocated and 3 deep infections were diagnosed . they also reported a relatively high prevalence rate of sciatic and peroneal nerve palsy that may have been related to ischial flange of the implant slotting and inferior screws to the ischial bone . one patient was with postoperative dislocation and one with deep infection , both being successfully treated . despite some intraoperative and temporary postoperative complications , the eventual clinical results were satisfactory in the vast majority of patients . among the patients of peters et al.12 two dislocations , out of 28 acetabular revisions , were nonoperatively managed . in the study of crockarell9 two , out of 11 revisions with reconstruction rings , required reoperation . we fully agree with the author , who found out that massive bone defects and poor ischial fixation were common in the identified cases of implant loosening . et al.17 the mechanical failure rate was17% and dislocation occurred in 23% of hips at 4.6 followup . despite a loose antiprotrusion cage , bone stock restoration might be expected . in one of our cases , following cage revision , the bone bed remained so well shaped that we decided to implant a cementless cup with support of structural bone graft . kosashvili et al.21 reported results of 15 failed acetabular cage revisions with bone stock restoration , performed with the use of bone graft during index procedure . in all those cases , they implanted highly porous cementless hemispheric cups during re revision . the antiprotrusion cage gives an opportunity to implant a polyethylene cup in a more anatomical position , acting as a bridge between the ischium and the ilium , providing more stability , protecting bone grafts and allowing for graft remodelling . in cases of massive bone stock , it is sometimes the only possible surgical option . definitely , it is an extensive procedure and striping of the gluteus medius muscle from the ilium is necessary . in the postoperative period , patients have for many months to exercise , walking with partial weight bearing to allow bone graft integration as the primary stability of the implant is not sufficient to transfer full body weight . the modified antiprotrusion cage technique provided an acceptable survival rate and radiological results , but complications might be expected . it seems that a massive bone loss with pelvic discontinuity and insufficient fixation of the cage to the ischium may be related to implant loosening . stable fixation of the ischial ring flange with screws over the bone grafts is essential for a good outcome .
background : hip arthroplasty is one of the most frequently performed orthopedic procedures with high scores of success while its most common complication is aseptic loosening of the acetabular component , which may result from host bone loss or even from pelvis discontinuity . the purpose of the study was to evaluate results in patients after revision acetabular arthroplasty with reconstruction rings and allografts.materials and methods : retrospective data was collected from 69 revisions of acetabular components , performed in a group of 69 treated patients ( the mean age 65.1 years ) . before surgery , the patients had bone defects of type iib ( n = 5 ) , iic ( n = 20 ) , iiia ( n = 27 ) or iiib ( n = 17 ) , according to paprosky et al . 
 results : the mean followup period of the patients was 7.2 years ( range 3 - 19 years ) . 
 a kaplan  meier analysis showed that a 3- and 10 year survival rate was 92.8% and 84.8% respectively , using further revision for any reason of the acetabular device as an end point . 
 eight patients revealed implant related complications . 
 four patients presented with ring loosening , one with a loose acetabular polyethylene cup , two hips demonstrated recurrent dislocations and one patient was with deep infection . regarding the remaining 61 patients without re - revision surgery , the mean harris hip score improved from 30.5 to 73.8 points.conclusion:a modified , antiprotrusion cage provides an acceptable survival rate and radiological results , but complications could still be expected . 
 it seems that the observed massive bone loss with pelvic discontinuity and an insufficient fixation of the cage to the ischium may result in implant loosening . 
 stable fixation of the ischial ring flange with screws is an essential condition to expect a good outcome .