we identified 27 hips in 27 patients who underwent revision tha and showed metallosis from a catastrophic failure of a pe liner in their hip joints during revision tha among all the patients who underwent revision thas in seoul national university hospital between january 1996 and august 2004 . three patients were lost to follow - up during the 5 years period after surgery and could not be reached by telephone or mail . excluding these 4 patients , 23 patients ( 12 men and 11 women ) had tha at the average age of 38.4 years ( range , 15 to 63 years ) , had index revision thas at the average age of 48.1 years ( range , 23 to 78 years ) and the average interval between tha and revision tha was 9.7 years ( range , 4.0 to 14.2 years ) . patients were followed for at least 6.5 years after the index revision tha ( average duration of follow - up , 12.5 years ; range , 6.5 to 18.0 years ) . nineteen of the 23 hips underwent clinical and radiographic evaluations and four hips underwent clinical evaluation only , which was conducted over the telephone and with a questionnaire sent by mail . the initial cause of primary tha was osteonecrosis of the femoral head in 7 patients , degenerative arthritis in 5 patients , legg - calve - perthes disease sequelae in 3 patients , developmental dysplasia of the hip in 2 patients , infection sequelae in 2 patients , tuberculosis sequelae in 1 patient , developmental coxa valga in 1 patient , dysplasia in 1 patient , and rheumatoid arthritis in 1 patient . metal - on - pe bearings were used for primary tha in 22 patients , and ceramic - on - pe bearing was used in 1 patient . nineteen thas were done in our hospital and their implants were the aml hip system ( depuy , warsaw , in , usa ) in 8 hips and osteonics hip system ( stryker , kalamazoo , mi , usa ) in 11 hips . implants of remaining 4 hips are not identifiable because the thas were performed at other hospitals and the corresponding medical records were insufficient . considering the time of the primary thas ( 1988 , 1994 , 1995 , and 1996 ) , the unidentifiable 4 liners probably were conventional pe . the revision thas were performed due to osteolysis without loosening in 21 hips and osteolysis with loosening of the cup in 2 hips . two hip surgeons who had more than 15 years of experience with hip operations each , performed all the revision thas . the bubble sign , which is known to be related with metallosis , was observed in 10 hips on plain radiographs taken before revision thas.12 ) the extent and location of the osteolysis were evaluated on preoperative radiographs , and bone deficiency around the cup and stem was categorized according to the system of the american association of orthopaedic surgeons.13,14 ) osteolysis was defined as periprosthetic cystic or scalloped lesions with a diameter exceeding 2 mm that had not been noted on the immediate postoperative radiograph.15,16 ) among the 23 hips , 15 hips showed type iii acetabular defects . type ii acetabular defects were observed in 7 hips , and a type i acetabular defect was observed in one hip . osteolysis around the femur was also observed in all 23 hips before revision thas with type i osteolysis in 6 hips and type ii osteolysis in 17 hips . total revision and cup revision procedures were performed in 13 and 10 hips , respectively . posterolateral and transtrochanteric approaches were used for revision thas in 10 hips and in 13 hips , respectively . cementless acetabular implants were used in 22 hips and an acetabular reinforcement ring was used in one hip for revision thas . chang et al.7 ) classified the severity of metallosis as grade i ( mild : black spotting in the soft tissues ) , grade ii ( moderate : geographically patterned black stain in soft tissues ) , and grade iii ( severe : black spotting throughout the soft tissues and bones ) . we used the same grading criteria and all 23 hips in this study showed grade iii metallosis ( fig . 1 ) during revision thas . we irrigated the operative field copiously and removed the functionless black - stained tissue as best we could . bone grafts were applied to both the acetabular and femoral defects in all hips . during revision surgery , metal - on - pe bearings were used in 12 hips , ceramic - on - ceramic bearings were used in 5 hips , ceramic - on - pe bearings were used in 4 hips , and metal - on - metal bearings were used in 2 hips . three of 16 pe liners were crossed linked pe and the others were conventional pe . clinical evaluations were performed using harris hip scores.17 ) when the patient could not visit the hospital , the evaluation was completed via telephone or by mail . radiographs were evaluated by two independent observers , who had completed their residency and fellowship programs and were working as adult hip reconstruction specialists for 22 years and 5 years , respectively , and were well - experienced in assessing the presence of osteolysis and loosening . a change in the angle of more than 4 , or vertical or horizontal migration of more than 3 mm were taken as evidences of an unstable cup.15 ) instability of the femoral stem was defined as subsidence or vertical migration of more than 2 mm or a change in the stem angle of more than 2 , on the anteroposterior radiographs.18 ) kaplan - meier survival analysis was performed to assess the implant survival after revision . the 15-year survival rates of revision tha were measured using osteolysis or loosening as the endpoint , respectively . demographic and clinical variables were compared by using chi - square or fisher exact tests for categorical variables such as gender , bubble sign , revision type , bearing for revision tha and bony defect severity between patients demonstrating osteolysis or loosening and the others . the t - test was also used to compare continuous variables such as age at revision tha and body mass index ( bmi ) . we identified 27 hips in 27 patients who underwent revision tha and showed metallosis from a catastrophic failure of a pe liner in their hip joints during revision tha among all the patients who underwent revision thas in seoul national university hospital between january 1996 and august 2004 . three patients were lost to follow - up during the 5 years period after surgery and could not be reached by telephone or mail . excluding these 4 patients , 23 patients ( 12 men and 11 women ) had tha at the average age of 38.4 years ( range , 15 to 63 years ) , had index revision thas at the average age of 48.1 years ( range , 23 to 78 years ) and the average interval between tha and revision tha was 9.7 years ( range , 4.0 to 14.2 years ) . patients were followed for at least 6.5 years after the index revision tha ( average duration of follow - up , 12.5 years ; range , 6.5 to 18.0 years ) . nineteen of the 23 hips underwent clinical and radiographic evaluations and four hips underwent clinical evaluation only , which was conducted over the telephone and with a questionnaire sent by mail . the initial cause of primary tha was osteonecrosis of the femoral head in 7 patients , degenerative arthritis in 5 patients , legg - calve - perthes disease sequelae in 3 patients , developmental dysplasia of the hip in 2 patients , infection sequelae in 2 patients , tuberculosis sequelae in 1 patient , developmental coxa valga in 1 patient , dysplasia in 1 patient , and rheumatoid arthritis in 1 patient . metal - on - pe bearings were used for primary tha in 22 patients , and ceramic - on - pe bearing was used in 1 patient . nineteen thas were done in our hospital and their implants were the aml hip system ( depuy , warsaw , in , usa ) in 8 hips and osteonics hip system ( stryker , kalamazoo , mi , usa ) in 11 hips . implants of remaining 4 hips are not identifiable because the thas were performed at other hospitals and the corresponding medical records were insufficient . considering the time of the primary thas ( 1988 , 1994 , 1995 , and 1996 ) , the unidentifiable 4 liners probably were conventional pe . the revision thas were performed due to osteolysis without loosening in 21 hips and osteolysis with loosening of the cup in 2 hips . two hip surgeons who had more than 15 years of experience with hip operations each , performed all the revision thas . the bubble sign , which is known to be related with metallosis , was observed in 10 hips on plain radiographs taken before revision thas.12 ) the extent and location of the osteolysis were evaluated on preoperative radiographs , and bone deficiency around the cup and stem was categorized according to the system of the american association of orthopaedic surgeons.13,14 ) osteolysis was defined as periprosthetic cystic or scalloped lesions with a diameter exceeding 2 mm that had not been noted on the immediate postoperative radiograph.15,16 ) among the 23 hips , 15 hips showed type iii acetabular defects . type ii acetabular defects were observed in 7 hips , and a type i acetabular defect was observed in one hip . osteolysis around the femur was also observed in all 23 hips before revision thas with type i osteolysis in 6 hips and type ii osteolysis in 17 hips . total revision and cup revision procedures were performed in 13 and 10 hips , respectively . posterolateral and transtrochanteric approaches were used for revision thas in 10 hips and in 13 hips , respectively . cementless acetabular implants were used in 22 hips and an acetabular reinforcement ring was used in one hip for revision thas . chang et al.7 ) classified the severity of metallosis as grade i ( mild : black spotting in the soft tissues ) , grade ii ( moderate : geographically patterned black stain in soft tissues ) , and grade iii ( severe : black spotting throughout the soft tissues and bones ) . we used the same grading criteria and all 23 hips in this study showed grade iii metallosis ( fig . 1 ) during revision thas . we irrigated the operative field copiously and removed the functionless black - stained tissue as best we could . bone grafts were applied to both the acetabular and femoral defects in all hips . during revision surgery , metal - on - pe bearings were used in 12 hips , ceramic - on - ceramic bearings were used in 5 hips , ceramic - on - pe bearings were used in 4 hips , and metal - on - metal bearings were used in 2 hips . three of 16 pe liners were crossed linked pe and the others were conventional pe . clinical evaluations were performed using harris hip scores.17 ) when the patient could not visit the hospital , the evaluation was completed via telephone or by mail . radiographs were evaluated by two independent observers , who had completed their residency and fellowship programs and were working as adult hip reconstruction specialists for 22 years and 5 years , respectively , and were well - experienced in assessing the presence of osteolysis and loosening . a change in the angle of more than 4 , or vertical or horizontal migration of more than 3 mm were taken as evidences of an unstable cup.15 ) instability of the femoral stem was defined as subsidence or vertical migration of more than 2 mm or a change in the stem angle of more than 2 , on the anteroposterior radiographs.18 ) the 15-year survival rates of revision tha were measured using osteolysis or loosening as the endpoint , respectively . demographic and clinical variables were compared by using chi - square or fisher exact tests for categorical variables such as gender , bubble sign , revision type , bearing for revision tha and bony defect severity between patients demonstrating osteolysis or loosening and the others . the t - test was also used to compare continuous variables such as age at revision tha and body mass index ( bmi ) . they both died of an unrelated medical condition at 6.5 years and 16 years after their revision tha procedures , respectively . one of these two patients could not visit the outpatient clinic due to a geographical reason and did not complain of any hip problems over the phone before death . the other patient died 16 years after the revision tha and used a cane due to hemiplegia from a cerebrovascular attack . the median harris hip score increased from 60 points ( range , 35 to 89 points ) before revision tha to 90 points ( range , 3 to 98 points ) at the final follow - up ( fig . three patients reported a decrease in the harris hip score at the last follow - up . osteolysis was detected on average 9.3 years ( range , 5.3 to 13.5 years ) after revision thas in 13 hips ( fig . , the acetabular cup was loosened an average of 9.8 years ( range , 5.7 to 18.3 years ) after revision tha in 9 hips . re - revision of the cup was performed in 5 hips and re - revision of both the cup and stem was performed in 2 of the 9 loosened hips ( fig . , cup removal and cutting of the artificial femoral neck were performed due to severe bone loss and vessel injury following cup re - revision due to infection on two occasions . among the other two patients with loosening , one patient could perform his daily activities with a cane and refused to undergo re - revision surgery . the other patient was recently recommended revision tha , but did not undergo the procedure under the time constraints of this study . one of the 4 patients in whom osteolysis without loosening was detected underwent a head and liner change with allogeneic bone grafting into the acetabular bone defect . the remaining 3 patients who showed osteolysis around the well - fixed implant did not complain of any discomfort and were followed - up without any further operations . , the 15-year survival rate was 28.2% ( 95% confidence interval [ ci ] , 8.3 to 52.6 ) and 56.0% ( 95% ci , 27.3 to 77.2 ) , respectively ( fig . statistical analysis did not reveal that any variables among age at revision tha , gender , bmi , bony defect severity , bubble sign , bearings used for revision tha , and revision type had a significant association with osteolysis or loosening after revision tha . metallosis from a catastrophic failure of a pe liner is a devastating condition . during our study period , the revision rate was 30.4% after revision tha , which was very high compared to the re - revision rate of other recent studies reporting the results of revision tha in the presence or absence of metallosis.19,20 ) moreover , the incidences of osteolysis and loosening after revision tha in this study were 56.5% and 39.1% , respectively , and they were also higher than those in other studies.20 ) this study has some limitations that need to be mentioned . first , there was no control group that included patients who had only catastrophic liner wear without metallosis , for comparing and determining the exact effect of metallosis on the results of revision tha . however , this study demonstrated that severe metallosis resulting from catastrophic liner wear by itself is a risk factor for the failure of revision tha . second , we could not identify any factors which affect the results of revision tha following severe metallosis . twenty - three cases do not constitute an adequate sample size to allow for analysis of other factors that may affect the results of revision tha . quantification of metallosis or metal wear might give further information on the volumetric effect of the metal problem . in fact , it is difficult to define the margin of metallosis because there is grossly invisible metallic invasion . during revision tha , all of the hips showed severe metallosis classified as grade iii in this study . bony defects before revision tha were also severe , and acetabular defects were noted in all 23 hips . in contrast , chang et al.7 ) reported osteolysis around the acetabular cup in only 24 of 31 hips ( 77.4% ) demonstrating metallosis , and only 4 of these hips showed a type iii acetabular defect . their results were not in agreement with those of the current study , in which 15 of 23 hips showed type iii acetabular bony defect.14 ) this may be related to the mechanism of metallosis . it is known that liner dissociation , catastrophic liner wear , or direct impingement between components , such as shell and stem or shell and screw , can cause metallosis.7,12 ) among them , pe liner wear usually does not cause symptoms that are different from those of liner dissociation or restricted motion due to impingement . metallosis from catastrophic liner wear can continue to progress , generating many pe and metal wear particles . pe wear particles are known to cause an inflammatory reaction and subsequent osteolysis.21 ) moreover , metal wear particles and pe wear particles can exert a synergistic effect.10 ) metallosis due to catastrophic liner wear leads to osteolysis and loosening . the problems caused by metal wear particles have been identified recently due to failed metal - on - metal tha and resurfacing tha.22,23,24,25 ) pseudotumor is one such problem . pseudotumor was first described as a soft - tissue mass associated with the metal - on - metal resurfacing implant , and it is neither malignant nor infective in nature.25 ) substantial necrosis and a heavy macrophage infiltrate were noted around the pseudotumor . the adaptive immune response also plays an important role in the development of pseudotumor.23 ) direct cytotoxicity of metal particles and immunologic reaction play an important role in problems related to metal ions.22,24 ) the increased incidence of osteolysis after revision tha following severe metallosis could be partially explained by the same phenomenon . in conclusion , the survival rate of revision tha in patients with metallosis following a catastrophic failure of a pe liner was found to be low . a substantial amount of pe wear debris and the infiltration of metallic wear particles in the periprosthetic tissues might lead to progressive bone loss and implant loosening , even after revision tha . the patient , in whom this catastrophic condition is detected during revision surgery , should be informed that he / she has to regularly attend follow - up visits due to a high possibility of additional revision surgeries .