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Analysis of removed autophor ceramic-on-ceramic components
Analysis of Removed Autophor Ceramicon-Ceramic Components
F r e d e r i c k J. K u m m e r , P h D , S t e v e n A. S t u c h i n , M D , a n d V i c t o r H. F r a n k e l , M D , P h D
Abstract: Six Autophor alumina ceramic total hip arthroplasty components (5 removed for stem loosening and 1 for cup loosening) were evaluated to determine the nature and extent of wear by direct measurement, scanning electron microscopy of wear debris, and histology. Component implantation averaged 29 months (range, 8-54 months). All components had evidence of marked wear, including gross loss of material, which increased with the duration of implantation. Key words: wear, alumina, ceramic, Autophor.
ening. The implantation times ranged from 8 to 54 months. The 8 - m o n t h sample was removed due to recurrent dislocation caused by poor cup placement; the 54-month sample exhibited a loose acetabular c o m p o n e n t after trauma. The others were removed because of stem loosening; these patients had firmly fixed acetabular components at revision. Patient data were obtained and radiographs used to determine implant placement, since factors such as vertical cup placement (>45 °) and significant leg length discrepancies have been implicated as contributing to wear (1, 4). These data are summarized in Table 1. Samples of synovium and adjacent tissues removed at surgery were submitted for pathologic analysis for the 24-, 51-, and 54-month samples. Implants were examined in the laboratory using the following techniques to quantify wear. Any bone and/or tissue adhering to the cup was removed and prepared by dehydration and coated with Au-Pd for SEM and EDAX analysis. Implants were photographically documented and the a m o u n t of wear quantified by direct measurement or the use o f a profilometer. The actual implant was coated with AuPd and examined by SEM. Samples of the removed synovial tissue were macerated with bleach and filtered to obtain wear debris for SEM and EDAX analysis.
Removed alumina ceramic-on-ceramic total hip arthroplasw components have exhibited clinical wear: surface scoring, gross loss of material, and the generation of wear debris (2, 6). This has been interpreted as a result of inferior-quality ceramics, improper device placement, and/or nonphysiologic loading (1, 4). Laboratory test results have not been conclusive. One study recommends against the use of alumina bearing surfaces (3), while another demonstrates 20 times less wear than against polyethylene (8). We examined the clinical wear response of the Autophor ceramic-on-ceramic system by analysis of retrieved prostheses and surrounding tissue.
Materials and Method Six removed A u t o p h o r components (head and acetabulum) were obtained from removals for loosFrom the Department of Bioengineering, ttospital for Joint Diseases Orthopaedic Institute, New York, New York.
Based in part on a presentation given at the Society for Biomaterials Symposium on Retrieval and Analysis of Surgical Implants and Biomaterials, August 12-14, 1988, Snowbird, Utah. Reprint requests: Frederick J. Kummero PhD, Department of Bioengineering,Hospital for Joint Diseases Orthopaedic Institute, 301 East 71st Street, New York, NY 10003.
29
30
The Journal of Arthroplasty Vol. 5 No. 1 March 1990 T a b l e l. Autophor Samples Examined
Time To Removal (Months)
Patient Age and Sex
9
60 F 5! M
24*
62 M
8
31"
Diagnosis
Leg Length Discrepancy (ram)
Cup Angle (o)
Stem Position
Reason For Removal
0 - 5
60 51
Neutral Neutral
OA
+2
54
Neutral
Dislocations Pain--cup and stem loose Pain--loose stem
OA
0
34
Valgus
Pain--loose stem
Protrusio Revision
51
56 M
OA
+ 15
47
Valgus
Pain-loose stem
54
38 F
OA
+ 15
60
Valgus
Pelvic fracture, causing loose cup
Wear/Gap Size Between Components Several small craters Slight areas of surface dullness "'Horseshoe" wear pattern, < 0.1 mm "Horseshoe" wear pattern, 0.1 mm "Horseshoe" wear pattern, 0.5 mm Gross--3.0 mm
* Same patient. OA, osteoarthritis.
Results
T h e r a d i o g r a p h s of these patients s h o w e d firmly fixed a c e t a b u l a r c o m p o n e n t s (except at 54 m o n t h s ) . All of the i m p l a n t s e x h i b i t e d surface d a m a g e , inc l u d i n g m i s s i n g f r a g m e n t s d u e to i n s e r t i o n or rem o v a l , a b r a s i o n of the a c e t a b u l a r c o m p o n e n t rim b y the metallic stem, a n d distinct " h o r s e s h o e " - s h a p e d
areas of surface roughness on the head with a corresponding region on the acetabulum. Measurements of wear ranged from less than 10 p.m to greater than 3 n u n total between the components for the 5 4 - m o n t h s a m p l e (Fig. 1). At r e m o v a l , a greyish disc o l o r a t i o n of a d j a c e n t tissues, p a r t i c u l a r l y i n the capsule a n d s y n o v i u m , w a s n o t e d i n t w o s a m p l e s (51 a n d 54 m o n t h s ) . The s y n o v i u m w a s h y p e r t r o p h i c a n d h i g h l y discolored. The histologic sections
Fig. 1. Ceramic head removed at 54 months, showing 1.6 m m of wear (distance to original surface).
Ceramic-on-Ceramic Components
showed areas of inflammation, with multiple histocytes and fibrosis as well as the presence of numerous dark particles (Fig. 2). Scanning electron microscopy of weight-bearing surfaces showed marked cratering in the least w o m surfaces and complete destruction of the polished surface in areas of roughness (Fig. 3). This surface appeared granular in nature, with asperities of a size ( 3 - 5 p.m) similar to that of the original alumina grains. Numerous particles (c. 5 p.m in diameter) noted in the wear debris proved, on EDAX analysis, to contain A1 as the main constituent; adjacent tissues demonstrated no detectable Co, Cr, or Mo.
Discussion As indicated in Table 1, the severity of wear increased with duration of implantation. In view of the size of particles seen in the tissue and the correspondingly sized defects in the wear surfaces, grain delamination and consequent third-body wear appears to be a likely mechanism, as has been previously proposed for inferior-quality ceramics (6).
•
Kummer et al.
31
However, the Autophor ceramic is high-purity and high-density, with small and uniform grain size, and thus has shown superior w e a r properties in laboratory testing (8). Most of the samples were removed because of stem loosening, which could have produced high local loading due to abrupt changes in the cup-head positions. Unlike metal-on-plastic systems, ceramic-on-ceramic is unforgiving of impact or nonuniform loading, due to the brittle nature of the ceramic. It should be noted that the sample that exhibited the most severe wear was removed because of cup loosening due to sudden trauma; both the cup and stem were not previously loose, but the cup position was somewhat vertical, which can produce high local loading on the cup edge leading to accentuated wear (6). The tissue response might not be solely due to the alumina particles; metallic wear and the presence of residual material from previous operations could also be factors. However, in two samples, a significant a m o u n t of particulate alumina debris was generated and no metallic contamination was detected with EDAX. The tissue response to the wear particles may not be benign; it has been implicated in bone resorption (5) and associated with sarcoma (7).
Fig. 2. Adjacent synovial lissue at 54 months, showing numerous wear particles. (tt&E, x 200)
O j
Jo
k
jP
:b o
D
,h, w -
, ,qltt~
;~ ~:.'~t~, ~¸
.
.~~',~,~.__ ~ -P"d
,.
,
,1~.
o
i
Fig. 3. Ceramic head surfaces at 8 months (A) and 31 months (B). ( x 1,000) Original surface is completely smooth.
32
Ceramic-on-Ceramic Components
Conclusion There is a potential for clinical w e a r of A u t o p h o r c e r a m i c - o n - c e r a m i c c o m p o n e n t s . As has b e e n previously s h o w n (1), loss of prosthetic stability, such as loosening or malposition, can lead 1o increased wear. This w e a r can be m o r e significant a n d o c c u r m o r e rapidly t h a n that seen with the usual metalo n - U H M W p o l y e t h y l e n e devices, due to the different n a t u r e of the materials and the resulting w e a r m e c h anisms (3).
References 1. Boutin P, Christel P, Dorlot J-M et al: The use of dense alumina-alumina ceramic combination in total hip replacement. J Biomed Mater Res 22:1203, 1988 2. Cameron H, Loehr J, Fornaiser V: Early clinical trials with a ceramic total hip prosthesis. Orthop Rev 12:45, 1986
•
Kummer et al.
33
3. Galante JO, Rostoker W: Wear in total hip prostheses. Acta Orthop Scand (suppl 145) 1973 4. Griss P, Heimke G: Biocompatibility of high density alumina and its applications in orthopaedic surgery, p. 155. In Biocompatibility of clinical implant materials, vol. 1. CRC Press, Boca Raton, FL, 1981 5. Plenk H, Locke H, Punzet G e t al: Tissue reactions to debris from bioceramic endoprostheses, p. 431. In Winter GD, Leray JL, de Groot K (et al): Evaluation of biomaterials: advances in biomaterials, vol. 1. Wiley, Chichester, 1980 6. Plitz W, Griss P: Clinical, histo-morphological, and material related observations on removed alumina-ceramic hip joint components, p. 131. In Implant retrieval: material and biological analysis. NBS Special Publication 601, U.S. Government Printing Office, Washington, D.C., 1981 7. Ryu RKN: Soft tissue sarcoma associated with aluminum oxide ceramic total hip arthroplasty: a case report. Clin Orthop 216:207, 1987 8. Semlitch M, Lehmann M, Weter H et ah New prospects for a prolonged functional life-span of artificial hip joints by using the material combination polyethylene/ aluminum oxide ceramic/metal. J Biomed Mater Res 11:537, 1977
F r e d e r i c k J. K u m m e r , P h D , S t e v e n A. S t u c h i n , M D , a n d V i c t o r H. F r a n k e l , M D , P h D
Abstract: Six Autophor alumina ceramic total hip arthroplasty components (5 removed for stem loosening and 1 for cup loosening) were evaluated to determine the nature and extent of wear by direct measurement, scanning electron microscopy of wear debris, and histology. Component implantation averaged 29 months (range, 8-54 months). All components had evidence of marked wear, including gross loss of material, which increased with the duration of implantation. Key words: wear, alumina, ceramic, Autophor.
ening. The implantation times ranged from 8 to 54 months. The 8 - m o n t h sample was removed due to recurrent dislocation caused by poor cup placement; the 54-month sample exhibited a loose acetabular c o m p o n e n t after trauma. The others were removed because of stem loosening; these patients had firmly fixed acetabular components at revision. Patient data were obtained and radiographs used to determine implant placement, since factors such as vertical cup placement (>45 °) and significant leg length discrepancies have been implicated as contributing to wear (1, 4). These data are summarized in Table 1. Samples of synovium and adjacent tissues removed at surgery were submitted for pathologic analysis for the 24-, 51-, and 54-month samples. Implants were examined in the laboratory using the following techniques to quantify wear. Any bone and/or tissue adhering to the cup was removed and prepared by dehydration and coated with Au-Pd for SEM and EDAX analysis. Implants were photographically documented and the a m o u n t of wear quantified by direct measurement or the use o f a profilometer. The actual implant was coated with AuPd and examined by SEM. Samples of the removed synovial tissue were macerated with bleach and filtered to obtain wear debris for SEM and EDAX analysis.
Removed alumina ceramic-on-ceramic total hip arthroplasw components have exhibited clinical wear: surface scoring, gross loss of material, and the generation of wear debris (2, 6). This has been interpreted as a result of inferior-quality ceramics, improper device placement, and/or nonphysiologic loading (1, 4). Laboratory test results have not been conclusive. One study recommends against the use of alumina bearing surfaces (3), while another demonstrates 20 times less wear than against polyethylene (8). We examined the clinical wear response of the Autophor ceramic-on-ceramic system by analysis of retrieved prostheses and surrounding tissue.
Materials and Method Six removed A u t o p h o r components (head and acetabulum) were obtained from removals for loosFrom the Department of Bioengineering, ttospital for Joint Diseases Orthopaedic Institute, New York, New York.
Based in part on a presentation given at the Society for Biomaterials Symposium on Retrieval and Analysis of Surgical Implants and Biomaterials, August 12-14, 1988, Snowbird, Utah. Reprint requests: Frederick J. Kummero PhD, Department of Bioengineering,Hospital for Joint Diseases Orthopaedic Institute, 301 East 71st Street, New York, NY 10003.
29
30
The Journal of Arthroplasty Vol. 5 No. 1 March 1990 T a b l e l. Autophor Samples Examined
Time To Removal (Months)
Patient Age and Sex
9
60 F 5! M
24*
62 M
8
31"
Diagnosis
Leg Length Discrepancy (ram)
Cup Angle (o)
Stem Position
Reason For Removal
0 - 5
60 51
Neutral Neutral
OA
+2
54
Neutral
Dislocations Pain--cup and stem loose Pain--loose stem
OA
0
34
Valgus
Pain--loose stem
Protrusio Revision
51
56 M
OA
+ 15
47
Valgus
Pain-loose stem
54
38 F
OA
+ 15
60
Valgus
Pelvic fracture, causing loose cup
Wear/Gap Size Between Components Several small craters Slight areas of surface dullness "'Horseshoe" wear pattern, < 0.1 mm "Horseshoe" wear pattern, 0.1 mm "Horseshoe" wear pattern, 0.5 mm Gross--3.0 mm
* Same patient. OA, osteoarthritis.
Results
T h e r a d i o g r a p h s of these patients s h o w e d firmly fixed a c e t a b u l a r c o m p o n e n t s (except at 54 m o n t h s ) . All of the i m p l a n t s e x h i b i t e d surface d a m a g e , inc l u d i n g m i s s i n g f r a g m e n t s d u e to i n s e r t i o n or rem o v a l , a b r a s i o n of the a c e t a b u l a r c o m p o n e n t rim b y the metallic stem, a n d distinct " h o r s e s h o e " - s h a p e d
areas of surface roughness on the head with a corresponding region on the acetabulum. Measurements of wear ranged from less than 10 p.m to greater than 3 n u n total between the components for the 5 4 - m o n t h s a m p l e (Fig. 1). At r e m o v a l , a greyish disc o l o r a t i o n of a d j a c e n t tissues, p a r t i c u l a r l y i n the capsule a n d s y n o v i u m , w a s n o t e d i n t w o s a m p l e s (51 a n d 54 m o n t h s ) . The s y n o v i u m w a s h y p e r t r o p h i c a n d h i g h l y discolored. The histologic sections
Fig. 1. Ceramic head removed at 54 months, showing 1.6 m m of wear (distance to original surface).
Ceramic-on-Ceramic Components
showed areas of inflammation, with multiple histocytes and fibrosis as well as the presence of numerous dark particles (Fig. 2). Scanning electron microscopy of weight-bearing surfaces showed marked cratering in the least w o m surfaces and complete destruction of the polished surface in areas of roughness (Fig. 3). This surface appeared granular in nature, with asperities of a size ( 3 - 5 p.m) similar to that of the original alumina grains. Numerous particles (c. 5 p.m in diameter) noted in the wear debris proved, on EDAX analysis, to contain A1 as the main constituent; adjacent tissues demonstrated no detectable Co, Cr, or Mo.
Discussion As indicated in Table 1, the severity of wear increased with duration of implantation. In view of the size of particles seen in the tissue and the correspondingly sized defects in the wear surfaces, grain delamination and consequent third-body wear appears to be a likely mechanism, as has been previously proposed for inferior-quality ceramics (6).
•
Kummer et al.
31
However, the Autophor ceramic is high-purity and high-density, with small and uniform grain size, and thus has shown superior w e a r properties in laboratory testing (8). Most of the samples were removed because of stem loosening, which could have produced high local loading due to abrupt changes in the cup-head positions. Unlike metal-on-plastic systems, ceramic-on-ceramic is unforgiving of impact or nonuniform loading, due to the brittle nature of the ceramic. It should be noted that the sample that exhibited the most severe wear was removed because of cup loosening due to sudden trauma; both the cup and stem were not previously loose, but the cup position was somewhat vertical, which can produce high local loading on the cup edge leading to accentuated wear (6). The tissue response might not be solely due to the alumina particles; metallic wear and the presence of residual material from previous operations could also be factors. However, in two samples, a significant a m o u n t of particulate alumina debris was generated and no metallic contamination was detected with EDAX. The tissue response to the wear particles may not be benign; it has been implicated in bone resorption (5) and associated with sarcoma (7).
Fig. 2. Adjacent synovial lissue at 54 months, showing numerous wear particles. (tt&E, x 200)
O j
Jo
k
jP
:b o
D
,h, w -
, ,qltt~
;~ ~:.'~t~, ~¸
.
.~~',~,~.__ ~ -P"d
,.
,
,1~.
o
i
Fig. 3. Ceramic head surfaces at 8 months (A) and 31 months (B). ( x 1,000) Original surface is completely smooth.
32
Ceramic-on-Ceramic Components
Conclusion There is a potential for clinical w e a r of A u t o p h o r c e r a m i c - o n - c e r a m i c c o m p o n e n t s . As has b e e n previously s h o w n (1), loss of prosthetic stability, such as loosening or malposition, can lead 1o increased wear. This w e a r can be m o r e significant a n d o c c u r m o r e rapidly t h a n that seen with the usual metalo n - U H M W p o l y e t h y l e n e devices, due to the different n a t u r e of the materials and the resulting w e a r m e c h anisms (3).
References 1. Boutin P, Christel P, Dorlot J-M et al: The use of dense alumina-alumina ceramic combination in total hip replacement. J Biomed Mater Res 22:1203, 1988 2. Cameron H, Loehr J, Fornaiser V: Early clinical trials with a ceramic total hip prosthesis. Orthop Rev 12:45, 1986
•
Kummer et al.
33
3. Galante JO, Rostoker W: Wear in total hip prostheses. Acta Orthop Scand (suppl 145) 1973 4. Griss P, Heimke G: Biocompatibility of high density alumina and its applications in orthopaedic surgery, p. 155. In Biocompatibility of clinical implant materials, vol. 1. CRC Press, Boca Raton, FL, 1981 5. Plenk H, Locke H, Punzet G e t al: Tissue reactions to debris from bioceramic endoprostheses, p. 431. In Winter GD, Leray JL, de Groot K (et al): Evaluation of biomaterials: advances in biomaterials, vol. 1. Wiley, Chichester, 1980 6. Plitz W, Griss P: Clinical, histo-morphological, and material related observations on removed alumina-ceramic hip joint components, p. 131. In Implant retrieval: material and biological analysis. NBS Special Publication 601, U.S. Government Printing Office, Washington, D.C., 1981 7. Ryu RKN: Soft tissue sarcoma associated with aluminum oxide ceramic total hip arthroplasty: a case report. Clin Orthop 216:207, 1987 8. Semlitch M, Lehmann M, Weter H et ah New prospects for a prolonged functional life-span of artificial hip joints by using the material combination polyethylene/ aluminum oxide ceramic/metal. J Biomed Mater Res 11:537, 1977