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Revision total hip arthroplasty with shelf bulk allografts
The Journal of ArthroplastyVol. 11 No. 1 1996
Revision Total Hip Arthroplasty With Shelf Bulk Allografts A Long-term Follow-up Study E l s a y e d M o r s i , M B B C H , M S ( O r t h ) , D o n G a r b u z , M D , a n d A l l a n E. G r o s s , M D
Abstract: A series of 29 shelf (< 50% of the acetabulum) structural allografts were
done in conjunction with acetabular revision with a minimum follow-up period of 5 years (average, 7.1 years). At the latest follow-up examination, 86% of the hips were successful both clinically and radiologically. Only four patients required further surgery, with two of these being revised with no additional grafts. The use of bulk allograft in conjunction with acetabular revision is supported, provided that at least 50% support of the cup can be obtained with host-bone. This type of reconstruction provides support for the cup and restores anatomy, leg length, and bone stock should future revision be necessary. Key words: shelf bulk allografts, revision.
With the increasing n u m b e r of total hip arthroplasties (THAs) being done, the n u m b e r requiring revision surgery is also increasing. Revision hip surgery on the acetabular side is a challenging procedure, especially w h e n associated with severe bone stock loss. This loss of bone stock is an ever-increasing problem, especially in the multiply revised patient. Loss of bone stock is due to both wear particles and abrasive action of b o n e - c e m e n t . 1-6 Restoration of bone stock m a y be necessary to provide suitable bone support for the cup. In addition, bone-grafting will help to restore a n a t o m y and leg lengths, making future revisions possible. Also, bone-grafting makes the use of conventional implants possible. The use of bulk allografts to achieve the above goals continues to be controversial. There are only two long-term studies in the literature that address the problem of bulk allografting in acetabular reconstruction; one supports allografts, v whereas the other discourages their use.8
It is our purpose to look at a group of patients whose acetabular defects are all of a similar magnitude. The patients in this study all had shelf (minor column) defects, meaning that they had loss of part of the rim plus the corresponding acetabular wall but less t h a n 50% of the acetabulum. All underw e n t acetabular revision with bulk allografts. Only patients with a m i n i m u m follow-up period of 5 years are included in this review.
Materials and Methods From 1983 to 1993, 58 acetabular revisions with bulk shelf allografts were performed at M o u n t Sinai Hospital. From this group, 35 hips had a mini m u m follow-up period of 5 years. We were able to obtain complete clinical and radiologic data on 29 hips performed in 28 patients (1 patient was bilateral). These 29 hips are the basis of this study. Six patients could not be completely followed up at to the time of this review due to death unrelated to their THA (2 cases) and failure to contact t h e m (4 cases). The average follow-up period was 7.1 years (range, 5-12 years). There were 25 w o m e n and 3 men. The average age was 53.2 years (range, 32-73 years). The average n u m b e r of previous
From Mount Sinai Hospital, Toronto, Ontario, Canada. Reprint requests: A. E. Gross, MD, Division of Orthopaedic Surgery, University of Toronto, Mount Sinai Hospital, 600 University Avenue, Suite 476, Toronto, Ontario, Canada, M5G IX5.
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operations was 2.2 (range, 1-4). The initial diagnoses w e r e congenital hip dysplasia in 15 cases, osteoarthritis in 6 cases, r h e u m a t o i d arthritis in 3 cases, avascular necrosis in 3 cases, and Perthes' disease in 1 case. The surgical technique, b o n e banking technique, and postoperative management have been addressed in detail previously. 9 D o n o r selection c o n f o r m e d to the guidelines r e c o m m e n d e d by the Musculoskeletal Council of the A m e r i c a n Association of Tissue Banks. 10 The surgical a p p r o a c h was transgluteal in 12 cases and transtrochanteric in 17. D o n o r allografts included 21 m a l e femoral heads, 3 acetabulums, 3 p r o x i m a l tibias, and 2 distal femoral condyles. Allografts w e r e shaped and fixed to h o s t - b o n e w i t h standard 4 . 5 - r a m AO malleolar or 6 . 5 - m m AO cancellous screws with washers directed in an oblique or vertical direction. The graft is rigidly fixed and t h e n gently r e a m e d until c o n g r u e n t with the bost acetabulum. We leave the subchondral b o n e of the graft intact by not r e a m i n g t h r o u g h to cancellous bone. If the subchondral b o n e is r e a m e d a w a y d o w n to cancellous bone, t h e n the cup should be cemented. A n y cancellous surfaces of the graft should be opposed to h o s t - b o n e and not soft tissues, w h i c h m a y lead to resorption. Twelve c e m e n t e d and 17 uncem e n t e d acetabular c o m p o n e n t s w e r e used. Eighteen cases h a d c o n c o m i t a n t femoral revision, with nine of these requiring p r o x i m a l femoral allografts. All of the patients w e r e followed b o t h clinically a n d radiographically. A modified Harris hip score was used for clinical assessment. 9 Radiographic review looked at several parameters. Allografts w e r e assessed for u n i o n to h o s t - b o n e as evidenced by trabecular bridging of h o s t - d o n o r interface, fracture fragmentation, and radiolucent lines. Resorption of allograft was m e a s u r e d in b o t h horizontal a n d vertical axes 9 and was graded as m i n o r (<1/3 of graft), m o d e r a t e (1/3-1/2 of graft), or severe (>1/2 of graft) 8 The screw position was m e a s u r e d as the angle of the screw relative to a horizontal line b e t w e e n teardrops. Failure was defined as inability to increase the hip score by 20 points, n e e d for reoperation, or radiographic evidence of loosening. 1~ The acetabular c o m p o n e n t s were considered to be loose if there was evidence of migration, fracture of the c e m e n t mantle, ~2 or a c o n t i n u o u s circumferential radiolocency m o r e t h a n 1 m m wide at the b o n e - c e m e n t interface. 13
Results At the latest f o l l o w - u p e x a m i n a t i o n (mean, 7.1 years), only 4 of 29 cases w e r e failures, giving a
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success rate of 86%. The average preoperative hip score was 44.5 (range, 19-73), a n d the average postoperative score was 79.5 (range, 60-97). Of these four failures, one was for deep infection and was treated with excision arthroplasty. One patient had m o d e r a t e resorption of the graft with painful cup loosening requiring rerevision at 5.5 postoperative years w i t h o u t additional graft. One patient with r h e u m a t o i d arthritis h a d graft resorption a n d f r a g m e n t a t i o n w i t h cup dislocation 6 m o n t h s after surgery. This patient u n d e r w e n t rerevision but e n d e d up with a low clinical score. The fourth failure h a d rerevision at a n o t h e r institution for cup loosening at 3.5 postoperative years, but the graft was intact. In two of the four cases that required revision, the graft was salvaged. On rerevision, the grafts w e r e f o u n d intact a n d united to h o s t - b o n e so that sufficient b o n e stock allowed acetabular rerevision using c e m e n t e d cups in b o t h cases w i t h o u t the n e e d for additional grafting. Before surgery, 4 patients h a d equal leg lengths, 8 had a leg-length discrepancy (LED) less t h a n 2 cm, and 16 h a d an LLD b e t w e e n 2 and 5 cm. After surgery, the LLD was less t h a n 2 cm in 27 of 28 patients, with 15 patients having equal leg lengths. Radiographically, all but one of the allografts united to the h o s t - b o n e . This n o n u n i o n was in one of the patients w h o failed at 6 postoperative m o n t h s . In addition to n o n u n i o n , she h a d fracture f r a g m e n t a t i o n of the allograft with dislocation of the prothesis. No other grafts d e m o n s t r a t e d fracture or f r a g m e n t a t i o n in this group. In terms of allograft resorption, nine cases s h o w e d no resorption. M i n o r resorption was seen in 17 cases a n d was m a i n l y in the n o n - w e i g h t - b e a r i n g lateral portion of the graft. In three cases, m o d e r a t e resorption was seen in b o t h the horizontal and the vertical planes. Two of these three patients w e r e failures due to associated cup loosening. The third patient h a d a s y m p t o m a t i c m o d e r a t e resorption 9 years after surgery. Radiolucent lines w e r e seen in only six cases. Three of these h a d lucent lines less t h a n 2 m m in zone 3 only. Two cases h a d lucent lines less t h a n 2 m m in zone 2 and one patient h a d lucent lines of only 1 m m in all three zones. N o n e of these cases with lucent lines w e r e progressive at a foll o w - u p period of at least 2 years. The average screw angle was 45 ° (range, 20°-85°). These positions w e r e not changed at the last follow-up e x a m i n a t i o n except in one case. This latter case h a d fracture of one screw 1.5 years after surgery, with no h a r m f u l effects after 7 postoperative years. This screw h a d a n angle of 20 ° . Apart f r o m the three aseptic failures, there w e r e one deep infection that necessitated excision arthroplasty and one case w i t h superficial infection
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successfully treated with appropriate antibiotics. There was one case of p u l m o n a r y embolism successfully treated medically.
Discussion Revision THA with structural acetabular allograft is k n o w n to be successful in short- to moderatefollow-up studies. 14-18 There is only one study in the literature that reports long-term follow-up results on the use of bulk allografts in revision THA. 8 Harris and his group reported failure rates of 32% at an average follow-up period of 6 years and 47% at an average tollow-up period of 10 years. 19 Harris et al. currently r e c o m m e n d placing the cup at a high hip center to avoid the use of bulk allografts. 19,20 There are advantages to anatomic placem e n t of the cup, 21-23 but placing the cup at a high hip center has b e e n s h o w n to be an acceptable alternative with correction of LLD by a long neck or calcar replacement prosthesis. 2o Also, the use of large u n c e m e n t e d cups supported mainly by h o s t - b o n e has b e e n s h o w n to be successful in revision acetabular arthroplasty.X4, a5 Using a larger c o m p o n e n t m a y make it possible to revise some of these cases w i t h o u t bulk grafts and w i t h o u t moving the hip center very far superiorly.24, 25 In our series, only 1 of 28 patients had a postoperative LLD greater t h a n 2 cm; however, in a study supporting the principle of a high hip center for reconstruction of an acetabulum with deficient bone stock, Russotti and Harris had only 5 of 34 patients with LLDs greater t h a n 1.5 cm. 20 In addition to correcting leg length, use of structural allograft restores bone stock should future revision be nec-
essary. Indeed, of Harris and colleagues' eight symptomatic failures using structural allograft for revision, six had successful rerevision at the anatomic level with no additional bone-graft, s Furthermore, two recent concerns have been brought up with regard to high hip center: first is the high dislocation rate, and second is the high rate of femoral loosening. Harris and co-workers reported a 6% dislocation rate w h e n using a high hip center in revision surgery. 26 Femoral loosening rates of 20 to 50% have b e e n reported w h e n acetabular cups were placed proximally.20,26-28 In contrast, w h e n shelf grafts were used to restore anatomic position as in our series, n o n e of these complications were found. Paprosky and Magnus in 1994 published their follow-up study on bulk acetabular allograft with a low failure rate of 4 % at an average followup period of 6 years. 7 In this study, we addressed a group of patients with similar acetabular defects (minor c o l u m n or shelf defects involving < 50% of the acetabulum). All had reconstruction with bulk allograft so that the cup could be placed in its anatomic position. Our success rate was 86% at an average follow-up period of 7 years. In our series, only one patient had graft resorption, fragmentation, and cup dislocation 6 m o n t h s after surgery. This patient had r h e u m a t o i d arthritis, which m a y affect the integrity and u n i o n of the bulk graft due to the poor bone quality of these patients. Our results suggest that w h e n using bulk allograft, one can expect u n i o n to h o s t - b o n e and only minor resorption mainly in the non-weight-bearing lateral portion of the graft (Fig. 1). Technical factors are important for success. Fixation of the graft should be done with compression screws oriented in an oblique to vertical direction. The graft should
Fig. 1. (A,B) Radiographs of a 56-year-old woman with a loose acetabular component and deficient bone stock. (Figure
continues)
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Fig. 1. (Continued) (C) Two weeks after revision surgery with minor column allograft fixed by two screws directed obliquely. (D) Seven years after revision surgery with complete incorporation of the graft and resorption of the lateral non-weight-bearing part.
make contact with as large an area of h o s t - b o n e as possible to e n h a n c e union. As well, to ensure a high rate of success, one should attempt to make contact of the cup (cemented or uncemented) with at least 50% host-bone. This is in agreement with a 1994 article by Hooten et al., w h o showed that w h e n the cup was supported by more than 50% h o s t - b o n e , a good clinical and radiologic o u t c o m e resulted. 29 If possible, the structural allograft material should be strong bone, for example, male femoral heads or part of an acetabulum.
Conclusion The goals of revision surgery on the pelvic side are to provide support for the cup, restore n o r m a l a n a t o m y and leg length, and restore bone stock should future revision be required. Our results with bulk allografting in revision THA for m i n o r c o l u m n defects involving less than 50% of the a c e t a b u l u m accomplish these goals. In addition, a success rate of 86% at an average follow-up period of 7 years in this challenging problem s h o w e d that acetabular revision with structural allograft can be successful in the long term.
References 1. Freeman MAR, Bradley GW, Revell PA: Observation upon the interface between bone and polymethylmethacrylate cement. J Bone Joint Surg 64B:489, 1982 2. Goldring SR, Schiller AL, Roelke M e t ah The synovial-like membrane at the bone cement interface in loose total hip replacements and its proposed role in bone lysis. J Bone Joint Surg 65A:575, 1983
3. Goodman SB, Schatzker J, Sumner-Smith G e t ah The effect of polymethylmethacrylate on bone: an experimental study. Arch Orthop Trauma Surg 104: 150, 1985 4. Howie D, Oakeshott R, Manthy B et al: Bone resorption in the presence of polyethylene wear particles. J Bone Joint Surg 69B:165, 1987 5. Jasty M J, Floyd WE, Schiller AL et ah Localized osteolysis in stable, non-septic total hip replacement. J Bone Joint Surg 68A:912, 1986 6. Pazzaglia UE, Ceciliani L, Wilkinson MJ et ah Involvement of metal particles in loosening of metal-plastic total hip prosthesis. Arch Orthop Trauma Surg 104:164, 1985 7. Paprosky WG, Magnus RE: Principles of bone grafting in revision total hip arthroplasty: acetabular technique. Clin Orthop 298:147, 1994 8. Jasty M J, Harris WH: Salvage total hip reconstruction in patients with major acetabular bone deficiency using structural femoral head allografts. J Bone Joint Surg 72B:63, 1990 9. Gross AE, Allan ED, Catre M e t al: Bone grafting in hip replacement surgery: the pelvic side. Clin Orthop North Am 24:679, 1993 10. American Association of Tissue Banks: Guidelines for the banking of musculoskeletal tissue. Am Assoc Tissue Banks Newslett 3:2, 1979 11. DeLee JG, Charnley J: Radiographic demarcation of cemented sockets in total hip replacement. Clin Orthop 121:20, 1976 12. Harris WH, Peneberg BL: Further follow-up on socket fixation using a metal-backed acetabular component for total hip replacement: a minimum ten-year follow-up study. J Bone Joint Surg 69A: I140, 1987 13. Hodgkinson JP, Shelley P, Wroblewski BM: The correlation between the roentgenographic appearance and operative findings at the bone-cement junction of the socket in Charnley low friction arthroplasties. Clin Orthop 228:i05, 1988
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14. Convery FR, Convery MM, Devine SD et ah Acetabular augmentation in primary and revision total hip arthroplasty with cemented prosthesis. Clin Orthop 252:167, 1990 15. Harris WH, Crothers O, Indong OH: Total hip replacement and femoral-head bone-grafting for severe acetabular deficiency in adults. J Bone Joint Surg 59A:752, 1977 16. Knight JL, Fujii K, Atwater R et ah Bone-grafting for acetabular deficiency during primary and revision total hip arthroplasty: a radiographic and clinical analysis. J Arthroplasty 8:371, 1993 17. Pollock FH, Whiteside LA: The fate of massive allografts in total hip acetabular revision surgery. J Arthroplasty 7:271, 1992 18. Samuelson KM, Freeman MAR, Levach B et al: Homograft bone in revision acetabular arthroplasty. J Bone Joint Surg 70B:367, 1988 19. Kwong LM, Jasty M J, Harris WH: High failure rate of bulk femoral head allografts in total hip acetabular reconstruction at 10 years. J Arthroplasty 8:341, 1993 20. Russotti GM, Harris WH: Proximal placement of the acetabular component in total hip arthroplasty: a long-term follow-up study. J Bone Joint Surg 73A: 587, 1991 21. Callaghan J J, Salvati EA, Pellicci PM et al: Results of revision for mechanical failure after cemented total hip replacement, 1979 to 1982: a two- to five-year follow-up. J Bone Joint Surg 67A:1074, 1985
22. Johnston RC, Brand RA, Crowninshield RD: Reconstruction of the hip: a mathematical approach to determine o p t i m u m geometric relationships. J Bone Joint Surg 61A:639, 1979 23. Ranawat CS, Dorr LD, Inglis AE: Total hip arthroplasty in protrusio acetabuli of rheumatoid arthritis. J Bone Joint Surg 62A:I059, 1980 24. Tanzer M, Drucker D, Jasty M e t ah Revision of the acetabular component with an uncemented Harris-Galante porous-coated prosthesis. J Bone Joint Surg 74A:987, i992 25. Padgett DE, Kull L, Rosenberg A et al: Revision of the acetabular component without cement after total hip arthroplasty. J Bone Joint Surg 75A:663, 1993 26. Schutzer SE Harris WH: Placement of a porous coated acetabular component at a high hip center. Presented at the 58th Annual Meeting of the American Academy of Orthopaedic Surgeons, Anaheim, CA, March 1991 27. Kelley SS: High hip center in revision arthroplasty. J Arthroplasty 9:503, 1994 28. Yoder SA, Brand RA, Pederson DR, O'Gorman TW: Total hip acetabular component position affects component loosening rates. Clin Orthop 228:79, 1988 29. Hooten JP, Engh CA Jr, Engh CA: Failure of structural acetabular allografts in cementless revision hip arthroplasty. J Bone Joint Surg 76B:419, 1994
Revision Total Hip Arthroplasty With Shelf Bulk Allografts A Long-term Follow-up Study E l s a y e d M o r s i , M B B C H , M S ( O r t h ) , D o n G a r b u z , M D , a n d A l l a n E. G r o s s , M D
Abstract: A series of 29 shelf (< 50% of the acetabulum) structural allografts were
done in conjunction with acetabular revision with a minimum follow-up period of 5 years (average, 7.1 years). At the latest follow-up examination, 86% of the hips were successful both clinically and radiologically. Only four patients required further surgery, with two of these being revised with no additional grafts. The use of bulk allograft in conjunction with acetabular revision is supported, provided that at least 50% support of the cup can be obtained with host-bone. This type of reconstruction provides support for the cup and restores anatomy, leg length, and bone stock should future revision be necessary. Key words: shelf bulk allografts, revision.
With the increasing n u m b e r of total hip arthroplasties (THAs) being done, the n u m b e r requiring revision surgery is also increasing. Revision hip surgery on the acetabular side is a challenging procedure, especially w h e n associated with severe bone stock loss. This loss of bone stock is an ever-increasing problem, especially in the multiply revised patient. Loss of bone stock is due to both wear particles and abrasive action of b o n e - c e m e n t . 1-6 Restoration of bone stock m a y be necessary to provide suitable bone support for the cup. In addition, bone-grafting will help to restore a n a t o m y and leg lengths, making future revisions possible. Also, bone-grafting makes the use of conventional implants possible. The use of bulk allografts to achieve the above goals continues to be controversial. There are only two long-term studies in the literature that address the problem of bulk allografting in acetabular reconstruction; one supports allografts, v whereas the other discourages their use.8
It is our purpose to look at a group of patients whose acetabular defects are all of a similar magnitude. The patients in this study all had shelf (minor column) defects, meaning that they had loss of part of the rim plus the corresponding acetabular wall but less t h a n 50% of the acetabulum. All underw e n t acetabular revision with bulk allografts. Only patients with a m i n i m u m follow-up period of 5 years are included in this review.
Materials and Methods From 1983 to 1993, 58 acetabular revisions with bulk shelf allografts were performed at M o u n t Sinai Hospital. From this group, 35 hips had a mini m u m follow-up period of 5 years. We were able to obtain complete clinical and radiologic data on 29 hips performed in 28 patients (1 patient was bilateral). These 29 hips are the basis of this study. Six patients could not be completely followed up at to the time of this review due to death unrelated to their THA (2 cases) and failure to contact t h e m (4 cases). The average follow-up period was 7.1 years (range, 5-12 years). There were 25 w o m e n and 3 men. The average age was 53.2 years (range, 32-73 years). The average n u m b e r of previous
From Mount Sinai Hospital, Toronto, Ontario, Canada. Reprint requests: A. E. Gross, MD, Division of Orthopaedic Surgery, University of Toronto, Mount Sinai Hospital, 600 University Avenue, Suite 476, Toronto, Ontario, Canada, M5G IX5.
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Revision THA With Shelf Bulk AIIografts
operations was 2.2 (range, 1-4). The initial diagnoses w e r e congenital hip dysplasia in 15 cases, osteoarthritis in 6 cases, r h e u m a t o i d arthritis in 3 cases, avascular necrosis in 3 cases, and Perthes' disease in 1 case. The surgical technique, b o n e banking technique, and postoperative management have been addressed in detail previously. 9 D o n o r selection c o n f o r m e d to the guidelines r e c o m m e n d e d by the Musculoskeletal Council of the A m e r i c a n Association of Tissue Banks. 10 The surgical a p p r o a c h was transgluteal in 12 cases and transtrochanteric in 17. D o n o r allografts included 21 m a l e femoral heads, 3 acetabulums, 3 p r o x i m a l tibias, and 2 distal femoral condyles. Allografts w e r e shaped and fixed to h o s t - b o n e w i t h standard 4 . 5 - r a m AO malleolar or 6 . 5 - m m AO cancellous screws with washers directed in an oblique or vertical direction. The graft is rigidly fixed and t h e n gently r e a m e d until c o n g r u e n t with the bost acetabulum. We leave the subchondral b o n e of the graft intact by not r e a m i n g t h r o u g h to cancellous bone. If the subchondral b o n e is r e a m e d a w a y d o w n to cancellous bone, t h e n the cup should be cemented. A n y cancellous surfaces of the graft should be opposed to h o s t - b o n e and not soft tissues, w h i c h m a y lead to resorption. Twelve c e m e n t e d and 17 uncem e n t e d acetabular c o m p o n e n t s w e r e used. Eighteen cases h a d c o n c o m i t a n t femoral revision, with nine of these requiring p r o x i m a l femoral allografts. All of the patients w e r e followed b o t h clinically a n d radiographically. A modified Harris hip score was used for clinical assessment. 9 Radiographic review looked at several parameters. Allografts w e r e assessed for u n i o n to h o s t - b o n e as evidenced by trabecular bridging of h o s t - d o n o r interface, fracture fragmentation, and radiolucent lines. Resorption of allograft was m e a s u r e d in b o t h horizontal a n d vertical axes 9 and was graded as m i n o r (<1/3 of graft), m o d e r a t e (1/3-1/2 of graft), or severe (>1/2 of graft) 8 The screw position was m e a s u r e d as the angle of the screw relative to a horizontal line b e t w e e n teardrops. Failure was defined as inability to increase the hip score by 20 points, n e e d for reoperation, or radiographic evidence of loosening. 1~ The acetabular c o m p o n e n t s were considered to be loose if there was evidence of migration, fracture of the c e m e n t mantle, ~2 or a c o n t i n u o u s circumferential radiolocency m o r e t h a n 1 m m wide at the b o n e - c e m e n t interface. 13
Results At the latest f o l l o w - u p e x a m i n a t i o n (mean, 7.1 years), only 4 of 29 cases w e r e failures, giving a
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success rate of 86%. The average preoperative hip score was 44.5 (range, 19-73), a n d the average postoperative score was 79.5 (range, 60-97). Of these four failures, one was for deep infection and was treated with excision arthroplasty. One patient had m o d e r a t e resorption of the graft with painful cup loosening requiring rerevision at 5.5 postoperative years w i t h o u t additional graft. One patient with r h e u m a t o i d arthritis h a d graft resorption a n d f r a g m e n t a t i o n w i t h cup dislocation 6 m o n t h s after surgery. This patient u n d e r w e n t rerevision but e n d e d up with a low clinical score. The fourth failure h a d rerevision at a n o t h e r institution for cup loosening at 3.5 postoperative years, but the graft was intact. In two of the four cases that required revision, the graft was salvaged. On rerevision, the grafts w e r e f o u n d intact a n d united to h o s t - b o n e so that sufficient b o n e stock allowed acetabular rerevision using c e m e n t e d cups in b o t h cases w i t h o u t the n e e d for additional grafting. Before surgery, 4 patients h a d equal leg lengths, 8 had a leg-length discrepancy (LED) less t h a n 2 cm, and 16 h a d an LLD b e t w e e n 2 and 5 cm. After surgery, the LLD was less t h a n 2 cm in 27 of 28 patients, with 15 patients having equal leg lengths. Radiographically, all but one of the allografts united to the h o s t - b o n e . This n o n u n i o n was in one of the patients w h o failed at 6 postoperative m o n t h s . In addition to n o n u n i o n , she h a d fracture f r a g m e n t a t i o n of the allograft with dislocation of the prothesis. No other grafts d e m o n s t r a t e d fracture or f r a g m e n t a t i o n in this group. In terms of allograft resorption, nine cases s h o w e d no resorption. M i n o r resorption was seen in 17 cases a n d was m a i n l y in the n o n - w e i g h t - b e a r i n g lateral portion of the graft. In three cases, m o d e r a t e resorption was seen in b o t h the horizontal and the vertical planes. Two of these three patients w e r e failures due to associated cup loosening. The third patient h a d a s y m p t o m a t i c m o d e r a t e resorption 9 years after surgery. Radiolucent lines w e r e seen in only six cases. Three of these h a d lucent lines less t h a n 2 m m in zone 3 only. Two cases h a d lucent lines less t h a n 2 m m in zone 2 and one patient h a d lucent lines of only 1 m m in all three zones. N o n e of these cases with lucent lines w e r e progressive at a foll o w - u p period of at least 2 years. The average screw angle was 45 ° (range, 20°-85°). These positions w e r e not changed at the last follow-up e x a m i n a t i o n except in one case. This latter case h a d fracture of one screw 1.5 years after surgery, with no h a r m f u l effects after 7 postoperative years. This screw h a d a n angle of 20 ° . Apart f r o m the three aseptic failures, there w e r e one deep infection that necessitated excision arthroplasty and one case w i t h superficial infection
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successfully treated with appropriate antibiotics. There was one case of p u l m o n a r y embolism successfully treated medically.
Discussion Revision THA with structural acetabular allograft is k n o w n to be successful in short- to moderatefollow-up studies. 14-18 There is only one study in the literature that reports long-term follow-up results on the use of bulk allografts in revision THA. 8 Harris and his group reported failure rates of 32% at an average follow-up period of 6 years and 47% at an average tollow-up period of 10 years. 19 Harris et al. currently r e c o m m e n d placing the cup at a high hip center to avoid the use of bulk allografts. 19,20 There are advantages to anatomic placem e n t of the cup, 21-23 but placing the cup at a high hip center has b e e n s h o w n to be an acceptable alternative with correction of LLD by a long neck or calcar replacement prosthesis. 2o Also, the use of large u n c e m e n t e d cups supported mainly by h o s t - b o n e has b e e n s h o w n to be successful in revision acetabular arthroplasty.X4, a5 Using a larger c o m p o n e n t m a y make it possible to revise some of these cases w i t h o u t bulk grafts and w i t h o u t moving the hip center very far superiorly.24, 25 In our series, only 1 of 28 patients had a postoperative LLD greater t h a n 2 cm; however, in a study supporting the principle of a high hip center for reconstruction of an acetabulum with deficient bone stock, Russotti and Harris had only 5 of 34 patients with LLDs greater t h a n 1.5 cm. 20 In addition to correcting leg length, use of structural allograft restores bone stock should future revision be nec-
essary. Indeed, of Harris and colleagues' eight symptomatic failures using structural allograft for revision, six had successful rerevision at the anatomic level with no additional bone-graft, s Furthermore, two recent concerns have been brought up with regard to high hip center: first is the high dislocation rate, and second is the high rate of femoral loosening. Harris and co-workers reported a 6% dislocation rate w h e n using a high hip center in revision surgery. 26 Femoral loosening rates of 20 to 50% have b e e n reported w h e n acetabular cups were placed proximally.20,26-28 In contrast, w h e n shelf grafts were used to restore anatomic position as in our series, n o n e of these complications were found. Paprosky and Magnus in 1994 published their follow-up study on bulk acetabular allograft with a low failure rate of 4 % at an average followup period of 6 years. 7 In this study, we addressed a group of patients with similar acetabular defects (minor c o l u m n or shelf defects involving < 50% of the acetabulum). All had reconstruction with bulk allograft so that the cup could be placed in its anatomic position. Our success rate was 86% at an average follow-up period of 7 years. In our series, only one patient had graft resorption, fragmentation, and cup dislocation 6 m o n t h s after surgery. This patient had r h e u m a t o i d arthritis, which m a y affect the integrity and u n i o n of the bulk graft due to the poor bone quality of these patients. Our results suggest that w h e n using bulk allograft, one can expect u n i o n to h o s t - b o n e and only minor resorption mainly in the non-weight-bearing lateral portion of the graft (Fig. 1). Technical factors are important for success. Fixation of the graft should be done with compression screws oriented in an oblique to vertical direction. The graft should
Fig. 1. (A,B) Radiographs of a 56-year-old woman with a loose acetabular component and deficient bone stock. (Figure
continues)
Revision THAWith Shelf Bulk AIIografts
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Morsi et al.
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Fig. 1. (Continued) (C) Two weeks after revision surgery with minor column allograft fixed by two screws directed obliquely. (D) Seven years after revision surgery with complete incorporation of the graft and resorption of the lateral non-weight-bearing part.
make contact with as large an area of h o s t - b o n e as possible to e n h a n c e union. As well, to ensure a high rate of success, one should attempt to make contact of the cup (cemented or uncemented) with at least 50% host-bone. This is in agreement with a 1994 article by Hooten et al., w h o showed that w h e n the cup was supported by more than 50% h o s t - b o n e , a good clinical and radiologic o u t c o m e resulted. 29 If possible, the structural allograft material should be strong bone, for example, male femoral heads or part of an acetabulum.
Conclusion The goals of revision surgery on the pelvic side are to provide support for the cup, restore n o r m a l a n a t o m y and leg length, and restore bone stock should future revision be required. Our results with bulk allografting in revision THA for m i n o r c o l u m n defects involving less than 50% of the a c e t a b u l u m accomplish these goals. In addition, a success rate of 86% at an average follow-up period of 7 years in this challenging problem s h o w e d that acetabular revision with structural allograft can be successful in the long term.
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14. Convery FR, Convery MM, Devine SD et ah Acetabular augmentation in primary and revision total hip arthroplasty with cemented prosthesis. Clin Orthop 252:167, 1990 15. Harris WH, Crothers O, Indong OH: Total hip replacement and femoral-head bone-grafting for severe acetabular deficiency in adults. J Bone Joint Surg 59A:752, 1977 16. Knight JL, Fujii K, Atwater R et ah Bone-grafting for acetabular deficiency during primary and revision total hip arthroplasty: a radiographic and clinical analysis. J Arthroplasty 8:371, 1993 17. Pollock FH, Whiteside LA: The fate of massive allografts in total hip acetabular revision surgery. J Arthroplasty 7:271, 1992 18. Samuelson KM, Freeman MAR, Levach B et al: Homograft bone in revision acetabular arthroplasty. J Bone Joint Surg 70B:367, 1988 19. Kwong LM, Jasty M J, Harris WH: High failure rate of bulk femoral head allografts in total hip acetabular reconstruction at 10 years. J Arthroplasty 8:341, 1993 20. Russotti GM, Harris WH: Proximal placement of the acetabular component in total hip arthroplasty: a long-term follow-up study. J Bone Joint Surg 73A: 587, 1991 21. Callaghan J J, Salvati EA, Pellicci PM et al: Results of revision for mechanical failure after cemented total hip replacement, 1979 to 1982: a two- to five-year follow-up. J Bone Joint Surg 67A:1074, 1985
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