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The Burch-Schneider antiprotrusio cage in acetabular revision surgery
The Journal of Arthroplasty Vol. 15 No. 8 2000
The Burch-Schneider Antiprotrusio Cage in Acetabular Revision Surgery A Mean Follow-up of 12 Years Stephan W. Wachtl, MD, Maximilien Jung, MD, Roland P. Jakob, MD, and Emanuel Gautier, MD
Abstract: A total of 38 acetabular revisions using a Burch-Schneider antiprotrusio cage in 37 patients (18 women and 19 men), with a mean age at surgery of 75 years (range, 55– 88 years), were evaluated retrospectively with a mean follow-up of 12 years (range, 8 –21 years). In 2 cases with total hip dislocation and in 1 case with a deep infection, revision of the antiprotrusio cages was required. Defining every revision of the antiprotrusio cage as the endpoint of survivorship, the antiprotrusio cage showed a survival rate of 92% after 21 years. Clinical evaluation of the surviving patients showed a mean Harris hip score of 76 points (range, 20 –96). Radiologic evaluation revealed that 1 antiprotrusio cage was loose and that 4 femoral stems were loose. The Burch-Schneider antiprotrusio cage compares favorably with other devices with regard to long-term implant survival rate. Key words: BurchSchneider antiprotrusio cage, revision total hip arthroplasty.
Severe segmental or cavitary deficiency of pelvic bone stock is a major problem in the increasing number of patients who require revision of a failed hip arthroplasty. A variety of techniques have been proposed for acetabular reconstruction after loss of acetabular bone stock [1,2] as well as a variety of reinforcement rings [3,4]. The use of acetabular reinforcement rings in acetabular revision surgery first was proposed in the mid-1970s. The antiprotrusio cage originally was designed by Burch in 1974 [5] and was modified slightly by Schneider in 1975 [6,7]. The purpose of this retrospective study
was to evaluate the long-term results of acetabular revision surgery using the Burch-Schneider antiprotrusio cage, with a minimum follow-up of 8 years.
Materials and Methods From January 1977 to December 1992, 38 acetabular revisions using the Burch-Schneider antiprotrusio cage were performed on 37 patients (18 women and 19 men), with a mean age at revision surgery of 75 years (range, 55– 88 years). The right hip was operated on in 21 cases and the left hip in 17 cases. Indication for initial arthroplasty was avascular necrosis of the femoral head in 3 cases, osteoarthrosis in 29 cases, and post-traumatic osteoarthrosis in 6 cases. In 34 hips, revision was necessary for loosening of a primary total hip arthroplasty; in 3, for loosening of a first revision; and in 1, for loosening of a second revision. The mean time between the initial arthroplasty and the inser-
From the Department of Orthopaedic Surgery, Hoˆpital cantonal, Fribourg, Switzerland. Submitted February 24, 2000; accepted July 15, 2000. No benefits or funds were received in support of this study. Reprint requests: Stephan W. Wachtl, MD, Department of Orthopaedic Surgery, Hoˆpital cantonal, CH-1708 Fribourg, Switzerland. Copyright © 2000 by Churchill Livingstone威 0883-5403/00/1508-0002$10.00/0 doi:10.1054/arth.2000.17942
959
960 The Journal of Arthroplasty Vol. 15 No. 8 December 2000 tion of the antiprotrusio cage was 12 years (range, 1.2–23 years). On the acetabular side, a Freeman double cup was noted in 2 cases; an Eichler cup, in 3 cases; and a standard cemented polyethylene cup, in 33 cases. On the femoral side, a Freeman double cup was noted in 2 cases; a cemented Mu¨ller straight stem, in 6 cases; and a cemented Mu¨ller curved stem, in 30 cases. Bone loss before the insertion of the antiprotrusio cage was classified according to the method of D’Antonio et al [8]. There was 1 hip with a segmental loss, 34 hips with combined segmental and cavitary deficiencies, and 3 hips with a pelvic discontinuity. The opposite side was not operated on in 19 hips. Eleven hips on the opposite side had a situation after primary total hip arthroplasty, and 8 hips had a situation after revision arthroplasty. The operation was done with the patient lying in a supine position, using a lateral approach with a trochanteric osteotomy. The loose prosthesis was removed. The acetabulum was prepared, and bone defect was filled with morcellized allograft. The antiprotrusio cage was adapted to the acetabular cavity and the surrounding bone. The distal flange was anchored into the ischium or fixed to it with 2 screws. The proximal flange was fixed to the outside of the ilium with 3 to 6 6.5-mm AO screws. An antiprotrusio cage of small size was implanted in 11 hips, and a large cage was implanted in 27 hips. A 44-mm outer-diameter polyethylene socket was cemented into place in 11 hips; a 48-mm socket, in 8 hips; and a 50-mm socket, in 19 hips. The femur was prepared, and the femoral prosthesis was introduced in the femur. A cemented Mu¨ller curved stem was used in 2 cases; a noncemented Wagner stem, in 14 cases; and a cemented Mu¨ller straight stem, in 21 cases. In 1 case, the original stem was stable and not refixed. The prosthesis was reduced, the greater trochanter was replaced with a doublewire cerclage, and the wound was closed in layers. The patient was mobilized with partial weight bearing for 3 months. Revision was defined by replacement of the antiprotrusio cage. Reoperation was defined as every surgical procedure conducted on the affected hip, excluding replacement of the antiprotrusio cage. Exchange of the polyethylene socket was not considered as a revision of the cage but as a reoperation. At follow-up, the patient was examined clinically and radiologically. Clinical results were assessed using the Harris hip score [9]. The need of pain medication, leg-length discrepancy, and the existence of a Trendelenburg sign were recorded. The anteroposterior radiograph of the pelvis
taken at follow-up was compared with radiographs taken after the implantation of the antiprotrusio cage. Vertical and horizontal acetabular migration was assessed by measuring the vertical distance from the center of the cup to the interteardrop line and the horizontal distance from the center of the cup to the ipsilateral teardrop [10]. Polyethylene socket inclination was evaluated as the angle formed between the interteardrop line and a line joining the lateral end of the socket to the medial end of the socket [11]. Radiolucent lines between the antiprotrusio cage and the bone were recorded on the basis of the 3 acetabular zones, described by DeLee and Charnley [12], to which 2 zones were added. The first, called zone 0, was defined to be next to the proximal flange of the antiprotrusio cage, and the second, called zone 4, was defined to be next to the distal flange. The presence of breakage of screws fixing the cage to the ilium was recorded. An antiprotrusio cage was considered to be radiologically loose if it migrated ⬎5 mm, in the presence of a continuous radiolucency and in the presence of screw breakage. The femoral component was assessed for osteolysis using the zonal system of Gruen et al [13]. Stem subsidence was assessed by measuring the distance from the center of the femoral head to the most medial point on the lesser trochanter [14]. Definite loosening was indicated if there had been subsidence of ⬎5 mm and in the presence of continuous demarcation around the stem. A Wagner stem was considered to be loose only on the basis of a continuous demarcation because subsidence of Wagner stems is common. Heterotopic bone formation was graded according to the classification of Brooker et al [15]. A Kaplan-Meier survivorship curve, with corresponding SEM, was calculated with failure defined according to 3 endpoints: revision, reoperation, or death of the patient.
Results Three antiprotrusio cages had to be revised. Two cages had to be exchanged because of recurrent prosthetic dislocation resulting from malposition of the cage with excessive anteversion, and 1 hip required a Girdlestone procedure because of deep infection. Mean time between implantation of the cage and revision was 3 months (range, 19 days– 8.5 months). Three patients died within the first 19 days after the implantation of the antiprotrusio cage: 2 patients died from heart failure, and 1 patient died from sepsis.
Burch-Schneider Antiprotrusio Cage •
We noted 8 complications that required a reoperation. Two cases with recurrent dislocations owing to excessive antetorsion of the Wagner stem were treated with an exchange of the stem. Three nonunions of the greater trochanter, 1 with a recurrent prosthetic dislocation, were treated with a re-osteosynthesis of the greater trochanter. One deep infection required de´bridement and suction drains. One periprosthetic fracture was treated by implantation of a Wagner stem. One stem loosening required reoperation 19 years after implantation of the antiprotrusio cage. In this patient, the polyethylene socket was exchanged because of excessive wear. The cage was stable. No other polyethylene socket needed to be changed. Mean time between implantation of the antiprotrusio cage and reoperation was 3 years (range, 15 days–19 years). From the implantation of the antiprotrusio cage until the final follow-up, 17 patients died from causes unrelated to surgery, with a mean time between surgery and death of 7 years (range, 2–14 years). Two patients could not be traced and probably died. The last review of these 2 patients was at 9 months and 3.5 years. Cumulative survival of the antiprotrusio cage was 92% (SEM 4.3) after 21 years, including deep infection. The probability of a hip not requiring reoperation within 21 years was 38% (SEM 27.5). Cumulative patient survival was 29% (SEM 11.8) after 21 years (Fig. 1). Consequently, 16 patients could be controlled with a mean follow-up of 12 years (range, 8 –21 years). At follow-up, the mean Harris hip score was 76
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points (range, 20 –96). The mean pain score was 37 points (range, 10 – 44); mean gait score, 21 (range, 4 –30); mean activities score, 10 (range, 3–14); mean deformities score, 3 (range, 0 – 4); and mean range of motion score, 4 (range, 1–5). The mean leg-length discrepancy was 0.5 cm (range, 0 –2.5 cm). The Trendelenburg sign was positive in 6 patients. Two patients needed nonsteroidal antiinflammatory medication, and 1 patient needed an opioid-like medication because of constant hip pain. Radiologic analysis (Fig. 2) showed that the mean inclination of the polyethylene socket was 40° (range, 26°– 60°) after implantation of the antiprotrusio cage and that the mean inclination at follow-up was 41° (range, 26°– 60°). The mean proximal and medial migration of the antiprotrusio cage was 1 mm (range, 0 –5 mm) and 1.5 mm (range, 0 –10 mm). A radiolucent line surrounding the whole antiprotrusio cage was not observed. Nonprogressive radiolucency was seen in zone 0 in 3 hips, in zone 1 in 1 hip, and in zone 4 in 2 hips. Broken screws were seen in 1 case. All the bone– grafts appeared to have incorporated. One antiprotrusio cage was considered to be loose. The mean subsidence of the femoral stem was 4 mm (range, 0 –13 mm). A continuous demarcation was noted in 3 hips. Nonprogressive radiolucencies in zones 1 and 7 were observed in 5 hips. Four stems were considered to be loose. Heterotopic ossification of grade 1 was noted in 2 hips and of grade 3 in 1 hip.
Discussion
Fig. 1. Survival curve with 3 different endpoints: revision of the antiprotrusio cage, reoperation of hip without exchange of the antiprotrusio cage, or death of the patient. ( ), revision; (—䉫—), reoperation; ( ), patient death.
Reconstruction of severe acetabular bone deficiencies is 1 of the main problems in revision total hip arthroplasty. The use of acetabular reinforcement rings combined with bone– graft has gained wide acceptance [16]. Short-term and midterm results of the BurchSchneider antiprotrusio cage have been reported. Rosson and Schatzker [17] reviewed 20 BurchSchneider antiprotrusio cages with a mean follow-up of 5 years. None of the hips required revision. The mean Harris hip score was 81. Berry and Mu¨ller [6] reported on 42 antiprotrusio cages with a mean follow-up of 5 years. There was failure because of sepsis in 5 hips (12%) and aseptic loosening in 5 other hips (12%). Peters et al [18] reported in a series of 28 antiprotrusio cages a cumulative survival rate of 100% at 5 years. Gill et al [19] reported a series of 84 operations in 78 patients with a mean follow-up of 8.5 years. Of these 84 hips, 9 antiprotrusio cages had to be re-
962 The Journal of Arthroplasty Vol. 15 No. 8 December 2000
Fig. 2. (A) Implantation of an Eichler ring because of primary protrusio osteoarthrosis. (B) Loosening 9 years after implantation. (C) Revision by implantation of an antiprotrusio cage. (D) Ten years after implantation with excellent integration of the cage. The femoral stem was exchanged after a periprosthetic femoral fracture occurred 7 years after the revision surgery.
vised; 20 patients were excluded. A good-to-excellent result was noted in 92% of the remaining patients. Our study presents the fate of all patients oper-
ated on with a minimum follow-up of 8 years. The fact that more than half of the patients had died at follow-up shows that the antiprotrusio cage was reserved for old patients with severe acetabular
Burch-Schneider Antiprotrusio Cage •
bone deficiencies. In cases of less extended bone loss, other implants, such as a cemented polyethylene cup, an Eichler ring, a Mu¨ller support ring, or a reinforcement ring with hook, were used in the period under review. Despite good long-term results and despite good clinical results of the surviving patients, the relative high mortality rate (3 of 38 patients) and the relative high incidence of postoperative infection (2 patients) exemplifies the risk of a patient whose bone stock deficiency requires the implantation of an antiprotrusio cage for revision hip arthroplasty. The Burch-Schneider antiprotrusio cage was compared directly with other implants in major acetabular revision surgery by Bo¨hm and Banzhaf [20] in a mixed series of 103 hips. Defined as revision of the acetabular component for any cause including infection, survival was 83% for the antiprotrusio cage after 11 years; 84%, for the Mu¨ller acetabular roof reinforcement ring after 13 years; and 69%, for the Harris-Galante cup after 8 years. Using revision because of aseptic loosening as an endpoint, the antiprotrusio cage had a 94% survival after 11 years; the Mu¨ller acetabular roof reinforcement ring, 89% after 13 years; and the HarrisGalante cup, 73% after 8 years. The present study confirms the good short-term and midterm results of the antiprotrusio cage and shows its long-term survival rate.
References 1. Papagelopoulos PJ, Lewallen DG, Cabenela ME, et al: Acetabular reconstruction using bipolar endoprosthesis and bone grafting in patients with severe bone deficiency. Clin Orthop 314:170, 1995 2. MacKenzie JR, Callaghan JJ, Pederson DR, et al: Areas of contact and extent of gaps with implantation of oversized acetabular components in total hip arthroplasty. Clin Orthop 298:127, 1994 3. Haentjens P, de Boeck H, Handelberg F, et al: Cemented acetabular reconstruction with the Mu¨ller support ring: a minimum five-year clinical and roentgenographic follow-up study. Clin Orthop 290:225, 1993 4. Oh I, Harris WH: Design concepts, indications and surgical technique for use of the protrusio shell. Clin Orthop 162:175, 1982 5. Burch HB: Eine Anti-Protrusions-Schale. p 60. In Burch HB (ed): Die orthopa¨dische Chirurgie. Bern, Hans Huber Verlag, 1978
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6. Berry DJ, Mu¨ller ME: Revision arthroplasty using an anti-protrusio cage for massive acetabular bone deficiency. J Bone Joint Surg Br 74:711, 1992 7. Schneider R: Die Armierung der Pfanne bei der Totalendoprothese der Hu¨fte. Unfallheilkunde 83:482, 1980 8. D’Antonio JA, Capello WN, Borden LS, et al: Classification and management of acetabular abnormalities in total hip arthroplasty. Clin Orthop 243:126, 1989 9. Harris WH: Traumatic arthritis of the hip after dislocation and acetabular fracture: treatment by mold arthroplasty. J Bone Joint Surg Am 51:737, 1969 10. Nunn D, Freeman MAR, Hill PF, et al: The measurement of migration of the acetabular component of hip prostheses. J Bone Joint Surg Br 71:629, 1989 11. Kobayashi S, Eftekhar NS, Terayama K, et al: Risk factors affecting radiological failure of the socket in primary Charnley low friction arthroplasty: a 10 to 20 year followup study. Clin Orthop 306:84, 1994 12. DeLee JG, Charnley J: Radiological demarcation of cemented sockets in total hip replacement. Clin Orthop 121:20, 1976 13. Gruen TA, McNeice GM, Amstutz HC: “Mode of failure” of cemented stem-type femoral components: a radiographic analysis of loosening. Clin Orthop 141:17, 1979 14. Malchau H, Ka¨rrholm J, Wang YX, et al: Accuracy of migration analysis in hip arthroplasty: digitized and conventional radiography, compared to radiostereometry in 51 patients. Acta Orthop Scand 66:418, 1995 15. Brooker AF, Bowerman JW, Robinson RA, et al: Ectopic ossification following total hip replacement: incidence and a method of classification. J Bone Joint Surg Am 55:1629, 1973 16. Zehntner MK, Ganz R: Midterm results (5.5–20 years) of acetabular allograft reconstruction with the acetabular reinforcement ring during total hip revision. J Arthroplasty 9:469, 1994 17. Rosson J, Schatzker J: The use of reinforcement rings to reconstruct deficient acetabula. J Bone Joint Surg Br 74:716, 1992 18. Peters CL, Curtain M, Samuelson KM: Acetabular revision with the Burch-Schneider anti-protrusio cage and cancellous allograft bone. J Arthroplasty 10:307, 1995 19. Gill TJ, Sledge JB, Mu¨ller ME: The Burch-Schneider anti-protrusio cage in revision total hip arthroplasty: indications, principles and long-term results. J Bone Joint Surg Br 80:946, 1998 20. Bo¨hm P, Banzhaf S: Acetabular revision with allograft bone: 103 revisions with 3 reconstruction alternatives, followed for 0.3–13 years. Acta Orthop Scand 70:240, 1999
The Burch-Schneider Antiprotrusio Cage in Acetabular Revision Surgery A Mean Follow-up of 12 Years Stephan W. Wachtl, MD, Maximilien Jung, MD, Roland P. Jakob, MD, and Emanuel Gautier, MD
Abstract: A total of 38 acetabular revisions using a Burch-Schneider antiprotrusio cage in 37 patients (18 women and 19 men), with a mean age at surgery of 75 years (range, 55– 88 years), were evaluated retrospectively with a mean follow-up of 12 years (range, 8 –21 years). In 2 cases with total hip dislocation and in 1 case with a deep infection, revision of the antiprotrusio cages was required. Defining every revision of the antiprotrusio cage as the endpoint of survivorship, the antiprotrusio cage showed a survival rate of 92% after 21 years. Clinical evaluation of the surviving patients showed a mean Harris hip score of 76 points (range, 20 –96). Radiologic evaluation revealed that 1 antiprotrusio cage was loose and that 4 femoral stems were loose. The Burch-Schneider antiprotrusio cage compares favorably with other devices with regard to long-term implant survival rate. Key words: BurchSchneider antiprotrusio cage, revision total hip arthroplasty.
Severe segmental or cavitary deficiency of pelvic bone stock is a major problem in the increasing number of patients who require revision of a failed hip arthroplasty. A variety of techniques have been proposed for acetabular reconstruction after loss of acetabular bone stock [1,2] as well as a variety of reinforcement rings [3,4]. The use of acetabular reinforcement rings in acetabular revision surgery first was proposed in the mid-1970s. The antiprotrusio cage originally was designed by Burch in 1974 [5] and was modified slightly by Schneider in 1975 [6,7]. The purpose of this retrospective study
was to evaluate the long-term results of acetabular revision surgery using the Burch-Schneider antiprotrusio cage, with a minimum follow-up of 8 years.
Materials and Methods From January 1977 to December 1992, 38 acetabular revisions using the Burch-Schneider antiprotrusio cage were performed on 37 patients (18 women and 19 men), with a mean age at revision surgery of 75 years (range, 55– 88 years). The right hip was operated on in 21 cases and the left hip in 17 cases. Indication for initial arthroplasty was avascular necrosis of the femoral head in 3 cases, osteoarthrosis in 29 cases, and post-traumatic osteoarthrosis in 6 cases. In 34 hips, revision was necessary for loosening of a primary total hip arthroplasty; in 3, for loosening of a first revision; and in 1, for loosening of a second revision. The mean time between the initial arthroplasty and the inser-
From the Department of Orthopaedic Surgery, Hoˆpital cantonal, Fribourg, Switzerland. Submitted February 24, 2000; accepted July 15, 2000. No benefits or funds were received in support of this study. Reprint requests: Stephan W. Wachtl, MD, Department of Orthopaedic Surgery, Hoˆpital cantonal, CH-1708 Fribourg, Switzerland. Copyright © 2000 by Churchill Livingstone威 0883-5403/00/1508-0002$10.00/0 doi:10.1054/arth.2000.17942
959
960 The Journal of Arthroplasty Vol. 15 No. 8 December 2000 tion of the antiprotrusio cage was 12 years (range, 1.2–23 years). On the acetabular side, a Freeman double cup was noted in 2 cases; an Eichler cup, in 3 cases; and a standard cemented polyethylene cup, in 33 cases. On the femoral side, a Freeman double cup was noted in 2 cases; a cemented Mu¨ller straight stem, in 6 cases; and a cemented Mu¨ller curved stem, in 30 cases. Bone loss before the insertion of the antiprotrusio cage was classified according to the method of D’Antonio et al [8]. There was 1 hip with a segmental loss, 34 hips with combined segmental and cavitary deficiencies, and 3 hips with a pelvic discontinuity. The opposite side was not operated on in 19 hips. Eleven hips on the opposite side had a situation after primary total hip arthroplasty, and 8 hips had a situation after revision arthroplasty. The operation was done with the patient lying in a supine position, using a lateral approach with a trochanteric osteotomy. The loose prosthesis was removed. The acetabulum was prepared, and bone defect was filled with morcellized allograft. The antiprotrusio cage was adapted to the acetabular cavity and the surrounding bone. The distal flange was anchored into the ischium or fixed to it with 2 screws. The proximal flange was fixed to the outside of the ilium with 3 to 6 6.5-mm AO screws. An antiprotrusio cage of small size was implanted in 11 hips, and a large cage was implanted in 27 hips. A 44-mm outer-diameter polyethylene socket was cemented into place in 11 hips; a 48-mm socket, in 8 hips; and a 50-mm socket, in 19 hips. The femur was prepared, and the femoral prosthesis was introduced in the femur. A cemented Mu¨ller curved stem was used in 2 cases; a noncemented Wagner stem, in 14 cases; and a cemented Mu¨ller straight stem, in 21 cases. In 1 case, the original stem was stable and not refixed. The prosthesis was reduced, the greater trochanter was replaced with a doublewire cerclage, and the wound was closed in layers. The patient was mobilized with partial weight bearing for 3 months. Revision was defined by replacement of the antiprotrusio cage. Reoperation was defined as every surgical procedure conducted on the affected hip, excluding replacement of the antiprotrusio cage. Exchange of the polyethylene socket was not considered as a revision of the cage but as a reoperation. At follow-up, the patient was examined clinically and radiologically. Clinical results were assessed using the Harris hip score [9]. The need of pain medication, leg-length discrepancy, and the existence of a Trendelenburg sign were recorded. The anteroposterior radiograph of the pelvis
taken at follow-up was compared with radiographs taken after the implantation of the antiprotrusio cage. Vertical and horizontal acetabular migration was assessed by measuring the vertical distance from the center of the cup to the interteardrop line and the horizontal distance from the center of the cup to the ipsilateral teardrop [10]. Polyethylene socket inclination was evaluated as the angle formed between the interteardrop line and a line joining the lateral end of the socket to the medial end of the socket [11]. Radiolucent lines between the antiprotrusio cage and the bone were recorded on the basis of the 3 acetabular zones, described by DeLee and Charnley [12], to which 2 zones were added. The first, called zone 0, was defined to be next to the proximal flange of the antiprotrusio cage, and the second, called zone 4, was defined to be next to the distal flange. The presence of breakage of screws fixing the cage to the ilium was recorded. An antiprotrusio cage was considered to be radiologically loose if it migrated ⬎5 mm, in the presence of a continuous radiolucency and in the presence of screw breakage. The femoral component was assessed for osteolysis using the zonal system of Gruen et al [13]. Stem subsidence was assessed by measuring the distance from the center of the femoral head to the most medial point on the lesser trochanter [14]. Definite loosening was indicated if there had been subsidence of ⬎5 mm and in the presence of continuous demarcation around the stem. A Wagner stem was considered to be loose only on the basis of a continuous demarcation because subsidence of Wagner stems is common. Heterotopic bone formation was graded according to the classification of Brooker et al [15]. A Kaplan-Meier survivorship curve, with corresponding SEM, was calculated with failure defined according to 3 endpoints: revision, reoperation, or death of the patient.
Results Three antiprotrusio cages had to be revised. Two cages had to be exchanged because of recurrent prosthetic dislocation resulting from malposition of the cage with excessive anteversion, and 1 hip required a Girdlestone procedure because of deep infection. Mean time between implantation of the cage and revision was 3 months (range, 19 days– 8.5 months). Three patients died within the first 19 days after the implantation of the antiprotrusio cage: 2 patients died from heart failure, and 1 patient died from sepsis.
Burch-Schneider Antiprotrusio Cage •
We noted 8 complications that required a reoperation. Two cases with recurrent dislocations owing to excessive antetorsion of the Wagner stem were treated with an exchange of the stem. Three nonunions of the greater trochanter, 1 with a recurrent prosthetic dislocation, were treated with a re-osteosynthesis of the greater trochanter. One deep infection required de´bridement and suction drains. One periprosthetic fracture was treated by implantation of a Wagner stem. One stem loosening required reoperation 19 years after implantation of the antiprotrusio cage. In this patient, the polyethylene socket was exchanged because of excessive wear. The cage was stable. No other polyethylene socket needed to be changed. Mean time between implantation of the antiprotrusio cage and reoperation was 3 years (range, 15 days–19 years). From the implantation of the antiprotrusio cage until the final follow-up, 17 patients died from causes unrelated to surgery, with a mean time between surgery and death of 7 years (range, 2–14 years). Two patients could not be traced and probably died. The last review of these 2 patients was at 9 months and 3.5 years. Cumulative survival of the antiprotrusio cage was 92% (SEM 4.3) after 21 years, including deep infection. The probability of a hip not requiring reoperation within 21 years was 38% (SEM 27.5). Cumulative patient survival was 29% (SEM 11.8) after 21 years (Fig. 1). Consequently, 16 patients could be controlled with a mean follow-up of 12 years (range, 8 –21 years). At follow-up, the mean Harris hip score was 76
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points (range, 20 –96). The mean pain score was 37 points (range, 10 – 44); mean gait score, 21 (range, 4 –30); mean activities score, 10 (range, 3–14); mean deformities score, 3 (range, 0 – 4); and mean range of motion score, 4 (range, 1–5). The mean leg-length discrepancy was 0.5 cm (range, 0 –2.5 cm). The Trendelenburg sign was positive in 6 patients. Two patients needed nonsteroidal antiinflammatory medication, and 1 patient needed an opioid-like medication because of constant hip pain. Radiologic analysis (Fig. 2) showed that the mean inclination of the polyethylene socket was 40° (range, 26°– 60°) after implantation of the antiprotrusio cage and that the mean inclination at follow-up was 41° (range, 26°– 60°). The mean proximal and medial migration of the antiprotrusio cage was 1 mm (range, 0 –5 mm) and 1.5 mm (range, 0 –10 mm). A radiolucent line surrounding the whole antiprotrusio cage was not observed. Nonprogressive radiolucency was seen in zone 0 in 3 hips, in zone 1 in 1 hip, and in zone 4 in 2 hips. Broken screws were seen in 1 case. All the bone– grafts appeared to have incorporated. One antiprotrusio cage was considered to be loose. The mean subsidence of the femoral stem was 4 mm (range, 0 –13 mm). A continuous demarcation was noted in 3 hips. Nonprogressive radiolucencies in zones 1 and 7 were observed in 5 hips. Four stems were considered to be loose. Heterotopic ossification of grade 1 was noted in 2 hips and of grade 3 in 1 hip.
Discussion
Fig. 1. Survival curve with 3 different endpoints: revision of the antiprotrusio cage, reoperation of hip without exchange of the antiprotrusio cage, or death of the patient. ( ), revision; (—䉫—), reoperation; ( ), patient death.
Reconstruction of severe acetabular bone deficiencies is 1 of the main problems in revision total hip arthroplasty. The use of acetabular reinforcement rings combined with bone– graft has gained wide acceptance [16]. Short-term and midterm results of the BurchSchneider antiprotrusio cage have been reported. Rosson and Schatzker [17] reviewed 20 BurchSchneider antiprotrusio cages with a mean follow-up of 5 years. None of the hips required revision. The mean Harris hip score was 81. Berry and Mu¨ller [6] reported on 42 antiprotrusio cages with a mean follow-up of 5 years. There was failure because of sepsis in 5 hips (12%) and aseptic loosening in 5 other hips (12%). Peters et al [18] reported in a series of 28 antiprotrusio cages a cumulative survival rate of 100% at 5 years. Gill et al [19] reported a series of 84 operations in 78 patients with a mean follow-up of 8.5 years. Of these 84 hips, 9 antiprotrusio cages had to be re-
962 The Journal of Arthroplasty Vol. 15 No. 8 December 2000
Fig. 2. (A) Implantation of an Eichler ring because of primary protrusio osteoarthrosis. (B) Loosening 9 years after implantation. (C) Revision by implantation of an antiprotrusio cage. (D) Ten years after implantation with excellent integration of the cage. The femoral stem was exchanged after a periprosthetic femoral fracture occurred 7 years after the revision surgery.
vised; 20 patients were excluded. A good-to-excellent result was noted in 92% of the remaining patients. Our study presents the fate of all patients oper-
ated on with a minimum follow-up of 8 years. The fact that more than half of the patients had died at follow-up shows that the antiprotrusio cage was reserved for old patients with severe acetabular
Burch-Schneider Antiprotrusio Cage •
bone deficiencies. In cases of less extended bone loss, other implants, such as a cemented polyethylene cup, an Eichler ring, a Mu¨ller support ring, or a reinforcement ring with hook, were used in the period under review. Despite good long-term results and despite good clinical results of the surviving patients, the relative high mortality rate (3 of 38 patients) and the relative high incidence of postoperative infection (2 patients) exemplifies the risk of a patient whose bone stock deficiency requires the implantation of an antiprotrusio cage for revision hip arthroplasty. The Burch-Schneider antiprotrusio cage was compared directly with other implants in major acetabular revision surgery by Bo¨hm and Banzhaf [20] in a mixed series of 103 hips. Defined as revision of the acetabular component for any cause including infection, survival was 83% for the antiprotrusio cage after 11 years; 84%, for the Mu¨ller acetabular roof reinforcement ring after 13 years; and 69%, for the Harris-Galante cup after 8 years. Using revision because of aseptic loosening as an endpoint, the antiprotrusio cage had a 94% survival after 11 years; the Mu¨ller acetabular roof reinforcement ring, 89% after 13 years; and the HarrisGalante cup, 73% after 8 years. The present study confirms the good short-term and midterm results of the antiprotrusio cage and shows its long-term survival rate.
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