- Email: [email protected]
Disassembly and Dislocation of a Bipolar Hip Prosthesis
CASE REPORT
Disassembly and Dislocation of a Bipolar Hip Prosthesis Hsieh-Hsing Lee,1,2 Yung-Chih Lo,2 Leou-Chyr Lin,2* Shing-Sheng Wu1,2 Dislocation of a hip prosthesis is a common complication. In usual cases of hip prosthesis dislocation, the prosthetic femoral head comes out from either the natural acetabular cavity in a bipolar hemiarthroplasty or the prosthetic acetabulum in a total hip arthroplasty. Only a few cases of bipolar hip prosthesis dislocation due to dissociation between the polyethylene and inner head of the prosthesis have been reported. We describe a rare case of disassembly of the inner head from the bipolar outer prosthesis in an osteoarthritic acetabulum. A 72-year-old woman had undergone bipolar hemiarthroplasty due to fracture of the left femoral neck about 10 years previously. Recently, she sustained an injury after falling from a chair, and examinations revealed an unusual disassembly–dislocation of the bipolar hip prosthesis. We classified this failure in our patient as a type II failure, representing extreme varus position of the outer head in the acetabulum, dislocation of the inner head from the outer head, and a detached locking ring around the stem neck. This mechanism of failure as shown in our patient rarely occurs in the bipolar prosthesis of the self-centering system. Osteoarthritic change of the acetabulum would place the outer head in the varus position, increasing wear on the beveled rim by impinging the femoral stem neck and causing dislodgment of the inner locking ring and consequent disassembly–dislocation of the inner head. [J Formos Med Assoc 2008;107(1):84–88] Key Words: bipolar prosthesis, disassembly, dislocation, hemiarthroplasty
hip.7–9 Simple dislocation after primary bipolar hemiarthroplasty can usually be reduced by closed methods, but disassembly of the bipolar components usually requires another operation and possible revision of the prosthesis. We present a rare case of disassembly of the inner head from the polyethylene in a bipolar hip prosthesis and discuss the mechanism of prosthesis failure.
Dislocation of a hip prosthesis is a common complication, which has been fully discussed in several series.1–3 In cases of hip prosthesis dislocation, the prosthetic femoral head usually escapes from the prosthetic acetabulum in a total hip arthroplasty or from the natural acetabular cavity in a bipolar hemiarthroplasty. Only a few cases of bipolar hip prosthesis dislocation between the polyethylene and the inner head of the prosthesis have been reported.4 Little information is available about the rare but serious complication that involves the disassembly of modular components during dislocation5,6 or after closed reduction in the bipolar hemiarthroplasty of the dislocated
Case Report A 72-year-old woman with a femoral neck fracture of the left hip underwent bipolar hemiarthroplasty
©2008 Elsevier & Formosan Medical Association .
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1
Division of Traumatology, Department of Surgery, Municipal Wan-Fang Hospital, Taipei Medical University, and 2 Department of Orthopedics, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan. Received: March 15, 2007 Revised: April 13, 2007 Accepted: June 5, 2007
84
*Correspondence to: Dr Leou-Chyr Lin, Department of Orthopedics, Tri-Service General Hospital, National Defense Medical Center, No. 325, Section 2, Chenggong Road, Neihu District, Taipei 114, Taiwan. E-mail: [email protected]
J Formos Med Assoc | 2008 • Vol 107 • No 1
Disassembly and dislocation of bipolar hip prosthesis
Figure 1. Disassembly–dislocation of the inner head with a detached locking ring around the stem neck (arrow), extreme varus position of the outer head, and osteoarthritic changes of the acetabulum.
about 10 years previously. The femoral stem was collarless in the calcar region and coated with hydroxyapatite in the proximal one third of the stem. The press-fit femoral stem attained stability in the femoral canal from the initial impaction of the implant into the femur, and the size of the outer head was compatible with the patient’s acetabular size. The prosthetic left hip functioned well with little uncomfortable sensation until the patient fell from a chair in December 2005, when she felt a sharp pain, after which she had limited motion in her left hip. On arrival to the emergency department that same day, physical examination revealed no significant abnormality except painful disability over her left hip. X-ray revealed disassembly– dislocation of the inner femoral head from the bipolar hip prosthesis and the outer head located in the varus position (Figure 1). A wire embedded in the polyethylene rim appeared near the implant neck on the X-ray film. Cystic formation with sclerosing change was found in the acetabulum, which indicated osteoarthritic change. No lucent line was evident between the implant stem and the cortical bone over the lower two thirds despite periprosthetic bone resorption in the intertrochanteric region. Revision surgery for total hip arthroplasty was performed several days later using the posterolateral approach along the previous scar over the J Formos Med Assoc | 2008 • Vol 107 • No 1
Figure 2. Retrieved bipolar components with a severely damaged beveled rim over the outer head (left) and a dislodged locking ring (right).
R Figure 3. Postoperative radiograph demonstrates total hip arthroplasty without revision of the stem.
left hip. The inner head had dissociated from the outer head, and marked wear in the beveled rim of the polyethylene with destruction of the inner locking ring was evident (Figure 2). The cartilage of the left acetabulum was worn, and the subchondral bone was devastated with significant cystic formation. Although there was significant osteolysis with bone resorption around the intertrochanteric region (zones I and VII), the femoral stem was still well fixed. Bone grafting with an allograft was applied to the bony defect in the acetabulum and the intertrochanteric region, and total hip arthroplasty without revision of the stem prosthesis was performed (Figure 3). Pathology study revealed foreign body granuloma in the bone and soft tissue, infiltration 85
H.H. Lee, et al
of numerous macrophages, and formation of multinucleated giant cells with polyethylene particles, which may have been responsible for the osteolysis in the intertrochanteric region.
Discussion Prosthetic replacement has been used to treat displaced femoral neck fractures in older patients, and several series have demonstrated predictable pain relief, functional improvement, and a low revision rate.10,11 The results of procedures using the bipolar prosthesis have generally been satisfactory, and early results have been as good as, or better than, unipolar designs.12 Short- to mediumterm follow-up studies comparing unipolar with bipolar bearings demonstrate no clear difference in morbidity, mortality, or functional outcome. Longer term follow-up suggests a lower revision rate with bipolar bearings.1,13,14 The main complication of hip arthroplasty performed on displaced femoral neck fractures is dislocation, which occurs in about 10% of cases on average.2,3 This procedure produces two motion interfaces, one at the outer head–acetabulum interface and the other at the inner head–bearing polyethylene interface. The most frequent complication with a dislocated bipolar hip prosthesis occurs between the acetabulum and the outer head. Disassembly of the bipolar cups is a rare pattern of bipolar prosthesis dislocation. In such rare instances, the mechanism of dislocation should be evaluated, and future revisions in the design of bipolar prostheses considered. The Bateman bipolar hemiarthroplasty has been used since 1985, and disassembly of the Bateman bipolar prosthesis has been reported previously.15–18 The mechanism of failure involves varus loading of the bearing insert and stress concentrated directly over the deep circumferential groove of the superolateral leaflets, rather than impingement of the neck of the femoral stem against the inferomedial leaflets.19 Disassembly of the bipolar prosthesis may also be seen when reducing the dislocated hip.7–9 Another 86
Figure 4. The disassembly–dislocation mechanism of the inner head reveals beveled rim wearing by the impingement of the femoral stem neck with fixed varus position of the outer head in an osteoarthritic acetabulum.
failure mechanism can occur on the bipolar cup of the self-centering system, as shown in our patient. The self-centering system involves the eccentric offset of the bearing centers, in which the outer cup center is located distal to the inner bearing center to prevent varus alignment of the outer head.20 Several studies have reported that the bipolar prosthesis might function as a unipolar prosthesis moving between the interface of the outer head and the acetabulum interface, and that the outer heads tend to be fixed in the extreme varus position when the hip is abducted in some osteoarthritic patients.21,22 The outer head motion might also be limited because of osteophyte formation and granular proliferation around the osteoarthritic acetabulum. Similarly, friction between the outer head and the acetabulum interface might increase because of the loss of acetabular cartilage. These factors would place the outer head in the varus position, increasing wear on the beveled rim of the bearing insert by impinging the femoral stem neck (Figure 4), and causing dislodgment of the inner locking ring and consequent disassembly–dislocation of the J Formos Med Assoc | 2008 • Vol 107 • No 1
Disassembly and dislocation of bipolar hip prosthesis
inner head.20 Several studies have reported the disassembly of bipolar cups with self-centering system. Hasegawa et al reported an 11% rate of disassembly for the Zimmer Bi-Articular Cup.20 Ito et al reported disassembly rates of 4% (1 of 23 hips) for the Osteonics Universal Hip Replacement (UHR®) system and 17% (1 of 6 hips) for the Zimmer Bi-Articular Cup.23 These disassembly problems of bipolar prostheses will persist despite the newest generation of designs of the self-centering systems. Three types of failure of the locking ring have been discussed.20 The detached locking ring around the stem neck without dislocation of the inner head is classified as a type I failure. Dislocation of the inner head with the detached locking ring is classified as a type II failure. Dislocation of the inner head without the detached locking ring is classified as a type III failure. We classified the failure in our patient as a type II failure because it involved an extreme varus position of the outer head in the acetabulum, dislocation of the inner head from the outer head, and a detached locking ring around the stem neck. In our patient, marked polyethylene wear with destruction of the inner locking ring caused osteolysis and erosion of the acetabular weight-bearing surface that eventually led to loosening and migration of the outer cup and hip dislocation of the inner head. This suggests that disassembly– dislocation of the inner head can easily occur during extreme hip adduction and flexion. To determine whether or not disassembly–dislocation of the bipolar prosthesis occurs via the same mechanism in the osteoarthritic acetabulum, thorough clinical examination must be performed. Patients with a well-functioning bipolar hemiarthroplasty should be carefully and regularly followed-up.
Acknowledgments This study was supported in part by the C.Y. Foundation for the Advancement of Education, Sciences and Medicine. J Formos Med Assoc | 2008 • Vol 107 • No 1
References 1. Ong BC, Maurer SG, Aharonoff GB, et al. Unipolar versus bipolar hemiarthroplasty: functional outcome after femoral neck fracture at a minimum of thirty-six months of follow-up. J Orthop Trauma 2002;16:317–22. 2. Sierra RJ, Schleck CD, Cabanela ME. Dislocation of bipolar hemiarthroplasty: rate, contributing factors, and outcome. Clin Orthop 2006;442:230–8. 3. Barnes CL, Berry DJ, Sledge CB. Dislocation after bipolar hemiarthroplasty of the hip. J Arthroplasty 1995;10: 667–9. 4. Corteel J, Putz P. Dislocation–dissociation of a bipolar hip prosthesis. Acta Orthop Belg 1996;62:173–6. 5. Niggemeyer O, Fink B, Ruther W. Dislocation of the polyethylene liner in hip arthroplasty: 6 patients with dislocation within 3 years. Acta Orthop Scand 2002;73: 403–6. 6. Holmes JC, Whalen NJ. Disassembly of the Osteonics bipolar ring when used with a Howmedica femoral head. A report of four cases. J Arthroplasty 1992;7:201–3. 7. Loubignac F, Boissier F. Cup dissociation after reduction of a dislocated hip hemiarthroplasty. Rev Chir Orthop Reparatrice Appar Mot 1997;84:469–72. 8. Georgiou G, Siapkara A, Dimitrakopoulou A, et al. Dissociation of bipolar hemiarthroplasty of the hip after dislocation. A report of five different cases and review of literature. Injury 2006;37:162–8. 9. Star MJ, Colwell CW Jr, Donaldson WF 3rd, et al. Dissociation of modular hip arthroplasty components after dislocation. A report of three cases at differing dissociation levels. Clin Orthop 1992;278:111–5. 10. Bhandari M, Devereaux PJ, Swiontkowski MF, et al. Internal fixation compared with arthroplasty for displaced fractures of the femoral neck. A meta-analysis. J Bone Joint Surg Am 2003;85(A):1673–81. 11. Rogmark C, Carlsson A, Johnell O, et al. Primary hemiarthroplasty in old patients with displaced femoral neck fracture: a 1-year follow-up of 103 patients aged 80 years or more. Acta Orthop Scand 2002;73:605–10. 12. Calder SJ, Anderson GH, Jagger C, et al. Unipolar or bipolar prosthesis for displaced intracapsular hip fracture in octogenarians: a randomised prospective study. J Bone Joint Surg Br 1996;78(B):391–4. 13. Haidukewych GJ, Israel TA, Berry DJ. Long-term survivorship of cemented bipolar hemiarthroplasty for fracture of the femoral neck. Clin Orthop 2002;403:118–26. 14. Cornell CN, Levine D, O’Doherty J, et al. Unipolar versus bipolar hemiarthroplasty for the treatment of femoral neck fractures in the elderly. Clin Orthop 1998;348: 67–71. 15. Herzenberg JE, Harrelson JM, Campbell DC 2nd, et al. Fractures of the polyethylene bearing insert in Bateman bipolar hip prostheses. Clin Orthop 1988;228:88–93.
87
H.H. Lee, et al
16. Barmada R, Mess D. Bateman hemiarthroplasty component disassembly. A report of three cases of highdensity polyethylene failure. Clin Orthop 1987;224: 147–9. 17. Bateman JE, Berenji AR, Bayne O, et al. Long-term results of bipolar arthroplasty in osteoarthritis of the hip. Clin Orthop 1990;251:54–66. 18. Cameron HU, Cha EJ, Jung YB. An examination of factors contributing to failure of bipolar prostheses. Clin Orthop 1989;240:206–9. 19. Krein SW, Chao EY. Biomechanics of bipolar hip endoprostheses. J Orthop Res 1984;2:356–68.
88
20. Hasegawa M, Sudo A, Uchida A. Disassembly of bipolar cup with self-centering system: a report of seven cases. Clin Orthop 2004;425:163–7. 21. Phillips TW. The Bateman bipolar femoral head replacement. A fluoroscopic study of movement over a four-year period. J Bone Joint Surg Br 1987;69(B):761–4. 22. Eiskjaer S, Boll K, Gelineck J. Component motion in bipolar cemented hemiarthroplasty. J Orthop Trauma 1989;3: 313–6. 23. Ito H, Matsuno T, Kaneda K. Bipolar hemiarthroplasty for osteonecrosis of the femoral head. A 7- to 18-year followup. Clin Orthop 2000;374:201–11.
J Formos Med Assoc | 2008 • Vol 107 • No 1
Disassembly and Dislocation of a Bipolar Hip Prosthesis Hsieh-Hsing Lee,1,2 Yung-Chih Lo,2 Leou-Chyr Lin,2* Shing-Sheng Wu1,2 Dislocation of a hip prosthesis is a common complication. In usual cases of hip prosthesis dislocation, the prosthetic femoral head comes out from either the natural acetabular cavity in a bipolar hemiarthroplasty or the prosthetic acetabulum in a total hip arthroplasty. Only a few cases of bipolar hip prosthesis dislocation due to dissociation between the polyethylene and inner head of the prosthesis have been reported. We describe a rare case of disassembly of the inner head from the bipolar outer prosthesis in an osteoarthritic acetabulum. A 72-year-old woman had undergone bipolar hemiarthroplasty due to fracture of the left femoral neck about 10 years previously. Recently, she sustained an injury after falling from a chair, and examinations revealed an unusual disassembly–dislocation of the bipolar hip prosthesis. We classified this failure in our patient as a type II failure, representing extreme varus position of the outer head in the acetabulum, dislocation of the inner head from the outer head, and a detached locking ring around the stem neck. This mechanism of failure as shown in our patient rarely occurs in the bipolar prosthesis of the self-centering system. Osteoarthritic change of the acetabulum would place the outer head in the varus position, increasing wear on the beveled rim by impinging the femoral stem neck and causing dislodgment of the inner locking ring and consequent disassembly–dislocation of the inner head. [J Formos Med Assoc 2008;107(1):84–88] Key Words: bipolar prosthesis, disassembly, dislocation, hemiarthroplasty
hip.7–9 Simple dislocation after primary bipolar hemiarthroplasty can usually be reduced by closed methods, but disassembly of the bipolar components usually requires another operation and possible revision of the prosthesis. We present a rare case of disassembly of the inner head from the polyethylene in a bipolar hip prosthesis and discuss the mechanism of prosthesis failure.
Dislocation of a hip prosthesis is a common complication, which has been fully discussed in several series.1–3 In cases of hip prosthesis dislocation, the prosthetic femoral head usually escapes from the prosthetic acetabulum in a total hip arthroplasty or from the natural acetabular cavity in a bipolar hemiarthroplasty. Only a few cases of bipolar hip prosthesis dislocation between the polyethylene and the inner head of the prosthesis have been reported.4 Little information is available about the rare but serious complication that involves the disassembly of modular components during dislocation5,6 or after closed reduction in the bipolar hemiarthroplasty of the dislocated
Case Report A 72-year-old woman with a femoral neck fracture of the left hip underwent bipolar hemiarthroplasty
©2008 Elsevier & Formosan Medical Association .
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1
Division of Traumatology, Department of Surgery, Municipal Wan-Fang Hospital, Taipei Medical University, and 2 Department of Orthopedics, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan. Received: March 15, 2007 Revised: April 13, 2007 Accepted: June 5, 2007
84
*Correspondence to: Dr Leou-Chyr Lin, Department of Orthopedics, Tri-Service General Hospital, National Defense Medical Center, No. 325, Section 2, Chenggong Road, Neihu District, Taipei 114, Taiwan. E-mail: [email protected]
J Formos Med Assoc | 2008 • Vol 107 • No 1
Disassembly and dislocation of bipolar hip prosthesis
Figure 1. Disassembly–dislocation of the inner head with a detached locking ring around the stem neck (arrow), extreme varus position of the outer head, and osteoarthritic changes of the acetabulum.
about 10 years previously. The femoral stem was collarless in the calcar region and coated with hydroxyapatite in the proximal one third of the stem. The press-fit femoral stem attained stability in the femoral canal from the initial impaction of the implant into the femur, and the size of the outer head was compatible with the patient’s acetabular size. The prosthetic left hip functioned well with little uncomfortable sensation until the patient fell from a chair in December 2005, when she felt a sharp pain, after which she had limited motion in her left hip. On arrival to the emergency department that same day, physical examination revealed no significant abnormality except painful disability over her left hip. X-ray revealed disassembly– dislocation of the inner femoral head from the bipolar hip prosthesis and the outer head located in the varus position (Figure 1). A wire embedded in the polyethylene rim appeared near the implant neck on the X-ray film. Cystic formation with sclerosing change was found in the acetabulum, which indicated osteoarthritic change. No lucent line was evident between the implant stem and the cortical bone over the lower two thirds despite periprosthetic bone resorption in the intertrochanteric region. Revision surgery for total hip arthroplasty was performed several days later using the posterolateral approach along the previous scar over the J Formos Med Assoc | 2008 • Vol 107 • No 1
Figure 2. Retrieved bipolar components with a severely damaged beveled rim over the outer head (left) and a dislodged locking ring (right).
R Figure 3. Postoperative radiograph demonstrates total hip arthroplasty without revision of the stem.
left hip. The inner head had dissociated from the outer head, and marked wear in the beveled rim of the polyethylene with destruction of the inner locking ring was evident (Figure 2). The cartilage of the left acetabulum was worn, and the subchondral bone was devastated with significant cystic formation. Although there was significant osteolysis with bone resorption around the intertrochanteric region (zones I and VII), the femoral stem was still well fixed. Bone grafting with an allograft was applied to the bony defect in the acetabulum and the intertrochanteric region, and total hip arthroplasty without revision of the stem prosthesis was performed (Figure 3). Pathology study revealed foreign body granuloma in the bone and soft tissue, infiltration 85
H.H. Lee, et al
of numerous macrophages, and formation of multinucleated giant cells with polyethylene particles, which may have been responsible for the osteolysis in the intertrochanteric region.
Discussion Prosthetic replacement has been used to treat displaced femoral neck fractures in older patients, and several series have demonstrated predictable pain relief, functional improvement, and a low revision rate.10,11 The results of procedures using the bipolar prosthesis have generally been satisfactory, and early results have been as good as, or better than, unipolar designs.12 Short- to mediumterm follow-up studies comparing unipolar with bipolar bearings demonstrate no clear difference in morbidity, mortality, or functional outcome. Longer term follow-up suggests a lower revision rate with bipolar bearings.1,13,14 The main complication of hip arthroplasty performed on displaced femoral neck fractures is dislocation, which occurs in about 10% of cases on average.2,3 This procedure produces two motion interfaces, one at the outer head–acetabulum interface and the other at the inner head–bearing polyethylene interface. The most frequent complication with a dislocated bipolar hip prosthesis occurs between the acetabulum and the outer head. Disassembly of the bipolar cups is a rare pattern of bipolar prosthesis dislocation. In such rare instances, the mechanism of dislocation should be evaluated, and future revisions in the design of bipolar prostheses considered. The Bateman bipolar hemiarthroplasty has been used since 1985, and disassembly of the Bateman bipolar prosthesis has been reported previously.15–18 The mechanism of failure involves varus loading of the bearing insert and stress concentrated directly over the deep circumferential groove of the superolateral leaflets, rather than impingement of the neck of the femoral stem against the inferomedial leaflets.19 Disassembly of the bipolar prosthesis may also be seen when reducing the dislocated hip.7–9 Another 86
Figure 4. The disassembly–dislocation mechanism of the inner head reveals beveled rim wearing by the impingement of the femoral stem neck with fixed varus position of the outer head in an osteoarthritic acetabulum.
failure mechanism can occur on the bipolar cup of the self-centering system, as shown in our patient. The self-centering system involves the eccentric offset of the bearing centers, in which the outer cup center is located distal to the inner bearing center to prevent varus alignment of the outer head.20 Several studies have reported that the bipolar prosthesis might function as a unipolar prosthesis moving between the interface of the outer head and the acetabulum interface, and that the outer heads tend to be fixed in the extreme varus position when the hip is abducted in some osteoarthritic patients.21,22 The outer head motion might also be limited because of osteophyte formation and granular proliferation around the osteoarthritic acetabulum. Similarly, friction between the outer head and the acetabulum interface might increase because of the loss of acetabular cartilage. These factors would place the outer head in the varus position, increasing wear on the beveled rim of the bearing insert by impinging the femoral stem neck (Figure 4), and causing dislodgment of the inner locking ring and consequent disassembly–dislocation of the J Formos Med Assoc | 2008 • Vol 107 • No 1
Disassembly and dislocation of bipolar hip prosthesis
inner head.20 Several studies have reported the disassembly of bipolar cups with self-centering system. Hasegawa et al reported an 11% rate of disassembly for the Zimmer Bi-Articular Cup.20 Ito et al reported disassembly rates of 4% (1 of 23 hips) for the Osteonics Universal Hip Replacement (UHR®) system and 17% (1 of 6 hips) for the Zimmer Bi-Articular Cup.23 These disassembly problems of bipolar prostheses will persist despite the newest generation of designs of the self-centering systems. Three types of failure of the locking ring have been discussed.20 The detached locking ring around the stem neck without dislocation of the inner head is classified as a type I failure. Dislocation of the inner head with the detached locking ring is classified as a type II failure. Dislocation of the inner head without the detached locking ring is classified as a type III failure. We classified the failure in our patient as a type II failure because it involved an extreme varus position of the outer head in the acetabulum, dislocation of the inner head from the outer head, and a detached locking ring around the stem neck. In our patient, marked polyethylene wear with destruction of the inner locking ring caused osteolysis and erosion of the acetabular weight-bearing surface that eventually led to loosening and migration of the outer cup and hip dislocation of the inner head. This suggests that disassembly– dislocation of the inner head can easily occur during extreme hip adduction and flexion. To determine whether or not disassembly–dislocation of the bipolar prosthesis occurs via the same mechanism in the osteoarthritic acetabulum, thorough clinical examination must be performed. Patients with a well-functioning bipolar hemiarthroplasty should be carefully and regularly followed-up.
Acknowledgments This study was supported in part by the C.Y. Foundation for the Advancement of Education, Sciences and Medicine. J Formos Med Assoc | 2008 • Vol 107 • No 1
References 1. Ong BC, Maurer SG, Aharonoff GB, et al. Unipolar versus bipolar hemiarthroplasty: functional outcome after femoral neck fracture at a minimum of thirty-six months of follow-up. J Orthop Trauma 2002;16:317–22. 2. Sierra RJ, Schleck CD, Cabanela ME. Dislocation of bipolar hemiarthroplasty: rate, contributing factors, and outcome. Clin Orthop 2006;442:230–8. 3. Barnes CL, Berry DJ, Sledge CB. Dislocation after bipolar hemiarthroplasty of the hip. J Arthroplasty 1995;10: 667–9. 4. Corteel J, Putz P. Dislocation–dissociation of a bipolar hip prosthesis. Acta Orthop Belg 1996;62:173–6. 5. Niggemeyer O, Fink B, Ruther W. Dislocation of the polyethylene liner in hip arthroplasty: 6 patients with dislocation within 3 years. Acta Orthop Scand 2002;73: 403–6. 6. Holmes JC, Whalen NJ. Disassembly of the Osteonics bipolar ring when used with a Howmedica femoral head. A report of four cases. J Arthroplasty 1992;7:201–3. 7. Loubignac F, Boissier F. Cup dissociation after reduction of a dislocated hip hemiarthroplasty. Rev Chir Orthop Reparatrice Appar Mot 1997;84:469–72. 8. Georgiou G, Siapkara A, Dimitrakopoulou A, et al. Dissociation of bipolar hemiarthroplasty of the hip after dislocation. A report of five different cases and review of literature. Injury 2006;37:162–8. 9. Star MJ, Colwell CW Jr, Donaldson WF 3rd, et al. Dissociation of modular hip arthroplasty components after dislocation. A report of three cases at differing dissociation levels. Clin Orthop 1992;278:111–5. 10. Bhandari M, Devereaux PJ, Swiontkowski MF, et al. Internal fixation compared with arthroplasty for displaced fractures of the femoral neck. A meta-analysis. J Bone Joint Surg Am 2003;85(A):1673–81. 11. Rogmark C, Carlsson A, Johnell O, et al. Primary hemiarthroplasty in old patients with displaced femoral neck fracture: a 1-year follow-up of 103 patients aged 80 years or more. Acta Orthop Scand 2002;73:605–10. 12. Calder SJ, Anderson GH, Jagger C, et al. Unipolar or bipolar prosthesis for displaced intracapsular hip fracture in octogenarians: a randomised prospective study. J Bone Joint Surg Br 1996;78(B):391–4. 13. Haidukewych GJ, Israel TA, Berry DJ. Long-term survivorship of cemented bipolar hemiarthroplasty for fracture of the femoral neck. Clin Orthop 2002;403:118–26. 14. Cornell CN, Levine D, O’Doherty J, et al. Unipolar versus bipolar hemiarthroplasty for the treatment of femoral neck fractures in the elderly. Clin Orthop 1998;348: 67–71. 15. Herzenberg JE, Harrelson JM, Campbell DC 2nd, et al. Fractures of the polyethylene bearing insert in Bateman bipolar hip prostheses. Clin Orthop 1988;228:88–93.
87
H.H. Lee, et al
16. Barmada R, Mess D. Bateman hemiarthroplasty component disassembly. A report of three cases of highdensity polyethylene failure. Clin Orthop 1987;224: 147–9. 17. Bateman JE, Berenji AR, Bayne O, et al. Long-term results of bipolar arthroplasty in osteoarthritis of the hip. Clin Orthop 1990;251:54–66. 18. Cameron HU, Cha EJ, Jung YB. An examination of factors contributing to failure of bipolar prostheses. Clin Orthop 1989;240:206–9. 19. Krein SW, Chao EY. Biomechanics of bipolar hip endoprostheses. J Orthop Res 1984;2:356–68.
88
20. Hasegawa M, Sudo A, Uchida A. Disassembly of bipolar cup with self-centering system: a report of seven cases. Clin Orthop 2004;425:163–7. 21. Phillips TW. The Bateman bipolar femoral head replacement. A fluoroscopic study of movement over a four-year period. J Bone Joint Surg Br 1987;69(B):761–4. 22. Eiskjaer S, Boll K, Gelineck J. Component motion in bipolar cemented hemiarthroplasty. J Orthop Trauma 1989;3: 313–6. 23. Ito H, Matsuno T, Kaneda K. Bipolar hemiarthroplasty for osteonecrosis of the femoral head. A 7- to 18-year followup. Clin Orthop 2000;374:201–11.
J Formos Med Assoc | 2008 • Vol 107 • No 1