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Cementless Alumina-on-Alumina Total Hip Arthroplasty in Patients Younger Than 50 Years: A 5-year Minimum Follow-Up Study
The Journal of Arthroplasty Vol. 22 No. 2 2007
Cementless Alumina-on-Alumina Total Hip Arthroplasty in Patients Younger Than 50 Years A 5-year Minimum Follow-Up Study Yong-Chan Ha, MD,* Kyung-Hoi Koo, MD,y Soon-Taek Jeong, MD,* Jeong Joon Yoo, MD,y Young-Min Kim, MD,y and Hee Joong Kim, MDy
Abstract: Sixty-seven patients (78 hips) who were younger than 50 years underwent cementless total hip arthroplasty using a porous-coated acetabular cup, an alumina liner, a 28-mm alumina head, and a proximally porous-coated femoral stem. One patient (1 hip) died and 2 patients (3 hips) were lost to follow-up. The remaining 64 patients (74 hips) were followed for 5 to 6 years. Their mean age at the index operation was 37 years. The mean Harris hip score was 94 points at the time of final follow-up. Four patients (4 hips) had mild thigh pain. All acetabular and femoral components were bone-ingrown, and neither pelvic nor femoral osteolysis was identified. No fracture of the ceramic liner or head was identified. Wear of the ceramic components was undetectable in 27 hips in which measurement was possible. Key words: total hip arthroplasty, cementless, ceramic. n 2007 Elsevier Inc. All rights reserved.
metal-on-metal articulation [7], and ceramicon-ceramic articulation [8 -10]. Ceramic-on-ceramic articulation has the lowest wear rate among various articulations [11]. Ceramic particles induced less macrophage reaction and decreased cytokine secretion compared with particles of high-density polyethylene [12], and total hip arthroplasty using the ceramic-on-ceramic articulation showed little periprosthetic osteolysis [8 -10]. Early ceramic prostheses combined an alumina head and a conically threaded bmonoblocQ or spherical press-fit cup. However, insufficient fixation of the acetabular component appeared to be a problem of the early ceramic prostheses. A modular acetabular system with a taper fixation between the metal shell and the ceramic liner has been introduced to obtain sound acetabular component fixation. In addition, hot isostatic pressing has been introduced to improve the material property of ceramic implants [13]. The purpose of our study was to assess the medium-term follow-up results (at a minimum of
Hip arthroplasty using a metal-on-polyethylene articulation in young and active patients is associated with high rates of failure [1-5]. Polyethylene particle–induced osteolysis is the major reason for failure; therefore, minimization of wear is the essential factor for the improvement of results of total hip arthroplasty. More durable articulations have been introduced, including highly crosslinked polyethylene-on-metal articulation [6],
From the *Department of Orthopaedic Surgery, Gyeongsang National University College of Medicine, Chinju, South Korea; and y Department of Orthopaedic Surgery, Seoul National University College of Medicine, Seoul, South Korea. Submitted June 20, 2005; accepted February 28, 2006. No benefits or funds were received in support of the study. Reprint requests: Kyung-Hoi Koo, MD, Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam, Gyeonggi-do 463-707, South Korea. n 2007 Elsevier Inc. All rights reserved. 0883-5403/07/1906-0004$32.00/0 doi:10.1016/j.arth.2006.02.169
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Alumina-On-Alumina Total Hip Arthroplasty ! Ha et al 185
5 years) of cementless alumina-on-alumina total hip arthroplasty in patients younger than 50 years.
Materials and Methods Between February 1998 and June 1999, 80 primary total hip arthroplasties were performed at the author’s hospital, on 69 patients who were younger than 50 years. In 78 hips (67 patients), a single cementless prosthesis design with alumina-on-alumina articulation (AESCULAP AG & Co, Tuttlingen, Germany) was used. In the remaining 2 patients (2 hips) with small femoral dimensions, that prosthesis could not be used. These 2 patients underwent total hip arthroplasty with other prosthesis and were excluded from the study. Two patients (3 hips) were not followed for a minimum of 5 years. One patient (1 hip) died 2 years after the operation. Thus, the remaining 64 patients (74 hips) were followed for an average of 5.5 years (range, 5-6 years). There were 45 men and 19 women. The mean age of the patients at the index operation was 37 years (range, 19-49 years), the mean weight was 64 kg (range, 49-82 kg), and the mean height was 166 cm (range, 154-181 cm). The primary diagnosis was osteonecrosis in 59 hips, osteoarthritis in 9, sequelae of pyogenic infection in 3, ankylosing spondylitis in 2, and rheumatoid arthritis in 1. The acetabular components were a hemispherical titanium cup (PLASMACUP SC, AESCULAP AG & Co) with an outer pure titanium plasma sprayed coating (PLASMAPORE, AESCULAP AG & Co) and an alumina acetabular insert (BIOLOX forte, CeramTec AG, Plochingen, Germany). The femoral component was a slightly tapered, rectangular, collarless titanium stem (BiCONTACT, AESCULAP AG & Co). The stem was tapered only in the anteroposterior projection at the angle of 1.58. The proximal one third of the stem was coated with PLASMAPORE. The neck-shaft angle of the stem was 1358. The standard offset was 40 mm, and the offset of the narrow stem ranged from 31.5 to 35 mm. A stem with the standard offset was used in 73 hips and a narrow stem with the offset of 32 mm was used in 1 hip. A 28-mm alumina femoral head (BIOLOX forte, CeramTec AG) was used. A short neck head component was used in 5 hips, a medium neck in 7, and a long neck in 62. The study was approved by the Institutional Review Board of the hospital, and all patients provided informed consent.
All operations were performed by 1 surgeon using a posterolateral approach. All of the acetabular and femoral components were inserted in a press-fit manner. Adjunctive acetabular screws were used in 6 hips (8%). Posterior capsule and short external rotators were routinely repaired. Although the prevailing opinion is that patients with proximal venous thrombosis should be treated with anticoagulants, a previous study in Korean patients has shown that all thrombi, regardless of their site and size, resolve spontaneously without associated pulmonary embolism [14]. Thus, our patients did not receive any form of prophylactic treatment of deep venous thrombosis. Postoperative coagulation assays, venograms, and lung perfusion scans were not performed. Patients were instructed to walk with partial weight-bearing with the aid of 2 crutches for 4 weeks after surgery. Routine follow-up visits were scheduled for 6 weeks; 3, 6, 9, and 12 months, and yearly thereafter. Patients who had not returned for regularly scheduled visits were contacted by telephone. Two nurses and 1 private locator found and visited nonresponders. Clinical evaluation was performed using the Harris hip scoring system [15]. Patients were routinely asked at follow-up evaluations whether they had experienced popping sensation because we were concerned about the separation of ceramicon-ceramic bearings and ceramic fractures. The radiographic evaluation was done by 2 independent observers who did not participate in the index operations. The 6-week anteroposterior and crosstable lateral radiographs were considered to be the baseline studies for all comparisons. Radiographic evaluation included an assessment of the fixation of the femoral and acetabular components, ceramic component’s wear, osteolysis, and heterotopic ossification. Vertical migration of the acetabular component was measured along a perpendicular line from the hip center to the interteardrop line. Horizontal migration was assessed by measuring the distance from the teardrop to the intersection of the perpendicular line from the hip center and the interteardrop line. Acetabular components were considered loose if there was a change in alignment of greater than 48 or 4 mm or more of change in the position [16]. Femoral components were considered to be unstable when there was progressive subsidence exceeding 3 mm, any change in position, a continuous radiolucent line wider than 2 mm, widening of the femoral canal, or a large pedestal [17]. The wear of articulation was calculated according to the method developed by Livermore
186 The Journal of Arthroplasty Vol. 22 No. 2 February 2007 et al [18]. Osteolytic lesions were defined according the criteria of Engh et al [19]. The lesions were recorded according to the 3 zones described by DeLee and Charnley [20] on the acetabular side and the 7 zones described by Gruen et al [21] on the femoral side. Heterotopic ossification was classified according to the system of Brooker et al [22].
Results The mean preoperative Harris hip score of 51 points (range, 21-84 points) improved to 94 points (range, 82-100 points) at the time of final followup. Of the 74 hips, 67 had an excellent result, 5 had a good result, and 2 had a fair result. The prevalence of pain in the thigh was 14% (11 hips). In 7 hips, the pain disappeared at 1 to 2 years after the operation. Four patients (4 hips, 5%) had persistent mild thigh pain at the time of final follow-up. No patient used any kind of walking support. Two patients, who were operated on because of sequelae of pyogenic infection, had a mild limp caused by residual discrepancy of leg length. Five patients (5 hips, 6.8%) experienced an intermittent popping sensation after the operation, which was presumed to be due to the separation of hip bearings. The popping occurred at the initial swing phase of walking or during rising from a sitting or squatting position. In radiographs of these 5 patients, there was no evidence of separation or ceramic fracture. In 3 patients, the
popping disappeared at 3 to 6 months after the operation. Two patients had a persistent popping sensation at the time of final follow-up. However, the frequency of popping was decreased. Fluoroscopic examination in these 2 patients showed no evidence of subluxation during active and passive motion of the hip joint. However, when the operated leg was pulled, the head component was separated from the acetabular component by several millimeters. All of the acetabular cups had radiographic evidence of bone ingrown stability at the time of the last follow-up. No femoral stem demonstrated radiographic evidence of subsidence, and all stems had bone ingrown stability. There was no ceramic fracture. Thus, no acetabular or femoral component was revised. All femora had cortical thinning, which was presumed to be due to cancellation of the cortex was limited to the calcar femorale (zone 7). The thinning was evident at 3 months postoperatively and was not seen to have progressed on serial radiographs. Seven femora (10%) had cortical hypertrophy in zone 5. The hypertrophy was evident 3 to 6 months after the operation and was not progressive. Periprosthetic osteolysis was not detected around any cup. Reactive radiolucent line formation was found around the uncoated distal tip of the stem in 8 hips at 9 to 18 months after the operation. The line was seen in only lateral radiograph (zones 10, 11, and 12) in 7 hips and in both anteroposterior and lateral radiographs (zones 3, 4, 5, 10, 11, and 12) in 1 hip.
Fig. 1. A 41-year-old man underwent cementless total hip arthroplasty using an alumina-on-alumina bearing surface. A, A preoperative anteroposterior radiograph shows femoral head osteonecrosis of the left hip. B and C, Anteroposterior and cross-table lateral radiographs obtained 6 weeks postoperative. No remodeling changes are present. D and E, Anteroposterior and cross-table lateral radiographs obtained 6 years postoperative. Reactive radiolucent line formation is seen around the uncoated distal tip of the stem in zones 3, 4, 5, 10, 11, and 12. The implants are stable, and there is no evidence of osteolysis or loosening.
Alumina-On-Alumina Total Hip Arthroplasty ! Ha et al 187
The line was parallel to the distal tip and the thickness was less than 2 mm. It was not associated with the formation of a pedestal and was not progressive. Thus, it was not thought to be an osteolysis (Fig. 1). Wear could not be measured with the technique described by Livermore et al [18] in 47 hips because it was difficult to differentiate the femoral head component from the ceramic liner on the radiographs. No evidence of wear was observed in 27 hips in which measurement was possible. Heterotopic ossification had developed in 7 hips (10%) by the time of the last follow-up. Five hips had grade I ossification, and 2 had grade II ossification. No patient had deep infection and there were no clinically apparent deep venous thromboses or pulmonary emboli. A femoral crack occurred in 1 hip during the insertion of the stem, which was fixed by cerclage wire. The fractures healed completely, and osseointegration of the prosthesis was achieved. Two hips dislocated and were treated successfully with closed reduction and abduction bracing for 3 months; after which, there was no recurrence.
Discussion To the authors’ knowledge, this is the first report on the intermediate-term results of the use of a contemporary alumina-on-alumina articulation in cementless total hip arthroplasty in patients younger than 50 years, and the results are encouraging. The rate of polyethylene wear and the prevalence of osteolysis associated with cementless or hybrid total hip arthroplasty in younger patients have been unacceptably high at the time of intermediate-term follow-up [1-5]. There has been renewed interest in total hip arthroplasty with the use of a ceramic-on-ceramic articulation because that prosthesis has been known to have a lower rate of wear [8 -10]. However, the risk of ceramic fracture was a wellrecognized problem. Old aluminas had a low density and a very coarse microstructure. Since 1990, the mechanical strength of alumina has been substantially improved. The latest-generation ceramic is an alumina that is hot isostatic– pressed, laser-marked, and proof-tested. Compared with the first generation ceramics, the grain size decreased from 4.2 to 1.8 lm, and the burst strength improved from 46 to 65 kN. Therefore, this new alumina-on-alumina bearing was expected to be a durable option for total hip arthroplasty in young and active patients [23,24].
Nevertheless, ceramic fractures of contemporary alumina-on-alumina articulation were reported [25-27]. In a recent study of cementless total hip arthroplasty using the new alumina-on-alumina bearing, the rate of ceramic fracture was 1% (1/100) [10]. Although there was no case of ceramic fracture in the current study, 5 patients (5 hips, 6.8%) experienced a popping sensation after the operation, which might be caused by separation of the weight-bearing surface. In the current study, careful attention was paid to avoid leg length discrepancy, and some joint laxity was allowed during the operation. This laxity might result in intermittent separation of the bearing surfaces, which might cause ceramic fractures in the future. We think enough soft tissue tension should be obtained during the operation in total hip arthroplasty using ceramic-on-ceramic articulation. If the leg length is adequate but the soft-tissue tension is insufficient after reduction of the trial prosthesis, some stem designs allow increasing the offset without increasing limb length [28]. However, the offset of the femoral stem, that was used in our study was 40 mm, and a higher offset prosthesis was not available. The presence of thigh pain after cementless total hip arthroplasty ranges from 2% to 40% [29]. Several factors have been associated with this problem, including the geometry and size of the stem. The incidence of thigh pain after total hip arthroplasties with a nontapered stem design was higher than that with a tapered stem design. The BiCONTACT stem, which was used in our study, was slightly tapered only in the anteroposterior projection at the angle of 1.58. The high prevalence (14%) of thigh pain in our patients seems to be associated with the prosthetic design and a lack of taper angle. The rate of failure of primary total hip arthroplasty in younger patients with osteonecrosis of the femoral head has been known to be higher than that in patients with osteoarthritis [30,31]. Polyethylene wear and osteolysis have limited the success of this procedure for the treatment of osteonecrosis. In our study using ceramic-onceramic bearing, 59 hips (80%) were operated on because of femoral head osteonecrosis. Although the numbers are too small for us to make any definitive conclusions, clinical and radiographic results after a minimum duration of follow-up of 5 years are satisfactory in patients with osteonecrosis and also patients with other diagnoses. Our intermediate-term results of cementless total hip arthroplasty with the use of contemporary alumina-on-alumina articulation in patients who
188 The Journal of Arthroplasty Vol. 22 No. 2 February 2007 were younger than 50 years are encouraging. However, longer follow-up is necessary to identify possible deleterious effects, especially ceramic fracture.
16.
References 17. 1. Dunkley AB, Eldridge JD, Lee MB, et al. Cementless acetabular replacement in the young. A 5- to 10-year prospective study. Clin Orthop Relat Res 2000; 376:149. 2. Beaule PE, Dorey FJ. Survivorship analysis of cementless total hip arthroplasty in younger patients. J Bone Joint Surg Am 2001;83:1590. 3. Berger RA, Jacobs JJ, Quigley LR, et al. Primary cementless acetabular reconstruction in patients younger than 50 years old. 7- to 11-year results. Clin Orthop Relat Res 1997;344:216. 4. Dowdy PA, Rorabeck CH, Bourne RB. Uncemented total hip arthroplasty in patients 50 years of age or younger. J Arthroplasty 1997;12:853. 5. Fye MA, Huo MH, Zatorski LE, et al. Total hip arthroplasty performed without cement in patients with femoral head osteonecrosis who are less than 50 years old. J Arthroplasty 1998;13:876. 6. D’Antonio JA, Manley MT, Capello WN, et al. Fiveyear experience with Crossfire highly cross-linked polyethylene. Clin Orthop Relat Res 2005;441:143. 7. Schmalzried TP, Peters PC, Maurer BT, et al. Longduration metal-on-metal total hip arthroplasties with low wear of the articulating surfaces. J Arthroplasty 1996;11:322. 8. Sedel L. Evolution of alumina-on-alumina implants: a review. Clin Orthop Relat Res 2000;379:48. 9. Hamadouche M, Boutin P, Daussange J, et al. Alumina-on-alumina total hip arthroplasty: a minimum 18.5-years follow-up study. J Bone Joint Surg Am 2002;84:69. 10. Yoo JJ, Kim YM, Yoon KS, et al. Alumina-onalumina total hip arthroplasty. A five-year minimum follow-up study. J Bone Joint Surg Am 2005;87:530. 11. Dorlot JM. Long-term effects of alumina components in total hip prostheses. Clin Orthop Relat Res 1992;282:47. 12. Catelas I, Petit A, Marchand R, et al. Cytotoxicity and macrophage cytokine release induced by ceramic and polyethylene particles in vitro. J Bone Joint Surg Br 1999;81:516. 13. Skinner HB. Ceramic bearing surfaces. Clin Orthop Relat Res 1999;369:83. 14. Kim YH, Oh SH, Kim JS. Incidence and natural history of deep-vein thrombosis after total hip arthroplasty. A prospective and randomised clinical study. J Bone Joint Surg Br 2003;85:661. 15. Harris WH. Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by
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mold arthroplasty. An end-result study using a new method of result evaluation. J Bone Joint Surg Am 1969;51:737. Latimer HA, Lachiewicz PF. Porous coated acetabular components with screw fixation. Five to ten-year results. J Bone Joint Surg Am 1996;78:975. Engh CA, Massin P, Suthers KE. Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components. Clin Orthop Relat Res 1990; 257:107 [Erratum in: Clin Orthop Relat Res 1992; 284:310]. Livermore J, Ilstrup D, Morrey B. Effect of femoral head size on wear of the polyethylene acetabular component. J Bone Joint Surg Am 1990;72:518. Engh CA, Hooten Jr JP, Zettl-Schaffer KF, et al. Porous-coated total hip replacement. Clin Orthop Relat Res 1994;298:89. DeLee JG, Charnley J. Radiological demarcation of cemented sockets in total hip replacement. Clin Orthop Relat Res 1976;121:20. Gruen TA, McNeice GM, Amstutz HC. bModes of failureQ of cemented stem-type femoral components: a radiographic analysis of loosening. Clin Orthop Relat Res 1979;141:17. 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 1973;55:1629. Willmann G. Ceramic femoral head retrieval data. Clin Orthop Relat Res 2000;379:22. Bierbaum BE, Nairus J, Kuesis D, et al. Ceramic-onceramic bearings in total hip arthroplasty. Clin Orthop Relat Res 2002;405:158. Bizot P, Larrouy M, Witvoet J, et al. Press-fit metalbacked alumina sockets: a minimum 5-year followup study. Clin Orthop Relat Res 2000;379:134. D’Antonio J, Capello W, Manley M, et al. New experience with alumina-on-alumina ceramic bearing for total hip arthroplasty. J Arthroplasty 2002; 17:390. Garino JP. Modern ceramic-on-ceramic total hip systems in the United States; early results. Clin Orthop Relat Res 2000;379:41. Della Valle AG, Padgett DE, Salvati EA. Preoperative planning for primary total hip arthroplasty. J Am Acad Orthop Surg 2005;13:455. Brown TE, Larson B, Shen F, et al. Thigh pain after cementless total hip arthroplasty: evaluation and management. J Am Acad Orthop Surg 2002;10:385. Kim YH, Oh JH, Oh SH. Cementless total hip arthroplasty in patients with osteonecrosis of the femoral head. Clin Orthop Relat Res 1995;320:73. Stulberg BN, Singer R, Goldner J, et al. Uncemented total hip arthroplasty in osteonecrosis. A 2- to 10-year evaluation. Clin Orthop Relat Res 1997; 334:116.
Cementless Alumina-on-Alumina Total Hip Arthroplasty in Patients Younger Than 50 Years A 5-year Minimum Follow-Up Study Yong-Chan Ha, MD,* Kyung-Hoi Koo, MD,y Soon-Taek Jeong, MD,* Jeong Joon Yoo, MD,y Young-Min Kim, MD,y and Hee Joong Kim, MDy
Abstract: Sixty-seven patients (78 hips) who were younger than 50 years underwent cementless total hip arthroplasty using a porous-coated acetabular cup, an alumina liner, a 28-mm alumina head, and a proximally porous-coated femoral stem. One patient (1 hip) died and 2 patients (3 hips) were lost to follow-up. The remaining 64 patients (74 hips) were followed for 5 to 6 years. Their mean age at the index operation was 37 years. The mean Harris hip score was 94 points at the time of final follow-up. Four patients (4 hips) had mild thigh pain. All acetabular and femoral components were bone-ingrown, and neither pelvic nor femoral osteolysis was identified. No fracture of the ceramic liner or head was identified. Wear of the ceramic components was undetectable in 27 hips in which measurement was possible. Key words: total hip arthroplasty, cementless, ceramic. n 2007 Elsevier Inc. All rights reserved.
metal-on-metal articulation [7], and ceramicon-ceramic articulation [8 -10]. Ceramic-on-ceramic articulation has the lowest wear rate among various articulations [11]. Ceramic particles induced less macrophage reaction and decreased cytokine secretion compared with particles of high-density polyethylene [12], and total hip arthroplasty using the ceramic-on-ceramic articulation showed little periprosthetic osteolysis [8 -10]. Early ceramic prostheses combined an alumina head and a conically threaded bmonoblocQ or spherical press-fit cup. However, insufficient fixation of the acetabular component appeared to be a problem of the early ceramic prostheses. A modular acetabular system with a taper fixation between the metal shell and the ceramic liner has been introduced to obtain sound acetabular component fixation. In addition, hot isostatic pressing has been introduced to improve the material property of ceramic implants [13]. The purpose of our study was to assess the medium-term follow-up results (at a minimum of
Hip arthroplasty using a metal-on-polyethylene articulation in young and active patients is associated with high rates of failure [1-5]. Polyethylene particle–induced osteolysis is the major reason for failure; therefore, minimization of wear is the essential factor for the improvement of results of total hip arthroplasty. More durable articulations have been introduced, including highly crosslinked polyethylene-on-metal articulation [6],
From the *Department of Orthopaedic Surgery, Gyeongsang National University College of Medicine, Chinju, South Korea; and y Department of Orthopaedic Surgery, Seoul National University College of Medicine, Seoul, South Korea. Submitted June 20, 2005; accepted February 28, 2006. No benefits or funds were received in support of the study. Reprint requests: Kyung-Hoi Koo, MD, Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam, Gyeonggi-do 463-707, South Korea. n 2007 Elsevier Inc. All rights reserved. 0883-5403/07/1906-0004$32.00/0 doi:10.1016/j.arth.2006.02.169
184
Alumina-On-Alumina Total Hip Arthroplasty ! Ha et al 185
5 years) of cementless alumina-on-alumina total hip arthroplasty in patients younger than 50 years.
Materials and Methods Between February 1998 and June 1999, 80 primary total hip arthroplasties were performed at the author’s hospital, on 69 patients who were younger than 50 years. In 78 hips (67 patients), a single cementless prosthesis design with alumina-on-alumina articulation (AESCULAP AG & Co, Tuttlingen, Germany) was used. In the remaining 2 patients (2 hips) with small femoral dimensions, that prosthesis could not be used. These 2 patients underwent total hip arthroplasty with other prosthesis and were excluded from the study. Two patients (3 hips) were not followed for a minimum of 5 years. One patient (1 hip) died 2 years after the operation. Thus, the remaining 64 patients (74 hips) were followed for an average of 5.5 years (range, 5-6 years). There were 45 men and 19 women. The mean age of the patients at the index operation was 37 years (range, 19-49 years), the mean weight was 64 kg (range, 49-82 kg), and the mean height was 166 cm (range, 154-181 cm). The primary diagnosis was osteonecrosis in 59 hips, osteoarthritis in 9, sequelae of pyogenic infection in 3, ankylosing spondylitis in 2, and rheumatoid arthritis in 1. The acetabular components were a hemispherical titanium cup (PLASMACUP SC, AESCULAP AG & Co) with an outer pure titanium plasma sprayed coating (PLASMAPORE, AESCULAP AG & Co) and an alumina acetabular insert (BIOLOX forte, CeramTec AG, Plochingen, Germany). The femoral component was a slightly tapered, rectangular, collarless titanium stem (BiCONTACT, AESCULAP AG & Co). The stem was tapered only in the anteroposterior projection at the angle of 1.58. The proximal one third of the stem was coated with PLASMAPORE. The neck-shaft angle of the stem was 1358. The standard offset was 40 mm, and the offset of the narrow stem ranged from 31.5 to 35 mm. A stem with the standard offset was used in 73 hips and a narrow stem with the offset of 32 mm was used in 1 hip. A 28-mm alumina femoral head (BIOLOX forte, CeramTec AG) was used. A short neck head component was used in 5 hips, a medium neck in 7, and a long neck in 62. The study was approved by the Institutional Review Board of the hospital, and all patients provided informed consent.
All operations were performed by 1 surgeon using a posterolateral approach. All of the acetabular and femoral components were inserted in a press-fit manner. Adjunctive acetabular screws were used in 6 hips (8%). Posterior capsule and short external rotators were routinely repaired. Although the prevailing opinion is that patients with proximal venous thrombosis should be treated with anticoagulants, a previous study in Korean patients has shown that all thrombi, regardless of their site and size, resolve spontaneously without associated pulmonary embolism [14]. Thus, our patients did not receive any form of prophylactic treatment of deep venous thrombosis. Postoperative coagulation assays, venograms, and lung perfusion scans were not performed. Patients were instructed to walk with partial weight-bearing with the aid of 2 crutches for 4 weeks after surgery. Routine follow-up visits were scheduled for 6 weeks; 3, 6, 9, and 12 months, and yearly thereafter. Patients who had not returned for regularly scheduled visits were contacted by telephone. Two nurses and 1 private locator found and visited nonresponders. Clinical evaluation was performed using the Harris hip scoring system [15]. Patients were routinely asked at follow-up evaluations whether they had experienced popping sensation because we were concerned about the separation of ceramicon-ceramic bearings and ceramic fractures. The radiographic evaluation was done by 2 independent observers who did not participate in the index operations. The 6-week anteroposterior and crosstable lateral radiographs were considered to be the baseline studies for all comparisons. Radiographic evaluation included an assessment of the fixation of the femoral and acetabular components, ceramic component’s wear, osteolysis, and heterotopic ossification. Vertical migration of the acetabular component was measured along a perpendicular line from the hip center to the interteardrop line. Horizontal migration was assessed by measuring the distance from the teardrop to the intersection of the perpendicular line from the hip center and the interteardrop line. Acetabular components were considered loose if there was a change in alignment of greater than 48 or 4 mm or more of change in the position [16]. Femoral components were considered to be unstable when there was progressive subsidence exceeding 3 mm, any change in position, a continuous radiolucent line wider than 2 mm, widening of the femoral canal, or a large pedestal [17]. The wear of articulation was calculated according to the method developed by Livermore
186 The Journal of Arthroplasty Vol. 22 No. 2 February 2007 et al [18]. Osteolytic lesions were defined according the criteria of Engh et al [19]. The lesions were recorded according to the 3 zones described by DeLee and Charnley [20] on the acetabular side and the 7 zones described by Gruen et al [21] on the femoral side. Heterotopic ossification was classified according to the system of Brooker et al [22].
Results The mean preoperative Harris hip score of 51 points (range, 21-84 points) improved to 94 points (range, 82-100 points) at the time of final followup. Of the 74 hips, 67 had an excellent result, 5 had a good result, and 2 had a fair result. The prevalence of pain in the thigh was 14% (11 hips). In 7 hips, the pain disappeared at 1 to 2 years after the operation. Four patients (4 hips, 5%) had persistent mild thigh pain at the time of final follow-up. No patient used any kind of walking support. Two patients, who were operated on because of sequelae of pyogenic infection, had a mild limp caused by residual discrepancy of leg length. Five patients (5 hips, 6.8%) experienced an intermittent popping sensation after the operation, which was presumed to be due to the separation of hip bearings. The popping occurred at the initial swing phase of walking or during rising from a sitting or squatting position. In radiographs of these 5 patients, there was no evidence of separation or ceramic fracture. In 3 patients, the
popping disappeared at 3 to 6 months after the operation. Two patients had a persistent popping sensation at the time of final follow-up. However, the frequency of popping was decreased. Fluoroscopic examination in these 2 patients showed no evidence of subluxation during active and passive motion of the hip joint. However, when the operated leg was pulled, the head component was separated from the acetabular component by several millimeters. All of the acetabular cups had radiographic evidence of bone ingrown stability at the time of the last follow-up. No femoral stem demonstrated radiographic evidence of subsidence, and all stems had bone ingrown stability. There was no ceramic fracture. Thus, no acetabular or femoral component was revised. All femora had cortical thinning, which was presumed to be due to cancellation of the cortex was limited to the calcar femorale (zone 7). The thinning was evident at 3 months postoperatively and was not seen to have progressed on serial radiographs. Seven femora (10%) had cortical hypertrophy in zone 5. The hypertrophy was evident 3 to 6 months after the operation and was not progressive. Periprosthetic osteolysis was not detected around any cup. Reactive radiolucent line formation was found around the uncoated distal tip of the stem in 8 hips at 9 to 18 months after the operation. The line was seen in only lateral radiograph (zones 10, 11, and 12) in 7 hips and in both anteroposterior and lateral radiographs (zones 3, 4, 5, 10, 11, and 12) in 1 hip.
Fig. 1. A 41-year-old man underwent cementless total hip arthroplasty using an alumina-on-alumina bearing surface. A, A preoperative anteroposterior radiograph shows femoral head osteonecrosis of the left hip. B and C, Anteroposterior and cross-table lateral radiographs obtained 6 weeks postoperative. No remodeling changes are present. D and E, Anteroposterior and cross-table lateral radiographs obtained 6 years postoperative. Reactive radiolucent line formation is seen around the uncoated distal tip of the stem in zones 3, 4, 5, 10, 11, and 12. The implants are stable, and there is no evidence of osteolysis or loosening.
Alumina-On-Alumina Total Hip Arthroplasty ! Ha et al 187
The line was parallel to the distal tip and the thickness was less than 2 mm. It was not associated with the formation of a pedestal and was not progressive. Thus, it was not thought to be an osteolysis (Fig. 1). Wear could not be measured with the technique described by Livermore et al [18] in 47 hips because it was difficult to differentiate the femoral head component from the ceramic liner on the radiographs. No evidence of wear was observed in 27 hips in which measurement was possible. Heterotopic ossification had developed in 7 hips (10%) by the time of the last follow-up. Five hips had grade I ossification, and 2 had grade II ossification. No patient had deep infection and there were no clinically apparent deep venous thromboses or pulmonary emboli. A femoral crack occurred in 1 hip during the insertion of the stem, which was fixed by cerclage wire. The fractures healed completely, and osseointegration of the prosthesis was achieved. Two hips dislocated and were treated successfully with closed reduction and abduction bracing for 3 months; after which, there was no recurrence.
Discussion To the authors’ knowledge, this is the first report on the intermediate-term results of the use of a contemporary alumina-on-alumina articulation in cementless total hip arthroplasty in patients younger than 50 years, and the results are encouraging. The rate of polyethylene wear and the prevalence of osteolysis associated with cementless or hybrid total hip arthroplasty in younger patients have been unacceptably high at the time of intermediate-term follow-up [1-5]. There has been renewed interest in total hip arthroplasty with the use of a ceramic-on-ceramic articulation because that prosthesis has been known to have a lower rate of wear [8 -10]. However, the risk of ceramic fracture was a wellrecognized problem. Old aluminas had a low density and a very coarse microstructure. Since 1990, the mechanical strength of alumina has been substantially improved. The latest-generation ceramic is an alumina that is hot isostatic– pressed, laser-marked, and proof-tested. Compared with the first generation ceramics, the grain size decreased from 4.2 to 1.8 lm, and the burst strength improved from 46 to 65 kN. Therefore, this new alumina-on-alumina bearing was expected to be a durable option for total hip arthroplasty in young and active patients [23,24].
Nevertheless, ceramic fractures of contemporary alumina-on-alumina articulation were reported [25-27]. In a recent study of cementless total hip arthroplasty using the new alumina-on-alumina bearing, the rate of ceramic fracture was 1% (1/100) [10]. Although there was no case of ceramic fracture in the current study, 5 patients (5 hips, 6.8%) experienced a popping sensation after the operation, which might be caused by separation of the weight-bearing surface. In the current study, careful attention was paid to avoid leg length discrepancy, and some joint laxity was allowed during the operation. This laxity might result in intermittent separation of the bearing surfaces, which might cause ceramic fractures in the future. We think enough soft tissue tension should be obtained during the operation in total hip arthroplasty using ceramic-on-ceramic articulation. If the leg length is adequate but the soft-tissue tension is insufficient after reduction of the trial prosthesis, some stem designs allow increasing the offset without increasing limb length [28]. However, the offset of the femoral stem, that was used in our study was 40 mm, and a higher offset prosthesis was not available. The presence of thigh pain after cementless total hip arthroplasty ranges from 2% to 40% [29]. Several factors have been associated with this problem, including the geometry and size of the stem. The incidence of thigh pain after total hip arthroplasties with a nontapered stem design was higher than that with a tapered stem design. The BiCONTACT stem, which was used in our study, was slightly tapered only in the anteroposterior projection at the angle of 1.58. The high prevalence (14%) of thigh pain in our patients seems to be associated with the prosthetic design and a lack of taper angle. The rate of failure of primary total hip arthroplasty in younger patients with osteonecrosis of the femoral head has been known to be higher than that in patients with osteoarthritis [30,31]. Polyethylene wear and osteolysis have limited the success of this procedure for the treatment of osteonecrosis. In our study using ceramic-onceramic bearing, 59 hips (80%) were operated on because of femoral head osteonecrosis. Although the numbers are too small for us to make any definitive conclusions, clinical and radiographic results after a minimum duration of follow-up of 5 years are satisfactory in patients with osteonecrosis and also patients with other diagnoses. Our intermediate-term results of cementless total hip arthroplasty with the use of contemporary alumina-on-alumina articulation in patients who
188 The Journal of Arthroplasty Vol. 22 No. 2 February 2007 were younger than 50 years are encouraging. However, longer follow-up is necessary to identify possible deleterious effects, especially ceramic fracture.
16.
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