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Alumina Delta-on-Alumina Delta Bearing in Cementless Total Hip Arthroplasty in Patients Aged <50 Years
The Journal of Arthroplasty xxx (2016) 1e6
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Original Article
Alumina Delta-on-Alumina Delta Bearing in Cementless Total Hip Arthroplasty in Patients Aged <50 Years Young-Hoo Kim, MD a, *, Jang-Won Park, MD b, Jun-Shik Kim, MD b a b
The Joint Replacement Center, SeoNam Hospital, Ewha Womans University School of Medicine, Seoul, Republic of Korea The Joint Replacement Center, MokDong Hospital, Ewha Womans University School of Medicine, Seoul, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history: Received 18 January 2016 Received in revised form 1 March 2016 Accepted 7 March 2016 Available online xxx
Background: There are limited studies to evaluate long-term clinical and radiographic outcomes of alumina delta ceramic-on-ceramic bearings in cementless total hip arthroplasty (THA). The purpose of this study was to evaluate the clinical and radiographic results, prevalence of osteolysis, squeaking, and fracture of ceramic material associated with the use of the alumina delta ceramic-on-alumina delta ceramic bearing in cementless THA in patients aged <50 years. Methods: We reviewed the cases of 277 patients (334 hips) who underwent a cementless THA using alumina delta ceramic-on-alumina delta ceramic when they were 50 years or younger at the time of surgery. Demographic data; Harris Hip Score; Western Ontario McMaster Universities Osteoarthritis Index; and University of California, Los Angeles activity score were recorded. Radiographic and computerized tomographic evaluations were used to evaluate implant fixation and osteolysis. Squeaking sound and ceramic fracture were documented. The mean follow-up was 13.1 years (range, 10-14). Results: The mean postoperative Harris Hip Score, Western Ontario and McMaster Universities Osteoarthritis Index score, University of California, Los Angeles activity score were 93 points, 15 points, and 8.6 points, respectively. Two patients had thigh pain (grade 7 points). All acetabular components and all but 2 femoral components were well fixed. Thirty-three hips (10%) exhibited clicking sound, and 2 hips (0.6%) exhibited squeaking sound. No hip had osteolysis or ceramic head or liner fracture. Conclusion: Our minimum 10-year follow-up results with the use of alumina delta ceramic-on-alumina delta ceramic bearings in patients aged <50 years suggest that cementless THA provides a high rate of survivorship without evidence of osteolysis or fracture of ceramic material. © 2016 Published by Elsevier Inc.
Keywords: cementless total hip arthroplasty alumina delta-on-alumina delta clinical results radiographic results squeaking sound ceramic fracture
Although total hip arthroplasties (THAs) have provided durable long-term results, periprosthetic osteolysis related to particulate polyethylene wear debris is considered an important cause of aseptic loosening and late implant failure [1,2]. Concern regarding development of osteolysis attributable to polyethylene wear, particularly in young patients, prompted the introduction of ceramic-on-ceramic bearings to prevent or minimize wear-related osteolysis. Furthermore, to combat the problem of hip instability in THA, larger diameter ceramic, metal, or highly cross-linked polyethylene femoral heads were transitioned [3-7].
No author associated with this paper has disclosed any potential or pertinent conflicts which may be perceived to have impending conflict with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2016.03.016. * Reprint requests: Young-Hoo Kim, MD, The Joint Replacement Center, SeoNam Hospital, Ewha Womans University School of Medicine, #20, Sinjeongipen 1-ro, Yangcheon-gu, Seoul 158-070, Republic of Korea. http://dx.doi.org/10.1016/j.arth.2016.03.016 0883-5403/© 2016 Published by Elsevier Inc.
Recent studies of the alumina forte ceramic-on-alumina forte ceramic bearings with smaller femoral heads (28 or 32 mm) found little or no osteolysis [8-13]. Concerns with alumina forte ceramic bearing remain, including ceramic head [14-16] and, more significantly, liner fracture [17-19]. Therefore, alumina delta ceramic-onalumina delta ceramic (BIOLOX Delta; CeramTec AG, Plochingen, Germany) was developed to address some of the concerns raised with the alumina forte ceramic-on-alumina forte ceramic bearing. The material has a smaller grain size (<0.8 mm) compared with the grain size of alumina forte ceramic (1-5 mm). The mechanical properties of this combination result in a bearing that has improved toughness and wear characteristics when measured in a laboratory setting [20]. There are few studies of alumina delta ceramic-on-alumina delta ceramic bearing, but these are limited by small number of patients aged <50 years and short-term follow-up [18,21]. To our knowledge, there are limited studies to evaluate long-term clinical and radiographic outcomes of alumina delta ceramic-on-alumina
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delta ceramic bearings in cementless THA in large cohorts of patients of age <50 years. The purpose of this study was to evaluate the clinical and radiographic outcomes associated with the use of the alumina delta ceramic-on-alumina delta ceramic bearing in cementless THA in patients aged <50 years. In addition, we determined the prevalence of osteolysis, squeaking, and fracture of ceramic femoral head or acetabular ceramic liner.
Assessed for eligibility (n=313 patients, 384 hips) Excluded (n=27 patients, 37 hips)
Enrollment
Allocation (n=286 patients, 347 hips)
Materials and Methods A consecutive 313 patients (384 hips) underwent THAs from October 2001 to October 2004. Of these, 286 patients (347 hips) met the inclusion criteria and were recruited to participate in the study. All operations were performed by the senior surgeon. The indications for surgery were hip diseases that were severe enough to warrant THA after an adequate trial of nonoperative therapy. Twenty-five patients (34 hips) were excluded because they were older than 50 years (the age limit was chosen arbitrarily), one patient (2 hips) was excluded because the patient had a foot or ankle disorder that limited walking, and one patient (one hip) was excluded because the patient had marked proximal femoral deformity. Contraindications for this ultrashort cementless stem were the patients with high dislocation of the femoral head, severe osteoporosis, or intertrochanteric fracture. The study protocol, including the consent form, was approved by the institutional review board at our institution. A detailed informed consent form was signed by each patient. Nine patients were lost to follow-up, leaving 277 patients (334 hips) available for study with a minimum duration of follow-up of 10 years (mean, 13.1 years; range, 10-14 years; Fig. 1). There were 143 men and 134 women with a mean age (standard deviation) of 48.2 (11.3) years (range, 21-49 years) at the time of surgery. The mean height (standard deviation) was 165.7 (10.2) cm (range, 157-186 cm), and the mean body weight (standard deviation) was 78 (9.7) kg (range, 68-121 kg). The mean body mass index (standard deviation) was 28.9 (10.1) kg/m2 (range, 27.2-34.6 kg/m2). The diagnosis was osteonecrosis of the femoral head in 124 patients (45%), osteoarthritis secondary to developmental dysplastic hip in 115 (42%), osteoarthrosis secondary to childhood pyogenic arthritis in 15 (5%), traumatic arthritis in 13 (5%), femoral neck fracture in 6 (2%), and rheumatoid arthritis in 4 (1%; Table 1). On the contrary to westerners, the predominant diagnosis was osteonecrosis related to excessive alcohol consumption and very low incidence of osteoarthritis of the hip joint in the current patient cohorts. All operations were performed by the senior author using a posterolateral approach. The ultrashort anatomic cementless stem (Proxima; DePuy, Leeds, United Kingdom) was used in all hips. The ultrashort anatomic cementless stem is made of titanium alloy and is entirely porous-coated with sintered titanium beads having a mean pore size of 250 mm, to which a 30-mm-thick hydroxyapatite coating is applied, except at the distal tip. The femoral neck was cut horizontally at the head-neck juncture. The broach was inserted into the divided femoral neck and driven distally in a varus direction by hammer blows and then steadily tilted in the correct alignment while advancing into the femoral metaphysis. We refer to this technique as the “round-the-corner” technique [22-25]. The size of the femoral component was selected not by a canal fill but by the torsional stability of the stem as dictated by bone quality. The real component was 0.5 mm larger than that of the prepared metaphysis. We used a 36-mm-diameter Biolox delta ceramic liner when a cup size was >52 mm, and a 32-mm Biolox delta ceramic liner was used when a cup size was <52 mm. A 36-mm-diameter Biolox delta ceramic femoral head (CeramTec) was used in 283 hips
Follow-up
Before 2 years (n=284 patients, 344 hips) Lost to follow-up (n=2 patients, 3 hips) Between 2-5 years (n=281 patients, 340 hips) Lost to follow-up (n=3 patients, 4 hips) Between 5-10 years (n=279 patients, 337 hips) Lost to follow-up (n=2 patients, 3 hips) Between 10-14 years (n=277 patients, 334 hips) Lost to follow-up (n=2 patients, 3 hips)
Analysis (n=277 patients, 334 hips) Fig. 1. CONSORT flow diagram.
(85%), and a 32-mm-diameter Biolox delta ceramic femoral head was used in the remaining 51 hips (15%). A cementless Pinnacle cup (DePuy, Warsaw, IN) and a 36-mm-internal-diameter Biolox delta ceramic liner were used in 283 hips (85%), and a 32-mm-internaldiameter Biolox delta ceramic liner was used in the remaining 51 hips (15%). In 304 hips (91%), the solid acetabular component was fixed with use of a press-fit technique only; in the remaining 30 hips (9%), 1 or 2 screws were inserted for fixation of the cups via the screw holes.
Table 1 Demographic Data of Patients. Number of Patients (Hips) Male:female Mean age (range, SD), y Mean weight (range, SD), kg Mean height (range, SD), cm Mean BMI (kg/m2) Diagnosis, n (%) Osteonecrosis Ethanol associated Idiopathic steroid use Osteoarthritis secondary to developmental dysplastic hip Osteoarthritis secondary to childhood pyogenic arthritis Traumatic arthritis Femoral neck fracture Rheumatoid arthritis Duration of follow-up (y) SD, standard deviation; BMI, body mass index.
277 (334) 143:134 48.2 (21-49, 11.3) 78 (68-121, 9.7) 165.7 (157-186, 10.2) 28.9 (27.2-34.6, 10.1) 124 69 44 115
(45) (56) (35) (42)
15 (5) 13 6 4 13.1
(5) (2) (1) (10-14)
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Patients were mobilized on the second postoperative day and progressed to full weight-bearing with a walking frame or crutches as comfort permitted; they were advised to use a walking aid for 6 weeks. The patients were reviewed at 3 months, 1 year, and every 2-3 years thereafter. The Harris Hip Score [26] was recorded at each visit, as was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score [27]. Thigh pain was scored on a 10-point visual analog scale [28] where 0 represents no pain and 10 represents severe pain, and activity level was assessed using the University of California, Los Angeles (UCLA) activity score at the most recent follow-up [29]. Also, the patient's satisfaction was assessed as fully satisfied, satisfied, dissatisfied, and fully dissatisfied. All the data were obtained by one observer who was not part of the surgical team. Any clicking or squeaking sound from the ceramic-on-ceramic bearing was recorded only by asking the patient. Radiological evaluation was undertaken at 3 months and 1 year postoperatively, and at each subsequent visit thereafter. A supine anteroposterior radiograph of the pelvis with both hips in 15 of internal rotation and no abduction and a cross-table lateral and iliac oblique radiograph of each hip were obtained 7 days postoperatively and at each subsequent visit. The femoral morphology was determined preoperatively using Dorr's system of classification [30]. Anteversion and inclination of the acetabular component were measured by the method of Engh et al [31]. Definite loosening of the femoral component was defined when there was progressive axial subsidence of >3 mm or a varus or a valgus shift of >3 [32]. Radiographs were analyzed by a research associate with no knowledge of the patient's name. The intraobserver error in all the radiographic measurements was determined by intraclass correlation coefficient after repeated measurements for 3 times at 3-day intervals. This was 0.96 (0.94-1.00), indicating excellent reproducibility. The fixation of the femoral component was classified as osseointegrated, fibrous stable, or unstable [30]. Stress shielding was graded on the radiographs at the final follow-up according to the classification of Engh and Bobyn [32]. The size and location of osteolytic lesions were assessed using the technique described by Zicat et al [33]. At the last follow-up, all patients underwent computerized tomographic (CT) scanning using a multislice scanner (General Electric Light Plus; GE Medical Systems, Milwaukee, WI) to determine osteolysis. The scan sequence was between the posterior superior iliac spine and 10 cm below the stem tip, using contiguous 2.5-mm slices. Osteolysis was defined as any nonlinear region of periprosthetic cancellous bone loss with delineable margins. One author examined all radiographs and CT scans. Survivorship analysis was performed with use of the KaplanMeier method [34], with revision for any reason as one end point and revision due to mechanical failure (clinical and radiographic evidence of aseptic loosening) at the time of follow-up as the other end point. We determined differences in continuous variances (Harris Hip Score and range of motion) between preoperative and postoperative results with use of a Student paired t test and differences in categorical variances (details of functional evaluation and deformity according to the Harris Hip Score) and limb length between preoperative and postoperative evaluation with use of a chi-square test. Univariate regression analysis was used to evaluate the relationship, if any, between osteolysis and the variables of age, sex, weight, diagnosis, duration of follow-up, and acetabular inclination and anteversion. All statistical analysis were performed using the Statistical Package Social Science software, version 14.0 (SPSS Inc, Chicago, IL), and statistical significance was set at a P value <.05.
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Results Preoperative Harris Hip Score, WOMAC score, and UCLA activity score improved significantly at the final follow-up (Table 2). The mean preoperative Harris Hip Score (standard deviation) was 39 (19.9) points (range, 10-51 points), and the mean postoperative Harris Hip Score (standard deviation) was 93 (11.7) points (range, 70-100 points). The mean preoperative total WOMAC score (standard deviation) was 64 (19) points (range, 51-85 points), and the mean postoperative total WOMAC score (standard deviation) was 15 (8) points (range, 5-25 points). The mean preoperative UCLA activity score was 2.4 points (range, 1-3 points), and the mean postoperative UCLA activity score was 8.6 points (range, 8-10 points). All but 2 patients (grade 7 points) had no thigh pain. Dependence on walking aids, ability to negotiate stairs, public transportation, to put on footwear, and to cut toe nails were improved markedly after the operation. Two hundred seventy-five patients (99.3%) were satisfied with the outcome of the operation. The 2 patients (0.7%) were dissatisfied because of pain resulted from aseptic loosening (Table 2). Fifty-eight of 277 patients (21%) changed from work involving heavy manual labor before the operation to sedentary work after the operation. The remaining 219 patients (79%) remained in the previous occupation after the operation. All patients were advised not to participate in highimpact sports or heavy labor work. Preoperatively, the Dorr isthmus ratio [30] ranged from 0.32 to 0.49. Two hundred forty-one hip (87%) were Dorr type A, 16 (6%) were type B, and 20 (7%) were type C. As seen on the postoperative radiograph, 269 femoral stems (97%) were neutral and 8 (93%) were in varus (<5 ). The mean inclination and anteversion of the acetabular component were 42 (range, 25 -52 ) and 21 (range, 17 -25 ), respectively. All hips had osseous integration of the acetabular components. All but 2 hips had osseous integration of the femoral components. Two hips (0.7%) exhibited an aseptic loosening of the femoral component (Table 3). When both an anteroposterior radiograph and an iliac oblique radiograph were examined, no hip displayed femoral or acetabular osteolysis. No femoral or acetabular osteolysis was identified in all hips by CT scans (Figs. 2 and 3). Thirty-three of 334 hips (10%) had clicking sound, and 2 hips (0.6%) exhibited squeaking sound. No hip had a fracture of the ceramic femoral head or acetabular ceramic liner. No hip had a revision for aseptic loosening. Kaplan-Meier survivorship analysis revealed a 99.7% survival rate (95% CI, 0.94-1.00) of the acetabular component and 99.3% survival rate (95% CI, 0.92-1.00) of the femoral component as the end point of revision or aseptic loosening at 13.1 years.
Table 2 Clinical Results. Parameter
Preoperative
Postoperative
Harris Hip Score (points)a 1y 5y 10 y 13.1 y Thigh pain at the final follow-up WOMAC score (points)a UCLA activity scorea Clicking sound Squeaking sound
39 ± 19.9 (10-51)
d
d d d d d
95 ± 3.9 94 ± 6.1 93 ± 6.8 93 ± 11.7 2 Hips
64 ± 19 (51-85) 2.4 (1-3) d d
15 ± 8 8.6 5 hips 0 hip
(73-100) (70-100) (70-100) (70-100) (0.6%; loosening stem) (5-25) (8-10) (1.5%) (0%)
WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index; UCLA, University of California, Los Angeles. a The values are given as the mean and the standard deviation, with the range in parentheses.
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Table 3 Radiographic Results. Parameter Dorr bone type, n (%) A B C Acetabular component positiona ( ) Inclination Anteversion Femoral component position, n (%) Neutral position Varus position Valgus position Center of rotationa Horizontal (mm) Vertical (mm) Femoral offseta (mm) Abductor moment arma (mm) Femoral neck lengtha (mm) Limb length discrepancyb (mm) Radiolucent line (>1 mm), n (%) Migration of the acetabular component, n (%) Migration of the femoral component, n (%)
Findings 241 (87) 16 (6) 20 (7) 42 (35-47) 21 (17-25) 269 (97) 8 (3) 0 (0) 45 18 44 49 37 0.3 ± 0.4 0 0 2 Hips
(39-53) (14-24) (38-83) (39-88) (30-41) ( 1.5 to 1.1) (0) (0) (0.6%)
a
The values are given as the mean, with the range in parentheses. The values are given as the mean and standard deviation with the range in parentheses. b
Complications Five of 334 hips (1.5%) had a dislocation postoperatively. Four of these were treated with closed reduction and an abduction brace for 3 months, and no further dislocation occurred. One of 5 hips had a recurrent dislocation and a cup was revised. Three hips (0.9%) had intraoperative undisplaced calcar fracture. These fractures were fixed with cerclage cables, and all were healed without compromise of stem stability. These patients were allowed to partial weight-bearing for 3 months. Discussion The alumina delta ceramic-on-alumina delta ceramic bearing was developed to address some of the concerns with the alumina forte ceramic-on-alumina forte ceramic design. The midterm or long-term studies on the current generation of cementless THAs with an alumina delta-on-alumina delta ceramic bearing in patients aged <50 years are limited. The long-term results of cementless ultrashort metaphyseal-fitting anatomic THA with an alumina delta ceramic-on alumina delta ceramic bearing in our patients aged <50 years demonstrated low incidence of thigh pain and very low incidence of aseptic loosening. Furthermore, there was no osteolysis on radiographs and CT scans. Several authors [8,11,12] reported on alumina forte-on-alumina forte ceramic bearings, and mean Harris Hip Scores were between 95 and 97 points in the short-and long-term follow-up. Hamilton et al [18] reported on midterm results of alumina delta ceramic-onalumina delta ceramic THA, and the mean Harris Hip Score was 94.1 points at mean 5.3 years follow-up. Harris Hip Score in our study, although longer follow-up, is similar to other report [18]. Thigh pain is sometimes associated with the use of cementless femoral components [22,23]. The low incidence of thigh pain in our patients may be attributable to the rigid axial and torsional stability of the femoral component in the proximal femur and an absence of contact between the distal stem and the femoral cortex. Many previous reports [10-12,22-25] suggested that fixation of a current generation of cementless THAs in young patients is quite encouraging. Our data revealed that there was a low incidence of
Fig. 2. (A) An anteroposterior view of both hips of a 36-year-old woman with osteonecrosis of both femoral heads made 7 days after the hip arthroplasty shows that the ultrashort metaphyseal-fitting anatomic cementless stems are embedded in a satisfactory position. The acetabular components are embedded in a position of 50 inclination in the right hip and 25 inclination in the left hip. (B) An anteroposterior view of both hips of the above patient made 13 years after the hip arthroplasty demonstrates the acetabular and ultrashort metaphyseal-fitting anatomic cementless stems are solidly fixed with no evidence of osteolysis. Grade I calcar resorption is evident in both hips.
mechanical failure (0.7% at 13.1 years) despite a high patient activity level. We feel that several factors were responsible for our good results in young patients: improved design (the proximalfitting designs of the femoral stem including pronounced lateral flare, and anteroposterior build-up), surgical technique for implantation of the cementless stem, the strong trabecular bone in young patients, and use of the alumina delta ceramic-on-alumina delta ceramic bearing. Our results are consistent with those from other studies [10-13,17,18,21,25]. Kim et al [13,22-24] reported that their short, anatomic femoral stem had mild stress shielding in the calcar region and it was nonprogressive 1 year after surgery. We believe that an absence of distal stem minimized stress shieldingerelated proximal femoral bone resorption.
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Fig. 3. Computerized tomographic scanning of both hips taken 13 years after surgery reveals no evidence of osteolysis around the acetabular or femoral components.
Many previous studies of the alumina forte ceramic-on-alumina forte ceramic bearings have found little or no osteolysis [9-14]. In the present study, we found no osteolysis. We postulate that extremely low wear and the scant damage of the optionally positioned articular surfaces were insufficient to cause osteolysis. Squeaking or other noises are a significant clinical concern for patients with ceramic-on-ceramic bearing. The reported prevalence of squeaking with alumina forte ceramic-on-alumina forte ceramic bearings has ranged from 1% to 21% [35,36,37]. Hamilton et al. [21] reported the prevalence of squeaking was 7.5% of patients after they used alumina delta-on-alumina delta ceramic bearings. They further reported unexpected findings that higher incidence of squeaking among 36-mm alumina delta-on-alumina delta bearings compared to 28-mm alumina delta-on-alumina delta bearings. In our study, only 2 patients (0.6%) had squeaking sound occasionally during bending over to pick something up on the floor. One of the major concerns regarding ceramic bearings is fracture of the material. Fracture of the alumina forte ceramic head or acetabular alumina forte ceramic liner has been reported in the literature [14-19]. Hamilton et al [21] observed no alumina delta ceramic femoral head fractures in their study, but they observed 3 insertional liner fractures, each occurring when the surgeon was attempting to seat the liner in the cup. They emphasized that the importance of symmetrical seating of the liner before impaction. The absence of an alumina delta ceramic head or liner fracture in the current series is attributed to optimal cup orientation (except one hip with a recurrent dislocation and one hip with a 25 inclination), symmetrical seating of the liner in the cup, and optimal interlocking of the alumina delta head and taper of the stem. There are several strengths in this study. First, drawing from a single center allows specific coordination of surgical technique or implant use throughout the study. Second, relatively a large volume of patients aged <50 years were treated and followed. Third, the follow-up was sufficient to determine the prevalence of osteolysis and loosening. Fourth, the performance of this stem and ceramic bearing was investigated in a group of patients with a high activity level. Finally, activity level data were collected for the patients and can be analyzed as a risk factor for failure. There is a limitation in this study. The performance of all operations by a single surgeon may introduce a bias into interpretation of the data. However, our findings were similar to other published results [18,21]. The similarity of the results between the current series and the other studies appear to mitigate single-surgeon bias. Our minimum 10-year follow-up results with the use of alumina-delta ceramic-on-alumina delta ceramic bearings in patients aged <50 years suggest that cementless acetabular and femoral components provide outstanding fixation and provide a
higher rate of survivorship without evidence of osteolysis or fracture of ceramic material.
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The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Original Article
Alumina Delta-on-Alumina Delta Bearing in Cementless Total Hip Arthroplasty in Patients Aged <50 Years Young-Hoo Kim, MD a, *, Jang-Won Park, MD b, Jun-Shik Kim, MD b a b
The Joint Replacement Center, SeoNam Hospital, Ewha Womans University School of Medicine, Seoul, Republic of Korea The Joint Replacement Center, MokDong Hospital, Ewha Womans University School of Medicine, Seoul, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history: Received 18 January 2016 Received in revised form 1 March 2016 Accepted 7 March 2016 Available online xxx
Background: There are limited studies to evaluate long-term clinical and radiographic outcomes of alumina delta ceramic-on-ceramic bearings in cementless total hip arthroplasty (THA). The purpose of this study was to evaluate the clinical and radiographic results, prevalence of osteolysis, squeaking, and fracture of ceramic material associated with the use of the alumina delta ceramic-on-alumina delta ceramic bearing in cementless THA in patients aged <50 years. Methods: We reviewed the cases of 277 patients (334 hips) who underwent a cementless THA using alumina delta ceramic-on-alumina delta ceramic when they were 50 years or younger at the time of surgery. Demographic data; Harris Hip Score; Western Ontario McMaster Universities Osteoarthritis Index; and University of California, Los Angeles activity score were recorded. Radiographic and computerized tomographic evaluations were used to evaluate implant fixation and osteolysis. Squeaking sound and ceramic fracture were documented. The mean follow-up was 13.1 years (range, 10-14). Results: The mean postoperative Harris Hip Score, Western Ontario and McMaster Universities Osteoarthritis Index score, University of California, Los Angeles activity score were 93 points, 15 points, and 8.6 points, respectively. Two patients had thigh pain (grade 7 points). All acetabular components and all but 2 femoral components were well fixed. Thirty-three hips (10%) exhibited clicking sound, and 2 hips (0.6%) exhibited squeaking sound. No hip had osteolysis or ceramic head or liner fracture. Conclusion: Our minimum 10-year follow-up results with the use of alumina delta ceramic-on-alumina delta ceramic bearings in patients aged <50 years suggest that cementless THA provides a high rate of survivorship without evidence of osteolysis or fracture of ceramic material. © 2016 Published by Elsevier Inc.
Keywords: cementless total hip arthroplasty alumina delta-on-alumina delta clinical results radiographic results squeaking sound ceramic fracture
Although total hip arthroplasties (THAs) have provided durable long-term results, periprosthetic osteolysis related to particulate polyethylene wear debris is considered an important cause of aseptic loosening and late implant failure [1,2]. Concern regarding development of osteolysis attributable to polyethylene wear, particularly in young patients, prompted the introduction of ceramic-on-ceramic bearings to prevent or minimize wear-related osteolysis. Furthermore, to combat the problem of hip instability in THA, larger diameter ceramic, metal, or highly cross-linked polyethylene femoral heads were transitioned [3-7].
No author associated with this paper has disclosed any potential or pertinent conflicts which may be perceived to have impending conflict with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2016.03.016. * Reprint requests: Young-Hoo Kim, MD, The Joint Replacement Center, SeoNam Hospital, Ewha Womans University School of Medicine, #20, Sinjeongipen 1-ro, Yangcheon-gu, Seoul 158-070, Republic of Korea. http://dx.doi.org/10.1016/j.arth.2016.03.016 0883-5403/© 2016 Published by Elsevier Inc.
Recent studies of the alumina forte ceramic-on-alumina forte ceramic bearings with smaller femoral heads (28 or 32 mm) found little or no osteolysis [8-13]. Concerns with alumina forte ceramic bearing remain, including ceramic head [14-16] and, more significantly, liner fracture [17-19]. Therefore, alumina delta ceramic-onalumina delta ceramic (BIOLOX Delta; CeramTec AG, Plochingen, Germany) was developed to address some of the concerns raised with the alumina forte ceramic-on-alumina forte ceramic bearing. The material has a smaller grain size (<0.8 mm) compared with the grain size of alumina forte ceramic (1-5 mm). The mechanical properties of this combination result in a bearing that has improved toughness and wear characteristics when measured in a laboratory setting [20]. There are few studies of alumina delta ceramic-on-alumina delta ceramic bearing, but these are limited by small number of patients aged <50 years and short-term follow-up [18,21]. To our knowledge, there are limited studies to evaluate long-term clinical and radiographic outcomes of alumina delta ceramic-on-alumina
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delta ceramic bearings in cementless THA in large cohorts of patients of age <50 years. The purpose of this study was to evaluate the clinical and radiographic outcomes associated with the use of the alumina delta ceramic-on-alumina delta ceramic bearing in cementless THA in patients aged <50 years. In addition, we determined the prevalence of osteolysis, squeaking, and fracture of ceramic femoral head or acetabular ceramic liner.
Assessed for eligibility (n=313 patients, 384 hips) Excluded (n=27 patients, 37 hips)
Enrollment
Allocation (n=286 patients, 347 hips)
Materials and Methods A consecutive 313 patients (384 hips) underwent THAs from October 2001 to October 2004. Of these, 286 patients (347 hips) met the inclusion criteria and were recruited to participate in the study. All operations were performed by the senior surgeon. The indications for surgery were hip diseases that were severe enough to warrant THA after an adequate trial of nonoperative therapy. Twenty-five patients (34 hips) were excluded because they were older than 50 years (the age limit was chosen arbitrarily), one patient (2 hips) was excluded because the patient had a foot or ankle disorder that limited walking, and one patient (one hip) was excluded because the patient had marked proximal femoral deformity. Contraindications for this ultrashort cementless stem were the patients with high dislocation of the femoral head, severe osteoporosis, or intertrochanteric fracture. The study protocol, including the consent form, was approved by the institutional review board at our institution. A detailed informed consent form was signed by each patient. Nine patients were lost to follow-up, leaving 277 patients (334 hips) available for study with a minimum duration of follow-up of 10 years (mean, 13.1 years; range, 10-14 years; Fig. 1). There were 143 men and 134 women with a mean age (standard deviation) of 48.2 (11.3) years (range, 21-49 years) at the time of surgery. The mean height (standard deviation) was 165.7 (10.2) cm (range, 157-186 cm), and the mean body weight (standard deviation) was 78 (9.7) kg (range, 68-121 kg). The mean body mass index (standard deviation) was 28.9 (10.1) kg/m2 (range, 27.2-34.6 kg/m2). The diagnosis was osteonecrosis of the femoral head in 124 patients (45%), osteoarthritis secondary to developmental dysplastic hip in 115 (42%), osteoarthrosis secondary to childhood pyogenic arthritis in 15 (5%), traumatic arthritis in 13 (5%), femoral neck fracture in 6 (2%), and rheumatoid arthritis in 4 (1%; Table 1). On the contrary to westerners, the predominant diagnosis was osteonecrosis related to excessive alcohol consumption and very low incidence of osteoarthritis of the hip joint in the current patient cohorts. All operations were performed by the senior author using a posterolateral approach. The ultrashort anatomic cementless stem (Proxima; DePuy, Leeds, United Kingdom) was used in all hips. The ultrashort anatomic cementless stem is made of titanium alloy and is entirely porous-coated with sintered titanium beads having a mean pore size of 250 mm, to which a 30-mm-thick hydroxyapatite coating is applied, except at the distal tip. The femoral neck was cut horizontally at the head-neck juncture. The broach was inserted into the divided femoral neck and driven distally in a varus direction by hammer blows and then steadily tilted in the correct alignment while advancing into the femoral metaphysis. We refer to this technique as the “round-the-corner” technique [22-25]. The size of the femoral component was selected not by a canal fill but by the torsional stability of the stem as dictated by bone quality. The real component was 0.5 mm larger than that of the prepared metaphysis. We used a 36-mm-diameter Biolox delta ceramic liner when a cup size was >52 mm, and a 32-mm Biolox delta ceramic liner was used when a cup size was <52 mm. A 36-mm-diameter Biolox delta ceramic femoral head (CeramTec) was used in 283 hips
Follow-up
Before 2 years (n=284 patients, 344 hips) Lost to follow-up (n=2 patients, 3 hips) Between 2-5 years (n=281 patients, 340 hips) Lost to follow-up (n=3 patients, 4 hips) Between 5-10 years (n=279 patients, 337 hips) Lost to follow-up (n=2 patients, 3 hips) Between 10-14 years (n=277 patients, 334 hips) Lost to follow-up (n=2 patients, 3 hips)
Analysis (n=277 patients, 334 hips) Fig. 1. CONSORT flow diagram.
(85%), and a 32-mm-diameter Biolox delta ceramic femoral head was used in the remaining 51 hips (15%). A cementless Pinnacle cup (DePuy, Warsaw, IN) and a 36-mm-internal-diameter Biolox delta ceramic liner were used in 283 hips (85%), and a 32-mm-internaldiameter Biolox delta ceramic liner was used in the remaining 51 hips (15%). In 304 hips (91%), the solid acetabular component was fixed with use of a press-fit technique only; in the remaining 30 hips (9%), 1 or 2 screws were inserted for fixation of the cups via the screw holes.
Table 1 Demographic Data of Patients. Number of Patients (Hips) Male:female Mean age (range, SD), y Mean weight (range, SD), kg Mean height (range, SD), cm Mean BMI (kg/m2) Diagnosis, n (%) Osteonecrosis Ethanol associated Idiopathic steroid use Osteoarthritis secondary to developmental dysplastic hip Osteoarthritis secondary to childhood pyogenic arthritis Traumatic arthritis Femoral neck fracture Rheumatoid arthritis Duration of follow-up (y) SD, standard deviation; BMI, body mass index.
277 (334) 143:134 48.2 (21-49, 11.3) 78 (68-121, 9.7) 165.7 (157-186, 10.2) 28.9 (27.2-34.6, 10.1) 124 69 44 115
(45) (56) (35) (42)
15 (5) 13 6 4 13.1
(5) (2) (1) (10-14)
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Patients were mobilized on the second postoperative day and progressed to full weight-bearing with a walking frame or crutches as comfort permitted; they were advised to use a walking aid for 6 weeks. The patients were reviewed at 3 months, 1 year, and every 2-3 years thereafter. The Harris Hip Score [26] was recorded at each visit, as was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score [27]. Thigh pain was scored on a 10-point visual analog scale [28] where 0 represents no pain and 10 represents severe pain, and activity level was assessed using the University of California, Los Angeles (UCLA) activity score at the most recent follow-up [29]. Also, the patient's satisfaction was assessed as fully satisfied, satisfied, dissatisfied, and fully dissatisfied. All the data were obtained by one observer who was not part of the surgical team. Any clicking or squeaking sound from the ceramic-on-ceramic bearing was recorded only by asking the patient. Radiological evaluation was undertaken at 3 months and 1 year postoperatively, and at each subsequent visit thereafter. A supine anteroposterior radiograph of the pelvis with both hips in 15 of internal rotation and no abduction and a cross-table lateral and iliac oblique radiograph of each hip were obtained 7 days postoperatively and at each subsequent visit. The femoral morphology was determined preoperatively using Dorr's system of classification [30]. Anteversion and inclination of the acetabular component were measured by the method of Engh et al [31]. Definite loosening of the femoral component was defined when there was progressive axial subsidence of >3 mm or a varus or a valgus shift of >3 [32]. Radiographs were analyzed by a research associate with no knowledge of the patient's name. The intraobserver error in all the radiographic measurements was determined by intraclass correlation coefficient after repeated measurements for 3 times at 3-day intervals. This was 0.96 (0.94-1.00), indicating excellent reproducibility. The fixation of the femoral component was classified as osseointegrated, fibrous stable, or unstable [30]. Stress shielding was graded on the radiographs at the final follow-up according to the classification of Engh and Bobyn [32]. The size and location of osteolytic lesions were assessed using the technique described by Zicat et al [33]. At the last follow-up, all patients underwent computerized tomographic (CT) scanning using a multislice scanner (General Electric Light Plus; GE Medical Systems, Milwaukee, WI) to determine osteolysis. The scan sequence was between the posterior superior iliac spine and 10 cm below the stem tip, using contiguous 2.5-mm slices. Osteolysis was defined as any nonlinear region of periprosthetic cancellous bone loss with delineable margins. One author examined all radiographs and CT scans. Survivorship analysis was performed with use of the KaplanMeier method [34], with revision for any reason as one end point and revision due to mechanical failure (clinical and radiographic evidence of aseptic loosening) at the time of follow-up as the other end point. We determined differences in continuous variances (Harris Hip Score and range of motion) between preoperative and postoperative results with use of a Student paired t test and differences in categorical variances (details of functional evaluation and deformity according to the Harris Hip Score) and limb length between preoperative and postoperative evaluation with use of a chi-square test. Univariate regression analysis was used to evaluate the relationship, if any, between osteolysis and the variables of age, sex, weight, diagnosis, duration of follow-up, and acetabular inclination and anteversion. All statistical analysis were performed using the Statistical Package Social Science software, version 14.0 (SPSS Inc, Chicago, IL), and statistical significance was set at a P value <.05.
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Results Preoperative Harris Hip Score, WOMAC score, and UCLA activity score improved significantly at the final follow-up (Table 2). The mean preoperative Harris Hip Score (standard deviation) was 39 (19.9) points (range, 10-51 points), and the mean postoperative Harris Hip Score (standard deviation) was 93 (11.7) points (range, 70-100 points). The mean preoperative total WOMAC score (standard deviation) was 64 (19) points (range, 51-85 points), and the mean postoperative total WOMAC score (standard deviation) was 15 (8) points (range, 5-25 points). The mean preoperative UCLA activity score was 2.4 points (range, 1-3 points), and the mean postoperative UCLA activity score was 8.6 points (range, 8-10 points). All but 2 patients (grade 7 points) had no thigh pain. Dependence on walking aids, ability to negotiate stairs, public transportation, to put on footwear, and to cut toe nails were improved markedly after the operation. Two hundred seventy-five patients (99.3%) were satisfied with the outcome of the operation. The 2 patients (0.7%) were dissatisfied because of pain resulted from aseptic loosening (Table 2). Fifty-eight of 277 patients (21%) changed from work involving heavy manual labor before the operation to sedentary work after the operation. The remaining 219 patients (79%) remained in the previous occupation after the operation. All patients were advised not to participate in highimpact sports or heavy labor work. Preoperatively, the Dorr isthmus ratio [30] ranged from 0.32 to 0.49. Two hundred forty-one hip (87%) were Dorr type A, 16 (6%) were type B, and 20 (7%) were type C. As seen on the postoperative radiograph, 269 femoral stems (97%) were neutral and 8 (93%) were in varus (<5 ). The mean inclination and anteversion of the acetabular component were 42 (range, 25 -52 ) and 21 (range, 17 -25 ), respectively. All hips had osseous integration of the acetabular components. All but 2 hips had osseous integration of the femoral components. Two hips (0.7%) exhibited an aseptic loosening of the femoral component (Table 3). When both an anteroposterior radiograph and an iliac oblique radiograph were examined, no hip displayed femoral or acetabular osteolysis. No femoral or acetabular osteolysis was identified in all hips by CT scans (Figs. 2 and 3). Thirty-three of 334 hips (10%) had clicking sound, and 2 hips (0.6%) exhibited squeaking sound. No hip had a fracture of the ceramic femoral head or acetabular ceramic liner. No hip had a revision for aseptic loosening. Kaplan-Meier survivorship analysis revealed a 99.7% survival rate (95% CI, 0.94-1.00) of the acetabular component and 99.3% survival rate (95% CI, 0.92-1.00) of the femoral component as the end point of revision or aseptic loosening at 13.1 years.
Table 2 Clinical Results. Parameter
Preoperative
Postoperative
Harris Hip Score (points)a 1y 5y 10 y 13.1 y Thigh pain at the final follow-up WOMAC score (points)a UCLA activity scorea Clicking sound Squeaking sound
39 ± 19.9 (10-51)
d
d d d d d
95 ± 3.9 94 ± 6.1 93 ± 6.8 93 ± 11.7 2 Hips
64 ± 19 (51-85) 2.4 (1-3) d d
15 ± 8 8.6 5 hips 0 hip
(73-100) (70-100) (70-100) (70-100) (0.6%; loosening stem) (5-25) (8-10) (1.5%) (0%)
WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index; UCLA, University of California, Los Angeles. a The values are given as the mean and the standard deviation, with the range in parentheses.
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Table 3 Radiographic Results. Parameter Dorr bone type, n (%) A B C Acetabular component positiona ( ) Inclination Anteversion Femoral component position, n (%) Neutral position Varus position Valgus position Center of rotationa Horizontal (mm) Vertical (mm) Femoral offseta (mm) Abductor moment arma (mm) Femoral neck lengtha (mm) Limb length discrepancyb (mm) Radiolucent line (>1 mm), n (%) Migration of the acetabular component, n (%) Migration of the femoral component, n (%)
Findings 241 (87) 16 (6) 20 (7) 42 (35-47) 21 (17-25) 269 (97) 8 (3) 0 (0) 45 18 44 49 37 0.3 ± 0.4 0 0 2 Hips
(39-53) (14-24) (38-83) (39-88) (30-41) ( 1.5 to 1.1) (0) (0) (0.6%)
a
The values are given as the mean, with the range in parentheses. The values are given as the mean and standard deviation with the range in parentheses. b
Complications Five of 334 hips (1.5%) had a dislocation postoperatively. Four of these were treated with closed reduction and an abduction brace for 3 months, and no further dislocation occurred. One of 5 hips had a recurrent dislocation and a cup was revised. Three hips (0.9%) had intraoperative undisplaced calcar fracture. These fractures were fixed with cerclage cables, and all were healed without compromise of stem stability. These patients were allowed to partial weight-bearing for 3 months. Discussion The alumina delta ceramic-on-alumina delta ceramic bearing was developed to address some of the concerns with the alumina forte ceramic-on-alumina forte ceramic design. The midterm or long-term studies on the current generation of cementless THAs with an alumina delta-on-alumina delta ceramic bearing in patients aged <50 years are limited. The long-term results of cementless ultrashort metaphyseal-fitting anatomic THA with an alumina delta ceramic-on alumina delta ceramic bearing in our patients aged <50 years demonstrated low incidence of thigh pain and very low incidence of aseptic loosening. Furthermore, there was no osteolysis on radiographs and CT scans. Several authors [8,11,12] reported on alumina forte-on-alumina forte ceramic bearings, and mean Harris Hip Scores were between 95 and 97 points in the short-and long-term follow-up. Hamilton et al [18] reported on midterm results of alumina delta ceramic-onalumina delta ceramic THA, and the mean Harris Hip Score was 94.1 points at mean 5.3 years follow-up. Harris Hip Score in our study, although longer follow-up, is similar to other report [18]. Thigh pain is sometimes associated with the use of cementless femoral components [22,23]. The low incidence of thigh pain in our patients may be attributable to the rigid axial and torsional stability of the femoral component in the proximal femur and an absence of contact between the distal stem and the femoral cortex. Many previous reports [10-12,22-25] suggested that fixation of a current generation of cementless THAs in young patients is quite encouraging. Our data revealed that there was a low incidence of
Fig. 2. (A) An anteroposterior view of both hips of a 36-year-old woman with osteonecrosis of both femoral heads made 7 days after the hip arthroplasty shows that the ultrashort metaphyseal-fitting anatomic cementless stems are embedded in a satisfactory position. The acetabular components are embedded in a position of 50 inclination in the right hip and 25 inclination in the left hip. (B) An anteroposterior view of both hips of the above patient made 13 years after the hip arthroplasty demonstrates the acetabular and ultrashort metaphyseal-fitting anatomic cementless stems are solidly fixed with no evidence of osteolysis. Grade I calcar resorption is evident in both hips.
mechanical failure (0.7% at 13.1 years) despite a high patient activity level. We feel that several factors were responsible for our good results in young patients: improved design (the proximalfitting designs of the femoral stem including pronounced lateral flare, and anteroposterior build-up), surgical technique for implantation of the cementless stem, the strong trabecular bone in young patients, and use of the alumina delta ceramic-on-alumina delta ceramic bearing. Our results are consistent with those from other studies [10-13,17,18,21,25]. Kim et al [13,22-24] reported that their short, anatomic femoral stem had mild stress shielding in the calcar region and it was nonprogressive 1 year after surgery. We believe that an absence of distal stem minimized stress shieldingerelated proximal femoral bone resorption.
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Fig. 3. Computerized tomographic scanning of both hips taken 13 years after surgery reveals no evidence of osteolysis around the acetabular or femoral components.
Many previous studies of the alumina forte ceramic-on-alumina forte ceramic bearings have found little or no osteolysis [9-14]. In the present study, we found no osteolysis. We postulate that extremely low wear and the scant damage of the optionally positioned articular surfaces were insufficient to cause osteolysis. Squeaking or other noises are a significant clinical concern for patients with ceramic-on-ceramic bearing. The reported prevalence of squeaking with alumina forte ceramic-on-alumina forte ceramic bearings has ranged from 1% to 21% [35,36,37]. Hamilton et al. [21] reported the prevalence of squeaking was 7.5% of patients after they used alumina delta-on-alumina delta ceramic bearings. They further reported unexpected findings that higher incidence of squeaking among 36-mm alumina delta-on-alumina delta bearings compared to 28-mm alumina delta-on-alumina delta bearings. In our study, only 2 patients (0.6%) had squeaking sound occasionally during bending over to pick something up on the floor. One of the major concerns regarding ceramic bearings is fracture of the material. Fracture of the alumina forte ceramic head or acetabular alumina forte ceramic liner has been reported in the literature [14-19]. Hamilton et al [21] observed no alumina delta ceramic femoral head fractures in their study, but they observed 3 insertional liner fractures, each occurring when the surgeon was attempting to seat the liner in the cup. They emphasized that the importance of symmetrical seating of the liner before impaction. The absence of an alumina delta ceramic head or liner fracture in the current series is attributed to optimal cup orientation (except one hip with a recurrent dislocation and one hip with a 25 inclination), symmetrical seating of the liner in the cup, and optimal interlocking of the alumina delta head and taper of the stem. There are several strengths in this study. First, drawing from a single center allows specific coordination of surgical technique or implant use throughout the study. Second, relatively a large volume of patients aged <50 years were treated and followed. Third, the follow-up was sufficient to determine the prevalence of osteolysis and loosening. Fourth, the performance of this stem and ceramic bearing was investigated in a group of patients with a high activity level. Finally, activity level data were collected for the patients and can be analyzed as a risk factor for failure. There is a limitation in this study. The performance of all operations by a single surgeon may introduce a bias into interpretation of the data. However, our findings were similar to other published results [18,21]. The similarity of the results between the current series and the other studies appear to mitigate single-surgeon bias. Our minimum 10-year follow-up results with the use of alumina-delta ceramic-on-alumina delta ceramic bearings in patients aged <50 years suggest that cementless acetabular and femoral components provide outstanding fixation and provide a
higher rate of survivorship without evidence of osteolysis or fracture of ceramic material.
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