The Journal of Arthroplasty xxx (2015) xxx–xxx
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Midterm Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty William G. Hamilton, MD a,b,1, James P. McAuley, MD c, Thomas J. Blumenfeld, MD d, James P. Lesko, PhD e, Sam E. Himden, BA, CCRA e, Douglas A. Dennis, MD f a
Anderson Orthopaedic Research Institute, Alexandria, Virginia Inova Center for Joint Replacement at Mount Vernon Hospital, Alexandria, Virginia London Health Sciences Center–University Hospital, London, Ontario, Canada d Joint Surgeons of Sacramento, Sacramento, California e DePuy, a Johnson & Johnson company, Warsaw, Indiana f Colorado Joint Replacement, Denver, Colorado b c
a r t i c l e
i n f o
Article history: Received 1 October 2014 Accepted 11 February 2015 Available online xxxx Keywords: total hip arthroplasty ceramic outcome total hip replacement bearing surfaces
a b s t r a c t This study reports mid-term results of Delta ceramic on ceramic (COC) in total hip arthroplasty (THA). Subjects received Delta COC THA in a prospective multi-center study with either 28 mm (n = 177) or 36 mm (n = 168) articulations. Annual clinical and radiographic evaluations were performed, and patients were asked about hip noises. At mean 5.3-year follow-up there were 3 (0.9%) post-operative liner fractures. Nine revisions were performed (2 liner fracture, 4 stem loosening, 3 deep infection). Kaplan-Meier survivorship at 6 years was 96.9% (94.0–98.4). Twenty-six (7.5%) subjects reported squeaking, of whom none were revised. One (0.3%) subject could reproduce a sound in clinic. More patients reported squeaking with a 36 mm bearing (28 mm: 7/177, 36 mm: 19/168, P = 0.013). © 2015 Elsevier Inc. All rights reserved.
Wear- and particle-related adverse reactions constitute one of the major problems affecting the long-term survivorship of total hip arthroplasty (THA) [1,2]. The evolving field of bearing technology continues to introduce new technologies to address the problem of bearing surface wear. In addition, the THA patient population is becoming younger, more active, and more obese, and subsequently placing higher demands on the prosthesis and specifically the bearing surface [3]. Alternative bearings in THA have been developed in an attempt to reduce wear-related issues and improve implant longevity [4]. Recent bearing surface combinations include metal-on-polyethylene (MOP) and ceramic-on-polyethylene (COP) with cross-linked polyethylene [5], ceramic-on-ceramic (COC) [6,7], ceramic-on-metal (COM) [4] and metal-on-metal (MOM). Legitimate concerns with MOM bearing
One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.02.047. Study Funding Statement: The institutions of the authors (W.G.H., J.P.M., D.A.D.) have received funding to support this research from DePuy, a Johnson & Johnson company. Ethical Board Review statement: Each author certifies that his or her institution approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research. Level of Evidence: Level 1, high quality prospective study. Reprint requests: William G. Hamilton, MD, Anderson Orthopaedic Research Institute, P.O. Box 7088, Alexandria, VA 22307 (via postal service). 1 Via courier: 2501 Parker's Lane, Suite 200, Alexandria, VA 22306.
couples including ion production and adverse local tissue reactions have led to a drastic reduction in the usage of metal liners [8,9]. The wear rates of cross-linked polyethylene have been shown to be markedly reduced when compared to non-cross-linked polyethylene in both simulator studies and clinical trials, but it is unclear how these bearings will perform in the second decade and beyond [5,10,11]. Furthermore, to combat the problem of hip instability in THA, surgeons have transitioned to using larger diameter femoral heads [12–15]. The use of larger heads, while improving stability, introduces the concern for increased volumetric polyethylene wear as well as trunion corrosion [16,17]. It is clear that longer term data are required to elucidate how clinically significant these concerns will become. COC bearings have the potential to address the concerns of wearrelated osteolysis and soft tissue damage. COC couplings have a long history of clinical success [6,7] with substantially lower wear rates and osteolysis than traditional bearing surfaces [18–21]. Concerns with this bearing surface remain, including ceramic head [22–25] and, more significantly, liner fracture [26–32] as well as noises such as squeaking generated from the bearing surface [13,33–40]. Although there are variations among different countries, other concerns regarding the use of COC articulations include fewer options, the lack of larger head diameters, and cost. Alumina matrix composite (AMC) ceramic (BIOLOX Delta, CeramTec AG, Plochingen, Germany) was developed to address some of the concerns raised with the alumina-on-alumina design. The AMC material consists of 82% alumina and 17% zirconia. The material has a smaller grain size (b 0.8 μm) compared with the grain size of alumina
http://dx.doi.org/10.1016/j.arth.2015.02.047 0883-5403/© 2015 Elsevier Inc. All rights reserved.
Please cite this article as: Hamilton WG, et al, Midterm Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty, J Arthroplasty (2015), http:// dx.doi.org/10.1016/j.arth.2015.02.047
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(1–5 μm). The mechanical properties of this combination result in a bearing that has improved toughness and wear characteristics when measured in a laboratory setting [41]. We previously reported our results using this bearing couple in THA [30]. Since that time, we have collected longer term follow-up and gained experience using the 36 mm couple, which was not described in our initial report. We also asked each patient if they heard any noise from their hip. Because these implants have only recently been approved for use in the United States, there are few reports using this bearing couple with mid- to longer term follow-up. The primary goal of this study is to report on the midterm results of all cases of both 28 mm and 36 mm Delta COC initially implanted as part of USA FDA IDE studies. The purpose was to demonstrate the midterm clinical and radiographic results including survivorship of this new ceramic material and provide an update on complications such as bearing failure and squeaking.
Table 1 Demographics (%, or Mean (SD)). Data Gender Men Women Age (years) Weight (pounds) BMI Primary diagnosis Osteoarthritis Avascular necrosis Post-traumatic arthritis Developmental dysplasia Epiphyseal defect Pre-operative Harris Hip scorea Years follow-upb
COC28 (N = 177)
COC36 (N = 168)
90 (51%) 87 (49%) 56.4 (10.6) 194.6 (45.7) 30.0 (6.3)
91 (54%) 77 (46%) 57.3 (11.0) 188.7 (45.8) 29.0 (6.4)
155 (88%) 12 (7%) 5 (3%) 5 (3%) 0 (0%) 50.6 (10.0) 5.2 (1.6)
147 (88%) 13 (8%) 2 (1%) 4 (2%) 2 (1%) 52.9 (10.7) 5.4 (1.3)
a
Four COC28 Subjects had an incomplete pre-operative Harris Hip evaluation. Mean follow-up was calculated for subjects with Harris Hip score in the 2-year protocol defined window or later (N = 165 COC28, N = 160 COC36). b
Materials and Methods From October 2003 to August 2007, a total of 345 hips were enrolled in two FDA Investigational Device Exemption (IDE) Delta Ceramic-onCeramic THA studies. Institutional Review Board (IRB) approval was obtained at all sites. Both studies were registered on www.clinicaltrials. gov, a registry and results database of publicly and privately supported clinical studies of human participants conducted around the world (28 mm study: NCT #00208507, 36 mm study: NCT #00953719). Inclusion criteria consisted of patients 20 to 75 years of age undergoing primary total hip arthroplasty, for non-inflammatory degenerative joint disease (NIDJD), with a pre-operative Harris Hip Score (HHS) [42] of ≤70 and HHS pain rating of at least moderate pain. Exclusion criteria included inflammatory arthritis, bilateral degenerative joint disease requiring staged or simultaneous bilateral hip arthroplasty, an existing total hip arthroplasty in the contralateral hip with a Harris Hip pain rating of mild or worse and patients who had undergone total hip arthroplasty in their contralateral hip within the past 12 months. Initially, as part of a prospective, randomized, multi-center (8 sites) study comparing ceramic on ceramic to ceramic on polyethylene, 177 patients received the 28 mm Delta ceramic on ceramic bearing (COC28) between October 2003 and December 2005 [30]. Subsequently, a prospective, multi-center, non-randomized supplemental IDE study arm was then launched at 5 of the original 8 study sites to evaluate the 36 mm ceramic bearing (COC36); 168 subjects were enrolled in the COC36 arm between April 2006 and August 2007. The 345 patients make up the COC study cohort for this paper. All patients received a cementless porous coated acetabular cup (Pinnacle, Depuy, Warsaw, IN) and one of five cementless femoral stems based on surgeon preference (AML, Prodigy, Summit Porocoat or Duofix, SROM, or Corail, Depuy, Warsaw, IN). The COC28 group received a ceramic bearing insert (Ceramax, Depuy, Warsaw, IN) with a 28 mm inner diameter. The COC36 group received a ceramic bearing insert (Ceramax, Depuy, Warsaw, IN) with a 36 mm inner diameter. All ceramic bearings and matching diameter femoral heads were BIOLOX Delta AMC (CeramTec AG, Plochingen, Germany). Head-liner mismatch never occurred. Demographics and pre-operative diagnoses were representative of a younger hip arthroplasty population (Table 1). All enrolled subjects were seen at clinic visits pre-operatively, postoperatively at 6 weeks, 6 months, 1 year, and annually thereafter. Each clinic visit included Harris Hip Score assessment and radiographic evaluations as well as reporting of any adverse events. Hips that had a reoperation to remove any index THA component were considered to be revised. Because of concerns regarding squeaking with ceramic bearings, each patient was asked if he/she heard any noise from his or her hip shortly after initiation of the study and each report of noise was recorded as an adverse event. If a patient reported that noise had ever occurred, he/she was asked to describe the quality, frequency and
factors that caused the noise. The patients were also asked to try to reproduce it during their clinic visit. Radiographs included supine anteroposterior (AP) pelvis and AP and lateral views of the proximal femur. All radiographs were evaluated by a single independent reviewer. Radiographs were examined for radiolucencies, interface gaps, acetabular migration or inclination change, and osteolysis. Radiolucencies were defined as gaps between the surface of the prosthesis and the surrounding bone [43]. If present, the maximum width and location of any radiolucencies were noted. Osteolysis was defined as an area of localized loss of trabecular bone or cortical erosion and classified as linear or expansile [44]. Linear osteolytic lesions were measured in millimeters and the regions where they appeared were noted. Linear osteolytic lesion measuring two millimeters or less was considered insignificant. Expansile lesions with a ballooning appearance were noted in the pelvis and femur. If present, expansile pelvic osteolysis was recorded as extending into the ilium, ischium or pubis. Cup abduction angle was measured on an AP pelvis radiograph as the angle between a line tangent to the inferior edges of both teardrops and another line tangent to long axis of the ellipse projected by the rim of the acetabular shell [45]. The following were deemed to be clinically meaningful radiographic findings: radiolucencies N 2 mm, acetabular cup migration N 4 mm, change in cup inclination N 4 degrees, and any osteolysis around the stem or cup. Descriptive statistics include mean values ± standard deviations. Comparisons of the Harris Hip Scores, time when squeaking was first reported and cup abduction angles between the COC28 and COC36 groups were performed using a two-tailed Independent samples t-test. Likewise, the pain, functional, activity, deformity and range of motion components of the Harris Hip Score were also compared. The functional component of the HHS included the responses to the limp, support and distance walked questions. The activities component of the HHS included the responses to the stairs, socks, sitting, and public transportation questions. Fisher's Exact test was used to compare the incidence of dislocation among the COC28 and COC36 groups. Post-hoc univariate logistic regression analyses were carried out on COC28 and COC36 subject data to evaluate the following factors for possible association with squeaking: age, gender, BMI, cup abduction angle, cup size, head size, stem type, and HHS at most recent follow-up. A Kaplan–Meier survivorship analysis [46] using revision for any reason as an endpoint was used to evaluate survivorship. A P-value of 0.05 was defined as the threshold for statistical significance. Results A flow diagram is provided which depicts that the patients lost to follow-up from the IDE studies through minimum 2 and 5 year follow-up (Fig. 1). Comparing the COC28 and COC36 subjects, there
Please cite this article as: Hamilton WG, et al, Midterm Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty, J Arthroplasty (2015), http:// dx.doi.org/10.1016/j.arth.2015.02.047
W.G. Hamilton et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
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Fig. 1. Subject accounting for continued follow-up through 5+ years: March 31, 2014 data.
was no difference in the Harris Hip Scores (94.5 ± 9.9 versus 93.7 ± 10.2, respectively, P = 0.49) at most recent follow-up (mean 5.3 years). There were also no differences in the pain, functional, activity, deformity or range of motion components of the Harris Hip Scores (P ≥ 0.16, Table 2) among the 28 and 36 COC groups. Five-year Kaplan–Meier survivorship and 95% confidence intervals were 97.7% (93.9–99.1) for COC28 and 97.3% (92.9–99.0) for COC36. A total of 9 revisions were performed over the course of the study. There were 3 revisions performed for infection (2 in the COC28 and 1 in the COC36), 4 revisions for stem loosening (2 in the COC28, 2 in the COC36), and 2 revisions for liner fracture (1 in COC28, and 1 in COC 36). The dislocation rate in this series was 3.4% (6/177) for the COC28 arm and 1.8% (3/168) for the COC36 arm (P = 0.50). Radiographic review showed no acetabular demarcation lines or interface gaps greater than 2 mm and no observations of cup migration,
change in inclination angle, cup instability, or osteolysis for any subject at any time period. Among subjects who were not revised, 1 COC28 subject and 1 COC36 subject had femoral stem radiolucencies greater than 2 mm at last follow-up (at 48 months for both subjects). The cup abduction angle was 44 ± 7 degrees for the COC 28 group and 46 ± 6 degrees for the COC 36 group (P = 0.04). There have been no femoral head fractures. There were a total of 3 post-operative ceramic liner fractures: 2 COC28 (2/168, 1.2%) and 1 COC36 (1/168, 0.6%). One of the COC28 liner fractures has been revised and was previously reported [30]; there are no new COC28 liner fractures since that original report. At the time of this current review, the second COC28 post-operative liner fracture has not been revised at 7.65-year follow-up because the patient was asymptomatic and refused revision. The latest Harris Hip score for this subject was 100 (4 years post-op). The COC36 post-operative liner fracture was revised at
Table 2 Harris Hip Scores at Most Recent Follow-up. Variable
Total Harris Hip Score Components of Harris Hip Score Function score (limp, support and distance walked) Activities score (stairs, socks, sitting and public transportation) Deformity score Range of motion score Pain score
Max COC28 Score N Mean Median Min
Max
Std Dev
N
100
165 94.5
98
47
100
9.9
160 93.7
98
33 14
165 31.0 165 13.0
33 14
2 5
33 14
5.3 1.6
160 31.2 160 12.9
4 5 44
165 4.0 165 4.8 165 41.7
4 4.9 44
4 0.0 5.0 0.4 44 5.4
160 4.0 160 4.9 160 40.7
4 1.6 20
COC36 Mean Median Min
COC28 vs. COC36 t-test P-value
Max
Std Dev
50
100
10.2
0.49
33 14
17 5
33 14
3.5 1.7
0.61 0.59
4 4.9 44
4 1.1 10
4 5.0 44
0.0 0.3 7.3
N/A 0.21 0.16
Please cite this article as: Hamilton WG, et al, Midterm Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty, J Arthroplasty (2015), http:// dx.doi.org/10.1016/j.arth.2015.02.047
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W.G. Hamilton et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
Fig. 2. Oblique view of COC36 subject with fractured liner at 19 months post-operative.
20 months. The patient presented with hip “clicking” and radiographs showed that there had been a failure of the ceramic liner (Fig. 2). The fractured ceramic liner was removed and the acetabular cup was left in place. Examination of the explanted liner (Fig. 3) demonstrated evidence that the fracture was a result of component-to-component impingement. A total of 3 intra-operative ceramic liner fractures occurred in COC subjects: 2 COC28 (2/177, 1.1%) that were previously described [30] and 1 COC36 (1/168, 0.6%). All of these intra-operative liner fractures occurred when attempting to seat the liner. One subject recieved a replacement ceramic liner and was followed in the study, without any subsequent adverse events related to the bearing surface. There were 26 (26/345, 7.5%) patients who reported hearing squeaking from their hip (7 in COC 28, 7/177, 4.0%; 19 in COC36, 19/ 168, 11.3%). These patients were seen annually over the course of the study, so these 26 reports occurred over 197 visits; 21 patients only reported squeaking at one office visit. Squeaking was first reported at 3.8 ± 1.6 years after surgery for the COC28 group and at 3.2 ± 1.7 years for the COC36 group (P = 0.43). The mean Harris hip score for these patients was 93.8, and none of these patients were revised or requested revision. There was no difference in Harris Hip Scores between those patients that reported squeaking and those that did not (93.8 vs 94.5, P = 0.735). There was no association between different stem designs and the incidence of squeaking. There was no association between acetabular abduction angle and the incidence of squeaking (squeaking present: 46.7°; squeaking absent: 45.0°, P = 0.389). The factors that were found to be associated with squeaking included 36 mm head size (P = 0.013), higher BMI in the COC28 subjects (P = 0.050; 6 of 7 subjects who reported squeaking had a BMI N 30), and gender in the COC36 subjects (P = 0.042; 13 of 19 subjects who reported squeaking were female). None of the COC28 patients and 1 of the COC36 (1/345, 0.3%) could reproduce squeaking during a clinic visit. In this patient, while standing with the knees stiff and bending over at the waist 90 degrees, the sound could be reproduced while the patient began to stand upright. Discussion One of the major limitations to the long-term survival of a total hip arthroplasty is particle induced osteolysis. While the development of osteolysis is related to volumetric wear, particle size, and the host response to the wear debris, the reduction of wear remains a priority in THA. This has become more important with the rise in the number of THAs performed in the United States, the younger ages at which arthroplasty is being performed, and increasing life expectancy [3]. It is well-accepted that ceramic-on-ceramic bearings have the lowest wear rate of any bearing couple available [47,48], so identifying a complication rate is paramount to determine the role that these bearings have in THA today. The limitations of this study include use of a multi-surgeon, multicenter design, which allowed the surgeon to determine the surgical
Fig. 3. Explanted COC36 fractured liner, showing sizes of the various fragments.
approach and the use of one of several FDA approved stems. Although cup abduction was measured, cup and stem anteversion were not assessed and the absence of this data is a weakness of the paper. In this study, we report the midterm results for a Delta ceramic on ceramic couple using both 28 mm and 36 mm heads. The survivorship results are similar to previously published reports on other ceramicon-ceramic bearings. Capello et al [49] reported the results of a multisurgeon, multi-center study using predominantly a 32 mm bearing composed of BIOLOX Forte-alumina (Stryker, Mahwah, NJ), receiving a modular ceramic liner. The estimated 10-year survivorship for revision for any reason was 95.9% [49]. This same group recently reported the 10-year survivorship for bearing-related revisions to be 100% for System I and 98.6% for System II [6]. At 14-year follow-up using an alumina 28 mm head, Sugano et al [50] reported an overall survivorship of 95.7%. The survivorship in this study, although a shorter interval is similar to these reports. One of the major concerns regarding ceramic bearings is fracture of the material. Femoral head fractures remain a rare occurrence with an incidence of 0.004% [51], and we observed no femoral head fractures in this study. We did observe 3 insertional liner fractures, each occurring when the surgeon was attempting to seat the liner in the cup. In a prior study, we described the importance of symmetrical seating of the liner prior to impaction and the need for firm impaction of the liner. It is our hypothesis that these insertional liner fractures, and possibly even the postoperative liner fractures, are a consequence of either leaving the liner asymmetrically seated in the cup or failure to impact the liner forcibly and lock the liner in its taper. Previous reports have documented how this cup can deform when impacted into sclerotic bone, which may have made symmetric seating of this liner more difficult [52]. Furthermore, it is recognized that some surgeons are concerned about the ceramic material and are hesitant to impact the ceramic with enough force to fully lock the head or liner in place, and this complication may have been a consequence of that hesitancy. Incomplete seating of the bearing is not unique to this design. With the use of a metal backed alumina liner, Langdown et al [53] reported incomplete seating in 19/117 cases (16.4%). Using the same system, in which 20 surgeons performed the procedures, a lower yet still concerning rate of 50/694 cases (7.2%) has been reported [54]. In the current study, we observed no obvious cases of incomplete seating of the liner. With the limited number of intra-operative fractures that occurred, we are reluctant to speculate about the role of surgeon experience. However, our data demonstrate that ceramic fractures during insertion remain a concern with BIOLOX Delta liners. Squeaking or other noises are a significant clinical concern for both patients and clinicians with ceramic bearings. In total, 7.5% of patients in this study reported hearing squeaking on at least one occasion. In
Please cite this article as: Hamilton WG, et al, Midterm Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty, J Arthroplasty (2015), http:// dx.doi.org/10.1016/j.arth.2015.02.047
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these patients, there was no difference in clinical scores and no revisions performed for squeaking. Our findings are similar to those of Owen et al [55] who performed a meta-analysis on 16,828 patients with ceramic bearings and found that while the incidence of squeaking was 4.2%, the incidence of revision for squeaking was 0.2%. There have been other reports with higher rates of reported squeaking [56]. Mai et al [56] used a questionnaire format where patients with a COC THA were specifically asked about noised from their hip and 17% reported hearing noise, with 10% describing it as a squeak. Most of the squeaking hips in that study, as in the current study, were pain free and the patients were satisfied with their hips. In another study on alumina COC THA, Keurentjes et al [33] reported that 20.9% of hips reported reproducible squeaking. In a study by Jarrett et al [57] a squeaking rate of 10.7% was reported and 4 of their 14 patients could reproduce squeaking in the clinic. One of those patients underwent revision for recurrent dislocation in association with the squeaking, suggesting that subluxation and/or prosthetic impingement may play a role in the development of stripe wear. Restrepo et al [37] reported a lower 2.7% rate of squeaking with alumina COC, but 6 hips were revised for squeaking in their cohort, indicating the impact of the squeaking on patients exceeded that in the current study where no revisions were performed. In the current study, the increased incidence of squeaking among the COC36 bearings compared to the COC 28 bearings in this study is unexpected. To the best of our knowledge, head size has not previously been identified as an independent factor in the development of squeaking in a ceramic-on-ceramic bearing. We had hypothesized that the use of larger head sizes would reduce the rate of squeaking because of a reduction in neck on liner prosthetic impingement. This impingement has been reported to be one potential source of squeaking [58]. This was not the case in this study. Furthermore, squeaking was distributed across 4 of the 5 stem designs, without a statistically significant trend for higher squeaking with any particular stem. Previous reports have associated the type of titanium alloy with a higher incidence of squeaking [38]. Also, we could not associate acetabular abduction with squeaking in our study which correlates with the findings of Restrepo et al [37] who found no statistically significant difference in acetabular anteversion or inclination between patients who reported squeaking and those that did not. In contrast, Walter et al [39] examined squeaking and non-squeaking control hips and showed that squeaking hips were more likely to have acetabular component positioning outside of an anteversion range of 25 ± 10 degrees and an inclination range of 45 ± 10 degrees. Excessively anteverted hips tended to squeak in gait. In conclusion, at midterm follow-up the 28 mm and 36 mm alumina matrix composite shows excellent function, Harris Hip Scores, and a low rate of complications. The liner fractures are concerning, but since the early fractures that were observed in the first 2 years post-operatively, there have been no additional fractures. We believe that this may implicate the insertional technique and emphasizes the importance of careful attention when seating the liner. The squeaking that is reported in this study remains a concern, and at this time there is no consensus as to cause. The clinical impact of squeaking appears to be low, with similar outcome scores and no revisions for squeaking to date. We continue to carefully follow all patients and believe that this material is an excellent bearing option to address the limitations of other bearing surfaces. Acknowledgment DePuy (Warsaw, IN) provided funding for data collection to the research institutions and surgeons who participated in the IDE studies. Of the authors of this paper, three received funding from DePuy for manuscript preparation, while two are paid employees of DePuy. References 1. Badorf D, Willmann G. Polyethylene in total endoprosthetics—a dead end for permanent implants? Biomed Tech (Berl) 1998;43(5):151.
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THA with Delta ceramic on ceramic: results of a multicenter investigational device exemption trial. Clin Orthop Relat Res 2010;468(2):358. 31. Min BW, Song KS, Kang CH, et al. Delayed fracture of a ceramic insert with modern ceramic total hip replacement. J Arthroplasty 2007;22(1):136. 32. Massin P, Lopes R, Masson B, et al. French Hip & Knee Society (SFHG). Does Biolox Delta ceramic reduce the rate of component fractures in total hip replacement? Orthop Traumatol Surg Res 2014;100(6 Suppl):S317 [Epub 2014 Aug 12]. 33. Keurentjes JC, Kuipers RM, Wever DJ, et al. High incidence of squeaking in THAs with alumina ceramic-on-ceramic bearings. Clin Orthop Relat Res 2008;466(6):1438. 34. Mai K, Verioti C, Ezzet KA, et al. Incidence of ‘squeaking’ after ceramic-on-ceramic total hip arthroplasty. Clin Orthop Relat Res 2010;468(2):413. 35. Matar WY, Restrepo C, Parvizi J, et al. Revision hip arthroplasty for ceramicon-ceramic squeaking hips does not compromise the results. J Arthroplasty 2010; 25(6 Suppl.):81. 36. Ranawat AS, Ranawat CS. The squeaking hip: a cause for concern-agrees. Orthopedics 2007;30(9):738. 37. Restrepo C, Parvizi J, Kurtz SM, et al. The noisy ceramic hip: is component malpositioning the cause? J Arthroplasty 2008;23(5):643.
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38. Restrepo C, Post ZD, Kai B, et al. The effect of stem design on the prevalence of squeaking following ceramic-on-ceramic bearing total hip arthroplasty. J Bone Joint Surg Am 2010;92(3):550. 39. Walter WL, O'Toole GC, Walter WK, et al. Squeaking in ceramic-on-ceramic hips: the importance of acetabular component orientation. J Arthroplasty 2007;22(4):496. 40. Walter WL, Waters TS, Gillies M, et al. Squeaking hips. J Bone Joint Surg Am 2008; 90(Suppl 4):102. 41. Yang CC, Kim RH, Dennis DA. The squeaking hip: a cause for concern-disagrees. Orthopedics 2007;30(9):739. 42. Harris WH. Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty. An end-result study using a new method of result evaluation. J Bone Joint Surg Am 1969;51(4):737. 43. Schmalzried TP, Wessinger SJ, Hill GE, et al. The Harris-Galante porous acetabular component press-fit without screw fixation. Five-year radiographic analysis of primary cases. J Arthroplasty 1994;9(3):235. 44. Zicat B, Engh CA, Gokcen E. Patterns of osteolysis around total hip components inserted with and without cement. J Bone Joint Surg Am 1995;77(3):432. 45. Widmer KH. A simplified method to determine acetabular cup anteversion from plain radiographs. J Arthroplasty 2004;19(3):387. 46. Kaplan EL, Meier P. Nonparametric estimation from incomplete observations. J Am Stat Assoc 1958;53:457. 47. Dorlot JM, Christel P, Meunier A. Wear analysis of retrieved alumina heads and sockets of hip prostheses. J Biomed Mater Res 1989;23(A3 Suppl):299. 48. Hamadouche M, Boutin P, Daussange J, et al. Alumina-on-alumina total hip arthroplasty: a minimum 18.5-year follow-up study. J Bone Joint Surg Am 2002;84-A(1):69.
49. Capello WN, D'Antonio JA, Feinberg JR, et al. Ceramic-on-ceramic total hip arthroplasty: update. J Arthroplasty 2008;23(7 Suppl):39. 50. Sugano N, Takao M, Sakai T, et al. Eleven- to 14-year follow-up results of cementless total hip arthroplasty using a third-generation alumina ceramic-on-ceramic bearing. J Arthroplasty 2012;27(5):736. 51. Willmann G. Ceramic femoral head retrieval data. Clin Orthop Relat Res 2000;379:22. 52. Squire M, Griffin WL, Mason JB, et al. Acetabular component deformation with pressfit fixation. J Arthroplasty 2006;21(6 Suppl 2):72. 53. Langdown AJ, Pickard RJ, Hobbs CM, et al. Incomplete seating of the liner with the Trident acetabular system: a cause for concern? J Bone Joint Surg (Br) 2007; 89(3):291. 54. Miller AN, Su EP, Bostrom MP, et al. Incidence of Ceramic Liner Malseating in Trident® Acetabular Shell. Clinical Orthopaedics and Related Research®. 2009; 467(6):1552. 55. Owen DH, Russell NC, Smith PN, et al. An estimation of the incidence of squeaking and revision surgery for squeaking in ceramic-on-ceramic total hip replacement: a meta-analysis and report from the Australian Orthopaedic Association National Joint Registry. Bone Joint J 2014;96-B:181. 56. Mai MC, Milbrandt JC, Hulsen J, et al. Acetabular cup malalignment after total hip resurfacing arthroplasty: a case for elective revision? Orthopaedics 2009; 32(11):853. 57. Jarrett CA, Ranawat AS, Bruzzone M, et al. The squeaking hip: a phenomenon of ceramic-on-ceramic total hip arthroplasty. J Bone Joint Surg Am 2009;91(6):1344. 58. Walter WL, Kurtz SM, Esposito C, et al. Retrieval analysis of squeaking alumina ceramic-on-ceramic bearings. J Bone Joint Surg (Br) 2011;93(12):1597.
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The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Midterm Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty William G. Hamilton, MD a,b,1, James P. McAuley, MD c, Thomas J. Blumenfeld, MD d, James P. Lesko, PhD e, Sam E. Himden, BA, CCRA e, Douglas A. Dennis, MD f a
Anderson Orthopaedic Research Institute, Alexandria, Virginia Inova Center for Joint Replacement at Mount Vernon Hospital, Alexandria, Virginia London Health Sciences Center–University Hospital, London, Ontario, Canada d Joint Surgeons of Sacramento, Sacramento, California e DePuy, a Johnson & Johnson company, Warsaw, Indiana f Colorado Joint Replacement, Denver, Colorado b c
a r t i c l e
i n f o
Article history: Received 1 October 2014 Accepted 11 February 2015 Available online xxxx Keywords: total hip arthroplasty ceramic outcome total hip replacement bearing surfaces
a b s t r a c t This study reports mid-term results of Delta ceramic on ceramic (COC) in total hip arthroplasty (THA). Subjects received Delta COC THA in a prospective multi-center study with either 28 mm (n = 177) or 36 mm (n = 168) articulations. Annual clinical and radiographic evaluations were performed, and patients were asked about hip noises. At mean 5.3-year follow-up there were 3 (0.9%) post-operative liner fractures. Nine revisions were performed (2 liner fracture, 4 stem loosening, 3 deep infection). Kaplan-Meier survivorship at 6 years was 96.9% (94.0–98.4). Twenty-six (7.5%) subjects reported squeaking, of whom none were revised. One (0.3%) subject could reproduce a sound in clinic. More patients reported squeaking with a 36 mm bearing (28 mm: 7/177, 36 mm: 19/168, P = 0.013). © 2015 Elsevier Inc. All rights reserved.
Wear- and particle-related adverse reactions constitute one of the major problems affecting the long-term survivorship of total hip arthroplasty (THA) [1,2]. The evolving field of bearing technology continues to introduce new technologies to address the problem of bearing surface wear. In addition, the THA patient population is becoming younger, more active, and more obese, and subsequently placing higher demands on the prosthesis and specifically the bearing surface [3]. Alternative bearings in THA have been developed in an attempt to reduce wear-related issues and improve implant longevity [4]. Recent bearing surface combinations include metal-on-polyethylene (MOP) and ceramic-on-polyethylene (COP) with cross-linked polyethylene [5], ceramic-on-ceramic (COC) [6,7], ceramic-on-metal (COM) [4] and metal-on-metal (MOM). Legitimate concerns with MOM bearing
One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.02.047. Study Funding Statement: The institutions of the authors (W.G.H., J.P.M., D.A.D.) have received funding to support this research from DePuy, a Johnson & Johnson company. Ethical Board Review statement: Each author certifies that his or her institution approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research. Level of Evidence: Level 1, high quality prospective study. Reprint requests: William G. Hamilton, MD, Anderson Orthopaedic Research Institute, P.O. Box 7088, Alexandria, VA 22307 (via postal service). 1 Via courier: 2501 Parker's Lane, Suite 200, Alexandria, VA 22306.
couples including ion production and adverse local tissue reactions have led to a drastic reduction in the usage of metal liners [8,9]. The wear rates of cross-linked polyethylene have been shown to be markedly reduced when compared to non-cross-linked polyethylene in both simulator studies and clinical trials, but it is unclear how these bearings will perform in the second decade and beyond [5,10,11]. Furthermore, to combat the problem of hip instability in THA, surgeons have transitioned to using larger diameter femoral heads [12–15]. The use of larger heads, while improving stability, introduces the concern for increased volumetric polyethylene wear as well as trunion corrosion [16,17]. It is clear that longer term data are required to elucidate how clinically significant these concerns will become. COC bearings have the potential to address the concerns of wearrelated osteolysis and soft tissue damage. COC couplings have a long history of clinical success [6,7] with substantially lower wear rates and osteolysis than traditional bearing surfaces [18–21]. Concerns with this bearing surface remain, including ceramic head [22–25] and, more significantly, liner fracture [26–32] as well as noises such as squeaking generated from the bearing surface [13,33–40]. Although there are variations among different countries, other concerns regarding the use of COC articulations include fewer options, the lack of larger head diameters, and cost. Alumina matrix composite (AMC) ceramic (BIOLOX Delta, CeramTec AG, Plochingen, Germany) was developed to address some of the concerns raised with the alumina-on-alumina design. The AMC material consists of 82% alumina and 17% zirconia. The material has a smaller grain size (b 0.8 μm) compared with the grain size of alumina
http://dx.doi.org/10.1016/j.arth.2015.02.047 0883-5403/© 2015 Elsevier Inc. All rights reserved.
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(1–5 μm). The mechanical properties of this combination result in a bearing that has improved toughness and wear characteristics when measured in a laboratory setting [41]. We previously reported our results using this bearing couple in THA [30]. Since that time, we have collected longer term follow-up and gained experience using the 36 mm couple, which was not described in our initial report. We also asked each patient if they heard any noise from their hip. Because these implants have only recently been approved for use in the United States, there are few reports using this bearing couple with mid- to longer term follow-up. The primary goal of this study is to report on the midterm results of all cases of both 28 mm and 36 mm Delta COC initially implanted as part of USA FDA IDE studies. The purpose was to demonstrate the midterm clinical and radiographic results including survivorship of this new ceramic material and provide an update on complications such as bearing failure and squeaking.
Table 1 Demographics (%, or Mean (SD)). Data Gender Men Women Age (years) Weight (pounds) BMI Primary diagnosis Osteoarthritis Avascular necrosis Post-traumatic arthritis Developmental dysplasia Epiphyseal defect Pre-operative Harris Hip scorea Years follow-upb
COC28 (N = 177)
COC36 (N = 168)
90 (51%) 87 (49%) 56.4 (10.6) 194.6 (45.7) 30.0 (6.3)
91 (54%) 77 (46%) 57.3 (11.0) 188.7 (45.8) 29.0 (6.4)
155 (88%) 12 (7%) 5 (3%) 5 (3%) 0 (0%) 50.6 (10.0) 5.2 (1.6)
147 (88%) 13 (8%) 2 (1%) 4 (2%) 2 (1%) 52.9 (10.7) 5.4 (1.3)
a
Four COC28 Subjects had an incomplete pre-operative Harris Hip evaluation. Mean follow-up was calculated for subjects with Harris Hip score in the 2-year protocol defined window or later (N = 165 COC28, N = 160 COC36). b
Materials and Methods From October 2003 to August 2007, a total of 345 hips were enrolled in two FDA Investigational Device Exemption (IDE) Delta Ceramic-onCeramic THA studies. Institutional Review Board (IRB) approval was obtained at all sites. Both studies were registered on www.clinicaltrials. gov, a registry and results database of publicly and privately supported clinical studies of human participants conducted around the world (28 mm study: NCT #00208507, 36 mm study: NCT #00953719). Inclusion criteria consisted of patients 20 to 75 years of age undergoing primary total hip arthroplasty, for non-inflammatory degenerative joint disease (NIDJD), with a pre-operative Harris Hip Score (HHS) [42] of ≤70 and HHS pain rating of at least moderate pain. Exclusion criteria included inflammatory arthritis, bilateral degenerative joint disease requiring staged or simultaneous bilateral hip arthroplasty, an existing total hip arthroplasty in the contralateral hip with a Harris Hip pain rating of mild or worse and patients who had undergone total hip arthroplasty in their contralateral hip within the past 12 months. Initially, as part of a prospective, randomized, multi-center (8 sites) study comparing ceramic on ceramic to ceramic on polyethylene, 177 patients received the 28 mm Delta ceramic on ceramic bearing (COC28) between October 2003 and December 2005 [30]. Subsequently, a prospective, multi-center, non-randomized supplemental IDE study arm was then launched at 5 of the original 8 study sites to evaluate the 36 mm ceramic bearing (COC36); 168 subjects were enrolled in the COC36 arm between April 2006 and August 2007. The 345 patients make up the COC study cohort for this paper. All patients received a cementless porous coated acetabular cup (Pinnacle, Depuy, Warsaw, IN) and one of five cementless femoral stems based on surgeon preference (AML, Prodigy, Summit Porocoat or Duofix, SROM, or Corail, Depuy, Warsaw, IN). The COC28 group received a ceramic bearing insert (Ceramax, Depuy, Warsaw, IN) with a 28 mm inner diameter. The COC36 group received a ceramic bearing insert (Ceramax, Depuy, Warsaw, IN) with a 36 mm inner diameter. All ceramic bearings and matching diameter femoral heads were BIOLOX Delta AMC (CeramTec AG, Plochingen, Germany). Head-liner mismatch never occurred. Demographics and pre-operative diagnoses were representative of a younger hip arthroplasty population (Table 1). All enrolled subjects were seen at clinic visits pre-operatively, postoperatively at 6 weeks, 6 months, 1 year, and annually thereafter. Each clinic visit included Harris Hip Score assessment and radiographic evaluations as well as reporting of any adverse events. Hips that had a reoperation to remove any index THA component were considered to be revised. Because of concerns regarding squeaking with ceramic bearings, each patient was asked if he/she heard any noise from his or her hip shortly after initiation of the study and each report of noise was recorded as an adverse event. If a patient reported that noise had ever occurred, he/she was asked to describe the quality, frequency and
factors that caused the noise. The patients were also asked to try to reproduce it during their clinic visit. Radiographs included supine anteroposterior (AP) pelvis and AP and lateral views of the proximal femur. All radiographs were evaluated by a single independent reviewer. Radiographs were examined for radiolucencies, interface gaps, acetabular migration or inclination change, and osteolysis. Radiolucencies were defined as gaps between the surface of the prosthesis and the surrounding bone [43]. If present, the maximum width and location of any radiolucencies were noted. Osteolysis was defined as an area of localized loss of trabecular bone or cortical erosion and classified as linear or expansile [44]. Linear osteolytic lesions were measured in millimeters and the regions where they appeared were noted. Linear osteolytic lesion measuring two millimeters or less was considered insignificant. Expansile lesions with a ballooning appearance were noted in the pelvis and femur. If present, expansile pelvic osteolysis was recorded as extending into the ilium, ischium or pubis. Cup abduction angle was measured on an AP pelvis radiograph as the angle between a line tangent to the inferior edges of both teardrops and another line tangent to long axis of the ellipse projected by the rim of the acetabular shell [45]. The following were deemed to be clinically meaningful radiographic findings: radiolucencies N 2 mm, acetabular cup migration N 4 mm, change in cup inclination N 4 degrees, and any osteolysis around the stem or cup. Descriptive statistics include mean values ± standard deviations. Comparisons of the Harris Hip Scores, time when squeaking was first reported and cup abduction angles between the COC28 and COC36 groups were performed using a two-tailed Independent samples t-test. Likewise, the pain, functional, activity, deformity and range of motion components of the Harris Hip Score were also compared. The functional component of the HHS included the responses to the limp, support and distance walked questions. The activities component of the HHS included the responses to the stairs, socks, sitting, and public transportation questions. Fisher's Exact test was used to compare the incidence of dislocation among the COC28 and COC36 groups. Post-hoc univariate logistic regression analyses were carried out on COC28 and COC36 subject data to evaluate the following factors for possible association with squeaking: age, gender, BMI, cup abduction angle, cup size, head size, stem type, and HHS at most recent follow-up. A Kaplan–Meier survivorship analysis [46] using revision for any reason as an endpoint was used to evaluate survivorship. A P-value of 0.05 was defined as the threshold for statistical significance. Results A flow diagram is provided which depicts that the patients lost to follow-up from the IDE studies through minimum 2 and 5 year follow-up (Fig. 1). Comparing the COC28 and COC36 subjects, there
Please cite this article as: Hamilton WG, et al, Midterm Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty, J Arthroplasty (2015), http:// dx.doi.org/10.1016/j.arth.2015.02.047
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Fig. 1. Subject accounting for continued follow-up through 5+ years: March 31, 2014 data.
was no difference in the Harris Hip Scores (94.5 ± 9.9 versus 93.7 ± 10.2, respectively, P = 0.49) at most recent follow-up (mean 5.3 years). There were also no differences in the pain, functional, activity, deformity or range of motion components of the Harris Hip Scores (P ≥ 0.16, Table 2) among the 28 and 36 COC groups. Five-year Kaplan–Meier survivorship and 95% confidence intervals were 97.7% (93.9–99.1) for COC28 and 97.3% (92.9–99.0) for COC36. A total of 9 revisions were performed over the course of the study. There were 3 revisions performed for infection (2 in the COC28 and 1 in the COC36), 4 revisions for stem loosening (2 in the COC28, 2 in the COC36), and 2 revisions for liner fracture (1 in COC28, and 1 in COC 36). The dislocation rate in this series was 3.4% (6/177) for the COC28 arm and 1.8% (3/168) for the COC36 arm (P = 0.50). Radiographic review showed no acetabular demarcation lines or interface gaps greater than 2 mm and no observations of cup migration,
change in inclination angle, cup instability, or osteolysis for any subject at any time period. Among subjects who were not revised, 1 COC28 subject and 1 COC36 subject had femoral stem radiolucencies greater than 2 mm at last follow-up (at 48 months for both subjects). The cup abduction angle was 44 ± 7 degrees for the COC 28 group and 46 ± 6 degrees for the COC 36 group (P = 0.04). There have been no femoral head fractures. There were a total of 3 post-operative ceramic liner fractures: 2 COC28 (2/168, 1.2%) and 1 COC36 (1/168, 0.6%). One of the COC28 liner fractures has been revised and was previously reported [30]; there are no new COC28 liner fractures since that original report. At the time of this current review, the second COC28 post-operative liner fracture has not been revised at 7.65-year follow-up because the patient was asymptomatic and refused revision. The latest Harris Hip score for this subject was 100 (4 years post-op). The COC36 post-operative liner fracture was revised at
Table 2 Harris Hip Scores at Most Recent Follow-up. Variable
Total Harris Hip Score Components of Harris Hip Score Function score (limp, support and distance walked) Activities score (stairs, socks, sitting and public transportation) Deformity score Range of motion score Pain score
Max COC28 Score N Mean Median Min
Max
Std Dev
N
100
165 94.5
98
47
100
9.9
160 93.7
98
33 14
165 31.0 165 13.0
33 14
2 5
33 14
5.3 1.6
160 31.2 160 12.9
4 5 44
165 4.0 165 4.8 165 41.7
4 4.9 44
4 0.0 5.0 0.4 44 5.4
160 4.0 160 4.9 160 40.7
4 1.6 20
COC36 Mean Median Min
COC28 vs. COC36 t-test P-value
Max
Std Dev
50
100
10.2
0.49
33 14
17 5
33 14
3.5 1.7
0.61 0.59
4 4.9 44
4 1.1 10
4 5.0 44
0.0 0.3 7.3
N/A 0.21 0.16
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Fig. 2. Oblique view of COC36 subject with fractured liner at 19 months post-operative.
20 months. The patient presented with hip “clicking” and radiographs showed that there had been a failure of the ceramic liner (Fig. 2). The fractured ceramic liner was removed and the acetabular cup was left in place. Examination of the explanted liner (Fig. 3) demonstrated evidence that the fracture was a result of component-to-component impingement. A total of 3 intra-operative ceramic liner fractures occurred in COC subjects: 2 COC28 (2/177, 1.1%) that were previously described [30] and 1 COC36 (1/168, 0.6%). All of these intra-operative liner fractures occurred when attempting to seat the liner. One subject recieved a replacement ceramic liner and was followed in the study, without any subsequent adverse events related to the bearing surface. There were 26 (26/345, 7.5%) patients who reported hearing squeaking from their hip (7 in COC 28, 7/177, 4.0%; 19 in COC36, 19/ 168, 11.3%). These patients were seen annually over the course of the study, so these 26 reports occurred over 197 visits; 21 patients only reported squeaking at one office visit. Squeaking was first reported at 3.8 ± 1.6 years after surgery for the COC28 group and at 3.2 ± 1.7 years for the COC36 group (P = 0.43). The mean Harris hip score for these patients was 93.8, and none of these patients were revised or requested revision. There was no difference in Harris Hip Scores between those patients that reported squeaking and those that did not (93.8 vs 94.5, P = 0.735). There was no association between different stem designs and the incidence of squeaking. There was no association between acetabular abduction angle and the incidence of squeaking (squeaking present: 46.7°; squeaking absent: 45.0°, P = 0.389). The factors that were found to be associated with squeaking included 36 mm head size (P = 0.013), higher BMI in the COC28 subjects (P = 0.050; 6 of 7 subjects who reported squeaking had a BMI N 30), and gender in the COC36 subjects (P = 0.042; 13 of 19 subjects who reported squeaking were female). None of the COC28 patients and 1 of the COC36 (1/345, 0.3%) could reproduce squeaking during a clinic visit. In this patient, while standing with the knees stiff and bending over at the waist 90 degrees, the sound could be reproduced while the patient began to stand upright. Discussion One of the major limitations to the long-term survival of a total hip arthroplasty is particle induced osteolysis. While the development of osteolysis is related to volumetric wear, particle size, and the host response to the wear debris, the reduction of wear remains a priority in THA. This has become more important with the rise in the number of THAs performed in the United States, the younger ages at which arthroplasty is being performed, and increasing life expectancy [3]. It is well-accepted that ceramic-on-ceramic bearings have the lowest wear rate of any bearing couple available [47,48], so identifying a complication rate is paramount to determine the role that these bearings have in THA today. The limitations of this study include use of a multi-surgeon, multicenter design, which allowed the surgeon to determine the surgical
Fig. 3. Explanted COC36 fractured liner, showing sizes of the various fragments.
approach and the use of one of several FDA approved stems. Although cup abduction was measured, cup and stem anteversion were not assessed and the absence of this data is a weakness of the paper. In this study, we report the midterm results for a Delta ceramic on ceramic couple using both 28 mm and 36 mm heads. The survivorship results are similar to previously published reports on other ceramicon-ceramic bearings. Capello et al [49] reported the results of a multisurgeon, multi-center study using predominantly a 32 mm bearing composed of BIOLOX Forte-alumina (Stryker, Mahwah, NJ), receiving a modular ceramic liner. The estimated 10-year survivorship for revision for any reason was 95.9% [49]. This same group recently reported the 10-year survivorship for bearing-related revisions to be 100% for System I and 98.6% for System II [6]. At 14-year follow-up using an alumina 28 mm head, Sugano et al [50] reported an overall survivorship of 95.7%. The survivorship in this study, although a shorter interval is similar to these reports. One of the major concerns regarding ceramic bearings is fracture of the material. Femoral head fractures remain a rare occurrence with an incidence of 0.004% [51], and we observed no femoral head fractures in this study. We did observe 3 insertional liner fractures, each occurring when the surgeon was attempting to seat the liner in the cup. In a prior study, we described the importance of symmetrical seating of the liner prior to impaction and the need for firm impaction of the liner. It is our hypothesis that these insertional liner fractures, and possibly even the postoperative liner fractures, are a consequence of either leaving the liner asymmetrically seated in the cup or failure to impact the liner forcibly and lock the liner in its taper. Previous reports have documented how this cup can deform when impacted into sclerotic bone, which may have made symmetric seating of this liner more difficult [52]. Furthermore, it is recognized that some surgeons are concerned about the ceramic material and are hesitant to impact the ceramic with enough force to fully lock the head or liner in place, and this complication may have been a consequence of that hesitancy. Incomplete seating of the bearing is not unique to this design. With the use of a metal backed alumina liner, Langdown et al [53] reported incomplete seating in 19/117 cases (16.4%). Using the same system, in which 20 surgeons performed the procedures, a lower yet still concerning rate of 50/694 cases (7.2%) has been reported [54]. In the current study, we observed no obvious cases of incomplete seating of the liner. With the limited number of intra-operative fractures that occurred, we are reluctant to speculate about the role of surgeon experience. However, our data demonstrate that ceramic fractures during insertion remain a concern with BIOLOX Delta liners. Squeaking or other noises are a significant clinical concern for both patients and clinicians with ceramic bearings. In total, 7.5% of patients in this study reported hearing squeaking on at least one occasion. In
Please cite this article as: Hamilton WG, et al, Midterm Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty, J Arthroplasty (2015), http:// dx.doi.org/10.1016/j.arth.2015.02.047
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these patients, there was no difference in clinical scores and no revisions performed for squeaking. Our findings are similar to those of Owen et al [55] who performed a meta-analysis on 16,828 patients with ceramic bearings and found that while the incidence of squeaking was 4.2%, the incidence of revision for squeaking was 0.2%. There have been other reports with higher rates of reported squeaking [56]. Mai et al [56] used a questionnaire format where patients with a COC THA were specifically asked about noised from their hip and 17% reported hearing noise, with 10% describing it as a squeak. Most of the squeaking hips in that study, as in the current study, were pain free and the patients were satisfied with their hips. In another study on alumina COC THA, Keurentjes et al [33] reported that 20.9% of hips reported reproducible squeaking. In a study by Jarrett et al [57] a squeaking rate of 10.7% was reported and 4 of their 14 patients could reproduce squeaking in the clinic. One of those patients underwent revision for recurrent dislocation in association with the squeaking, suggesting that subluxation and/or prosthetic impingement may play a role in the development of stripe wear. Restrepo et al [37] reported a lower 2.7% rate of squeaking with alumina COC, but 6 hips were revised for squeaking in their cohort, indicating the impact of the squeaking on patients exceeded that in the current study where no revisions were performed. In the current study, the increased incidence of squeaking among the COC36 bearings compared to the COC 28 bearings in this study is unexpected. To the best of our knowledge, head size has not previously been identified as an independent factor in the development of squeaking in a ceramic-on-ceramic bearing. We had hypothesized that the use of larger head sizes would reduce the rate of squeaking because of a reduction in neck on liner prosthetic impingement. This impingement has been reported to be one potential source of squeaking [58]. This was not the case in this study. Furthermore, squeaking was distributed across 4 of the 5 stem designs, without a statistically significant trend for higher squeaking with any particular stem. Previous reports have associated the type of titanium alloy with a higher incidence of squeaking [38]. Also, we could not associate acetabular abduction with squeaking in our study which correlates with the findings of Restrepo et al [37] who found no statistically significant difference in acetabular anteversion or inclination between patients who reported squeaking and those that did not. In contrast, Walter et al [39] examined squeaking and non-squeaking control hips and showed that squeaking hips were more likely to have acetabular component positioning outside of an anteversion range of 25 ± 10 degrees and an inclination range of 45 ± 10 degrees. Excessively anteverted hips tended to squeak in gait. In conclusion, at midterm follow-up the 28 mm and 36 mm alumina matrix composite shows excellent function, Harris Hip Scores, and a low rate of complications. The liner fractures are concerning, but since the early fractures that were observed in the first 2 years post-operatively, there have been no additional fractures. We believe that this may implicate the insertional technique and emphasizes the importance of careful attention when seating the liner. The squeaking that is reported in this study remains a concern, and at this time there is no consensus as to cause. The clinical impact of squeaking appears to be low, with similar outcome scores and no revisions for squeaking to date. We continue to carefully follow all patients and believe that this material is an excellent bearing option to address the limitations of other bearing surfaces. Acknowledgment DePuy (Warsaw, IN) provided funding for data collection to the research institutions and surgeons who participated in the IDE studies. Of the authors of this paper, three received funding from DePuy for manuscript preparation, while two are paid employees of DePuy. References 1. Badorf D, Willmann G. Polyethylene in total endoprosthetics—a dead end for permanent implants? Biomed Tech (Berl) 1998;43(5):151.
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Please cite this article as: Hamilton WG, et al, Midterm Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty, J Arthroplasty (2015), http:// dx.doi.org/10.1016/j.arth.2015.02.047
