Ceramic-on-ceramic articulations have been in use in total hip arthroplasty since the 1970s, but early implants had a high failure rate1. More recently developed third-generation alumina ceramic bearings have improved fixation methods as well as a metal-backed acetabular component and improved material properties to resist wear and fracture2. We previously reported the five-year results of third-generation alumina-on-alumina ceramic bearings in cementless total hip arthroplasty3. A consecutive series of 301 cementless primary total hip arthroplasties with alumina bearings was evaluated. At a minimum of five years of follow-up (mean, 6.5 years; range, five to 9.2 years), the survival rate of the prosthesis was 96% with revision for any reason as the end point. Over 98% of the hips (256 of 259) had an excellent or good clinical outcome. All of the patients had improved function, a reduced pain score, and a very high overall satisfaction score (mean, 9.6 of 10; range, 5 to 10). The aim of the present study was to review the results in the same cohort of patients after reevaluation of the clinical outcome, radiographic findings, revision rate, and implant survivorship at a minimum of ten years of follow-up.
Materials and Methods
From June 1997 to February 1999, 301 consecutive primary cementless hip arthroplasties were performed in 283 patients by the two senior authors (W.K.W. and B.A.Z.). The mean age of the patients at the time of the arthroplasty was fifty-eight years, and 145 (51%) were women. There were 163 right-sided arthroplasties (54%) and eighteen bilateral arthroplasties (6%), including six (2%) that were performed simultaneously. The mean patient weight was 77.5 kg (range, 45 to 130 kg), and the mean body mass index was 26.8 kg/m2 (range, 16 to 39 kg/m2). All patients were treated with use of the same implants (Osteonics ABC acetabular component and Secur-Fit or Secur-Fit Plus femoral component; Stryker Orthopaedics, Mahwah, New Jersey), surgical technique, and postoperative management protocol, as described in our previous report3. A third-generation alumina ceramic-on-ceramic bearing material (BIOLOX forte; CeramTec, Plochingen, Germany) was used for the articulation in all cases.
Postoperative clinical and radiograph review was performed at six weeks, one year, two years, and every two years thereafter. A questionnaire based on the system of Johnston et al.4, which included the modified Harris hip score5, was completed by the patient at each review appointment. Specific questions had also been included in the questionnaire to identify the presence of noise in the hip, especially squeaking. If any noise was reported, further details regarding the nature, duration, and functional disturbance were recorded. An anteroposterior radiograph of the pelvis (Fig. 1) and a lateral radiograph of the hip were obtained and were assessed by an arthroplasty fellow who had not been not involved with the surgery. All data were collected prospectively and were stored in a relational database, as described previously6.
Survival analysis was performed with use of the Kaplan-Meier method. The Student t test was used to compare the cortical index in the hips that had sustained a femoral fracture and in matched controls; a p value of <0.05 was considered significant.
Source of Funding
No direct external funding was received for this study.
Twenty-six patients (twenty-seven hips) had died; all had died with the prosthesis in situ from a cause unrelated to the arthroplasty. Twenty-two patients (6.3%, twenty-two hips) were lost to follow-up because they could not be contacted, had moved to other states, or did not wish to participate in further follow-up. Nine revisions (including one repeat revision) involving one or both of the components had been described in the previous five-year follow-up report, and no additional revisions were performed subsequently (see Appendix). The implants in the remaining 227 surviving patients (244 hips) remained in situ at the time of the latest follow-up (Table I). The mean duration of follow-up was 10.9 years (range, 10.1 to 12.8 years). Forty-six of the patients included in the study were unable to attend a clinical review but completed the questionnaire during a telephone interview.
The twenty-two patients who were lost to follow-up were censored from the at-risk group in the survival analysis on the date of the last follow-up. However, the names of these patients were cross-checked against the Australian National Joint Replacement Registry, and none was recorded to have undergone revision arthroplasty elsewhere in Australia or registered as deceased. This group of patients was therefore assumed to be alive and to have a functional hip.
The mean Harris hip score5 had improved from 56 points (range, 17 to 89 points) before surgery to 94 points (range, 57 to 100 points) at the time of the latest follow-up. The result was rated as good or excellent in 95% of the hips, as fair in 3.3%, and as poor in only 1.6%. Groin pain was reported as none or mild in association with 230 (94.3%) of the hips, as moderate in association with nine (3.7%), and as severe in association with five (2.0%). Thigh pain was reported as none or mild in association with a notably greater number of hips (235, 96.3%) and as moderate in association with nine (3.7%). Most patients were satisfied with the results of the surgery; the mean satisfaction score was 9.4 (range, 3 to 10) out of 10 on a visual analog scale, and the score was ≥9 for 86% (209) of the hips.
Radiographic assessment was performed for 184 hips in 172 patients at a minimum of ten years of follow-up. No radiolucency or osteolysis adjacent to the acetabular component had been observed at five years of follow-up. One hip had developed acetabular osteolysis following revision for psoas tendinitis and underwent repeat revision. However, this had been discussed in the previous report and was excluded from the present study because this complication followed revision of the acetabular component. Three hips (1.6%) had developed radiolucency in one Charnley7 zone adjacent to the acetabular component, but there was no evidence of cup migration, loosening, or osteolysis. Five hips (2.7%) had developed radiolucency in one Gruen8 zone adjacent to the femoral stem, but only one hip had loosening and required revision. All of the remaining femoral components since the last report had evidence of stable osseous ingrowth with no subsidence or migration of the stem. Mild stress-shielding (loss of trabecular bone density) was observed in eighteen hips (9.8%), and no severe stress-shielding (with cortical thinning) was observed. Brooker grade-I or II heterotopic ossification9 was observed in thirty-six (19.6%) of the hips, and grade-III or IV heterotopic ossification was observed in eleven (6.0%).
A number of postoperative complications, most of which occurred within the first three years, were previously reported (Table II). One additional dislocation had occurred since the time of the previous report; this dislocation was treated with closed reduction and no further problems were reported. One additional periprosthetic fracture had occurred since the time of the previous report; this was a nondisplaced femoral fracture that was treated conservatively without the need for femoral implant revision. The fracture occurred at 140 months (11.7 years) after surgery, but the ten-year follow-up assessment prior to the fracture had indicated an excellent outcome, and that assessment was included in the analysis.
No fractures of the ceramic head or liner occurred postoperatively. Chipping of the rim of the acetabular liner of one implant had occurred during insertion, but this was replaced with a new liner at the time of the initial surgery. One patient reported a squeaking hip six years and nine months after the surgery, but the squeaking could not be reproduced at the time of the clinical assessment. Further questioning revealed that the squeaking occurred only intermittently at maximum flexion with internal rotation and that no pain or other functional disability had resulted3.
The most common cause of failure in our series was periprosthetic femoral fracture. We analyzed the risk of such a fracture by comparing the cortical index (which reflects the ratio of inner to outer cortical diameter) in femora that developed a periprosthetic fracture with the index in a control group that was matched with regard to sex, age, and body mass index (see Appendix). The difference in the cortical index was not significant (p = 0.348), but the number of femora with a fracture was small.
No further revisions were performed since the five-year report3. The overall survival rate, with revision of the acetabular and/or femoral component for any reason as the end point, was 98% (95% confidence interval [CI], 94.2% to 99.6%) at ten years (Fig. 2). The survival rate with fracture as the end point was 98.6% (95% CI, 96.2% to 99.5%) at ten years (Fig. 3). The survival rate with aseptic loosening as the end point was 99.6% (95% CI, 97.7% to 99.9%) at ten years (Fig. 4). In the worst-case scenario in which all of the patients who were lost to follow-up were assumed to have required revision and were considered failures, the survival rate was 89% (95% CI, 84.5% to 92.3%) at ten years.
The results at ten years of follow-up in this large series of total hip arthroplasties involving a single type of implant with a third-generation ceramic-on-ceramic articulation reinforced the excellent clinical results reported at five years of follow-up. No additional complications leading to further revision had arisen since the previously reported early complications, most of which occurred within the first three years. Clinical outcomes at ten years of follow-up were good and, aside from one case of osteolysis and one case of aseptic loosening, radiographic assessment showed no further evidence of implant failure leading to revision.
Ceramic has been used as an articulating bearing material because of its exceptional material properties. It has superior wear resistance because it is extremely hard, with a high scratch resistance. It also has excellent biocompatibility and is chemically and hydrothermally stable. Although earlier reports involving the use of ceramic-on-ceramic as a bearing material10,11 were not very encouraging because of the reported risk of fracture, more recent studies reported excellent mid-term results3,12,13. The third generation of ceramic has substantially improved material properties resulting from improvements in manufacturing. These improvements have yielded alumina ceramics with much smaller grain size and fewer inclusions, resulting in a harder material with a reduced fracture risk2. The long-term clinical and radiographic results in more recent series involving ceramic-on-ceramic articulations were excellent at ten years14 and at twenty years15. Despite these results, some authors have expressed a variety of concerns regarding the use of ceramic: the small risk of implant fracture leading to catastrophic failure14,16, chipping on insertion3, wear leading to osteolysis11, and squeaking during hip movement17. However, no fracture of either the femoral head or the acetabular component occurred postoperatively in our series. Chipping of the acetabular liner occurred in one hip and squeaking occurred in another hip, but these did not result in any further clinical problems. Both of these hips were functioning well, with high patient satisfaction, at the time of the latest follow-up.
Periprosthetic femoral fracture was the main cause of failure in this series. The majority of the fractures occurred less than one year after surgery, with no fractures occurring intraoperatively. The number of femoral fractures was too small to permit determination of possible causes. Psoas tendinitis was another reason for revision in this series, and previous studies have suggested that a large cup diameter or cup overhang might be associated with the occurrence of this complication18,19. Deliberate attempts to prevent psoas tendinitis by ensuring that no anterior overhang occurred and by leaving the anterior capsule intact to protect the tendon anteriorly have been described previously20.
Recognition of squeaking in ceramic articulations as a clinical problem has increased recently. Although the mechanism is not fully understood, squeaking has been proposed to result from a frictional driving force created when edge loading occurs. This force may cause uncoupling of the acetabular liner and shell that allows the shell or the femoral component to resonate, producing an audible sound21. Although other causes of squeaking may also exist, edge loading appears to be an important causative factor17,21. The prevalence of squeaking was extremely low and not clinically important in our series at ten years of follow-up, despite a high prevalence of edge loading noted previously in retrieved implants3. Other series have reported a prevalence of squeaking ranging from 0.5% to 20.9%17,22-24. However, the prevalence in our series was the lowest at 0.3% despite routine questioning during the follow-up reviews regarding the occurrence of noises. Other authors have also reported the prevalence of squeaking to be lower in hips with the femoral component used in the present series than in hips with other femoral components25. This low prevalence may be due to the greater stiffness and correspondingly higher natural frequency of the femoral component used in the present series, as most of the series with a high reported prevalence of squeaking involved femoral components that were less stiff and had a lower natural frequency26,27.
Overall, our study did not show any clear evidence that ceramic wear or osteolysis were responsible for implant failure or for any other adverse effect in vivo following primary total hip arthroplasty, although we acknowledge that our study has limitations. Ideally, an activity score would have been collected to assess the change in activity level of the patients. Also, our radiographic follow-up was less comprehensive than the clinical follow-up.
The hydroxyapatite-coated cementless acetabular and femoral components used in this study yielded excellent mid-term results that were comparable with those in previously reported series28,29. This provides very encouraging evidence to support the use of this combination of implant components with a third-generation ceramic-on-ceramic articulation for primary hip arthroplasty.
Tables comparing the cortical index in femora that experienced a fracture with the index in matched controls and listing the revisions are available with the online version of this article as a data supplement at jbjs.org.
NOTE: The authors acknowledge Lyn McDonald and Sharon Wales for their assistance in collecting the data.
Investigation performed at the Specialist Orthopaedic Group, North Sydney, New South Wales, Australia
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Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.