Abstract
Introduction:
There has been a debate on the use of ceramic-on-ceramic coupling with the retained femoral stem in isolated acetabular revision. The purpose of this study was to retrospectively review the results and complications of isolated revision of the acetabular component using alumina-on-alumina bearings.
Methods:
Between August 2010 and December 2013, 22 patients (23 hips) with a mean age of 60.74 years (40–73) underwent isolated revision of the acetabular component from metal-on-polyethylene to alumina-on-alumina bearings without using a metal sleeve on the undamaged trunnion. All patients completed clinical and radiographic evaluation.
Results:
At a mean follow-up of 3 years (2–5.5), all patients had a significant improvement in the clinical outcome, including Harris Hip Score (84.9 vs. 43, p < 0.001), West Ontario McMaster University Osteoarthritis Index Score (14.4 vs. 49.2, p < 0.001), and visual analogue pain score (1.42 vs. 6.63, p < 0.001). Complications included one aseptic loosening of the acetabular component and three noisy hips (click only). No fracture of the ceramic bearings, dislocation, infection, or squeaking noise were observed in any of the patients.
Conclusion:
Isolated revision of the acetabular component to alumina-on-alumina bearings on the undamaged trunnion may be considered if there is no available titanium sleeves. Our study showed a satisfactory early outcome with minimal complications. However, a longer term follow-up study is necessary.
Introduction
The durability of a total hip prosthesis has been a problem when it is implanted in younger populations. The indications for revision total hip arthroplasty (THA) include osteolysis, mechanical loosening, infection, and recurrent dislocation. 1 Osteolysis secondary to polyethylene (PE) wear remains the most common cause of late failure in THA. 1 Acetabulum osteolysis is far more common than that of the femoral side. Therefore, orthopedic surgeons face the dilemma of whether to retain a well-fixed cementless femoral component during revision THA.
The advantages of isolated revision of the acetabulum component include reduced operating time, less blood loss, and preservation of the femoral bone stock. 2,3 On the other hand, retaining the femoral component will compromise the operation field when preparing the acetabulum side and may cause a malposition of the acetabular component and result in an increased risk of postoperative dislocation. A dislocation rate as high as 20% was reported if isolated revision of the acetabular component was performed. 4 For young and active patients, the least wearing bearings couple, such as ceramic on ceramic (CoC) articulation, is a prudent choice to sustain a longer lifespan for the revised hip prosthesis. However, fracture of the ceramic head on used trunnions in isolated acetabular revisions has been reported. 5 The manufacturers do not recommend the use of ceramic heads on a retained femoral stem because trunnion damage might occur during removal of the femoral head or present before revision surgery.
In our institution, third-generation ceramic bearings are used on trunnions of well-fixed femoral components, if the trunnions are not damaged preoperatively or during removal of the metal head in revision hip arthroplasty. This is because the local manufacturer (Wright Medical Technology, Inc., Arlington, Tennessee, USA) does not provide metal sleeves for this situation. The purpose of this study was to retrospectively evaluate the clinical and radiological outcomes and complications of patients that underwent isolated revision of the acetabular component with the use of third-generation CoC bearings from a single manufacturer.
Patients and methods
This study was approved by the Institutional Review Board of our institute. We retrospectively reviewed all patients from August 2010 to December 2013 who underwent isolated revision of a failed acetabular component from metal-on-PE bearings to alumina-on-alumina bearings from the same manufacturer (Wright Medical Technology, Inc.). Exclusion criteria were patients with peri-prosthetic joint infection, having had a revision of both components, having had revision surgeries not performed by the same surgeon, and use of revised bearings other than third-generation CoCs or those provided by other manufacturers. The retained trunnion was evaluated by visual inspection using the criteria of corrosion and fretting scores 6 (Table 1). Revision arthroplasties with CoC bearings were not used if the corrosion and fretting scores were more than 2. Six patients had trunnion damage scores >2 and were excluded from the study.
Corrosion and fretting scores.
All the CoC bearing components were derived from a single manufacturer, Biolox Forte (CeramTec, Plochingen, Germany), and assembled with a non-cemented acetabular component (Perfecta, Total Hip System; Wright Medical Technology, Inc.). There were 13 males and 9 females with a mean age of 60.74 (40–73) years and a mean body mass index of 26.60 kg/m2 (Table 2). The index arthroplasty was performed because of femoral head osteonecrosis in 11 hips (47.8%), development dysplasia of the hip in 4 (17.4%), osteoarthritis in 4 (17.4%), post-traumatic arthritis in 1 (4.3%), rheumatoid arthritis in 2 (8.7%), and femoral neck fracture in 1 patient (4.3%). The indications for revision arthroplasty included PE wear and osteolysis in 16 hips, aseptic loosening of the acetabulum component in 5, iliopsoas impingement in 1, and acetabular cartilage wear after bipolar hemiarthroplasty in 1 hip. All of the patients underwent an isolated acetabular revision because of a well-fixed non-cemented femoral component.
Demographic data of all patients.
BMI: body mass index.
Surgical technique
All the revision arthroplasty procedures were performed or supervised by a single senior surgeon, using a posterolateral approach. The hip joint was dislocated first and the previous metal head was disassembled from the trunnion with a plastic head impactor. Care was taken to avoid damaging the trunnion. Then, the retained trunnion was inspected carefully, based on the criteria of corrosion and fretting scores. 6 In order to expose the acetabular component, we used two Hohman retractors on the anterior and superior wall of the acetabulum. Then, the posterior capsule flap was sutured to the skin to cover the sciatic nerve and protect it from injury during manipulation. At the revision surgery, we preserved the host bone by using a circumferential extraction tool to remove the well-fixed acetabular component, and then the morcellized or strut allografts were impacted into the acetabular defect and covered with acetabular autograft-paste collected from acetabulum reaming. Then, an acetabulum component (Lineage Acetabular Cup System, Wright Medical Technology, Inc.) was fixed to the acetabulum with screws (Figure 1) and position within a 35–45° inclination and a 20–30° anteversion. If the acetabular bone deficiency was very severe, such as Paprosky Type IIIA or B, and required an anti-protrusio cage in conjunction with a structural allograft, the ceramic bearing material was not used. A structural femoral head allograft was used in one hip and was fixed to the unsupportive superior dome of the acetabulum (Paprosky type IIIA defect) with two screws. The acetabulum component was fixed via a cementless technique in 21 hips and a cemented technique (when the host bone coverage was less than 50% on the surface of the acetabular component) in 2 hips. All the acetabular components were fixed to the acetabular dome with screws. Additional procedures for the osteolysis of the greater trochanter included morcellized allografts in 4 hips only, combined morcellized allografts and wiring in 10 other hips with impending fracture, and Dall-Miles plate fixation for 1 patient due to coexisting periprosthetic fracture of the proximal femur, without loosening of the component (Table 3). A 32-mm modular ceramic head was used in all the patients. Neck lengths were + 3 mm in 2, +0 mm in 8, and −3.5 mm in 13 hips. After relocation of the ceramic head into the acetabular insert and insertion of two hemovac drains, the posterior capsule was tightly repaired to the gluteus medius tendon with reinforcement to prevent dislocation of the hip.

A 53-year-old man with Paprosky type IIC acetabular deficiency secondary to osteolysis. (a) Radiograph before revision arthroplasty (b) Isolated revision of acetabular component with third generation CoC bearings using a cementless acetabular component; postoperative cup inclination: 39°. CoC: ceramic on ceramic.
Characteristic of revision arthroplasty.
Radiographic review
Bone defects on the acetabulum were classified based on the radiographic evaluation and the operative findings as Paprosky 7 type I in eight hips, type IIA in three hips, type IIB in six hips, type IIC in five hips, and type IIIA in one hip. Preoperative plain film was reviewed to evaluate a well-fixed femur component as described by Engh et al. 8 All the cup inclination angles were measured using methods proposed by Lewinnek et al 9 in anteroposterior views of the pelvis (Figure 1). The radiolucent lines are defined as 2 mm or larger in width using DeLee and Charnley zones (zone I to zone III) for the acetabular side and Gruen zones 10,11 (zone I to zone VII) for the femoral side. Incorporation of the bone graft was evaluated using the latest radiography as described by Conn et al. 12 Osteo-integration was identified if the radiodensity was equal and trabecular bridging was evident between the graft and the host bone.
For the rehabilitation protocol, partial weight-bearing ambulation with a walker was requested based on the acetabulum bone defect, using the Paprosky classification and the host bone quality. Eight to twelve weeks were usually required for partial weight-bearing. Patients were allowed to ambulate with a cane or with full weight-bearing, if there was radiographic and clinical evidence of healing of the grafts and osteo-integration of the acetabular component.
All patients were followed up regularly at 1, 3, 6, and 12 months, and then annually after operation. Clinical evaluation included use of the modified Harris Hip Score (HHS) 13 and the West Ontario McMaster University Osteoarthritis Index (WOMAC). 14 The visual analogue score (VAS) was also assessed before operation and postoperatively at the latest follow-up for all patients. All complications, including aseptic loosening, osteolysis, ceramic fracture, dislocation, periprosthetic joint infection, and audible noise, were recorded.
Statistical analysis
The sample size was calculated as mean value and standard deviation. The sample is within normal distribution using Kolmogorov–Smirnov test, p value < 0.2. Paired t test was used for comparison of the pre- and postoperative values. A p value less than 0.05 was considered significant. SPSS software V.21 (SPSS Inc. Chicago, Illinois, USA) was used for statistical analysis.
Results
The mean follow-up was 3 years (2–5.5). The mean HHS improved significantly from preoperative 43 points (30–60) to 84.9 points (62–97) at the latest follow-up (p < 0.001), and the WOMAC score improved significantly from preoperative 49.2 points (34–75) to 14.4 points (4–30) at the latest follow-up (p < 0.001; Figure 2). The VAS pain scale improved from preoperative 6.63 (5–8) to 1.42 (1–3) at the latest follow-up (p < 0.001; Figure 2).

(a) The mean HHS improved significantly from preoperative 43 points to 84.9 points at the latest follow-up (p < 0.001), and the WOMAC score improved significantly from preoperative 49.2 points to 14.4 points at the latest follow-up (p < 0.001). (b) The VAS pain scale improved from preoperative 6.63 to 1.42 at the latest follow-up (P < 0.001). HHS: Harris Hip Score; WOMAC: West Ontario McMaster University Osteoarthritis Index; VAS: visual analogue score.
The mean inclination of the acetabulum component was 40.65° (35–45°) immediately after operation and 40.98° (36–46.8) at the latest follow-up (p = 0.854). All hips with a non-cemented cup revision, except one with an aseptic loosening of the cup, showed bone ingrowth into the reconstructed acetabulum side at the latest follow-up, without a radiolucent line greater than 2 mm. Eleven hips that underwent bone grafting with a morcellized or structural allograft in the proximal femur osteolysis revealed complete incorporation with a trabecular pattern between the host bone and the allograft. Loosening of the femur component was not noticed at the latest follow-up. No immediate or late infection, dislocation or periprosthetic fracture was observed in any patient.
One patient with Paprosky type IIC sustained loosening of the acetabulum component at 2 months postoperation. The revision procedure included isolated revision of the acetabulum component with structural and morcellized allografts with a 58 mm cup size, and the immediate cup inclination was 32°. For the rehabilitation protocol, we requested the patient to do protected weight-bearing ambulation with a walker for at least 12 weeks, but the patient discarded the walker 2 weeks after discharge. Since further migration of the cup was seen at the 2-month follow-up, a re-revision arthroplasty was performed with cage and allograft reconstruction using metal-on-cemented PE. The cage was well fixed and the allograft had healed to the host bone at the 4-year follow-up.
An audible clicking sound was described by three patients, but no squeaking, grinding or snapping was mentioned. The clicking sound was noted occasionally during hip flexion but did not interfere with daily activities, according to the patients’ statements. There were no dislocation, deep infection of the hip, or ceramic fractures, including head and liner, in any of the patients during the follow-up period.
Discussion
Use of the CoC bearing in primary THA has been an attractive option for young and active patients, owing to its low-wear characteristic 15,16 and low rate of osteolysis. 17 –19 The 10-year survival rate for alumina-on-alumina hip prostheses was reported to be 99.0%. 20 The efficacy of its application in revision THA, however, is still a concern. First, ceramic bearing material has the disadvantage of its fragility and the possibility of fracture. 21,22 In primary alumina-on-alumina THAs, the reported rate of ceramic liner fracture was 0.013–0.017%, and that of ceramic head fracture was 0.02–1.2%. 23,24 In theory, the possibility of ceramic fracture will increase in revision procedures because of the complexity of the procedure and the use of a ceramic head on the imperfect trunnion. 5 Second, the postoperative dislocation rate is higher in revision procedures than in primary arthroplasty 25,26 and is even higher (up to 20%) when isolated acetabular revision is performed. 25 Third, the risk of noisy hip, especially squeaking after hard-on-hard articulation such as with ceramic bearings, is a cause for concern. However, the exact etiology of the squeaking in CoC THA is unclear and is likely multifactorial. 27
Many studies have reported mid- to long-term satisfactory results after isolated revision of an acetabular component without revising a well-fixed femoral stem. 28 –31 However, there are only a few reports on isolated acetabular revision using CoC bearings. Jack et al. 32 reported 165 hips with isolated acetabular revision, including 100 alumina and 65 delta bearing couples. At a mean follow-up of 4.8 years, the mean HHS improved significantly from 71.3 to 91.0 points (p < 0.001). Kim et al. 33 reported 166 patients (187 hips) with isolated acetabular revision using CoC bearings under the age of 50 at the time of revision. At a mean follow-up of 15.6 years, 92% (153/166) of patients had a satisfactory outcome.
Fracture of the ceramic bearings is a major concern in primary CoC THA and in revision surgery, because of the brittleness of the ceramic bearings. 21 Jack et al. 32 reported two fractures of the alumina femoral head but no liner fracture in 165 CoC bearings after revision THA. A titanium sleeve was used in both alumina and delta groups during revision. Hannouche et al. 34 reported no fractures among 61 alumina heads implanted on a well-fixed stem without imperfection of the trunnion. Another risk factor for ceramic head fracture is the use of short-neck 28 mm heads. 24 In the current report, we used 32 mm heads in all hips and followed the method suggested by Hannonche et al. 34 to place the ceramic head on the undamaged trunnion of the retained stem. Therefore, metal sleeve was not used between the ceramic head and trunnion in all hips. There were no fractures of the alumina ceramic head in our cases.
Dislocation of the hip is another issue in revision THA. The reported incidence of postoperative dislocation ranged from 1% to 10%. 35,36 It was even higher, up to 22%, after revision procedures. 32 The risk factors for dislocations include surgical approach, component orientation, and component size. 37 A prospective randomized study reported that use of a larger head (36 mm) in primary THA was associated with a lower incidence of dislocation than use of a smaller head (28 mm; 0.8% vs. 4.4%). 38 Revision THA with a 36 mm or 40 mm metallic head has been reported to have a reduced dislocation rate compared with a 32 mm metallic head. 39 Kim et al. 33 reported three dislocations (1.6%) among 187 hips with isolated acetabular revisions using CoC bearings, but they did not mention the size of the dislocated head. Chang et al 40 reported 2 of 42 hips dislocated after revision THA, and a 28 mm ceramic head was used in both dislocated hips. The orientation of the acetabular component is also important in preventing dislocation. One study reported a “safe position” of 15 ± 10 anteversion and 40 ± 10 degrees inclination. 9 Capsule repair is also effective in reducing hip dislocation. Mai et al. reported 2 dislocations among 336 primary CoC THA (0.6%); 32 mm or 36 mm heads were used with 97% of the hips, and the THA was performed through the posterolateral approach employing capsule repair and reinforcement. 41 Our traditional surgical approach for a THA is the posterolateral approach with repair of the posterior capsule and reinforcement to prevent posterior dislocation, 42 which is in accordance with other reports. 32,33 In the current study, we used a 32 mm ceramic head at revision, and the mean inclination of the cup of all patients was 40.98° (36–46.8°); therefore, there were no dislocations during the follow-up period.
Audible noise is another complication that occurs after CoC THA. In our previous study of 125 patients that underwent primary alumina-on-alumina THA using products from the same manufacturer, 3.2% (4 patients) had a clicking sound but no squeaking. 42 In a study of 166 patients (187 hips) who had isolated revision of the acetabular component using CoC bearings, only 5% (9/187) had clicking, but there was no squeaking. 33 In the current study, noisy hips occurred in three patients who had clicking only, but no squeaking; this noise did not affect the clinical outcome, and no revision procedure was required. A longer clinical follow-up and a larger cohort of patients may be necessary to verify the influence of clicking noise on the clinical outcome.
We acknowledge several limitations to this study. First, the patient cohort was small and the follow-up period was short. However, compared with other studies of isolated acetabular revisions using different CoC bearings from different manufacturers, our patients were operated on by a single surgeon using products from a single manufacturer and the same surgical technique—changing MoPE bearings to third-generation CoC bearings with the ceramic head sitting directly on the used trunnion—which makes the results of our study more reliable and consistent. Further, our report focused on the complications of revision THA using CoC bearings. In previous studies, most complications with ceramic bearings, including dislocation, fracture, and squeaking occurred less than 3 years after operation. 32,33,41,43,44 Our mean follow-up period of 3 years is adequate to report complications with ceramic bearings. Second, our study was a retrospective review without a comparison group of patients. Further studies to compare the differences in revision procedures using BIOLOX Delta and BIOLOX Forte CoC bearings are necessary.
Conclusion
Our study demonstrated satisfactory early results with minimal complications on isolated revision of the acetabular component to alumina-on-alumina bearings without the use of a titanium sleeve if the retained trunnion was undamaged.
Footnotes
Acknowledgment
We would like to acknowledge Dr Po Cheng Chen and Mrs Ya-Ju Yang for their help with the statistical analyses of this study.
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
