The Journal of Arthroplasty 30 (2015) 282–285

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Squeaking in Large Diameter Ceramic-on-Ceramic Bearings in Total Hip Arthroplasty Stephen M. Tai, MBBS, BSc(Hons), FRCS (Tr & Orth) , Selin Munir, MBiomed, BEng(Hons), William L. Walter, FRACS, FAOrthA, PhD, Simon J. Pearce, MBBS, FRCS (Tr & Orth), William K. Walter, MBBS, FRACS, FAORthA, Bernard A. Zicat, MD, FRACS, FAOrthA Specialist Orthopaedic Group, North Sydney, New South Wales, Australia

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Article history: Received 27 June 2014 Accepted 12 September 2014 Keywords: large diameter ceramic-on-ceramic squeaking cup orientation cementless

a b s t r a c t We analyzed the results of 206 consecutive total hip arthroplasties performed using large diameter ceramic-onceramic bearings. At an average follow-up of 28 months, the mean Harris Hip Score improved from 54 to 92. Fifteen (7.3%) hips were noted to squeak. There was no significant difference between silent and squeaking hips with regards to age, weight, height, BMI, range of movement, femoral head diameter, leg length, and offset or center of rotation. No correlation was present between incidence of squeaking and increasing cup inclination and anteversion. 5.2% of cups orientated within Lewinnek's safe zone squeaked. No hips required revision for squeaking. While large diameter ceramic bearings may produce squeaking, our early results of surgery using large head ceramic bearings are encouraging. However, long-term follow-up is required. © 2014 Elsevier Inc. All rights reserved.

In the quest to achieve better long-term clinical and functional outcome after total hip arthroplasty (THA), prosthesis and bearing designs is continually evolving. Increasing demands are being placed on THAs by higher levels of patient activity and longer life expectancy. Therefore, the ideal bearing surface would allow for recreation of natural hip motion, while displaying excellent wear properties. Large diameter femoral head bearings were designed with these needs in mind. Conventional polyethylene is associated with wear debris-induced osteolysis [1] and hence the last decade has seen an increase in the use of hard-on-hard bearings in THA [2]. However, concerns now exist regarding the use of metal-on-metal bearings as they have associations with elevated metal ion levels and pseudotumor formation [3]. In contrast, ceramic-on-ceramic bearings have been shown to demonstrate excellent wear properties [4]. Ceramic liners are now commonly used in combination with a rough or porous coated titanium shell, with excellent rates of survival and patient satisfaction results reported [5,6]. However, some difficulties in assembling the acetabular component intra-operatively have been reported in a small number of cases [7,8]. Ceramic bearings have a number of very appealing properties, however, they can be associated with the unusual phenomenon of squeaking. The incidence of squeaking has been reported as ranging from b1 to 21% depending on how the sound is defined [9]. Squeaking

The Conflict of Interest statement associated with this article can be found at http://dx. doi.org/10.1016/j.arth.2014.09.010. Reprint requests: Stephen M. Tai MBBS, BSc(Hons), FRCS (Tr & Orth), Specialist Orthopaedic Group, Mater Clinic Suite 1.08, 3-9 Gillies Street, North Sydney, New South Wales 2060, Australia. http://dx.doi.org/10.1016/j.arth.2014.09.010 0883-5403/© 2014 Elsevier Inc. All rights reserved.

has been reported as affecting the quality of life after THA, occasionally requiring revision surgery [10–12]. The DeltaMotion (developed by Finsbury Orthopaedics, Leatherhead, UK, now manufactured by DePuy, Leeds, UK) is a large diameter acetabular cup consisting of a titanium alloy shell with a pre-assembled fourth generation Ceram Tec BIOLOX delta ceramic liner. The thin ceramic liner of this component permits the use of a large femoral head, even in relatively small diameter acetabulae, thus optimizing the head–neck ratio. Potential advantages of large femoral heads over smaller diameter components include reduced risk of dislocation and impingement after THA [13]. However, unlike thin modular liners, the Delta motion does not permit the use of supplementary screws to achieve primary stability and this may be considered a potential drawback of the pre-assembled design. The aim of the study was to report the short-term clinical and radiological results of the DELTAMOTION cup, together with the incidence of post-operative squeaking. Patient and Methods We examined the results of 206 consecutive primary cementless THAs which were performed in 195 patients, using the DELTAMOTION ceramic bearing. Patient demographics are summarized in Table 1. The commonest indication for surgery was osteoarthritis (98.1%), followed by inflammatory arthropathy (1.5%) and acute fracture (0.5%). The data from all operations, clinical and radiological examinations were prospectively collected and stored in a database. Consent was obtained from all patients for the use of anonymous information for ongoing research projects.

S.M. Tai et al. / The Journal of Arthroplasty 30 (2015) 282–285 Table 1 Summary of Cohort Demographics. Hips Patients Male Female Mean age at surgery (years) (range) Mean weight (kg) (range) Mean height (cm) (range)

206 195 77 118 69 (38.1–93) 77 (46–136) 168 (152–198)

Operative Information All the procedures took place in a single institution. The joint arthroplasty surgery was performed within a high air-flow environment, utilizing a posterior approach to the hip joint, by one of two experienced surgeons (WLW, WKW). All components were implanted utilizing a press-fit technique. The desired position of the component was 45° of abduction and 20° of anteversion. The size of femoral head used in the DELTAMOTION is dictated by the diameter of the acetabular component: a 32 mm head is used with 42 and 44 mm cups, a 36 mm head is used with 46 and 48 mm cups, a 40 mm head is used with 50 and 52 mm cups, a 44 mm head is used with 54 and 56 mm cups, and a 48 mm head is used with cups 56 mm and larger. All patients had a Securfit (Stryker Orthopaedics, Mahwah, New Jersey) cementless femoral component inserted. This stem is manufactured from a titanium alloy (Ti–6Al–4 V) with a proximal porous hydroxyapatite coating. A 12/14 titanium alloy (Ti–6Al–4 V) taper sleeve adapter was inserted onto the 12/14 trunnion of the femoral stem with the ceramic head impacted onto the taper sleeve. Prior to implantation, the company manufacturing the femoral heads agreed that all engineering tolerances and geometries of the head–neck taper interface were suitable for use together with the chosen stem and sleeve adaptor. The head-liner clearance and surface finish of hard-on-hard bearings are important considerations relating to surface wear and the impact on frictional forces, consequently, the senior authors were assured by the manufacturing company engineers that the surface finish and clearance between the acetabular component and femoral head were compatible. Postoperatively, patients had a standardized protocol, that included both mechanical and chemical thromboprophylactic measures, 48 hours of intravenous antibiotics, and mobilization fully weight bearing as tolerated under the supervision of physiotherapists. Clinical Assessment Clinical information was prospectively collected pre-operatively and post-operatively at out-patient follow-up (6 weeks, 6 months and 2 years). Assessment included an examination of range of movement together with a Harris hip score (HHS) [14]—a valid and reliable test for determining the outcome of total hip arthroplasty [15]. Each patient was asked a binary question to determine if any audible squeaking had occurred since the time of operation and if so, whether this noise was reproducible. Clunks, clicks or any other noises were not considered as “true squeakers”, but the prevalence of these other noises was recorded. Known complications specifically relating to the prostheses (periprosthetic fracture and dislocation) were recorded in the database regardless of time after surgery and whether or not the complications were treated at our institution. Pulmonary embolism was detected by CT pulmonary angiography on the basis of clinical symptoms. Radiological Assessment Radiological assessment of the hip prostheses was performed utilizing anteroposterior (AP) pelvic and lateral radiographs using a standardized protocol. The AP film was obtained with a tube-to-film distance of 1000 mm with the tube orientated parallel to the floor. The resultant magnification of the radiograph created was 1.1. All pelvic

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radiographs were taken with the beam centered at the pubis symphysis with the patient standing. A low dose GE Definium machine was used to take all radiographs in this study. The images were scored by arthroplasty fellows, none of whom had been involved in the initial surgery or subsequent clinical follow-up. The radiological assessment of the acetabular component included evaluation for the presence or absence of radiolucent lines and osteolysis [16] according to the three zones described by DeLee and Charnley [17]. Components that exhibited no radiolucent lines or migration were considered well-fixed [18]. Cup inclination and anteversion were measured on the AP radiographs using the Ein-Bild-Roentgen-Analyse (EBRA) software [19]. EBRA is a validated method of determining cup orientation [20]. Component inclination and anteversion were measured blinded to the clinical outcome score or complication incidence. Femoral components were examined for evidence of subsidence by comparing serial radiographs. Using previously described techniques, pre and post-operative radiographs of squeaking hips were analyzed in order to assess the restoration of leg length [21], offset [22] and center of rotation [23], as these factors have been reported as influencing the incidence of squeaking [24]. The results were then compared with those for non-squeaking patients who were closely matched for gender, BMI (±2u), femoral head size, and cup inclination (±3°). Statistical Analysis The results of the analyses were compared using the paired and unpaired two-tailed t-tests. Statistical analysis of the presence or absence of squeaking was done with chi-squared and Fisher's exact tests. Correlation between squeaking and cup inclination and anteversion was determined with Pearson's coefficient. Statistical significance was set at P b 0.05. Results There were 189 hips in 178 patients available for clinical review, with a mean follow up of 28 months (15–41). Nine patients (5.1%) were lost to follow up and eight patients died (4.5%) from causes unrelated to the original surgery. EBRA analysis was performed on digital radiographs of 202 hips (98.1%). Harris Hip Score The mean HHS improved from a pre-operative score of 54 (16–95) to 92 (44–100) points post-operatively, with results rated as excellent in 175 hips (92.3%), fair in 5 hips (2.6%), and poor in 9 hips (4.7%). Squeaking Hips Fifteen hips (7.3%) (10 female:5 male) were recorded as squeaking. All occurrences of squeaking occurred during deep flexion of the hip. Mean post-operative time to onset of squeaking was 1.4 years (0.4–3). No significant difference was observed in age (P = 0.187), gender (P = 0.785), weight (P = 0.195), height (P = 0.351), BMI (P = 0.919), flexion/extension (P = 0.695), adduction (P = 0.465), abduction (P = 0.987), internal rotation (P = 0.137) or external rotation (P = 0.629) between squeaking and non-squeaking hips. The median femoral component size for squeaking hips was 44 mm. The median femoral component size for non-squeaking hips was 40 mm. The frequency of squeaking according to component size is reported in Table 2. Patients with a head size of 48 mm had the highest incidence of squeaking (11.1%). However, there was no statistically significant difference in the incidence of squeaking in the various head sizes (P = 0.531). In the squeaking hips, the mean acetabular component inclination and anteversion were 45.1° and 15.6° respectively. In the nonsqueaking hips, the mean acetabular component inclination and anteversion were 45.5° and 16.2° respectively. There was no statistical

S.M. Tai et al. / The Journal of Arthroplasty 30 (2015) 282–285

length to increase tissue tension. None of the revised cases were noted to squeak at subsequent follow-up.

Table 2 Frequency of Squeaking According to Component Size. Head Size (mm)

Non-Squeaking (n)

Squeaking (n)

36 40 44 48

16 82 61 32

0 7 4 4

Acetabular Size (mm)

Non-Squeaking (n)

Squeaking (n)

46 48 50 52 54 56 58 60 62 64

8 8 44 45 34 31 30 4 1 1

0 0 3 4 3 1 2 1 1 0

Discussion

difference in cup inclination (P = 0.808) and anteversion (P = 0.778) between squeaking and non-squeaking hips. There was no correlation between increasing cup inclination (P = 0.82) or anteversion (P = 0.69) and the occurrence of squeaking. Of the 155 cups measured within Lewinnek's safe zone [25], 8 hips squeaked (5.2%). Of the 51 cups positioned outside of the safe zone, 7 hips squeaked (13.7%). This difference was not statistically significant (P = 0.0834). We found no significant difference between squeaking and non-squeaking hips with regards to restoration of leg length (P = 0.327), offset (P = 0.684) or center of rotation (P = 0.644). Five patients (3 female; 2 male) reported other noises including clicking and popping. None of these 5 patients were troubled by their symptoms. Radiographic Analysis All patients showed bony ingrowth of the acetabular component. 98.5% of stems had good bony ingrowth, with the remaining 1.5% demonstrating stable fibrous growth. No cup or stem migration was reported. Two patients showed minor stem lucency: the first in zone 4, while the second patient had lucency in zones 4 and 5. Complications One pulmonary embolism (0.5%), 1 dislocation (0.5%), 2 periprosthetic fractures (1%) and 2 subsided stems (1%) were recorded, represented in Table 3. The peri-prosthetic fractures and the dislocation were all associated with trauma and required subsequent revision arthroplasty: The peri-prosthetic fractures comprised a peri-acetabular fracture that resulted in a loose cup and a peri-prosthetic femoral fracture that resulted in a loose stem. At the time of revision surgery for the femoral peri-prosthetic fracture the acetabular component was considered to be well fixed and so was retained. The case of dislocation related to recurrent falls resulting from alcohol-related cerebellar ataxia. CT scan demonstrated satisfactory acetabular component positioning. Reoperation was performed to reconstruct the posterior soft tissues using a vastus lateralis aponeurosis flap augmentation technique previously described [26]. At the time of surgery the acetabular and femoral components were confirmed to be well orientated and well fixed, so only the femoral head was removed and changed to a longer neck

Squeaking is a multifactorial complication that has been extensively reported with CoC articulations [27–30]. Retrieval studies show that patient, surgical and implant design may all contribute to squeaking [9,27,31]. We have previously reported on a cohort of 2406 patients with alumina-on-alumina bearings which showed that taller, heavier and younger patients were significantly more likely to have hips that squeaked [24]. Furthermore, we found squeaking hips had a significantly higher range of post-operative internal and external rotation compared with silent hips. In this current study, however, where acetabular component, femoral component and bearing type were all standardized, we found no significant difference between silent and squeaking patients in relation to height, weight, BMI or range of movement. Furthermore, we found no difference between squeaking and non-squeaking hips with regards to restoration of leg length, offset or center of rotation. The disparity we have between the findings in our own studies would seem to be consistent across the published literature as there is a lack of unanimity regarding which patient factors are associated with squeaking [24,32,33]. Perhaps this can be explained by the heterogeneity in components implanted in the various studies, as the alloy used to manufacture the Securfit stem (Ti-6Al-4 V) has been shown to have a significantly lower incidence of squeaking when compared with titanium alloys that contain molybdenum [31]. Acetabular component orientation has been suggested as an important factor in the origin of squeaking, as in certain cup positions the prosthesis is more likely to impinge and edge-load [34]. Our results would point towards posterior edge loading being an important surgical factor in the etiology of squeaking as squeaking only occurred in deep flexion, the position at which posterior edge loading occurs [27]. However, our study showed no correlation between increasing cup inclination or anteversion and the occurrence of squeaking. While a greater proportion of cups orientated outside of Lewinnek's safe zone (Fig. 1) squeaked (13.7% compared with 5.2%), this difference was not significant. Under ideal conditions, hard-on-hard bearings are assumed to be operating under conditions of fluid film lubrication with very low friction [24,31]. However, if the thin fluid lubrication is destroyed the frictional forces across the bearing interface are increased. The increase in friction due to increased surface contact area can provide more energy 65 60 55 50

Inclination

284

45

squeakers

40 35 30 25

Table 3 Frequency of Known Complications.

20 Pulmonary embolism Dislocation Peri-prosthetic fracture Subsided stem Squeaking

1 1 2 2 15

0

10

20

30

40

Anteversion Fig. 1. Acetabular cup position for squeaking and non-squeaking hips in relation to the Lewinnek's safe zone.

S.M. Tai et al. / The Journal of Arthroplasty 30 (2015) 282–285

than can dissipate resulting in the phenomenon of squeaking [29,32]. Our study does not show a significant relation between head size and squeaking, however the high squeaking incidence in patients with a 48 mm femoral head in comparison to those with the 36 mm femoral head reinforces the thought that head size may have a role to play in squeaking. Another theory why larger head sizes may be heard to squeak more often is the fact that the greater mass of a larger head may decrease the frequency of the resonating waves, bringing them into the audible range for humans. Our study reports a squeaking rate of 7.3%. This compares with a squeaking incidence of 20.7% in a recent similar study in which the DELTAMOTION acetabular component was also utilized [35]. Both studies have a patient cohort of approximately 200, with follow-up for a similar time period. Perhaps the greater incidence of squeaking reported by McDonnell et al could be attributed to the fact that several different designs of cementless femoral stems were used. Femoral component design, metallurgy and rigidity have all been suggested as reasons to explain differences in the incidence of squeaking when using the same bearing material [30]. This study has a number of limitations. While a standardized protocol was utilized for performing the radiographs, the technique remains open to human variation and the hence the measurement of cup anteversion using the EBRA software could be affected. Furthermore, we did not measure femoral component version, which is a factor that could potentially affect impingement in deep flexion. Radiological examinations were performed by different observers using predetermined criteria however, intra-observer variability tests were not performed. The number of hips within the sub-group case-matched analysis is small. Our national joint registry does not record individual occurrences of complications, and therefore determination of complication rates was reliant upon local audit and accurate feedback from other institutions. In summary, large head ceramic bearings are a relatively new design of hip bearing which possess a number of potentially advantageous characteristics. Similar to small diameter ceramic bearings however, they are associated with “benign” squeaking indicating that the squeaks are intermittent, pain free and not an indication for further surgery. The etiology of squeaking is still under debate, but likely to be multifactorial. While our early results of surgery using large head ceramic bearings are encouraging, further mid and long-term follow-up is required. Acknowledgments We would like to thank Lyn McDonald and Sharon Wales for all their help and support with this study. Stephen Tai would like to thank the John Charnley Trust. References 1. Revell PA, al-Saffar N, Kobayashi A. Biological reaction to debris in relation to joint prostheses. Proc Inst Mech Eng H 1997;211(2):187. 2. National Joint Regsiotry for England and Wales: 10th Annual report. http://njrcentre. org.uk; 2013. 3. Medical Device Alert Ref: MDA/2012/008. 4. Lombardi Jr AV, Berend KR, Seng BE, et al. Delta ceramic-on-alumina ceramic articulation in primary THA: prospective, randomized FDA-IDE study and retrieval analysis. Clin Orthop Relat Res 2010;468(2):367.

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Squeaking in large diameter ceramic-on-ceramic bearings in total hip arthroplasty.

We analyzed the results of 206 consecutive total hip arthroplasties performed using large diameter ceramic-on-ceramic bearings. At an average follow-u...
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