Objectives. Studies reporting specifically on squeaking in total hip arthroplasty have focused on cementless, and not on hybrid, fixation. We hypothesised that the cement mantle of the femur might have a damping effect on the sound transmitted through the metal stem. The objective of this study was to test the effect of cement on sound propagation along different stem designs and under different fixation conditions. Methods. An in vitro model for sound detection, composed of a mechanical suspension structure and a sound-registering electronic assembly, was designed. A pulse of sound in the audible range was propagated along bare stems and stems implanted in cadaveric bone femurs with and without cement. Two stems of different alloy and geometry were compared. Results. The magnitudes of the maximum amplitudes of the bare stem were in the range of 10.8 V to 11.8 V, whereas the amplitudes for the same stems with a cement mantle in a cadaveric bone decreased to 0.3 V to 0.7 V, implying a pulse-attenuation efficiency of greater than 97%. The same magnitude is close to 40% when the comparison is made against stems implanted in cadaveric bone femurs without cement. Conclusion. The in vitro model presented here has shown that the cement had a remarkable effect on sound attenuation and a strong energy absorption in cement mantle and bone. The visco-elastic properties of cement can contribute to the dissipation of vibro-acoustic energy, thus preventing hip prostheses from squeaking. This could explain, at least in part, the lack of reports of squeaking when hybrid fixation is used. Cite this article: F. J. Burgo, D. E. Mengelle, A. Ozols, C. Fernandez, C. M. Autorino. The damping effect of cement as a potential mitigation factor of squeaking in ceramic-on-ceramic total hip arthroplasty. Bone Joint Res 2016;5:531–537. DOI: 10.1302/2046-3758.511.BJR-2016-0058.R1

Introduction and Objective. Ceramic on Ceramic bearings in Total Hip Arthroplasty (THA) afford a low friction coefficient, low wear rates and extreme hardness. Significant complications include hip squeak, ceramic fracture and poor polyethylene performance in revision procedures due to imbedding of abrasive microscopic ceramic fragments. We report on the results of this bearing at a minimum of 10 years. Materials and Methods. A single-centre retrospective review of 449 THAs was performed. Primary outcome measures included aseptic revision and all-cause revision rates at a minimum of 10 years post operatively. Evaluation of functionality was performed with WOMAC and SF-36 scores which were performed pre-operatively and at intervals of 6 months, one year, 2 years, 5 years and 10 years post operatively. Results. There was a 6.2% (n=28) all-cause and 5.3% (n=24) aseptic revision rate for ceramic on ceramic total hip arthroplasty at minimum of 10 years with a mean time to revision 4.8 years (range 2 months − 11.6 years). Notably, there were 2 revisions for ceramic head fracture, one for ceramic liner fracture, 3 for aseptic loosening and 3 revisions for squeaking. Pain of unknown origin was the most common reason for revision. There was an improvement in postoperative WOMAC scores from a mean of 59.8 (range 15–95) pre-operatively to a mean of 15.6 (range 0–78) at 10 years. Conclusions. This study showed good functional outcomes but high revision rates for CoC THA at a minimum of 10 years. The role for CoC bearings in THA has been called into question in recent years and may continue to decline in popularity, even in younger patients. Further large scale studies are important to assess the long-term outcomes of this bearing surface

Explanations for “bearing” noise in ceramic-on-ceramic hips (COC) included stripe-wear formation and loss of lubrication leading to higher friction. However clinical and retrieval studies have clearly documented stripe wear in patients that did not have squeaking. Seldom highlighted has been the risk of metal-on-metal or metal-on-ceramic impingement present in total hip arthroplasty (THA) with metal and ceramic cup designs. The limitation in THA positioning studies has been (i) reliance on 2-dimensional radiographic images and (ii) patients lying supine on the examination table, thus not imaged in squeaking positions. We collected eleven squeaking COC cases for an EOS 3D-imaging functional study. Hip positions were documented in each patient's functional ‘squeaking’ posture using standard and 3-D EOS images for sitting, rising from a chair, hip extension in striding, and single-legged stance. EOS imaging documented for the 1st time that postural dysfunctions with potential impingements were demonstrable for each squeaking case. The 1st major insight in this study came from a female patient who complained of squeaking while walking in flat-soled shoes (Figs. 1a, b). She found that when wearing high-heeled shoes her hip stopped squeaking (Figs. 1c, d). Her lateral EOS view in standing position with heeled shoes revealed that the femoral stem had approximately 3o less hyper-extension compared to flat shoes (Figs. 1b, d, arrows #1,3). The three-dimensional ‘sky-view’ EOS reconstruction of pelvis and femurs (Fig. 2) showed that her femur was also more internally rotated when she wore heels. These subtle shifts in position changed her COC hip from one of squeaking to non-squeaking. A squeaking male patient observed similar postural effects while walking up his boat ramp but not going down the ramp. In both cases, the squeaking was a consequence of cup impinging on a metal femoral neck. Thus the primary cause of squeaking appeared to be hip impingement, i.e. repetitive subluxations that patients generally were not aware of. Another case is representative of situations due to atypical and subtle cup/stem mal-adjustments (Fig. 3); frontal pelvic-tilt, thoracolumbar scoliosis, with 1cm of femur lengthening and a significant increase of offset are observed. Also evident was the femoral-neck retroversion in both standing and sitting. Squeaking occurred when modification of the functional neck orientation occured in one-legged stance (Fig. 3c) or when climbing a stair (Fig. 3d). It was apparent in our EOS studies that patient functionality controlled whether squeaking occurred or not. Thus the new data indicated COC squeaking was a three-fold consequence of component positioning, spine and pelvic adaptions, and variations in patient posture. One limitation here is that our conclusions are based on a small sample of patients and may not be applicable to all. A consequence of such repetitive impingement can be cup rim damage and neck-notching, with release of metal debris. It is well documented that retrieved ceramic bearings are frequently stained black. Thus hip squeaking may likely result from (i) impingement and secondarily (ii) due to ingress of metal particles, and then (iii) producing a failure of lubrication. To view tables/figures, please contact authors directly

Introduction. Acetabular cup orientation has been shown to be a factor in edge-loading of a ceramic-on-ceramic THR bearing. Currently all recommended guidelines for cup orientation are defined from static measurements with the patient positioned supine. The objectives of this study are to investigate functional cup orientation and the incidence of edge-loading in ceramic hips using commercially available, dynamic musculoskeletal modelling software that simulates each patient performing activities associated with edge-loading. Methodology. Eighteen patients with reproducible squeaking in their ceramic-on-ceramic total hip arthroplasties were recruited from a previous study investigating the incidence of noise in large-diameter ceramic bearings. All 18 patients had a Delta Motion acetabular component, with head sizes ranging from 40 – 48mm. All had a reproducible squeak during a deep flexion activity. A control group of thirty-six patients with Delta Motion bearings who had never experienced a squeak were recruited from the silent cohort of the same original study. They were matched to the squeaking group for implant type, acetabular cup orientation, ligament laxity, maximum hip flexion and BMI. All 54 patients were modelled performing two functional activities using the Optimized Ortho Postoperative Kinematics Simulation software. The software uses standard medical imaging to produce a patient-specific rigid body dynamics analysis of the subject performing a sit-to-stand task and a step-up with the contralateral leg, Fig 1. The software calculates the dynamic force at the replaced hip throughout the two activities and plots the bearing contact patch, using a Hertzian contact algorithm, as it traces across the articulating surface, Fig 2. As all the squeaking hips did so during deep flexion, the minimum posterior Contact Patch to Rim Distance (CPRD) can then be determined by calculating the smallest distance between the edge of the contact patch and the true rim of the ceramic liner, Fig 2. A negative posterior CPRD indicates posterior edge-loading. Results. The mean CPRD was significantly less in the squeaking group than the control group, −2.5mm and 2.9mm respectively, (p < 0.001), Fig 3. The mean pelvic tilt in the flexed seated position was 12.6° (range −13.5° to 30.3°) for the squeaking group and 5.1° (−9.8° to 26.4°) for the control group. Consequently, the mean functional cup anteversion at seat-off was significantly less in the squeaking group than the control group, 8.1° (−10.5° to 36.0°) and 21.1° (−1.9° to 38.4°) respectively (p < 0.001), Fig 3. There were 67% (12) of patients in the squeaking group that showed posterior edge-loading in the simulation compared to only 28% (10) in the control group that exhibited posterior edge-loading in the simulation. Conclusions. Acetabular cup orientation during activities associated with edge-loading are likely very different from those measured when supine. Patients with large anterior pelvic tilts during deep flexion activities might be more susceptible to posterior edge-loading and squeaking in ceramic-on-ceramic bearings, as a consequence of a significant decrease in cup anteversion. If these patients can be identified preoperatively, cup orientation and bearing choice could be customised accordingly to accommodate these individual motion patterns

The April 2014 Hip & Pelvis Roundup. 360 . looks at: Recent arthroplasty and flight; whether that squeak could be a fracture; diagnosing early infected hip replacement; impaction grafting at a decade; whether squeaking is more common than previously thought; femoral offset associated with post THR outcomes; and periprosthetic fracture stabilisation

Introduction. Squeaking is a potential problem of all hard on hard bearings yet it has been less frequently reported in metal-on-metal hips. We compared a cohort of 11 squeaking metal-on-metal hip resurfacings to individually matched controls, assessing cup inclination and anteversion between the groups to look for any differences. Methods. We retrospectively reviewed the patient records of 332 patients (387 hip resurfacings) who underwent hip resurfacing between December 1999 and Dec 2012. 11 hips in 11 patients were reported to squeak postoperatively. Each of these patients, except one, were matched by age, sex, BMI and implant to 3 controls. The final patient only had one control due to his high BMI. The latest post-operative radiographs of the squeaking group and controls were analysed using EBRA (Einzel-Bild-Roentgen-Analysis, University of Innsbruck, Austria) software to evaluate cup inclination and anteversion. Results. Post- operative audible squeaking occurred in 11 out of 387 hips (2.84%). The mean follow up of the squeaking group was 88.6 months (19–131 months). The mean time to squeak was 11.3 months (3–22 months). 8 (73%) patients were male, 10 (91%) patients had a Birmingham hip resurfacing and 9 (82%) patients had an operation on the left hip. The mean inclination angle of the cups in the squeaking group was 48.4° (43.9°–55.4°) compared to 50° (37.8° −63°) in the control group. The mean anteversion of the cups in the squeaking group was 17.1°(6.3°–25.7°) compared to 14.6° (4.3° −33.5°) in the control group. There was no statistically significant difference between the cases and their controls for cup inclination (p = 0.36) or cup anteversion (p = 0.31). The mean head size in the squeaking group was smaller at 49.3 mm (46 mm-54 mm), compared to 51.4 mm (48 mm-54 mm) in the control group (p = 0.026). The mean cup size in the squeaking group was also smaller at 56.5 mm (54 mm-62 mm), compared to 57.9 mm (48 mm-60 mm) in the control group (p = 0.007). Overall, 4 (40%) male patients in the squeaking group had a head size less than 50 mm, compared to 0 (0%) in the control group. 3 (27%) patients with squeaking resurfacings underwent revision surgery. 1 (9%) at 72 month for a pseudotumour, 1 (9%) at 114 months for persistant squeaking and 1 (9%) at 117 months for a subtrochanteric fracture after a fall. Conclusions. No difference was found between the radiographic inclination or anteversion of squeaking metal-on-metal hip resurfacing cups compared to a control group. Male patients with squeaking hips were noted to have smaller head and cup sizes than their controls

INTRODUCTION. Squeaking after total hip replacement has been reported in up to 10% of patients. Some authors proposed that sound emissions from squeaking hips result from resonance of one or other or both of the metal parts and not the bearing surfaces. There is no reported in vitro study about the squeaking frequencies under lubricated regime. The goal of the study was to reproduce the squeaking in vitro under lubricated conditions, and to compare the in vitro frequencies to in vivo frequencies determined in a group of squeaking patients. The frequencies may help determining the responsible part of the noise. METHODS. Four patients, who underwent THR with a Ceramic-on-Ceramic THR (Trident(r), Stryker(r)) presented a squeaking noise. The noise was recorded and analysed with acoustic software (FMaster(r)). In-vitro 3 alumina ceramic (Biolox Forte Ceramtec(r)) 32 mm diameter (Ceramconcept(r)) components were tested using a PROSIM(r) hip friction simulator. The cup was positioned with a 75° abduction angle in order to achieve edge loading conditions. The backing and the cup liner were cut with a diamond saw, in order to avoid neck-head impingement and dislocation in case of high cup abduction angles (Figure1). The head was articulated ± 10° at 1 Hz with a load of 2.5kN for a duration of 300 cycles. The motion was along the edge. Tests were conducted under lubricated conditions with 25% bovine serum without and with the addition of a 3. rd. body alumina ceramic particle (200 μm thickness and 2 mm length). Before hand, engineering blue was used in order to analyze the contact area and to determine whether edge loading was achieved. RESULTS. Edge loading was obtained. In-vitro, no squeaking occurred under edge loading conditions. However, with the addition of an alumina ceramic 3. rd. body particle in the contact region squeaking was obtained at the beginning of the tests and stopped after ∼20 seconds (dominant frequency 2.6 kHz). In-vivo, recordings had a dominant frequency ranging between 2.2 and 2.4 kHz. DISCUSSION. For the first time, squeaking was reproduced in vitro under lubricated conditions. In-vitro noises followed edge loading and 3. rd. body particles and despite, the severe conditions, squeaking was intermittent and difficult to reproduce. However, squeaking is probably more difficult to reproduce because the cup was cut and the head was fixed in the simulator, preventing vibration to occur. Squeaking noises of a similar frequency were recorded in-vitro and in-vivo. The lower frequency of squeaking recorded in-vivo, demonstrates a potential damping effect of the soft tissues. Therefore, the squeaking in the patients was probably related to the bearing surfaces and modified lubrication conditions that may be due to edge loading. Varnum et al reported recently (3) that all the revised squeaking patients had a neck-cup impingement with metal 3. rd. body particles. These metallic wear particles may generate squeaking as shown in vitro. However, a larger cohort of squeaking patients is needed to confirm these results

The problem associated with ceramic on ceramic total hip replacement (THR) is audible noise. Squeaking is the most frequently documented sound. The incidence of squeaking has been reported to wide range from 0.7 to 20.9%. Nevertheless there is no study to investigate on incidence of noise in computer assisted THR with ceramic on ceramic bearing. The purpose of this study was to determine the incidence and risks factors associated with noise. We retrospectively reviewed 200 patients (202 hips) whom performed computer assisted THR (Orthopilot, B. Braun, Tuttlingen, Germany) with ceramic on ceramic bearing between March 2009 and August 2012. All procedures underwent uncemented THR with posterior approach by single surgeon. All hips implanted with PLASMACUP and EXIA femoral stem (B. Braun, Tuttlingen, Germany). All cases used BIOLOX DELTA (Ceramtec, AG, Plochingen, Germany) ceramic liner and head. The incidence and type of noise were interviewed by telephone using set of questionnaire. Patient's age, weight, height, body mass index, acetabular cup size, femoral offset size determined from medical record for comparing between silent hips and noisy hips. The acetabular inclination angle, acetabular anteversion angle, femoral offset, hip offset were reviewed to compare difference between silent hips and noisy hips. The audible noise was reported for 13 hips (6.44%). 5 patients (5 hips) reported click (2.47%) and 8 patients (8 hips) squeaked (3.97%). The mean time to first occurrence of click was 13.4 months and squeak was 7.4 months after surgery. Most common frequency of click was less than weekly (60%) and squeak was 1–4 times per week (50%). Most common activity associated with noise was bending; 40% in click and 75% in squeaking. No patients complained for pain or social problem. Moreover, no patient underwent any intervention for the noise. The noise had not self-resolved in any of the patients at last follow up. Age, weight, height and BMI showed no statistically significant difference between silent hips and click hips. In addition, there was also same result between silent hips and squeaking hips. Acetabular cup insert size and femoral offset stem size the results showed that there was no statistically significant difference between silent hips and click hips, also with squeaking hips. Acetabular inclination, angle acetabular anteversion angle, femoral offset, hip offset the results shown that only acetabular anteversion angle differed significantly between silent hips (19.94±7.78 degree) and squeaking hips (13.46±5.54 degree). The results can conclude that incidence of noise after ceramic on ceramic THR with navigation was 6.44 %. Squeaking incidence was 3.97% and click incidence was 2.47%. The only associated squeaking risk factor was cup anteversion angle. In this study, squeaking hip had cup anteversion angle significant less than silent hip

The use of hard-on-hard bearings, including ceramics peaked in the mid 2000's and has seen rapid decline since that time. Ceramics are not new to the market place but have had a 40 year history outside the U.S. The basis for renewed enthusiasm for ceramics included improved manufacturing, improved taper tolerances, higher strength, and lower wear. In spite of the major improvements concerns have been expressed with new generation ceramics by the experts and thought leaders in the field. The major concerns included complications related to modularity, continued problems with fracture and consequences of fracture, limited surgical options, and squeaking and impingement. The conclusion of one review article was that “although ceramics show promise as a lower wear articulation, manufacturing and design modifications and improvements will continue in an attempt to address the substantial concerns that persist”. Modifications have indeed occurred. The question is rather all of these concerns have been addressed and the answer is no. One proposed solution was a hybrid material of Alumina and Zirconia (Delta Ceramic). The advantages included higher strength, lower wear, more options and possibly less squeaking. Unfortunately the modest material improvements did not begin to overcome the obstacles to adopting this technology. High on this list is the problem with cost with the current health care environment unwilling to pay for expensive new technology that does not have proven value. A 2nd major issue is new technology must account for variability in surgeon performance in maximising margin for error. The medical legal environment is unforgiving of failure of new unproven options. Most of the old issues with ceramics have not been completely resolved. Delta Ceramic in particular, has increased cost with no demonstrated benefit. A major problem is there is no known problem with metal or ceramic against cross-linked polyethylene bearing in terms of wear or osteolysis in the 10–15 year time frame. Among all the bearing articulations, metal-on-cross-linked performs the best. The persistent vexing problems with ceramics include impingement, liner breakage, and squeaking. Ceramic components do not tolerate component malposition which increases wear and squeaking. The problem is that a substantial percentage of hip replacements are put in outside of the ideal radiographic zone even at specialty centers. Breakage continues to be a problem especially with liners. There is also a need for complete rim exposure for concentric placement with impaction of liners which makes ceramics less compatible with small incision surgery. The problem of squeaking has not been solved by Delta Ceramic. Originally a case report appeared in the literature of squeaking with Delta Ceramic. Since that time a large scale study has showed that only 69% of Delta Ceramic hips were silent with up to 13% being associated with reproducible squeaking. While a new generation of ceramics are better than the earlier generation and have lowered the fracture risk and increased intraoperative options, the current generation ceramics still provide far fewer options than a standard metal-on-cross-linked total hip. The current generation metal-on-cross-linked total hips have 10–15 year results that cannot be improved upon in terms of wear and osteolysis. Other unsolved problems include breaking, chipping and squeaking. Ceramic-on-ceramic is less tolerant of suboptimal position which leads to impingement, edge loading, and an increased incidence of squeaking. Until all of these problems are successfully addressed, ceramic-on-ceramic cannot be advocated for widespread use

At the present time, there is no bearing in total hip arthroplasty that a surgeon can present to a younger and/or more active patient as being the bearing that will necessarily last them a lifetime. This is the driver to offering alternative bearings (crosslinked polyethylene with either a CoCr or ceramic head, resurfacings, and ceramic-on-ceramic) to patients. Each of these bearings has pros and cons, and none has emerged as the clear victor in the ongoing debate. Ceramic-on-ceramic (CoC) bearings have been available for decades. Earlier generation CoC bearings did encounter problems with rare fractures, however, with a greater understanding and improvement in the material, the fracture incidence has been significantly reduced. However, what has emerged in the past few years is an increasing reporting of significant squeaking. The incidence of squeaking, reported in the literature in various series, has varied from less than 1% to over 20%, depending on the definition used. The primary reasons that ceramic-on-ceramic is not truly the articulation of choice for younger patients are: 1) There is absolutely no evidence that this bearing has a lower revision rate. Data from the Australian joint registry actually shows that at 15 years it has a significantly increased rate of revision (7.2%) compared with using a highly crosslinked liner with either a ceramic (5.1%) or a CoCr (6.3%) head; 2) This bearing is by far the most costly bearing on the market. In 2017 with significant constraints on health care systems across the globe, this is a significant concern; 3) This bearing has unique complications including squeaking and both liner and head fracturing. While ceramic-on-ceramic can be considered a viable alternative bearing in total hip arthroplasty, it can be in no way considered the articulation of longevity for the younger patient

Introduction. One of the most common complications of ceramic on ceramic hip replacement is squeaking. The association of Accolade stem and Trident acetabular system has been reported to have squeaking incidence of up to 35,6%. There is doubt if this phenomenon occurs due to: the stem titanium alloy, the V40 femoral neck, the recessed liner of the trident cup or even the mal-seating of the trident insert on the cup. Objectives. Primary: The purpose of the present study was to determine the incidence of squeaking in association with the use of Exeter stem and Trident ceramic acetabular system. Secondary: Analysis of the correlation of the cup abduction angle and squeaking. Methods. During the period from March 2004 to December 2008, two surgeons performed 87 total hip arthroplasties in 77 patients with use of a ceramic-on-ceramic bearing (Exeter stem, alumina head, Trident ceramic acetabular system). Seventy six patients (86 THA) were available for review after at least 18 months follow-up. The incidence of squeaking and other noises was analyzed. Cup abduction angle was measured. The Pearson correlation coefficient was used to determine if a correlation existed between the cup abduction angle and squeaking. Results. The incidence of squeaking was 2,63% (2 patients). Both patients reported a “click” noise in hyperextension of the hip. The mean abduction angle was 44 degress (35–60), and 48 degrees (46 and 50) on the squeaking group. There was no statistically significant difference in the in the mean cup inclination between squeaky and quiet hips. Conclusion. The incidence of squeaking in association with the use of Exeter stem and Trident ceramic acetabular system was 2,63%. There was no correlation of the cup abduction angle and squeaking

Alumina ceramic-ceramic bearings have the benefit of very low wear and studies showing the complete absence of osteolysis during the first decade of close study. However, good results depend on several critical factors including surgical exposure, surgical technique, component placement, and choice of component design. The following abstract discusses our experience with several of these factors. Initially, there were concerns that the use of ceramic-ceramic bearings would lead to a higher incidence of hip dislocation since the bearings have fewer femoral head-length choices and the absence of lipped-liners. In our prospective study of 418 hips the incidence of hip dislocation at 1 to 10 year followup is 0.5% (2/418). This experience suggests that the use of alumina ceramic-ceramic bearings is not associated with an increased incidence of dislocation. More recently, concerns about squeaking of alumina ceramic-ceramic bearings have been reported, particularly from centers in the United States. To investigate this issue, we reviewed information on 1275 consecutive revision THAs and 1039 consecutive primary ceramic-ceramic THA that had been performed at two institutions between 1996 and 2007. To identify the influence of the implant design on the incidence of squeaking we divided the primary hips into three groups with group 1: flush mounted ceramic liner; group 2a: recessed ceramic liner mated with a stem made of TiAlV; and group 2b: recessed ceramic liner mated with a stem made of a beta titanium alloy comprised of 12% molybdenum, 6% Zirconium, and 2% Iron. Analysis of the 1275 revision hips revealed 5 alumina ceramic-ceramic hips in patients who complained of squeaking or grinding. All 5 hips were designs that included a ceramic liner that was recessed inside of an elevated metal rim. All 5 hips also demonstrated metallosis at the time of revision. In primary THA, Group 2b had statistically significantly more squeaking (9 of 118) than group 2a (10 of 321) which had statistically significantly more squeaking than group 1 (6 of 700). In addition, the severity of squeaking between the groups was qualitatively different. Patients in Group 2b who complained of squeaking would often experience squeaking frequently throughout the day and could be demonstrated in the physician’s office. By contrast, patients in Group 1 who noted squeaking stated that the hip squeaked once a day to once a year. No patient in Group 1 complained of frequent squeaking or could demonstrate squeaking in the physicians’ office. Further, joint fluid analysis from a patient in Group 2b who complained of squeaking revealed metal from both the femoral (Molybdenum) and acetabular (Aluminum) components. As reported in another abstract at this meeting, 10 year survivorship of flush-mounted alumina ceramic-ceramic THA is 98.4% (95% confidence interval 97.1–100%) and no patient in that prospective clinical studies demonstrated radiographic evidence of osteolysis or wear. These experiences demonstrate that THA using alumina ceramic-ceramic is extremely reliable with low revision and dislocation rates and an absence of osteolysis. Significant squeaking is not associated with flush-mounted alumina ceramic liners and is clearly associated with elevated metal rims and metallosis. Finally, squeaking is statistically significantly associated with femoral components made of a beta titanium alloy consisting of Titanium, Molybdenum, Aluminum, and Iron

Introduction: Squeaking after total hip replacement has been reported in up to 10% of patients. Some authors proposed that sound emissions from squeaking hips result from resonance of one or other or both of the metal parts and not the bearing surfaces. There is no reported in vitro study about the squeaking frequencies under lubricated regime. The goal of the study was to reproduce the squeaking in vitro under lubricated conditions, and to compare the in vitro frequencies to in vivo frequencies determined in a group of squeaking patients. The frequencies may help determining the responsible part of the noise. Methods: Four patients, who underwent THR with a Ceramic-on-Ceramic THR (Trident. ®. , Stryker. ®. ) presented a squeaking noise. The noise was recorded and analysed with acoustic software (FMaster. ®. ). In-vitro 3 alumina ceramic (Biolox Forte Ceramtec. ®. ) 32 mm diameter (Ceramconcept. ®. ) components were tested using a PROSIM. ®. hip friction simulator. The cup was positioned with a 75° abduction angle in order to achieve edge loading conditions. The backing and the cup liner were cut with a diamond saw, in order to avoid neck-head impingement and dislocation in case of high cup abduction angles. The head was articulated ± 10° at 1 Hz with a load of 2.5kN for a duration of 300 cycles. The motion was along the edge. Tests were conducted under lubricated conditions with 25% bovine serum without and with the addition of a 3rd body alumina ceramic particle (200 μm thickness and 2 mm length). Results: Edge loading was obtained incompletely. In-vitro, no squeaking occurred under edge loading conditions. However, with the addition of an alumina ceramic 3rd body particle in the contact region, squeaking was obtained at the beginning of the tests and stopped after ~20 seconds (dominant frequency 2.6 kHz). In-vivo, recordings had a dominant frequency ranging between 2.2 and 2.4 kHz. Discussion: For the first time, squeaking was reproduced in vitro under lubricated conditions. In-vitro noises followed edge loading and 3rd body particles and despite, the severe conditions, squeaking was intermittent and difficult to reproduce. However, squeaking is probably more difficult to reproduce because the cup was cut and the head was fixed in the simulator, preventing vibration to occur. Squeaking noises of a similar frequency were recorded in-vitro and in-vivo. The lower frequency of squeaking recorded in-vivo, demonstrates a potential damping effect of the soft tissues. Therefore, the squeaking in the patients was probably related to the bearing surfaces and modified lubrication conditions that may be due to edge loading. The determined values of frequencies may help to analyze the squeaking patients in order to determine the mechanism generating the sound

Ceramic-on-ceramic (CoC) total hip arthroplasty (THA) can produce articular noise during the normal activities, generating discomfort to the patient. THA noise has to be investigated also as a potential predictor and a clinical sign of prosthetic failure. An observational study has been carried out to characterize the noise in CoC cementless THA, and to analyze the related factors. A total of 46 patients with noisy hip have been enrolled in 38 months, within the follow-up protocol normally applied for the early diagnosis of ceramic liner fracture [1]. Noise recording was based on a high-quality audible recorder (mod. LS 3, Olympus, Japan) and a portable ultrasonic transducer (mod USB AE 1ch, PAC, USA). The sensors for noise recording were applied to the hip of the patient during a sequence of repeatable motorial activities (forward and backward walking, squat, sit in a chair, flexion and extension of the leg). Sessions were also video-recorded to associate the noise emission to the specific movements. Each noise event was initially identified by the operator and therefore classified by comparison to the spectral characteristics (duration, intensity and frequency) of the main noise types. Number and spectral characteristics of noise events were obtained and correlated to the factors describing the clinical status of the patient, the surgical approach, the prosthetic device implanted. The study investigated also the noise as a sign of implant failure, by comparison with the total number of implants failed in the cohort during the study. We observed three types of noise with the main spectral characteristics in agreement to the literature: clicking, squeaking and popping. Among the identified types of noise, squeaking showed the longest duration and the highest amplitude. The 63% of hip presented the emission of just one type of noise, while the remaining a mix of types. The movement with the highest presence of noise was walking, followed by squat. Correlation was found between the noise type and the dimension of the ceramic head (p<0.001), with the sizes of 32 mm more affected by squeaking that the smaller one. Squeaking appeared before during the follow-up than the other types of noise. The 35% (16/46) of the noisy hips were revised during the study. Among the revised hips, the 81% (13/16) were affected by impingement and/or severe damage of the prosthetic components. The antiversion of the cup (p=0.008), the presence of debris in the synovial fluid (p=0.021) and the average frequency of squeaking (p=0.006) were significant predictors for the revision, but it has to be mentioned that the squeaking data was obtained on a small subset of revised patients. Ultrasonic analysis did not show significant correlations. The study presented and validated an experimental procedure to analyze noisy hips in clinical trials. Noise is confirmed to be a significant parameter in the follow-up evaluation of ceramic THA

Background: Squeaking in hip arthroplasty is a phenomenon that was described decades ago, but has only been brought back to attention recently. It occurs predominantly in ceramic on ceramic bearings, and has a reported incidence from less than 1% to 21%. The cause and the implication of squeaking are still unknown and many factors have been suggested to contribute. This study has looked into the patient factors to investigate if any clinical features are associated with an increased risk of squeaking. Methods: All primary total hip arthroplasties with ceramic on ceramic bearing that were performed at our unit were reviewed and all squeaking hips presented are included in the study. Patient demographics and clinical outcome data were analysed and compared with matched controls from the silent hips. Results: Between 1997 and 2008, 3375 primary hip arthroplasties in 3182 patients with ceramic on ceramic bearing were performed in our unit. Seventy one hips (2.1%) presented with squeaking on direct questioning and self reporting. Those patients were found to be taller, heavier and younger. They also have a significantly higher post-operative range of hip motion and higher Harris hip score when compared to matched controls. There was no difference in the satisfaction score. Only 4 patients (5.6%) presented with pain as well as squeaking, and 2 (2.8%) resulted in revision surgery for problematic squeaking. Conclusions: We present the largest series of squeaking primary hip arthroplasties with ceramic on ceramic bearing to date. A number of patient factors were found to be associated with squeaking. The taller, heavier and younger patients with more flexible and functional hips were at a higher risk, presumably because these patients put greater mechanical demands on their hips. Majority of the patients with squeaking are pain free and there is only a small risk of requiring revision surgery

Polyimide (MP-1, MMATech, Haifa, Israel), is a high performance aerospace thermoplastic used for its lubricity, stability, inertness and radiation resistance. A wear resistant thin robust bearing is needed for total hip arthroplasty (THR). After independent laboratory testing, in 2006, the author used the material as a bearing in two Reflection (Smith and Nephew, USA) hip surgeries. The first, a revision for polyethylene wear, survives with no evidence of wear, noise, new osteolysis or complications related to the MP-1 bearing after 16 yrs. The second donated his asymptomatic MP-1 hip at 6.5yrs for post-mortem examination. There were no osteoclasts, cellular reaction bland in contrast to that of polyethylene. In 2013 a clinical study with ethical committee approval was started using a Biolox Delta (Ceramtec, Germany) head against a polyimide liner in 97 patients. MMATech sold all liners, irradiated: steam 52:45. Sixteen were re-machined in New Zealand. Acetabular shells were Delta PF (LIMA, Italy). The liner locked by taper. The cohort consisted of 46:51 M:F, and ages 43 to 85, mean 65. Ten received cemented stems. For contralateral surgery, a ceramic or polyethylene liner was used. Initial patients were lower demand, later, more active patients, mountain-biking and running. All patients have on-going follow up, including MP-1 liner revision cases. There has been no measurable wear, or osteolysis around the acetabular components using weight-bearing radiographs. Squeaking within the first 6 weeks was noted in 39 number of cases and subtle increase in palpable friction, (passive rotation at 50 degrees flexion), but then disappeared. There were 6 revisions, four of which were related to cementless Stemsys implants (Evolutis, Italy) fixed distally with proximal linear lucencies in Gruen zones 1 and 7, and 2 and 6. No shells were revised and MP-1 liners were routinely changed to ceramic or polyethylene. The liners showed no head contact at the apex, with highly polished contact areas. There were no deep or superficial infections, but one traumatic anterior dislocation at 7 years associated with 5 mm subsidence of a non-collared stem. The initial squeaking and increased friction was due to the engineering of the liner / shell composite as implanted, not allowing adequate clearance for fluid film lubrication and contributed to by shell distortion during impaction. The revised bearings were “equatorial” rather than polar, and with lack of wear or creep this never fully resolved. Where the clearance was better, function was normal. The “slow” utilization was due to my ongoing concern with clearances not being correct. The revision of 4 Stemsys stems, tribology issues may have contributed, but non “MP-1” / Stemsys combinations outside this study have shown the same response, thought to be due to de-bonding of the hydroxyapatite coating. With correct engineering and clearances, a 3.6 mm thick MP-1 bearing, a surface Ra<0.5, steam sterilized, shows no appreciable wear, and with confidence, can be used as a high performance THR bearing

Squeaking in ceramic on ceramic bearing total hip arthroplasty is well documented but its aetiology is poorly understood. In this study we have undertaken an acoustic analysis of the squeaking sound recorded from 31 ceramic on ceramic bearing hips. The frequencies of these sounds were compared with in vitro acoustic analysis of the component parts of the total hip implant. Analysis of the sounds produced by squeaking hip replacements and comparison of the frequencies of these sounds with the natural frequency of the component parts of the hip replacements indicates that the squeaking sound is due to a friction driven forced vibration resulting in resonance of one or both of the metal components of the implant. Finite element analysis of edge loading of the prostheses shows that there is a stiffness incompatibility between the acetabular shell and the liner. The shell tends to deform, uncoupling the shell-liner taper system. As a result the liner tends to tilt out of the acetabular shell and slide against the acetabular shell adjacent to the applied load. The amount of sliding varied from 4–40μm. In vitro acoustic and finite element analysis of the component parts of a total hip replacement compared with in vivo acoustic analysis of squeaking hips indicate that either the acetabular shell or the femoral stem can act as an “oscillator’ in a forced vibration system and thus emit a squeak. Introduction: Squeaking has long been recognized as a complication in hip arthroplasty. It was first reported in the Judet acrylic hemiarthroplasty. 1. It was the squeak of a Judet prosthesis that led John Charnley to investigate friction and lubrication of normal and artificial joints which ultimately led to the concept of low friction arthroplasty. Ceramic on ceramic bearings were pioneered by Boutin in France during the 1970’s, but experienced unacceptably high fracture rates. Charnley demonstrated in vitro squeaking when he tested one of Boutin’s ceramic-on-ceramic bearings in his pendulum friction comparator. 2. Squeaking has also been reported in other hard on hard bearings, and can also occur after polyethylene bearing surface failure resulting in articulation between metal on metal or ceramic on metal surfaces. 3–6. Recently, squeaking has been increasingly reported in modern ceramic-on-ceramic bearings in hip arthroplasty. However, although well-documented, the aetiology of squeaking in ceramic on ceramic bearings is still poorly understood. The incidence ranges from under 1% to 10%. 7–10. It has been reported in mismatched ceramic couples,11and after ceramic liner fracture. 12,13. An increased risk of squeaking has been demonstrated with acetabular component malposition, as well as in younger, heavier and taller patients. 9. However, it may also occur in properly matched ceramic bearings with ideal acetabular component position and in the absence of neck to rim impingement. 7–9. In rare cases, the squeak is not tolerated by the patient and has prompted a revision. Under ideal conditions hard-on-hard bearings are assumed to be operating under conditions of fluid film lubrication with very low friction. 14,15. However, if fluid film lubrication breaks down leading to dry sliding contact there will be a dramatic increase in friction. If this increased friction provides more energy to the system than it can dissipate, instabilities may develop in the form of friction induced vibrations and sound radiation. 16. Friction induced vibrations are a special case of forced vibration, where the frequency of the resulting vibration is determined by the natural frequency of the component parts. Running a moistened finger around the rim of a wine glass is an example of this. [Appendix]. The hypothesis of this study is that the squeaking sound that occurs in ceramic on ceramic hip replacement is the result of a forced vibration. This forced vibration can be broken down into a driving force and a resultant dynamic response. 17. The driving force is a frictional driving force and occurs when there is a loss of fluid film lubrication resulting in a high friction force. 14,15,18. The dynamic response is a vibration of a part of the device (the oscillator) at a frequency that is influenced by the natural frequency of the part. 16. By analyzing the frequencies of the sound produced by squeaking hip replacements and comparing them to the natural frequency of the component parts of a hip replacement this study aims to determine which part produces the sound. Materials and methods: In vitro determination of the natural frequencies of implant components Modal analysis has suggested that resonance of the ceramic components would occur only at frequencies above the human audible range and that resonance of the metal parts would occur at frequencies within the human audible range. Furthermore, that resonance of the combined ceramic insert and titanium shell would not be within the human audible range. To test this hypothesis we performed a simple acoustic analysis. The natural frequency of hip replacement components was determined experimentally using an impulse-excitation method (Grindo-sonic). Components were placed on a soft foam mat in a quiet environment and struck with a wooden mallet. The sound emitted from the component was recorded on a personal computer with an external microphone with a frequency response which ranges from 50Hz to 18,000Hz (Beyerdynamic MCE87, Heilbronn, Ger-many). The computer has an integrated sound card with a frequency response from 20Hz to 24kHz (SoundMAX integrated digital audio chip, Analogue Devices Inc, Norwood, M.A.) and we used a codec with a frequency response from 20Hz to 20kHz (Audio Codec ’97, Intel, Santa Clara, CA). Sound files were captured as 16 bit mono files at a sample rate of 48000Hz using acoustic analysis software (Adobe Audition 1.5, Adobe Systems Incorporated, San Jose, California, USA). We performed fast Fourier transform (FFT) of the sound using FFT size 1024 with a Blackmann-Harris window to detect the frequency components of the emitted sound. (Fast Fourier transform is an accepted and efficient algorithm which enables construction of a frequency spectrum of digitized sound). We tested the following components: modular ceramic/titanium acetabular components, which included testing the titanium shell and the respective ceramic inserts both assembled according to the manufacturer’s instructions and unassembled; titanium femoral stems and ceramic femoral heads both assembled and unassembled. A range of sizes of each component was tested according to availability from our retrieval collection. In vivo acoustic analysis: Sound recordings were collected from 31 patients. Nineteen recordings were made at our institution: 16 of these were video and audio recordings and 3 were audio only recordings. Video recording was with a digital video camera recorder (Sony DCR-DVD101E Sony Electronics, San Diego, CA, USA) with the same external microphone used in the in vitro analysis. For 3 patients who could not reproduce the sound in the office we lent them a digital sound recorder for them to take home and record the sound when it occurred (Sony ICD-MX20, Sony Electronics, San Diego, CA, USA). This device has a In vivo acoustic frequency range from 60Hz to 13,500Hz. The remainder of the recordings were video and audio recordings made by surgeons at three other institutions on digital video camera recorders. Sound files were captured and analyzed by the same method used in the in vitro analysis. Each recording was previewed in the spectral view mode which allows easy visual identification of the squeak in the sound recording. In addition all sound recordings were played, listening for the squeak. Once a squeak was identified a fast Fourier transform (FFT) was performed. We used FFT size 1024 with a Blackmann-Harris window which allowed us to easily pick out the major frequency components. All prominent frequency components were recorded at the beginning of the squeak and at several time points during the squeak if there was any change. A range was recorded for the fundamental frequency component. We were able to determine the frequency range of the recording device used by observing the frequency range of the background noise on the recording. We found that if a squeak was audible on the recording we had no difficulty determining its frequency regardless of the quality of the device used to make the recording or the amount of background noise. The mean age of the patients was 54 years (23 to 79 years), mean height was 171cm (152 to 186cm) and mean weight was 79kg (52 to 111kg). There were 17 female and 14 male patients. There were nineteen ABGII stem and ABGII cup combinations, 10 accolade stem and trident cup, 1 Exeter stem and trident cup and 1 Osteonics Securfit stem with an Osteonics cup. Ethics committee approval was obtained for this project from our institution and from the referring institutions and informed consent was gained from the patients. Finite element analysis of edge loading: Edge-loading wear which may provide a mechanism for failure of fluid film lubrication and may therefore play a role in squeaking. To evaluate edge loading further we conducted finite-element analysis (FEA). 9. Computed tomography (CT) scans of an intact pelvis were obtained from visual human data set (VHD, NLM, Bethesda, Maryland). Slices were taken at 1mm thick with no inter-slice distance through the entire pelvis. The CT files were then read into a contour extraction program and saved into an IGES file format which was imported into PATRAN (MSC Software, Los Angeles, CA) to develop the pelvic geometry. The pelvis was meshed with 10 noded modified tetrahedral elements. The model was reconstructed with a 54mm titanium alloy generic acetabular shell and a 28mm alumina ceramic liner. The acetabular shell and ceramic liner were meshed using 8 noded hexahedral elements. The shell-liner modular taper junction incorporated an 18° angle. The implant contact conditions (Lagrangian multiplier) allowed the liner and shell to slide with a friction coefficient of 0.9. Tied contact conditions were applied between the generic acetabular shell and the bone representing bone ongrowth. Bone material properties were extracted from the CT files by taking the Hounsfield value and the coordinates and mapping to the element in the model allowing us to calculate the Young’s modulus for each element . 19. Material properties for the shell and liner were based on published values. 20. for titanium alloy and alumina ceramic

Squeaking of ceramic-on-ceramic (CoC) hips is a clinical phenomenon that is concerning with regard to the long term performance of these joint devices. Investigations into the cause of the squeaking have focused on patient factors and demographics, surgical placement, and other non-ceramic components in the devices. The current study tests latest-generation CoC devices to measure the vibration modes and frequencies of the components individually as well as assembled in the complete surgical construct. Audio data from clinical cases of squeaking hips were analysed to determine the frequencies present. Retrieved CoC hips (n = 7) and never-implanted CoC bearing couples (n = 3) were tested in the laboratory for squeaking under loaded articulation. Bovine serum was introduced into the CoC articulation and dried to promote stick-slip motion at the articulation. Squeaking sounds from the in vitro tests were recorded for audio analysis. Low mass, high frequency-response ceramic shear piezoelectric accelerometers (PCB Piezotronics) were adhered to the hip components along multiple axes to measure vibrations during testing. Clinical audio shows that squeaking occurs at fundamental frequencies in the range of 1 to 3 kHz, with harmonics above the fundamental frequency. Retrieved CoC bearing couples squeaked at fundamental frequencies from 1.5 kHz to 3.8 kHz. Fourier Transform analysis of the audio closely matched the concurrent output from the accelerometers mounted directly on the ceramic components. This held true even in the absence of metal components in the system. With metal components included in the test construct (acetabular shell, acetabular cup, femoral stem), those components also vibrated at the same frequencies as the ceramic bearing couples, indicating that the CoC articulation is the source of the vibrations, with metal components conducting and emanating the sound. The never-implanted bearing couples were made to squeak and vibrated at fundamental frequencies ranging from 1 kHz to 8 kHz. Squeaking from CoC hips can be reproduced in the lab using components from clinical retrievals. Instrumentation of the explanted hips confirms that the vibration frequencies of the ceramic components themselves match the audible squeaking. The squeaking of ceramic components mounted with soft polymers and with no metal contact at any point indicates that the ceramic components themselves are the source of the clinical squeaking. The measured vibration of ceramic components in the audible range is an observation not predicted by modeling studies reported in the literature to date

Introduction. The Delta Motion device (developed by Finsbury Orthopaedics, Leatherhead, United Kingdom, now manufactured by DePuy, Leeds, United Kingdom) is a pre-assembled factory fitted cup. It has been introduced to overcome some of the concerns relating to intra-operative assembly with improper seating of the liner and chipping. This device has a thinner shell and liner in comparison with other cups, allowing the use of larger sized heads which should help reduce the risk of impingement and dislocation. A drawback of the pre-assembled design is the inability to use supplementary screws to achieve stability and the difficulty in obtaining primary stability compared with a thin titanium shell. To date we are not aware of any publications reviewing the outcomes of these devices. Methods. 206 DeltaMotion cups were implanted in 195 patients, between Dec 2008 to Dec 2009 by the three senior authors. All the hips had the same stem (Osteonics) and a ceramic head was used. Data was prospectively collected and we reflect on our two year results. Results. A total of 206 cups (123 F: 83 M) were implanted in 195 patients. The mean age at implantation was 69 years (range 38–93). 11 patients had bilateral hips (6M:5F). Complications were 1 pulmonary embolism, 2 femoral stem subsidence, 1 dislocation, 2 femoral fractures, 13 squeaking hips (9F:4M). The squeaking hips had a mean age of 65 years. Discussion. The main complication was ‘benign’ squeaking. This was more common in younger (mean age 64 years) females. This cohort has a squeaking rate of 6.3% which is higher than 3.1% previously reported by our unit. There was no squeaking when 36 mm heads were used. The risk of squeaking dramatically increased when cup sizes 60 mm and above were used with 48 mm heads. Although squeaking seems to have increased with this device, none of the patients required revision

Squeaking in ceramic total hip joint replacements has become a controversial topic. This study aims to document the incidence of squeaking and other noise generation in a single surgeon series for ceramic on ceramic total hip joint replacements. Possible aetiological for squeaking causes are explored. All patients from public and private who received ceramic on ceramic total hip joint replacements (Stryker trident-accolade) from 2002 to 2007 were identified via the New Zealand Joint registry. Following ethics approval all patients were contacted for a phone interview to question as to whether they had noted any noise generation. Patients who demonstrated noise generation were reviewed in clinic for full history and examination. Data including age, sex, weight, primary diagnosis, head size and cup size were obtained from clinical notes. Post operative x-rays were reviewed to analyse cup abduction and version. Forty one ceramic total hip joint replacements in a total of thirty seven patients were reviewed via telephone interviews. Three patients complained of squeaking in the ceramic bearing while one patient complained of a grinding and one other of clicking. Two of the three who had recognised the squeaking were both able to reproduce the squeaking in the clinic room. The third patient was noted to have crepitus from anterior patello-femoral osteoarthritis. There was no statistical difference in age, weight, primary diagnosis or head size. In terms of abduction and version of the acetabular cups that squeaked, one had twenty seven degrees of ante-version and forty seven degrees of abduction and the other fifteen degrees of anteversion and thirty degrees of anteversion. Four cups lay outside the recommended fifteen-thirty five degrees of anteversion and thirty five-fifty five degrees of abduction yet showed no squeaking. Neither patient is troubled by the squeaking and neither would seek revision surgery. The incidence of squeaking in ceramic on ceramic total hip joint replacements appears to be around five percent with a similar number of patients experiencing other noises. The position of the acetabular cup does not appear to be the sole contributor to the noise and other aetiological causes need to be further investigated