Introduction. Metal-on-Metal (MoM) bearing surfaces were historically used for young patients undergoing total hip arthroplasty, and remain commonplace in modern hip resurfacing. In theory, it has been postulated that metal ions released from such implants may cross the placental barrier and cause harm to the fetus. In light of this potential risk, recommendations against the use of MoM components in women of child-bearing age have been advocated. The purpose of this systematic review was to evaluate: 1) the Metal-on-Metal bearing types and ion levels found; 2) the concentrations of metals in maternal circulation and the umbilical cord; and 3) the presence of abnormalities in the fetus. Methods. A comprehensive literature review was conducted of studies published between January 1st, 1975 and April 1st, 2019 using specific keywords. (See Fig 1). We defined the inclusion criteria for qualifying studies for this review as follows: 1) studies that reported on the women who experienced pregnancy and who had a Metal-on-Metal hip implant; 2) studies that reported on maternal metal ions blood and umbilical cord levels; and 3) studies that reported on the occurrence of fetal complications. Data on cobalt and chromium ion levels in the maternal blood and umbilical cord blood, as well as the presence of adverse effects in the infant were collected. Age at parturition and time from MoM implant to parturition were also collected. A total of 6 studies were included in the final analysis that reported on a total of 21 females and 21 infants born. The mean age at parturition was 40 years (range, 24–41 years), and the mean time from MoM implantation to parturition was 47.2 months (range, 11–119 months). Results. Maternal blood cobalt levels were found as a weighted average of 33.94ug/L (0.972–143), while umbilical cord blood cobalt levels were found to be 22.07 ug/L(0.486–75). Cobalt levels were reduced by an average of 35% between maternal and umbilical cord blood. Maternal cord blood chromium levels were found as a weighted average of 9.25 ug/L (1–25), while umbilical cord chromium levels were found to be 1.30 ug/L(0.288–2.3). Chromium levels were reduced by an average of 86% between maternal and umbilical cord blood. No cobalt or chromium was detected in the umbilical cord blood of three patients. Out of the 21 infants born to women with MoM implants, 20 were born healthy with no adverse effects or complications. Conclusion. To date, there is a lack of consensus as to whether Metal-on-Metal hip arthroplasty implants are to be avoided in the child-bearing female population and whether it constitute a hazard to the fetus in-utero. Both chromium and cobalt ions were markedly reduced in levels when transitioning from maternal to cord blood. In particular, chromium showed a greater reduction on average than cobalt (86% vs. 35%). Based on the current evidence, there appears to be no correlation between the presence of metal ions in umbilical cord blood and complications, particularly congenital malformations in the fetus, as none of the infants experienced abnormalities uniquely attributable to the presence of metal ions. For any figures or tables, please contact the authors directly

High complication rates and poor outcomes have been widely reported in patients undergoing revision of large head metal-on-metal arthroplasty. A previous study from our centre showed high rates of dislocation, nerve injury, early cup loosening and pseudotumor recurrence. After noting these issues, we implemented the following changes in surgical protocol in all large head MOM revisions: One: Use of highly porous shells in all cases. Two: Use of largest femoral head possible. Three: Low threshold for use of dual mobility and constrained liners when abductors affected or absent posterior capsule. Four: Use of ceramic head with titanium sleeve in all cases. Five: Partial resection of pseudotumor adjacent to sciatic and femoral nerves. The purpose of the present study is to compare the new surgical protocol above to our previously reported early complications in this group of patients. We specifically looked at (1) complications including reoperations, (2) radiologic outcomes, and (3) functional outcomes. Complication rates after (Group 1), and before (Group 2) modified surgical protocol were compared using Chi-square test, assuming statistical significance p < 0 .05. Major complications occurred in 4 (8.3%) of 48 patients who had modified surgical technique, compared to 12 (38%) of 32 revisions prior to modification (p < 0 .05). Two hips of 48 (4.17%) endured dislocations in Group 1, compared to 9 of 32 (28%) in Group 2 (p < 0 .05). Four patients of 48 had repeat revision in Group 1: 2 for recurrence of pseudotumor, 1 for dislocation, and 1 for infection, compared to 6 patients who had 7 repeat revisions of 32 patients in Group 2: 3 for acetabular loosening, 3 for dislocation, and 1 for recurrence of pseudotumor (p=0.1). None of 48 revisions in Group 1 had acetabular loosening, compared to 4 of 32 in Group 2 (p=0.02). Two patients had nerve injury in Group 2, compared to none in Group 1 (p=0.16). The mean WOMAC pain score was 87.1 of 100 and the function score was 88.4 of 100 in Group 1, compared to a mean WOMAC pain score of 78 of 100 (p=0.6) and a function score of 83 of 100 in Group 2 (p=0.8). Modification of the surgical techniques described in the introduction has resulted in a significant decrease in complications in revision of large head MOM total hips. We continue to use this protocol and recommend it for these difficult cases

Introduction. This study reports outcomes of 35 revisions of a recalled metal-on-metal (MOM) monoblock prosthesis performed by a single surgeon. Methods. We prospectively collected data on all patients who underwent revision of a recalled metal-on-metal monoblock prosthesis between 2010 and 2015. Average follow-up was 2.5 years post-revision and 6.9 years post-primary procedure. We evaluated the cohort for age, BMI, gender, existence of medical comorbidities, and post-op complications. We compared pre and post-revision cup abduction angles, anteversion angles, combined angles, cup sizes, and Harris Hip Scores. Cobalt and chromium levels were followed throughout the study period for each patient. Results. Thirty-one patients underwent 35 revisions surgeries for pain, high metal ions, infection, aseptic loosening, failure of ingrowth, leg length discrepancy and/or pseudotumor. Two of these revisions were subsequently re-revised – one for continued pain and one for failure involving multiple dislocations, breakage of screws, and acetabular fracture. The survival rate for our revisions to date is 94.3%. Female patients comprised a majority of revisions (54%) despite comprising a minority (28%) of primary hip replacements using the studied prosthesis. Revised patients were an average of 51.8 years of age with a BMI of 31.07. Demographics are included on Table 1. There were five post-operative complications, including 2 infections, 2 dislocations, and one DVT. Cups were revised from a mean abduction angle of 47.5° in primary hips to 42.3° in revisions. Cups were revised from a mean of 53.4 to 57.8. Cobalt and chromium levels were followed in all patients and showed significant decrease after revision (Graph 1). Cobalt levels decreased from an average of 33.7 to 13.1 ng/mL while Chromium levels decreased from an average of 12.4 to 9.2 ng/mL. Harris Hip Scores increased significantly after revision (45.8 to 72.1). Conclusion. This study presents 35 revisions of a recalled monoblock hip prosthesis performed by a single surgeon at our institution from 2010 to 2015. To our knowledge, this is the largest single-surgeon study reported in the literature. Acetabular cups were revised to a lower average abduction angle. Patients have had significant improvements in Harris Hip Scores and significant decreases in Cobalt and Chromium levels after revisions. Our revision survival rate to date is 94.3% at an average of 2.5 years (range 2 weeks – 4.3 years). To view tables/figures, please contact authors directly

BACKGROUND. We originally performed metal-on-metal hip resurfacing using a Townley designed Vitallium Total Articular Replacement Arthroplasty (TARA) curved stemmed prosthesis. Neither the acetabular or femoral components were cemented or had porous coating. The bearing surfaces were consistently polar bearing. The surgical objectives were to preserve bone stock, maintain normal anatomy and mechanics of the hip joint and to approximate the normal stress transmission to the supporting femoral bone. The functional objectives were better sports participation, less thigh pain and limp, less perception of a leg length difference and a greater perception of a normal hip. Metal-on-metal was selected to conserve acetabular bone and avoid polyethylene associated osteolysis. Relatively few cases were performed until the Conserve Plus and later the Birmingham Hip Resurfacing systems became available. METHODS. We examined the results of metal-on-metal hip resurfacing in patient with at least 10 years of follow-up and an age less than 50 at the time of surgery. We did not have access to the Birmingham Prosthesis until 2006. We performed 101 TARA procedures and 397 Conserve Plus procedures for 357 patients. For the combined series the mean age was 43 and 62% of patients were male. 34 patients had a conventional total hip replacement on the contralateral side. We used both the anterolateral and posterior approaches. All acetabular components were placed without cement and all the Conserve Plus Femoral Components were cemented. RESULTS. There were no implant related failures with the TARA prosthesis. The average Harris Hip Score was 93. There were 2 revisions for femoral neck fracture at years 8 and 14 and one revision for infection. There was one dislocation but no instance of implant loosening. There were 29 (7%) revisions with the Conserve Plus Prosthesis. 14 revisions were for adverse reactions to metal wear debris and 10 of these patients had femoral components of size 46 mm or smaller. There were 5 revisions for acetabular loosening and 3 for femoral loosening. There were 7 revisions for femoral neck fracture and infection. The limb lengths were measured to be within 1 cm of equal in 98% of patients. 95% of patients had a UCLA activity score above 6 and 96% of patients rated their outcome excellent or good. 32 of 34 patients preferred their hip resurfacing to total hip replacement. The Kaplan-Meier survivorship was 93%. Narrowing of the femoral neck was seen in 9% of patients but acetabular osteolysis was not seen. Signs of impingement of the femoral neck against the acetabular prosthesis were seen in 14% of patients. CONCLUSIONS. Metal-on-metal hip resurfacing has been performed for more than 40 years using predicate prostheses such as the Townley TARA. The results of metal-on-metal resurfacing are favorable even in young and very active individuals. There were no instances of medical illness related to metal-on-metal implants with up to 41 years of follow-up. Metal-on-metal hip resurfacing has favorable outcomes at 10 years. There is an increased chance of an adverse reaction to metal wear debris with femoral component sizes 46 mm or smaller

Impact relief ability of Metal-on-Metal artificial hip joint with multi-garter spring using drop impact tester for practical use. Toshiaki Kaneeda, Xinming Zhao and Hiroshi Matsuura. Metal-on-metal (MoM) joints can provide better wear properties than hard-on-polymer joints, leading to reducing osteolysis. However during gait, MoM hip joints have no material to relieve impact. These impacts can cause severe pain in postoperative patients. Kaneeda proposed double-shell MoM artificial hip joints in which multi garter springs were inserted between the inner and outer acetabular shell as an impact relief device. The proposed double-shell metal-on-metal artificial hip joint is composed of two layers, as shown in Fig. 11). A garter spring is usually used when by loading and a compression stress from the outside to the center axis. In the model testing for garter spring, it is demonstrated that garter spring had impact relief ability, then using dual garter springs could lead to better impact relief ability than single one2). In this work, the impact relief ability of model hip joint were investigated by using the Instron CEAST 9340 machine as shown in Fig. 2. The machine is a floor standing impact system designed to deliver 0.30–405J of energy and equipped with precise locating system for height. A holding device of double-shell cup was made to fix the right position. A shape of drop impact weight was modified for this experiment. The model hip joint was applied vertical load over 6000N, which is estimated to be equal to maximum vertical load during jumping. The ability in the case of single garter spring and dual garter springs was evaluated in the model hip joint, comparing with UHMWPE liner in the same size of femur head. Each testing was conducted 10 times. Fig. 3 shows load-time curve detected. From the results, it can be seen that in both case Load L gradually rise with Time T, then reach maximum values, finally L gently drop: maximum impact load as well as maximum impact load arriving time also presented nearly the same values. Much differences in shape of the curve between model hip joint with dual garter springs and UHMWPE liner could not be recognized. The model hip joint with dual garter springs may has enough impact relief ability

Introduction. When following patients with metal-on-metal (MoM) hip replacements, current evidence suggests that orthopaedic surgeons should avoid reliance on any single investigative tool. In 2014, guidelines for stratifying patients with MoM hip replacement into groups of low, medium, and high risk of failure based on multiple criteria were published. However, such risk stratification guidelines can be difficult to interpret due to the numerous risk factors related to MoM hip replacements. This is especially true for patients with various (high and low) risk levels for different criteria within the guidelines. The first purpose of this study was to assess if a scoring system can be applied to the current MoM guidelines. The second purpose was to test, using this scoring system, how the contemporary guidelines would classify a cohort of patients with a recalled MoM hip replacement system. Methods. The study population consisted of 1301 patients (1434 hips) enrolled from September 2012 to June 2015 in a multicenter follow-up study of a recalled MoM hip replacement system at a mean of 6.2 (range 2.4 – 11.2) years from index surgery. Eleven required scoring criteria were determined based on existing follow-up algorithm recommendations and consisted of patient factors, symptoms, clinical status, implant type, metal ion levels, and radiographic imaging results. Criteria considered ‘low’ risk were given 1 point, 2 points for ‘moderate’ risk, and 3 points for the ‘high’ risk group. Forward stepwise logistic regression was conducted to determine the minimum set of predictive variables for risk of revision and assign variable weights. The MoM risk score for each hip was then created by averaging the weighted values of each predictive variable. Results. Only two of the proposed eleven criteria were found to be significant predictors of revision in our logistic regression model; clinical status (as measured by the Harris Hip Score) and blood metal ion levels. By September 2015, 85 patients had been revised. The median MoM risk score for unrevised hips (2.15) was lower compared to revised hips (4.49) (p < 0.001). Receiver operating characteristic analysis yielded good discrimination between all revised and unrevised hips, with an area under the curve of 0.82 (p < 0.001) (Figure 1). A high MoM risk score had 5.8-fold increased odds for revision relative to the moderate risk group (p < 0.001) and a 21.8-fold increased odds for revision compared to the low risk group (p < 0.001). Discussion and Conclusion. The MoM risk score is an effective tool for applying the current risk stratification guidelines to a cohort of patients with a MoM hip replacement. This scoring system is one way to simplify the interpretation of current risk stratification guidelines for patients with MoM hip replacements

The aim of this study is to investigate whether Metal-on-Metal (MoM) implants result in more chromosome aberrations and increased blood metal ions post-operatively when compared to Metal-on-Polyethylene (MoP) implants. Metal-on-metal arthroplasties are being inserted in increasing numbers of younger patients due to the increased durability and reduced requirement for revision in these implants. Recent studies have raised many concerns over possible genotoxicity of MoM implants. This is a prospective study of patients who have undergone elective total hip replacement, they were selected and then randomised into two groups. Group A received a MoP implant and group B received a MoM implant. Patients are reviewed pre-operatively (control group), at 3 months, 6 months, 1 year and 2 years post-operatively. On each occasion blood tests are taken to quantify metal ion levels (chromium, cobalt, titanium, nickel and vanadium) using HR-ICPMS method and chromosome aberrations in T lymphocytes using 24 colour fluorescent in situ hybridisation (FISH). 53 patients have been recruited to date. 24 of whom had MoP prosthesis and 29 a MoM. 37 of these have had their one year follow-up with blood analysis and 14 have had 2 year follow up. Cobalt and chromium concentration increased during the first 6 months in both MoM and MoP groups, in the MoM group the chromium levels were twice that of MoP group and 12x that of the preoperative samples. Chromosome aberrations occurred in both groups. At 6 months both the MoM and MoP groups showed increase frequency of aneuploidy aberrations with further increases after one year. Structural damage in the form of translocations occurred in the MoM group after one year, but not in the MoP group, by two years there was a profound increase in translocations Preliminary results of this study show that the levels of chromium and cobalt are significantly higher in the MoM group compared to the MoP group. This corresponds to increases in chromosome aberrations in the groups with increases in structural chromosome damage after two years

Purpose. Use of a large femoral head metal-on-metal bearing in total hip arthroplasty may offer an advantage in terms of dislocation rates and more natural joint kinematics. The acetabular component is more rigid however in these prostheses and if not placed accurately can lead to increased levels of metal ion release. A prospective randomized controlled trial was conducted to quantify bone mineral density on the acetabular side, as well as compare metal ion levels from a standard metal-on-polyethylene bearing to a large head metal-on-metal bearing in primary total hip arthroplasty. Method. Fifty patients were randomized to receive total hip arthroplasty with either the CONSERVE A-Class Total Hip with BFH femoral head or the Lineage acetabular component with polyethylene insert and cobalt chrome femoral head. There were 27 females (11 BFH) and 23 males (14 BFH), with a mean overall age of 61.6 (range 47.7–73.2). Serum levels of cobalt, chromium, and titanium were measured at regular intervals up to two years. Harris Hip Score, WOMAC, UCLA, and RAND-36 were completed at these same intervals. Standard radiographs as well as periprosthetic BMD were performed. Results. Bone mineral density in acetabular zones II, III, and IV was greater in the BFH group compared with the metal on poly group (p= 0.030, 0.046, and 0.019 respectively). Serum levels of cobalt (2.31 microg/mL vs 0.23 microg/mL, p=<0.001) and chromium (1.53 microg/mL vs 0.21 microg/mL, p=<0.001) were statistically higher in the BFH group compared with the metal-on-polyethylene group at one year post-op. There was no significant difference in serum titanium levels between groups. Conclusion. At short term follow up the load transfer to the acetabular bony bed differed between the two groups, with the more rigid shells demonstrating increased BMD in certain zones when compared with metal on poly. Serum levels of certain ions were 7–15 fold higher in the metal-on-metal large femoral head design compared with a standard metal-on-polyethylene. We await results on any clinical differences in performance and complications in this group of patients. Systemic implications of these ion levels are not known and further study is warranted

Metal-on-Metal devices generate significantly lower volumetric wear than conventional total hip replacements. However, clinically some patients may suffer some form of laxity in their joints leading to subluxation of the joint, which in turn may cause edge loading of an implant thereby increasing the chances of failure due to higher than expected wear. In this study, the effect of subluxation on MoM implant wear was investigated on a hip joint simulator. Materials & Methods. Two groups of 44 mm MoM devices were tested, n=3 in each group. The devices were subjected to 1 and 2 mm of subluxation. The flexion/extension was 30° and 15° respectively, internal/external rotation was ±10°, and cup inclination was 35°. The force was Paul type stance phase loading with a maximum load of 3 kN, with ISO swing phase load of 0.3 kN, run at 1 Hz. The test was carried out on a ProSim deep flexion & subluxation hip wear simulator (SimSol, UK). Rather than separating the head and the cup (microseparation), or reducing the swing phase load, this simulator is equipped with a novel mechanism to achieve translation of the head, while subjecting the devices to subluxation. During the swing phase, a controlled lateral force necessary for the translation of the head is applied by a cam mechanism, head retraction will then take place on heel strike. The lubricant used was new born calf serum with 0.2 wt. % sodium azide concentration diluted with de-ionised water to achieve average protein concentration of 20 g/l. Lubricant was changed every 250k cycles. Gravimetric wear measurements have been taken at 0.25 & 0.5 Mc stages. Results. Tests conducted with 1mm (Group 1) and 2mm (Group 2) subluxation significantly increased volumetric wear compared to standard hip simulator tests [1]. At 0.5 million cycles, group 1 and 2 produced an average volume loss of 4.38±0.98 mm. 3. (95% CL) and 7.07±1.64 mm. 3. (95% CL) respectively. Discussion/conclusion. Well positioned and well-fixed hip implants perform well in vitro and in vivo; however optimal performance a device can be affected by a number of factors from design, technical factors, patient factors, surgical technique to position of the device in vivo. The study presents test results of a hip joint simulator with a subluxation mechanism to simulate clinically relevant subluxation during the swing phase of a gait cycle under the ISO swing phase load of 0.3kN, with differing levels of luxation. Increasing the level of subluxation in turn increased volumetric wear due to greater head contact at the superior rim of the cup. Further tests will be conducted with high cup inclination angles (>45°) and subluxation to determine the effect upon wear. Tests which can simulate the (ideal and adverse) conditions clinically can help to improve the design and understanding of implant behaviour in vivo

Introduction. Failure rates of Metal-on-Metal (MoM) ASR XL hip implants have been unacceptably high compared with other bearing surfaces, so patients must be monitored over the time checking for disorders in clinical condition, blood tests or in diagnostic imaging. Objectives. We have carried out a continuing prospective investigation to evaluate the relationship between blood metal ions measurements and ultrasound levels and to evaluate if ultrasound score can predict a future indication to revision. Materials and methods. From DePuy Recall of 2010 we have monitored 106 patients (51 males, 55 females, mean age 63.6) with ASRXL implants. The controls were performed annually. The following scales were used for patients evaluation:. Ultrasound score: 0 none; 1 fluid collection <20 mm, 2 fluid collection <20 mm, 3 solid mass: metallosis. Blood metal levels of Chromium-Cobalt (Cr-Co) (μg/l = ppb): normal <3 ppb, alert between 3 and 7 ppb, pathologic <7 ppb. Clinical Score: Harris Hip Score. Rx score, evaluating the prosthetic-bone integration and the inclination of acetabular component. Patients who presented positive clinical-instrumental conditions and values of Cr and Co > 3 mg/l were checked every 6 months. Statistical analysis was carried out with Non-parametric Kruskal-Wallis test and two factors Analysis of Variance using SAS System vers. 9.4. Results. The follow-up included 110 implants (4 are bilateral case). 43 patients (39,1 %) underwent revision surgery for failed MoM utilizing ceramic-on-polyethylene devices. At a mean time of 65,7 +/− 15,9 months, 47 patients had a ultrasound score of 0 (13 revised), 32 patients had a ultrasound score of 1 (9 revised), 20 patients had a ultrasound score of 2 (15 revised), 7 patients had a ultrasound score of 3 (6 revised); 44 patients had Cr value < 3 ppb (5 revised), 28 patients had Cr value <3 ppb<7 (6 revised), 34 patients had Cr value <7 ppb (32 revised), 25 patients had Co value < 3 ppb (5 revised), 20 patients had Co value <3 ppb<7 (1 revised), 61 patients had Co value > 3 ppb (37 revised). A positive correlation between blood metal ions values and ultrasound levels (p<0,001) and a statistically significant interaction between ultrasound score and indication to revision (p=0,037) were found. Discussion and Conclusion. As reported in literature also in our experience the ASR XL implant was afflicted by an excessive revision rate, associated with levels of metal ions significantly higher than other hip bearing surfaces. Our results demonstrate a positive correlation between blood Cr and Co levels and the amount of fluid collection: at higher levels of fluid collection correspond higher levels of blood metal ions. Since statistical analysis confirmed that the level of ultrasound score is correlated with indication to revision it is suggested to use ultrasounds, if the score is 2 or more, as parameter to revise MoM implants even in absence of pathologic blood ions levels

Soft tissue reactions following metal-on-metal arthroplasty of the hip have been under discussion in recent times. The phenomenon has been observed since the advent of arthroplasty, but the particular nature of metal-on-metal (MoM) resurfacing or total hip arthroplasty (THA), and the associated shedding of metal particles in high wear states, appears to excite a more aggressive response. Recent reports suggest involvement of muscle groups on a wide scale, and some cases of neurovascular involvement. It is not known which reactions require widespread muscle excision, and which cases may be adequately addressed by bearing exchange alone. We report three cases of soft tissue reaction (pseudotumour) following MoM hip resurfacing all managed with revision to ceramic-on-ceramic (CoC) THA with minimal soft tissue excision. All patients were female with ages at original operation of 49, 52 and 58 years. Time to revision surgery was 85, 28 and 66 months respectively. Prosthesis revision resulted in progressive and satisfactory resolution of the pseudotumour. We propose that in the early stages, pseudotumour following MoM hip resurfacing can be adequately managed with revision to ceramic-bearing THA with minimal soft tissue excision, rather than revision with extensive soft tissue debridement that has been recently described

Metal-on-metal resurfacing offers an alternative strategy to hip replacement in the young active patient with severe osteoarthritis of the hip. The aim of this study was to compare functional outcomes, failure rates and impending revisions in hybrid total hip arthroplasties (THAs) and Birmingham Hip Resurfacings (BHRs) in young active patients. We compared the 5-7 year clinical and radiological results of the metal-on-metal BHR with hybrid THA in two groups of 54 hips each, matched for sex, age, body mass index and activity. Function was excellent in both groups as measured by the Oxford hip score (median 13 in the BHRs and 14 in the THAs, p=0.14), but the resurfacings had higher UCLA activity scores (median 9 v 7, p=0.001) and better EuroQol quality of life scores (0.90 v 0.78, p=0.003). The THAs had a revision or intention to revise rate of 8% and the BHRs 6%. Both groups demonstrated impending failure on surrogate end-points. 12% of THAs had polyethylene wear and osteolysis under observation, and there was femoral component migration in 8% of resurfacings. Polyethylene wear was present in 48% of hybrid hips without osteolysis. Of the femoral components in the resurfacing group which had not migrated, 66% had radiological changes of unknown significance (classification proposed). In conclusion, the early to mid-term results of resurfacing with the BHR appear at least as good as those of hybrid THA. Only by longer term follow-up will we establish whether the change of practice recorded here represents a true advance

Introduction. Large head total hip arthroplasty (THA) reduces dislocation rates and provides a theooretically larger range of motion. We hypothesised that this would translate into greater improvement in functional scores when compared to 28mm metal-on-polyethylene THA at 5 years. We believe ours to be the first in vivo comparison study. Methods. A multi-surgeon case-control study in a District General Hospital. The study group consisted of 427 patients with 452 hips, the 38mm uncemented metal-on-metal articulation THA (M2A/Bi-metric, Biomet UK). The control group consisted of 438 age and sex-matched patients with 460 28mm metal-on-polyethylene articulation THA (Exeter/Exeter or Exeter/Duraloc - Stryker UK. All patients were assessed in a physiotherapist led Joint Review Service as part of their standard follow up, with functional scoring using Oxford Hip (scored 0–48) and WOMAC scores (0–100). Results. The demographics for the 38mm and 28mm groups gave mean ages of 65.8 years and 66.4 years, 40.4% and 39.3% male respectively. Pre-operative functional scores were comparable, with Oxford Hip scores of 23.3 and 26.8 respectively, WOMAC 49 compared to 53. At each review point there was no statistical difference in either Oxford or WOMAC scores and this was sustained at 5 yrs. Dislocation rates in the 38mm group were lower (2.9% vs. 5%) though not statistically significant (p = 0.111). Revision rate was significantly higher in the larger head group, primarily due to adverse reaction to metal debris (4.6% vs. 2.0%). Conclusions. There is no functional difference between 38mm metal-on-metal THA and 28mm metal-on-polyethylene THA at five years. Dislocation rates were found to be lower in the 38mm THAs as would be expected, but this was not statistically significant. The difference in revision rates was found to be due to metal-on-metal adverse reactions to metal debris, and their use is therefore not advocated in the current climate

Performance of metal-on-metal (MOM) bearings was of great interest until recently. Major concerns emerged over high incidence of MOM-wear failures and initially there appeared greater risks with MOM total hip arthroplasty (THA) designs compared to resurfacing arthroplasty (RSA). Impingement of the metal neck against the THA cup was likely the differentiating risk. There is a major difference between RSA and THA in (i) size of femoral necks and (ii) risk of THA metal necks impinging on metal cups. For example, a 46mm THA with 12.5mm neck, a 3.68 head:neck (H/N) ratio, provides a suitably large range-of-motion (ROM). In contrast, an RSA patient with retained 31mm size of natural neck would only have H/N = 1.48, indicating even less ROM than a Charnley THA. However, the enigma is that RSA patients have as good or better ROM in majority of clinical studies. We studied this apparent RSA vs THA dilemma by examining MOM retrievals for signs of adverse impingement. We previously described CoCr stripe wear in failed THA bearings, notably alignment of polar and basal wear stripes coincident with the rim profiles of the cups (Clarke 2013). Our governing hypothesis was that RSA patients had to routinely sublux their hips to get ROM comparable to THA. Our THA impingement studies showed polar stripes within 15o of the polar axis in large heads. For the various RSA diameters, we calculated that wear stripes angled 40o from the femoral axis could indicate impingement with no subluxation, whereas smaller angles would indicate routine subluxation of RSA femoral-shell from cup. We compared explanted RSA (N=15) and THA (N=15) bearings representing three vendors (42–54mm diameters). Wear maps and head-stripes were ink-marked for visualization, photography, and analysis. Wear areas were calculated using spherical equations and wear-stripe angles measured by computer graphics. The results showed that RSA femoral shells had wear areas circular in shape with areas varying 1,085- 3,121mm2. These averaged 14% larger than in matched THA heads but statistically significant difference was not proven. Polar stripes were readily identifiable on femoral components, 75% for RSA cases and 100% for THA. These contained identical linear scratches and all were sited within 30o of neck axis, confirming our hypothesis that RSA patients had to sublux their hips to achieve same motion as THA. Examination of cup wear areas revealed all showed ‘edge-loading’, but RSA cups had a significantly greater degree. Retrieval studies are limited by uncontrolled case sources, varied brands, and small numbers. In this study, we were able to match RSA and THA cases by vendor and diameter. The RSA retrievals revealed polar stripes identical to THA by site, topography and inclination to femoral-neck axis. This confirmed our starting hypothesis and explained the large clinical ROM available in RSA patients. The larger wear areas on RSA femoral shells, although not statistically significant, and the larger ‘edge loading’ sites in RSA cups appeared as further support for routine subluxation of femoral-shells during hip impingement

This study aims to investigate femoral blood flow during Metal-on-Metal Hip Resurfacing (MMHR) by monitoring oxygen concentration during the operative procedure. Patients undergoing MMHR using the posterior approach were evaluated. Following division of fascia lata, a calibrated gas-measuring electrode was inserted into the femoral neck, aiming for the supero-lateral quadrant of the head. Baseline oxygen concentration levels were detected after electrode insertion 2-3cm below the femoral head surface and all intra-operative measures were referenced against these. Oxygen levels were continuously monitored throughout the operation. Data from ten patients are presented. Oxygen concentration dropped most noticeably during the surgical approach and was reduced by 62% (Std.dev +/-26%) following dislocation and capsulectomy. Insertion of implants resulted in a further oxygenation decrease by 18% (Std.dev +/-28%). The last obtained measure before wound closure detected 22% (Std.dev +/-31%) of initial baseline oxygen levels. Variation between subjects was observed and three patients demonstrated a limited recovery of oxygen levels during implant insertion and hip relocation. Intra-operative measurement of oxygen concentration in blood perfusing the femoral head is feasible. Results in ten patients undergoing MMHR showed a dramatic effect on the oxygenation in the femoral head during surgical approach and implant fixation. This may increase the risk of avascular necrosis and subsequent femoral neck fracture. Future experiments will determine if less invasive procedures or specific positioning of the limb can protect the blood supply to femoral neck and head

Background:. Failed metal-on-metal (MOM) bearings and corrosion reactions are being increasingly encountered with little to guide evaluation for periprosthetic joint infection (PJI). Our purpose was to determine the utility of the erythrocyte sedimentation rate (ESR), C-Reactive Protein (CRP), synovial fluid white blood cell (WBC) count and differential (%PMN) in diagnosing PJI in failed hips with a MOM bearing or corrosion. Methods:. 150 revision hips (92 MOM total hip arthroplasties, 19 MOM hip resurfacings, 30 non-MOM bearings with corrosion and 9 full-thickness bearing surface wear with metallosis) were retrospectively evaluated. Nineteen patients were diagnosed as infected using MSIS criteria. Mean laboratory values were compared between groups and receiver operator characteristic curves (ROC) generated with an area under the curve (AUC) to determine test performance and optimal cutoffs. Results:. The synovial fluid WBC count was judged to be inaccurate secondary to cellular debris in 47 of the 141 patients where one was obtained (33.3%); a WBC count was still reported, however, in 35 hips, 11 of which were falsely positive. Infected patients had significantly higher mean serum ESR, CRP, synovial fluid WBC count, and differential (p < 0.0001, all). The best tests for diagnosis of PJI were the synovial fluid WBC count (AUC=98%, optimal cutoff 4350 WBC/μL), and differential (AUC = 90%, optimal cutoff 85% PMN). Diagnostic performance of the synovial fluid WBC count and differential improved with fewer false positives after excluding inaccurate samples. The ESR and CRP both had good sensitivity. Conclusions:. The diagnosis of PJI is extremely difficult in patients with MOM bearings or corrosion and the synovial fluid WBC count can frequently be falsely positive and should be relied upon only if a manual count is done and if a differential can be performed. A more aggressive approach to preoperative evaluation for PJI is recommended in these patients to allow for careful evaluation of the synovial fluid specimen, the integration of synovial fluid culture results, and repeat aspiration if necessary

Introduction. This study reports outcomes of primary and revision total hip arthroplasties of a recalled metal-on-metal (MOM) monoblock prosthesis performed by a single surgeon. Methods. We performed a retrospective review of all patients who underwent both primary and revision total hip arthroplasties at our institution between 2006 and 2014. Only those patients who underwent primary recalled MOM monoblock prosthesis placement and/or revision of the recalled prosthesis were included. We evaluated revision group versus non-revision group for age, BMI, gender, existence of medical comorbidities, primary cup abduction and anteversion, primary combined angle, post-operative complications, cobalt and chromium ion levels, and Harris Hip Scores. Student t-test was used to compare groups. Results. During the study period, 105 patients underwent 115 primary total hip arthroplasties with the recalled system. Thirty-six patients underwent 40 revisions surgeries for pain, high metal ions, infection, aseptic loosening, failure of ingrowth, and/or pseudotumor. The revision rate was 34.8%. Except for a higher percentage of women undergoing revision (17.4% vs 50%, p=0.0002), there were no significant differences in patient demographics, medical comorbidities, or pre-operative Harris Hip Scores (Table 1). Revision group showed higher cup abduction angles (47.8 vs 42.4, p = 0.005), smaller average cup size (53.3 vs. 55.2, p = 0.003), smaller average femoral component size (4.7 vs 5.6, p = 0.02, respectively), and lower post-operative Harris Hip Scores (87.9 vs 93.8, p = 0.0007). The revision group had higher cobalt levels (34.5 vs 5.8, p = 0.00003) and higher chromium levels (14.0 vs 1.3, p = 0.00003). There were five post-operative complications in the revision group (2 infections, 2 dislocations, and one DVT) versus one DVT in the non-revision group (p=0.01). Harris Hip Scores for revision surgeries increased from a mean of 44.2 pre-operatively to 74.9 post-operatively (p=1.45×10. −5. ). Conclusion. This study presents 115 primary total hip arthroplasties and 40 revisions performed by a single surgeon at our institution. To our knowledge, this is the largest single-surgeon study reported in the literature. Hips requiring revision had significantly higher cup abduction angles, smaller cup and femoral component sizes, lower post-operative Harris Hip scores, and higher metal ion levels. Age, BMI and comorbidities did not contribute to revision in our study; however, there was a higher chance of undergoing revision if you are a woman (p=0.0002). There was a 30.7 mean improvement in Harris Hip Score after revision

Purpose. Metal-on-Metal (MoM) hip bearings are being implanted in ever-increasing numbers and into ever-younger patients. The consequence of chronic exposure to metal ions is a cause for concern. Therefore, using cytogenetic biomarkers, we investigated a group of patients who have had MoM bearings in situ for in excess of 30 years. Method. Whole blood specimens were obtained from an historical group of patients who have had MoM bearings in situ for in excess of 30 years. Blood was also obtained from an age and sex matched control group and from patients with Metal-on-Polyethylene (MoP) components of the same era. The whole blood was cultured with Pb-Max karyotyping medium and harvested for cytogenetics after 72 hrs. The 24 colour FISH (Fluorescent In Situ Hybridisation) chromosome painting technique was performed on the freshly prepared slides, allowing chromosomal mapping. Each slide was evaluated for chromosomal aberrations (deletions, fragments and translocations) against the normal 46 (22 pairs and two sex) chromosomes. At least 20 metaphases per sample were scored and the number of aberrations per cell calculated. Results. Chromosomal aberrations, including deletions, fragments and translocations were only detected in the peripheral blood lymphocytes isolated from the group that had MoM bearings. These changes were not present in the age and sex matched control group. The chromosomal aberrations were also detected in the patients previously exposed to MoM bearings who have been revised to a MoP articulation. Conclusion. We have detected dramatic chromosomal aberrations in peripheral blood lymphocytes in a group of patients chronically exposed (over 30 years) to elevated metal ions. It is not known whether these aberrations have clinical consequences or whether they are reproduced in other cells in the body. The results emphasise the need for further investigations into the effect of chronic exposure to elevated metal ions produced by orthopaedic implants

Introduction. High early failure rates have been reported with certain metal-metal surface arthroplasties and good results have been reported with others. This is a minimum 10-year review of the first 1000 consecutive resurfacings including all ages and diagnoses from one centre. Methods. The first 1000 surface arthroplasties (892 patients) were followed-up with postal questionnaires. Of these the first 402 hips (350 patients) were also invited for a clinico-radiological review. 54 patients (63 hips) died 6.7 years (0.7–12.6) later due to unrelated causes. Mean follow-up is 12.2 years (range 10.8–13.7). Radiographs were assessed independently by a senior musculoskeletal radiologist. Results. There were 33 revisions at a mean of 7 years (0–11.6) following operation, 15 femoral failures (0.6%), 6 infections (1.5%) and 12 wear-related failures (1.2%) including 7 pseudotumours (0.7%). With revision for any reason as the end-point Kaplan-Meier survival analysis showed 97.5% survival at 10 years and 96.5% at 13 years. Single zone socket lucencies were found in 2.7% and 5.7% on the femoral side and two zone lucencies in 2.1% on the acetabular side only. No 3-zone lucencies or component migration were seen. Discussion and Conclusion. Our study shows that the performance of modern metal-on-metal resurfacing arthroplasty continues to be good at 10 year follow-up. Even though the incidence of radiographic adverse features, wear-related failures and pseudotumours is low at this stage it continues to raise concern about long-term implications

Between April 2008 and February 2012, we implanted 159 large-diameter MOM stemmed THA with head diameters of 38–50mm. There were 6–38mm, 22–40mm, 42–42mm, 42–44mm, 24–46mm, 13–48mm, 4–50mm, 5–52mm, and one-54mm heads implanted in 138 patients (21 males and 117 females). The pre-operative diagnoses included: 120 OAs, 12 IONs, 4 femoral neck fractures, one RA, and one post-traumatic OA. Their ages were 40–86 years (avg. 63.6 yrs). Follow up was 4 to 67 months post implantation (avg. 40.4 months). All implants were manufactured by one company (Wright Medical Technology, Arlington, TN, USA). The stems were of a standard titanium-aluminum alloy, either 44 ANCA-FIT or 115 PROFEMUR Z non-cemented stems. Acetabular components were all CONSERVE PLUS cobalt-chromium monoblock shells. Heads were also fabricated out of cobalt-chromium alloy, with modular junctions. Patients with complaints of groin pain and/or swelling or hip instability underwent MRI examination in order to detect the presence of fluid collections or soft tissue masses. The statistical correlation between abnormal findings on MRI and age, gender, head diameter, component position and duration post-surgery was performed. 35 hips in 31 patients (22.0%) were found to have either a fluid collection or “pseudotumor” on MRI. These were in 5 males and 26 female patients. According to Hart's MRI classification, they were classified 21 hips in Type 1, twelve hips in Type 2, and two hips in Type 3 (Fig. 1, 2 and 3). 8 hips in 8 patients who had any pseudotumors were undergone revision THA (Fig. 4, 5 and 6). All hips had corrosions at head-neck taper junctions (Fig. 7). There was no difference in age between these two groups of patients (63.7 vs. 63.6 yrs.), but a significant difference in duration from the time of implantation of two groups (23.9 vs. 44.8 months). There appeared to be no significant difference between the mean head diameter of the two groups, 43.2mm and 44.0mm respectively. There was no statistical difference between the two groups with regard to implant orientation: cup inclination 18–70 degrees (41.8 vs. 43.6 degrees); cup anteversion −13–49 degrees (15.1 vs. 14.7 degrees); stem anteversion 2–48 degrees (20.1 vs. 23.3 degrees); and stem offset 17.5–56.2mm (38.2 vs. 37.8mm). Furthermore, according to Lewinnek's safe zone, there was no difference in cup orientation between the two groups (Fig. 8). When we investigated the types of modular neck, the hips having any pesudotumors tended to have long or varus necks. In this study, it is important to emphasize that the appearance of symptoms and development of a pseudotumor occurred early after a MOM THA in some patients. Also it will be important to subject all patients to MRI examination to evaluate the possibility of “silent” fluid collections and pseudotumors. In large-diameter head metal-on-metal stemmed THAs, femoral stems having long or varus neck may contribute to head-neck junction failure