I believe ceramic-on-polyethylene should be used in all patients undergoing THA. I believe the issues that one must look at include wear and osteolysis, bearing fracture and in 2018 corrosion/adverse local tissue reaction (ALTR). If one looks at these aspects it is clear ceramic-on-polyethylene is the bearing of choice. In the literature, there is a paucity of studies comparing metal-on-polyethylene with ceramic-on-polyethylene total hips. The data suggests no real difference in survivorship but less wear. However, most studies are not comparative studies and are underpowered to see these differences. The only data that is powered to see these differences is registry data. In first decade survivorship of metal-on- polyethylene is similar to ceramic-on-polyethylene. However, in the second decade the advantage is clearly with ceramic-on-polyethylene. However, in 2018, the major issue is corrosion and subsequent ALTR. While corrosion at the femoral head and stem taper has been seen for many years, in 2012 an article by Cooper et al. highlighted that this corrosion may lead to ALTR. They reported on 10 cases with variable presentation and no specific factor was found in their study or any study to date that will lead to corrosion and ALTR. More recently, a study from our center highlighted that dislocation may be the first presentation of ALTR. In this study, 10 cases of dislocation presented at an mean of 8 months with their first dislocation. Components were well positioned and it was concluded that the ALTR was the cause for the dislocation. Today any patient with new onset pain, stiffness or instability with a metal-on-polyethylene THA should be worked up for ALTR. The question of why this is happening now is important to answer. Numerous theories have been proposed, most likely it is a combination of these factors: change in trunnion dimension/surface, increasing head size, trunnion preparation and impaction force. It also appears to be stem dependent. In a study by McGrory et al. they found a 1% prevalence of ALTR in just over 1300 cases with one particular femoral stem. At present, however, we cannot predict at all which patient will develop ALTR and therefore we have gone to ceramic-on-polyethylene in all our THAs. In summary, the ideal bearing has low wear, low corrosion potential, generalizable, easy to revise, versatile, biocompatible and safe. In 2018, ceramic-on-polyethylene as a bearing fulfills all these criteria and should be the bearing of choice in total hip replacement

High failure rates have been associated with large diameter metal-on-metal total hip replacements (MoM THR). However there is limited literature describing the outcomes following the revision of MoM THR for adverse local tissue reaction (ALTR). A total of 98 large diameter MoM THRs underwent revision for ALTR at our institution. The data was obtained from the clinical records and included the demographics, intra-operative findings of ALTR and post-operative complications. Any subsequent procedures and re-revision for any reason was analysed in detail. The clinical outcome was measured using functional outcome scores using the Oxford hip score (OHS), Western Ontario and McMaster Universities osteo-arthritis index (WOMAC) score and Short Form (SF12). The mean age of the patients at the time of revision was 58.2 yrs. At a mean follow-up of 3.9 years (1.0 to 8.6) from revision for ALTR, there were 15 hips (15.3 %) with post-operative complications and 8 hips (8 %) requiring re-revision. The Kaplan–Meier five-year survival rate for ALTR revision was 91 % (95% confidence interval 78.9 to 98.0). There were no statistically significant predictors of re-revision. The rate of postoperative dislocation following revision was 9.2% (9 hips). The post-operative functional outcome depends on the intra-operative findings of tissue destruction secondary to ALTR. The short term results following revision of large diameter MoM THR for ALTR are comparable with other reports in the literature. The use of constrained liners reduces the incidence of post-operative dislocation. There is an increased risk of postoperative instability following revision THR for ALTR. Early identification and intervention seems to be the logical approach in the management of patients with ALTR

Introduction:. To date, there have been few reports of the results of revisions for failed metal-on-metal hip arthroplasties (MoM HA's). These series have included relatively modest numbers, and classification of the severity of adverse local tissue reaction (ALTR) has been under-reported. In this study, early outcomes and complications are analyzed as a function of pre-operative MRI grade and intra-operative ALTR severity to determine their prognostic value. Methods:. This is a retrospective review of revisions of 121 failed MoM HA's performed between 2008 and 2012. Indications for revision include ALTR (n = 97), loose cup (n = 13), and combined loose cup and ALTR (n = 11). When pre-operative MRI's were available, these were graded according to Anderson's system by 2 radiologists who were blinded to the clinical results. Intra-operative findings were graded for severity according to an ALTR classification. Post-operative complications were recorded. Correlations between pre-operative MRI grade, intra-operative ALTR classification and post-operative complications were analyzed using Spearman's rank correlation. ALTR Classification:. Type 0: No abnormal fluid or pseudotumor. Peri-articular structures intact. Type 1: Abnormal fluid and/or pseudotumor. Peri-articular structures disrupted but repairable. Type 2: Abnormal fluid and/or pseudotumor. Peri-articular structures disrupted and no meaningful repair possible. Type 3: Abnormal fluid and/or pseudotumor. Peri-articular structrues disrupted, no meaningful repair possible, AND significant necrosis involving abductor muscles. Results:. The average time to revision was 47 months (range: 7–198 months). In cases where the cup required revision, the average increase in outer diameter was 4.1 mm (range: 2–10 mm). Average revision head size was 38 mm (range: 32–48 mm). 19 patients (16%) experienced at least one complication which included dislocation (n = 12/10%), infection (n = 6/5%), recurrent pseudotumor requiring surgery (n = 2/1.7%), and VTE (n = 1/0.9%). The pre-operative MRI grade correlated significantly with the intra-operative ALTR classification (p = 0.03), and both the MRI grade and ALTR classification correlated significantly with post-operative complications (p < 0.01). Among the 23 patients with the most severe ALTR's (Type 2 and 3), 11 patients (48%) experienced complications. Conclusion:. Revisions for failed MoM HA's can be heterogenous with varying degrees of soft tissue compromise. Despite the use of large femoral head sizes in the current series, the overall dislocation rate was 10%. The pre-operative MRI grade and intra-operative ALTR classification have good prognostic significance and may alert the surgeon and patient to an increased potential for complications after surgery

INTRODUCTION. Corrosion of modular tapers is increasingly recognized as a source of adverse tissue reaction (ALTR) and revision surgery in total hip arthroplasty (THA). The incidence of corrosion and rate of revision for ALTR may differ among different types of implants. OBJECTIVE. The objective of this study was to determine if a difference exists in rate of THA revision for corrosion and ALTR with tapered broach only stems compared to ream-broach femoral stems. METHODS. We reviewed the results of 3741 primary THA performed over a 5 year period at our institution using 2 different implants by the same manufacturer, a tapered proximally coated cementless titanium stem inserted via a broach only technique (Group A) and dual tapered proximally coated cementless titanium stem inserted via a ream and broach technique (Group B). RESULTS. Of 1567 THA in group A, 964 were combined with a chrome cobalt metal head, while 603 were ceramic. Of 2174 THA in group B, 1302 were metal and 872 were ceramic. Head sizes used were similar between groups. The same polyethylene was used in all THA. At a minimum follow-up of 2 years and average follow-up of 5 years, the overall revision rate for all causes was 3.1% in group A and 1.4% in group B. There were 29 revisions for ALTR due to corrosion of the morse taper junction in group A (3.4%) and 0 in group B. Univariate and multivariate analysis indicated no relationship between revision for corrosion/ALTR and age, gender, stem size, stem offset and head size. A significant relationship was identified between revision and head length, with an increased rate of revision among longer head lengths. There were no revisions for corrosion, ALTR or unexplained pain among patients receiving ceramic heads in either group. CONCLUSION. There was a significant difference in the rate of revision for corrosion and adverse tissue reaction encountered with the use of stem A when compared to stem B. The stem geometry, taper geometry and exact metallurgy of these femoral components likely influences the incidence and severity of taper corrosion, however, more research is required to identify the exact contributions of these factors

Adverse local tissue reactions (ALTR), such as so-called pseudotumours associated with metal-metal bearings, can also occur secondary to corrosion products from modular tapers where at least one side is composed of cobalt alloy. In 1988, Svensson et al. reported a fulminant soft-tissue pseudotumour following a cementless, metal-on-polyethylene total hip. This case had all of the features of ALTR that were subsequently observed in association with contemporary large diameter metal-metal bearings, having the same histological characteristics that Willert and colleagues termed ALVAL in 2005. There is a documented increased risk of femoral taper corrosion in association with larger diameter (>32 mm) metal-metal bearings. There may be a generic increase in the risk of taper corrosion with larger diameter bearings, regardless of acetabular bearing type. Other variables include the design and manufacturing tolerances of the taper and head, the stiffness of the neck, implantation time, and possibly in vivo assembly. Head and neck moment arm and neck length have not been demonstrated to be independent risk factors for taper corrosion or fretting. Retrieval analyses indicate that fretting and corrosion tend to be higher on the head than on the stem. ALTR has similarly been described in association with corrosion of the modular neck-stem junction. Taper corrosion is the probable explanation for elevated ion levels and ALTR in association with well-positioned metal-metal total hip bearings and low bearing wear. Whole blood or serum metal levels are elevated with a greater elevation of cobalt compared to chromium. Ion analyses are now relatively accessible and reliable and should be obtained in the evaluation of a painful total hip without an obvious cause. Cross-sectional imaging, such as a MARS MRI scan, can demonstrate associated changes in the periprosthetic tissues and secure the diagnosis. Treatment recommendations are similar to those established for hips with metal-metal bearings and ALTR. Removal of the modular cobalt alloy head and/or neck component is recommended. At this time, there are no established criteria for the degree of “acceptable” femoral taper damage. The dilemma faced by the revising surgeon is whether to expose the patient to the potential morbidity associated with revision of a well-fixed femoral stem, particularly a distally-fixed, extensively porous-coated stem, in the setting of mild-to-moderate fretting and corrosion of the femoral taper. Several manufacturers offer ceramic heads with a titanium alloy taper sleeve inside the head specifically for mating to previously used femoral tapers. It is not recommended to put a ceramic head taper directly onto a used femoral taper. Surface damage of the used femoral taper can create high localised stresses in the ceramic head and predispose to head fracture. The same principles can be applied to corrosion of a stem-neck taper. If the modular neck is made of cobalt alloy, it is preferable to exchange it for one made of titanium alloy (if available). Again, there are no established criteria for the degree of “acceptable” femoral taper damage. The paucity of reported experience with such revisions inhibits further comment at this time. It is prudent to be suspicious of “taperosis” considering that the majority of heads used over the past 5 years are cobalt alloy and >36 mm in diameter, many contemporary stems have narrower, and hence more flexible necks, some tapers are smaller (shorter), more variable in vivo assembly secondary to “minimally invasive” surgical techniques, and the risk of taper corrosion increases with time in situ. Additional studies are needed to determine the incidence of clinically significant taper corrosion. There are more than 30 different head-stem tapers worldwide and the incidence of clinically significant taper corrosion is likely variable for different head-stem combinations. Similar to ALTR that occur with metal-metal bearings, some cases of ALTR secondary to taper corrosion may be asymptomatic

Introduction. Neck-stem corrosion has been associated with Adverse Local Tissue Reaction (ALTR) in dual-taper femoral stems. Several diagnostic tests, of varying specificity and sensitivity, are used to identify ALTR. The purpose of this study was to document the clinical presentation, diagnostic workup and surgical findings in a large cohort of patients with dual modular stems, and use this information to propose an evaluation protocol that assists surgical decision-making. Methods. This is a single center, single surgeon's retrospective case series of 38 patients who underwent 42 primary total hip arthroplasty (THA) with a dual-taper femoral components between March 2010 and May 2011 The evaluation included clinical exam, hip radiographs, labs including serum metal ion levels, metal artifact reduction sequence magnetic resonance imaging (MARS MRI), and fluoroscopic hip aspiration with qualitative and quantitative assessment of synovial fluid. Each hip aspirate was classified into Class 1 (clear, <10cc), 2(brown, clear, >10cc), or 3 (cloudy, turbid, viscous). 20 patients to date have undergone revision THA. Results. 19/42 hips were symptomatic. Serum cobalt levels were elevated in 38/42 patients. 23/42 had abnormal MRI findings. MRI was able to identify abnormalities in 79% (15/19) of symptomatic patients and 35% (8/23) asymptomatic patients. Class 2 and 3 hip aspirates were associated with abnormal MRI (in 86% and 61%, respectively), elevated Cobalt, and a high rate of revision (71% and 72%, respectively). ESR and CRP were normal in most patients (76% and 66%, respectively). A small subset of patients (2/38) with symptoms, normal metal ion levels and normal MRI, had abnormal aspirates (Class 2 or 3) with extensive tissue necrosis at revision. Conclusion. The diagnosis of ALTR can be challenging and requires integrating data from several sources: clinical exam, radiographs, serum metal testing, MARS MRI and hip aspirations. Hip aspiration appears to be useful not only in excluding infection, as proposed in current literature, but also in identifying ALTR in patients with otherwise normal tests. Abnormal results on MARS MRI and/or hip aspiration appear to be most predictive of surgical pathology. Both should be included in the protocol to evaluate for underlying ALTR in patients with dual-taper femoral stems

Introduction. Taper corrosion at modular junctions can cause a spectrum of adverse local tissue reactions (ALTR) in the periprosthetic soft tissues in patients who have undergone total hip arthroplasty (THA). Because these reactions are usually painful, taper corrosion has become part of the differential diagnosis of hip pain following THA. However these destructive lesions may not always cause pain, and can occasionally result in other atypical presentations. The purpose of this study is to describe a cohort of patients presenting with late and recurrent instability following THA due to underlying ALTR and taper corrosion. Methods. This is a multicenter retrospective case series of fourteen patients presenting with late instability secondary to ALTR and corrosion at the modular head-neck taper. The cohort included nine women and five men with a mean age of 66.8 years (range, 49 to 74). All patients had a metal (CoCr)-on-polyethylene bearing surface, but had a range of CoCr and Ti-alloy stem designs from three different manufacturers. Seven patients had 28 mm heads, while the rest had 32–40 mm heads. Patients experienced a mean of 3.4 dislocations (range, 2 to 6) at an average of 5.2 years (range, 0.4 to 17.0) following their index surgery. Although most reported some degree of discomfort around the hip, instability was the primary presenting symptom in all fourteen patients, and four were otherwise completely asymptomatic. Serum metal levels demonstrated a greater elevation of cobalt (mean 3.13 ng/mL) than chromium (mean 2.33 ng/mL). Preoperative infection workup including serum inflammatory markers and a hip aspiration documented the absence of sepsis. Results. Radiographic analysis demonstrated cups were well positioned, with a mean abduction angle of 43.2° (range, 40° to 48°) and mean anteversion angle of 19.5° (range, 16° to 26°). Hips were revised at a mean of 7.4 years (range, 2.4 to 19.4) following their index surgery. At the time of revision, ALTR was encountered in every case, with extensive tissue necrosis and abductor damage or insufficiency in the majority. The modular head-neck junction demonstrated visible corrosion seen as fretting, surface damage, and deposition of a black, flaky material. Constrained liners were placed in all patients. Conclusions. Although ALTR resulting from modular taper corrosion typically presents with hip pain, some patients can present with recurrent instability in the absence of other significant symptoms. Recurrent instability in the setting of otherwise well-positioned components and without another obvious cause should raise concern for ALTR as a potential underlying etiology

Introduction. Complication and revision rates have shown to be high for all metal-on-metal (MoM) bearings, especially for the ASR Hip System (ASR hip resurfacing arthroplasty (HRA) and ASR XL total hip arthroplasty (THA)). This prompted the global recall of the ASR Hip System in 2010. Many studies have previously explored the association between female gender and revision surgery MoM HRA implants; yet less research has been dedicated to exploring this relationship in MoM THA. The first purpose of this study was to assess the associations between gender and implant survival, as well as adverse local tissue reaction (ALTR), in patients with MoM THA. Secondly, we sought to report the differences between genders in metal ion levels and patient reported outcome measures (PROMs) in patients with MoM THA. Methods. The study population consisted of 729 ASR XL THA patients (820 hips) enrolled from September 2012 to June 2015 in a multicenter follow-up study at a mean of 6.4 (3–11) years from index surgery. The mean age at the time of index surgery was 60 (22–95) years and 338 were women (46%). All patients enrolled had complete patient and surgical demographic information, blood metal ion levels and PROMs obtained within 6 months, and a valid AP pelvis radiograph dating a maximum of 2 years prior to consent. Blood metal ion levels and PROMs were then obtained annually after enrollment. A sub-set of patients from a single center had annual metal artifact reduction sequence (MARS) MRI performed and were analyzed for the presence of moderate-to-severe ALTR. Results. Eighty-nine hips (11%) were revised during the study period. Forty-five of the 338 men underwent revision (13%), and 44 of the 391 women underwent revision (11%). The mean time from index surgery to revision was 7 years for both males and females. After controlling for confounding variables, the only variables found to be associated with revision surgery in patients with unilateral THA were VAS pain (hazard ratio [HR], 1.28; p < 0.001) and elevated cobalt metal ion levels (HR, 1.02; p < 0.001). Patients with bilateral arthroplasties with low HHS (HR, 0.96; p < 0.001) and high cobalt levels (HR, 1.02; p < 0.001) were at increased risk for revision. Moderate-to-severe ALTRs were identified in 48 of the 133 hips with MARS MRI (36%), 17 of which were in females (30% of females) and 31 in males (40% of males). The only variables found to be associated with the presence of moderate-to-severe ALTR were abduction angle (HR, 0.92; p = 0.004) and Corail AMT stem type (HR, 2.31; p = 0.012). Female gender did not influence the risk of revision or ALTR. Chromium concentrations were greater in female patients than males, while cobalt levels were similar between genders. Males reported higher HHS, EQ-5D and UCLA scores than females. Discussion and Conclusion. Both males and females with MoM THA implants should be followed with equal vigilance as gender does not appear to be associated with poor outcomes, such as revision surgery and presence of ALTR

Background. Reasons for revision of metal-on-metal hip resurfacing arthroplasty (MoMHRA) have evolved with improving surgical experience and techniques. Early revisions were often due to fracture of the femoral neck while later revisions are associated with loosening and/or adverse local tissue reactions (ALTR) to wear debris. In some studies, revisions of MoMHRA with ALTR have been complicated by an increased risk of rerevision and poor outcome. The purpose of this study was to investigate the causes of failure and to identify factors that improve outcome following revision of a failed HRA. Methods. From 2001 to May 2015, 180 consecutive HRA revisions were performed in 172 patients. Ninety-nine primary surgeries were done at a HRA specialist centre (99/4211, revision rate: 2.4%), 81 elsewhere. Eight different HRA designs were revised mainly in females (60%). Components’ orientation was measured from radiographs using EBRA. Ion levels were used as a diagnostic tool since 2006 (n=153). Harris-Hip-Score (HHS) was obtained prerevision and at latest follow-up. The initial experience of the first 42 cases (Initial Group) was compared to cases 43–180 (Later Group). Patients of the Later group were noted to have less soft tissue damage, had significantly bigger THA heads implanted at surgery, were educated of the increased complication risk and some wore an abduction brace for 6 weeks. Results. All patients presented with some pain/discomfort. Mean time to revision was 38 months (0–160). Eight HRAs were revised for fracture and 8 for infection. The most common reason for revision was component malpositioning (acetabular 48%, excessive abduction and/or anteversion; femoral 10%) usually associated with high metal ions (62%). The most common intra-operative finding was ALTR (48%) followed by metallosis (36%) and impingement (29%). Metal sensitivity was suspected in 8 patients (6F/2M). There were gender-specific differences in component sizes and causes of failure, with a higher incidence of component malpositioning, osteolysis and elevated metal ions in women. Time to revision in patients with high metal ion levels was shorter with the ASR (21 months, SD:10) in comparison to the BHR (38 months, SD: 25) (p=0.05). For the whole cohort, HHS significantly improved post revision (93, 42–100) (p<0.001). Fourteen complications (9 dislocations; 5 infections) and 9 re-revisions occurred. Outcome {HHSpost-op (p=0.04), complication and re-revision rates (p=0.005)} was significantly better in the Later Group compared to the Initial group. The incidence of complications/re-revisions significantly reduced since the introduction of metal ions (p=0.004). The presence of ALTR did not significantly affect outcome (p=0.65). However, patients with ALTR in the Later group (n=51) had significant reduced complication(p=0.005) and re-revision(p=0.016) rates in comparison to those in the Initial Group. Conclusion. Component malpositioning is the most common cause of HRA failure. Metal ion measurements are an excellent tool to detect wear at an early stage. The revision analysis highlights the importance of surgical experience, indications and prosthesis design. Use of ion levels, big THA-heads and patient education/compliance were identified as factors improving outcome following HRA revision. Patients with soft tissue reactions can have good outcome if operated prior to extensive soft tissue destruction

Introduction. There have been increased concerns with trunnion fretting and corrosion and adverse local tissue reactions (ALTR) in total hip arthroplasty. We report on 11 catastrophic trunnion failures associated with severe ALTR requiring urgent revision arthroplasty. Methods. We retrospectively reviewed 10 patients with gross trunnion failure (n=11) and an additional 3 patients with impending trunnion failure. Results. All patients presented to the emergency department with severe pain, an inability to bear weight, and dramatic radiographs demonstrating implant failure. Patients were an average of 7.8 years from the initial index procedure. Implants were a cementless component with metal on polyethylene bearing from a single manufacturer with a 36mm femoral head size and a range of extended offset of 2.5 to 5.5 and neck length of +0 (n=1), +5 (n=5), and +10 (n=5). The implant was used during a limited time (2.5 years) by single surgeon in our practice using a posterior approach, with the last implant placed 7 years ago. Prior to revision, serum cobalt levels were elevated, typically more than chromium levels. Radiographs demonstrated failure of the implant with a dissociation of the head from the taper and large radiolucent fluid collections from the metal debris (Fig 1). Intraoperative findings and magnetic resonance imaging confirmed a diagnosis of ALTR with loss of abductors, and severe material loss from the taper (Fig 2). We estimate a conservative incidence of catastrophic trunnion failure in our series to be 2.2% (n = 636 total implanted). A femoral revision with a modular Wagner stem was performed, and when necessary the acetabulum was revised secondary to destruction of the locking mechanism from mechanical wear. Discussion and Conclusion. ALTR can occur in patients with catastrophic failure of their trunnion. Radiographs are dramatic. Serum metal ion levels and magnetic resonance imaging is comparable to adverse local tissue reaction in metal on metal bearing surfaces, corrosion at the head neck taper, and corrosion of dual modular taper stems. The initiating events leading to this mechanism of trunnion failure is unknown. We observed trunnion failure at large head sizes and at increased femoral head offsets. Other groups have reported an association of trunnion failure at increased neck length and head size with a variety of manufacturers. Based on our experience, we have been able to identify impending failure based on subtle radiographic criteria and elevated metal ion levels. A failure rate of 2% at 7.8 years is non-trivial. Impending trunnion failure should be considered as a possible diagnosis in a painful total hip arthroplasty with unknown etiology. Serum metal ion levels and magnetic resonance imaging should be obtained as part of the initial evaluation

Introduction. Wear debris and metal ions originating from metal on metal hip replacements have been widely shown to recruit and activate macrophages. These cells secrete chemokines and pro-inflammatory cytokines that lead to an adverse local tissue reaction (ALTR), frequently requiring early revision. The mechanism for this response is still poorly understood. It is well documented that cobalt gives rise to apoptosis, necrosis and reactive oxygen species generation. Additionally, cobalt stimulates T cell migration, although the effect on macrophage motility remains unknown. This study tests the hypothesis that cobalt ions and nanoparticles affect macrophage migration stimulating an ALTR. Methods. This study used Co. 2+. ions (200µM) and cobalt nanoparticles (CoNPs, 100µM, 2–60nm diameter). PMA differentiation of the U937 cell line was used as macrophage-like cells. The effect of cobalt on macrophage migration was investigated by live cell imaging. After 12 hours of each treatment, timelapse images of 20 cells were collected over a 6 hour period with images captured every 5 min. Migration of individual cells was tracked in 2D using ImageJ software. The transwell migration assay was also applied to study the effect of cobalt on macrophage directional migration. U937 cells in serum free medium were added to the upper chamber of a 8µm pore size Transwell insert in the presence of cobalt, whilst the lower chamber was filled with medium plus 10% FBS. After 6 hours treatment, cells remaining on the membrane were fixed, stained with crystal violet and counted. Cellular F-actin and podosomes were visualized by labeling with TRITCconjugated phalloidin and anti-vinculin antibody after 12 hours of cobalt exposure (Co. 2+. and CoNPs). Results. Cells incubated with cobalt ions and nanoparticles showed a substantial reduction in cell migration compared with control cells. The total migration path length of cells treated with Co. 2+. (362.4±96.6µm) and CoNPs (217.3±128.1µm) were significantly shorter than those for untreated cells (801.1±198.3µm). The ability of macrophages to migrate through the transwell membrane was significantly impaired by pre-treatment with cobalt, with 16±4 and 18± migrated cells/field for Co. 2+. and CoNPs respectively with the control at 42±7 migrated cells/field. In addition, cobalt influenced macrophage morphology and actin cytoskeletal organization with a dramatic increase in the presence of intracellular podosome-type adhesions structure. Discussion. Co. 2+. ions and nanoparticles dramatically inhibited the migration of U937 macrophages in contrast to the enhanced migration reported for T cells. We propose that macrophages recruited into the area of CoCr implants would lose their responsiveness to migration signals and be retained in situ due to cobalt-induced cytoskeleton rearrangement. This enhanced macrophage accumulation and cobalt-induced formation of podosomes may therefore represent a mechanism through which cobalt wear debris and metal ions from joint prostheses exacerbate the ALTR leading to revision surgery

INTRODUCTION. Metal-on-metal hip resurfacing (MoMHRA) requires a new standardized radiographic evaluation protocol. Evaluation of the acetabular component is similar to total hip arthroplasty but the femoral component requires different criteria since there is no component in the femoral canal and the metallic femoral implant overlies the junctions between bone-cement and cement-prosthesis. Lucencies around the metaphyseal HRA femoral stem can be described with the femoral zonal system into 3 peg-zones (Amstutz' et al) but this doesn't account for bony changes of the femoral neck away from the stem. This study proposes a new femoral zonal system for radiographic HRA assessment. We tested the efficacy of radiographs in identifying a problem by reviewing 711 radiographs of resurfaced hips and correlating radiographic features to outcome. METHODS. 611 in-situ HRA (one surgeon) with minimum two radiographs at >12 months postoperatively and 100 revised HRA (55 referred) were assessed for component positioning, reactive lines±cortical thickening±cancellous condensation (borderline) and lucent lines±osteolysis±bone resorption (sinister). Findings around the acetabular implant were classified in six zones: Zones I-III equally distributed acetabular zones (DeLee-Charnley); Zone IV, V and VI situated in the iliac, pubic and ischial bone respectively. Findings around the proximal femur are defined with a new zonal system, dividing the implant-cement-bone interfaces and the femoral neck into 7 areas. Zones 1,7 at the superior and inferior part of the femoral neck-head, zones 2,3 at the proximal and distal halves of the superior aspect of the stem, zone 4 at the tip, zones 5,6 at the distal and proximal inferior aspects of the stem). Radiological findings and zones were correlated with gender, size, survival, Harris Hip Scores (HHS), metal ions, and adverse soft tissue reactions (ALTR). RESULTS. Radiological changes were found in 260 cases (36.7%), 151 sinister (21.2%) and 110 borderline (15.5%). 82% of revisions had sinister findings versus 11.3% of in-situ HRA (p<0.001). Of the 52 revised cases with ALTR, 2 had normal Xrays, 3 borderline and 47 sinister (90.4%). Females had a higher incidence of sinister findings (28.9%) compared to males (16.6%)(p<0.001). Sinister radiographs were significantly associated with lower HHS (mean 85 versus 98)(p<0.001), smaller sizes (median 48 versus 50)(p<0.001) and ASR design (58.8%). Metal ions were significantly higher with sinister (mean Cr:17.6μg/l-Co:17.8μg/l)(p<0.001) and borderline findings (mean Cr:3.34μg/l-Co:3.01μg/l)(p<0.01) compared to normal radiographs (mean Cr:2.61μg/l-Co:2.26μg/l). A higher number of pathological zones was correlated with risk of revision(p=0.006), ALTR(p<0.001), female gender(p<0.001), smaller size(p<0.001), and lower HHS(p<0.001). Pathological findings in . 3. 4 zones had a sensitivity of 50% and specificity of 94.2% (AUC=0.898) in detecting hips with ALTR (risk ratio=19.6). DISCUSSION. Radiographic assessment of HRA provides valuable information: 82% of problematic hips had sinister changes and 90.4% of cases with proven ALTR. In order to accurately evaluate progressive radiographic changes in HRA, specific zones have been established around the HRA femoral component. There was a high correlation between radiographic findings, clinical outcome and metal in levels. However, the absence of sinister radiologic findings does not eliminate a problematic HRA and further investigations (ion levels, imaging) would be indicated in symptomatic patients

Background. Large head metal on metal total hip arthroplasty MOM THA have been consistently shown substantial improvement in wear performance compared with metal on polyethylene articulations. Large diameter femoral heads theoretically can reduce dislocation risk by increasing range of motion before impingement, increasing prosthetic jump distance. However, early failure associated with adverse local tissue reactions (ALTRs) to metal debris is an emerging problem after MOM THA. The purpose of this study was to evaluate mid-term results of MOM THA. Materials and Methods. Twenty-five patients, 28 hips were included in this study. The average age of the patients at the time of surgery was 66.9 years. Three patients were men and 22 were women. MOM THAs were performed using 28 PINNACLE Cup system (DepPuy) (C-STEM: 23, S-ROM: 5) with posterior approach and head size of 36mm. Twenty-five primary THAs due to osteoarthritis in 22 cases and rheumatoid arthritis (RA) in one, and two revisions due to recurrent dislocation THA patients, were performed. The average follow up was 56.7 months. Evaluation items are JOA score, cup anteversion /lateral opening angle, and complications. Indication of the system were applied for patients with high risk of dislocation such as recurrent dislocation in primary and/or THAs, posterior pelvic tilt, elderly, RA and mental disorders. Results. The average JOA score improved from 48.3 (range: 26–77) preoperatively to 88.3 (range: 55–100) postoperatively. The average cup anteversion was 21.7 degrees (range: 2–38) and average lateral opening was 45.5 degrees (range: 37–60). Three patients (12%) developed dislocation. Two patients (8%) required reoperations from the deep infection. One female patient (4%) remained hip pain and was suspected pseudotumor / ALTR, which was confirmed by computed tomography and magnetic resonance imaging. Conclusion. Large femoral head MOM THA was useful for patients with recurrent dislocation in revision THA. However, three patients developed dislocation in primary THAs (12% of primary cases), which suggested that the more accurate placement of the acetabular cup is important even in the large diameter cup. Although only one case (4%) revealed ALTR, however, continuous careful follow-up would be necessary in the MOM system

Since the market withdrawal of the ASR hip resurfacing in August 2010 because of a higher than expected revision rate as reported in the Australian Joint Replacement Registry (AOAJRR), metal-on-metal hip resurfacing arthroplasty (MoMHRA) has become a controversial procedure for hip replacement. Failures related to destructive adverse local tissue reactions (ALTR) to metal wear debris have further discredited MoMHRA. Longer term series from experienced resurfacing specialists, however, demonstrate good outcomes with excellent 10- to 15-year survivorship in young and active men. Besides, all hip replacement registries report significantly worse survivorship of total hip arthroplasty (THA) in patients under 50 compared to older ages. The triad of a well-designed device, implanted accurately, in the correct patient has never been more critical than with MoMHRA implants. The surgical objectives of MoMHRA 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. Cobb reported that patients with MoMHRA were able to walk faster and with more normal stride length than patients with well performing hip replacements. They also show that function following hip replacement is very good, with high satisfaction rates, but the use of a patient centered outcome measure (PCOM), and objective measures of function reveal substantial inferiority of THA over MoMHRA in two well-matched groups. When coupled with the very strong data regarding life expectancy and infection, this functional data makes a compelling case for the use of resurfacing in active adults. Recent studies show a possible increase in life expectancy with MoMHRA. Compared with uncemented and cemented total hip replacements, Birmingham hip resurfacing has a significantly lower risk of death in men of all ages. McMinn's investigations additionally suggest a potentially higher mortality rate with cemented total hip replacements. These results have now been confirmed by other centers as well, and confirm that those undergoing MoMHRA have reduced mortality in the long term (up to 10 years) compared with those undergoing THA and that this difference persisted after extensive adjustment for confounding factors. Early revisions were often due to fracture of the femoral neck while later revisions are associated with loosening and/or ALTR to wear debris. In some studies, revisions of MoMHRA with ALTR have been complicated by an increased risk of re-revision and poor outcome. Component malpositioning is the most common cause of MoMHRA failure. Metal ion measurements are an excellent tool to detect wear at an early stage. The revision analysis highlights the importance of surgical experience, indications and prosthesis design. Use of ion levels, big THA-heads and patient education/compliance were identified as factors improving outcome following MoMHRA revision. Today's MoMHRA is conservative to the bone. It is the first implant that proves decrease of wear in time, disappearance of wear in longer term with a possible life time survival of the implant, this unrelated to the activity of the patient. If following an international consensus, the right implant is used, with a perfect technique in the right patient, all benefits exceed the problems described in the past

Distal neck modularity places a modular connection at a mechanically critical location. However, this is also the location that confers perhaps the greatest clinical utility. Assessment of femoral anteversion in 342 of our THR patients by CT showed a range from −24 to 61 degrees. The use of monoblock stems in some of these deformed femurs therefore must result in a failure to appropriately reconstruct the hip and have increased risks of impingement, instability, accelerated bearing wear or fracture, and adverse local tissue reaction (ATLR). However, the risks of failing to properly reconstruct the hip without neck modularity must be weighed against the additional risks introduced by neck modularity. There are several critical design, material, and technique variables that are directly associated with higher or lower incidences of problems associated with modular neck femoral components. These include modular neck length, design and material of both parts including the junction design, wall thickness of the receiving junction, assembly force, and bearing diameter and material. With regard to stem design and material, it has been clearly shown that the incidence of titanium neck fractures is higher in stems with a thinner wall-thickness of the receiving junction than in stems with a thicker wall-thickness. Moreover, titanium necks have been largely replaced with CoCr necks with significantly higher yield and fatigue strength. It remains to be seen if the introduction of CoCr necks will decrease or increase the risks associated with distal neck modularity. With respect to titanium necks, our experience has shown no adverse local tissue reaction, no fractures of short necks (0 of 370) and a 0.34% incidence of fractures in long necks (2/580) at 3 to 8 years following surgery. This lower incidence of neck fracture compared to other reports may relate to the relatively more rigid stem and thicker wall of the junction receiving the neck compared to other stems. With respect to CoCr modular necks, one device that mated the CoCr modular neck with a beta-titanium alloy femoral component has been shown to have a high incidence of ALTR and has been recalled. While the CoCr on Conventional Titanium Alloy modular neck experience has had a statistically significantly lower incidence of problems, we believe that we have identified two cases of ALTR. If that is the case, the CoCr neck experience may well have a higher incidence of problems that the Ti neck experience. In summary, placing a modular connection at the stem-neck junction has great clinical utility but this is a very design sensitive location. There are risks associated with the use of non-modular neck components that are incapable of properly reconstructing the spectrum of pathology that presents. This failure can lead to instability, impingement, and polyethylene fracture. Yet, the use of titanium modular necks has a small risk of component fracture while the use of cobalt-chrome modular necks may have a higher risk of adverse local tissue reaction. While the existence of a modular neck may offer great advantages at the time of primary reconstruction and of future revision, currently the risk/benefit for the use of these components is strongest in patients with more significant anatomical abnormalities or more complex revision settings

Introduction. Metallic resurfacing systems have been widely used until pseudotumors and ALTR have been clinically found and related to excessive wear of these metal-on-metal hip systems. Hence, surgeons widely abandoned the use of resurfacing systems. Meanwhile, there is a ceramic on ceramic (CoC) resurfacing system (Embody, London, UK) made of zirconia toughened alumina (BIOLOX. ®. delta, CeramTec, Plochingen, Germany) in a clinical safety study. Even though conventional CoC hip systems are known for their excellent wear behavior, it has to be ensured that intraoperative and in-vivo deformations of the ceramic acetabular cup do not infringe the proper functionality of the system. The method of determining the minimum clearance of such a system will be presented here. Materials and Methods. Combined experimental and numerical results were used to determine the deformation of the ceramic shell. In a cadaver lab, the resulting deformations after impaction of generic metal shells have been measured, see e.g. [1] for the method of measurement. The maximum deformation has been chosen for further calculation. Additionally, the stiffness of both generic metal and ceramic shells has been measured using ISO 7206–12. The deformation of the ceramic shells were then calculated by the equation. where u. c. and u. m. are the deformations of the ceramic and the metal shell, respectively, and K. m. and K. c. are the respective stiffnesses. Additionally, in a finite element simulation, the resulting deformation of the ceramic shell under in-vivo conditions was calculated and superposed with u. c. The resulting deformation was used as the minimum value of the clearance for the ceramic resurfacing system. Results. The average value of the maximum deformation of the 8 generic metal shells was 177 µm (StD. 68 µm). Using the stiffness values for the ceramic and the metal shells, a maximum deformation for the ceramic shells (with the smallest and the largest outer diameter) were calculated to 56 µm and 74 µm, respectively. The superposition with the results from the FE studies led to deformation values of 69 µm (smallest shell) and 87 µm (largest shell), respectively. These values were chosen as the minimum values for the realization of the minimum clearance. Discussion. The above described minimum clearance results from a worst-case scenario for the long-term deformation of the ceramic shells. The values from the experimental measurements were taken ten minutes after impaction in the cadaveric hips, when first relaxation already took place. Any other bone remodeling in the long-term, leading to further relaxation of the ceramic shell, has not been taken into account. The maximum deformations resulting from the numerical investigations have been superposed to the experimental values, assuming that both maximum deformations are acting in the same direction. In reality, this is most likely not the case because the line-of-action of the in-vivo forces acting on the hip are not collinear with the direction where the maximum deformation during intra-operative impaction takes place. Additionally, the experimentally chosen underreaming (1 mm) can also be considered as a worst-case. Hence, the calculated minimum clearances are representing the maximal deformation that in the long-term may take place in-vivo

The AAOS clinical practice guideline for diagnosis of periprosthetic joint infection (PJI) and the MSIS definition of PJI were both “game changers” in terms of diagnosing PJI and the reporting of outcomes for research. However, the introduction of new diagnostic modalities, including biomarkers, prompted a re-look at the diagnostic criteria for PJI. Further there was a desire to develop an evidence-based, validated algorithm for the diagnosis of PJI. This multi-institutional study led by Dr. Jay Parvizi examined revision total joint arthroplasty patients from three academic institutions. For development of the algorithm, infected and aseptic cohorts were defined. PJI cases were defined using only the major criteria from the Musculoskeletal Infection Society (MSIS) definition (n=684). Aseptic cases underwent revision for a non-infective indication and did not show evidence of PJI or undergo a reoperation for any reason within 2 years (n=820). Risk factors, clinical findings, serum and synovial markers as well as intraoperative findings were assessed. A stepwise approach using random forest analysis and multivariate regression was used to generate relative weights for each of the various variables assessed at each stage to create an algorithm for diagnosing PJI using the 3 most important tests from each step. The algorithm was formally validated on a separate cohort of 422 patients, 222 who were treated with a 2-stage exchange for PJI who subsequently failed secondary to PJI within one year and 200 patients who underwent revision surgery for an aseptic diagnosis and had no evidence of PJI within two years and did not undergo a reoperation for any reason. The first step in evaluating PJI should include a physical examination to identify a sinus tract, followed by serum testing for C-reactive protein (cut-off value 1mg/dl), D-dimer (cut-off value 860ng/mL) and/or erythrocyte sedimentation rate (cut-off value 30mm/hr) in that order of importance. If at least one of these are elevated, or if there is a high clinical suspicion, joint aspiration should be performed, sending the fluid obtained for a synovial fluid white blood-cell (cut-off value 3,000 wbc/uL) or leukocyte esterase strip testing, polymorphonuclear percentage (cut-off value 80%) and culture. Alpha defensin did not show added benefit as a routine diagnostic test. Major diagnostic criteria are the same whereby the presence of a sinus tract or (2) positive cultures showing the same organism defines PJI. Special care should be taken in cases of ALTR (failed metal-on-metal bearing), crystalline deposition disease, inflammatory arthritis flares or slow growing organisms. In the rare cases where no fluid is obtained at the time of an attempted aspiration and revision surgery is not planned, then this is the rare scenario where nuclear imaging (my preference is an indium labeled white blood cell scan) or a biopsy can be performed. The updated definition of PJI demonstrated a higher sensitivity of 97.7% when compared to the MSIS criteria (79.3%) and the ICM definition (86.9%), with a similar specificity of 99.5%. However, just over 2% of patients examined do fall into the “inconclusive” category. The proposed diagnostic algorithm demonstrated a high overall sensitivity (96.9%) and specificity (99.5%)

Metal-on-metal bearing surfaces were reintroduced to take advantage of the reduction in volumetric wear afforded by these bearings and reduce the complications of osteolysis and aseptic loosening. In addition, metal-on-metal hip resurfacing and many metal-on-metal total hip replacement systems employed large diameter femoral heads, thereby reducing the risk of dislocations. Unfortunately, many metal-on-metal systems demonstrated poor survivorship and were associated with adverse local tissue reactions (ALTRs) related to metal debris generated from the bearings and/or modular connections. Careful clinical surveillance of patients with metal-on-metal bearings is warranted to identify patients with ALTR at an early stage in order to intervene prior to the development of extensive peri-articular soft tissue damage. Monitoring may include serum or whole blood metal levels and metal artifact reduction sequence magnetic resonance imaging (MARS-MRI) depending on the patient's signs and symptoms and the track record of the implanted device. While there currently is a lack of high quality evidence-based guidelines on the management of patients with either symptomatic or asymptomatic metal-on-metal total hip replacements, professional organizations have issued consensus-based algorithms to guide the practitioner in management. Ultimately, the decision for revision surgery should not be based on a single diagnostic test but on the entire clinical scenario

Properly designed ceramic-on-ceramic total hip arthroplasty has consistently shown excellent clinical outcomes without the problems associated with crosslinked polyethylene bearings such as liner dissociation, debris associated osteolysis, polyethylene fracture, clinically measurable wear, and taper-corrosion associated adverse tissue reaction when metal heads are used. The recognition of these results has been affected by the confusion with the poorer results of designs with elevated metal rims especially when coupled with the use of femoral components made of beta-titanium alloys. Our clinical experience, now at 18 years, with flush mounted liners and Ti-Al6-V4 stem and cup alloy demonstrate consistently excellent outcomes without osteolysis or ALTR. Ceramic-Ceramic THA remains the gold standard for the young active patient

Abductor deficiency after THA can result from proximal femoral bone loss, trochanteric avulsion, muscle destruction associated with infection, pseudotumor, ALTR to metal debris, or other causes. Whiteside has described a transfer of the tensor muscle and anterior gluteus maximus to the greater trochanter for treatment of absent abductors after THA. Transposition of the tensor muscle requires raising an anterior soft tissue flap to the lever of the interval between the tensor muscle and sartorius, which is the same interval used in an anterior approach to the hip. The muscle is transected distally and transposed posteriorly to attach to the proximal femur. This can result in soft tissue redundancy between the posterior tensor muscle and anterior gluteus maximus. This interval is separated and the anterior gluteus maximis also attached to the proximal femur. Relatively large unconstrained (36 mm heads) were not found to be effective in controlling dislocation in patients with abductor deficiency. In our practice, 11 patients with abductor deficiency were treated with Whiteside's tensor muscle transfer and an unconstrained large diameter femoral head. The mean pre-operative abductor strength was 2.2 and improved to 3.2 post-operatively. One patient sustained a dislocation four weeks after surgery which was treated with open reduction. All of the other hips have remained stable. The combination of a large head and tensor muscle transposition may be a viable alternative to use of a fully constrained component in patients with deficient abductors after THA