Purpose. Our primary purpose was to study the rate of occurrence and the natural course of pseudotumors in patients who had not required a revision procedure. Our secondary purpose was to see if there is a relationship between serum metal ion analysis and clinical symptoms with metal-on-metal (MOM) hip arthroplasty. Patients and Methods. We used repeated metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) to screen 17 unrevised hips (mean patient age 63.0 years, 43 to 83 years) with pseudotumors and 26 hips (mean patient age 63.2 years, 47 to 83 years) without pseudotumors. Patients with 17 MOM, 17 ceramic-on-polyethylene (COP) and 7 ceramic on ceramic (COC) who had undergone repeated MARS MRI were evaluated with or without any symptoms. We utilized MARS MRI to score the type of pseudotumors using the Hart method. The mean post-operative time to the first MARS MRI scan was 30.0 months (8 to 96), and the time between the first and the second MARS MRI scan was eleven months (6 to 12). Serum Cr and Co ion measurements were undertaken at the time of both MRIs and analyzed only after MOM total hip arthroplasty. Results. The rate of occurrence of pseudotumors was 47.5% with MOM, 33.0% with COP, and 25.0% with COC. There was a significant difference in number of abnormalities between MOM and COP and COC bearing. At the second MRI scan, the grade of severity of pseudotumors had not changed in 40 hips. Two new asymptomatic pseudotumors (MOM:1 case, COP:1 case) were detected and one pseudotumor was downgraded. In 17 patients with pseudotumors, two cases (11.7%) were symptomatic and in 26 patients without pseudotumors, 4 cases (15.3%) were symptomatic, with no significance between the two groups. In 17 patients with MOM cases, only two cases with pseudotumors were symptomatic, and both cases showed elevated blood metal ion levels. However, in these series 13 cases (6 with pseudotumors and 7 without pseudotumors) (76.4%) were overtaken baseline. So there was no significance in terms of metal ion levels with or without pseudotumors. Discussion. Overall, there was the same tendency in terms of occurrence of pseudotumors compared with our previous studies regarding MARS MRI. Pseudotumors can occur in patients with COP and COC bearing secondary to corrosion at modular femoral head neck taper. This feature is similar to pseudotumors seen in patients with a MOM bearing. In general, the characteristics of the pseudotumors hardly changed. Repeated MARS MRI scans within one year after total hip arthroplasty showed little or no variation. On the other hand, in 26 patients without pseudotumors, two new asymptomatic pseudotumors were detected. Moreover, there was no clinically useful association among symptoms, serological markers and the severity of MR findings. In conclusion, MRI abnormalities are present in normal asymptomatic THA and, regardless of the type of bearing surface, the occurrence of pseudotumors suggests that it might originate from head neck junction and indicate subclinical disease

PURPOSE:. Wright Medical has a long history of modular neck hip implants but had fracture issues with the original titanium necks. They subsequently changed to chrome cobalt modular necks. Direct contact between these dissimilar metal parts in the modular femoral component brings into consideration the possibility of similar adverse reactions of metal-on-metal articulations that have been previously described in other designs. METHODS:. A retrospective review of 10 patients with Wright Medical chrome cobalt modular necks who were evaluated with chromium and cobalt metal ion levels as well as Metal Artifact Reduction Sequence (MARS) MRI's was performed. Pseudotumors were classified by MRI based on wall thickness, T1/T2 signal, shape, and location and given a corresponding type of I, II, or III. For each patient, symptoms or lack thereof were recorded, and time since surgery noted. RESULTS:. Of 10 patients tested, 9 were symptomatic, and 1 was asymptomatic. The patient that was asymptomatic at last clinical visit at 14 months post-op while symptomatic patients averaged 18 months since initial surgery before symptoms began. Those with metal-poly articulation had an average cobalt level of 1.6, ceramic-ceramic articulation had level of <1, and metal-on-metal had level of 2.9. Five patients had pseudotumor by MRI (2 type I, 1 type II, and 2 type III pseudotumors). CONCLUSION:. It appears that an unintended consequence of changing from titanium to chrome cobalt modular neck may be occurring secondary to corrosion at neck-stem junction. SIGNIFICANCE: This reaction does not appear to be design-specific as these findings are similar to our findings in Stryker Rejuvenate stems. Surgeons evaluating patients with these and other similar stems should be aware of this complication and consider ion testing and MARS MRI

Introduction. Metal Artefact Reduction Sequence (MARS) MRI is being increasingly used to detect soft tissue inflammatory reactions surrounding metal-on-metal hip replacements. The UK MHRA safety alert announced in April 2010 recommended cross-sectional imaging such as MRI for all patients with painful MOM hips. The terms used to describe the findings include bursae, cystic lesions and solid masses. A recently used term, pseudotumour, incorporates all of these lesions. We aimed to correlate the pattern of abnormalities on MRI with clinical symptoms. Method. Following our experience with over 160 MARS MRI scans of patients with MOM hips we recognized patterns of lesions according to their: wall thickness, T1/T2 signal, shape, and location. We categorised the 79 lesions from 159 MARS MRI scans of into our novel classification scheme of 1, 2a, 2b and 3. There were two groups of patients: well functioning and painful. Results. We found a surprisingly high prevalence of lesions on MRI scan in the well functioning group (11 out 23, 48%) when compared to the painful group (79 out of 137, 57%). However, there were a significantly greater number of grade 1 lesions in the well functioning group. We suggest that these are post-surgical changes and should not be confused with pathological, tissue destroying lesions. Discussion. This is the largest ever study of patients with MARS MRI scans of MOM hips. It is the first to use a classification system and the first to compare well functioning with painful hips. We are now able to provide radiologists and surgeons with clinical interpretation of a lesion on MRI scan. Our classification system will provide useful information on both symptomatic and asymptomatic patients. Longitudinal follow up of these patients will provide the final validation

The prevalence of pseudotumours in patients with large-head metal-on-metal (MOM) THA has been the subject of implant recalls and warnings from various regulatory agencies. To date, there is no consensus on whether ultrasound or MRI is superior for the detection and following the progression of pseudotumours. Ultrasound is relatively cheap but can be operator dependent. MARS MRI has the advantage of excellent visibility of the soft tissue. However, MRI comes at a marked increase cost and takes about twice as long to perform. At our institution, we prospectively compared ultrasound to MRI for pseudotumour detection in an asymptomatic cohort of patients with MOM THAs. We enrolled 40 patients with large-head MOM THAs in the study. The mean age was 54 years (range, 34–76 years). The mean time from surgery was 54 months (range, 40–81 months). There were 28 men and 12 women. All patients underwent ultrasound and MRI using slice encoding for metal artifact correction. The gold standard was defined as follows: if both ultrasound and MRI agreed, this was interpreted as concordant and the result was considered accurate. Ultrasound and MRI agreed in 37 of 40 patients (93%). The prevalence of pseudotumours was 31% (12 of 39) in our cohort. Twenty-three of 39 patients (59%) had completely normal tests and four (10%) had simple fluid collections. Ultrasound had a sensitivity of 100% and specificity of 96% while MRI had a sensitivity of 92% and specificity of 100%. Conclusions: A negative ultrasound rules out pseudotumour in asymptomatic patients as this test is 100% sensitive. Given its lower cost, we recommend ultrasound as the initial screening tool for pseudotumours. More recently, Kwon et al have compared ultrasound to MARS MRI for following the progression of pseudotumours. They found a strong agreement between the 2 modalities for assessing change in size and consistency of pseudotumours

Introduction. The MHRA guidelines for metal on metal (MOM) suggest cobalt and chromium levels of more than 7ppb as potential for soft tissue reaction. However, in some patients soft tissue reaction is seen even in the presence of normal serum metal ions levels. Methods. A prospective review of all patients who had metal-on-metal hip arthroplasty was done. Patients who had both serum metal ion levels and MARS MRI scan were included in this study. Results. There were 574 patients with 319 females and 255 males. 240 patients had both MARS MRI scan and serum metal ions. Fifty nine (24.5%) patients with normal metal ions had metallosis/pseudo tumour on MRI scans, and 17 (7%) patients with increased metal ions had normal MRI scans. Conclusion. This study confirms that there is poor correlation between serum metal ions and soft tissue reaction. Nearly a quarter of patients with normal serum metal ions had evidence of metallosis on MRI scan. Clinicians should be aware of the potential for soft tissue reaction even in the presence of normal metal ions. Hence, consideration should be given to further imaging where appropriate, to ensure early metallosis is picked up and further complications of pseudo tumour prevented

All patients with a MOM THR implanted at our unit were recalled for clinical examination, Oxford hip score, radiographs, MARS MRI and cobalt/chromium ion levels. Patients were sub-classified, determining further follow up: a regular screening programme or referral to a revision arthroplasty surgeon. We identified 299 MOM THR's. 59 patients reported a recent deterioration in symptoms. 67 had an abnormal x-ray. 232 hips underwent MARS MRI: 66 showed mild MOM disease, 31 moderate MOM disease, 17 severe MOM disease. 117 had a substantial fluid collection around the hip. Serum cobalt/chromium ions were raised in 135 patients. 46 had one or both above 7 ppb. 148 THR's were referred to a revision surgeon. 21 have been revised and 14 are awaiting revision. In total 64 hips have been revised. 13 were histologically proven ALVAL, 19 had clinical findings of ALVAL (not histologically confirmed), and 1 non-specific reaction to metal wear. 53 asymptomatic patients had evidence of soft tissue reaction on MRI and/or rising metal ions. Our screening programme identified asymptomatic patients with evidence of a suspicious reaction to their MOM THR. We recommend all patients with a MOM THR are fully screened for ARMD regardless of symptoms and metal ion levels

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

Articular cartilage has a limited regeneration capacity, and damage of cartilage often results in the onset of degenerative disease such as osteoarthritis (OA). MRI and CT imaging of cartilage and subchondral bone are becoming increasingly important in early detection and treatment of OA as well as for quantifying quality of tissue-engineered samples. Non-invasive CT scanners have been used to image cartilage tissue with the help of contrast agents. However, since only one energy source is available, imaging information of multiple soft and hard tissues is lost given that the overall x-ray attenuation is measured. Medipix All Resolution System (MARS) CT offers the possibility of applying more than one energy source. It is able to measure the energy of each photon individually and therefore determines the characteristics of attenuation. In this study, an ionic contrast agent (Hexabrix) was used to image the negatively charged extra-cellular matrix component, glycosaminoglycan (GAG), which is abundantly found in the middle and lower layers of healthy cartilage tissue. GAG distribution in the cartilage tissue could be imaged using an inverse relationship with Hexabrix signal (i.e. high signal represents low GAG content). Eight bovine cartilage-bone explants (3mm × 5mm) were incubated in 4 different Hexabrix concentrations ranging from 20% to 50% in PBS. Sections were imaged using the MARS scanner at high and low energies (13.32 keV and 30.84 keV). Images were pre-processed, reconstructed and colour-coded using different enhancement techniques and virtual experimental software. Histological (Safranin-O) staining and quantitative biochemical analysis of GAG content (DMMB dye assay) was performed to correlate GAG distribution and content with MARS-CT images. High resolution images of both cartilage and bone regions were obtained, with contrast enhanced CT of cartilage correlating well with histological staining. X-ray attenuation was high in regions poor in GAG content, whereas attenuation was low in GAG rich regions. Furthermore, there was a direct inverse correlation between Hexabrix signal and GAG content as measured in superficial (2.9 μg/mg) and middle/deep regions (10.6 μg/mg) in cartilage explants. It can be concluded that the MARS technique can be used to image GAG distribution and GAG content, and therefore could be used clinically to assess quality of healthy or osteoarthritic cartilage, as well as non-destructive imaging of GAG content in engineered tissues

Background:. Higher than expected revision rates have been observed in large bearing metal-on-metal total hip replacements. We have introduced a metal on metal hip screening clinic at our unit and report the results. Methods:. All patients who had a metal-on-metal total hip replacement implanted at our unit were recalled to clinic. Screening consisted of clinical examination, Oxford hip score, radiographs, MARS MRI and serum cobalt/chromium ion levels. MRI scans were graded (Norwich Classification) by a single consultant radiologist who was blinded to the history, examination, and metal levels. Patients were sub-classified into 6 groups, which determined further follow up and were either entered into a regular screening programme or referred to a revision arthroplasty surgeon for a decision on whether revision was required. Results:. A total of 278 patients were identified. Four patients had moved away, 2 refused follow-up and 1 patient had died. This left 271 patients in our cohort, having 299 metal-on-metal hip replacements with a M:F ratio of 1.5:1 and a mean age of 61.9 years (29–87). 59 (21.8%) patients complained of a recent deterioration in symptoms. Sixty seven (24.7%) patients had an abnormal xray appearance of their hip replacement (inclination >50 degrees, loosening, or migration of prosthesis). Of the 232 hips which underwent MARS MRI, 118 (50.9%) were group A (normal appearance), 66 (28.4%) C1 (mild MOM disease), 31 (13.4%) C2 (moderate MOM disease), and 17 (7.3%) C3 (severe MOM disease). One hundred and seventeen (38.9%) had a substantial fluid collection around the hip. Serum cobalt/chromium metal ions were raised in 135 patients (49.5%), 46 of which had one (8.8%) or both (8%) above 7 ppb (chromium >134 nmol/L, cobalt > 119 nmol/L). One hundred and forty nine patients (55%) remained under review in the MOM clinic and 122 (45%, 148 hip replacements) were referred to a revision surgeon for specialist opinion. Of these 21 hips (14.2%) have been revised and a further 14 hips (9.5%) are awaiting revision. In total 64 hips (21.3% of all large head metal on metal hips implanted in our unit) have been revised with a further 22 (7.3%) listed for revision. Of these, 13 were histologically proven to be an ALVAL reaction, 19 had the classic clinical findings of ALVAL (but not histologically confirmed), and 1 was a non-specific reaction to metal wear. 53 patients (19.4%, 56 hips) were completely asymptomatic but had evidence of ALVAL soft tissue reaction on MRI and/or rising metal ion levels – 9 of these hips have already been revised for ALVAL and 6 more listed for revision. Conclusions. Our screening programme has identified 53 (19.6%) asymptomatic patients who have evidence of a suspicious reaction to their metal-on-metal hip replacements. 16 (3%) of these have gone on to revision. We would recommend all patients with a metal-on-metal total hip replacement in situ are fully screened for ARMD regardless of symptoms and metal ion levels

Total knee arthroplasty (TKA) is one of the most common orthopaedic operations performed worldwide and it is largely successful in pain relief and functional recovery. However, when pain persists post-operatively the thorough evaluation must be instituted. Extra-articular causes of knee pain include; hip pathology, lumbar spine degenerative disease or radicular symptoms, focal neuropathy, vascular disease, and chronic regional pain syndrome. Intra-articular causes of knee pain: infection, crepitation/clunk, patella osteonecrosis, patella mal-tracking, soft tissue imbalance, malalignment, arthrofibrosis, component loosening, implant wear, ilio-tibial band irritation, and bursitis. Other causes of pain to rule out are component overhang with soft tissue irritation, recurrent hemarthrosis secondary to synovial impingement or entrapment, non-resurfaced patella, and metal sensitivity. A careful history may reveal previous knee surgeries with delayed healing or prolonged drainage, chronology of sign and symptoms, co-morbid medical conditions, jewel or metal sensitivity. Physical exam should help with specific signs in the operated knee. Targeted local anesthetic blocks are helpful and response to lumbar sympathetic blocks determines presence of CRPS. Lab tests are important: ESR, CRP, WBC, aspiration with manual cell count and diff, leucocyte esterase dipstick, RA titers, metal derm patch testing, nuclear scans, CT best for rotational malalignment, and MARS MRI. More recently patient satisfaction as an outcome measure has shown TKA results not satisfactory in 11- 18% of patients. A discordance of patient vs. surgeon satisfaction exists so the following factors may help improve this: correct patient selection, establishing and correlating surgeon-patient expectations, peri-operative optimization of patient co-morbidities to help avoid preventable complications, use of pre-operative and post-operative pathways. Satisfaction rates can best be improved by addressing the previous points with patients prior to TKA surgery

Uncemented metal-on-polyethylene total hip arthroplasties (THAs) have had a modular cobalt-chrome alloy head since their introduction in the early 1980's. Retrieval analysis studies and case reports in the early 1990's first reported corrosion between the femoral stem trunnion (usually titanium alloy) and cobalt-chrome alloy femoral head. However, then this condition seemed to disappear for about two decades? There are now numerous recent case series of this problem after metal-on-polyethylene THA, with a single taper or dual taper modular femoral component. Metal ion elevation, corrosion debris, and effusion are caused by mechanically assisted crevice corrosion (MACC). These patients present with diffuse hip pain, simulating trochanteric bursitis, iliopsoas tendinitis, or even deep infection. Trunnion corrosion, with adverse local tissue reaction, is a diagnosis of exclusion, after infection, loosening, or fracture. The initial lab tests recommended are: ESR, CRP, and serum cobalt and chromium ions. With a metal-on-polyethylene THA, a cobalt level > 1ppb is abnormal. Plain radiographs are usually negative, but may show calcar osteolysis or acetabular erosion or cyst. MARS MRI may be the best imaging study to confirm the diagnosis. Hip aspiration for culture and cell-count may be necessary. The operative treatment is empiric, with debridement, and head exchange with a ceramic head-titanium sleeve (or oxidised zirconium head) placed on the cleaned trunnion. The femoral component may have to be removed if there is “whole trunnion failure”. This usually relieves the symptoms, but the complication rate of this procedure may be high

TKA is one of the most common orthopaedic operations performed worldwide and it is largely successful in pain relief and functional recovery. However, when pain persists post-operatively the thorough evaluation must be instituted. Extra-articular causes of knee pain include; hip pathology, lumbar spine degenerative disease or radicular symptoms, focal neuropathy, vascular disease, and chronic regional pain syndrome. Intra-articular causes of knee pain: infection, crepitation/ clunk, patella osteonecrosis, patella mal-tracking, soft tissue imbalance, malalignment, arthrofibrosis, component loosening, implant wear, ilio-tibial band irritation, and bursitis. Other causes of pain to rule out are component overhang with soft tissue irritation, recurrent hemarthrosis secondary to synovial impingement or entrapment, non-resurfaced patella, and metal sensitivity. A careful history may reveal previous knee surgeries with delayed healing or prolonged drainage, chronology of sign and symptoms, co-morbid medical conditions, jewel or metal sensitivity. Physical exam should help with specific signs in the operated knee. Targeted local anesthetic blocks are helpful and response to lumbar sympathetic blocks determines presence of CRPS. Lab tests are important: ESR, CRP, WBC, aspiration with manual cell count and diff, leukocyte esterase dipstick, RA titers, metal derm patch testing, nuclear scans, CT best for rotational malalignment,, and MARS MRI. More recently patient satisfaction as an outcome measure has shown TKA results not satisfactory in 11 – 18% of patients. A discordance of patient vs. surgeon satisfaction exists so the following factors may help improve this: correct patient selection, establishing and correlating surgeon-patient expectations, peri-operative optimisation of patient comorbidities to help avoid preventable complications, use of pre- and post-operative pathways. Satisfaction rates can best be improved by addressing the previous points with patients prior to TKA surgery

Introduction. Mechanically assisted crevice corrosion (MACC) in metal-on-polyethylene (MOP) total hip arthroplasty (THA) is of concern, but its prevalence, etiology and natural history are incompletely understood. Methods. From January 2003 to December 2012, 1356 consecutive THA surgeries using a titanium stem, cobalt chromium alloy femoral head, highly crosslinked polyethylene and a tantalum or titanium acetabular shell were performed. Patients were followed at 1 year, and 5 year intervals for surveillance, but also seen earlier if they had symptoms. Any patient with osteolysis or unexplained pain underwent exam, radiographs, CBC, ESR and CRP, as well as serum cobalt (Co) and chromium (Cr) level. MARS MRI was performed if the Co level was > 1 ppb. Results. Symptomatic MACC was present in 39/1356 patients (2.9%). Yearly MACC prevalence ranged from 0 % (0/139, 2005) to 9.9 % (16/162, 2009). 22/39 (56%) patients have undergone revision surgery, and 17/39 (44%) have opted for ongoing surveillance. Of the surveillance patients, serial serum metal ion levels appear to increase over time. Time of symptoms is correlated with tissue necrosis at time of revision. Conclusions. The prevalence of MACC in MOP hips is higher in this cross-sectional study than previously reported. The highest prevalence was found in 2009 with this vendor. Based on how common this finding is in symptomatic patients from 2009, we may consider asking asymptomatic patients to obtain baseline serum ion levels. The goal of our ongoing research is to understand how to avoid permanent soft tissue loss from adverse local tissue reactions caused by MACC

It is a not so uncommon clinical scenario: well-fixed, well-aligned, balanced total knee arthroplasty with continued pain. However, radiographs also demonstrate an unresurfaced patella. The debate continues and the controversy remains as whether or not to routinely resurface the patella in total knee arthroplasty. In perhaps the most widely referenced article on the topic, the overall revision rates were no different between the resurfaced (9%) and the unresurfaced (12%) groups and thus their conclusion was that similar results can be obtained with and without resurfacing. However, a deeper look in to the data in this study shows that 4 times more knees in the unresurfaced group were revised for patellofemoral problems. A more recent study concluded that selectively not resurfacing the patella provided similar results when compared to routinely resurfacing. The study does emphasise however, that this conclusion depends greatly on femoral component design and operative diagnoses. This suggests that selective resurfacing with a so-called “patella friendly” femoral component in cases of tibio-femoral osteoarthritis, is a safe and effective strategy. Finally, registry data would support routine resurfacing with a 2.3 times higher relative risk of revision seen in the unresurfaced TKA. Regardless of which side of the debate one lies, the not so uncommon clinical scenario remains; what do we do with the painful TKA with an unresurfaced patella. Precise and accurate diagnosis of the etiology of a painful TKA can be very difficult, and there is likely a strong bias towards early revision with secondary patellar resurfacing in the painful TKA with an unresurfaced TKA. At first glance, secondary resurfacing is associated with relatively poor outcomes. Correia, et al. reported that only half the patients underwent revision TKA with secondary resurfacing had resolution of their complaints. Similarly, only 53% of patients in another series were satisfied with the procedure and pain relief. The conclusions that can be drawn from these studies and others are that either routine patellar resurfacing should be performed in all TKA or, perhaps more importantly, we need to better understand the etiology of pain in an otherwise well-aligned, well-balanced, well-fixed TKA. It is this author's contingency that the presence of an unresurfaced patella leads surgeons to reoperate earlier, without truly identifying the etiology of pain or dissatisfaction. This strong bias; basically there is something more that can be done, therefore we should do it, is the same bias that leads to early revision of partial knee arthroplasty. While very difficult, we as knee surgeons should not revise a partial knee or secondarily resurface a patella due to pain or dissatisfaction. Doing so, unfortunately, only works about half the time. The diagnostic algorithm for evaluating the painful, uresurfaced TKA includes routinely ruling out infection with serum markers and an aspiration. Pre-arthroplasty radiographs should be obtained to confirm suitability and severity of disease for an arthroplasty. An intra-articular diagnostic injection with Marcaine +/− corticosteroid should provide significant pain relief. MARS MRI may be beneficial to evaluate edema within the patella. Lastly, operative implant stickers to confirm implant manufacturer and type are critical as some implants perform less favorably with unresurfaced patellae. To date, no studies of secondary resurfacing describe the results of this, or similar, algorithms for defining patellofemoral problems in the unresurfaced TKA and therefore it is still difficult to conclude that poor results are not simply due to our inherent bias towards early revision and secondary resurfacing of the unresurfaced patella

Patients with painful metal-on-metal bearings presenting to the orthopaedic surgeon are a difficult diagnostic challenge. The surgeon must go back to basic principles, perform a complete history and physical exam, obtain serial radiographs and basic blood work (ESR, CRP) to rule out common causes of pain and determine if the pain is, or is not, related to the bearing. The Asymptomatic MoM Arthroplasty: Patients will present for either routine follow up, or because of concerns re: their bearing. It is important to emphasise that at this point the vast majority of patients with a MoM bearing are indeed asymptomatic and their bearings are performing well. The surgeon must take into account: a) which specific implant are they dealing with and what is its track record; b) what is the cup position; c) when to perform metal ion testing; d) when to perform further soft tissue imaging (MARS MRI, Ultrasound); e) when to discuss possible surgery. Painful MoM THA causes not related to the bearing couple: These can be broken down into two broad categories. Causes that are Extrinsic to the hip include: spine, vascular, metabolic and malignancy. Causes that are Intrinsic to the hip can either be Extracapsular (iliopsoas tendonitis and trochanteric bursitis) or Intracapsular (sepsis, loosening, thigh pain, prosthetic failure). Painful MoM THA causes related to the bearing couple: There are now described a number of possible clinical scenarios and causes of pain that relate to the metal-on-metal bearing couple itself: a) local hypersensitivity reaction without a significant soft tissue reaction; b) local hypersensitivity reaction with a significant soft tissue reaction; c) impingement and soft tissue pain secondary to large head effect. Metal ions: obtaining serum, or whole blood, cobalt and chromium levels is recommended as a baseline test. However, there is no established cutoff level to determine with certainty if a patient is having a hypersensitivity reaction. A 7 parts per billion cutoff has been suggested. This gives high specificity, but poor sensitivity. Metal ions therefore can be used as a clue, and one more test in the workup, but cannot be relied upon in isolation to make a diagnosis. MARS MRI: a useful tool for demonstrating soft tissue involvement, but there are many painless, well-functioning MoM implants that have soft tissue reactions, that don't require a revision. In the painful MoM hip an MRI, or ultrasound, is recommended to look for soft tissue destruction or a fluid-filled periprosthetic lesion (pseudotumor). Significant soft tissue involvement is concerning and is commonly an indication for revision in the painful MoM hip. Treatment: management of the painful MoM hip is directly related to the etiology of the pain. Unique to MoM bearing is the issue of pain secondary to a local hypersensitivity reaction. All above tests should be utilised to help determine the best course of action in any individual patient. The painful MoM bearing, that is demonstrating significant soft tissue involvement is a concerning scenario. Earlier revision, to prevent massive abductor damage, would seem prudent for these patients. The painful MoM bearing with no significant soft tissue changes can probably be followed and reviewed at regular intervals. If the pain persists and is felt to be secondary to a hypersensitivity reaction, then revision is really the only option, although the patient must be cautioned regarding the unpredictable nature of the pain relief

Metal-on-metal bearing surfaces were used frequently until recently because of the potential for decreased wear and the ability to use large femoral heads which can reduce instability. However, data reported in the Australian registry over the past 5 years demonstrated an increase in failure rates compared to metal-on-polyethylene bearings. In addition, adverse local tissue reactions (ALTR) associated with pseudotumors and destruction of the soft tissue around the joint have led to revision of these implants. Unfortunately, at the present time there is no optimal management strategy that has been delineated for metal-on-metal implants because of a lack of evidence. The biologic response to metal-on-metal implants is usually local but may be systemic. The management of these patients is complex because patients may have pseudotumors and/or elevated metal ion levels and be asymptomatic. In addition, there are a number of intrinsic causes (loosening, infection, iliopsoas tendinitis) and extrinsic causes (spinal disease, trochanteric bursitis) that can be a source of pain. There is no evidenced based approach to manage these patients and no single test should be used to determine treatment. A thorough clinical evaluation is essential and blood tests are necessary to rule out infection. Imaging studies including plain radiographs and a MARS MRI are needed to evaluate either the stability of the prosthesis and to assess for the presence of pseudotumors and soft tissue destruction around the implant. Patients with symptomatic hips and evidence of muscle involvement on MRI require revision. Finally, the clinician must always be aware of the potential for systemic effects which require early and aggressive intervention to limit the adverse response to the metal and the metal bearing

The prevalence of pseudotumours in patients with large-head metal-on-metal (MOM) THA has been the subject of implant recalls and warnings from various regulatory agencies. To date, there is no consensus on whether ultrasound or MRI is superior for the detection of pseudotumours. Ultrasound is relatively cheap but can be operator dependent. MARS MRI has the advantage of excellent visibility of the soft tissue. However MRI comes at a marked increase cost and takes about twice as long to perform. At our institution we prospectively compared ultrasound to MRI for pseudotumour detection in an asymptomatic cohort of patients with MOM THAs. Methods. We enrolled 40 patients with large-head MOM THAs in the study. The mean age was 54 years (range, 34–76 years). The mean time from surgery was 54 months (range, 40–81 months). There were 28 men and 12 women. All patients underwent ultrasound and MRI using slice encoding for metal artifact correction. The gold standard was defined as follows: if both ultrasound and MRI agreed, this was interpreted as concordant and the result was considered accurate. Results. Ultrasound and MRI agreed in 37 of 40 patients (93%). The prevalence of pseudotumours was 31% (12 of 39) in our cohort. Twenty-three of 39 patients (59%) had completely normal tests and four (10%) had simple fluid collections. Ultrasound had a sensitivity of 100% and specificity of 96% while MRI had a sensitivity of 92% and specificity of 100%

Metal on metal bearing surfaces were used frequently until recently because of the potential for decreased wear and the ability to use large femoral heads which can reduce instability. However, data reported in the Australian registry over the past 5 years demonstrated an increase in failure rates compared to metal on polyethylene bearings. In addition, adverse local tissue reactions (ALTR) associated with pseudotumors and destruction of the soft tissue around the joint have led to revision of these implants. Unfortunately, at the present time there is no optimal management strategy that has been delineated for metal on metal implants because of a lack of evidence. The biologic response to metal on metal implants is usually local but may be systemic. The management of these patients is complex because patients may have pseudotumors and/or elevated metal ion levels and be asymptomatic. In addition, there are a number of intrinsic causes (loosening, infection, iliopsoas tendinitis) and extrinsic causes (spinal disease, trochanteric bursitis) that can be a source of pain. There is no evidence based approach to manage these patients and no single test should be used to determine treatment. A thorough clinical evaluation is essential and blood tests are necessary to rule out infection. Imaging studies including plain radiographs and a MARs MRI are needed to evaluate either the stability of the prosthesis and to assess for the presence of pseudotumors and soft tissue destruction around the implant. Patients with symptomatic hips and evidence of muscle involvement on MRI require revision. Finally, the clinician must always be aware of the potential for systemic effects which require early and aggressive intervention to limit the adverse response to the metal and the metal bearing

Metal-on-metal bearings (MoM) saw an increase in global utilisation in the last decade. This peaked in 2008 in the US, with approximately 35% of bearings being hard-on-hard (metal-on-metal, or ceramic-on-ceramic). Beginning in 2008, reports began to surface regarding local soft tissue reactions and hypersensitivity to MoM bearings. A major implant manufacturer recalled a resurfacing device in 2010 after national joint registries demonstrated higher than expected revision rates. Patients with painful MoM bearings are a difficult diagnostic challenge. The surgeon must go back to basic principles, perform a complete history and physical exam, obtain serial radiographs and basic blood work (ESR, CRP) to rule out common causes of pain and determine if the pain is, or is not, related to the bearing. The Asymptomatic MoM Arthroplasty: Patients will present for either routine follow up, or because of concerns regarding their bearing. It is important to emphasise that at this point the vast majority of patients with a MoM bearing are indeed asymptomatic and their bearings are performing well. The surgeon must take into account: a) which specific implant are they dealing with and what is its track record; b) what is the cup position; c) when to perform metal ion testing; d) when to perform further soft tissue imaging (MARS MRI, Ultrasound); e) when to discuss possible surgery. Painful MoM THA causes not related to the bearing couple: These can be broken down into two broad categories. Causes that are Extrinsic to the hip include spine, vascular, metabolic and malignancy. Causes that are Intrinsic to the hip can either be Extracapsular or Intracapsular. Painful MoM THA causes related to the bearing couple: There are now described a number of possible clinical scenarios and causes of pain that relate to the MoM bearing couple itself: A) Local hypersensitivity reaction without a significant soft tissue reaction; B) Local hypersensitivity reaction with a significant soft tissue reaction; C) Impingement and soft tissue pain secondary to large head effect. Factors related to a hypersensitivity reaction: Some patients, and prostheses, seem to be at a higher risk of developing issues following a MoM bearing, although our understanding of the interplay of these factors is still in evolution: patients at risk include all women and patients with smaller component sizes. Implant factors play a role with some implants having higher wear rates and being more prone to corrosion. Special tests: There is ongoing confusion related to the relative value of the various special tests that patients with a painful MoM undergo. A) Metal Ions - obtaining serum, or whole blood, cobalt and chromium levels is recommended as a baseline test. However, there is no established cutoff level to determine with certainty if a patient is having a hypersensitivity reaction. Metal ions therefore can be used as a clue, but cannot be relied upon in isolation to make a diagnosis. B) MARS MRI - a useful tool for demonstrating soft tissue involvement, but there are many painless, well-functioning MoM implants that have soft tissue reactions, that don't require a revision. In the painful MoM hip an MRI, or ultrasound, is recommended to look for soft tissue destruction or a fluid-filled periprosthetic lesion (pseudotumor). Significant soft tissue involvement is concerning and is commonly an indication for revision in the painful MoM hip. C) CT imaging - can be utilised to help determine cup position and combined anteversion, however, plain radiographs can give a rough estimate of this as well, so routine CT scan evaluations are not currently recommended. The painful MoM bearing, that is demonstrating significant soft tissue involvement is a concerning scenario. Earlier revision, to prevent massive abductor damage, would seem prudent for these patients. The painful MoM bearing with no significant soft tissue changes can probably be followed and reviewed at regular intervals. If the pain persists and is felt to be secondary to a hypersensitivity reaction, then revision is really the only option, although the patient must be cautioned regarding the unpredictable nature of the pain relief

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