Hip Arthroplasty Pseudotumors: Pathogenesis, Imaging, and Clinical Decision Making

US-Guided Interventional Procedures for Total Hip Arthroplasty

In patients with total hip arthroplasty (THA) with recurrent pain, symptoms may be caused by several conditions involving not just the joint, but also the surrounding soft tissues including tendons, muscles, bursae, and peripheral nerves. US and US-guided interventional procedures are important tools in the diagnostic work-up of patients with painful THA given that it is possible to reach a prompt diagnosis both directly identifying the pathological changes of periprosthetic structures and indirectly evaluating the response and pain relief to local injection of anesthetics under US monitoring. Then, US guidance can be used for the aspiration of fluid from the joint or periarticular collections, or alternatively to follow the biopsy needle to collect samples for culture analysis in the suspicion of prosthetic joint infection. Furthermore, US-guided percutaneous interventions may be used to treat several conditions with well-established minimally invasive procedures that involve injections of corticosteroid, local anesthetics, and platelet-rich plasma or other autologous products. In this review, we will discuss the clinical and technical applications of US-guided percutaneous interventional procedures in painful THA that can be used in routine daily practice for diagnostic and therapeutic purposes.

Pseudotumor from ceramic-on-ceramic total hip arthroplasty

INTRODUCTION AND IMPORTANCE

Total hip arthroplasty is one of the most performed surgical interventions in the world. Adverse local tissue reactions and pseudotumors are infrequent but dangerous eventualities, which are often related with metal-on-metal or metal-on-polyethylene implants. This study wants to highlight how adverse local tissue reactions and pseudotumors must be taken into consideration during the diagnostic process.

CASE PRESENTATION

We report the case of a patient with ceramic-on-ceramic modular total hip arthroplasty with titanium neck. 12 years after surgery, he complained of pain and swelling on the hip. Diagnostic tests revealed the presence of a bulky pseudotumor. During the revision surgery biopsy samples were taken and microscopical analysis revealed the presence of fibrous tissue, fibrin hemorrhagic collections, histiocytes and chronic inflammation due to foreign body, with dark refractive material of an exogenous nature.

CLINICAL DISCUSSION

The possible formation of pseudotumor and metallosis reactions in hip prostheses with metal-on-metal coupling or in couplings with polyethylene is known. Many cases of pseudotumor are reported after revision of prostheses due to the breakage of ceramic components, but we did not observe any damage or corrosion of the prosthetic elements; on the other hand, we noticed an excessive retroversion of the femoral neck. It may be possible that an accurate microscopic analysis could clarify the failure of this implant.

CONCLUSION

To date ceramic-ceramic coupling remains the gold standard in terms of resistance and durability for hip arthroplasty but there is still a gap of knowledge in the field of tribology and individual immune response mechanisms.

When Is a Two-Stage Surgical Procedure Indicated in the Treatment of Pseudotumors of the Hip? A Retrospective Study of 21 Cases and a Review of the Literature

(1) Background: A pseudotumor of the hip is a sterile, non-neoplastic soft tissue mass associated with total hip arthroplasties. Pseudotumors may mimic soft tissue tumors or infections, and thus a differential diagnosis is crucial, and biopsy is recommended. The purpose of this study was to compare the complications and functional results between one-stage and two-stage procedures. (2) Methods: We retrospectively analyzed 21 patients surgically treated at our institution with "pseudotumors" associated with hip prosthesis (8 male, 13 female with a mean age of 69 years). One-stage revision was performed in 10 cases and two-stage reversion in 10, with excision only in 1 case. Complications were classified as major and minor and functional results assessed using the Harris Hip Score (HHS). (3) Results: Five patients (24%) reported major complications. The survival rate for all complications was 75%. The overall survival rate was 95% at 5 years. The mean HHS ranged from 35 pre-op to 75 post-op, highlighting improved functional results in all cases. We recorded no differences in complications or functional outcomes between the one- and two-stage procedures. (4) Conclusions: In our experience, the two-stage surgical approach is preferable in cases with major bone defects and larger pseudotumor sizes. The use of custom-made 3D-printed prostheses is increasing and is a further reason to prefer two-stage revision.

Arthroplasty-Related Pseudotumor of the Scapula: Case Report and Review of the Literature

Arthroplasty-related pseudotumors are nonneoplastic and noninfectious inflammatory masses that are typically associated with adverse reaction to metal debris. Pseudotumors most commonly occur in the setting of metal-on-metal joint replacements at the hip. However, the presentation of pseudotumor at the shoulder is exceedingly rare. In this article, we reported a case of arthroplasty-related pseudotumor of the scapula. Clinical history, radiologic signs, and tissue analysis are described. Knowledge of this rare diagnosis will support clinical decision making for teams of radiologists, pathologists, oncologists, and orthopaedic surgeons who provide care for patients presenting with suspicious shoulder masses.

Hyaluronic acid-British anti-Lewisite as a safer chelation therapy for the treatment of arthroplasty-related metallosis

Cobalt-containing alloys are useful for orthopedic applications due to their low volumetric wear rates, corrosion resistance, high mechanical strength, hardness, and fatigue resistance. Unfortunately, these prosthetics release significant levels of cobalt ions, which was only discovered after their widespread implantation into patients requiring hip replacements. These cobalt ions can result in local toxic effects-including peri-implant toxicity, aseptic loosening, and pseudotumor-as well as systemic toxic effects-including neurological, cardiovascular, and endocrine disorders. Failing metal-on-metal (MoM) implants usually necessitate painful, risky, and costly revision surgeries. To treat metallosis arising from failing MoM implants, a synovial fluid-mimicking chelator was designed to remove these metal ions. Hyaluronic acid (HA), the major chemical component of synovial fluid, was functionalized with British anti-Lewisite (BAL) to create a chelator (BAL-HA). BAL-HA effectively binds cobalt and rescues in vitro cell vitality (up to 370% of cells exposed to IC50 levels of cobalt) and enhances the rate of clearance of cobalt in vivo (t1/2 from 48 h to 6 h). A metallosis model was also created to investigate our therapy. Results demonstrate that BAL-HA chelator system is biocompatible and capable of capturing significant amounts of cobalt ions from the hip joint within 30 min, with no risk of kidney failure. This chelation therapy has the potential to mitigate cobalt toxicity from failing MoM implants through noninvasive injections into the joint.

Metallosis in Total Hip Arthroplasty

» Metallosis is a rare but significant complication that can occur after total hip arthroplasty (THA) for a variety of reasons but most commonly in patients with metal-on-metal implants.» It is characterized by the visible staining, necrosis, and fibrosis of the periprosthetic soft tissues, along with the variable presence of aseptic cysts and solid soft tissue masses called pseudotumors secondary to the corrosion and deposition of metal debris.» Metallosis can present with a spectrum of complications ranging from pain and inflammation to more severe symptoms such as osteolysis, soft tissue damage, and pseudotumor formation.» Workup of metallosis includes a clinical evaluation of the patient's symptoms, imaging studies, serum metal-ion levels, and intraoperative visualization of the staining of tissues. Inflammatory markers such as erythrocyte sedimentation rate and C-reactive protein along with intraoperative frozen slice analysis may be useful in certain cases to rule out concurrent periprosthetic joint infection.» Management depends on the severity and extent of the condition; however, revision THA is often required to prevent rapid progression of bone loss and tissue necrosis.

A Sarcoma Masquerading as a Pseudotumor After Total Hip Arthroplasty: A Case Report

CASE

There is an increasing emphasis on adverse reactions to metal debris around prosthetic hip implants. We present a case report of a patient with increasing pain around a previous total hip arthroplasty and magnetic resonance imaging findings consistent with a pseudotumor. Serum metal ion levels were not elevated and initial biopsy findings inconclusive. The patient was diagnosed with an extraskeletal chondrosarcoma after revision total hip arthroplasty and subsequently underwent external hemipelvectomy with negative margins.

CONCLUSION

This report highlights the importance of remaining vigilant for malignant sarcomas presenting as pseudotumors around hip replacements, particularly in the absence of abnormal metal ion levels or definitive biopsy results.

Rare Pseudotumor in Ceramic-On-Ceramic Total Hip Replacement with Concomitant Fungal Periprosthetic Joint Infection: A Case Report

BACKGROUND Total hip replacement (THR) is a commonly performed treatment for severe osteoarthritis. In this report, we present the case of a woman who unfortunately suffered 2 severe but rare complications of THRs: a pseudotumor formation on a Delta ceramic-on-ceramic bearing and a fungal periprosthetic joint infection (PJI). CASE REPORT In early 2016, a 63-year-old woman underwent an elective left total hip replacement with ceramic-on-ceramic bearing due to severe osteoarthritis. In 2021, she suffered 2 unprovoked DVTs. Therefore, ultrasound (US) Doppler imaging of the left lower limb was performed, which showed a mass close to the iliac vein. After magnetic resonance imaging (MRI) to further examine the mass, a pseudotumor was confirmed. Revision surgery was performed, after which positive swabs for fungal infection were identified, but were not clinically correlated. A few years before, a deep buccal fungal infection was suspected and treated, but never confirmed. The pseudotumor was confirmed by histology samples. A few weeks later, the patient presented again with symptoms of infection, and 2 debridement, antibiotics, and implant retention (DAIR) procedures were performed, in which further positive swabs of Candida parapsilosis were obtained. Currently, the patient is on conservative therapy with long-term antifungal medication since she refused a staged procedure due to personal circumstances. CONCLUSIONS In conclusion, this case report documents the first ever reported pseudotumor associated with a ceramic-on-ceramic bearing THR with concomitant fungal PJI. Although it is unlikely for a person to develop 2 rare complications without them being connected, no causal link could be established.

Massive pseudotumor of unknown etiology in a cemented metal-on-polyethylene total hip arthroplasty: a case report

Background

The formation of destructive pseudotumors is a well-documented, albeit rare, complication of total hip arthroplasties. They tend to be progressive and, if left untreated, can result in extensive periprosthetic bony destruction. The current case presents a large benign mass consistent with a pseudotumor on both imaging and intraoperative findings but histologic findings demonstrating chronic hematoma.

Case Description

An 86-year-old female with a metal-on-polyethylene total hip presented with a massive pseudotumor accompanied by extensive bony lysis. Due to pain and chronic anemia, a palliative debulking procedure was undertaken as a palliative measure. At one year follow-up, the patient reported significant pain relief and was able to ambulate safely with gait aids. Her hemoglobin stabilized post-operatively and ongoing transfusions were not required. Final pathology was not supportive of particle disease despite this being the leading diagnosis. Microscopic sections showed tissue mostly composed of fibrin and blood with multiple foci of calcification and reactive papillary endothelial hyperplasia which can be seen in chronic hematomas.

Conclusions

This case presents the diagnostic dilemma of a large benign mass consistent with a pseudotumor on both imaging and intraoperative findings but histologic findings consistent with a chronic hematoma. It highlights the importance of close follow-up and early intervention when periprosthetic osteolysis is detected.

Adverse Local Tissue Reaction Associated With Ceramic-On-Metal Bearing Surface in Primary Total Hip Arthroplasty: Report of Two Cases

Total hip arthroplasty (THA) is one of the most common and successful surgical procedures worldwide. At the same time, it is constantly evolving, and as a consequence, advances in implant technology have led to significant improvements in the different materials of the acetabular and femoral components. The selection of bearing surfaces and their tribology are critical to achieving a successful outcome. Pseudotumors are important, and usually misdiagnosed, complications associated with hard bearing surfaces such as metal-on-metal couples. They belong to a group of reactions called adverse local tissue reaction, which can occur in the vicinity of any THA. We present 2 cases of adverse local tissue reaction associated with the use of ceramic-on-metal bearings surfaces in 2 primary THAs that were treated with modular component exchange during single-stage revision surgery.

Level of Evidence

IV.

Neurological emergency from rare spinal metalloma: Case report and literature review

Metallosis is a rare and poorly understood long-term complication of instrumented surgery that can result in an inflammatory pseudotumor termed metalloma. We describe a particularly unique case and compare it to 6 analogous cases identified by PubMed and/or Medline search through July 2020. A 79-year-old male with multiple prior spinal lumbar fusion procedures presented with progressive weakness and pain. Imaging revealed a large mass surrounding the right-sided paraspinal rod with extension into the spinal canal, neural foramina, extraforaminal spaces, psoas muscle, marrow spaces, and right sided pedicles. The case presented is a unique example of a unilateral metalloma with mixed-metal instrumentation that created a progressive neurologic deficit without infection, pseudoarthrosis, or hardware failure. This case highlights the lack of understanding regarding the pathophysiology of metallosis and metalloma in spinal instrumentation. We highlight the imaging findings of metalloma to encourage early identification for removal and decompression.

Metallosis following hip arthroplasty: two case reports

Background

There has been increasing recognition of local and systemic adverse events associated with the release of metal ions and nanoparticles from hip arthroplasty components. Adverse local tissue reactions to metal ion debris can include periprosthetic solid and cystic masses known as pseudotumors. These masses can result in pain, swelling, extensive destruction to surrounding hip soft-tissues, and compression syndromes on neurovascular, gastrointestinal, and genitourinary structures. As reports of pseudotumors requiring multidisciplinary excision are limited, we present two pseudotumor cases that were excised through a combined approach.

Case presentations

The first case involves a 60-year-old Caucasian female with a large pseudotumor with intrapelvic and vascular involvement associated with a metal-on-polyethylene total hip arthroplasty, excised with contributions from general surgery, vascular surgery, and orthopedic surgery. Pseudotumor excision was followed by a revision total hip reconstruction in addition to an abductor mechanism reconstruction with tendo-Achilles allograft. The second case is that of a 64-year-old Caucasian female with a pseudotumor in close relationship to the femoral vessels following a metal-on-metal hip resurfacing, excised with a combination of vascular surgery and orthopedic surgery, with subsequent revision total hip reconstruction.

Conclusions

There remains a lack of literature to support the extensiveness of pseudotumor excision required in complex cases with significant intrapelvic or vascular involvement. Given the potential for significant adverse effects of large masses, the authors’ preference is to involve a multidisciplinary team to achieve a more comprehensive excision while minimizing the risk of potential complications.

Cobalt Levels and Pseudotumor Characteristics Vary due to Metal Ion Source: Modular Femoral Neck vs Metal-on-Metal Articulations

BACKGROUND

This study examines cobalt levels and pseudotumor characteristics in a non-recalled modular femoral prosthesis. We sought to determine relationships between serum cobalt levels and pseudotumors following modular and metal-on-metal (MoM) total hip arthroplasty (THA), the location and size of pseudotumors, and changes to pseudotumor grade over time.

METHODS

We retrospectively evaluated a cohort of 190 primary THAs implanted with a dual-modular femoral stem by one surgeon from 2005 to 2013. One hundred seventeen THAs used a cobalt-chromium modular neck (CoCrMN) component and non-MoM articulation, 63 THAs had a titanium neck component and MoM articulation, and 10 had a titanium neck component and polyethylene liner. Serum ion levels were recorded for all patients. Pseudotumor grade and location were measured by musculoskeletal-trained radiologists.

RESULTS

Cobalt levels did not correlate to time after index arthroplasty. In the CoCrMN group, cobalt levels were elevated in 11 of 19 (57.9%) patients with pseudotumor compared to 14 of 19 (73.7%) in the MoM group. Pseudotumors were more often located lateral to the hip joint in the CoCrMN group compared to anteromedial following MoM arthroplasty. In CoCrMN THAs, pseudotumors were visualized in 12 of 51 (23.5%) initial MARS MRIs within 40 months compared to 5 of 66 (7.6%) performed later (P = .02).

CONCLUSION

Pseudotumor characteristics differ between patients with CoCrMN designs vs those with an MoM articulation. Normal serum cobalt levels did not exclude the presence of a pseudotumor and routine MARS MRI should be included in follow-up of patients with this CoCrMN prostheses.

Catastrophic failure and metallosis of the acetabular component in total hip arthroplasty

Background

To evaluate the clinical features and results of the revision total hip arthroplasties (THA) in patients with catastrophic failures and metallosis.

Methods

Fifteen hips of 14 patients with catastrophic failure and metallosis in hip arthroplasties were evaluated. They were followed for at least 4.2 years after the revision THA. Clinical evaluation was performed using Harris hip score. Osteolysis, loosening or presence of metallosis was evaluated with standard radiographs. Metallosis was evaluated intraoperatively according to the metallosis severity classification.

Results

The mean time from failure until revision surgery was 9.4 years. It was observed that in the primary THA, metal-on-ceramic (MoC), ceramic-on-ceramic (CoC) and metal-on-conventional polyethylene (MoCPE) bearings were used in 1, 3 and 11 hips, respectively. Grade III metallosis was observed in all patients during revision surgeries. The mean Harris hip score increased from 55 points before revision THA to 75 points at the final follow-up. In revision arthroplasty, MoCPE and CoC bearings were used in 13 and 2 hips, respectively. The femoral stem was replaced in 5 hips. All acetabular cups, except that of one hip, were revised.

Conclusions

Revisions of THAs with catastrophic failures and metallosis are quite challenging. Routine follow-up of arthroplasty patients is beneficial to examine for osteolysis, loosening, and asymmetric wear.

Pseudotumors in Total Joint Arthroplasty

»

The true incidence of pseudotumors in association with total joint arthroplasty is underestimated.

»

Pseudotumors occur with metal-on-metal, metal-on-polyethylene, and metal-on-ceramic articulations.

»

Metal ion levels should not be the only factor in decision-making regarding revision surgery.

»

Revision surgery is only indicated in symptomatic patients with clinical and radiographic findings and elevated metal ion levels.

»

Revision to a non-metal articulation is strongly suggested.

N-Acetyl-Cysteine Reduces Blood Chromium and Cobalt Levels in Metal-on-Metal Hip Arthroplasty

The most common reasons for revision of metal-on-metal hip arthroplasty are aseptic loosening and metal reaction. Failure of a metal-on-metal implant due to the aggressive destruction of periprosthetic tissues may require extensive reconstruction procedures. The aim of this case report is to describe the treatment in an asymptomatic patient with high levels of chromium and cobalt, using chelation therapy. The rational use of N-acetyl-cysteine (NAC) involves thiol groups to chelate sites for metals. More than 10 years after the metal-on-metal hip arthroplasty, the patient did not have to undergo revision surgery; the levels of the ions in the blood were considerably lowered (chromium from 4.51 mcg/L to 1.85 mcg/L; cobalt from 7.78 UG/L to 0.8 UG/L) after using NAC without adverse effects.

Pseudotumor Caused by a Retained Intra-articular Bullet: A Case Report

CASE

A 54-year-old man presented with systemic lead poisoning due to a gunshot wound to the hip suffered 35 years prior to presentation. He urgently underwent removal of the bullet with total hip arthroplasty and was found to have a pseudotumor. This case highlights the team-based approach to manage systemic lead poisoning caused by an intra-articular bullet.

CONCLUSION

We report on the first documented case of systemic lead toxicity and a pseudotumor caused by an intra-articular bullet. An expeditious, team-based approach is necessary for appropriate treatment. Our treatment algorithm can guide future teams on the management of this reversible disorder.

Femoral head disengagement from Accolade femoral stem in MOM Arthroplasty: a case study and literature review

Background: Metal on Metal Hip arthroplasty was commonly used until the last decade. However Hip Arthroplasty registries of many countries showed increased revision rates of MOM Hips – these high rates of revision caused by trunnionosis, adverse tissue reactions (ALTRs) and Pseudotumor formation.

The Case: Our Case is 73 years old gentleman who had left MOM THR in 2008, and was doing fine till the beginning of 2018 when his left leg stuck while getting out of the car. Despite he heard the pop and his leg was shortened and externally rotated, but he was still walking on it for a while. On reviewing him in our orthopedic clinic and after getting the CT-scan showed that he had dislocated femoral head from the stem.

Particulate wear debris osteolysis, acute urinary retention and delirium as late complications of hip arthroplasty

Intrapelvic mass formation as a result of particulate wear debris induced osteolysis is a recognised late complication of cementless total hip arthroplasty. Clinical presentation typically involves hip and/or leg pain resulting in functional impairment, and obstructive urinary symptoms developing 3-20 years after surgery. An acute confusional state has never been described in this scenario. We report the case of an 86-year-old gentleman with a diagnosis of dementia brought to our emergency department with an acute confusional state. Abdominal imaging revealed a distended bladder, a large pelvic mass and a lytic lesion within his right acetabulum. Cytological and microbiological examination of fluid obtained with radiologically guided aspiration of the mass was negative for neoplasia and infection.

Association Between Pseudotumor Formation and Patient Factors in Metal-on-Metal Total Hip Arthroplasty Population

BACKGROUND

Pseudotumor formation from metal-on-metal (MoM) hip implants is associated with implant revision. The relationship between pseudotumor type and patient outcomes is unknown.

METHODS

We retrospectively reviewed patients with a MoM total hip arthroplasty and metal artifact reduction sequence magnetic resonance imaging. Pseudotumors were graded using a validated classification system by a fellowship-trained radiologist. Patient demographics, metal ion levels, and implant survival were analyzed.

RESULTS

Pseudotumors were present in 49 hips (53%). Thirty-two (65%) pseudotumors were cystic thin walled, 8 (16%) were cystic thick walled, and 9 (18%) were solid masses. Patients with pseudotumors had high offset stems (P = .030) but not higher metal ion levels. Patients with thick-walled cystic or solid masses were more likely to be symptomatic (P = .025) and were at increased risk for revision (P = .004) compared to patients with cystic lesions.

CONCLUSION

Pseudotumor formation is present in 53% of patients with a MoM total hip arthroplasty, of which 40% were asymptomatic. Patients with thick-walled cystic and solid lesions were more likely to be symptomatic and undergo revision.

Systemic and local toxicity of metal debris released from hip prostheses: A review of experimental approaches

Despite the technological improvements in orthopedic joint replacement implants, wear and corrosion products associated with the metal components of these implants may result in adverse local tissue and perhaps systemic reactions and toxicities. The current review encompasses a literature review of the local and systemic toxicity studies concerning the effect of CoCrMo wear debris released from wear and corrosion of orthopedic implants and prostheses. Release of metallic debris is mainly in the form of micro- and nano-particles, ions of different valences, and oxides composed of Co and Cr. Though these substances alter human biology, their direct effects of these substances on specific tissue types remain poorly understood. This may partially be the consequence of the multivariate research methodologies employed, leading to inconsistent reports. This review proposes the importance of developing new and more appropriate in-vitro methodologies to study the cellular responses and toxicity mediated by joint replacement wear debris in-vivo.

Biological effects of metal degradation in hip arthroplasties

Metals and metal alloys are the most used materials in orthopedic implants. The focus is on total hip arthroplasty (THA) that, though well tolerated, may be associated with local and remote adverse effects in the medium-long term. This review aims to summarize data on the biological consequences of the metal implant degradation that have been attributed predominantly to metal-on-metal (MoM) THA. Local responses to metals consist of a broad clinical spectrum ranging from small asymptomatic tissue lesions to severe destruction of bone and soft tissues, which are designated as metallosis, adverse reactions to metal debris (ARMD), aseptic lymphocytic vasculitis associated lesion (ALVAL), and pseudotumors. In addition, the dissemination of metal particles and ions throughout the body has been associated with systemic adverse effects, including organ toxicity, cancerogenesis, teratogenicity, and immunotoxicity. As proved by the multitude of studies in this field, metal degradation may increase safety issues associated with THA, especially with MoM hip systems. Data collection regarding local, systemic and long-term effects plays an essential role to better define any safety risks and to generate scientifically based recommendations.

Two-Stage Treatment of a Large Pelvic Cystic Pseudotumor in a Metal-On-Metal Total Hip Arthroplasty

The authors report a case of a huge cystic pseudotumor, surrounding a failed metal-on-metal total hip arthroplasty (THA). The cyst surrounded the hip anteriorly, occupied part of the anterior portion of the thigh, and extended to the anterolateral aspect of the abdomen. The case was treated by a two-stage procedure. The first stage consisted of a percutaneous drainage of the fluid content of the cyst (∼1,200 mL). This procedure reduced the risk of tearing the cyst capsule spreading the liquid in the tissues surrounding the THA, and in the abdomen. Thanks to this simple procedure, the second stage treatment consisted of a relatively usual THA revision. The patient recovered completely from the treatment and returned to pain-free full activities of daily living.

Nongynecologic Findings Seen at Pelvic US

Ultrasonography (US) is frequently the first imaging modality used to examine women with symptoms involving the pelvis. It is widely available and involves no exposure to ionizing radiation. Images can be acquired with a transabdominal, endovaginal, or translabial approach, and the use of video clips and three-dimensional reconstructions can be helpful. US is excellent for assessment of the uterus, ovaries, and adnexa. Occasionally, nongynecologic pelvic diseases arising from the gastrointestinal, genitourinary, and musculoskeletal systems and the pelvic peritoneal and extraperitoneal spaces may be detected and can be a source of diagnostic dilemma. US can be helpful not only in the detection but also occasionally in the characterization of such entities. Computed tomography and magnetic resonance imaging are useful in complicated cases. In this article, the normal US appearance of the bowel and US signs of bowel disease and specific entities, including appendicitis, diverticular disease, bowel obstruction, appendiceal mucocele, and intestinal tumors, are reviewed. The lower urinary tract is included in the field of view in every pelvic US examination; commonly encountered entities related to the urinary bladder, distal ureter, and urethra are illustrated. In addition to arising in the gastrointestinal and genitourinary tracts, pathologic conditions in the pelvis can arise in the peritoneal or extraperitoneal space. Although conditions of the pelvic peritoneal and extraperitoneal spaces are rare, it is important to recognize these entities and distinguish them from the more common gynecologic diseases. Owing to the implications for diagnosis and management, radiologists and other physicians who perform pelvic US should be aware of the spectrum of nongynecologic pathologic entities that can be detected. ©RSNA, 2017.

Pseudotumor in ceramic-on-metal total hip arthroplasty

The increasing demand for total hip arthroplasty (THA) in relatively young, high-demand patients has led to the use of hard-on-hard bearing surfaces. Adverse local tissue reaction/pseudotumor and elevated serum metal ion levels are commonly reported complications encountered in metal-on-metal THA, while audible articulation and rim fracture are reported in ceramic-on-ceramic THA. For this reason, ceramic-on-metal THA was implemented as an ideal hard-on-hard bearing combination. In this report, we describe a case of bilateral simultaneous ceramic-on-metal THA in a 69-year-old woman who presented 7 years postoperatively with unilateral hip pain associated with underlying pseudotumor and elevated serum cobalt and chromium ion levels. Pre-revision workup, intraoperative findings, and postoperative evaluation are included and suggest acetabular malposition as a potential source for complication.

Cobalt Cardiomyopathy Secondary to Hip Arthroplasty: An Increasingly Prevalent Problem

A forty-year-old man experienced worsening heart failure four years following bilateral complicated total hip replacement. His condition was extensively worked up but no underlying pathology was immediately evident. Given the cobalt-chromium alloy component present in the hip arthroplasties, the raised cobalt blood levels, and a fitting clinical picture coupled with radiological findings, the patient underwent right hip revision. Evidence of biotribocorrosion was present on direct visualisation intraoperatively. The patient subsequently experienced symptomatic improvement (NYHA class III to class I) and echocardiography showed recovery of ejection fraction. Cobalt exists as a bivalent and trivalent molecule in circulation and produces a cytotoxicity profile similar to nanoparticles, causing neurological, thyroid, and cardiological pathology. Blood levels are not entirely useful as there is no identifiable conversion factor for levels in whole blood, serum, and erythrocytes which seem to act independently of each other. Interestingly cobalt cardiomyopathy is frequently compounded by other possible causes of cardiomyopathy such as alcohol and a link has been postulated. Definitive treatment is revision of the arthroplasty as other treatments are unproven.

Comparison of Pre-Revision Magnetic Resonance Imaging and Operative Findings in Mechanically Assisted Crevice Corrosion in Symptomatic Metal-on-Polyethylene Total Hip Arthroplasties

BACKGROUND

Failed total hip arthroplasty (THA) caused by mechanically assisted crevice corrosion (MACC) has serious consequences-notably, adverse local tissue reactions. Metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) has been used to evaluate failed THA for other reasons but has not been assessed for the analysis of cases of MACC in the setting of metal-on-polyethylene arthroplasties.

METHODS

We examined the correlation between preoperative MARS MRI and surgical findings in a cohort of 20 consecutive patients undergoing revision THA for symptomatic MACC without other associated orthopedic diagnoses. Surgical findings included soft tissue and bone evaluation, presence and location of fluid, abductor disruption, composite tissue damage grade, and prosthesis trunnion damage at the time of revision.

RESULTS

MARS MRI complex synovitis, thickened pseudocapsule, and extra-articular fluid extension each strongly correlated with both the soft-tissue damage grade and trunnion damage noted at surgery. Bone marrow edema was also found to strongly correlate with bone necrosis intraoperatively.

CONCLUSION

MARS MRI is an excellent diagnostic tool for evaluation of patients with elevated serum Co after metal-on-polyethylene THA. Patients with complex synovitis, a thick pseudocapsule, bone marrow edema, and extra-articular fluid should strongly consider revision surgery.