Introduction Overview a metal-on-metal (MoM) pseudotumor, also known as aseptic lymphocyte-dominant vasculitis-associated lesion (ALVAL), is a mass-forming tissue reaction caused by metal-on-metal wear the lesion is neither infective or neoplastic, and develops in the vicinity of a total hip replacement (THA) treatment is typically revision arthroplasty for symptomatic pseudotumor with elevated metal ions Epidemiology incidence 10-15% of patients with MoM THA have a pseudotumor 45-50% of revisions in patients with MoM THA are due to pseudotumor or adverse local tissue reaction risk factors elevated cobalt and chromium levels female gender high acetabulum inclination angle > 55° pathophysiology mechanism two different mechanisms have been proposed for formation of pseudotumors: hypersensitivity to metal ions local high wear debris variability in distribution of metal debris, degree of necrosis, and number, type, and arrangement of inflammatory cells macrophages and lymphocytes are present in all cases with lymphocytes being predominant patient's with high wear have more macrophages than those with primarily hypersensitivity to metal ions patients with extensive infiltrates of macrophages tend to have smaller lymphocytic aggregates. Presentation History patient may complain of gradual onset of symptoms or a sudden inciting pain in the groin Symptoms common symptoms may be asymptomatic groin pain trendelenburg gait Physical Exam inspection soft tissue masses around the hip may be present neurovascular usually normal provocative tests groin pain with flexion, IR and adduction groin pain with rising from a chair Imaging Radiographs recommended views AP pelvis, AP and lateral of affected hip findings will show metal-on-metal THA necessary to rule out peri-prosthetic fractures as source of pain may show peri-prosthetic bony erosion, commonly seen in calcar region MRI with Metal Artifact Reduction Sequence (MARS) indications normal radiographs without evidence of component lossening findings a pseudotumor will appear like a fluid collection or solid mass in periprosthetic soft tissues T1 weighted images will show signal similar to bladder contents (transudate) T2 weighted images will generally show hyperintensity as compared to muscle and may be heterogenous or homogenous the hypointense content observed in T2 sequences may be related to the presence of necrosis or metal deposition Studies Serum labs WBC, ESR and CRP metal ion levels (cobalt, chromium) serum metal ion concentration highest at 12-24 months following index surgery correlates with the initial "wear in" or "run-in" phase of increased particle generation, but then followed by a "steady state" phase of decreased particle generation values > 7 parts per billion (ppb, or mg/L) generally an indication for advanced imaging with MRI Invasive studies Hip aspiration synovial fluid analysis will allow for differentiation of a metallosis from periprosthetic infection gross appearance of metallosis generally described as "dishwater fluid" with watery, grayish and hazy appearance manual cell count necessary fibrinous debris from metal-on-metal reactions will falsely elevate automated cell counts Treatment Nonoperative observation indications well functioning painless THA with low metal ions and no pseudotumor on MRI outcomes studies show that around 40% of patients with a pseudotumor are asymptomatic Operative revision THA to ceramic-on-polyethelyne components indications painful metal on metal THA, elevated metal ions, pseudotumor on MRI rate of revision THA due to symptomatic pseudotumor is only 1.7–5.6% most patients with pain, elevated ions or a psudotumor on MRI require operative intervention outcomes significant bone loss, soft tissue destruction, degree of abductor muscle deficiency and poorlocal environment for healing corresponds to difficulty of revision and functional outcomes if severely compromised abductor function or damaged soft-tissue affects implant stability, may require the use of a contrained liner higher rates of dislocation and infection Techniques Observation technique in the asymptomatic patient, serial hip radiographs to assess for wear, or component loosening can be performed Revision THA to ceramic-on-polyethelyne components approach depends on location of tumor and surgeon preferene direct lateral and direct anterior commonly cited technique can be single stage or 2 stages depending on surgeon preference or presence/concern of infection depend on bone loss, abductor defiency and soft tissue damage constraint liners may be required if severe abductor deficiency is present complications instability deep infection aseptic loosening persistent iliopsoas tendonitis persistent metal related reaction Complications Repeat revision THA incidence 14-20% of revision THAs performed due to a MoM pseudotumor require a 2nd operation within 5 years treatment revision THA to address reason for repeat failure Pseudotumor induced femoral nerve palsy incidence rare, only case reports noted treatment decompression and revision THA to ceramic-on polyethelyne components
QUESTIONS 1 of 4 1 2 3 4 Previous Next (SBQ16HK.16) A 45-year-old female is referred to you for evaluation of her right hip. Five years ago, she was involved in a motor vehicle collision and sustained a femoral head fracture that was treated with a hip surface replacement arthroplasty. Her post-operative course was unremarkable and she didn't have any issues until 4 months ago when she noticed subtle hip and groin pain. She is otherwise healthy and wants to begin training for a marathon but is concerned about her hip due to television ads about metal-on-metal devices. Her radiographs show a well-placed implant and are otherwise unremarkable. What test would best evaluate for the most concerning complication from this implant? Tested Concept QID: 211284 Type & Select Correct Answer 1 CT including the pelvis, hip, and femur 7% (82/1248) 2 Whole body triple-phase bone scan 1% (17/1248) 3 MRI with metal artifact reduction sequence 44% (550/1248) 4 Serum cobalt and chromium levels 40% (495/1248) 5 Serum cobalt, chromium, molybdenum, and nickel levels 8% (99/1248) L 5 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review tested concept Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ13.270) Figure A shows a radiograph of a 62-year-old female that underwent a left total hip arthroplasty 5 years ago. She presents to your office with insidious onset of left groin and buttock pain. She denies trauma, fever or chills. On physical examination, her left hip has mild pain with range of motion. She has a normal gait cycle, normal power across the hip and her vitals signs are stable. A left hip aspirate was performed and results are shown in Figure B. What is the most likely cause of her hip pain? Tested Concept QID: 4905 FIGURES: A B Type & Select Correct Answer 1 Periprosthetic bacterial hip infection 8% (315/3747) 2 Periprosthetic hip fracture 0% (14/3747) 3 Large-particle wear debris disease 15% (554/3747) 4 Pseudotumor hypersensitivity response 75% (2794/3747) 5 Abductor tendon tear 1% (44/3747) L 3 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review tested concept
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