Sunday, July 13, 2014

Arthroprosthetic Cobaltism

Orthopedic Principles




Cobalt poisoning by hip replacement: Arthroprosthetic-Cobaltism

Stephen Tower, MD, University of Alaska, Alaska, USA

  • Cobalt, in excess, has the potential to block oxidative metabolism at the mitochondrial level.
  • The peripheral and central nervous systems, the heart, and the thyroid gland are variably compromised whether the means of cobalt exposure is iatrogenic (use of cobalt chloride as a hematemic), industrial (exhalation or ingestion of cobalt powders or ores), from the ingestion of cobalt laced beer (beer drinkers cardiomyopathy), or arthroprosthetic (wear of chrome-cobalt articular surfaces or corrosion and fretting of modular chrome-cobalt femoral necks and heads).
  • The toxicity of cobalt has been known since 1948.(1 2)
  • The first case report of arthroprosthetic-cobaltism was in Italian in 2001. The mechanism was wear or a revision chrome-cobalt femoral head by ceramic bits from the primary fractured ceramic component embedded in the revision plastic socket liner.
  • The degree of hypercobaltemia was unreported; symptoms of peripheral neuropathy were first noted 9 months after the first revision operation. Diagnosis was serendipitous.
  • A metal laden pericardial effusion was found on CT scan, prompting a radiograph of the asymptomatic hip revealing an aspherical femoral head. Resection arthroplasty was not performed until 16 months after the first revision operation, by then the patient’s pathology had progressed to severe motor and sensory neuropathy, pericardial tamponade, and hypothyroidism(.3)
  • Reports of 8 additional extreme cases of cobaltism from the ceramic-on-metal wear have followed. Blood cobalt levels in mcg/L ([BCo]) have ranged from 400 to 1000, latency to symptoms ranged from 3-48 months, and latency to diagnosis or revision surgery from 9 to 72 months.
  • All patients had neurologic pathology, most were hypothyroid, and all but three were noted to have cardiomyopathies. One patient died of heart failure, those patients followed > 6 months post second revision improved as their [BCo] declined.
  • The typical presentation of cobaltism was fatigue and anorexia, followed by numbness and weakness, hypothyroidism, deafness and blindness, and finally and sometimes fatally, heart failure or arrhythmias. Hypothyroidism was diagnosed in most cases before the diagnosis of cobaltism was made and some clinical improvement noted with onset of thyroid replacement therapy. None of the patients had notable sentinel hip symptoms before onset of overt systemic pathology.(4-11)
  • Sunday, May 4, 2014

    Recommendation request

    Steven Tucker, MD@drsteventucker
     Follow Follow 
    Dear Twitter, Can anyone suggest a surgeon for a total hip replacement in Melbourne?#THR #Melbourne cc @mydepuyhip
     09:23 AM - 03 Apr 14

    Biomet Metal-on-Metal Hip Implant Litigation Update: $56 Million Settlement Approved; Qualified

    Qualified Biomet Patients Need to File Lawsuit by April 15, 2014

    Device maker, Biomet Inc., announced that it will be pay at least $56 million to settle the MDL which involves consumer claims that the device maker manufactured a defective metal-on-metal hip implant device that may lead to serious metal ion build-up in patients' bodies. Allegations also include that the device may lead to metallosis (metal poisoning), difficulty walking, pain, and premature hip failure. These issues may, in turn, lead to a need for revision surgery to remove and replace the device.

    This settlement agreement extends to all cases currently pending in the Biomet MDL, and any future cases filed in a federal court on or before April 15, 2014. The agreement received approval from U.S. District Judge Robert L. Miller Jr. (In re: Biomet M2A Magnum Hip Implant Products Liability Litigation, case number 3:12-md-02391, in the U.S. District Court for the Northern District of Indiana)

    According to the settlement's definition, a qualified plaintiff is defined as a plaintiff who was implanted with a Biomet M2a-38 or M2a-Magnum hip implant and who later required that metal hip device to be "revised"--removed or repaired. Each of these qualified individuals will receive a base payment of $200,000; however, there are a number of variations to this amount, according to Law360, which are bas

    Read more:

    Biomet Hip Lawsuit News: More Than 1,200 Biomet Hip Replacement Claims Now Pending in Federal Litigation, Read more:

    MoM Hip Implants Present Diagnostic Challenges

    April 2014 AAOS 

    Terry Stanton
    Tribocorrosion occurring as articular surface loss at metal-on-metal (MoM) junctions in hip implants has emerged as one of the most important clinical problems in orthopaedic surgery. The problem has also attracted considerable media attention focused on complications occurring over time.
    Young-Min Kwon, MD, PhD
    During the “Metal on Metal and Modular Corrosion: Clinical Impact of Tribocorrosion” symposium Wednesday, panelists surveyed the pressing issues under investigation, including diagnostic modalities and treatment options for patients who may have adverse local tissue reactions (ALTRs) to metal debris.
    Retrieving valuable information
    Alister Hart, FRCS
    , of Royal National Orthopaedic Hospital in London, first reviewed what retrieval studies, involving 5,000 components from 22 countries, reveal about implant complications. He described such forensic analysis as akin to study of the black box from an airplane after a crash, providing clues to questions such as: What is the human wear rate? What surgical, design, and patient factors influence wear rate? How does the wear occur?
    Hip simulation and imaging findings can then guide the design of future implants in such parameters as material combinations, cup articular arc angle, and clearance.
    For retrieval studies, Dr. Hart described the following five ascending levels of data:
    1. Implant only—component size mismatch
    2. Intraoperative details—loosening, soft-tissue findings, impingement
    3. Clinical and blood details—to correlate laboratory tests with other clinical parameters
    4. Imaging—to distinguish between surgical and design factors
    5. Registry studies—“the ultimate method of understanding implant performance”
    Level 1 failures involving the implant only accounted for 1 percent of retrievals and showed a prominent circumferential wear scar with an oversized head, leading to a conclusion of component size mismatch and surgeon error. Blood metal ions were greater than 7 parts per billion (ppb) in all cases, and all the mismatches were missed at surgery and on plain radiograph.
    At level 2, he said, soft-tissue destruction may not be seen on radiographs, and patient sensitivity to metal debris is important. A reduced head-neck ratio increases the risk of impingement, and subluxation of the femoral head raises the risk for edge loading.
    Level 3 findings for patients with Birmingham Hip Resurfacing (BHR) found that half the patients had high wear and metal ion levels and half had low wear and metal ions.
    At level 4, radiographs are essential, Dr. Hart said. “A surgeon would never consider a hip revision operation without a radiograph. How can proper retrieval analysis be done without a radiograph?”
    Level 5 linkage to registry data is essential because it shows the failure rate of implants. “The ASR™ implant showed us that preclinical testing cannot predict the effect of all variables,” Dr. Hart said. “We all want well-performing implants. We need to know why implants fail if early data show a poor trajectory. To avoid continued use of a poor-performing implant, registry-retrieval linkage allows safe innovation.”
    He concluded that retrieval analysis enables surgeons to understand the causes of implant failure. The data helps in quantifying the impact of surgical positioning, implant design, and patient factors on clinical performance, and “linkage with registry data improves postmarket surveillance and the ability to safely innovate.”
    The risk variation
    Moderator Young-Min Kwon, MD, PhD, of Massachusetts General Hospital, explained that evaluation of a
    painful MoM hip should take a systematic approach that includes the following:
    • clinical history and physical examination
    • testing of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
    • radiographs
    • measurement of metal ion levels
    • cross-sectional imaging, such as metal artifact reduction software (MARS) MRI
    An algorithm for diagnosis includes identification of the implant by type and size (greater or less than 36 mm). The threshold for problematic ion levels is probably 7 ppb.
    Dr. Kwon provided a three-level risk stratification profile. The low-risk patient has a low activity level, is asymptomatic mechanically and systemically, and has no change in gait, abductor weakness, or swelling. Radiographs show optimal acetabular cup orientation and no implant osteolysis or loosening; metal ion levels are low (< 3 ppb). For this patient, annual follow-up is the recommendation.
    The moderate-risk patient would typically be a woman with mild local hip symptoms and no systemic symptoms. The patient has a change in gait but still no abductor weakness or swelling. The implant would be a large-diameter femoral head (³ 36 mm), a MoM total hip, a recalled implant, a hip resurfacing with risk factors (such as dysplasia), or a dual-taper modular neck device.
    Infection work-up would be normal, while metal ion levels would be moderately elevated (3–10 ppb). Cross-sectional imaging would indicate presence of abnormal tissue reaction without involvement of surrounding tissue and bone and simple cystic lesions or small cystic lesions without a thickened wall.
    For this patient, follow-up in 6 months is recommended, with revision surgery considered if symptoms or imaging abnormality progress, and/or metal levels rise within 6 months.
    The high-risk patient would have the signs and symptoms of the moderate-risk patient, but also with high activity level, abductor weakness and swelling, metal ions greater than 10 ppb, and presence of abnormal tissue reactions with involvement of surrounding muscles or bone. Revision should be considered for this patient.
    In evaluating the symptomatic patient, the physician should consider factors both intrinsic and extrinsic to the hip, Dr. Kwon said. There should be a “low threshold to perform a systematic evaluation,” and early and accurate diagnosis is important.
    Better diagnosing
    Craig J. Della Valle, MD
    , of Rush University, also addressed the diagnostic challenges in MoM hips, particularly as they relate to periprosthetic joint infections (PJIs). “The intra-operative appearance may mimic purulence, and cell count may be likewise unreliable,” he said.
    He described a study to determine the utility of blood (ESR/CRP) and synovial fluid white blood cell (WBC) count to diagnose patients with a failed MoM bearing or a corrosion reaction. The study found that automated synovial WBC counts were inaccurate in 33 percent of tests run and that 41 of 47 hips initially identified as infected by these tests were actually not infected.
    His conclusion was that “the diagnostic challenges of PJI are magnified for hips with MoM bearings, corrosion or full-thickness wear. The synovial fluid WBC can frequently be falsely positive—about 10 percent of the time—but is still a good test. It should only be relied upon, however, if manual count is done or if a differential can be performed.”
    Dr. Della Valle said “the threshold to aspirate preoperatively should be much lower. The intra-operative appearance can be deceiving. A request for a manual count alerts the technician to examine the specimen.”
    Also appearing on the panel were Robert M. Urban, MD, of Rush University; H. John Cooper, MD, of Lenox Hill Hospital; and J. Mark Wilkinson, PhD, FRCS, of the University of Sheffield.
    Details of the authors’ disclosure as submitted to the Orthopaedic Disclosure Program can be found in the Final Program; the most current disclosure information may be accessed electronically
    2014 Annual Meeting News
    Tuesday through Friday, March 11 – 14, 2014.

    Friday, March 14, 2014

    2013 Mar 20;95(6):512-8. doi: 10.2106/JBJS.L.00471.

    Ten-year outcome of serum metal ion levels after primary total hip arthroplasty: a concise follow-up of a previous report*.


    We previously reported on the metal ion concentrations of cobalt, chromium, and titanium that were found in the serum of patients three years after they had undergone primary total hip arthroplasty as compared with the concentrations found in the serum of control patients who did not have an implant. This study is a concise update on the serum metal levels found in a cohort of these patients ten years after the time of hip implantation. Of the original seventy-five subjects, metal ion levels were available for forty patients (53%). Ten patients (hybrid group) had received a hybrid total hip replacement that consisted of a modular cobalt-alloy femoral stem with a cobalt-alloy femoral head that had been inserted with cement and a titanium acetabular socket that had been inserted without cement. Nine patients (cobalt-chromium [CoCr] group) had received an implant with an extensively porous-coated modular cobalt-alloy femoral stem and femoral head along with a titanium acetabular socket; the femoral and acetabular components had each been inserted without cement. Eight patients (titanium group) had undergone insertion of a proximally porous-coated modular titanium-alloy femoral stem with a cobalt-alloy femoral head and a titanium acetabular socket; the femoral and acetabular components had each been inserted without cement. Thirteen patients (control group) from the original control group of patients who had not received an implant served as control subjects. Serum metal levels were measured with use of high-resolution sector field inductively coupled plasma mass spectrometry. The hybrid total hip arthroplasty group had mean cobalt levels that were 3.2 times higher at 120 months than they were at baseline, and the cobalt levels in that group were significantly higher than those in the titanium total hip arthroplasty group at thirty-six, sixty, eighty-four, ninety-six, and 120 months (p < 0.01). The hybrid group had mean chromium levels that were 3.9 times higher at 120 months than they were at baseline, and the CoCr total hip arthroplasty group had chromium levels that were 3.6 times higher at 120 months than they were at baseline. The serum titanium levels were higher in the titanium group at all follow-up time intervals as compared with the levels in all other groups, and the level in the titanium group at 120 months was eighteen times higher than it was at baseline (p < 0.01). Patients with well-functioning primary metal-on-polyethylene total hip replacements had elevated serum metal levels for as many as ten years postoperatively. Furthermore, metal release at the modular femoral head-neck junctions, rather than passive dissolution from porous ingrowth surfaces, was likely the dominant source of serum cobalt and chromium.

    Metal Levels Rise Following Second hip replacement

    2013 Oct;42(10):E84-7.

    Effect of a second joint arthroplasty on metal ion levels after primary total hip arthroplasty.


    Serum metal ion levels increase after primary total hip arthroplasty (THA) regardless of bearing surface. We conducted a study to determine the effect of a second joint arthroplasty on existing serum metal ion levels at long-term followup. Twelve patients underwent primary THA and then either another THA (8 patients) or total knee arthroplasty (TKA) (4 patients). The secondary procedures were performed a mean of 102.7 months (range, 36-144 months) after the index surgeries. The secondary THA group had significantly elevated levels of cobalt ion at 36 and 48 months, chromium ion at 12 and 24 months, and titanium ion at 48 and 72 months. The TKA group had no significant differences in cobalt, chromium, or titanium ion levels up to 72 months after surgery. Overall, when metal-polyethylene THA was performed after primary THA, there was a trend toward elevated serum metal ion levels at all follow-up intervals. This trend should be investigated with larger clinical trials.