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Adverse reactions to metallic debris from corrosion of polished cobalt-chromium–cemented femoral stems are reported. Cobaltism (systemic cobalt poisoning) has not been reported from this phenomenon. Three patients presented to their surgeon for ongoing care 10-20 years after primary metal-on-plastic hip arthroplasty with the same polished cobalt-chromium–cemented femoral stems (Heritage, Zimmer). Urine cobalt was elevated, and the patients had symptoms consistent with cobaltism. Quantitative-F16DG-PET-CT brain imaging was performed showing generalized and focal brain hypometabolism consistent with cobalt encephalopathy. At revision, all stems were well fixed and grossly corroded. At 1 year after revision, cobalturia and cognitive symptoms were resolved or improved. Mechanically assisted crevice corrosion at the polymethylmethacrylate interface is a complication of polished cobalt-chromium–cemented stems that can result in systemic cobalt exposure and toxic encephalopathy. Our cases had only minor periprosthetic symptoms. Patients implanted with polished cobalt-chromium–cemented stems warrant monitoring with urine cobalt. Patients with cobaltemia warrant an evaluation for toxic encephalopathy.

Purpose Imaging studies of cobalt toxicity from cobalt-chromium alloy arthroprosthetics have focused on the local intra-articular and peri-articular presentation from failing joint replacements. Most studies investigating neurological findings have been small case series focused on the clinical findings of memory loss, diminished executive function, tremor, hearing and vision loss, depression, and emotional lability. This study utilizes software-based quantitative analysis of brain metabolism to assess the degree of hypometabolism and areas of susceptibility, determine if a pattern of involvement exists, and measure reversibility of findings after prosthetic revision to cobalt-free appliances. Methods Over 48 months, 247 consecutive patients presenting to an orthopedic clinic with an arthroprosthetic joint containing any cobalt-chromium part were screened with whole blood and urine cobalt levels. A clinically validated inventory of 10 symptoms was obtained. Symptomatic patients with a blood cobalt level above 0.4 mcg/L or urine cobalt greater than 1 mcg/L underwent F-18 FDG PET brain imaging. Analysis was performed with FDA-approved quantitative brain analysis software with the pons as the reference region. Control group was the normal brain atlas within the software. Results Of the 247 consecutively screened patients, 123 had blood and urine cobalt levels above the threshold. The 69 scanned patients had statistically significant regional hypometabolism and higher symptoms inventory. Fifty-seven patients were retained in the study. Distribution of hypometabolism was in descending order: temporal, frontal, Broca’s areas, anterior cingulate, parietal, posterior cingulate, visual, sensorimotor, thalamic, and lastly caudate. Metal-on-metal (MoM) and metal-on-plastic (MoP) joint replacements produced similar patterns of hypometabolism. Of 15 patients with necessary revision surgery, 8 demonstrated improved metabolism when later re-scanned. Conclusion All scanned patients had regions of significant hypometabolism. Neurological toxicity from elevated systemic cobalt levels following arthroprosthetic joint replacement has a pattern of regional susceptibility similar to heavy metals and solvents, differing from classical dementias and may occur at blood and urine cobalt levels as low as 0.4 mcg/L and 1 mcg/L, respectively. Presently accepted thresholds for cobalt exposure and monitoring may need revision. Quantitative F-18 FDG PET brain imaging may aid in the decision process for treatment options and timing of possible medical versus surgical intervention.

Approximately 1 million metal-on-metal (MoM)6 hip prostheses have been implanted worldwide to alleviate pain, restore hip function, and improve overall quality of life. These implants contain femoral and acetabular bearing surfaces that are typically composed predominantly of cobalt (Co) and chromium (Cr). Although the majority of MoM hip replacements have been successful, multiple recent reports have documented markedly increased Co and Cr concentrations in the joint synovial fluid, periprosthetic tissue, blood, and even peripheral tissues of some patients with MoM hip prostheses. Consequently, concerns have been raised about the physiological consequences of metal release from MoM hip prostheses into the periprosthetic tissue and systemic circulation. Co and Cr concentrations in the serum and hip joint fluid correlate with the degree of MoM implant wear and are increased in individuals with an accumulation of metal debris in the periprosthetic tissue. Therefore, some scientists have suggested that Co and Cr concentrations be routinely measured during the management of patients with MoM hip prostheses. In this Q&A article, 4 experts provide their opinions on the use of MoM hip prostheses, the adverse biological consequences of metal release, and the clinical utility of Co and Cr measurements. They also discuss the methodology used to assess the concentration of these metal ions and provide insight into the many challenges associated with Co and Cr measurement. What are the advantages of MoM hip prostheses over other types of implants? Catherine Van Der Straeten: MoM was reintroduced as a bearing surface for hip arthroplasty to solve the problem of particle-induced osteolysis secondary to polyethylene wear. In vitro hip-simulator studies demonstrated much less volumetric wear and much smaller particles with MoM compared to metal-on-polyethylene (MoP). This finding was confirmed in vivo with high-carbon alloy MoM 28-mm and 32-mm total hip arthroplasty (THA). The use of larger-diameter femoral …

The medical literature is prone to overstating results, a condition not thoroughly recognized among policymakers. This article sets forth examples of potential problems with research integrity in the infectious disease literature. We describe articles that may be spun, categories lumped together in hopes of creating a significant effect (and sometimes an insignificant one), changes in metrics, and how trials may fail because of suboptimal interventions. When examined together, the examples show that the problems are widespread and illustrate the difficulty associated with interpreting medical research. The state of the current medical literature makes it of utmost importance that all sections of the manuscript are read, including associated letters to the editors and information on ClinicalTrials.gov before authors' recommendations are accepted.

Background Studies have suggested that cross-linked polyethylene bearings reduce wear rates from 40% to 100% compared with conventional polyethylene. However, the reduced mechanical properties of highly cross-linked polyethylene have the potential to be a limiting factor in device performance. We reviewed a series of retrieved acetabular liners with a fracture of the superior rim to assess the factors that played a role in their failure. Methods Four Longevity acetabular bearings, which had been retrieved from two patients after seven to twenty-seven months in vivo, were visually examined for clinical damage, were assessed with use of Fourier transform infrared spectroscopy to determine the level of oxidation, and were analyzed for mechanical properties and fracture surface characterization. Control data were obtained from never-implanted devices and from global reference ultra-high molecular weight polyethylene bar stock as an industry calibration material. Results All four retrieved liners demonstrated articular surface wear modes, which in most cases were rated as moderate, and none were rated as severe. All showed cracking or rim failure of the liner at the superior aspect along the groove in the polyethylene that engages the locking ring of the shell. The retrieved liners had no measurable oxidation, and the mechanical properties were comparable with those of never-implanted material. Conclusions There was no notable in vivo degradation of the retrieved liners. Important factors related to failure appear to be thin polyethylene at the cup rim, relatively vertical cup alignment, and the material properties of the highly cross-linked polyethylene that are decreased relative to conventional polyethylene. The critical dimension with respect to rim failure in modular liners appears to be the minimum thickness at the equatorial region. Clinical Relevance For a given implant design and loading, highly cross-linked polyethylene may be more susceptible to fatigue damage, such as rim cracking, than is conventional polyethylene. The potential for excess rim loading on thin polyethylene should be assessed carefully when the use of a cross-linked liner and a large femoral head is being considered, particularly in a cup with a more vertical abduction angle.

Objectives We sought to synthesize data on systemic arthroprosthetic cobaltism, a recently described syndrome that results from wear or corrosion of chrome-cobalt hip components. Methods We conducted a systematic literature review to identify all reported cases of systemic arthroprosthetic cobaltism. To assess the epidemiologic link between blood cobalt levels (B[Co]), we developed a symptom scoring tool that evaluated 9 different symptom categories and a category of medical utilization. Results We identified 25 patients reported between 2001 and 2014 with a substantial increase in case reports over the past 3 years. Symptoms were diverse and involved the hip (84%), cardiovascular system (60%), audiovestibular system (52%), peripheral motor-sensory system (48%), thyroid (48%), psychological functioning (32%), visual system (32%), and the hematological, oncological, or immune system (20%). The mean latency from implantation to presentation or revision was 41 months (range, 9–99 months). The mean B[Co] was 324 μg/L and 4 patients had levels less than 20 μg/L. The B[Co] but not blood chromium level was highly associated with a quantitative measure of overall symptom severity (r2, 0.81; P < 0.001). Mean B[Co] and symptom scores were substantially higher in patients with revisions of failed ceramic-on-ceramic prostheses than those with primary metal-on-metal prostheses. Conclusions Systemic arthroprosthetic cobaltism is an increasingly recognized complication of wear or corrosion of chrome-cobalt hip implants, may involve a large number of organ systems, and may occur with relatively low B[Co]. There is an urgent need to better define the overall scope of the problem and to develop screening and management strategies.

The article provides an analysis of 102 interventions in 93 periprosthetic fractures of the femur contributed by multiple surgeons predominately in community practice. The authors find that treatment of periprosthetic fracture of the femur is problematic. Success in terms of arthroplasty function and fracture treatment is difficult to achieve. Specific treatment recommendations are made based upon the success and failures of this survey.

Background A multisystem illness recently reported in recipients of the newest generation of metal-on-metal hip prostheses has been ascribed to toxic effects of cobalt and possibly chromium. Case report We present a case of insidiously developing neurologic illness that occurred in a physically active professional. Discussion This case illustrates the potential for a hip prosthesis to occultly impair safe functioning of aviators. Based on this case and others, we suggest modifications to aeromedical policy relating to waiver requests after hip replacement, including routine monitoring of serum cobalt and chromium levels in recipients of metal-on-metal hip prostheses. The evaluation of aviators having an elevated cobalt level is also discussed.

A retrospective review of 93 periprosthetic fractures and 102 periprosthetic fracture treatments showed that the type of prosthesis (cemented, ingrowth, Austin-Moore) and the presence of preexisting stress risers play a role in determining where the fractures occur. The site of fracture and the prefracture interface influence treatment of periprosthetic fractures. This study suggests that fractures associated with a loose interface, cemented or cementless, are best treated by removal of the prosthesis, reduction of the fracture, and insertion of a long stemmed prosthesis with additional fixation as needed. Treatment of a periprosthetic fracture associated with a stable prosthesis depends on the site of fracture. Fractures proximal to the tip of a fixed prosthesis usually can be treated nonoperatively or with limited internal fixation. Fractures at the tip of the prosthesis may be managed by revision or internal fixation, and fractures below the prosthesis can be managed operatively or nonoperatively.

Case: A 46-year-old man developed rapidly progressing Parkinson disease symptoms after metal-on-metal total hip arthroplasty, worsening to the extent that he underwent implantation of a right subthalamic deep brain stimulator (DBS). A serum cobalt level of 116 μg/L was measured shortly after DBS implantation, and revision arthroplasty was performed using ceramic-on-polyethylene bearings. After revision, the patient’s serum cobalt level fell below 1 μg/L, the Parkinson disease symptoms improved, and he reduced the DBS to its lowest setting. Explant analysis showed substantial material loss from the bearing surfaces of one hip. Conclusion: Future studies should evaluate the possible link between Parkinson disease symptoms and prosthesis wear-induced hypercobaltemia.

Early failure of metal-on-metal hip arthroplasties is a current concern because tissue damage resulting from periprosthetic metallosis can compromise subsequent revision arthroplasty1,2. The United Kingdom’s Medicines and Healthcare products Regulatory Agency has advised that patients with metal-on-metal implants who have pain, prosthetic malposition, or implants that are known to have excessive failure rates should be evaluated with the measurement of serum cobalt. A serum cobalt level of >7 μg/L indicates possible periprosthetic metallosis3,4. A normal serum cobalt level is 0.19 μg/L, and 95% of those who are unexposed to cobalt have a value of 1 μg/L indicates excessive cobalt exposure, and levels of >5 μg/L are considered toxic6. In excess, cobalt blocks cellular metabolism and can damage multiple organs. Cobalt poisoning (cobaltism) from beer additives, industrial exposure, or medicinal use is well known. Cobaltism can result in tinnitus, vertigo, deafness, blindness, optic nerve atrophy, convulsions, headaches, peripheral neuropathy, cardiomyopathy, and hypothyroidism7,8. Including the two cases in the present report, there are at least six case reports of cobaltism related to arthroplasty implants (arthroprosthetic cobaltism)7,9-12. These four patients presented with combinations of deafness, blindness, cognitive decline, headaches, convulsions, fatigue, weakness, peripheral neuropathy, heart failure, and hypothyroidism. All of these patients had periprosthetic metallosis due to wear of steel femoral heads by ceramic, and all had a serum cobalt level of >60 μg/L. The two …

The article provides an analysis of 102 interventions in 93 periprosthetic fractures of the femur contributed by multiple surgeons predominately in community practice. The authors find that treatment of periprosthetic fracture of the femur is problematic. Success in terms of arthroplasty function and fracture treatment is difficult to achieve. Specific treatment recommendations are made based upon the success and failures of this survey.

Boards of Directors of tax-exempt hospitals are increasingly struggling with whether to convert their facilities to for-profit status. Other than the traditional duties of loyalty and fair dealings imposed upon directors, there is currently little guidance to assure that boards obtain a fair price for the hospital in such conversions. The author provides recommendations to assure proper valuation.

Our initial experience with metal on metal hip implants1 was favourable. But several years later an uncharacteristically high proportion of patients developed progressive, unresolved, or new hip pain, some showing metal debris around the hip with tissue damage. Two patients had remarkably high cobalt concentrations, cognitive decline, cranial neuropathy, and early cardiomyopathy.2 We have just identified a fifth case of probable arthroprosthetic cobaltism …

Summary: The Resonant Frequency (RF) of the tibia is proportional to its stiffness. As a fractured tibia heals, its RF should increase. The RF was serially determined in 74 fractured tibias (205 examinations). These were subdivided by fracture location and fixation. Fast Fourier transform software generates the RF from data obtained with an instrumented impactor and accelerometer. The RF was normalized by expressing it as a ratio of the intact tibia. This ratio is called the tibial stiffness index (TSI). A 20 point tibial fracture score (TFS) quantitated the clinical and radiographic signs of healing. For each group the paired TSI and TFS were compared by regression analysis. Except for those fractures limited to the proximal fourth of the tibia, the TSI was found to correlate significantly (p=0.0001) with the TFS. Fractures without fixation and those with unlocked, unreamed tibial nails showed very significant correlation of TSI with TFS (p=0.0001). RF analysis was not useful in fractures with locked or reamed tibial nails. Examination of tibia with external fixation showed significant correlation (p=0.02) of the TSI with the TFS

Roentgenographic and anthropologic studies have shown a high incidence of spondylolysis in Eskimo populations. It is uncertain whether this is related to a genetic predisposition or to environmental factors. This study of recent roentgenograms and demographic characteristics of patients of the authors' institution notes a lower incidence in Eskimo populations than prior skeletal and roentgenographic studies. An attempt is made to quantitate the contributions of environmental factors and genetic predisposition. A higher incidence was found in full-blooded Eskimos than in part-blooded Eskimos. Rural-dwelling Eskimos had a higher incidence than urban-dwelling Eskimos. Eskimo subpopulations had a greater incidence than Athabascan Indians. Eskimos with spondylolysis were significantly more likely to have an associated spondylolisthesis than Athabascans with spondylolysis. Symptoms in the Eskimo population related to spondylolysis and associated spondylolisthesis rarely warrant surgical intervention.

Roentgenographic and anthropologic studies have shown a high incidence of spondylolysis in Eskimo populations. It is uncertain whether this is related to a genetic predisposition or to environmental factors. This study of recent roentgenograms and demographic characteristics of patients of the authors' institution notes a lower incidence in Eskimo populations than prior skeletal and roentgenographic studies. An attempt is made to quantitate the contributions of environmental factors and genetic predisposition. A higher incidence was found in full-blooded Eskimos than in part-blooded Eskimos. Rural-dwelling Eskimos had a higher incidence than urban-dwelling Eskimos. Eskimo subpopulations had a greater incidence than Athabascan Indians. Eskimos with spondylolysis were significantly more likely to have an associated spondylolisthesis than Athabascans with spondylolysis. Symptoms in the Eskimo population related to spondylolysis and associated spondylolisthesis rarely warrant surgical intervention.

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We have investigated certain aspects of the mechanism of synaptic transmission in a sympathetic ganglion by recording the action potentials in the inferior cardiac nerve of the cat while stimulating the preganglionic fibers to the stellate. This preparation has proved admirable for such a study because the long postganglionic nerve makes possible a careful investigation of the properties of the fibers whose response is used as a measure of the activity of the ganglion.The form of the action potential in the non-medullated fibers of the inferior cardiac nerve has been determined by recording the impulses in the nerve during direct excitation. It differs from that of medullated nerve in 2 respects which are important to this investigation. Because the conduction velocity is much less (0.4 to 1.1 meters per second) there is a marked spread of the spike potential due to temporal dispersion of impulses in the several fibers. This temporal dispersion and the large positive and negative after potentials which ar...

(1908). A Present Weakness in Teaching Geography. Journal of Geography: Vol. 6, No. 8, pp. 262-264.

The central portion of the human cornea yields, to any form of stimulation, only the sensation of pain. The reactions of laboratory mammals to stimulation of this field recapitulate those of the human. Therefore it may be inferred that the sensation evoked is likewise pain. The site thus offers the possibility of investigating the mechanism of this sense, unconfused by other modalities. To this end arrangements were made to amplify and record action potentials in the long ciliary nerves. In some experiments the active fibers of one of these nerves were reduced to 2 or 3. The animals, cats, were decerebrated, the second to sixth cranial nerves cut, and the ciliary ganglion removed. The stimulators employed included a set of von Frey needles (1/8 to 10 gm.), a corresponding set of hairs, a mechanical stimulator delivering prick of variable intensity, and blunt glass rods.The responses obtained from the cornea using these different instruments were essentially the same—trains of impulses of rapidly diminishi...

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