Gary Mlady

Iron-Based Superparamagnetic Nanoparticle Contrast Agents for MRI of Infection and Inflammation

OBJECTIVE. In this article, we summarize the progress to date on the use of superparamagnetic iron oxide nanoparticles (SPIONs) as contrast agents for MRI of inflammatory processes. CONCLUSION. Phagocytosis by macrophages of injected SPIONs results in a prolonged shortening of both T2 and T2* leading to hypointensity of macrophage-infiltrated tissues in contrast-enhanced MR images. SPIONs as contrast agents are therefore useful for the in vivo MRI detection of macrophage infiltration, and there is substantial research and clinical interest in the use of SPION-based contrast agents for MRI of infection and inflammation. This technique has been used to identify active infection in patients with septic arthritis and osteomyelitis; importantly, the MRI signal intensity of the tissue has been found to return to its unenhanced value on successful treatment of the infection. In SPION contrast-enhanced MRI of vascular inflammation, animal studies have shown decreased macrophage uptake in atherosclerotic plaques after treatment with statin drugs. Human studies have shown that both coronary and carotid plaques that take up SPIONs are more prone to rupture and that abdominal aneurysms with increased SPION uptake are more likely to grow. Studies of patients with multiple sclerosis suggest that MRI using SPIONs may have increased sensitivity over gadolinium for plaque detection. Finally, SPIONs have enabled the tracking and imaging of transplanted stem cells in a recipient host.

Extensor Hallucis Capsularis: Frequency and Identification on MRI

Background: The extensor hallucis capsularis (EHC) is the most common name given to the accessory tendon sporadically seen medial to the extensor hallucis longus (EHL). We performed cadaver dissections and MRI evaluation to determine the frequency of its occurrence, the pattern of its origin and insertion, and its potential suitability as tendon graft. Methods: The EHC was examined by dissection in 81 cadaver feet. Physical parameters pertaining to EHC size and location were recorded. MRI was performed on six cadaver legs to determine if the EHC can be identified radiographically. MRI images were evaluated independently by a foot and ankle specialist and a radiologist. Results: The EHC was present in 71 (88%) of the specimens. It originated from the EHL tendon or muscle in 93% and inserted into the first metatarsophalangeal joint capsule in 99% of cases. All EHC tendons were less than or equal to 4 mm in width; only 16% were more than 2 mm wide. Correct prediction of the presence or absence of EHC by MRI varied according to EHC width: two of two in tendons more than 2 mm, five of eight in tendons 1 to 2 mm, and zero of two in tendons 1 mm or less. Conclusion: Up to 14% of the population may have an EHC tendon suitable for grafting in reconstructive surgeries, particularly surgeries related to hallux dysfunction. MRI may have a role in the preoperative identification of the EHC.

Medial collateral ligament tear entrapped within a proximal tibial physeal separation: imaging findings and operative reduction

Entrapped soft tissues such as periosteum and tendons have been described within joints and physeal fractures in the literature and frequently result in irreducible fractures and posttraumatic growth disturbances. We believe this case represents a novel presentation of acute, preoperative, magnetic resonance (MR) imaging diagnosis of a torn medial collateral ligament entrapped within a proximal tibial physeal separation. This case is presented with MR imaging and operative correlation of the findings.

Ferumoxytol negatively enhances T2 -weighted MRI of pedal osteomyelitis in vivo.

The current standard-of-care imaging technique for the diagnosis of osteomyelitis is gadolinium-contrasted MRI (Gd-MRI). However, Gd-MRI has imperfect specificity for osteomyelitis because signal enhancement also occurs in the presence of Charcot joints and other forms of sterile inflammation. The diagnosis of osteomyelitis has substantial clinical implications; there is a 15–25% lifetime risk of diabetic foot infections in diabetic patients. These infections are the basis for more than half of the nontraumatic lower extremity amputations performed. Furthermore, the intravenous infusion of gadolinium salts in the presence of chronic kidney disease (CKD) can lead to incurable nephrogenic systemic fibrosis. Recent research has suggested that superparamagnetic iron oxide nanoparticles (SPIONs) present an attractive alternative to gadolinium-based contrast agents for the MRI-aided diagnosis of inflammation and infection. SPIONs are taken up by macrophages and give rise to negative T2-weighted MRI contrast (darkening) in areas of inflammation. Preclinical and clinical studies suggest that iron oxide nanoparticle-contrasted MRI may be superior to gadolinium in distinguishing active osteomyelitis from other sterile forms of inflammation. Ferumoxytol is a SPION preparation that has been approved by the Food and Drug Administration in the United States for intravenous use as an iron replacement drug for patients with CKD. Unlike gadolinium-containing preparations, ferumoxytol may be safely used in patients who have kidney disease, a common comorbidity in diabetic patients with osteomyelitis. The purpose of this pilot study is to determine if ferumoxytol given to patients with clinically suspected osteomyelitis would cause negative T2weighted MRI contrast changes. Materials and Methods

Finite element analysis of plate-screw systems used in medial opening wedge proximal tibial osteotomies

This study investigates, through finite-element analysis, different plate-screw fixation systems used for medial opening proximal tibial osteotomies (locking or non-locking with or without a medial spacer). Sulzer stainless steel non-locking without spacer, Synthes titanium locking without spacer, Smith and Nephew custom titanium locking with a wedge spacer and Arthrex stainless steel non-locking with a wedge spacer fixation systems were modelled and compared. All fixation systems were tested under static loading of 889 N applied evenly over the proximal tibia particular surface. The areas of highest stress experienced in the bone and the plate/screw interface were analysed. Tendency of the osteotomy wedge to close under loading for each fixation system was analysed. The numerical results suggest the titanium locking plate with wedge spacer block outperforms the others by achieving lower stresses (incurred by the fixation system and bone) and loss of correction. Locking screw mechanisms and wedge spacer blocks appear advantageous.

Segmentation of knee joints in x-ray images using decomposition-based sweeping and graph search

Plain radiography (i.e., X-ray imaging) provides an effective and economical imaging modality for diagnosing knee illnesses and injuries. Automatically segmenting and analyzing knee radiographs is a challenging problem. In this paper, we present a new approach for accurately segmenting the knee joint in X-ray images. We first use the Gaussian high-pass filter to remove homogeneous regions which are unlikely to appear on bone contours. We then presegment the bones and develop a novel decomposition-based sweeping algorithm for extracting bone contour topology from the filtered skeletonized images. Our sweeping algorithm decomposes the bone structures into several relatively simple components and deals with each component separately based on its geometric characteristics using a sweeping strategy. Utilizing the presegmentation, we construct a graph to model the bone topology and apply an optimal graph search algorithm to optimize the segmentation results (with respect to our cost function defined on the bone boundaries). Our segmented results match well with the manual tracing results by radiologists. Our segmentation approach can be a valuable tool for assisting radiologists and X-ray technologists in clinical practice and training.

Psychosocial and demographic factors influencing pain scores of patients with knee osteoarthritis

Background Pain levels in patients with osteoarthritis (OA) of the knee are commonly assessed by using a numeric scoring system, but results may be influenced by factors other than the patient’s actual physical discomfort or disease severity, including psychosocial and demographic variables. We examined the possible relation between knee-pain scores and several psychosocial, sociodemographic, disease, and treatment variables in 355 patients with knee OA. Methods The pain-evaluation instrument was a 0- to 10-point rating scale. Data obtained retrospectively from the patients’ medical records were demographic characteristics, body mass index (BMI), concomitant disorders, illicit and prescription drug use, alcohol use, smoking, knee OA treatment, and severity of knee OA indicated by Kellgren-Lawrence (KL) radiographic grade. Univariate and multivariate analyses were performed to determine whether these variables correlated with reported pain scores. Results On univariate analysis, higher pain scores were significantly associated with Native American or Hispanic ethnicity; a higher BMI; current prescription for an opioid, antidepressant, or gabapentinoid medication; depression; diabetes mellitus; fibromyalgia; illicit drug use; lack of health insurance; smoking; previous knee injection; and recommendation by the clinician that the patient undergo knee surgery. Neither the patient’s sex nor the KL grade showed a correlation. On multivariate analysis, depression, current opioid prescription, and Native American or Hispanic ethnicity retained a significant association with higher pain scores. Conclusions and implications Our results in a large, ethnically diverse group of patients with knee OA suggest that psychosocial and sociodemographic factors may be important determinants of pain levels reported by patients with knee OA.