Imaging of Non-Neoplastic Bone Marrow Disorders

Bone marrow is one of the largest organs in the human body, and as such it is afflicted by many primary and secondary disorders. Magnetic resonance (MR) imaging has proved to be the method of choice to image the bone marrow. A deep knowledge of the normal pattern of maturation, the value of each pulse sequence including the newest ones (diffusion/perfusion), the use of conventional and novel contrast media, and the clinical impact of the various MR imaging findings are important in clinical praxis.

A previous issue of Seminars published in 2009 (guest editor Andrea Baur-Melnyk) addressed neoplastic bone marrow disorders. In the present issue, consisting of 10 articles, renowned experts on the field discuss non-neoplastic bone marrow disorders.

The first article, by Navas and Kassarjian, deals with the bone marrow changes in stress injuries that represent a common finding at all levels of athletic involvement. The authors offer an updated review of the pathophysiology, MR imaging findings, and clinical impact of stress injuries, with an emphasis on how to discriminate them from normal bone marrow changes commonly seen in athletes.

The next article, by Krestan et al, discusses bone marrow changes secondary to insufficiency fractures. These fractures become more common among the aging population and often create diagnostic problems. The article discusses the prevalence, common sites of involvement, clinical implications, and proper imaging algorithm.

Steinbach and Suh's article reviews the MR imaging findings of various nontraumatic causes of bone marrow edema around the knee joint, including osteonecrosis, bone marrow edema syndrome, arthropathy, infection, Paget's disease, and marrow replacement disorders.

Chang et al review bone marrow changes seen following cartilage repair procedures. The variable treatment options currently available create a spectrum of MR imaging findings that may or may not be clinically relevant. Radiologists should be able to interpret postoperative imaging studies and therefore need to know the various surgical procedures. In this respect, the authors provide a practical guide to imaging the postoperative cartilage.

In the aging population MR imaging findings associated with osteoarthritis are also commonly seen in other disorders, such as insufficiency fractures. Link and Li review bone marrow changes in osteoarthritis, discuss their histological basis and clinical significance, and present the differential diagnosis.

Recognition and understanding of lesions that cause low signal on T1-weighted images is an important tool when interpreting MR images. Gina Allen presents the list of causes that create these dark areas and discusses the proper imaging algorithm to understand their nature and narrow the differential diagnosis.

Toledano et al present a practical imaging approach of the diabetic foot. Bone marrow changes with MR imaging are used to differentiate osteomyelitis, reactive edema, neuroarthropathy, and superinfected neuropathic joint.

Chronic anemias comprise a heterogeneous group of disorders and result in bone marrow changes. Martinoli et al present the musculoskeletal manifestations that may correlate with the primary disorder, but also with specific complications either from the disease itself or treatment.

Nontraumatic avascular necrosis of the hip is a devastating disorder affecting young patients, and, despite treatment, it normally follows a progressive course toward a destructive osteoarthropathy. Pain in these patients is a challenging clinical problem. The article by Karantanas and Drakonaki reviews the established and evolving role of MR imaging in the diagnosis and management of avascular necrosis of the hip including the postoperative status.

The final article in this issue, by Maas et al, focuses on the increasing role of imaging in the management of patients with inborn errors of metabolism. More demand for biomarkers in these patients with rare diseases is associated with expensive enzyme replacement therapies. MR imaging may serve as a biomarker. The authors discuss the current need for imaging and raise the issue of the potential for metabolic radiology to evolve as a subspecialty.

I would like to thank the editors for giving me the opportunity to serve as guest editor for this clinically important topic. I am also grateful to the authors for their cooperation and excellent contributions to this issue of Seminars in Musculoskeletal Radiology.