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Metabolic bone diseases comprise a wide spectrum. Of them, osteoporosis is the most frequent and the most commonly found in the spine, with a high impact on health care systems and on morbidity due to vertebral fractures (VFs).This article discusses state-of-the-art techniques on the imaging of metabolic bone diseases in the spine, from the well-established methods to the latest improvements, recent developments, and future perspectives.We review the classical features of involvement of metabolic conditions involving the spine. Then we analyze the different imaging techniques for the diagnosis, characterization, and monitoring of metabolic bone disease: dual-energy X-ray absorptiometry (DXA) and DXA-based fracture risk assessment applications or indexes, such as the geometric parameters, Bone Strain Index, and Trabecular Bone Score; quantitative computed tomography; and magnetic resonance and ultrasonography-based techniques, such as radiofrequency echographic multi spectrometry. We also describe the current possibilities of imaging to guide the treatment of VFs secondary to metabolic bone disease., Competing Interests: Jan Kirschke is Co-Founder of Bonescreen GmbH. All other authors declare no conflict of interest., (Thieme. All rights reserved.)

Metabolic bone diseases comprise a wide spectrum. Osteoporosis, the most frequent, characteristically involves the spine, with a high impact on health care systems and on the morbidity of patients due to the occurrence of vertebral fractures (VFs).Part II of this review completes an overview of state-of-the-art techniques on the imaging of metabolic bone diseases of the spine, focusing on specific populations and future perspectives. We address the relevance of diagnosis and current status on VF assessment and quantification. We also analyze the diagnostic techniques in the pediatric population and then review the assessment of body composition around the spine and its potential application. We conclude with a discussion of the future of osteoporosis screening, through opportunistic diagnosis and the application of artificial intelligence., Competing Interests: Jan Kirschke is Co-Founder of Bonescreen GmbH. All other authors declare no conflict of interest., (Thieme. All rights reserved.)

Related to fractures of and around the knee, inappropriate technical factors related to the surgery, severe comminution of the fracture, early overly arduous rehabilitation of the patient, and patient-related noncompliances may have the potential for the risk of inadequate fixation and other complications. Loss of fixation, malunion/nonunion, infection, arthritis, arthrofibrosis, and symptomatic hardware are among postsurgical complications that may necessitate further reconstructive techniques. In this review, complications that may be encountered in the postsurgical period of fractures involving the patella, supracondylar femur, and tibial plateau are described., Competing Interests: Disclosure The authors report no conflicts of interest in this work., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

The differential diagnosis between benign and malignant vertebral fractures is a common challenge in clinical practice, especially because osteoporotic fractures become more frequent within the aging population and many malignant diseases spread to the bone first, impacting bone integrity. This article reviews the morphological features and computed tomography (CT) and magnetic resonance imaging (MRI) imaging findings that help differentiate between benign and malignant fractures. Newer techniques such as MR-based diffusion-weighted imaging, dynamic contrast-enhanced MR, and chemical-shift imaging as well as hybrid techniques such as positron emission tomography-CT are also discussed briefly., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

For patients with malignant disease taking bisphosphonates and denosumab, the incidence of medication-related osteonecrosis of the jaw (MRONJ) is up to 15% in contrast to 0.01% in patients with osteoporosis. Clinical presentation of MRONJ extends from asymptomatic exposure of bone in 94% of patients to severe cases of mandibular fractures in a minority of 4.5%. The strongest risk factors for MRONJ are invasive dental procedures and dental infections. Advances in imaging provide more preoperation information compared with panoramic radiograph. Prevention strategies are the elimination of potential risk factors leading to invasive dental procedures and maintenance of good oral hygiene prior to the administration of antiresorptive agents. Management of MRONJ depends on the underlying disease, extent of the necrosis, and the presence of contributing therapy. Conservative therapies include topical anti-infective rinses and systemic antibiotic therapy. The most important part of surgical therapy is to remove the exposed and necrotic bone. Several options for defect closure are possible from local tissue flaps to microvascular free flap procedures. The development of MRONJ in conjunction with dental implants is a severe side effect and should be avoided if potentially harmful medication has already been administered., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

Soft tissue sarcomas are rare, but early, accurate diagnosis with subsequent appropriate treatment is crucial for the clinical outcome. The ESSR guidelines are intended to help radiologists in their decision-making and support discussion among clinicians who deal with patients with suspected or proven soft tissue tumors. Potentially malignant lesions recognized by ultrasound should be referred for magnetic resonance imaging (MRI), which also serves as a preoperative local staging modality, with specific technical requirements and mandatory radiological report elements. Radiography may add information about matrix calcification and osseous involvement. Indeterminate lesions, or lesions in which therapy is dependent on histology results, should be biopsied. For biopsy, we strongly recommend referral to a specialist sarcoma center, where an interdisciplinary tumor group, with a specialized pathologist, radiologist, and the surgeon are involved. In sarcoma, a CT scan of the chest is mandatory. Additional staging modalities are entity-specific. There are no evidence-based recommendations for routine follow-up in surgically treated sarcomas. However, we would recommend regular follow-up with intervals dependent on tumor grade, for 10 years after the initial diagnosis., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

This review article focuses on occurrence, imaging, and differential diagnosis of insufficiency fractures. Prevalence and the most common sites of insufficiency fractures and their clinical implications are discussed. Insufficiency fractures are due to normal stress exerted on weakened bone. Most commonly postmenopausal osteoporosis is the cause for insufficiency fractures. Additional conditions affecting bone turnover include osteomalacia, chronic renal failure, and high-dose corticosteroid therapy. It is a challenge for the radiologist to detect and diagnose insufficiency fractures as well as to differentiate them from malignant fractures. Radiographs are the basic modality used for screening of insufficiency fractures, yet depending on the location of the fractures, sensitivity is limited. Magnetic resonance imaging is a very sensitive tool to visualize bone marrow abnormalities associated with insufficiency fractures and allows differentiation of benign versus malignant fractures. Thin section multidetector computed tomography (CT) depicts subtle fracture lines allowing direct visualization of cortical and trabecular bone. Dedicated Mikro-CTs (Xtreme-CT) can detect subtle fractures reaching an in-plane resolution of 80 μm. Bone scintigraphy still plays a role in detecting fractures, with good sensitivity but unsatisfactory specificity. Positron emission tomography-CT with hybrid-scanners has been the upcoming modality for the differentiation of benign from malignant fractures. Bone densitometry and clinical fracture history may determine the future risk of possible insufficiency fractures., (© Thieme Medical Publishers.)