Adult Acquired Flatfoot Deformity: Anatomy, Biomechanics, Staging, and Imaging Findings.

Adult acquired flatfoot deformity (AAFD) is a common disorder that typically affects middle-aged and elderly women, resulting in foot pain, malalignment, and loss of function. The disorder is initiated most commonly by degeneration of the posterior tibialis tendon (PTT), which normally functions to maintain the talonavicular joint at the apex of the three arches of the foot. PTT degeneration encompasses tenosynovitis, tendinosis, tendon elongation, and tendon tearing. The malaligned foot is initially flexible but becomes rigid and constant as the disorder progresses. Tendon dysfunction commonly leads to secondary damage of the spring ligament and talocalcaneal ligaments and may be associated with injury to the deltoid ligament, plantar fascia, and other soft-tissue structures. Failure of multiple stabilizers appears to be necessary for development of the characteristic planovalgus deformity of AAFD, with a depressed plantar-flexed talus bone, hindfoot and/or midfoot valgus, and an everted flattened forefoot. AAFD also leads to gait dysfunction as the foot is unable to change shape and function adequately to accommodate the various phases of gait, which require multiple rapid transitions in foot position and tone for effective ambulation. The four-tier staging system for AAFD emphasizes physical examination findings and metrics of foot malalignment. Mild disease is managed conservatively, but surgical procedures directed at the soft tissues and/or bones become necessary and progressively more invasive as the disease progresses. Although much has been written about the imaging findings of AAFD, this article emphasizes the anatomy and function of the foot's stabilizing structures to help the radiologist better understand this disabling disorder. Online supplemental material is available for this article. ©RSNA, 2019.

Layered Approach to the Anterior Knee: Normal Anatomy and Disorders Associated with Anterior Knee Pain.

Anterior knee pain is a common complaint that can be caused by a wide spectrum of disorders affecting the many varied tissues at the anterior knee. The anatomy and pathologic conditions of the anterior knee can be approached systematically by organizing the region into four layers: (a) superficial layer of fat, fascia, and bursae; (b) functional layer composed of the extensor mechanism and patellar stabilizers; (c) intracapsular extrasynovial layer containing the fat pads; and (d) intra-articular layer. The superficial layer is composed of delicate tissues that are predisposed to blunt and penetrating trauma, irritation, and infection. The extensor mechanism forms the functional layer, is responsible for knee extension and patellar stabilization, and is engaged in repetitive movements; overuse disorders dominate in this layer. The fat pads of the anterior knee are discussed collectively as an extracapsular extrasynovial layer, functioning to improve congruence and protect the articular surfaces during motion. Diseases involving the fat pads can be primary or secondary to pathologic conditions in the rest of the joint. The synovial lining and cartilage surface are in the fourth and final intra-articular layer; pathologic conditions are centered around arthritides and internal derangement. Symptoms in the anterior knee may be due to conditions affecting one or more of these interrelated layers. ©RSNA, 2018.

MR Imaging of Atraumatic Muscle Disorders.

Atraumatic disorders of skeletal muscles include congenital variants; inherited myopathies; acquired inflammatory, infectious, or ischemic disorders; neoplastic diseases; and conditions leading to muscle atrophy. These have overlapping appearances at magnetic resonance (MR) imaging and are challenging for the radiologist to differentiate. The authors organize muscle disorders into four MR imaging patterns: (a) abnormal anatomy with normal signal intensity, (b) edema/inflammation, (c) mass, and (d) atrophy, highlighting each of their key clinical and imaging findings. Anatomic muscle variants, while common, do not produce signal intensity alterations and therefore are easily overlooked. Muscle edema is the most common pattern but is nonspecific, with a broad differential diagnosis. Autoimmune, paraneoplastic, and drug-induced myositis tend to be symmetric, whereas infection, radiation-induced injury, and myonecrosis are focal asymmetric processes. Architectural distortion in the setting of muscle edema suggests one of these latter processes. Intramuscular masses include primary neoplasms, metastases, and several benign masslike lesions that simulate malignancy. Some lesions, such as lipomas, low-flow vascular malformations, fibromatoses, and subacute hematomas, are distinctive, but many intramuscular masses ultimately require a biopsy for definitive diagnosis. Atrophy is the irreversible end result of any muscle disease of sufficient severity and is the dominant finding in disorders such as the muscular dystrophies, denervation myopathy, and sarcopenia. This imaging-based classification, in correlation with clinical and laboratory data, will aid the radiologist in interpreting MR imaging findings in patients with atraumatic muscle disorders. ©RSNA, 2018.

MR Imaging of Muscle Trauma: Anatomy, Biomechanics, Pathophysiology, and Imaging Appearance.

Muscle is an important component of the muscle-tendon-bone unit, driving skeletal motion through contractions that alter the length of the muscle. The muscle and myotendinous junction (MTJ) are most commonly injured in the young adult, as a result of indirect mechanisms such as overuse or stretching, direct impact (penetrating or nonpenetrating), or dysfunction of the supporting connective tissues. Magnetic resonance (MR) imaging is widely used for assessment of muscle injuries. This review illustrates the MR imaging appearance of a broad spectrum of acute, subacute, and chronic traumatic lesions of muscle, highlighting the pathophysiology, biomechanics, and anatomic considerations underlying these lesions. Concentric (shortening) contractions are more powerful, but it is eccentric (lengthening) contractions that produce the greatest muscle tension, leading to indirect injuries such as delayed-onset muscle soreness (DOMS) and muscle strain. Strain is the most commonly encountered muscle injury and is characteristically located at the MTJ, where maximal stress accumulates during eccentric exercise. The risk of strain varies among muscles based on their fiber composition, size, length, and architecture, with pennate muscles being at highest risk. Direct impact to muscle results in laceration or contusion, often accompanied by intramuscular interstitial hemorrhage and hematoma. Disorders related to the muscle's collagen framework include compartment syndrome, which is related to acute or episodic increases in pressure, and muscle herniation through anatomic defects in the overlying fascia. The healing response after muscle trauma can result in regeneration, degeneration with fibrosis and fatty replacement, or disordered tissue proliferation as seen in myositis ossificans. In athletes, accurate grading of the severity and precise location of injury is necessary to guide rehabilitation planning to prevent reinjury and ensure adequate healing. In elite athletes, MR imaging grading of muscle trauma plays an increasingly important role in recently developed comprehensive grading systems that are replacing the imprecise three-grade injury classification system currently used. ©RSNA, 2017.

Sarcoma sinovial monofásico de tipo fibroblástico. Evaluación diagnóstica por RM y postratamiento mediante ADC: Presentación de un caso / Monophasic Fibroblastic Synovial Sarcoma. Diagnostic and Post-Treatment Assessment by MRI and ADC: Case Report

El sarcoma sinovial representa entre el 2 al 10 % de todas las malignidades primarias de tejidos blandos, situándose en el cuarto lugar en frecuencia de los sarcomas de tejidos blandos. Es una neoplasia clasificada por la WHO (World Health Organization) bajo la categoría de tumores de diferenciación incierta, considerándose una malignidad entre intermedio y alto grado. El tratamiento estándar es la escisión quirúrgica, sin embargo, por su alta recurrencia y en los casos en que se asocia a metástasis o márgenes positivos después de la resección, se han planteado otros tratamientos como la quimio y radioterapia. La imaginología juega un papel importante en el diagnóstico, la estadificación y evaluación de la respuesta al tratamiento. Nuevas técnicas como el uso de difusión y mapas de ADC (Apparent Diffusion Coefficient, o coeficiente de difusión aparente) en resonancia magnética (RM) son útiles para evaluar las lesiones tumorales y la respuesta al tratamiento. En este artículo se presenta el caso de un paciente con un sarcoma sinovial monofásico, el diagnóstico por imágenes y evaluación del tratamiento mediante técnicas avanzadas de resonancia magnética como la difusión

Synovial sarcomas represent 2 to 10% of all the primary tissue malignancies and occupy the fourth place in the list of most common soft tissue sarcomas. According to the World Health Organization (WHO), this neoplasm is classified under the category of tumors of uncertain differentiation and is considered an intermediate to high-grade malignancy. Although the standard treatment is surgical excision, alternative treatments such as radiotherapy and chemotherapy have been proposed due to its high rate of recurrence in cases when it is associated with metastasis or positive resection margins. Imaging plays a key role in the diagnosis, staging and assessment of treatment of this disease. New techniques in Magnetic Resonance Imaging such as diffusion and Apparent Diffusion Coefficient (ADC) mapping are useful to further characterize these neoplastic lesions and to assess treatment response. In this article we present a patient with monophasic synovial sarcoma in which the use of these new imaging techniques was essential for the diagnosis and evaluation post-treatment.

Aortitis con bacteriemia por Streptococcus equi zooepidemicus / Aortitis with bacteriemia by Streptococcus equi zooepidemicus

La infección por Streptococcus equi zooepidemicus es propia de animales y en el hombre es generalmente accidental con reporte de pocos casos. Presentamos el caso de un hombre de 56 años, matarife, con cuadro de dolor abdominal, documentándose por TAC y en cirugía dilatación aneurismática de la aorta por debajo de las renales, con colección purulenta y ulceración del vaso de donde se aisló Streptococcus equi zooepidemicus, aislándose también la bacteria de los hemocultivos.