Posteromedial Corner of the Knee: The Neglected Corner.

The posteromedial corner of the knee (PMC) is an important anatomic structure that is easily seen but often overlooked on magnetic resonance (MR) images. Whereas the posterolateral corner has been referred to as the "dark side of the knee" by some authors owing to widespread lack of knowledge of its complex anatomy, even less is written about the PMC; yet it is as important as the posterolateral corner in multiligament injuries of the knee. The PMC lies between the posterior margin of the longitudinal fibers of the superficial medial collateral ligament (MCL) and the medial border of the posterior cruciate ligament (PCL). The anatomy of the PMC can be complex and the literature describing it can be confusing, at times oversimplifying it and at other times adding unnecessary complexity. Its most important structures, however, can be described more simply as five major components, and can be better shown with illustrations that emphasize the anatomic distinctions. Injuries to the PMC are important to recognize, as disruption of the supporting structures can cause anteromedial rotational instability (AMRI). Isolated PMC injuries are rare; most occur in conjunction with injuries to other important stabilizing knee structures such as the anterior cruciate ligament (ACL) and PCL. Unrecognized and unaddressed injury of the PMC is one of the causes of ACL and PCL graft failures. Recognition of PMC injuries is critical, as the diagnosis will often change or require surgical management.

Coronal plane fracture of the femoral condyles: anatomy, injury patterns, and approach to management of the Hoffa fragment.

OBJECTIVE: The purpose of this article is to provide a review of coronal fractures of the femoral condyles, known as Hoffa fractures. This includes a review of the normal anatomy of the femoral condyles, examples of the injury, and postoperative imaging findings after surgical treatments. CONCLUSIONS: Knowledge of anatomy with related pathology, orthopedic trends, imaging findings, and complications, is important in assessing Hoffa fractures.

Hand infections: anatomy, types and spread of infection, imaging findings, and treatment options.

Infections of the hand are common, particularly in immunocompromised patients, and can lead to significant morbidity, including amputation, if not treated properly. Hand infection can spread far and wide from the original site of inoculation through interconnections between the synovium-lined and nonsynovial potential spaces. Because surgery is the mainstay of treatment, knowledge of the pertinent anatomy is imperative for accurately describing the presence, location, and extent of infection. The authors review the pertinent anatomy of the spaces of the hand and describe different types of infection-including cellulitis, necrotizing fasciitis, paronychia, felon, pyogenic flexor tenosynovitis, deep space infections, septic arthritis, and osteomyelitis-and common causative organisms of these infections. They also describe various modes of spread; the common radiologic appearances of hand infections, with emphasis on findings at magnetic resonance imaging and ultrasonography; and the role of radiology in the management of these infections, along with a brief overview of treatment options.

Madura foot: two case reports, review of the literature, and new developments with clinical correlation.

"Madura foot" or pedal mycetoma is a rare destructive infection of the skin and subcutaneous tissues of the foot, progressing to involve muscle and bone. The infection can be caused by both bacteria and fungi. Infection typically follows traumatic implantation of bacteria or fungal spores, which are present in soil or on plant material. Clinically, this entity can be difficult to diagnose and can have an indolent and progressive course. Early diagnosis is important to prevent patient morbidity and mortality. We present two cases of pedal mycetoma, review the literature, review new developments in diagnosis, and discuss magnetic resonance imaging (MRI) features of this unusual entity.

Giant cell tumor of bone: review, mimics, and new developments in treatment.

Giant cell tumor (GCT) of bone is generally a benign tumor composed of mononuclear stromal cells and characteristic multinucleated giant cells that exhibit osteoclastic activity. It usually develops in long bones but can occur in unusual locations. The typical appearance is a lytic lesion with a well-defined but nonsclerotic margin that is eccentric in location, extends near the articular surface, and occurs in patients with closed physes. However, GCT may have aggressive features, including cortical expansion or destruction with a soft-tissue component. Fluid-fluid levels, consistent with secondary formation of aneurysmal bone cysts, are seen in 14% of cases. GCT can mimic or be mimicked by other benign or malignant lesions at both radiologic evaluation and histologic analysis. Rarely, GCT is associated with histologically benign lung metastases or undergoes malignant degeneration. In the past, the mainstay of treatment was surgical, primarily consisting of curettage with cement placement, with recurrence rates of 15%-25%. Recurrence is suggested by development of progressive lucency at the cement-bone interface. Other complications include pathologic fracture and postoperative infection. Denosumab, a monoclonal antibody that targets the osteoclastic activity of GCT, has produced 90% tumor necrosis in early studies, results indicative of promise as a potential adjuvant therapy.

Lipoma arborescens of the biceps tendon sheath.

Lipoma arborescens, described as lipomatous infiltration and distention of synovial villi resulting in a frond-like appearance, most frequently affects the suprapatellar recess of the knee. While there have been reports of this entity involving the upper extremity joints, bursa, and tendon sheaths, we present the first reported case of lipoma arborescens isolated to the biceps tendon sheath. We describe imaging and histologic findings with clinical correlation.

Transient lateral patellar dislocation: review of imaging findings, patellofemoral anatomy, and treatment options.

Transient patellar dislocation is a common sports-related injury in young adults. Although patients often present to the emergency department with acute knee pain and hemarthrosis, spontaneous reduction frequently occurs, and half of cases are unsuspected clinically. Characteristic magnetic resonance imaging (MRI) findings often lead to the diagnosis. The purpose of this review is to illustrate the MRI findings of lateral patellar dislocation and concomitant injuries, such as kissing contusions of the medial patella and lateral femoral condyle; osteochondral and avulsion fractures; and injuries of the medial patellofemoral ligament/retinacular complex. This article will also briefly review patellofemoral anatomy and passive, active, and static stabilizers. Predisposing factors for patellar instability, including trochlear dysplasia, patella alta, and lateralization of the patella or tibial tuberosity and their relevant measurements will also be highlighted. Treatment options, including surgery, such as medial patellofemoral ligament reconstruction, tibial tuberosity transfer, and trochleoplasty, and their postoperative imaging appearances will also be discussed.

Cruciate ligament avulsion fractures: anatomy, biomechanics, injury patterns, and approach to management.

Injury to the ACL or PCL of the knee most commonly involves a tear of the collagenous fibers of the ligament. Less frequently, a cruciate ligament injury involves an avulsion fracture at the origin or insertion of the ligament, usually from the insertion site on the tibial surface. Avulsion fractures of the cruciate ligaments are important, as they can be identified on radiographs, allowing a specific diagnosis. Although more common in children, when they occur in adults, they are more commonly associated with other injuries. The treatment of cruciate ligament avulsion fractures is different than the treatment of intrasubstance tears of the cruciate ligaments. These injuries can be treated conservatively or surgically with good outcomes. Recently arthroscopic fixation of these injuries with various fixation devices has become more frequent. Treatment largely depends on the type of fracture, particularly, the size, displacement, comminution, and orientation of the avulsed fracture fragment, in addition to the integrity of the attached cruciate ligament. This review article covers the anatomy and biomechanics of the cruciate ligaments, their injury patterns, and approach to management.

Sclerosing bone dysplasias: review and differentiation from other causes of osteosclerosis.

Sclerosing bone dysplasias are skeletal abnormalities of varying severity with a wide range of radiologic, clinical, and genetic features. Hereditary sclerosing bone dysplasias result from some disturbance in the pathways involved in osteoblast or osteoclast regulation, leading to abnormal accumulation of bone. Several genes have been discovered that, when disrupted, result in specific types of hereditary sclerosing bone dysplasia (osteopetrosis, pyknodysostosis, osteopoikilosis, osteopathia striata, progressive diaphyseal dysplasia, hereditary multiple diaphyseal sclerosis, hyperostosis corticalis generalisata), many of which exhibit similar pathologic mechanisms involving endochondral or intramembranous ossification and some of which share similar underlying genetic defects. Nonhereditary dysplasias include intramedullary osteosclerosis, melorheostosis, and overlap syndromes, whereas acquired syndromes with increased bone density, which may simulate sclerosing bone dysplasias, include osteoblastic metastases, Paget disease of bone, Erdheim-Chester disease, myelofibrosis, and sickle cell disease. Knowledge of the radiologic appearances, distribution, and associated clinical findings of hereditary and nonhereditary sclerosing bone dysplasias and acquired syndromes with increased bone density is crucial for accurate diagnosis.

Imaging of intraarticular masses.

Intraarticular masses can be classified as noninfectious synovial proliferative processes (lipoma arborescens, synovial osteochondromatosis, pigmented villonodular synovitis, rheumatoid arthritis), infectious granulomatous diseases (tuberculous arthritis, coccidioidomycosis arthritis), deposition diseases (gout, amyloid arthropathy), vascular malformations (synovial hemangioma, arteriovenous malformations), malignancies (synovial chondrosarcoma, synovial sarcoma, synovial metastases), and miscellaneous (cyclops lesion). Knowledge of articular anatomy aids the radiologist in localizing masses to the joint space. Some joints have complex anatomy with contiguous or adjacent bursae, recesses, and tendinous connections from which masses may originate or into which masses may extend. Many of the diseases causing intraarticular masses have specific imaging characteristics, especially on magnetic resonance images, and knowledge of these characteristics will allow for a more confident diagnosis.

Turf toe and sesamoiditis: what the radiologist needs to know.

The first metatarsophalangeal (MTP) joint complex is a critical weight-bearing structure important to biomechanics. An acute dorsiflexion injury, named "turf toe," is common among American football and soccer players. "Sesamoiditis" is a name often given for pain arising from the hallux sesamoids in the absence of acute trauma, and may result from a variety of causes. The first MTP joint complex can also be affected by degenerative or inflammatory arthritis, infarct, and infection. This review article will cover the anatomy and biomechanics of the first MTP joint complex, its patterns of injury and pathology, imaging techniques, and management.

Infectious spondylitis.

Infection of the spine is a rare but serious cause of back pain. Conventional radiographs remain the initial screening procedure. Typically two adjacent vertebral bodies and the intervening disk space are affected. Early in the course of the disease, radiographs may be normal or nondiagnostic. Magnetic resonance imaging or radionuclide bone scan will establish pathology centered in the vertebral body. Because of the ability to image soft tissues, magnetic resonance imaging is particularly helpful in detecting paravertebral and extradural abscesses. Four other conditions may mimic infectious spondylitis: degenerative disk disease associated with Modic type 1 changes, pseudoarthrosis in ankylosing spondylitis, dialysis spondyloarthropathy, and neuropathic spondyloarthropathy. Advanced imaging studies in combination with radiographs and clinical information are essential in determining the correct diagnosis.

Musculoskeletal manifestations of endocrine disorders.

Endocrine disorders can lead to disturbances in numerous systems within the body, including the musculoskeletal system. Radiological evaluation of these conditions can demonstrate typical appearances of the bones and soft tissues. Knowledge of these patterns can allow the radiologist to suggest a diagnosis that may not be clinically apparent. This review will highlight the typical musculoskeletal findings of acromegaly, hypercortisolism, hyperthyroidism, hypothyroidism, hyperparathyroidism, pseudo- and pseudopseudohypoparathyroidism, and diabetes mellitus. The radiological manifestations of each of these endocrine disorders, along with a brief discussion of the pathophysiology and clinical implications, will be discussed.

The early diagnosis of sacroiliac joint infections in children.

UNLABELLED: We retrospectively reviewed the medical records and imaging studies of 15 children with infections of the sacroiliac joint to determine the usefulness of specific examinations and studies to aid in the early diagnosis of this condition. The clinical presentation, physical examination findings, pertinent laboratory data, and imaging studies were reviewed. Thirteen patients (87%) were febrile at the time of presentation. One patient presented in septic shock requiring intubation and critical care management. Tenderness to palpation over the sacroiliac joint was present in all 9 patients who had this examination performed, and the flexion abduction external rotation test was positive in 10 of 12 patients (83%) who had this test done. Laboratory indicators of infection were elevated in most patients, and 6 patients (46%) had positive blood cultures, most commonly growing Staphylococcus aureus. Initial conventional radiographs were negative in all but 1 patient. Radionuclide 99-m-technetium bone scans were positive in 7 of 10 patients (70%), and magnetic resonance imaging studies were ultimately positive in 13 of 14 patients (93%). However, within the first 6 days after the onset of symptoms, only 5 of 8 bone scans (63%) and 5 of 9 magnetic resonance imaging studies (57%) were consistent with infection. We conclude that while diagnostic imaging studies are ultimately helpful in confirming the diagnosis of sacroiliac joint infections in children, studies made within 6 days of the onset of symptoms may not always confirm the diagnosis. The early diagnosis of this condition is best made on the basis of clinical and laboratory findings. LEVEL OF EVIDENCE: Therapeutic Study, level IV (Case series [no, or historical control group]).

Imaging of amyloid arthropathy.

Amyloidosis is a disease complex caused by the extracellular deposition of an insoluble protein called amyloid. Amyloid arthropathy results from localized amyloid deposition in and around the joints. This article discusses the types of amyloidosis associated with amyloid arthropathy and presents their characteristic imaging findings.

Infliximab treatment of Familial Mediterranean fever and its effect on secondary AA amyloidosis.

We describe a patient with a long history of familial Mediterranean fever who developed proteinuria as a result of secondary AA amyloidosis. In this patient, the inflammatory process, including recurrent attacks of arthritis, abdominal pain, nephrotic syndrome secondary to amyloidosis, and high sedimentation rate, was rapidly suppressed by treatment with infliximab and there was remarkable improvement of the proteinuria.Because TNF-alpha is a proinflammatory cytokine that plays a major role in FMF and secondary amyloid, it is an appropriate target for therapy. Our case is the first case of reactive systemic amyloidosis secondary to familial Mediterranean fever, which responded favorably to infliximab.

Inflammatory arthritis secondary to metastatic gastric cancer.

Metastatic spread of malignancy to the joints is rare and only a few cases of solid tumors have been reported. We describe a patient with inflammatory arthritis of the knee and ankle secondary to metastatic gastric adenocarcinoma to the joints and bone diagnosed by synovianalysis. Arthritis secondary to metastatic cancer is a poor prognostic sign. The diagnosis is based on a strong clinical suspicion, magnetic resonance imaging, and joint fluid cytology or synovial biopsy.