CT and MR Imaging of the Postoperative Ankle and Foot.

A variety of surgical procedures exist for repair of both traumatic and degenerative osseous and soft-tissue pathologic conditions involving the foot and ankle. It is necessary for the radiologist to be familiar with these surgical procedures, so as to assess structural integrity, evaluate for complicating features, and avoid diagnostic pitfalls. Adequate interpretation of postoperative changes often requires access to surgical documentation to evaluate not only the surgery itself but the expected timeline for resolution of normal postoperative changes versus progressive disease. Appropriate use of surgical language in radiology reports is another important skill set to hone and is instrumental in providing a high-quality report to the referring surgeons. The pathophysiology of a myriad of surgical complaints, beginning from the Achilles tendon and concluding at the plantar plate, are presented, as are their common appearances at computed tomography and magnetic resonance imaging. Commonly encountered entities include Achilles tendon tear, spastic equinus, nonspastic equinus, talar dome osteochondral defect, tarsal tunnel syndrome, plantar fasciitis, pes planovalgus, pes cavovarus, peroneal tendinosis, lateral ligament complex pathology, Morton neuroma, plantar plate tear, and metatarsophalangeal joint instability. Computer-generated three-dimensional models are included with many of the procedures to provide a more global view of the surgical anatomy. Correlation with intraoperative photographs is made when available. When appropriate, discussion of postoperative complications, including entities such as infection and failure of graft integration, is presented, although a comprehensive review of postoperative complications is beyond the scope of this article. Notably absent from the current review are some common foot and ankle procedures including hallux valgus and hammertoe corrections, as these are more often evaluated radiographically than with cross-sectional imaging. ©RSNA, 2016.

Myositis Ossificans in the Thigh of a Lacrosse Player.

An 18-year-old man presented with mid left thigh pain after sequential lacrosse injuries 1 month and 2 weeks prior. Physical examination was significant for a tender mass in the mid left thigh.

Magnetic Resonance Arthrography of the Wrist and Elbow.

Magnetic resonance (MR) arthrography of the wrist and elbow is useful for detecting a variety of intra-articular pathologies. MR dictations should address whether intrinsic ligament tears of the wrist are partial-thickness or full-thickness, and involve the dorsal, membranous, and/or volar components of the ligaments. With regard to elbow soft tissue pathology, partial-thickness tears of the anterior band of the ulnar collateral ligament in overhead-throwing athletes are well evaluated with MR arthrography. MR arthrography also is helpful in staging osteochondritis dissecans of the capitellum, caused by repetitive valgus impaction injury in adolescent or young adult baseball pitchers.

Osteochondral lesions of the elbow.

Osteochondral lesions of the elbow are injuries that disrupt the cartilage and subjacent bone, and they most commonly involve the capitellum. The staging, prognosis, and treatment of osteochondral lesions in the elbow are based on a combination of radiographic, magnetic resonance imaging, and arthroscopic findings. Radiographic staging includes the radiolucent, separation, and free (advanced) stages. MR imaging features of instability include cysts, osteochondral fracture, T2 hyperintense rim, subchondral plate defects, and fluid-filled osteochondral defects. Finally, arthroscopic grading of osteochondral lesions increases in severity based on findings of softened cartilage, cartilage fissuring, exposed bone, loose but nondisplaced fragments, and eventually displaced fragments resulting in intra-articular bodies. This pictorial review focuses on osteochondral lesions in the capitellum and trochlea including osteochondritis dissecans, Panner disease, and acute trauma.

Imaging of benign soft tissue tumors.

The evaluation of soft tissue tumors should be approached systematically, with careful assessment of the patient's age, clinical presentation, anatomical location of the mass, and MRI characteristics. The imaging evaluation of a suspected soft tissue mass begins with conventional radiography to exclude an underlying osseous lesion and assess for any lesional calcification. MRI is particularly useful in evaluating the signal intensity, enhancement pattern, and extent of soft tissue masses that can expand beyond fascial planes and involve the neurovascular bundle, joint, or bone. Among the common benign soft tissue tumors, a fairly definitive imaging diagnosis can be made in cases of lipoma, elastofibroma dorsi, hemangiomas, myositis ossificans, giant cell tumor of tendon sheath, and peripheral nerve sheath tumors. In the remaining cases, the differential diagnosis can be narrowed by knowing the patient's demographics and any associated syndromes, in conjunction with recognizing specific MRI features. Knowledge of the World Health Organization's tumor designations and the incidence of specific tumors based on patient age and anatomical location are vital tools for the interpreting radiologist.

Magnetic resonance imaging of hip tumors.

After initial evaluation with radiography, magnetic resonance (MR) imaging is the most common modality used to establish the diagnosis and characterize osseous and soft tissue tumors of the hip. Tumors involving the proximal femur are often benign, and MR imaging can be specific in diagnosing solitary bone cyst, osteochondroma, and chondroblastoma. Benign and malignant soft tissue tumors about the hip are often nonspecific in their MR imaging appearances, but knowledge of the patient's age may direct a more limited differential diagnosis. In the setting of malignancy, MR imaging is commonly used to stage tumors and follow patients postoperatively.

Postoperative shoulder magnetic resonance imaging.

Magnetic resonance imaging (MRI) and MR arthrography have proven invaluable for managing the postoperative shoulder, particularly in relation to the rotator cuff and labrum. MRI has proven to be an accurate imaging technique for differentiating expected findings versus complications in the postoperative setting. The transition from metallic hardware to bioabsorbable suture anchors used in orthopedic surgery has rendered less metallic susceptibility artifact over the years, allowing more accurate interpretation of MR images. This article gives a pictorial review of various expected postoperative findings in the shoulder and complications related to repair of the rotator cuff and labrum.

Gender differences in organ density in a rat simulated microgravity model.

Research investigating the physiological effects of microgravity on the human body has demonstrated a shift of body fluids in actual spaceflight and in simulated Earth-based microgravity models in both males and females, possibly causing many deleterious physiological effects. Twenty-five anatomically normal female (NF) and 20 ovariectomized (OE) Fischer 344 rats were randomly selected to be in an experimental (1 h of 45 degrees head-down tilt, 45HDT) or control (1 h of prone position) group. At the end of the hour experimental period, the density of the brain, lungs, heart, liver, and left and right kidneys were measured using spiral computed tomography (SCT) while the rats remained in their experimental positions. A sub-group of OE rats (N=6) was administered estrogen replacement therapy on a daily basis (5 micrograms/kg body weight, s.c.) for 4 days and then underwent 1 h of 45HDT and SCT analysis at one day, 2 days, and 5 days to determine if estrogen replacement therapy would alter organ densities. Our data demonstrate that 1 h of 45HDT produced significant increases (p<0.05) in the organ densities of the brain, liver, left kidney, and lung of the OE female group compared to their prone controls. However, only the brain density was significantly increased in the NF group. Estrogen replacement therapy caused a significant decrease in brain organ density at the 5 day time point compared to the 24 h time point. We conclude that estrogen plays a role in fluid distribution in a rat 45HDT model.

Changes in organ perfusion and weight ratios in post-simulated microgravity recovery.

Head-down tilt models have been used as ground-based simulations of microgravity. Our previous animal research has demonstrated that there are significant changes in fluid distribution within 2 h after placement in a 45 degrees head-down tilt (45HDT) position and these changes in fluid distribution were still present after 14 days of 45HDT. Consequently, we investigated changes in fluid distribution during recovery from 16 days of 45HDT. Changes in radioactive tracer distribution and organ/body weight ratio were examined in rats randomly assigned to a 45HDT or prone control group. The 45HDT rats were suspended for 16 days and then allowed to recover at the prone position 0, 77, 101, or 125 h post-suspension. Animals were injected with technetium-labeled diethylenetriamine pentaacetate (99mTcDTPA, MW=492 amu, physical half-life of 6.02 h) and then killed 30 min post-injection. Lungs, heart, liver, spleen, kidneys, and brain were harvested, weighed, and measured for radioactive counts. Statistical analyses included two-way analysis of variance (ANOVA) that compared 45HDT versus controls at the four experimental time points. The organ weight divided by the body weight ratio for the brain, heart, kidneys and liver in the 45HDT rats was significantly different than the control rats, regardless of time (treatment). There was no difference between the different time points (time). The average 99mTcDTPA count divided by the organ weight ratio values for the heart, liver, and spleen were significantly higher in the 45HDT group than the control group. The average counts for the heart and spleen were significantly higher at 77, 101, and 125 h than at time zero. We conclude that the major organs have different recovery patterns after 45HDT for 16 days in the rat.