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The association between congenital pseudoarthrosis and osteofibrous dysplasia of the tibia and fibula is a rare entity that has been recently recognized. We report a male newborn who was found to have swelling and deformity of the left lower leg. Radiographs and magnetic resonance imaging showed an extensive destructive lesion of the tibial shaft, with dysplastic congenital pseudoarthrosis of the lower fibula. Histopathological examination confirmed the diagnosis of congenital pseudoarthrosis of the tibia and fibula with underlying osteofibrous dysplasia involving both bones. Immunohistochemical stains showed cytokeratin positivity.

The imaging features of extensive lipofibromatosis presenting in a 1-day-old female infant are reported. This lesion involved her entire right upper limb, extending from the axilla to the palm of the hand. Radiographs showed marked deformity and thinning of all the right upper-limb bones due to pressure effect of soft-tissue enlargement, especially affecting the distal humerus and proximal forearm bones. Magnetic resonance imaging showed a huge soft-tissue mass infiltrating most of the muscles of the entire upper limb, with bony erosion. The mass was largely T1-isointense, moderately T2-hyperintense and showed marked enhancement. There were intra-lesional signal changes consistent with fatty elements. A lesion debulking procedure was performed and the histology was that of lipofibromatosis. The limb was found to be non-viable after the procedure and a subsequent above-elbow amputation was performed. Although the resection margins were not clear, she had no further recurrence over a subsequent 3-year follow-up period.

The classification of certain vascular bone tumors that show an epithelioid cytologic appearance remains confusing, with overlap in features of epithelioid hemangioma, hemangioendothelioma and epithelioid hemangioendothelioma. Radiographs of a 27-year-old woman who presented with ankle pain showed an expanded lytic-sclerotic lesion in the distal left fibula. Magnetic resonance imaging showed an intramedullary lesion with a small lateral intracortical component. The lesion was hypo- to isointense to muscle on T1-weighted images and heterogeneously hyperintense on T2-weighted images. Initial incisional biopsy was inconclusive. Open biopsy showed hemangioendothelioma with epithelioid morphology, and the lesion was completely resected with reconstruction using a peroneal fibular rotation graft. Examination of the resected specimen showed focal hemangioendothelioma with an epithelioid phenotype arising in a hemangioma. This case illustrates the difficulty and pitfalls of making the correct diagnosis on the basis of a small biopsy specimen.

A 78-year-old man developed a large subdural hematoma extending from T12 to L3 levels following L3 laminectomy and L3-5 posterior spinal fusion. He had associated neurological signs and symptoms. MR imaging showed typical signal characteristics of a subacute intraspinal subdural hematoma. Percutaneous drainage was successfully performed under CT guidance by inserting a Tuohy needle through the L3 laminectomy defect. The catheter packaged with the Tuohy needle was inserted cranially into the hematoma and 30 ml of blood was aspirated. Follow-up MR imaging confirmed resolution of the hematoma and the patient made a rapid recovery.

A large number of artifacts occur in magnetic resonance (MR) imaging of the musculoskeletal system. These artifacts may potentially affect the quality of MR images, and may also simulate pathologic conditions and produce pitfalls in interpretation. Motion artifacts may be periodic or random. Protocol-error artifacts include saturation, wraparound, radiofrequency (RF) interference, shading, and partial volume averaging artifacts. Truncation artifacts occur when the number of phase-encoding steps of high spatial frequencies is insufficient (or under-sampled) for faithful reproduction of the true anatomic detail of the original image. Chemical shift artifacts are due to the protons in fat being mismapped relative to water protons. Susceptibility artifacts occur at the interfaces of structures with different magnetic susceptibilities. Artifacts special to the musculoskeletal system include the magnic angle phenomenon and spurious signal induced at very short echo times, both of which affect anisotropic structures such as tendon, ligament, and cartilage. Recognition and, if possible, correction of these artifacts are an important aspect of practical musculoskeletal MR imaging.

Objective: In magnetic resonance (MR) imaging of the shoulder, oblique coronal images are used for evaluating the supraspinatus tendon (SST) of patients with suspected rotator cuff tear or impingement. This study aimed to compare orientation of the SST long axis with planes perpendicular to the glenohumeral joint (GHJ)., Design and Patients: The axial scans of 100 consecutive patients referred for MR imaging or MR arthrography of the shoulder were reviewed. Using the electronic cursors of a computer workstation, the angle of the SST long axis was measured and compared with the angle obtained through the GHJ utilizing three different landmarks: perpendicular to the joint (GHJ-90), joint-humeral head center axis (GHJ-H) and joint-scapular body axis (GHJ-S)., Results: Differences in angulation between axes of the SST and the three GHJ axes averaged only about 5 degree [range of means 4.5-5.3 degrees, range of standard deviation (SD) 3.8-4.6 degrees]. In the majority of shoulders, angular differences measured 4 or less for all SST/GHJ comparisons. Similarly, small angular differences in the three GHJ axes were found: 4.5 degrees (SD 3.3 degrees) for GHJ-90/GHJ-S, 5.0 degree (SD 4.0 degrees) for GHJ-S/GHJ-H and 2.9 degrees (SD 3.0 degrees) for GHJ-90/GHJ-H. Correlation between the GHJ-90 and GHJ-H axes was particularly good, with differences of 4 degree or less in 84% of shoulders. The orientations of the GHJ axes and that of the SST long axis are comparable., Conclusion: The GHJ may potentially be used as a landmark for obtaining oblique coronal images of the SST.

Chondroblastoma is typically located in the epiphysis. Predominant metadiaphyseal location is very rare, as is involvement of the digits. We describe a case of chondroblastoma involving the metadiaphysis of the thumb. The patient was a 13-year-old boy who presented with pain and swelling of his left thumb. Radiographs showed an expanded lytic lesion involving the whole metaphysis and diaphysis of the proximal phalanx, which subsequently progressed to involve the epiphysis. Curettage and bone grafting were done.

Two cases of osteogenic sarcoma with skeletal muscle metastases are described. A 40-year-old woman presented with progressive swelling of both calves and a soft tissue back lump. She had been diagnosed with mandibular chondroblastic osteogenic sarcoma 6 years earlier. Radiographs showed calcified masses. MRI scans and bone scintigraphy revealed multiple soft tissue masses in both calves. Bone scintigraphy also showed uptake in the back lump, right thigh and left lung base. Biopsy confirmed metastatic chondroblastic osteogenic sarcoma, which initially responded well to chemotherapy. However, the metastatic disease subsequently progressed rapidly and she died 21 months after presentation. The second case concerns a 20-year-old man who presented with a pathologic fracture of the humerus, which was found to be due to osteoblastic osteogenic sarcoma. He developed cerebral metastases 17 months later, followed by metastases at other sites. Calcified masses were subsequently seen on radiographs of the abdomen and chest. CT scans confirmed the presence of densely calcified muscle metastases in the abdominal wall, erector spinae and gluteal muscles. The patient's disease progressed rapidly and he died 30 months after presentation.

Secondary synovial osteochondromatosis (SOC) is a rare disorder caused by a variety of joint disorders. Two unusual cases of secondary SOC are presented. The first patient is a 43-year-old man with extensive SOC developing within a bursa surrounding an osteochondroma of the pubic bone. The second patient is a 23-year-old man who developed florid and progressive SOC of his hip joint following excision of a femoral neck osteochondroma. SOC recurred despite three excisions over a 15-month period. Imaging was useful in pre-operative diagnosis of bursal SOC in the first patient and in detecting multiple recurrences in the second patient. Both cases illustrate prominent SOC developing secondary to osteochondroma. The different hypotheses regarding bursal and secondary SOC are reviewed.

Patients who suffer gun shot wounds often have retained bullet fragments within their bodies. These are usually of no clinical consequence. We describe three patients with retained bullets within their hip joints. One of these patients, who had extensive ground intra-articular bullet fragments and secondary osteoarthritis of the hip, presented with signs, symptoms, and laboratory data consistent with lead intoxication. The bullet and metallic fragments were removed surgically with good clinical response. Two patients whose bullets were implanted entirely within the femoral head and whose joints showed smaller degrees of lead fragmentation had no symptoms of lead intoxication. The degree of intra-articular fragmentation of the bullet and the surface area of lead exposed to synovial fluid are emphasized as decisive factors with respect to appropriate therapy.