Intraosseous lipomas originating from simple bone cysts.

PURPOSE: Fatty or part-fatty intraosseous lesions are occasionally encountered while imaging the skeletal system. A number of case reports have proposed involution of calcaneal bone cysts to intraosseous lipomas, but this has never been proven. This paper sets out to prove that simple bone cysts (SBCs) can involute to fatty lesions indistinguishable from intraosseous lipomas. MATERIALS AND METHODS: The pathology and PACS databases at 2 specialist orthopedic hospitals were retrospectively interrogated for all cases of intraosseous lipomas or SBCs with cross-sectional imaging follow-up for SBCs and precursor or follow-up imaging for intraosseous lipomas, in the time period from August 2007 to December 2016. For intraosseous lipoma cases, these were only included if change in imaging appearances was observed. RESULTS: There was no case of change in the appearance in intraosseous lipomas. Six cases of SBC with cross-sectional imaging follow-up were identified in one participating hospital and none in the other. The 6 cases were comprised of 4 male and 2 female patients. Two were located in the proximal humerus, one in the proximal tibia, and 3 in the os calcis. All cases demonstrated filling in of the cystic lesion with fat from the periphery, in 2 cases complete filling in, and in 4 cases partial fatty conversion. CONCLUSION: SBCs can heal with fatty conversion of the cystic cavity, with partly cystic remnants. It is proposed that at least part of the so-called intraosseous lipomas are healed simple bone cysts.

Radiofrequency thermo-ablation of PVNS in the knee: initial results.

INTRODUCTION: Pigmented villonodular synovitis (PVNS) is normally treated by arthroscopic or open surgical excision. We present our initial experience with radiofrequency thermo-ablation (RF ablation) of PVNS located in an inaccessible location in the knee. MATERIALS: Review of all patients with histologically proven PVNS treated with RF ablation and with at least 2-year follow-up. RESULTS: Three patients met inclusion criteria and were treated with RF ablation. Two of the patients were treated successfully by one ablation procedure. One of the three patients had a recurrence which was also treated successfully by repeat RF ablation. There were no complications and all patients returned to their previous occupations following RF ablation. CONCLUSION: In this study we demonstrated the feasibility of performing RF ablation to treat PVNS in relatively inaccessible locations with curative intent. We have also discussed various post-ablation imaging appearances which can confound the assessment for residual/recurrent disease.

Prevalence of extraforaminal nerve root compression below lumbosacral transitional vertebrae.

OBJECTIVE: Although pathology at the first mobile segment above a lumbosacral transitional vertebra (LSTV) is a known source of spinal symptoms, nerve root compression below an LSTV, has only sporadically been reported. Our objective was to assess the prevalence of nerve root entrapment below an LSTV, review the causes of entrapment, and correlate with presenting symptoms. MATERIALS AND METHODS: A retrospective review of MR and CT examinations of the lumbar spine was performed over a 5.5-year period in which the words "transitional vertebra" were mentioned in the report. Nerve root compression below an LSTV was assessed as well as the subtype of transitional vertebra. Correlation with clinical symptoms at referral was made. MR and CT examinations were also reviewed to exclude any other cause of symptoms above the LSTV. RESULTS: One hundred seventy-four patients were included in the study. Neural compression by new bone formation below an LSTV was demonstrated in 23 patients (13%). In all of these patients, there was a pseudarthrosis present on the side of compression due to partial sacralization with incomplete fusion. In three of these patients (13%), there was symptomatic correlation with no other cause of radiculopathy demonstrated. A further 13 patients (57%) had correlating symptoms that may in part be attributable to compression below an LSTV. CONCLUSIONS: Nerve root compression below an LSTV occurs with a prevalence of 13% and can be symptomatic in up to 70% of these patients. This region should therefore be carefully assessed in all symptomatic patients with an LSTV.

Venous air embolism in consecutive balloon kyphoplasties visualised on CT imaging.

OBJECTIVE: We noted a large amount of intravenous gas during balloon kyphoplasty on CT imaging. Formal assessment to understand the extent, possible causes and implications was undertaken. MATERIALS AND METHODS: Ten consecutive cases of balloon kyphoplasty were performed under general anaesthesia in the prone position, on a single vertebral level using a two-step technique under combined fluoroscopic and CT guidance. CT of the affected vertebra was performed before, after, and intermittently during the procedure. In 2 cases delayed CT was carried out in the supine position. RESULTS: Gas was seen on CT imaging, but not on conventional fluoroscopy. The gas is most likely to be air introduced during the procedure and was seen in the epidural and paravertebral venous plexus, posterior intercostal veins, renal veins, IVC and azygos vein. The average measured volume of gas seen on the post-procedure CT imaging was 1.07 mL, range 0.16-3.97 mL. There was no correlation of the measured amount of gas to the procedure duration or location, the use of a curette or the injected cement volume. Delayed CT in the supine position no longer showed air in the local venous system. CONCLUSIONS: Balloon kyphoplasty is associated with the fluoroscopically invisible introduction of air into the vertebral and paravertebral veins and deep systemic veins and is likely to be much more extensive than identified on CT imaging. There is potential for serious air embolism in kyphoplasty and if there is a sudden deterioration in patient condition during the procedure the possibility of this complication needs to be considered.

Magnetic resonance imaging of appendicular musculoskeletal infection.

Appendicular skeletal infection includes osseous and extraosseous infections. Skeletal infection needs early diagnosis and appropriate management to prevent long-term morbidity. Magnetic resonance imaging is the best imaging modality to diagnose skeletal infection early in most circumstances. This article describes the role of magnetic resonance imaging in relation to the other available imaging modalities in the diagnosis of skeletal infection. Special circumstances such as diabetic foot, postoperative infection, and chronic recurrent multifocal osteomyelitis are discussed separately.

Magnetic resonance imaging of spinal infection.

This article reviews the pathophysiology of spinal infection and its relevance for imaging. Magnetic resonance imaging (MRI) is the modality with by far the best sensitivity and specificity for spinal infection. The imaging appearances of spinal infection in MRI are outlined, and imaging techniques are discussed. The problems of clinical diagnosis are outlined. There is some emphasis on the MRI differentiation of pyogenic and nonpyogenic infection and on the differential diagnosis of spinal infection centered on the imaging presentation.

Imaging investigations in Spine Trauma: The value of commonly used imaging modalities and emerging imaging modalities.

Traumatic spine injuries can be devastating for patients affected and for health care professionals if preventable neurological deterioration occurs. This review discusses the imaging options for the diagnosis of spinal trauma. It lays out when imaging is appropriate and when it is not. It discusses strength and weakness of available imaging modalities. Advanced techniques for spinal injury imaging will be explored. The review concludes with a review of imaging protocols adjusted to clinical circumstances.

Incidence of numerical variants and transitional lumbosacral vertebrae on whole-spine MRI.

OBJECTIVES: This study sets out to prospectively investigate the incidence of transitional vertebrae and numerical variants of the spine. MATERIALS AND METHODS: Over a period of 28 months, MRIs of the whole spine were prospectively evaluated for the presence of transitional lumbosacral vertebrae and numerical variants of the spine. RESULTS: MRI of the whole spine was evaluated in 420 patients, comprising 211 female and 209 male subjects. Two patients had more complex anomalies. Lumbosacral transitional vertebrae were seen in 12 patients: eight sacralised L5 (3 male, 5 female) and four lumbarised S1 (3 male, 1 female). The incidence of transitional vertebrae was approximately 3.3. % (14/418). Thirty-two (7.7 %) of 418 patients had numerical variants of mobile vertebrae of the spine without transitional vertebrae. The number of mobile vertebrae was increased by one in 18 patients (12 male, 6 female), and the number was decreased by one in 14 patients (4 male, 10 female). CONCLUSIONS: Numerical variants of the spine are common, and were found to be almost 2.5 times as frequent as transitional lumbosacral vertebrae in the study population. Only whole-spine imaging can identify numerical variants and the anatomical nature of transitional vertebrae. The tendency is toward an increased number of mobile vertebrae in men and a decreased number in women. Main messages • Numerical variants of the spine are more common than transitional vertebrae. • Spinal numerical variants can be reliably identified only with whole-spine imaging. • Increased numbers of vertebrae are more common in men than women. • Transitional lumbosacral vertebrae occurred in about 3.3 % of the study population. • The incidence of numerical variants of the spine was about 7.7 %.

Stress fracture of the pelvis and lower limbs including atypical femoral fractures-a review.

Stress fractures, that is fatigue and insufficiency fractures, of the pelvis and lower limb come in many guises. Most doctors are familiar with typical sacral, tibial or metatarsal stress fractures. However, even common and typical presentations can pose diagnostic difficulties especially early after the onset of clinical symptoms. This article reviews the aetiology and pathophysiology of stress fractures and their reflection in the imaging appearances. The role of varying imaging modalities is laid out and typical findings are demonstrated. Emphasis is given to sometimes less well-appreciated fractures, which might be missed and can have devastating consequences for longer term patient outcomes. In particular, atypical femoral shaft fractures and their relationship to bisphosphonates are discussed. Migrating bone marrow oedema syndrome, transient osteoporosis and spontaneous osteonecrosis are reviewed as manifestations of stress fractures. Radiotherapy-related stress fractures are examined in more detail. An overview of typical sites of stress fractures in the pelvis and lower limbs and their particular clinical relevance concludes this review. Teaching Points • Stress fractures indicate bone fatigue or insufficiency or a combination of these. • Radiographic visibility of stress fractures is delayed by 2 to 3 weeks. • MRI is the most sensitive and specific modality for stress fractures. • Stress fractures are often multiple; the underlying cause should be evaluated. • Infratrochanteric lateral femoral fractures suggest an atypical femoral fracture (AFF); endocrinologist referral is advisable.

Imaging in rheumatology: reconciling radiology and rheumatology.

Imaging in rheumatology was in the past largely confined to radiographs of the hands and sacroiliac joints (SIJs) helping to establish the diagnosis and then monitoring disease progression. Radiographs are not very sensitive for early inflammation in inflammatory rheumatic disorders and the demand on imaging services was therefore limited. However, over the last 10-15 years new drugs and new technologies have brought new challenges and opportunities to rheumatology and radiology as specialties. New drug treatments allow more effective treatment, preventing many complications. Early diagnosis and disease monitoring has become the challenge for the rheumatologist and radiologist alike. The best possible patient outcome is only achieved if the two specialties understand each other's viewpoint. This article reviews the role of imaging-in particular radiography, magnet resonance imaging, computer tomography, ultrasound and nuclear medicine-for the diagnosis and monitoring of rheumatological disorders, concentrating on rheumatoid arthritis, inflammatory spondylarthropathies and gout. Teaching Points • New drugs for the treatment of inflammatory disorders has led to greatly improved outcomes. • Imaging often allows for earlier diagnosis of inflammatory disorders. • Early diagnosis and treatment can often prevent the development of crippling disease manifestations. • Tailored imaging examinations are best achieved by consultation of rheumatologist and radiologist.

Migrating lumbar facet joint cysts.

OBJECTIVE: The majority of lumbar facet joint cysts (LFJCs) are located in the spinal canal, on the medial aspect of the facet joint with characteristic diagnostic features. When they migrate away from the joint of origin, they cause diagnostic problems. MATERIALS AND METHODS: In a 7-year period we examined by computed tomography (CT) and magnetic resonance (MR) imaging five unusual cases of facet joint cysts which migrated from the facet joint of origin. RESULTS: Three LFJCs were identified in the right S1 foramen, one in the right L5-S1 neural foramen and one in the left erector spinae and multifidus muscles between the levels of L2-L4 spinous process. CONCLUSIONS: Awareness that spinal lesions identified at MRI and CT could be due to migrating facet joint cyst requires a high level of suspicion. The identification of the appositional contact of the cyst and the facet joint needs to be actively sought in the presence of degenerative facet joints.

Uncovertebral joint injury in cervical facet dislocation: the headphones sign.

The purpose of our study is to demonstrate the uncovertebral mal-alignment as a reliable indirect sign of cervical facet joint dislocation. We examined the uncovertebral axial plane alignment of 12 patients with unilateral and bilateral cervical facet joint dislocation (UCFJD and BCFJD, respectively), comparing its frequency to the reverse hamburger bun sign on CT and MR axial images. Of the seven cases with BCFJD, five clearly demonstrated the diagnostic reverse facet joint hamburger bun sign on CT and MR images, but in two cases this sign was not detectable. In the five cases with UCFJD, four demonstrated the reverse hamburger bun sign on both CT and MRI. In one case the reverse hamburger bun sign was not seen adequately with either image modality, but the facet dislocation was identified on sagittal imaging. The uncovertebral mal-alignment was detected in all 12 cases. Normally, the two components of the uncovertebral joint enjoy a concentric relationship that in the axial plane is reminiscent of the relationship of headphones with the wearer's head. We name this appearance the 'headphones' sign. Radiologists should be aware of the headphones sign as a reliable indicator of facet joint dislocation on axial imaging used in the assessment of cervical spine injuries.

Chance-type flexion-distraction injuries in the thoracolumbar spine: MR imaging characteristics.

PURPOSE: To evaluate retrospectively the magnetic resonance (MR) imaging features of Chance-type flexion-distraction injuries. MATERIALS AND METHODS: The authors' institutional review board does not require its approval or patient informed consent for retrospective studies. Imaging data were reviewed retrospectively for 24 patients (15 male, nine female; mean age, 28 years; range, 9-71 years) who had sustained radiographically typical Chance-type flexion-distraction injuries. The posterior vertebral body height remained unchanged or was increased in these patients. Two radiologists recorded a variety of bone and soft-tissue abnormalities seen with MR imaging. Based on consensus, the documented findings were sequentially analyzed to determine their frequencies. RESULTS: Combined bone and soft-tissue injuries occurred in 23 (96%) of 24 patients, were more common than soft-tissue damage alone (one [4%] of 24 patients), and occurred primarily at the thoracolumbar junction. Contiguous vertebral injury was seen in 20 (83%) of 24 patients, usually in the form of anterosuperior vertebral endplate edema, while noncontiguous injury occurred in eight (33%) of 24 patients. Extensive subcutaneous and paraspinal muscle edema was seen in all patients and extended over several segments. Posterior osteoligamentous complex disruption also occurred in all patients. Horizontally oriented fractures of the posterior neural arches produced an MR imaging pattern that the authors call the sandwich sign, which consists of linear hemorrhage framed by marrow edema. This sign was seen in 12 (50%) of 24 patients. In seven (29%) of 24 patients, a fracture line extending from a damaged pedicle was seen to exit through the contralateral posterosuperior aspect of the vertebral body, with extension of the fracture fragments into the spinal canal. CONCLUSION: A spectrum of features is discernible with MR imaging in Chance-type injuries.

Autologous chondrocyte implantation in knee joint: MR imaging and histologic features at 1-year follow-up.

PURPOSE: To evaluate magnetic resonance (MR) imaging features of autologous chondrocyte implantation (ACI) grafts and compare these with graft histologic features 1 year after ACI for treatment of femoral condylar defects. MATERIALS AND METHODS: This study was approved by the regional ethics committee, and all patients gave informed consent. Forty-one patients (mean age, 35 years; 30 men, 11 women) underwent ACI for treatment of femoral condylar defects. One year later, knee joint MR imaging and graft biopsy were performed. Graft biopsy results were categorized into those showing hyaline, mixed fibrohyaline cartilage, fibrocartilage, and fibrous tissue. Standard T1-, T2-, T2*-, and intermediate-weighted sequences were performed, as well as three-dimensional (3D) fast low-angle shot (FLASH) and double-echo steady-state sequences for cartilage assessment. ACI grafts were assessed for signal intensity (with FLASH sequence), thickness, overgrowth, surface smoothness, integration to adjacent cartilage and underlying bone, bone marrow edema underneath graft, and contour of bone underneath graft. MR images were assessed by two observers, first independently and then in consensus. MR imaging findings were correlated with histologic findings. RESULTS: All 41 grafts were present at 1-year follow-up. The graft consisted of hyaline cartilage in four, mixed fibrohyaline cartilage in 10, fibrocartilage in 25, and fibrous tissue in two cases. Graft signal intensity was virtually always lower than adjacent normal cartilage signal intensity, and there was no relationship between graft signal intensity and histologic appearance (P = .34). Graft thickness (P = .83), overgrowth (P = .69), surface smoothness (P = .28), and integration with adjacent cartilage and underlying bone (P = .90); edema in bone marrow underneath graft (P = .63); and bone contour underneath graft (P = .94) at MR imaging had no correlation with graft histologic appearance. Graft overgrowth (n = 16; 39%) and edema-like signal in bone marrow underneath graft (n = 23; 56%) were common. The origin of graft overgrowth remains unclear. CONCLUSION: With the methods presented here, MR imaging findings cannot predict ACI graft histologic features, and graft histologic appearance determined at biopsy was not related to graft signal intensity, graft thickness, overgrowth, surface smoothness, integration with adjacent cartilage or underlying bone, signal intensity change in underlying bone marrow, or underlying bone contour. Overgrowth and bone marrow changes underneath the graft were common.

MR imaging of spinal infection.

Magnetic resonance (MR) imaging plays a pivotal role in the diagnosis and management of spinal infection, enjoying a high sensitivity and specificity. A thorough understanding of spinal anatomy and the physicochemical pathological processes associated with infection is a desirable prerequisite allowing accurate interpretation of the disease process. Apart from confirmation of the disease, MR imaging is also best suited to excluding multifocal spinal involvement and the detection/exclusion of complications. It plays an essential role in the decision-making process concerning conservative versus surgical treatment and is also the best imaging method to monitor the effect of treatment. The MR features of infection confidently exclude tumor, degeneration, and so forth as the underlying process; differentiate pyogenic from granulomatous infections in most cases; and can suggest the rarer specific infective organisms.