A. M. Davies

The effect of X-rays on bone: a pictorial review

Abstract The deleterious effects of X-rays on bone have been recognised for almost a century and continue to be seen today because of improved survival in patients treated for malignancy with radiotherapy with or without other treatments. In this pictorial review we present the imaging features of radiation damage to bone highlighting the differences seen in the immature skeleton and post-skeletal fusion. In the former, damage is greatest to the physis resulting in growth disturbances. In the mature skeleton there is a spectrum of changes from mild osteopenia, through disordered attempts at healing with varying degrees of sclerosis, radionecrosis which may lead to acute fractures following minimal trauma and insufficiency fractures both with refractory healing to the dreaded complication of sarcomatous transformation. The imaging appearances are illustrated and the features that help distinguish malignant change from other complications stressed.

Primary synovial chondromatosis and synovial chondrosarcoma: a pictorial review

Abstract. This article illustrates the imaging characteristics of primary synovial chondromatosis (PSC) using 20 cases referred to a tertiary orthopaedic oncology centre. Three quarters of patients presented with a large intra-articular soft tissue mass and a suspected clinical and radiological diagnosis of malignancy made in the referring centres. Radiographs demonstrated fine cartilaginous mineralisation in the soft tissue masses in 85% cases and bone erosions were shown on MR imaging in 80%. Malignant transformation to chondrosarcoma was proven in 2 cases with longstanding disease. There were no specific MR features to distinguish these cases with malignant change from PSC alone. Primary synovial chondromatosis should be considered in the diagnosis of the monarticular presentation of an intra-articular soft tissue mass, particularly in the presence of superficial bone erosions and signal voids due to the mineralisation.

Imaging features of intraosseous ganglia: a report of 45 cases.

The aim of this study is to report the spectrum of imaging findings of intraosseous ganglia (IG) with particular emphasis on the radiographic and magnetic resonance (MR) features. Forty-five patients with a final diagnosis of IG were referred to a specialist orthopaedic oncology service with the presumptive diagnosis of either a primary or secondary bone tumour. The diagnosis was established by histology in 25 cases. In the remainder, the imaging features were considered characteristic and the lesion was stable on follow-up radiographic examination. Radiographs were available for retrospective review in all cases and MR imaging in 29. There was a minor male preponderance with a wide adult age range. Three quarters were found in relation to the weight-bearing long bones of the lower limb, particularly round the knee. On radiographs all were juxta-articular and osteolytic; 74% were eccentric in location, 80% had a sclerotic endosteal margin and 60% of cases showed a degree of trabeculation. Periosteal new bone formation and matrix mineralization were not present. Of the 29 cases that underwent MR imaging, 66% were multiloculated. On T1-weighted images the IG contents were isointense or mildly hypointense in 90% cases. Forty-one per cent of the cases showed a slightly hyperintense rim lining that enhanced with a gadolinium chelate. Thirty-eight per cent were associated with soft tissue extension and 17% with a defect of the adjacent articular cortex. Fifty-five per cent showed surrounding marrow oedema on T2-weighted or STIR images and two cases (7%) a fluid-fluid level prior to any surgical intervention. The authors contend that it is semantics to differentiate between an IG and a degenerate subchondral cyst as, while the initial pathogenesis may vary, the histological endpoint is identical, as are the imaging features apart from the degree of associated degenerative joint disease. IGs, particularly when large, may be mistaken for a bone tumour. Correlation of the typical radiographic and MR imaging features will indicate the correct diagnosis and obviate the need for biopsy.

Differential diagnosis of tumours and tumour-like lesions of the infrapatellar (Hoffa’s) fat pad: pictorial review with an emphasis on MR imaging

A variety of intrinsic and extrinsic tumours and tumour-like conditions may affect the infrapatellar (Hoffa’s) fat pad (IFP). MR imaging is the technique of choice in evaluating these conditions, but correlation with radiographs is important to identify those lesions producing mineralization. This pictorial review illustrates the spectrum of mass-like lesions that can affect the IFP, emphasizing the radiographic and MR findings that suggest a specific diagnosis.

The penumbra sign in subacute osteomyelitis

The penumbra sign is a characteristic magnetic resonance (MR) feature of subacute osteomyelitis. It can be identified on unenhanced T1-weighted spin echo images as a discrete peripheral zone of marginally higher signal intensity than the central bony abscess cavity and the surrounding lower signal intensity of the reactive new bone and oedema.

Imaging strategy for detecting lung metastases at presentation in patients with soft tissue sarcomas

PURPOSE To identify the risk of lung metastases at the time of diagnosis in patients with soft tissue sarcomas (STS) and to establish the optimum imaging strategy for the diagnosis of these metastases and whether this affects outcome. MATERIALS AND METHODS A retrospective review of an orthopaedic oncology database identified 1170 patients with newly diagnosed STS during a 7.5-year period (1996-2004). The patient demographics, tumour type, size, depth, histology grade and presence of metastatic disease at presentation were studied. The chest radiograph (CXR)/computed tomography of the chest (CT chest) findings, performed as part of the initial staging study, were available in all patients. We estimated the efficacy of CXR in identifying pulmonary metastatic disease compared with CT chest and whether this affected patient survival. RESULTS The incidence of metastases at diagnosis was 10% (116 patients), 8.3% (96 patients) had lung metastases on chest CT and 1.7% (20 patients) had metastases elsewhere. The risk of having lung metastases at diagnosis was 11.8% in high grade tumours, 7% in intermediate grade and 1.2% in low grade tumours. CXR alone detected 2/3 of all lung metastases. The positive predictive value of the CXR was 93.3%, the negative predictive value 96.7%, the sensitivity 60.8% and the specificity 99.6%. The accuracy was 96.9%. CT overestimated metastases in 4% with a sensitivity of 100%, specificity of 99.6% and accuracy of 99.6%. Median survival of patients with lung metastases at diagnosis was 11 months and there was no significant difference in survival between those who had metastases detected on CXR or purely on CT. DISCUSSION We recommend that all patients with a suspected STS should have a CXR at presentation, prior to histological diagnosis. CT of the chest should then be performed in those patients with an abnormality on the presentation CXR and routinely in those patients who have large, deep seated or high/intermediate grade tumours and in certain histological subtypes where the incidence of lung metastases at diagnosis is known to be high. In our experience, this strategy will detect 93% of all chest metastases. With current treatment strategies for metastases, outcome is not likely to be affected by any delay in diagnosis.

The role of MR imaging in the diagnostic characterisation of appendicular bone tumours and tumour-like conditions

MRI has an established role in the local staging of primary bone tumours. However, as the majority of tumours have non-specific appearances on MRI, the diagnosis is usually established on the basis of clinical history, plain film findings and biopsy. This article reviews the value of MRI in the further characterisation of appendicular bone tumours and tumour-like lesions, with particular reference to peri-lesional oedema, fluid-fluid levels, flow voids, fat signal, cartilage signal and dedifferentiation. These features are a useful adjunct for distinguishing between benign and malignant disease, pointing towards a more specific diagnosis, and guiding biopsy.

Atraumatic avulsion of the lesser trochanter as an indicator of tumour infiltration

Avulsion of the lesser trochanter can be identified on radiographs when a variable-sized fragment of bone is pulled off and displaced from the surface of the trochanter. It is due to an avulsion by the iliopsoas tendon and is well recognised following acute trauma, typically in children and adolescents [1–3]. Atraumatic avulsions are much less common and it has been suggested that they should be considered as pathognomonic of underlying metastatic disease (Fig. 1) [4, 5].

MR imaging of pseudosarcoma in Paget’s disease of bone: a report of two cases

Abstract Pseudosarcoma is a rare manifestation of Paget’s disease of bone. We report the MR imaging of two cases highlighting the difficulties in diagnosis. One of the cases is the first time this condition has been described outside the long bones of the lower limb.

MR imaging features of giant pre-sacral schwannomas: a report of four cases

Abstract. Benign giant sacral schwannoma is an uncommon cause of destruction of the sacrum. This report details four cases of a variant of this condition called giant presacral schwannoma (GPSS). On MR imaging the features are of a large, well-defined presacral soft tissue mass, arising just to one side of the midline with minor involvement of the bone. The typical MR features of a benign peripheral nerve sheath tumour are not seen. The tumours appear heterogeneous due to long-standing degeneration. Biopsy is advocated as the appearances of GPSS can be similar to a malignant peripheral nerve sheath tumour (malignant schwannoma).