Isolated lesions of the pubis.

The osseous pelvis is a well-known area of various primary and secondary bone tumours, tumour mimics, and infections. Isolated lesions of the pubis (ILP) are rare, with few case reports in the literature. Given their sparsity, such lesions may pose a great diagnostic challenge due to varied clinical presentations and imaging features. In this study, we report the largest case series of ILP. We discuss the patient demographics, differentials, surgical approaches, and management.

"Do-not-touch" lesions of bone revisited.

Incidental bone lesions are encountered frequently in day-to-day practice. Many of these lesions are indeterminate requiring referral to specialist centres for further characterisation with or without biopsy; however, as biopsy has its own drawbacks, not all lesions can be subjected to biopsy. The primary role of a radiologist in these situations is to characterise these lesions based on their imaging appearances into aggressive lesions requiring biopsy and non-aggressive lesions that do not require a biopsy. The term "do-not-touch lesion" is used to describe a lesion with typical radiographic appearances that can be characterised based on radiographic appearances alone without needing a biopsy. With recent advances in imaging, many incidental lesions can be characterised into do-not-touch lesions based on their imaging appearances alone using a single imaging technique or using a combination of imaging techniques and, less frequently, with the additional help of serological investigations, without the need for biopsy. Hence, the definition of do-not-touch lesions of bone needs a revisit. In this article, we attempt to redefine do-not-touch lesions of bone and propose an imaging-based classification for characterisation of these lesions.

Tibial tuberosity lesions.

Lesions of the tibial tuberosity are very rare but often present a diagnostic dilemma due to their unusual location and appearances. Although some pathologies affecting this region are commonly seen elsewhere in the skeleton, they may have atypical imaging appearances and morphological characteristics when present at the tibial tuberosity. The present review describes the developmental stages of the tibial tuberosity, explaining why this area is prone to degenerative tractional changes and injury, and also highlights various pathologies including benign and malignant osseous lesions and trauma/degenerative related abnormalities.

MRI assessment of anatomy and pathology of the iliofemoral ligament.

The iliofemoral ligament is strongest ligament of the body. We review the magnetic resonance imaging (MRI) appearances of the iliofemoral ligament, and discuss the disease entities that may affect this region.

An imaging protocol for the management of central cartilage tumours of the proximal fibula.

AIM: To retrospectively review a series of solitary central cartilage tumours (CCTs) of the proximal fibula and propose an imaging protocol for their management. MATERIALS AND METHODS: Over 11 years, 48 patients were identified with a CCT of the proximal fibula. The initial magnetic resonance imaging (MRI) and follow-up imaging were assessed for tumour length, endosteal scalloping, or aggressive/malignant features. Each case was categorised according to the Birmingham Atypical Cartilage Tumour Imaging Protocol (BACTIP). The final diagnosis and outcome were reviewed to establish an appropriate imaging protocol for the management of similar cases in the future. RESULTS: The final diagnosis based on imaging alone or imaging and histopathology was enchondroma in 46 cases (96%) and atypical cartilage tumour (ACT)/low-grade chondrosarcoma in two (4%). Using the BACTIP classification, the majority were type IC (48%) with type IA the second commonest (24%). Of 19 that underwent follow-up MRI, only two revealed any increase in length, neither of which was shown to be malignant. No cases re-presented later with evidence of malignant transformation. CONCLUSION: There has been a significant increase in the number of CCTs of the proximal fibula referred to Royal Orthopaedic Hospital, Birmingham, over the past decade. This can largely be attributed to the increased use of MRI. The majority were benign with only 4% classified as an ACT. A modified BACTIP, the Fibular Atypical Cartilage Tumour Imaging Protocol (FACTIP) is presented, indicating which cases would benefit from follow-up imaging and which require referral to a specialist orthopaedic oncology service.

The diagnostic significance of pulmonary nodules on CT thorax in chondrosarcoma of bone.

AIM: To provide a diagnostic approach to pulmonary nodules in patients with chondrosarcoma. MATERIALS AND METHODS: A search of the oncology database at a specialist orthopaedic oncology referral centre was performed to identify all patients who were treated surgically for chondrosarcoma between January 2007 and December 2018. Reports from the computed tomography (CT) examinations of the thorax of these patients were reviewed. In patients who had pulmonary nodules/metastases identified on CT, data on the primary chondrosarcoma and pulmonary nodule characteristics were collected. RESULTS: Twenty point two percent of patients had a pulmonary nodule identified on either initial or follow-up staging CT of the thorax, of which 8.1% were pulmonary metastases. Patients with grade 3 and dedifferentiated chondrosarcoma were more likely to have pulmonary metastases than patients with grade 1/2 chondrosarcoma. The time interval to developing metastases was shorter in patients with grade 2/3 and dedifferentiated chondrosarcoma versus patients with grade 1 chondrosarcoma. A low proportion of patients with grade 1 chondrosarcoma developed metastases (12.5%), all of which were identified at the time of a local recurrence. Nodules ≥10mm, nodules with lobulate margins, nodules containing irregular or subtle calcification, and nodules seen bilaterally or both centrally and peripherally were more likely to represent pulmonary metastases than benign nodules. CONCLUSION: The diagnostic significance of pulmonary nodules (i.e., whether they represent pulmonary metastases or not) can be predicted by taking into account a number of factors, in particular, the histological grade of the patient's chondrosarcoma, the size and margins of the nodules, and the presence of subtle/irregular calcification.

Osteochondroma-induced pseudoaneurysms of the extremities mimicking sarcoma: a report of seven contemporary and one historical case.

AIM: To provide a diagnostic approach to distinguish osteochondroma-induced pseudoaneurysm from sarcoma on imaging and prevent biopsy which may be fatal. MATERIALS AND METHODS: A retrospective study of the orthopaedic oncology database was performed to identify all patients referred to specialist orthopaedic oncology service with a final diagnosis of osteochondroma-induced pseudoaneurysm. The demographics of the cohort, the anatomical location of the osteochondromas and pseudoaneurysms, and the imaging appearances were assessed. RESULTS: Seven contemporary and one historical case of osteochondroma-induced-pseudoaneurysm were identified. There were five patients with solitary osteochondroma and three cases of hereditary multiple exostosis. Five cases underwent magnetic resonance imaging (MRI) of which pulsation artefact was present in 40%. On MRI, all the present cases demonstrated a small central pseudoaneurysm surrounded by multiple eccentric layers of thrombus and haemorrhage, which was termed the "eccentric-whorl sign". CONCLUSION: Osteochondroma-induced pseudoaneurysms are often misdiagnosed as malignant transformation of an osteochondroma or a soft-tissue sarcoma and referred for urgent biopsy. This study presents the largest case series, which includes the first documented case diagnosed in 1934. Differentiating and characterising pseudoaneurysms from sarcomas is imperative in order to prevent a biopsy, which could be fatal.

Are the tubular bones of the hand really the commonest site for an enchondroma?

AIM: To investigate whether the long-held view that the hand is the commonest site for an enchondroma is actually correct in light of more sensitive imaging techniques that are able to demonstrate small enchondromas at other skeletal sites. MATERIALS AND METHODS: A two-part retrospective study was undertaken. Part 1 comprised a review of the hand radiographs obtained in two major teaching hospitals over a 10-year period to establish the incidence of enchondroma in the hand. Part 2 was a review of a series of enchondromas of the proximal humerus, distal femur, and proximal tibia <4 cm in length on magnetic resonance imaging (MRI) to see which cases were visible or not on corresponding radiographs. RESULTS: Part 1: 84 enchondromas were identified on 116,354 trauma radiographs to give an incidence of 0.07%. Part 2: 157 patients with an enchondroma on MRI <4 cm were reviewed. Only 17% of lesions <2 cm in length were visible on the contemporaneous radiographs. In lesions that were 2-2.9 and 3-3.9 cm the percentage visible on the radiographs increased to 58 and 77%, respectively. CONCLUSION: It is well recognised from existing studies that incidental enchondromas can be seen in approximately 2.5% of routine shoulder and knee MRI scans. This figure is 35 times higher than the incidence found in the series of hand trauma radiographs. This infers that the hand should no longer be considered as the commonest site for an enchondroma. This is because radiographs are relatively insensitive to the detection of small lesions in larger bones, such as the proximal humerus and around the knee, when compared with MRI.

Psoas muscle atrophy following unilateral hip arthroplasty.

BACKGROUND: Studies have demonstrated the presence of muscle atrophy around the hip in patients with hip osteoarthritis. Few studies have examined the psoas muscle or assessed it at a paraspinal level in patients post-total hip arthroplasty. The aim of this study was to determine if there is significant psoas muscle atrophy as indicated by muscle cross-sectional area and high degree of fat infiltration post-unilateral hip arthroplasty. METHODS: Retrospective analysis of 341 patients with unilateral hip implant and subsequent lumbar spine MRI over a 8-year period was performed. Fat infiltration and cross-sectional area of the psoas muscle at L3/4 level were measured by two musculoskeletal fellows (1 year experience in musculoskeletal radiology), and comparison made between the implant and non-operative sides was made. Fat infiltration was measured using the modified Goutallier grading. The degree of hip osteoarthritis in the non-operative side was measured using the Kellgren-Lawrence grading. The data was analysed using paired t test, ANOVA, unpaired t test, Pearson correlation and Jonckheere-Terpstra test. RESULTS: The cross-sectional area of the psoas muscle on the implant side was significantly less than the non-operative side. There was significance between the cross-sectional area difference and the fat grade of the implant side. CONCLUSION: Our results demonstrate psoas atrophy on the implant side compared to the non-operative side in post-unilateral implant patients. Post-operative hip implant rehabilitation may benefit from more focused psoas strengthening exercises to improve functional outcome.

Direct MR arthrography of the shoulder: current practice in the UK.

There is wide variation in the technique and type of contrast used for MR arthrography of shoulder. In this article, we discuss the current practice in UK and the reason for the change over the last few years.

A pragmatic approach to the imaging and follow-up of solitary central cartilage tumours of the proximal humerus and knee.

Central cartilage tumours of bone range from the benign enchondroma to the malignant chondrosarcoma. They are an incidental finding in up to 2.8% of routine magnetic resonance imaging (MRI) examinations performed of the shoulder and knee. The purpose of this review is to provide a current appraisal of the imaging and histological challenges of distinguishing enchondroma from low-grade chondrosarcoma. The general radiologist, encountering these lesions in the proximal humerus and around the knee, is introduced to the Birmingham Atypical Cartilage Tumour Imaging Protocol (BACTIP). This provides a guide to the initial assessment and diagnosis, a stepwise imaging follow-up plan, and the indications for onward specialist orthopaedic oncology referral or discharge from follow-up.

A retrospective validation of an imaging protocol for the management of solitary central cartilage tumours of the proximal humerus and around the knee.

AIM: To validate an imaging protocol for the management of solitary central cartilage tumours (CCTs) of the proximal humerus and around the knee. MATERIALS AND METHODS: Over a 10-year period, 387 patients were identified with a CCT in the proximal humerus, distal femur, and proximal tibia, who were referred to a single unit either from primary/secondary care or tertiary care directly to Royal Orthopaedic Hospital, a specialist orthopaedic oncology service. The initial magnetic resonance imaging (MRI) images and any follow-up images were evaluated for length of tumour, presence/absence of endosteal scalloping, or aggressive/malignant features. The cases were categorised into one of seven types according to the Birmingham Atypical Cartilage Tumour Imaging Protocol (BACTIP). The outcome in the cases was assessed to ascertain if application of the protocol would have led to any delay in the diagnosis of malignant transformation to a chondrosarcoma. RESULTS: The incidence of malignancy (chondrosarcoma) increased with ascending BACTIP. There was a 100% benign diagnosis (enchondroma) in types IA and IB, 96% in IIA, and 83% in IIB. Fifty-seven percent of type IIC and 97% type III were diagnosed as malignant. In only one case would the application of the protocol have led to a 5-month delay in the diagnosis of chondrosarcoma. CONCLUSIONS: This retrospective study confirms the BACTIP as a useful tool for the general radiologist in the initial assessment of CCT in the proximal humerus and around the knee with the exception of the proximal fibula. In particular, determining which cases need prompt referral to a specialist orthopaedic oncology service for further assessment.

"Flow-void" sign in osseous metastatic renal cell carcinoma.

AIM: To evaluate the frequency of the "flow-void" sign in a large series of pathologically proven renal cell carcinoma (RCC) bone metastases referred to a specialist unit and to evaluate its correlation with both lesion size and imaging sequence. A further aim was to describe a proposed grading system for the description of the "flow-void" sign. MATERIALS AND METHODS: A retrospective review of patients with magnetic resonance imaging (MRI) of pathologically proven RCC bone metastases between September 2007 and December 2017 was performed. MRI images were reviewed for the presence of the "flow-void" sign and a proposed grading system for this sign was applied. Statistical analysis was performed to determine the association between the presence of the "flow-void" sign and lesion size and MRI sequence. RESULTS: One hundred and forty bone lesions in 123 patients with histologically proven metastatic RCC were reviewed. One hundred and thirty-two (94.3%) lesions demonstrated the "flow-void" sign on at least one sequence in each study. A statistically significant difference was demonstrated between lesion size and the presence and type of "flow-void" sign. Lesions demonstrating type 3 "flow-void" sign had mean dimensions of 82.2 mm compared to 47.3 mm for lesions that did not demonstrate the "flow-void" sign (χ2(2) =11.4; p=0.01). T2-weighted, proton density and fat-saturated imaging also demonstrated the "flow-void" sign more frequently. CONCLUSION: The "flow-void" sign is a common imaging feature within RCC bone metastases. When observed, the "flow-void" sign can be a useful imaging feature in the diagnosis of RCC bone metastases.

What are the differentiating clinical and MRI-features of enchondromas from low-grade chondrosarcomas?

OBJECTIVES: To evaluate the role of clinical assessment, conventional and dynamic contrast-enhanced MRI in differentiating enchondromas from chondrosarcomas of long bone. METHODS: The following clinical and MRI findings were assessed: age, gender, pain, pain attributable to lesion, tumour location, tumour length, presence, depth of endosteal scalloping, bone marrow oedema, soft tissue oedema, cortical destruction, periosteal reaction, bone expansion, macroscopic fat, calcification, soft tissue mass, haemorrhage, dynamic contrast-enhanced MRI. Clinical and MRI findings were compared with histopathological grading. RESULTS: Sixty patients with central chondroid tumours were included (27 enchondromas, 10 cartilaginous lesions of unknown malignant potential, 15 grade 1 chondrosarcomas, 8 high-grade chondrosarcomas). Pain attributed to lesion, tumour length, endosteal scalloping > 2/3, cortical destruction, bone expansion and soft tissue mass were differentiating features between enchondromas and grade 1 chondrosarcomas. Dynamic contrast-enhanced MRI could not differentiate enchondromas from grade 1 chondrosarcomas. CONCLUSIONS: Previously reported imaging signs of chondrosarcomas are useful in the diagnosis of grade 1 lesions but have lower sensitivity than in higher grade lesions. Deep endosteal scalloping is the most sensitive imaging sign of grade 1 chondrosarcomas. Pain due to the lesion is an important clinical sign of grade 1 chondrosarcomas. Dynamic contrast-enhanced MRI is not useful in differentiating enchondromas from grade 1 chondrosarcomas. KEY POINTS: • Differentiation of enchondroma from low-grade chondrosarcoma is challenging for radiologists and pathologists. • The utility of clinical assessment, conventional and dynamic contrast-enhanced MRI was uncertain. • Clinical assessment and conventional MRI aid in differentiating enchondromas from low-grade chondrosarcoma. • Dynamic contrast-enhanced MRI cannot differentiate enchondromas from grade 1 chondrosarcoma.

Current concept in upright spinal MRI.

Magnetic resonance imaging (MRI) is the established technique for evaluating the spine. Unfortunately, the supine position of the patient during conventional MRI scanning does not truly reflect the physiological forces experienced by the discoligamentous structures during normal upright posture and ambulation. Upright MRI is a relatively new technique that allows the patient to be scanned in several different weight-bearing positions, which may potentially demonstrate occult pathology not visualised in the supine position. The imaging technique and current clinical indications of upright spinal MRI would be discussed.

Correction to: Current concept in upright spinal MRI.

Unfortunately, the legend of Fig. 5 was incorrectly published in original publication. The corrected legend is given below.

A diagnostic approach to popliteal fossa masses.

There is a myriad of potential mass lesions that occur in the popliteal fossa, which present as palpable masses or are found incidentally on imaging. With a thorough knowledge and understanding of the appearances and locations of these different entities, one can narrow the differential diagnoses in the majority of cases. This will eliminate unnecessary additional investigations and enable a more rapid management. We present a review of frequently encountered and less common entities using an anatomical sieve, with the aim of providing a diagnostic approach to popliteal fossa masses.

The rising root sign: the magnetic resonance appearances of post-operative spinal subdural extra-arachnoid collections.

We present a case series of symptomatic post-operative spinal subdural extra-arachnoid collections that displace the cauda equina roots anteriorly. This is described as the "rising root sign".

Chemical shift MRI can aid in the diagnosis of indeterminate skeletal lesions of the spine.

OBJECTIVES: To evaluate the role of chemical shift MRI in the characterisation of indeterminate skeletal lesions of the spine as benign or malignant. METHODS: Fifty-five patients (mean age 54.7 years) with 57 indeterminate skeletal lesions of the spine were included in this retrospective study. In addition to conventional MRI at 3 T which included at least sagittal T1WI and T2WI/STIR sequences, patients underwent chemical shift MRI. A cut-off value with a signal drop-out of 20 % was used to differentiate benign lesions from malignant lesions (signal drop-out <20 % being malignant). RESULTS: There were 45 benign lesions and 12 malignant lesions. Chemical shift imaging correctly diagnosed 33 of 45 lesions as benign and 11 of 12 lesions as malignant. In contrast, there were 12 false positive cases and 1 false negative case based on chemical shift MRI. This yielded a sensitivity of 91.7 %, a specificity of 73.3 %, a negative predictive value of 97.1 %, a positive predictive value of 47.8 % and a diagnostic accuracy of 82.5 %. CONCLUSIONS: Chemical shift MRI can aid in the characterisation of indeterminate skeletal lesions of the spine in view of its high sensitivity in diagnosing malignant lesions. Chemical shift MRI can potentially avoid biopsy in a considerable percentage of patients with benign skeletal lesions of the spine. KEY POINTS: • Differentiating benign from malignant skeletal lesions of the spine can be challenging. • Utility of chemical shift MRI in characterising indeterminate spinal lesion is unreported. • This study demonstrates sensitivity 91.7 %, specificity 73.3 %, diagnostic accuracy 82.5 % for CSI. • CSI is useful in differentiating benign from malignant skeletal spine lesions. • Biopsy can potentially be avoided in some patients with benign skeletal lesions.

Heterotopic ossification related to the radial tuberosity: a tumour mimic.

AIM: To present the imaging features of heterotopic ossification (HO) related to the radial tuberosity initially referred as a suspected sarcoma. MATERIALS AND METHODS: Local institutional review board approval was obtained. A retrospective search of the oncology database was conducted to identify cases of ossification related to the radial tuberosity, referred to the supra-regional orthopaedic oncology centre as a suspected sarcoma. Furthermore, cases of soft-tissue sarcoma (STS) of the proximal forearm were also identified. The imaging findings were reviewed for all relevant cases. RESULTS: Over a 10-year period, 50 cases of STS of the forearm were identified with 23 involving the proximal forearm. STS was intimately related to the radial tuberosity in 52% (12/23) of these cases. There was no calcification or ossification related to the radial tuberosity in any of these sarcomas. During the same 10-year period, five cases of HO related to the radial tuberosity were identified. Demographics of these five cases revealed no significant sex predominance with a median age of 60 years. No obvious precipitating cause or predisposing condition was demonstrated. All five cases had radiographic evidence of ossification ranging from 20-53 mm in maximal dimension. Apart from one patient who had extensive ossification extending up the distal biceps tendon, the biceps tendon was otherwise normal on magnetic resonance imaging (MRI). There was only one case of mild osseous oedema of the proximal radius. CONCLUSION: No STS adjacent to the radial tuberosity was associated with ossification related to the radial tuberosity. Ossification related to the radial tuberosity is a benign entity and radiologists need to be aware of this tumour mimic.