Radiology Level: FRCR, FRCS, MRCP, ABR, EDiR, Radiology Junior +

The initial images are from an MRCP (magnetic resonance cholangiopancreatography) examination. The images on the left are T2 axial images, the images on the right from a FIESTA sequence (equivalent to FISP/TRUEFISP sequence, T2 predominant-although actually ratio of T2/T1- fat suppressed, bright blood sequence) demonstrating that the gallbladder is completely packed with low signal abnormalities consistent with stones.  There is no apparent gallbladder wall thickening, oedema or pericholecystic inflammation.  These appearances indicate chronic gallstone disease.

It is important, however, to carefully review the remainder of the biliary tree. Hopefully, on such a review you would have also assessed the common bile duct which can be seen in the head of the pancreas (short narrow).  This is mildly dilated but additionally on both the images dependent low signal abnormality can be identified consistent with bile duct stones i.e. choledocholithiasis.  The presence of gallstones within the bile duct is an important parameter to indicate prior to laparoscopic surgery to ensure that the duct is cleared.

The appearances are very evident on the oblique T2-weighted radial ray projection (left).  In this image it is perhaps easy to not see the gallbladder due to the loss of high T2 signal caused by multiple gallstones (long narrow).  In this instance the choledocholithiasis is easily appreciated (short narrow).  These are also appreciated on coronal SSFSE (single shot fast spin echo) acquired through the gallbladder and the lower biliary tree.

In identifying extrahepatic duct choledocholithiasis, particularly single stones, it is important to exclude artefact related to flow.  Flow artefacts do appear central and are not consistent whereas choledocholithiasis is typically dependent and reproducible on more than one sequence. A typical site for flow artefacts is also at the crossover of the right hepatic artery over the common hepatic duct near the hepatic duct confluence.

Abdominal pain and fever.
Easy! Careful...
Radiology Level: FRCR, FRCS, MRCP, ABR, EDiR, Radiology Junior +

Radiology Level: FRCR, FRCS, MRCP, ABR, EDiR, Radiology Junior +

The images demonstrate a pair of cervical spine radiographs. The image on the left is in extension the image on the right in flexion. Both images are adequate visualising to C7-T1 or lower. The extension image demonstrates that there is some moderate degenerative change with sclerosis and joint space reduction at C5-C6. The flexion film demonstrates that there is straightening of the cervical spine at this level in flexion. There is, however, no spondylolisthesis (slip).

Looking more carefully at the atlanto (C1) –axial (C2) articulation, we can see that in extension the anterior margin of the dens can be traced superiorly to the skull base (blue line). The predental space (also called atlantodental or predentate space) measures only 2mm (red line). In flexion though the predental space greatly increases  to >7mm. The appearances are those of non-traumatic atlanto-axial subluxation/dislocation. In addition there is some loss of clarity of the odontoid peg (confirmed on MRI/CT) suggesting some erosion. These appearances were due to rheumatoid disease. The patient was being assessed pre-operatively.

Typically the predental space is usually <=3mm in neutral or extension radiographs, <=5mm in children. In children the ligamentous laxity of the neck in flexion allows some minor increase of this space, but not in adults. The anterior motion of the atlas on the axis/dens is typically restricted by the transverse ligament. The disruption of this ligament can occur by trauma (look for associated fractures or prevertebral soft tissue swelling) or by inflammatory conditions (typically rheumatoid disease but also less commonly psoriasis, Down’s and Morquio’s syndromes, Neurofibromatosis, Osteogenesis Imperfecta).

Disruption of the transverse ligament enables atlanto-axial instability. This can be asymptomatic or life-threatening (particularly in trauma). Specifically, posterior translation of the dens can compress the cord resulting in upper motor neuron compressive neurology. Such unexpected spinal compression may become first apparent during intubation and is, therefore, screened for in susceptible patients with rheumatoid arthritis. The condition is termed atlanto-axial instability/subluxation or dislocation and should be differentiated from atlanto-axial rotatory subluxation in which the primary injury is a rotation at C1-C2 that may be associated with unilateral facet dislocation, fractures and nerve root compression with flexed rotated angulated neck malalignment.

Radiology Level: FRCR, FRCS, MRCP, ABR, EDiR, Radiology Junior +

Radiology Level: FRCR, ABR, EDiR, MRCP, Radiology Junior +

This is a relatively simple case. The lateral and AP projection of the knee demonstrate minor degenerative changes of the knee including the patellofemoral joint. However, there is an abnormality of the distal femur. The femur demonstrates patchy diffuse sclerosis. This extends extensively beyond the articular margin of the joint and is, therefore, not related to a degenerative process. The patchy appearances may suggest an infiltrative disorder such a metastasis or a primary osteogenic lesion. However, there are other features here that suggest an alternative diagnosis.

The distal femur demonstrates thickening and coarsening of the medullary trabeculae. The cortex of the distal femur is also considerably thickened compared to the cortex of the femur. Further one can appreciate that the femur size is subtly enlarged compared to the tibia. Finally, the entirety of the femur is involved extending to involve all of the femoral condyles to the articular surface.

These are classical appearances of Paget’s disease. Paget’s disease typically involves the entirety of a single bone extending from one articular surface to the other side of the bone.  The typical appearances seen here those of coarsening of the trabeculae, cortical thickening, sclerosis and osseous enlargement. Bowing may then develop in the long bones. This is typically lateral in the femur but anterior in the tibia. Premature degenerative change is also a feature in long bones.

Paget’s disease most typically involves the pelvis although involvement of other sites including the skull, proximal long bones and vertebrae is also common. Both poly-ostotic and mono-ostotic variations can occur. The mixed osteosclerotic and osteolytic phase observed here is preceeded in some patients by a pure osteolytic phase that is often not clinically detected. This may in the long bones be associated with an advancing margin often likened to a “blade of grass” or the “candle flame sign”. A later fully sclerotic osteoblastic phase may occur.

Although there is often extensive sclerosis the serum calcium and phosphate levels are normal with increase in serum Alkaline Phosphatase or urinary hydroxyproline the only consistent biochemical findings. Clinically approximately 75% of patients are incidentally detected and asymptomatic, although local pain and even symptoms of increased heat sensation can occur with long-bone involvement. Long term the principle concerns of long bone involvement are deformity, fractures, and in approximately 1% of patients, osteosarcoma transformation. Treatment is with bisphosphonate therapy.

Radiology Level: FRCR, Radiology Junior +, ABR, EDiR, MRCP

Radiology Level: FRCR, ABR, EDiR, Radiology Junior +

This case demonstrates an asymmetrically irregular appearance of the right femoral head and neck. The right femoral neck appears excessively flexed and the right femoral head appears “mushroomed” with a flattened widened appearance. This widened metaphysis is often referred to as coxa magna. The acetabulum is more steep on the right side than on the left, suggesting a developmental cause. In combination the right femoral head is subluxed superiorly. This would result in clinical foreshortening of the right leg.

These appearances are highly suggestive of remote missed slipped capital femoral epiphysis (SCFE). SCFE is a diagnosis of prepuberty and puberty typically occurring in the acute phase in children (boys>girls) with a greater incidence in children that are overweight or are suffering from hypothyroidism, hypopituitarism or hyperparathyroidism. Metabolic associated causes may present earlier than 10 years of age and are more likely to be bilateral. Approximately 5-7% of cases have an associated familial predisposition.

The cause of the slipped capital femoral epiphysis is in essence a Salter Harris type I injury. It is thought to occur during periods of rapid growth during which the physis anatomically widens and the biomechanical stresses become more oblique and results in posteromedial slippage.

Most SCFE is picked up acutely, or even in the chronic phase (after 3 weeks of symptoms), however, if missed long term then fusion of the physis can occur in a deformed position. Chondrolysis of the articular surface can occur with premature degeneration of the hip joint. This degeneration typically occurs beyond the fifth decade. This may present as in this case with foreshortening or chronic pain.

A further complication of missed SCFE is appreciated in this case. Look carefully at the right femoral head. It is irregular in shape and mildly sclerotic. There is a small fragment of the femoral head that is separate from the remainder of the femoral head. These are appearances of avascular necrosis. Avascular necrosis is a serious complication of SCFE, and may further predispose to premature degeneration, and a reason why early diagnosis is essential. Avascular necrosis is thought to occur as a result of raised intracapsular pressure in conjunction with kinking of retinacular vessels that is thought to result in hypoxia leading to avascular necrosis. The risk of avascular necrosis appears higher in unstable SCFE (able to walk with our without crutches) compared to stable SCFE (unable to walk).

Treatment both in the acute phase and in the delayed phase id by osteotomy and pinning.

Radiology Level: FRCR, EDiR, ABR, Radiology Junior +

Case Level: Radiology Junior +, ABR, EDiR, MRCP, FRCR, FRCS

The images demonstrate a relatively obvious fracture of the ulna. This is appreciable on the AP projection and confirmed as significantly angulated on the lateral projection. However, careful review of the elbow image reveals an additional abnormality. What is it?

Whenever reviewing a paediatric elbow the first consideration is to establish that all the expected epiphyses are present. These appear in the order defined by the mnemonic of CRITOL (Capitellum, Radial head, Internal epicondyle, Trochlea, Olecranon, Lateral epicondyle). Epiphyses appearing out of order can be due to avulsion-dislocation of an epiphysis. In this case only the first epiphysis, the capitellum, in its correct position. However, the capitellum is the “cap” that lies over the radial head. In this case we can see that a line drawn through the medulla of the radius, through its expected head location does not meet the capitellum. Therefore, the findings reflect dislocation of the proximal radius/radial head.

The combination of a mid-ulnar fracture and proximal radius/radial head dislocation constitutes the eponymous fracture-dislocation combination of Monteggia. This type of fracture dislocation highlights the importance of imaging the joint above and below a fracture. These types of fracture-dislocations are difficult for most to remember. The commonly confused fracture-dislocation is that of Galeazzi. In Galeazzi there is a mid-radial fracture with dislocation of the distal ulnar head at the wrist joint. It can be frustrating to remember the fracture and where the dislocation is (bone and location) and there are many mnemonics to assist. My preference is to recall that the dislocation occurs in the non-fractured bone and to use the mnemonic of GRIMUS (Galeazzi, Radius #, Inferior dislocation, Monteggia, Ulna #, Superior dislocation). Recall that the fracture may simply be a greenstick injury but it is essential to look for the associated dislocation as these can be missed and result in chronic pain/dysfunction for the patient and medicolegal pain for the reporting radiologist!

Finally don’t forget the final fracture dislocation which is the Essex-Lopresti (one hyphenated British surgeon not 2 people!). This is a comminuted fracture of the radial head where force is transmitted down the interosseous ligament resulting in dissociation of the distal radio-ulnar joint at the wrist.

Case Level: FRCR, FRCR, FRCS, EDiR, ABR, Radiology Junior +