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Nuffield Orthopaedic Centre, Windmill Road, Headington, Oxford OX3 7LD, UK
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 Top Cases Answers |
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shows an ultrasound longitudinal view of the palpable lump. Sagittal T1 weighted MRI (Figure 1b) and sagittal short tau inversion recovery MRI (Figure 1c).
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) and short tau inversion recovery MRI (Figure 2b).
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) and short tau inversion recovery MRI (Figure 3b).
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), T2 weighted (Figure 4b) and proton density (Figure 4c) with fat saturation.
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).
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) and T1 weighted (Figure 6b) MRI of the foot.
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), proton density with fat saturation (Figure 7b) and axial T2 weighted (Figure 7c) MRI of the knee.
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) and short tau inversion recovery (Figure 8b) MRI of the foot.
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TopCasesAnswers |
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The median nerve could be followed from wrist to brachial plexus and although is not involved, it is situated immediately deep to pronator teres where it may be compressed.
Lipomas are common tumours. They consist of a well defined mass of mature fat, which appear radioleucent on plain film, low attenuation on CT and hyperintense on T1 weighted imaging. Fine septations can sometimes be seen on CT and MRI. They may calcify or ossify. Larger lesions can cause local pressure symptoms leading to erosion of underlying cortical bone and spur formation.
Answer 2
There is a lesion involving the distal radial metaphysis. The centre returns fluid signal, with a relatively thick rim of surrounding high signal on T1. This is a characteristic appearance for chronic osteomyelitis and is known as the penumbra sign. It is thought to be due to a rim of vascular tissue lining the cavity and is characteristic although not pathognomonic of chronic infection. It is useful in distinguishing an infectious lesion from tumour.
There is extensive oedema surrounding the lesion within the bone and soft tissues.
Chronic osteomyelitis is usually a consequence of an episode of acute osteomyelitis caused by an open fracture or surgery, failure to eradicate haematogenous source, or as a consequence of local spread from soft tissue infection. Plain film findings include a florid periostial reaction causing focal cortical thickening, areas of bone destruction, cortical defects and sequestrum. Pus penetrates the cortex via a cloaca which can sometimes be seen on plain film although usually CT or MRI is required. Management involves surgical removal of necrotic bone including all sequestra and administration of antibiotics.
Answer 3
There is collapse of the midfoot with disruption of the mid-tarsal joints, bony destruction and fragmentation. There is a "rockerbottom" appearance to the underside of the foot with complete loss of the normal arch. A large ulcer is present on the sole of the foot beneath the cuboid. No drainable collection is demonstrated and the marrow signal in the midfoot is relatively well preserved. The features are classical for a Charcot (neuropathic) foot.
The neuropathic foot is usually encountered in diabetic patients as a result of small vessel disease resulting in ischaemia and neuropathy. Neuroarthropathy tends to develop between the 5th and 7th decades following a period of diabetes of at least 15 years. The foot is involved in most cases with the tarsal and tarsometatarsal joints being affected in 60%. Loss of proprioception leads to an ataxic gait, and loss of pain sensation allows repeated trauma resulting in ulcers and neuroarthropathy. There are two forms of neuroarthropathy, atrophic and hypertrophic, The former is characterised by osteoporosis, bone resorption and dislocation, the latter by osteophyte formation, sclerosis, eburnation, fragmentation and dislocation.
Answer 4
Extensive oedema is seen within the subcutaneous tissues overlying the inferior patellar tendon insertion. The patellar tendon its self is thickened and there is extensive bruising throughout the anterior aspect of the proximal tibia.
The posterior cruciate ligament (PCL) is disrupted superiorly. The anterior cruciate ligament (ACL) is intact. No meniscal tears seen.
This patient shows the typical pattern of MRI abnormalities resulting from a dashboard injury where there is a direct blow to the superior tibia with the knee in flexion. PCL injuries are relatively rare as a significant force is required. The PCL may also be injured by excessive rotation or hyperextension. Isolated tears of the PCL are uncommon and are usually associated with damage to the ACL, menisci or collateral ligaments. The PCL usually tears in its mid portion. Injury to the PCL is indicated by high signal within the usually low signal ligament. There may be adjacent haemorrhage or oedema.
Answer 5
Images show peroneal tendon dislocation.
The peroneal tendons consist of peroneus longus and peroneus brevis. The tendon of peroneus longus passes behind the lateral malleolus beneath the peroneal retinaculum, passes forwards lateral to calcaneus, swings under the tarsus before inserting at the base of the first metatarsal and medial cuneiform. Peroneus brevis descends anterior to longus, passes under the lateral malleolus but then passes superior to the peroneal tuberosity to insert on the tuberosity of the fifth metatarsal.
The tendons are held in place behind the lateral malleolus with support from a fibro-osseous tunnel formed by the ankle bones, ligaments and peroneal retinaculum. Disruption of this tunnel may allow the tendons to move anteriorly. This is often associated with a small bony avulsion from the lateral aspect of the fibula.
Treatment includes surgical repair to prevent chronic instability.
Answer 6
The lateral sesamoid underlying the first metatarso-phalangeal joint demonstrates abnormal signal intensity on both T1 and T2 sequences, being low on T1 and intermediate on T2.
No other osseous abnormality. Features are consistent with sesamoiditis involving the lateral sesamoid underlying the first metatarsophalangeal joint.
Sesamoiditis is a painful inflammation of the area surrounding the sesamoid apparatus. It is common in physically active young people and is thought to be cause by repetitive excessive pressure to the forefoot. Stress fractures of the sesamoid bone can also cause this condition. Clinically it presents as a gradual onset of pain leading to pain and swelling severe enough to limit dorsi and plantar flexion of the 1st metatarsophalangeal joint and difficulty walking. Treatment is usually non invasive with rest, immobilization and the use of a pressure reducing shoe pad. Severe cases may be helped by the use of a below knee walking cast and injection of steroids.
Answer 7
Multiple loose bodies are seen within the joint. Many of these are osseous with central fat signal intensity. There is a moderate joint effusion and synovial thickening. Rudimentary osteophytes are present suggestive of early superadded degenerative change. No definite articular cartilage defects are noted. The ACL, PCL, collateral ligaments and extensor mechanism were all intact.
Multiple intra-articular loose bodies in a patient of his age with no predisposing factors suggests of a diagnosis of synovial osteochondromatosis.
Synovial osteochondromatosis develops by metaplasia of the subsynovial connective tissue. It may affect synovial joints, bursae and sometimes the tendon sheath. Multiple nodules of cartilage form in the synovium and project into the joint space. These may mineralize. Other features include loose bodies, bone erosions and secondary osteoarthritis.
Answer 8
There is a fibrous calcaneonavicular coalition. There is extensive oedema within both the anterior process of the calcaneus and the lateral aspect of the navicular adjacent to the coalition.
A diagnosis is made of calcaneonavicular coalition with stress response in the adjacent bones.
Tarsal coalition is a common cause for a painful flat foot. It most commonly occurs at the calcaneonavicular joint or the middle facet of the talocalcaneal joint. 80% are bilateral. Calcaneonavicular coalition is well seen on oblique view. However MRI or CT is required to delineate accurately the type and extent of the coalition.
Answer 9
A sialastic implant is seen replacing the scaphoid bone. Extensive synovial thickening and erosions are seen throughout the wrist. The most severe erosive changes involve the joints surrounding the silicone prosthesis.
Cysts are seen in the subcutaneous fat over the radial aspect of the scaphoid. Several hypointense foci are evident interspersed with the synovial thickening which may represent silicone particles.
MRI feature suggest a diagnosis of florid sialastic synovitis related to the scaphoid prosthesis.
Sialastic synovitis is caused by an abnormal response to the presence of a prosthesis in which shedding of particles occurs from the prosthesis as a result of shear and compressive forces. Particle synovitis can also occur in the presence of shedding metal, polyethylene and cement. Although it can occur at any site of prosthetic implant, the carpal bones of the hand are most at risk as they are more susceptible to stress forces. An inflammatory reaction occurs in response to the sloughed particles which leads to erosion of the bone, articular cartilage and intraosseous cystic changes. This may be accompanied by swelling and calcification.
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