MSK Practice Cases
MSK cases are not as challenging as GI and Chest for spotting the abnormality. They are often the starter case in the exam. However, the findings can sometimes be subtle. Please use these cases to build up technique on the basics. There are also a few banana skins we have to be careful about.
Case 1: Model Answer and Analysis
Description Single view plain film in an adult patient of the lower limb demonstrates a permeative appearance of the bony medulla. There is lamellated periosteal reaction and sub periosteal resorption. No acute fracture. The differential diagnosis is between an aggressive bony neoplasm or a metabolic syndrome such as hyper-parathyroidism resulting in brown tumours.
How can you confirm the diagnosis of hyperparathyroidism Calcium levels, PTH levels and history of renal disease.
What else can be done to confirm the diagnosis Biopsy
If malignancy was suspected what are the options 1. Bone scan 2.Staging CT examination.
Commentary This is a case of a diffuse neoplastic process.
Tips 1.Abnormal bone has a higher risk of fracture, so double check for a pathological fracture. 2.Advanced renal bone disease can look like malignancy so useful to mention this in the differential diagnosis and consider this condition.
Case 2: 87 year old admitted after being found on the floor
Case 2: Model Answer and Analysis
Description Pelvic radiograph of an adult patient demonstrates bilateral hip prosthesis. No clips are present to suggest these are recent operations. The right hip prosthesis is not sitting in the acetabulum. There are loose bony fragments inferior to the right acetabulum. The appearance on imaging is suggestive of displacement of the joint secondary to a fracture. No soft tissue swelling is identified. The left hip prosthesis looks appropriately positioned. In summary, fracture of right hip resulting in a displaced joint.
What are potential causes of this Either secondary to a fall or development of a lesion such as neoplasm or infected joint.
What can you do next If there was concern for infection or neoplasm I would organise a CT or MRI
Commentary This is an example of fracture of the right hip resulting in a displacement of the prosthesis
Tips Differentials for displaced prosthesis maybe malignancy, infection or fracture. Look for ancillary signs of malignancy such as pathological fracture of the prosthesis and additional bony metastasis. Look for evidence of soft tissue swelling and evidence of a abscess to support the diagnosis of a infected hip. Alternatively the MRI/CT they might show next can demonstrate this.
Case 3: 26 year old with right hip pain 4 days history
Description Pelvic Radiograph of a skeletally mature patient demonstrates left hip prosthesis. There are H shaped L4 and L5 vertebrae. The right hip joint demonstrates an abnormal bone texture particularly in the neck and femoral head. There is also abnormal texture in the right acetabulum. No acute bony injury. No destructive change. No periosteal reaction. The appearances are suggestive of a patient with sickle cell disease with concern for a right hip vascular necrosis. The patient will require referral to an orthopaedic surgeon for assessment and management.
What would you do next MRI scan of the hip to further assess the degree of abnormality
What is the management options In early disease NSAIDS, as it progresses joint injections and decompressive surgery. Final option is joint replacement.
Commentary This is an example of avascular necrosis of the right hip joint in a patient with sickle cell anaemia.
Tips This is an example of different imaging findings which can be put together to form a single diagnosis. In this case AVN in sickle cell anaemia.
· Be comfortable with the imaging of AVN and the management of this. Particularly the MRI appearance.
· Hip replacements in sickle cell disease get infected more often so you may get shown an infected hip replacement
Figure 1 is an example of H shaped vertebrae in a patient with sickle cell anaemia. You may get shown an abdominal film with splenomegaly and H shaped vertebrae ! This would be a case of sickle cell anaemia.
Case 4: 47 year old man with pain in fingers.
Case 4 Model Answer and Analysis
Description Single view x ray of right hand demonstrates abnormality within the 2nd and 3rd phalanxes. Within the DIP joints adjacent to the joint spaces there are punched out erosions with over hanging margins. The joint spaces are preserved. No soft tissue deposits. No acute bony injury. Differential Diagnosis include gout or pseudo-gout. Most Likely diagnosis is Gout
What is Gout Excess of monosodium urate in the blood stream and joint space. This results in crystal deposition in the joints. The pathognomonic feature is soft tissue tophi which are deposits of urate visible on x ray.
How do you distinguish between Gout and Pseudo-gout Gout typically effects the big toe. Pseudo-gout affects the knees mainly. Pseudo-gout involves the deposition of calcium pyrophosphate dehydrate crystals (CPPD).
What are the complications of Gout Burisitis of the olecranon? Avascular necrosis.
Commentary This is an example of gout in an adult patient.
Tips Be aware of the different inflammatory arthropathy conditions and the image manifestations of these disease. Useful to develop stock reports in your head to present these conditions in the exam. Also be comfortable with the complications of this condition. This should not be a difficult case to present.
Case 5: History of trauma to the hand.
Case 5 Model Answer and Analysis
Description Single view radiograph of an adult patient demonstrating abnormal bone texture of the 3rd finger proximal phalanx. There is expansion of the phalanx with ground glass change within. No lucency. No periosteal reaction. No bone destruction. No acute bony injury. The appearance on imaging is suggestive of a benign process. I think this is fibrous dysplasia. No additional lesions identified.
What would you do next Report it as a benign lesion and not recommend further tests.
If there was concern for a fracture, what can you do Recommend orthopaedic consultation to guide the patients care. Treat this conservatively and perform a repeat X ray in 3-4 days.
Commentary This is an example of fibrous dysplasia, a benign condition
Tips Do not fall into the trap of thinking this is an aggressive process. If you see a fracture manage this conservatively.
Be aware of the association of fibrous dysplasia such as Mc Cune Albright syndrome, metabolic conditions such as hyperparathyroidism. You maybe shown a pelvic x ray with fibrous dysplasia and renal stones!
Case 6: 45 year old swelling of the left arm.
Case 6 Model Answer and Analysis
Description X rays of the upper arm in a skeletally mature patient, demonstrates deformity of the radius with an abnormal expansile lucency localised to the proximal metaphysis. This contains multiple lesions which have well defined borders and rings and arc calcification. No periosteal reaction. No associated fractures. No soft tissue lesions demonstrated. I suspect this represents a benign pathology. The appearances are suggestive of multiple enchondromata-Olliers disease.
What would you do next There is deformity of the limb, which maybe have impact on the patients mobility. Suggest orthopaedic consultation.
Would you do any further tests to assess this There is an association of chondrosarcoma occurring in patients with this condition but there are no imaging features for this. If there is clinical concern for chondrosarcoma then I would recommend MRI and orthopaedic consultation for assessment.
Commentary This is an example of multiple enchondromas-Olliers disease
Tips This is a benign lesion. If there was soft tissue hemangioma the appearance would be in keeping with maffuci syndrome. Do not get tripped into calling this an aggressive lesion as this does not have any of the image features of a invasive process. The examiner may show an MRI of this. It is helpful to review images of a chondrosarcoma.
Case 7: No history
Case 7 Model Answer and Analysis
Description Single view of the hand in an adult patient demonstrates re-sorption of all the tufts of the phalanxes. No soft tissue swelling. No acute bony injury. Normal joint spaces. Three differential diagnosis for this include scleroderma, psoriatic arthropathy and secondary to drugs.
What would you do next Treat the underlying cause. If there was suspicion of scleroderma the patient may have pulmonary manifestations of this disease. Pulmonary features include lower lobe fibrosis. Oesophageal dysmotility may lead to aspiration pneumonia.
Commentary This is an example of gross acro-osteolysis.
Tips This is a relatively straight forward case. Do not get confused with bony metastasis. Be comfortable with the different manifestations of scleroderma and sarcoid including the chest.
Case 8: 67 year old long standing deformity of the arm
Case 8 Model Answer and Analysis
Description Single view of the arm in an adult patient demonstrates expansion of the humerous, radius and ulna with a ground glass appearance. Narrow zone of transition. No periosteal reaction. No fracture. There is a similar appearance of the ribs. No rib fracture noted. The appearance on imaging is suggestive of a benign process most likely fibrous dysplasia. Given the multi-focal involvement this may represent Mc-Cune Albright syndrome.
What else can you do Mc-cune Albright syndrome is associated with endocrine disorders and café-au-lait pigmentation. If this is the first diagnosis on the basis of the film, the patient may require work up for this condition to look for other problems.
Would you work up this bone problem The bone disorder is a benign condition although there is gross deformity and the patient may require surgical intervention to repair the bone.
Commentary This is an example of fibrous dysplasia.
Tips This is a nice example of multi-focal abnormality involving multiple joints. The key is satisfaction of search to spot all the areas. Look at the other things. The grossness of the involvement initially is a bit. Go through the rules of benign and aggressive process and exclude an aggressive process first.
Case 9: Reduced movement in the right shoulder.
Case 9 Model Answer and Analysis
Description Radiograph of the shoulder joint in a skeletally mature patient. There is abnormal lucency of the humeral head with lucency which has ill defined margins. There is cortical destruction with periosteal calcification. No pathological fracture but the appearance on imaging is in keeping with an aggressive process. Looking at the visualised lung I cannot see any lung lesions or second bone lesion. Differentials include either a metastasis or primary neoplasm such as a sarcoma. I would like to check if there is a history of an existing malignancy. If no recorded malignancy is present in the clinical documentation I would urgently convey the findings to referring physician and suggest a staging CT chest, abdomen and pelvis as well as an MRI of the shoulder joint.
Would you biopsy this lesion Yes, but ideally in a specialist centre. The biopsy can be percutaneous or excisional but should be planned in a manner that the area biopsied can be excised during surgery to reduce the risk of tumour seeding. Coaxial needle system may be used to used to decrease needle seeding, in this a coaxial needle is placed at the edge of the lesion and then the biopsies are taken through this coaxial needle. In this manner, the needle traversing the superficial soft tissue is not exposed to the cells from the area of biopsy.
What is the value of MRI Accurate local staging with superior visualisation of the bony involvement, soft tissues and vessels. Contrast is also helpful for this.
What are the normal MRI signal intensities of a sarcoma
T1-intermediate signal intensity to muscle and on T2-high signal intensity to joints.
Commentary This is an example of sarcoma of the shoulder joint
Tips This is an example of an aggressive bony lesion. Presenting this should be simple and straight forward. The examiner may move onto a CT scan or an MRI. However, it is useful to check the remainder of the film in this type of case for a second lesion on the plain film.
Case 10: Model Answer and Analysis
Description Radiographs of the lower limb in a skeletal immature patient demonstrates an expansile area of bony lucency localised to the metaphysis adjacent to the growth plate. This has well defined borders with a narrow zone of transition. No periosteal reaction. No soft tissue swelling. No fractures appreciated. Appearances are in keeping with a benign lesion. I think the image appearances are in keeping with a non ossifying fibroma.
What would you do next This is a benign self limiting lesion so I would not do anything else.
If the lesion was larger would you be concerned For large NOF, there is an increased risk of pathological fracture, I would in that instance suggest orthopaedic review for further assessment.
Commentary This is an example of a non ossifying fibroma
Tips This should be a straight forward case of a benign NOF. Look for ancillary evidence of problems such as a fracture and remember if you get an example of a benign appearing bone lesion with a fracture it does not mean there is a neoplasm! The advice should be orthopaedic referral and management of the acute bony injury.
Case 11: GP referral for suspicion of OA.
Case 11: Model Answer and Analysis
Description Hip Radiograph of an adult patient demonstrates an avulsion fracture of the right anterior superior iliac spine. The anterior superior iliac spine and adjacent pelvis has abnormal bone texture. There is localised bony expansion, thickened cortex with coarsened trabecula. No bony destruction. No abnormal bone lucency. The appearance is suggestive of underlying pagets disease. In summary I suspect this is a pathological fracture. I would recommend referring the patient for management of the fracture to an orthopaedic surgeon.
What you be concerned for a neoplastic process Pagets is a benign lesion. No evidence of malignant transformation on this study. This does not require work up.
Would you perform an MRI scan No specific features of malignancy on this plain film. However, if there is clinical concern for malignancy i.e. bone pain out of proportion to the pain of the fracture, weight loss, no clear mechanism of injury to explain the fracture an MRI scan maybe helpful
What other tests can be done to assess for Pagets Alkaline phosphatase.
Commentary Pathological fracture of the right anterior superior iliac spine
Tips This is a plain film with two abnormalities. Pagets and a fracture. Do not fall into the trap of thinking this is a neoplastic process. Malignant transformation is a separate entity, do not fall into the trap of thinking this is malignancy. People with pagets are more at risk of fracture compared to normal patients.
Case 12: Unable to stand 67 year old lady.
Case 12: Model Answer and Analysis
Description Radiograph of the pelvis in an adult patient. This demonstrates a fracture of the left neck of femur. There is abnormal bone lucency in the adjacent neck of femur. No evidence of bony degenerative process. No additional bony lesions. No additional fractures. The appearance is suggestive of a pathological fracture. This can either represent a metastasis or primary local neoplasm. I would recommend an MRI scan to assess this area further and if there was no history of an existing malignancy suggest a CT scan of the chest, abdomen and pelvis for further assessment.
What local neoplasm can cause this Sarcoma and plasmacytoma. There is no exuberant periosteal reaction or soft tissue swelling, locally.
Commentary This is an example of a pathological fracture of the left hip.
Tips In contrast to the other case in this packet, this is an example of a pathological fracture. This will require a work up and further assessment. The examiner may show a CT scan looking for a primary cause or an MRI to assess this area further.
Case 13: 39 year old with long standing leg problem presents with pain following knock
Case 13: Model Answer and Analysis
Description Radiographs of the lower leg in an adult patient demonstrating resorption of the mid aspect of the fibula. The adjacent bone is corticated. The appearance on imaging is of a pseudoarthrosis. The top differential diagnosis are Neurofibromatosis type 1, failed bone graft or non union of a fracture.
What would you do next Management depends on the underlying cause. The patient requires an orthopaedic Consult assuming they are not under the care of one already. Neurofibromatosis is a poly-syndromic condition which has extensive disease manifestation. If there is no other potential cause for this i.e. a fracture or previous attempt at Bone Union then the patient will require referral and assessment for this.
What are the Treatment options for Pseudoarthrosis Bone grafting, external fixation, depends on the nature of the case.
Commentary Pseudoarthrosis of the joint.
Tips This is an example of a pseudoarthrosis. Be able to describe it. If you suggest an orthopaedic Consult, the examiner may show you a MRI of a pseudoarthrosis. It might be helpful to see an example of this. Unfortunately I do not have an example of an MRI of this condition.
Case 14: Pain in fingers for several months.
Case 14: Model Answer and Analysis
Description Radiographs of the hand in a skeletally mature patient. There is abnormal bone texture of the thumb distal phalanx, 2nd digit proximal phalanx and 3rd digit intermediate phalanx. All of these joints demonstrate coarse bone texture with a lace like configuration. There is sub-periosteal bone resorption. No fracture. No periosteal reaction. No bony destruction or erosion. The joint spaces are all preserved. No soft tissue swelling. Most likely differential diagnosis is sarcoid of the hand. Differential diagnosis include scleroderma.
Image feature of sarcoid of the hand?
This can be variable but includes
- Punched out lytic lesions.
- Lace like destruction
- Bone destruction with fractures
- Sub-periosteal bone resorption
How would you manage this condition? Treat the underlying cause and symptomatic management of hand disease. There is a high association of involvement of the chest. Clinical correlation is suggested to assess for this.
Commentary This is an example of sarcoidosis of the hand.
Tips This is an example of sarcoid of the hand, with the abnormality affecting multiple joints. The method of presenting the case I have suggested in this case is to first identify the locations of abnormality, in this case the digits affected and then describe the nature of the abnormality. The alternate method is to describe each joint individually. This seems more cumbersome. I have advocated presenting significant positives and significant negatives. The offering differentials. Difficult to guess the questions the examiner may ask but provided you do not get tripped into thinking this is a neoplastic process this case may come up and go down. However, it is useful to know the image features of this condition.
Case 15: Model Answer and Analysis
Description Lateral skull X ray in an adult patient. There are two lytic lesions within skull. The larger lesion is located adjacent to the cortex. The margins are ill defined inferiorly. No destruction of the cortex. No periosteal reaction or visible fracture. The appearance is concerning for either a lytic bone metastasis or a primary neoplasm such as a plasmacytoma. Further characterisation with an MRI Head scan is suggested. The patient will also need a staging CT chest, abdomen and pelvis for assessment.
What features would help to diagnose Plasmacytoma Plasmacytoma is a tumour of plasma cells growing either in the soft tissues or axial skeleton. Features on imaging to support this would be a solitary lesion with a lytic and soft tissue component. Bone destruction is a non specific additional feature as this is seen in other malignancies. Additional features on imaging that would support this diagnosis is the absence of a proven malignancy
What tests can you do to help with diagnosis Non invasive tests such as Bence Jones Protein, serum electrophoresis- looking for para proteins. A bone scan could be helpful as Myeloma/Plasmacytoma are photopenic. Invasive tests such as Biopsy.
Commentary This lateral skull film is an example of plasmacytoma.
Tips The key is not to go down the route of a benign lesion on a case like this i.e. lytic lesion with well defined margins, no periosteal reaction no soft tissue mass, I suspect this is benign and would do no further tests. Approach the case systematically.
Case 16: Model Answer and Analysis
Description Single image of a hand Radiograph in an adult patient which demonstrates osteosclerosis of the tufts. No bone erosions. No bony destruction. No fractures. The remainder of the joint appears normal. Differential diagnosis include inflammatory arthropathy such as systemic sclerosis and rheumatoid arthritis. Another differential diagnosis is sickle cell disease.
What would you do next The finding needs to be correlated with clinical assessment to identify the underlying cause.
Commentary This is an example of sclerosis of the distal tufts of the fingers. There is no single diagnosis but differentials.
Tips Look for evidence to support one differential diagnosis. Do not recommend MRI, CT etc for further assessment. The exam is about being safe and sensible.
Case 17: Model Answer and Analysis
Description Single Radiograph of the upper arm in a skeletally immature demonstrates abnormal bone texture within the proximal metaphyses with sclerotic and permeative change. There is a sun burst periosteal reaction. No fracture appreciated. The appearance is in keeping with an aggressive process. My main differential diagnosis is a bone sarcoma. I would recommend urgent orthopaedic referral for assessment.
What would you do next
1. Recommend MRI for assessment with IV Dotarem
2. Staging CT investigation of the chest, abdomen and pelvis
Commentary This is an example of a bony sarcoma
Tips This is a straightforward case of an aggressive process. Always double check for a pathological fracture. Increasingly they are showing CT and MRI studies in the exam. It is useful to review an MRI of an aggressive bone process and perhaps discuss with an MSK specialist on the sequences used.
Case 18: Model Answer and Analysis
Description Radiograph of the left hip in an adult patient demonstrating abnormal lucency within the femoral neck. This has well defined margins with a clear zone of transition. There is ground glass matrix. No periosteal reaction. No fracture. No soft tissue swelling. No additional lesions noted. The appearance on imaging is suggestive of a non-aggressive process. The most likely differential diagnosis is fibrous dysplasia.
What would you do next I would not recommend follow up imaging or assessment of this lesion as this appears benign in nature.
If there were multiple lesions would you do anything different
Polystatic fibrous dysplasia has associations with two major conditions
Mazabraud Syndrome-multi-focal fibrous dysplasia and soft tissue myxoma which have the potential for malignant transformation.
Mc Cune Albright syndrome-this has association with endocrine problems such as precious puberty.
Fibrous dysplasia is a non malignant condition but the associated problems with this may require clinical care.
Commentary This is an example of fibrous dysplasia of the femoral head
Tips This is an example of fibrous dysplasia. I have heard of several candidates being tripped up by a case like this in the exam and going down the route of an aggressive process suggestive MRI, biopsy etc. Remember features of a benign bone lesion aggressive lesion. This does not have the features of a sinister condition.