What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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Findings Again, please do not focus on the orthopedic instrumentation although that was thought to be the cause of the patient’s symptoms. In particular, the screw for arthroeiriesis was removed. The 5th MT fracture was not contributory. On the radiograph there is an effacement of the normal fat of Kager’s fat pad. On the MRI a “mass” with skeletal muscle architecture and signal is seen. There is an effacement of the fat posterior to the tibial nerve and a slight flattening of the nerve but otherwise normal signal intensity and architecture of the nerve as it extends distally.
What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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What’s the Diagnosis – Case 151
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Diagnosis: Accessory Soleus Muscle I hope I did not give this case away but felt it only appropriate to label this accessory muscle as a “mass” during this presentation. There are numerous accessory muscles especially around the foot and ankle. They are always diagnosed by the same signal and architecture as skeletal muscle just in an aberrant location. By in large these muscles are of no consequence but at times they may become symptomatic. Particularly as relates to this accessory muscle, it lies superficial to the flexor retinaculum and within Kager’s fat pad and hence on a radiograph a soft tissue structure is seen effacing or obliterating Kager’s fat pad. Although many other accessory muscles can be present in the posterior aspect of the ankle, most lie deep to the flexor retinaculum and hence do not produce an effacement of the fat pad. When accessory muscles are in close proximity to neurovascular structures they can cause mass effect upon these structures. In this case, the tibial nerve is adjacent to the muscle and it is easy to see how there may be mass effect upon the nerve especially if there is muscle hypertrophy. The same process occurs for the anconeus epitrochlearis and the ulnar nerve. The accessory soleus is known to have varied insertions including directly into the calcaneus and either via a tendinous or muscular attachment to the superior or medial calcaneus. As seen here, if the attachment is separate from the Achilles, it is always anterior and medial to the Achilles attachment to the calcaneus. Although knowing the names of accessory muscles is nice, recognizing them and identifying if they have mass effect upon critical structures is much more important.
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References Accessory Muscles: Anatomy, Symptoms, and Radiologic Evaluation. Paul A. Sookur, Ali M. Naraghi, Robert R. Bleakney, Rosy Jalan, Otto Chan, Lawrence M. White. Radiographics. Mar 1 2008 https://doi.org/10.1148/rg.282075064 Accessory Muscles of the Ankle. John F. Carroll, M.D. Radsource. MRI Web Clinic — November 2008
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