Purpose
At the elbow level,
the radial nerve splits into the radial sensory nerve and the posterior interosseous nerve (PIN) proximal to the supinator muscle.
The PIN is predominantly motor and,
passes beneath several potential compressing structures as it crosses the elbow,
including the proximal aponeurotic edge of the supinator,
which is commonly referred to as the arcade of Frohse,
the sharp medial border of the extensor carpi radialis brevis,
the radial recurrent blood vessels and the inferior edge of the superficial layer of the supinator...
Methods and Materials
Anatomic Study
A dissection study was performed on n=3 fresh frozen elbow specimens to assess the regional anatomy of the PIN and its divisional branches at the distal edge of the supinator muscle.
They were thawed at room temperature immediately prior to the study and evaluated with ultrasound before starting dissection.
At the distal edge of the supinator muscle the PIN was targeted for US guided injection.
Each injection was performed using a sonographically guided,
in-plane approach,
targeting the presumed vertical segment with a 22...
Results
In all cadaveric specimens,
gross anatomy revealed the PIN splitting into two divisional branches after exiting the distal gate of the supinator tunnel.
The first continued on the same course of the main trunk straight down in the dorsal compartment of the forearm to supply the regional extensor muscles.
The second was shorter and had a curved recurrent course going to supply the extensor digitorum communis (Fig.
1).
Visualization for US-guided latex injection was excellent in all specimens using the 17-5MHz transducer.
In all three...
Conclusion
Despite the clinical importance of detecting the exact level of entrapment in the context of patients presenting with posterior interosseous neuropathy,
no prior study has formally investigated the ability of US to identify cases of distal compression of the PIN at the inferior edge of the superficial belly of the supinator muscle using currently available,
high-resolution US probes.
Based on our series,
the PIN entrapment at the distal edge of the supinator tunnel was found to be relatively common,
accounting for approximately 19% of cases....
References
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