Keywords:
Image verification, Surgery, Ultrasound, Neuroradiology peripheral nerve, Musculoskeletal system, Musculoskeletal soft tissue
Authors:
S. Airaldi1, F. Zaottini2, M. Miguel-Perez3, S. Martinez Blanco4, J. Palau3, J. Smith5, S. Gennaro1, C. Martinoli1; 1Genova/IT, 2Albisola (SV)/IT, 3Barcelona/ES, 4Burgos/ES, 5Rochester/US
DOI:
10.1594/essr2016/P-0140
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 gauge,
1.5 inch (38 mm) stainless steel needle.
In each specimen,
0.2- 0.3 ml of diluted,
blue latex (50% water,
50% latex),
was into and around the presumed nerve for localization purposes. Each specimen was then dissected to directly identify the PIN and its divisional branches and determine its relationship to the injected latex.
Clinical Study
Since January 2011 to March 2016,
we examined a series of n=32 consecutive patients (mean age,
45±12 years,
age range 24-70),
with PIN neuropathy based on clinical (ie.
fingerdrop and atrophy of the posterior forearm muscles with exclusion of the brachioradialis,
extensor carpi radialis longus and brevis and supinator,
pain along the lateral aspect of the elbow and proximal radial forearm) and neurophysiological (ie.
detection of positive sharp waves and/or fibrillation potentials,
reduction of motor unit potential amplitude) evidence.
In each patient,
the PIN was evaluated sonographically from the radial nerve bifurcation down to its divisional branches in the forearm.
Four levels of potential nerve compression were recognized: level #1,
from the radial nerve bifurcation to the proximal edge of the supinator muscle (arcade of Frohse),
including the area anterior to the radiocapitellar joint,
the recurrent radial vessels that fan out across the PIN at the level of the radial neck as the so-called “Leash of Henry” and the leading (medial proximal) edge of the extensor carpi radialis brevis; Level #2,
the proximal edge of the supinator muscle (arcade of Frohse); Level #3,
inside the supinator tunnel,
when the nerve descends obliquely between the superficial and deep bellies of the muscle; Level #4,
at the distal edge of the supinator muscle or beyond it.
The US diagnosis of PIN entrapment was based on nerve shape changes and focal thickening of one or more of its fascicles according to established criteria 7-8.
After ultrasound examination,
all patients underwent RM imaging and had surgical decompression.
Assessment
Both cadaveric and clinical studies were performed using a Philips IU22 ultrasound machine with a 17-5MHz broadband linear array transducer (Philips Healthcare,
Bothell,
WA).
The supinator tunnel evaluation required a specific scanning technnique with the forearm lying on the table in supination.
The probe was initially placed over the arcade of Frohse in a transverse plane.
It was then swept down moving from anterior to posterior while pronating the forearm to examine the full length of the tunnel until its distal edge while keeping the nerve fascicles in a stable position within the field of view.
Once the examination of the posterior interosseous nerve and its divisional branches beyond the supinator was completed,
the probe followed the inversed path sweeping it up from posterior to anterior while supinating the forearm to reach back to the arcade of Frohse.