Diagnostic ultrasound ( PDFDrive )

866 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
A
B
FIG. 23.19 Carpal Tunnel Entrapment of the Median Nerve. (A) Short-axis cross-sectional area of the median nerve obtained at the level
of the pronator quadratus (PQ) at the distal forearm. (B) Cross-sectional area obtained in the carpal tunnel at the level of the pisiform (P). The
4-mm 2 difference in area between the two images is consistent with carpal tunnel syndrome.
A
B
FIG. 23.20 Ulnar Nerve Dislocation at the Elbow. (A) At rest, with the elbow extended and the probe positioned between the medial epicondyle
(M) and the ulnar olecranon (O), the ulnar nerve (circled) is positioned posterior to the epicondyle. Note the ulnar nerve is enlarged at this location.
(B) On lexion the ulnar nerve (circled) dislocates anterior to the medial epicondyle along with the medial head (MT) of the triceps muscle (known
as “snapping triceps” syndrome). Most patients with ulnar dislocation do not exhibit medial head triceps dislocation. See also Video 23.4.
during elbow lexion, and this subluxation can be captured on
dynamic imaging (Video 23.4). Scan technique is important in
this diagnosis. he probe should be positioned in a transverse
plane with respect to the medial posterior elbow. he nerve should
normally be visible within the cubital tunnel with the elbow in
an extended position. he osseous landmark of the medial
epicondyle should be maintained in the visualized ield as the
patient slowly lexes the elbow. Excessive probe pressure should
be avoided because this can limit dynamic motion of the nerve.
he nerve should normally remain lateral to the medial epicondyle.
Subluxation, where the nerve moves medially and anteriorly
along the epicondyle, or dislocation, where the nerve snaps
anteromedial to the medial epicondyle, may occur on lexion 52,53
(Fig. 23.20). Patients with ulnar nerve subluxation or dislocation
may experience pain or transient numbness, but this dynamic
instability can also be seen in asymptomatic in healthy controls,
and the association with neuropathy is debated. 54,55
JOINT ASSESSMENT
Ultrasound can play a helpful role in the diagnosis and follow-up
of both inlammatory and noninlammatory arthropathy and
may guide diagnostic and therapeutic procedures in patients
with these disorders. Patients with inlammatory arthropathy
such as rheumatoid arthritis present with joint pain, swelling,
and stifness. Ultrasound plays a complementary role to clinical
history, physical examination, radiographs, and serology tests
such as acute phase reactants (e.g., C-reactive protein, erythrocyte
sedimentation rate, rheumatoid factor, and antinuclear antibody).
In this role, when used systematically, ultrasound can substantially
increase diagnostic certainty in patients with suspected inlammatory
arthropathy. 56 Ultrasound also represents a great tool in
the follow-up of these patients, allowing detection of subclinical
relapse in patients with clinical remission and predicting relapse
and joint deterioration. 57