HRUS represents the first level imaging in the palmar aponeurosis evaluation.
So we will provide a dedicated HR-US images of palmar aponeurosis at different levels, compared with a detailed anatomic scheme,
and a practical guide on “how we do” a HR-US scan.
The patient must be sitting in front of the examiner,
with the upper limb lying on the table and the the palm of the hand facing up (Fig.1).
Fig. 2: Position of the hand to evaluate the palmar aponeurosis.
Place the probe with an axial scan on the proximal wrist,
proximal to carpal tunnel, to evaluate the palmaris longus tendon (Fig.2-3).
Fig. 3: Probe position to evaluate palmaris longus (PL) tendon on axial plane, proximal to carpal tunnel, correlated with anatomical scheme of PL and palmar aponeurosis (A). TML, transverse metacarpal ligament; TCL, transverse carpal ligament; dashed triangle, central bundle; *, slip for the fingers.
Fig. 4: Axial scan of palmaris longus tendon (arrowheads), proximal to carpal tunnel.
Turn by 90° the transducer to examine PL tendon on longitudinal plane.
(Fig 4-5).
Fig. 5: Probe position to evaluate palmaris longus (PL) tendon with longitudinal scan proximal to carpal tunnel correlated with anatomical scheme of PL and palmar aponeurosis (A). TML, transverse metacarpal ligament; TCL, transverse carpal ligament; dashed triangle, central bundle; *, slip for the fingers.
Fig. 6: Longitudinal scan of palmaris longus tendon (PL), proximal to carpal tunnel; fl, flexor tendon.
Then,
the probe must be moved distally, at the level of the carpal tunnel,
to evaluate the PL tendon on axial scan.
Remember that the probe must be tilted correctly to obtain the right insonation.
At this level the PL tendon present the maximum thickening (Fig.
6-7).
Fig. 7: Probe position to evaluate palmaris longus (PL) tendon on axial plane at level of carpal tunnel, correlated with anatomical scheme of PL and palmar aponeurosis.
Fig. 8: Axial scan of palmaris longus tendon (arrowheads), at the level of the carpal tunnel.
Turn the probe to evaluate at this level the PL tendon on longitudinal plane.
Note the median nerve inside the carpal tunnel (Fig.8-9).
Fig. 9: Probe position to evaluate palmaris longus (PL) tendon with longitudinal scan at level of carpal tunnel, correlated with anatomical scheme of PL and palmar aponeurosis (A). TML, transverse metacarpal ligament; TCL, transverse carpal ligament; dashed triangle, central bundle; *, slip for the fingers.
Fig. 10: Longitudinal scan of palmaris longus tendon (PL), at the level of the carpal tunnel. Note the ralationship with median nerve (*). fl, flexor tendons.
Place the probe with an axial scan to evaluate the relationship of PL tendon with transverse carpal ligament (Fig.10-11).
Fig. 11: Probe position to evaluate the relationship of palmaris longus (PL) tendon with transverse carpal ligament, correlated with anatomical scheme of PL and palmar aponeurosis (A). TML, transverse metacarpal ligament; TCL, transverse carpal ligament; dashed triangle, central bundle; *, slip for the fingers.
Fig. 12: Axial scan of palmaris longus tendon (arrowheads), at the level of the carpal tunnel. *, median nerve; TL, transverse carpal ligament.
Turn the transducer by 90° and shift it distally to evaluate PL tendon witch continues in palmar aponeurosis (Fig.12-13).
Fig. 13: Probe position to evaluate palmaris longus (PL) tendon which continues in palmar aponeurosis (A), correlated with anatomical scheme of PL and palmar aponeurosis (A). TML, transverse metacarpal ligament; TCL, transverse carpal ligament; dashed triangle, central bundle; *, slip for the fingers.
Fig. 14: Longitudinal scan of palmaris longus tendon (PL) when it continues in the palmar aponeurosis (A).
Examine the central bundle of palmaris aponeurosis in the middle of the palm (Fig.14-15).
Fig. 15: Probe position to evaluate the central bundle of palmaris aponeurosis correlated with anatomical scheme of palmaris longus (PL) and palmar aponeurosis (A).TML, transverse metacarpal ligament; TCL, transverse carpal ligament; dashed triangle, central bundle; *, slip for the fingers.
Fig. 16: Axial scan of the central bundle of palmar aponeurosis (arrowheads) at middle of the palm.; fl, flexor tendons.
Use Color Doppler to evaluate the vassels of the superficial palmer arch (Fig.16).
Fig. 17: Axial scan of the central bundle of palmar aponeurosis (arrowheads) at middle of the palm.; fl, flexor tendons. Doppler sign on the vassels of the superficial palmer arch.
Following the central bundle until it divides into four slips,
one for each finger.
Evaluate the finger slips on axial and longitudinal plane (Fig 17-18-19-20-21).
Fig. 18: Probe position to evaluate with axial scan the finger slips of central bundle of aponeurosis correlated with anatomical scheme of palmaris longus (PL) and palmar aponeurosis (A).TML, transverse metacarpal ligament; TCL, transverse carpal ligament; dashed triangle, central bundle; *, slip for the fingers.
Fig. 19: Axial scan of the finger slip of palmar aponeurosis (arrowheads) for the IV finger¸a, artery of the superficial palmer arch.
Fig. 20: Probe position to evaluate with longitudinal scan the finger slips of central bundle of palmaris aponeurosis correlated with anatomical scheme of palmaris longus (PL) and palmar aponeurosis (A). TML, transverse metacarpal ligament; TCL, transverse carpal ligament; dashed triangle, central bundle; *, slip for the fingers.
Fig. 21: Longitudinal scan of the finger slip of palmar aponeurosis (arrowheads) for the III finger¸flIII, flexor tendon of III finger.
Fig. 22: Longitudinal scan of the finger slip of palmar aponeurosis (arrowheads) for the III finger¸flIII, flexor tendon of III finger.