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X-ray Evaluation of the True Neutral
Position of the Wrist: The Groove
for Extensor Carpi U Inaris as a
Landmark
Andrzej Jedlinski, MD, Malmo, Sweden, John M. G. Kauer, MD, PhD,
Nijmegen, The Netherlands, Kjell Jonsson, MD, PhD, Malmo, Sweden
Wrist problems have gained increased interest
among hand surgeons.1For accurate preoperative and
postoperative x-ray examinations, reproducible meth­
ods are required.2'5We report an x-ray observation that
demonstrates the true neutral position of the wrist.
90° of abduction. At each 10° elevation of the humerus
an x-ray film was taken over the caput ulnae, using a
vertical x-ray beam with film-focus distance of 100
cm. In this way, a series of projections of the whole
Materials and Methods
The sulcus of the extensor carpi ulnaris (ECU) ten­
don is located in the posterolateral aspect of the ulna in
the groove between the head of the ulna and the ulnar
styloid process.6This is well demonstrated in a crosssection through the cadaver wrist at the level of the dis­
tal radioulnar joint (Fig. 1). The ulnar styloid process of
the ulna is always posterior to the head of the ulna.
To evaluate imaging of the ECU groove with differ­
ent degrees of abduction in the shoulder, an anatomic
study of dry skeletal material was undertaken. Seven
humerus-ulnar bone complexes were used. The radius
was not included. The elbow was kept in 90° flexion
throughout the experiment. The humerus was elevated
from vertical toward horizontal position, imitating
abduction (0° to 90°) in the shoulder joint. The posi­
tion of the ulna was changed to the same degree as the
humerus was elevated; that is, from lateral wrist view
with maximal adduction to the frontal wrist view with
From the Department of Diagnostic Radiology, M alm o General
Hospital, M alm o , Sweden, and the Department of Anatomy and
Embryology, University of Nijmegen, Nijmegen, The Netherlands.
ECU
Received for publication Jan. 15, 1993 ; accepted in revised form
Nov. 2 9 , 1994 .
No benefits in any form have been received or will be received from a
commercial party related directly or indirectly to the subject of this article.
Reprint requests: Kjell Jonsson, M D , PhD, Department of Radiology,
University of Lund, University Hospital, S -221 85 Lund, Sweden.
Figure 1. Cross-section of the distal radius and ulna show­
ing the extensor carpi ulnaris (ECU) tendon in the postero­
lateral aspect of the ulna in the groove (straight black
arrows) between the ulnar styloid (S) and ulnar head (H).
The Journal of Hand Surgery
511
512
Jedlinski et al. / Neutral Position of the Wrist
Figure 2. X-ray films of the styloid process and ECU groove projected over each other and the head of the distal ulna,
showing their changing relationships as the arm is abducted from 0° to 90°. (A) and (B) show a case of a deep groove with
a “double line” seen between 40° and 60°.
cortex of the bottom of the ECU groove, seen as a
white line, and the outlines of the ulnar head and ulnar
styloid were registered (Fig. 2).
Results
At 0° elevation of the humerus (adduction) the ulnar
styloid is projected in the middle of the ulnar head. As
the elevation of the humerus is increased, the ulnar sty­
loid projects toward the lateral outline of the ulnar
head. At approximately 45° of humerus abduction, the
cortical outline of the concavity of the ECU groove
becomes visible as a discrete white line of cortical bone
projected over both the ulnar head and ulnar styloid. As
the angulation is additionally increased to 50°, 60°,
70°, and 80°, the projection of the cortical line of the
ECU groove “moves” anteriorly through the ulnar sty­
loid width toward the ulnar head (Fig. 2). At 90° eleva­
tion of the humerus, the cortical line is absent. In this
position the ulnar styloid can be demonstrated in the
true lateral, anatomic view.
Discussion
A number of studies have shown the importance of
standard projections in neutral position.1-3,7*8 Hulten9
introduced the term “ulnar variance” to refer to the
relative length of the ulna in relation to the radius.
Relative length differences between these two bones
have since been considered an important factor in the
pathogenesis of Kienbock’s disease and ulnar abut­
ment syndrome.1,7,9
In this study we have found that the projection of the
ECU groove can be used as a control to ensure that the
wrist has been x-rayed properly. The ECU line clearly
indicates the position of the ulna in the distal radioul­
nar joint during the wrist x-ray examination.
References
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Livingstone, 1993:973-1019.
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