To The Editor: I read with interest the article entitled "Is
There a Safe Area for the Axillary Nerve in the Deltoid Muscle? A Cadaveric
Study" (2006;88:2395-9), by Cetik et al., and I would like to offer some
comments.
There is general agreement that the distance of the axillary nerve in
relation to certain acromial sites is variable. The authors of this study
tried to determine a safe area in which it would be possible to avoid injuring
the axillary nerve during deltoid muscle-splitting. According to their
findings, the surgeon can determine a so-called safe area during surgery by
measuring the arm length. In my opinion, this is not accurate.
The axillary nerve extends more anteriorly from the anterior acromial edge
and more posteriorly from the posterior acromial edge before it enters into
the muscle belly. The so-called safe area includes only the portion of the
nerve parallel to the lateral acromial border. Measurement of arm length
during surgery does not allow accurate application of a linear regression
equation for the determination of the safe zone for the nerve.
We performed a study1 on this topic and found that, in about 25%
of sixty-seven fresh cadavers (134 deltoid specimens), the axillary nerve's
vertical distance from the upper border of the deltoid muscle was <4 cm in
both shoulders, with the minimal distance being 2 cm. Also, we found that the
nerve is located a mean 2.6 cm (range, 1.7 to 3.7 cm) above the midpoint of
the vertical plane (length) of the deltoid. Our findings were in agreement
with those in a previous publication2. Also, Burkhead et
al.3 studied the axillary nerve in fifty-one embalmed and five
fresh cadaveric specimens and found that, in nearly one-fifth of the cadavers,
the nerve was <5 cm from the palpable edge of the acromion and at a minimal
distance of 3.1 cm.
With this information in mind, I am concerned about the relatively larger
distances of the nerve, from the anterior and posterior edges of the acromion,
reported by Cetik et al. I do not know if differences in the material
(embalmed rather than fresh cadavers, population characteristics, etc.)
explain these differences.
Regarding the posterior deltoid-splitting approach recommended by Wirth et
al.4, our laboratory studies showed that it was safe only when the
splitting was strictly between the posterior and middle parts of the deltoid.
We must keep in mind that the axillary nerve, after passing the quadrilateral
space and giving off its branch to the teres minor, divides into a posterior
branch (runs to the posterior part of the deltoid) and an anterior branch
(runs to the middle and anterior parts of the deltoid).
In summary, I think that in clinical practice we must be very careful when
performing a deltoid-splitting procedure. It is certainly possible to cause
iatrogenic nerve damage even with a deltoid-splitting of 4 cm from the
acromial edge. The axillary nerve is always located at a level inferior to the
subacromial bursa and above the vertical to the middle of the deltoid length.
The suggested arm-length determination of the safe area should be used as
complementary information only.