Study Design: Cadaver dissection to study the anatomy of the scaleni muscle
s and surrounding structures.
Objectives: To analyze in depth the anatomy of the scaleni muscles and surr
ounding structures, and to further document anatomical variations which hav
e been reported in the literature.
Background: The literature reported variations in the attachments of the sc
aleni muscles, as well as the presence of a scalenus minimus muscle. The im
portance of these muscles in the respiratory and musculoskeletal systems le
d us to study these muscles with dissection.
Methods and Measures: We performed anatomical dissection on 10 cadavers. Th
e findings from the cadavers were analyzed and reported.
Results: The attachments of the 3 primary scaleni muscles (anterior, medius
, and posterior) were variable. The actual width of the scaleni muscles (an
terior, medius, and posterior) at the C6 tubercle and at the first rib also
varied. A scalenus minimus was present in one cadaver and presumably prese
nt in 2 others.
The scalenus anterior muscle arose in 20% of the specimens from C3 to C6, i
n 30% of the specimens from C3 to C7, in 20% of the specimens from C4 to C5
, and in 30% of the specimens from C4 to C6. The scalenus anterior muscle a
rose from C3 in 50% of the dissections. An attachment to C7 was observed in
30% of the cadavers. The widths of the scalenus anterior muscles at their
insertion were between 8 and 17 mm. The scalenus medius muscle arose in 40%
of the specimens from C2 to C6. In 60% of the cadavers, the scalenus mediu
s muscle had an attachment to C7. Fifty percent of the scalenus medius musc
les arose from C2 and 50% also had an origin from C1. The widths of the sca
lenus medius muscles at their insertion were between 10 and 20 mm with a me
an of 15.5 mm. Fifty percent of the scalenus posterior muscles arose from C
4 to C6 and 50% arose from C5 to C6.
Conclusions: Variations were found in the attachments and the size of the s
caleni muscles. These variations may effect the size of the scalene triangl
e, and thus, may potentially result in varied signs and symptoms in patient
s who have cervical, thoracic, and rib dysfunctions. Clinical implications
were postulated.