The Journal of the Arkansas Medical Society Med Journal Sept 2019 FInal 2 | Page 18

As the trunk of the main intercostal nerve passes
laterally around the thoracic wall, it divides into
three branches. The main branch is the anterior
cutaneous nerve, which runs inferior to the
specified rib in the subcostal groove. The anterior
cutaneous branch terminates after piercing
the intercostal and pectoralis major muscles
parasternally to supply the skin and sternum.
Figure 3: Dissection showing the anterior cutaneous branch of the intercostal nerve in the PIF
plane. Lateral spread of the injectate has stained the anterior cutaneous nerve a green color.
DISCUSSION
This is the first anatomical study of the PIFB.
There are two main findings of the study: first,
the PIFB injectate spread effectively involves the
anterior cutaneous branches of the intercostal
nerves; and secondly, the PIFB spread approached
the anterior border of the serratus anterior muscle
to involve the lateral branches of the intercostal
nerves as they emerge from the external intercostal
muscles (Fig. 3). The hemi-chests that received
the injections over the third and fifth ribs showed
a larger injectate spread compared to the single
injection at the fourth rib.
The layers of the thoracic chest wall from
superficial to deep include skin, subcutaneous
fat, pectoralis major muscle, anterior intercostal
membrane, external intercostal muscle, internal
intercostal muscle, and the innermost intercostal
muscle. The intercostal nerves lie in the intercostal
space deep to the internal intercostal muscle and
superficial to the innermost intercostal muscle.
The collateral branch of the intercostal
nerve runs in the inferior border of the intercostal
space at the superior edge of the rib below. The
collateral branch may rejoin the main nerve or end
independently as an additional anterior cutaneous
nerve. The last branch of the intercostal nerve is
the lateral cutaneous branch. It begins roughly
between the angle of the rib and the mid-axillary
line and terminates after piercing the intercostal
muscles and lateral thoracic wall obliquely to
innervate the overlying skin. 9, 10 It is important to
note that utilization of the PIFB will require diffusion
of local anesthetic across an anterior, intercostal
membrane and the external intercostal muscle
before reaching the intercostal nerves.
> Continued on page 68.
If You, Or A Patient,
Need Legal Assistance
Call Us For a
Free Consultation
• Personal Injury
• Tractor Trailer Crashes
• Social Security
• Bankruptcy
• Nursing Home Negligence
• Family Law
• Contract Disputes
T HE B RAD H ENDRICKS
L AW F IRM
800-603-5100
Little Rock • Conway • Fayetteville • Texarkana • Jonesboro • Fort Smith
66 • THE JOURNAL OF THE ARKANSAS MEDICAL SOCIETY
VOLUME 116