Full Length Article
Posterior interosseous artery pedicle
flap: an anatomical study of the
relationship between the posterior
interosseous nerve and artery
Journal of Hand Surgery
(European Volume)
0(0) 1–4
! The Author(s) 2018
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DOI: 10.1177/1753193418797525
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Angus Keogh1, David James Graham2 and Bryan Tan2
Abstract
The anatomical relationships of the posterior interosseous artery and nerve are not well described. To characterize these relationships, ten cadaveric forearms were dissected and the relationships between the
posterior interosseous nerve, its branches, and the posterior interosseous artery documented. The dissection
of the posterior interosseous artery flap can be conceptualized in three zones with decreasing risk to the nerve
as the dissection proceeds from proximal to distal. Provided fine motor branches of the posterior interosseous
nerve are protected during the dissection of the nerve and artery, this flap can be harvested with safety.
Keywords
Posterior interosseous artery, posterior interosseous nerve, anatomy, soft tissue surgery, surgical flaps
Date received: 8th March 2018; revised: 12th June 2018; accepted: 7th August 2018
Introduction
The method of raising the posterior interosseous
artery (PIA) flap was originally published independently by two groups (Penteado et al., 1986; Zancolli
and Angrigiani, 1988). Its versatility and the ability to
avoid sacrificing a major vessel of the forearm has
helped popularize this flap. It can be used for skin
coverage of the elbow and hand, either in an antegrade or as a reverse pedicled flap fashion (Brunelli
et al., 2001; Hubmer et al., 2004). It has been used as
a vascularized interposition for the treatment of
radioulnar synostosis with good results (Jones
et al., 2007; Sonderegger et al., 2012). Its use however has been associated with complications, such
as venous congestion, flap failure, and injury to the
posterior interosseous nerve (PIN) (Acharya et al.,
2012; Brunelli et al., 2001; Elgafy et al., 2000; Puri
et al., 2007).
There is little information about anatomical relationship between the PIA and the PIN, although there
are articles reporting on the anatomy of the nerve
and the artery independently (Ay et al., 2005;
Zancolli and Angrigiani, 1988).
The aim of this study was to report in detail on the
relationship of the PIA and PIN in the forearm,
particularly as they relate to the preparation of the
PIA flap.
Methods
Ethics consent was obtained for the ten skeletally
mature cadaveric forearms used for our dissections.
All specimens were fresh frozen and prepared with a
gelatine arterial infusion technique according to the
protocol of Jansen et al. (2011).
Dissections were performed by a single surgeon
using loupe magnification from proximal to distal as
would be done when raising the PIA flap. The PIA and
PIN were dissected from the supinator tunnel to the
distal radioulnar joint.
With the elbow flexed to 90 and forearm pronated, a line was drawn between the lateral epicondyle of the elbow and the ulnar head. A skin incision
1
Western Orthopaedic Clinic and St John of God Hospital, Subiaco,
Western Australia
2
Sir Charles Gairdner Hospital, Perth, WA, Australia
Corresponding Author:
David James Graham, Sir Charles Gairdner Hospital, Perth, WA,
Australia.
Email: Ortho_reg@yahoo.com
2
was made exposing the forearm fascia. The fascial
septum dividing extensor digiti minimi (EDM) and
extensor carpi ulnaris (ECU) was identified. A
5 mm section of fascia superficially covering both
muscles was taken with the septum, and the
septum was freed from the adjacent muscles with
gentle blunt dissection. In the proximal part of the
dissection, nerves and arteries passing from deep to
the septum and penetrating the under surface of the
EDM and ECU muscle bellies were freed from areolar attachments (Figure 1). This revealed a complex
interweaving of fine nerves and vessels supplying
the undersurface of the EDM and ECU and the
Figure 1. Right arm dissection. The elbow is on the left
and wrist on the right. The distal edge of supinator is
shaded. Nerves and vessels can be seen coursing from the
under surface of the inter muscular septum (labelled ^) to
penetrate the EDM and ECU muscles (marked with pins).
The PIN (labelled *) exits toward the right of the picture in
close association with the septum.
EDM: extensor digiti minimi; ECU: extensor carpi ulnaris.
Journal of Hand Surgery (Eur) 0(0)
surrounding tissues. The PIA and PIN were then
easily identifiable at the base of the septum. Just
distal to these, small nerves and vessels branched
to the ECU and EDM (Figure 2). The artery and
nerve were followed both proximally and distally
and gently dissected from each other and from fascial coverings.
Throughout the course of the dissections, measurements were taken with reference to the lateral
epicondyle using a surgical ruler. Digital photographs
were taken.
Results
We found a consistent relationship between the PIA
and PIN, enabling us to define three zones of dissection; the proximal (at-risk zone), the middle (intermediate risk zone), and the distal (low risk zone) (Figure 2).
The PIN emerges from the distal edge of supinator
at 73 mm (range 60–76 mm) from the lateral epicondyle. At this point multiple nerve branches arise and
supply the abductor pollicis longus deep to the fascia
underlying EDM, the ECU, and the extensor digitorum
communis.
In the proximal aspect of the dissection, nerves
and vessels emanating from underneath the
septum and coursing radial and ulnarward supply
the EDM and ECU muscles respectively (Figure 3).
In this region, which we refer to as the proximal
region or at-risk zone, there is a close intertwining
of small vessels and nerves such that they resemble
Medusa’s head. Individual nerves and arteries must
be gently freed from their areolar attachments. The
PIN continues deep to this web of intertwined vessels
and nerves.
The proximal at-risk zone spans on average
25 mm (range of 15–55 mm). The range of distances
Figure 2. Right arm dissection showing zones in forearm. Nerves and vessels emerge from underneath the septum on
the left of the image. The PIA (red line) and PIN (yellow line) diverge at the proximal muscle belly of EPL.
Keogh et al.
3
Figure 3. Right forearm proximal dissection. The Medusa’s head of intertwined nerves (yellow line) and arteries (red line)
supplying the ECU and extensor digitorum communis muscles can be seen arising from underneath the intermuscular
septum.
can be explained by variability in the number of
branches of the PIN and the point at which they
diverge from the PIN. Specimen variability meant
that between one and three branches of the nerve
could supply either the ECU or EDM muscles. The
distance from the lateral epicondyle at which they
diverged from the PIN also varied.
Immediately distal to this region is the middle or
intermediate risk zone. It spans on average 40 mm
(20–56 mm) at a distance of 98 mm (61–103 mm) from
the lateral epicondyle. In this region, the deep fascia on
the radial side of the septum surrounding the EDM can
be gently separated to reveal the PIN and PIA
(Figure 2). In this zone the average maximal separation
of the PIN from the PIA was 4.3 mm. The septum with
the perforators arising from the PIA can be drawn
to the ulnar side of the dissection, separating the flap
with the PIA pedicle from the nerve (Figure 2). In this
way, the nerve and artery can be freed from one
another to the level of the distal, safe zone.
The distal or low risk zone spans 100 mm
(79–119 mm) at a distance of 132 mm (116–147 mm)
from the lateral epicondyle. This area is marked by a
wide separation of the nerve and the artery. The
artery bifurcates at the proximal aspect of the safe
zone. The PIA proper continues in the base of the
septum, while the bifurcating branch courses
around the proximal edge of the extensor pollicis
longus (EPL) muscle belly to supply the EPL and
abductor pollicis longus, and it eventually and variably connects with the dorsal branch of the anterior
interosseous artery (Figure 2). The PIN continues
from this bifurcation point, not with the PIA and the
septum, but with the bifurcating arterial branch.
There are several branches of the nerve at this
point, including branches to the extensor indicis
proprius and the extensor pollicis longus. The distribution of these branches is variable although they are
separate from the PIA and the septum.
Discussion
Zancolli and Angrigiani (1988) divided the PIA into
three parts, describing its path and branches but
not its relationship to the PIN and its branches.
Hubmer et al. dissected the PIA in 66 cadaveric specimens and determined that it was only present in
the proximal forearm, with a dorsal branch of the
anterior interosseous artery forming a vascular
arcade that anastomosed with the PIA in the middle
of the forearm (a choke anastomosis) (Hubmer et al.,
2004). Xarchas et al. (2004) performed an anatomical
study of the PIA flap in eight cadavers but did not
describe the relationship of the PIA and PIN. Elgafy
et al. (2000) described in detail the branches of the
PIN from their work dissecting cadavers but not its
relationship to the PIA and its branches. We hoped to
make clear with this study the relationship between
PIN and PIA in the forearm.
We have identified a reproducible pattern of branching and transit of the nerve and artery through the
forearm. The PIA can be divided into three zones relating to the degree of risk for damage to the PIN and its
branches when dissecting the artery. Knowledge of
this interrelationship is clinically important because
injury to the PIN is described in relation to the use of
PIA flaps (Brunelli et al., 2001; Elgafy et al., 2000). In
our experience, transient weakness of the extensors of
the little finger and ECU can occur.
PIA flaps that are pedicled at the level of the wrist
in a retrograde fashion and which do not require as
much proximal dissection have a relatively low risk of
4
injury to the PIN. Flaps that are raised with a proximal pedicle in an antegrade fashion create an
increased risk of injury to the nerve because of the
close intertwining of the small vessels and the nerve
in the proximal dissection.
For PIA flaps to cover the hand, the PIA flap is
pedicled distally based on the communicating
branch between the PIA and the anterior interosseous artery. Xarchas et al. (2004) provides an apt
description for raising this flap. There is mention in
that study of the relationship between the PIA and the
PIN but the specifics are lacking. As the flap is being
raised from distal to proximal, the surgeon should be
aware of the point of bifurcation of the PIA. This is the
point at which the PIA and PIN come to lie in closest
proximity (middle zone). Proximal to this, the nerve
can be gently dissected from the PIA keeping the PIN
to the radial side of the septum. For coverage of the
hand, the PIA is typically ligated in the middle zone. If
more length is required, the small branches to the
ECU and EDM must be protected when ligating the
PIA within the proximal zone (Figure 2).
When performing the flap in an antegrade fashion
(for elbow coverage), the pedicle is based in the
proximal zone. It is possible to dissect further proximally, however, the artery must be freed from
small nerves and vessels in the at-risk zone.
Obtaining additional length for the flap is difficult,
and in our practice we tend to rotate the flap within
the distal half of the proximal zone. As per the
description of Xarchas et al. (2004), the dissection
starts by raising the fascia covering the EDM and
ECU and identifying the intermuscular septum. The
PIA is identified distally near the ulnar head, and the
communicating branch with the anterior interosseous
artery is ligated. Working proximally, the PIA and the
intermuscular septum are freed from deeper attachments and at the point of bifurcation of the PIA (the
junction between the intermediate and low risk
zones) the PIN joins the PIA. The dissection from
here proximally must ensure the safety of the PIN,
as branches to the EPL emerge distal to this point.
The PIN can be gently freed in a radial direction from
the PIA and the septum while dissecting the septum
proximally. At the distal extent of the high-risk zone,
one encounters fine branches to EDM and ECU
(Figure 3). These must be gently dissected from the
soft tissues associated with the PIA and vessels. The
flap can then be rotated for elbow coverage or
interposition.
As with all cadaveric studies there are flaws in this
study. The measurements of zones are not absolute
position values and therefore should not be interpreted as such. Values can be used as relative measures of structures between different individuals.
Journal of Hand Surgery (Eur) 0(0)
Another weakness of the study is the relatively
small number of specimens tested. This is a
common issue with cadaveric studies owing to
costs and ability to procure specimens.
We sought to clarify the relationship of the PIA to
the PIN in order to promote awareness of the possible problems arising when using this flap. We hope
this study will ensure greater safety and reduce the
incidence of nerve injury related to its use.
Acknowledgements CTEC,
University
of
Western
Australia.
Declaration of conflicting interests The authors
declared no potential conflicts of interest with respect to
the research, authorship, and/or publication of this article.
Funding The authors received no financial support for the
research, authorship, and/or publication of this article.
Ethical approval We obtained ethics consent from St
John of God Hospital Subiaco (reference no. 896) and the
University of Western Australia.
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