Anatomic Analysis of Surgical Approaches to the Deep Volar Forearm
Daniel N. Ronel, MD, Estomih Mtui, MD, William B. Nolan III, MD
Forearm compartment syndrome is a surgical emergency that requires release of the superficial muscle compartments. In
some clinical situations it is imperative to also explore the deep muscle compartments, such as in cases of high-voltage
electrical injury, severe crush injuries, extended extrinsic pressure (such as an unconscious patient lying on their own
forearm), and when there is ongoing sepsis or suspicion of necrotic muscle despite previous fasciotomy.1-4 In some cases,
even after compartment fasciotomy, the epimysium of individual muscles must be incised to relieve persistently elevated
tissue pressure.5 This can only be achieved with adequate visualization of the deep space. If epimysiotomies of the deep
muscles are not performed in these situations, necrosis and contracture may result.
There are no anatomical guides for surgical exploration of the deep compartments that would minimize collateral damage to
surrounding vessels, nerves, and muscles. Anatomical textbooks do not delineate the dominant vascular pedicles within the
deep space in enough detail to plan a safe surgical approach. Surgical injury in the setting of ischemia, especially vascular
injury, compounds the tissue damage that has already occurred. Three standard approaches to the deep forearm have been
described, either in the context of fractures or of nerve compression. These ulnar, central, and radial approaches do not
attempt to minimize iatrogenic trauma to small arteries, because they are not described in the setting of forearm ischemia. In
the Henry approach to the anterior radius, for example, the recurrent radial vessels are ligated.
Incisions described for the treatment of compartment syndrome often criss-cross the forearm or gently sweep across it in
various directions (Figure 1). Incisions that cross the forearm will transect more of the venous and lymphatic return than will
a straight incision, and the resolution of forearm edema could be impaired. Such incisions may also prevent the future design
of a radial forearm flap, as the vascular supply and outflow of the skin pedicle would be compromised.
Figure 1. Forearm incisions.
Modified from Gelberman, et al
(with permission).
Method: We evaluated four surgical approaches to the deep forearm by performing detailed anatomical dissections on
embalmed and plastinated cadavers. In the radial approach the skin incision was made radial to the midline of the volar
forearm, starting at the proximal wrist crease and extending to the antecubital fossa. The superficial fascia was released and
the dissection continued radial to the FCR and between the FCR and the FDS. In the central approach the skin incision was
made over the center of the volar forearm. The superficial fascia was released and the deep dissection continued either radial
or ulnar to the palmaris longus and then between tendons of the FDS. In the ulnar approach the skin incision was made radial
to the FCU at the wrist and extended to the medial epicondyle of the humerus. The superficial fascia was released and the
dissection continued radial to the FCU, between the FCU and the FDS.
We used a scoring system to rate the approaches for their ability to visualize the deep space without causing iatrogenic injury
to superficial muscles, arteries, and nerves (Table 1). Each element was scored on a scale of 1 – 3, with 1 being the best (the
least damage was caused by the surgical approach) and 3 being the worst (the most damage was caused by the surgical
approach). In the category of muscle injury, the surgical approach scored a “1” if there was no muscle injury, a “2” if sharp
dissection of muscle was required to access the deep space, and a “3” if the division of a superficial muscle was required. For
arterial injury, the surgical approach scored a “1” if no arterial branches were divided, a “2” if less than 50% of the segmental
branches to any muscle were divided, and a “3” if more than 50% of the segmental branches to any muscle or if a dominant
pedicle was divided. For nerve injury the surgical approach scored a “1” if no dissection around a motor nerve was required,
a “2” if dissection around a motor nerve was required, and a “3” if division of a motor nerve was required.
Table 1: Surgical approach scoring system
Muscle injury score
Criterion
1
No muscle injury
2
Sharp dissection required
3
Division of superficial muscle required
Arterial injury score
Criterion
1
No arterial branches divided
2
Less than 50% of segmental branches to any muscle divided
3
More than 50% of segmental branches or a dominant pedicle to any muscle divided
Nerve injury score
Criterion
1
No dissection around a motor nerve required
2
Dissection around a motor nerve required
3
Division of motor nerve required
Results: Each surgical approach easily allowed the release of the superficial volar compartment. In the radial approach, the
FDS impeded access to the deeper forearm in all the specimens. Division of the origin of FDS III was necessary to evaluate
the FPL and FDP muscles (Figure 2, left). Segmental branches from the radial artery to the FCR impeded deep dissection in
all the specimens (Figure 2, right). There was no significant injury to motor nerves.
Figure 2. Radial approach. Left: access to the deep space requires division of the FDS. Right: branches from the radial artery
to the FCR impede deep exploration.
In the central approach it was difficult to separate the proximal fibrous raphe of the palmaris longus from the FCR or the
FCU. Sharp dissection of the raphe or division of the FDS was required to reach the FPL and FDP. The division of several
arterial branches from the ulnar artery to the FDS was required in 70% of the specimens (Figure 3, left). Dissection through
and around the FDS was adjacent to motor nerve branches from the median nerve in 60% of the specimens (Figure 3, right).
Figure 3. Central approach. Left: there is no plane in the proximal FDS, it is difficult to separate the FCR or FCU from the
palmaris, and ulnar artery branches to the FDS impede deep access. Right: sharp dissection around median nerve branches to
the FDS is required.
In the ulnar approach, the PQ was reached between the ulnar artery and the FDS. One or two distal segmental arterial
branches to the FDS and/or the FCR required division in 50% of the specimens (Figure 4, left). As the dissection moved
proximally, the remainder of the deep compartment could easily be seen if the ulnar neurovascular bundle was raised with the
FDS (Figure 4, right). This approach spared all proximal segmental branches to the FCR and FDS. In two specimens, one
segmental branch to the distal FCU was divided. No dissection of superficial muscles or motor branches was required with
the ulnar approach.
Figure 4. Ulnar approach. Left: access to the PQ only requires division of one or two branches from the ulnar artery to the
FDS. The scissors are under the fascia of the PQ, which is easily divided. Right: the deep compartment is easily seen in the
interval between the FDS and FCU.
The radial approach scored an average of 6.1 (SD 0.32); the central approach scored an average of 5.8 (SD 0.63), and the
ulnar approach scored an average of 4.0 (SD 1.05). Using the Mann-Whitney test for non-parametric data (U statistic =
5.8656), the ulnar approach caused significantly less surgical trauma than the radial approach (p < 0.001, z = 4.0701) and the
central approach (p < 0.003, z = 3.4349).
Table 2: Comparison of surgical approaches
Approach
Average score* SD
Radial
6.10
0.32
Central
5.80
0.63
Ulnar
4.00
0.05
*Lowest possible score (safest approach) = 3
Highest possible score (least safe approach) = 9
Conclusion: In the volar forearm, an ulnar approach to the deep space is simple, causes the least surgical injury, and provides
access to the deep structures. The skin incision is similar to that described by Matsen, which extends from the medial
epicondyle to the flexor crease of the wrist.2 The superficial compartment along the radial side of the FCU is opened distally,
which reveals the ulnar neurovascular bundle. The muscle is retracted ulnarly, and the plane of dissection between the FCU
and the FDS can be appreciated. The PQ can be seen distally between the ulnar neurovascular bundle and the FDS: one or
two branches from the ulnar artery to the FDS may need to be ligated in order to release the PQ. Moving proximally, the
ulnar neurovascular bundle is raised with the FDS to preserve its branches to that muscle. Although a branch from the ulnar
artery to the FCU may need to be ligated, the FCU receives most of its blood supply via a dominant pedicle from the
posterior ulnar recurrent artery. Raising the FDS in the middle third of the forearm allows easy access to the remaining
muscles of the deep volar compartment, the FPL and the FDP. Exposure of the three deep muscles allows their evaluation
for ischemia and, if needed, individual epimysiotomy. This approach to the deep space requires no sharp dissection.
References
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