Improving Skin Paddle Reliability and Muscle Gliding in Free Functional Gracilis Transfers

Summary:

Free functional muscle transfer is an attractive option within reconstructive surgery when seeking to restore critical muscle function. The gracilis muscle has long been utilized for this purpose due to its expendability and consistent anatomy. Historically, survival of the skin overlying the distal one-third of the myocutaneous gracilis flap has been unpredictable. To address this, the myofasciocutaneous technique was developed, with prior studies demonstrating improved distal skin paddle viability with this approach; however, the mechanism is poorly defined. This study aimed to understand what factors contribute to survival benefit in myofasciocutaneous gracilis flaps. Using cadaveric dissections followed by latex dye injections, we discuss the creation of a deep fascial sheath that contains a rich vascular network and permits adhesion-free excursion at the recipient site. This study advances our understanding of the myofasciocutaneous gracilis flap and provides wider clinical applicability in free functional muscle transfer.

Takeaways

Question: What factors contribute to distal skin paddle survival in the myofasciocutaneous gracilis flap?

Findings: Cadaveric dissections followed by latex dye injections revealed a highly vascularized 360-degree fascial sheath around the myofasciocutaneous gracilis flap.

Meaning: Preserving the deep fascia of adjacent structures during myofasciocutaneous gracilis flap harvest improves distal skin paddle reliability and permits adhesion-free excursion at the recipient site.

INTRODUCTION

Free functional gracilis transfer is a valuable technique in reconstructive surgery due to muscle expendability, adequate excursion, low donor site morbidity, and consistent anatomy.^1,2 However, a key limitation of the myocutaneous technique is the unpredictable survival of skin overlying the distal one-third of the flap.^1,2 Prior literature has discussed improvements in distal skin paddle survival using the myofasciocutaneous technique, by which the deep fascia of adjacent muscles is harvested with the gracilis and skin paddle.^1–4 However, the mechanism by which this phenomenon occurs is not fully understood, and was the impetus for this study.^1,2,4 Here, we discuss key steps for harvesting the myofasciocutaneous gracilis flap, and provide a mechanistic explanation related to distal skin paddle viability and adhesion-free excursion at the recipient site.

TECHNIQUE

Flap Harvest

To visualize the anatomy of the myofasciocutaneous gracilis flap, five fresh-frozen cadaver legs were dissected. On each donor limb, a myofasciocutaneous gracilis flap was raised using the following steps:

Preparation

1. Mark the adductor longus muscle, which is the palpable cord in the medial thigh.

2. Mark the gracilis muscle’s axis, two finger breadths posterior to the adductor longus muscle, extending to the pes anserinus.

3. Mark the appropriately sized elliptical flap centered over the muscle axis.

Creation of the Deep Fascial Sheath

1. Extend the proximal incision through fat to the muscular fascia.

2. Identify the septal junction between the gracilis and adductor longus muscles.

3. Enter the space by retracting the adductor longus anteriorly to locate the pedicle.

4. Anteriorly, harvest fascia from the adductor longus, adductor magnus, and sartorius muscles ensuring fascial continuity around the gracilis.

5. Posteriorly, harvest fascia from the semimembranosus and adductor magnus muscles, ensuring fascial continuity around the gracilis.

6. Perform further dissection of the fascia from these adjacent muscles, if necessary. The actual gracilis muscle should not be seen, except in the most proximal or distal portions.

Pedicle Dissection

1. While retracting the adductor longus anteriorly, dissect the pedicle and the nerve off the adductor brevis, taking a portion of the adductor brevis fascia with it as needed.

2. Trace the vascular pedicle and nerve back proximally, depending on the desired length of pedicle needed.

Muscle Detachment

1. Free the muscle from all nonfascial soft tissue attachments, leaving only the pedicle.

2. Transect the proximal tendon to detach it from the ischiopubic ramus.

3. Transect the distal tendon at or near the insertion, based on required length.

4. Transect the nerve based on desired length for functional transplant.

Latex Dye Injection

After dissection of each flap, pink latex dye was injected into the cadaveric myofasciocutaneous gracilis flap via the medial circumflex femoral artery using an 18-gauge angiocatheter and 10-mL syringe. Latex dye injection permitted visualization of the small vessels within the fascia (Fig. 1). Many of these vessels branched from the medial circumflex femoral artery (main vascular pedicle), coursed around the muscle and through the fascia, and supplied the overlying skin paddle. Additionally, the deep fascia of adjacent muscles surrounding the gracilis formed a 360-degree sheath (Fig. 2), which permitted the muscle to glide with minimal resistance. [See Video (online), which displays how deep fascia is harvested from adjacent muscular structures and fully ensheathes the gracilis muscle. The fascial sheath enhances muscle gliding in myofasciocutaneous gracilis flaps.]

Fig. 1.

Lifted deep fascial sheath of myofasciocutaneous gracilis with latex-injected branching vascular network within the fascia (yellow arrows). Printed with permission from and copyrights retained by Shaun D. Mendenhall, MD.

Fig. 2.

Deep fascia of gracilis and surrounding muscles (adductor longus, adductor magnus, sartorius, and semimembranosus) creates a sheath (white arrow) around the myofasciocutaneous gracilis. Printed with permission from and copyrights retained by Shaun D. Mendenhall, MD.

Video 1. displays deep fascia is harvested from adjacent muscular structures and fully ensheathes the gracilis muscle. The fascial sheath enhances muscle gliding in myofasciocutaneous gracilis flaps.

Download video file ^{(85.1MB, mp4)}

DISCUSSION

The gracilis flap is a perennial option in reconstructive surgery due to consistent anatomy and clinical versatility.^1–9 Since the late 1970s, gracilis-based reconstructions have evolved to encompass a spectrum of advanced clinical solutions.^2,5,8 Despite these benefits, concerns about perfusion, particularly in the distal one-third of the skin paddle in myocutaneous gracilis flaps, have persisted.^1–3,7,10 This dialog resulted in Stevanovic et al introducing the myofasciocutaneous technique as a solution to skin paddle necrosis in the distal one-third.² Our findings provide a better understanding of the mechanism behind improved distal skin paddle survival, thus building upon previous work on this technique.

Myofasciocutaneous techniques were developed to improve skin paddle survival by harvesting the muscle, vascular pedicle and nerve, adjacent deep fascia, and overlying skin, and authors endorse this method for gracilis FFMT.^4,7–9 Our study confirms that there is a rich vascular network within the deep fascia that when preserved, enhances blood flow to the overlying skin paddle. In our experience, this has led to more clinical versatility including the ability to harvest a larger skin paddle if needed. Of the myofasciocutaneous FFMTs performed at our practice, only one of 22 (4.5%) had partial skin paddle necrosis that required skin grafting. Additionally, there were no reports of significant peri-incisional anesthesia or dysesthesia in our patient cohort. Furthermore, there is the added benefit of the 360-degree fascial sheath that surrounds the gracilis. This deep fascial sheath is analogous to a tendon sheath, thus permitting improved muscle excursion while countering adhesion formation at the recipient site [see Video 1 (online)].

This study has several limitations. First, there are no objective metrics to support the mechanism described herein other than direct visualization of the blood vessels coursing through the fascia. Secondly, conducting a prospective study that compares the two techniques (ie, myocutaneous versus myofasciocutaneous) would not be feasible due to relatively low case numbers, and in our opinion, would not be ethically permissible because of the benefits that we observed clinically with the myofasciocutaneous method. Furthermore, this approach is favorable for clinical scenarios that necessitate a sizable skin paddle, but is not necessary for reconstructions that do not require a skin paddle or high excursion demands, such as in facial reanimation. Lastly, endpoints related to long-term flap survival and function must be evaluated to inform the risks, benefits, and limitations of this approach.

In summary, we have provided a mechanistic explanation for the improved survival of the distal one-third of the skin paddle in myofasciocutaneous free functional gracilis transfers. We believe that the vascularized deep fascia ensheathing the muscle prevents fibrous adhesions, improves muscle excursion, and enhances skin paddle perfusion, thus contributing to the favorable outcomes at our institution.

DISCLOSURES

Shaun D. Mendenhall is an educational consultant for PolyNovo, which does not relate to the content of this article. All the other authors have no financial interest in relation to the content of this article. This study was funded by a research grant from the Edwin & Fannie Gray Hall Center for Human Appearance.

ETHICAL APPROVAL

This study was approved by the institutional review board of the Children’s Hospital of Philadelphia.