ORIGINAL ARTICLE Year : 2022  |  Volume : 30  |  Issue : 3  |  Page : 59-62

Free gracilis muscle flap: Variations of obturator nerve

Yavuz Tuluy1, Zulfukar Ulas Bali2, Merve Ozkaya Unsal3, Aziz Parspanci4, Levent Yoleri4, Yavuz Kececi4
1 Department of Plastic, Reconstructive and Aesthetic Surgery, Turgutlu State Hospital, Manisa, Turkey
2 Private Practitioner in Plastic, Reconstructive and Aesthetic Surgery, İstanbul, Turkey
3 Department of Plastic, Reconstructive and Aesthetic Surgery, Kent Hospital, İzmir, Turkey
4 Department of Plastic, Reconstructive and Aesthetic Surgery, Manisa Celal Bayar University, Manisa, Turkey

Date of Submission15-Dec-2021Date of Acceptance28-Feb-2022Date of Web Publication24-Jun-2022

Correspondence Address:
Dr. Yavuz Tuluy
Manisa Turgutlu State Hospital, Turgutlu, Manisa 45000
Turkey

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/tjps.tjps_67_21

Background: Gracilis muscle has been used in reconstructive surgery for free muscle flap transfer. It was reported to be a reliable flap with lower rates of donor-site morbidity. In this study, we aimed to emphasize the anatomical variations of the obturator nerve. Materials and Methods: Clinical results of 14 patients who underwent lower lip reconstruction and facial reanimation with free gracilis muscle transfer between March 2017 and May 2021 were examined. Results: We identified eight male and six female patients, with a mean age of 55.6 years (range: 37–73 years). Of 14 patients, nine (64.3%) were operated on for lower lip reconstruction, and the remaining five cases underwent facial reanimation. Despite adequate dissection, we could not find the branch of the obturator nerve for gracilis muscle in two cases (14.3%), while vascular pedicles are detected in all cases. The first case was a lower lip reconstruction and the second case was a facial reanimation. Conclusion: While gracilis muscle is a good option for functional muscle transfer, it may be difficult to find the branch of the obturator nerve. Our study may suggest the need for consideration of anatomical variations of the obturator nerve before surgical planning for improved shared decision-making.

Keywords: Facial reanimation, free gracilis muscle flap, lip reconstruction, obturator nerve

How to cite this article:
Tuluy Y, Bali ZU, Unsal MO, Parspanci A, Yoleri L, Kececi Y. Free gracilis muscle flap: Variations of obturator nerve. Turk J Plast Surg 2022;30:59-62
  Introduction 

Gracilis muscle flap has been extensively used in reconstructive surgery practice and can be used as both local and free flap. Breast reconstruction, facial reanimation, perineal reconstruction, lower and upper extremity reconstruction, and lip reconstruction are the most common procedures for gracilis muscle.[1] Harii et al. reported the first use of gracilis muscle for head-and-neck reconstruction.[2] Afterward, it was started to be used widely in plastic surgery. Notwithstanding its potential anatomical variations, the gracilis muscle has many advantages compared to the other muscle flaps. It has a long vascular pedicle and a single motor nerve.[3] Located superficially on the medial thigh and easy to harvest, gracilis muscle has lower donor-site morbidity and overall reliable anatomy.[4] It can be harvested entirely or segmentally. It is a Type-2 muscle whose pedicle length is about 7–10 cm and sufficient for anastomosis for different anatomical areas as a free flap.[5] Gracilis muscle is innervated by the obturator nerve and can be used as a free functional muscle flap. In our clinic, gracilis muscle is used as a free flap in the reconstruction of facial paralysis and total lip reconstruction. In this study, we aimed to emphasize the anatomical variations of the obturator nerve observed during reconstructive surgery.

  Materials and Methods 

In this retrospective study, we included the cases who underwent surgery for facial reanimation and lower lip reconstruction using a gracilis muscle flap between March 2017 and May 2021 in Manisa Celal Bayar University Hospital and İstanbul Kartal Dr. Lütfi Kırdar Training and Research Hospital. Data on patients' sex, age, and past medical history were collected. In addition, intraoperative findings such as any variation of the obturator nerve and postoperative clinical outcomes, including duration of follow-up and surgical aftermath, were recorded.

Surgical technique

During the procedures, a two-team approach was performed. Gracilis is a Type-2 muscle, and nutrient vessels come from the deep femoral artery, medial circumflex femoral artery, and superficial femoral artery.[2] The main vascular pedicle is located at the proximal third of the muscle. It is innervated by the obturator nerve, which stems from the lumbar plexus and emerges from the obturator foramen.[6] It divides into two branches under the pectineus muscle. Anterior branch enters the gracilis from the proximal and middle third junction.[7]

The patient is positioned on the operating table in the supine position while the thigh is flexed and abducted. Adductor longus muscle is palpated, and just posterior of it, the skin incision is made about 10 cm distal to the pubic tubercle. The muscle is isolated in the distal part not to damage the pedicle. After the dissection of the neurovascular pedicle about 5 cm long, if more muscle length is needed, another 5 cm incision is made distally to dissect the pretibial attachment of the tendon. In all cases, facial artery and vein were prepared as recipient's vessels. Cross-facial nerve graft was coapted to the obturator nerve for facial reanimation, and the branch of the marginal mandibular nerve was coapted to the obturator nerve for lip reconstruction. In all lip reconstruction cases, skin grafts were used to cover the muscle.

  Results 

We identified eight male and six female patients, with a mean age of 55.6 years (range: 37–73 years). Of 14 patients, nine (64.3%) were operated on for lower lip reconstruction, and the remaining five cases underwent facial reanimation. While the etiology of the latter included trauma and intracranial tumor surgery, all patients who underwent lower lip reconstruction had underlying squamous cell carcinoma. All the patients were hospitalized for approximately 1 week, and the mean follow-up period was 18 months (range: 5–44 months).

We could not find the branch of the obturator nerve for gracilis muscle in two cases (14.3%) [Figure 1] and [Figure 2], while vascular pedicles are detected in all cases [Figure 3]. The first case was a lower lip reconstruction and the second case was a facial reanimation. Neither of the patients had a history of previous thigh surgery that would damage the anatomical structures. The first patient was a 67-year-old male who had a history of smoking for 35 years. Incisional biopsy of the ulcerated lesion on the lower lip was reported as squamous cell skin cancer. Bilateral modified radical neck dissection was planned due to the presence of metastatic lymph nodes in the bilateral neck on magnetic resonance imaging. The second patient was a 55-year-old female, active in daily life and had no comorbidities. The patient's facial paralysis occurred after trauma. In the first case, nerve coaptation was not performed. In the second case, the contralateral gracilis flap was dissected and the obturator nerve was found without any difficulty. Total flap loss occurred in one patient undergoing total lower lip reconstruction, who reported nonadherence to postoperative advice. The patient was operated on again using local flaps. Another patient was grafted due to skin graft loss. No complications were observed in patients who underwent facial reanimation, and muscle contractions started on average in the postoperative 3rd month.

Figure 1: Perioperative image of the gracilis muscle flap harvest on the left side. No obturator nerve was found

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Figure 3: Perioperative image of the gracilis muscle flap harvest. Obturator nerve is seen clearly (black arrow: obturator nerve, white arrow: vascular pedicle)

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  Discussion 

The obturator nerve originates from the lumbar plexus (L2–L4), descends through the psoas muscle, and passes the obturator foramen. The nerve runs close to the lateral wall of the obturator canal, and it is located lateral to the obturator artery and vein.[8],[9] Then, it divides into two branches. Anagnostopoulou et al. reported in their cadaver study that the division point was in the obturator canal in 51.78% of the specimens, while the rest were either in the medial thigh (25%) or intrapelvic (23.22%).[10] In another anatomical study, they reported that in the vast majority of cadavers, the obturator nerve division was inside the obturator canal.[6] Its anterior branch continues between the adductor longus and brevis, and the posterior branch continues between the adductor magnus and brevis muscles. The anterior branch divides into 2–4 branches, innervating gracilis, adductor longus, adductor brevis, and pectineus muscles. The posterior branch divides into 1–4 branches and innervates adductor magnus, adductor longus, external obturator, and adductor brevis muscles. The anterior branch also provides sensory innervation of the medial thigh and knee joint. After the obturator nerve enters the gracilis muscle, it divides into 2–3 branches.[5] This provides partial use of the muscle by dissection according to the course of the nerve. It is understood that the obturator nerve has high anatomic variability, its intraneural topography changing from patient to patient.[11] Due to this variation, the muscle can be innervated by anterior or posterior branches of the nerve. Furthermore, the presence of accessory obturator nerve was reported in the literature, innervating the pectineus muscle.[12] The cadaver study by Rodríguez Lorenzo et al. reported that the nerve entered the muscle perpendicularly to the dominant vascular pedicle in all cadavers.[13] In another anatomical study on cadavers, the gracilis muscle was innervated by the branch of the anterior division of the obturator nerve in all cases.[14] In our study, although the gracilis muscle flap was adequately dissected superiorly and inferiorly under loupe magnification by experienced surgeons in microsurgery, the obturator nerve was not observed in two cases. These patients did not undergo any previous surgery that would cause anatomical changes in the medial thigh. The obturator nerve enters the gracilis muscle from its deep surface about 7–8 cm distance from the origin of the muscle.[15] For this reason, it was not thought that there would be injury due to dissection during the exposure of the gracilis muscle. There may be several explanations for the fact that the branch of the obturator nerve, which is thick compared to many neural structures and whose localization has been clearly defined in many studies, cannot be found by experienced microsurgeons. First, the nerve branch may enter from a localization very close to the origin of the muscle, and this may make it difficult to expose. Second, a very thin branch may be entering the muscle from an unexpected location, increasing the risk of nerve damage during dissection. If nerve anastomosis is required, the contralateral gracilis muscle flap should be elevated. In the literature, there are many articles about vascular pedicle of gracilis, but studies on obturator nerve are scarce. Studies are generally focused on the sensory branch of the obturator nerve that receives the sensation of the knee joint. Especially for facial reanimation surgery, obturator nerve anatomic variations should be considered. The variation can change the course of the surgical procedure. Gracilis muscle is known for its reliable anatomy, but further studies are needed for obturator nerve anatomy.

  Conclusion 

While the gracilis muscle is a good option for functional muscle transfer, it may be difficult to find the branch of the obturator nerve. Our study may suggest the need for consideration of anatomical variations of the obturator nerve before surgical planning for improved shared decision-making. Due to the limited anatomical data on the obturator nerve, more anatomical studies are needed for understanding the course of the nerve.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 

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  [Figure 1], [Figure 2], [Figure 3]