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Reconstruction of oral cavity defects using myogenous‐only scapular tip free‐flaps

Abstract Background Oral cavity reconstruction is very challenging anatomical subsite to reconstruct. Large defects often require free tissue reconstruction to provide the best chance of form and function. Additionally, free tissue reconstruction aids to prevent fistula formation. We aimed to determine outcomes of oral cavity defect reconstruction using scapular tip free flaps with a myogenous intraoral component. Methods All patients with a mandibular or maxillary bony defect that included a disruption of the intraoral mucosa component between 07/1/14 and 07/31/17. Patients were reconstructed with a scapular tip free flap, which included a muscular component that was used to recreate the oral mucosa. The primary study outcomes were flap success rates, development of orocutaneous or oronasal fistula, rate of resuming oral diet as well as the occurrence of medical and surgical complications in the first month following surgery. The tested hypothesis was formulated before data collection began. Results Twenty‐five patients were identified by the study criteria. There was one (4%) flap that failed, while orocutaneous fistula occurred in two patients (8%). Prior history of osteoradionecrosis was a statistically significant predictor of overall complication (p < .05). Conclusions Intraoral myogenous reconstruction allows for re‐mucosalization of the oral cavity defect and is associated with high viability and low‐complication rates. In patients with amenable oral mucosal defects, a myogenous scapular tip free flap is a suitable reconstructive option.

cutaneous, mucosal, and bony components closely associated with each other that poses many challenges to reconstructive surgeons.
The introduction of osteo-cutaneous free tissue transfer in combination with titanium reconstruction plates in the 1980's has been transformative; it allows for primary bony and mucosal reconstruction which re-establish facial contour and, even in select cases, provides adequate bone stock for dental implantation. The iliac crest flap was first introduced for this indication, but was quickly followed by the fibular and scapular free flaps. [1][2][3][4] A variety of possible flap designs exist based off of the subscapular vascular system. These allow for chimeric inclusion of scapular lateral border bone, scapular tip bone, scapular (horizontal) or parascapular (axial) or thoracodorsal artery perforator (TDAP) skin, a myogenous or myo-cutaneous element from the latissimus as well as serratus muscle. This great versatility has led to the continued popularization of this donor site for composite defects of the oral cavity. 5,6 The addition of myogenous elements has been touted for its ability to prevent salivary fistulas. 7 Additionally, designing the bony reconstruction based on the angular artery to the scapular tip has increased the available pedicle length. 8 The scapular bone has been also lauded for its natural contour which seems to easily replace angle and body mandibular defects as well as maxillary and palatal defects. 6 Free, regional, or local tissue transfer with cutaneous or mucosal elements remain the mainstay of oral cavity reconstruction. However, there is mounting support in the literature as to the utility of myogenous reconstruction for oral mucosal defects. [9][10][11][12][13][14] The use of myogenous only reconstruction can be considered for smaller intraoral mucosal defects where one subsite (alveolus) required reconstruction, or as a backup if an adequate perforator for TDAP was not found or if the subcutaneous tissue was deemed to be too thick. Myogenous pedicled flaps with the masseter and temporalis have been reported, as well as myogenous free tissue transfer with latissimus or vastus lateralis. [9][10][11][12] Seminal reports have recently begun to emerge also demonstrating good outcomes with myogenous closure or the oral mucosa in conjunction with osseous free tissue reconstruction of the mandible and maxilla. 5,13,14 Intriguingly, Gennaro et al. report comparable salivary fistula rates comparing cutaneous covered free tissue reconstructions of the maxilla and mandible to those covered by only a 5-20 mm cuff of surrounding muscle (sutured to the oral mucosa). 14 We herein report the largest case series to our knowledge using myogenous closure of oral cavity in mandibular and maxillary free tissue reconstruction using the scapular tip based off of the angular artery.
Patient factors, surgical technique, complications, and reconstructive outcomes are presented and discussed.

| Data source and study population
Approval from the University of North Carolina at Chapel Hill Biomedical Internal Review Board for human research was requested and granted for retrospective chart review of head and neck free tissue transfer at our institution. All patients provided documentation for medical photographs and the use of their nonidentifying photographs in publications. Chart review of all cases of free tissue transfer performed by the senior author at a single academic referral center over the study period, January 1, 2014-July 31, 2017, was performed.
Exclusion criteria for this study were donor sites other than the scapula tip based off the angular artery, resection not resulting in a combined osseous and mucosal defect requiring reconstruction, and resections outside of the oral cavity. Twenty-five cases were identified after exclusions were applied.

| Analysis
Patient demographics, patient comorbidities, smoking history, surgical descriptors, complications, tumor factors where applicable, the type of muscular elements included in the free tissue transfer and dimensions of the muscular elements. All data was manually extracted from the medical record.

| Patient outcomes
The demographic and patient factors from the cohort of 25 cases are summarized in Table 1. Indications for reconstruction were most commonly osteoradionecrosis and postablative defect after surgery for malignancy. Of the patients undergoing oncologic resection the great majority were advanced tumor stage (Table 1). Nineteen patients received reconstruction of the mandible and six received reconstruction of the maxilla. 24% of patients were smoking at the time of surgery and 52% had significant history of smoking in the past. The most common comorbid condition was diabetes mellitus (Table 1). Interestingly, one patient in our series had sickle cell trait, which was found after free flap failure on postoperative day 6.  Table 2. Osseous elements as long as 10.2 cm were harvested.
Osteotomies were used in five cases and were not associated with an increased number of complications. In 18 of 25 cases, a chimeric myogenous component (latissimus muscle only) was utilized in the oral closure ( Table 2). In seven (six maxilla, one mandible reconstruction) cases the oral closure was performed using the primarily the teres  The first is a female who underwent a right partial maxillectomy and tracheostomy for resection of a slowly growing palatal hemangioma. A 6 Â 3 cm maxillary defect remained ( Figure 1A). Her right scapular tip was harvested, as described above, and designed to incorporate a large cuff of teres major muscle for the intraoral aspect ( Figure 1B). The pedicle was re-anastomosed to the ipsilateral facial artery and vein. She ultimately had a 7-day hospitalization which included decannulation on POD 6 and resumption of a postoperative (oral) diet on POD 7 prior to discharge. At her 3-month follow-up visit intraoral swelling of the teres major was seen as well as full remucosalization of the muscle ( Figure 1C). The edema decreased and muscle continued to atrophy to a near-normal appearance, at her 1-year follow-up ( Figure 1D). The myogenous component used for all maxillary reconstruction was the teres major muscle.
The second case is a male who developed osteoradionecrosis of his mandible 2 years following chemoradiation of a Stage IVA base of tongue squamous cell carcinoma. He underwent a left segmental mandibulectomy from the mandibular body to right parasymphysis.
His left scapular tip was harvested to include teres major and subscapularis muscles and the thoracodorsal artery was incorporated to include a section latissimus muscle. An osteotomy was required for mandibular symphysis and body reconstruction, with care taken to leave periosteum intact on the inner aspect of the bone. 16 The plated bone flap can be seen in Figure 2A, the bone was then inset to native mandible with the latissimus muscle used for intraoral closure of the alveolus ( Figure 2B). Anastomosis was made to the ipsilateral facial artery and external jugular vein. During his 9-day hospitalization the patient received a laparoscopic gastrostomy tube on POD 8 and was decannulated POD 9 with discharge later that day. He underwent a swallow study on POD 16 and began slowly advancing an oral diet.
Unfortunately, he then presented in respiratory distress due to supraglottic lymphedema requiring replacement of the tracheostomy on POD 25. The patient was successfully decannulated 16 days later.
The rest of his postoperative course remained without further significant event. At his one-year follow-up CT shows bony union formation ( Figure 2C) complete intraoral remucosalization ( Figure 2D) and atrophy to be near-symmetric to his right alveolus ( Figure 2E). The patient had also returned to his preoperative left shoulder range of motion following harvest ( Figure 2F) as well oral diet with removal of his gastrostomy tube. All mandible reconstruction used latissimus muscle for closure of the intraoral defect, except one case where teres major was used.
As evidenced in the series, scapular tip bone can reconstruct complex maxillary and mandibular defects. 5,7 The The initial general concern surgeons may have is the ability to achieve watertight closure to prevent postoperative fistula. As suggested by Syme et al. we found that the implanted musculature initially swells and becomes edematous. 13 We believe this is instrumental in aiding in a watertight closure, by sealing potential areas for fistula formation. The edema slowly resolves and within a year the muscle atrophies and contracts, closely resembling the surrounding mucosa (Figures 1C and 2D). Postoperative fistula in our group had a low-occurrence rate of 8% (2 patients). One was a delayed postoperative fistula on POD 15 after the patient was cleared to resume an oral diet on POD 11. She required readmission for gastrostomy tube and the fistula spontaneously closed following a month of NPO status. The second fistula occurred in a patient who was status-post extensive mandibular repair after self-inflected gunshot wound. She had intraoral breakdown allowing salivary leakage into the neck. This was treated with aggressive operative debridement and primary closure as well as G-tube for prolonged enteral feeding.
The fistula had completely healed and closed by her 1 month postoperative visit. The low-fistula rate of 8% noted in this study is also comparable to rates experienced by other authors (12% of 33 muscle-only fibular and iliac crest flaps, 14 1 of 3, 13 1 of 17 18 and 0 of 15 7 osteomyogenous scapular flaps). In comparison to these studies our series remains the most comprehensive.
Furthermore, another concern can be contracture of the oral cavity using muscle-only flaps. We avoided the myogenous-only approach where the expected contracture would be deleterious.
When there is significant involvement (>50%) of oral cavity sites adja- Also inferred from the study was the low sequelae of donor site morbidity. Our protocol is to implement an out-of-bed and ambulation order on POD 1. As the average age of the patient cohort was 57 ± 13 years, early ambulation was important in order to limit the potential for pneumonia or postoperative thrombotic occurrences. All patients were out of bed to chair on POD 1, and 18 (72%) of patents ambulated by POD 3. Four patients that did not achieve ambulation by POD 3 were either noncompliant or limited by medical factors. Ambulation data was not clearly delineated on the remaining three patients.
Many patients had peripheral vascular disease and their advanced age made them poor candidates for fibular free flap. 19 Postoperatively all patients worked with physical and occupational therapy in order to return to preoperative shoulder range of motion levels as well as to decrease the changes of shoulder pain syndrome in the patients that

| CONCLUSION
The scapular tip flap with a chimeric muscle-only component is a reliable source for re-mucosalization of the oral cavity. The flap has a high-success rate, low rate of fistula formation, and is an excellent candidate in oral cavity reconstruction due to its robust vasculature and low-donor site morbidity. It is yet another option in the reconstructive surgeon's armamentarium and should be considered for intraoral mucosal defects involving either the maxilla or mandible.

FUNDING INFORMATION
No sponsor funding source.

CONFLICTS OF INTEREST
No conflicts of interest have existed in previous 24 months.