Derrick T. Lin
INTRODUCTION
The floor of the mouth (FOM) is an anatomic subsite of the oral cavity defined anteriorly by the inferior alveolar ridge, extending posteriorly to the ventral surface of the tongue medially and the anterior tonsil pillar laterally. This area overlies the paired sublingual glands, which are situated on the mylohyoid and hyoglossus muscles.
A split-thickness skin graft (STSG) by definition is a graft that incorporates only a portion of the dermis, in contrast to a full-thickness skin graft (FTSG) that includes the entire dermis. STSG may range anywhere from 0.012 to 0.030 inch in depth. STSG is usually preferred over FTSG for FOM defects since they require less ideal conditions for survival.
Defects of the FOM requiring reconstruction are usually the result of resection of a cancer. Cancer of the oral cavity accounts for 2% to 6% of all cancers in the United States and 30% of all cancers of the head and neck. The goals of reconstruction of this area include preservation of the mobility of the tongue and establishment of a sulcus between the mandible and tongue. The use of an STSG is one of several reconstructive options for small, superficial defects in the FOM.
HISTORY
A general history should be performed prior to considering reconstructive surgery. Patients with medical comorbidities such as high-risk heart disease, chronic obstructive lung disease, or other significant systemic illness should be carefully evaluated before surgery to determine if they can tolerate general anesthesia. Additionally, a history of infection, poor healing, or keloid scarring should be considered. A history of radiation therapy of the oral cavity should be sought.
PHYSICAL EXAMINATION
The physical examination should be focused on the size and depth of the cancer and resultant extent of the defect of the oral cavity. Larger defects involving the FOM and the tongue may be managed with a radial forearm free flap to prevent contractures and tethering of the tongue. Donor site must be inspected to rule out infection, previous trauma or surgical scars.
INDICATIONS
STSGs for the defect in the FOM are generally reserved for defects resulting from the resection of small, superficial cancers (T1, T2). Either the periosteum of the mandible must be intact or healthy cancellous bone present in the setting of a marginal mandibulectomy. The integrity of the musculature of the FOM cannot have been violated, and the overall size of the defect should be no more than 4 cm in diameter.
CONTRAINDICATIONS
Free tissue reconstruction or a rotational pedicled flap should be considered in defects larger than 4 cm to prevent significant contracture and tethering of the tongue. STSG should not be considered for defects in which the musculature of the FOM is no longer intact or when a segmental mandibulectomy is necessary.
Previous irradiation or recurrence after prior surgical resection would be considered relative contraindications to the use of an STSG for the defect in the FOM, especially if a marginal mandibulectomy is to be included in the ablative plan.
PREOPERATIVE PLANNING
STSGs donor sites are usually chosen based on areas that are easily concealed such as the upper anterior or lateral thigh. These sites should be free of infections, other skin lesions or previous surgery, radiation or trauma. Preparation of the recipient wound bed is critical for the survival of the STSG. In general, STSG will survive on muscle, fascia, cancellous bone, periosteum, perichondrium, or granulation tissue. The wound needs to be free of necrotic tissue and infection, and hemostasis must be complete.
Postoperative endoscopy and examination of the cancer under general anesthesia is important in determining the extent and resectability of the cancer. Second primary cancers must be ruled out.
SURGICAL TECHNIQUE
The STSG is usually taken from the upper thigh. The donor site is inspected to ensure that there is no infection, lesions, eschar, or granulation tissue. The area is prepped and draped in the usual sterile fashion.
Gauze soaked with 1:100,000 epinephrine is placed on the proposed donor site. Mineral oil is then placed over the site in preparation for the dermatome. The dermatome is set at a depth of 0.0185 inch (range of 0.012 to 0.030 inch). A no. 15 blade may be used to simulate the thickness by placing the beveled edge in the dermatome. Using a tongue blade on the thigh to maintain constant pressure, the dermatome is then applied at a 30- to 45-degree angle and activated (Fig. 2.1). When the appropriate size is achieved, the dermatome is tilted away from the skin and the base of the graft is separated from the donor site using either a scalpel or scissors (Fig. 2.2).
FIGURE 2.1 Using a tongue blade on the thigh to maintain constant pressure, the dermatome is then applied at a 30- to 45-degree angle and activated.
FIGURE 2.2 When the appropriate size of the skin graft is achieved, the dermatome is tilted away from the skin and the base of the graft is separated from the donor site using either a scalpel or scissors.
Before suturing the graft into the FOM defect, the graft is “pie-crusted” to allow for egress of any possible fluid accumulation. This is achieved by making small longitudinal incisions with a no. 15 blade. A nasogastric tube is inserted prior to suturing the graft into the defect.
The graft is sutured into the defect using 3-0 Vicryl sutures. A Xeroform gauze bolster is placed over the graft and sutured into place. 2-0 silk sutures are tied over the bolster to immobilize the graft. If there is significant edema of the FOM or retropulsion of the tongue, a tracheostomy should be considered.
Donor-site hemostasis is achieved by placing 1:100,000 epinephrine–soaked gauze. Once hemostasis is achieved, a Tegaderm is placed.
POSTOPERATIVE MANAGEMENT
Postoperatively, the patient receives his or her nutrition through a nasogastric tube. The bolster is left in place for 7 days. Revascularization of the graft usually begins after 2 to 3 days with full circulation achieved by 6 to 7 days.
After the bolster is removed, the patient may begin an oral diet. Oral hygiene with Peridex rinse is begun at this time. If there is any wound breakdown, continual NPO with nasogastric tube feeding is recommended. Primary contracture of 10% to 20% is expected in the use of an STSG.
COMPLICATIONS
In patients who are carefully selected, postoperative complications are rare. Hematoma under the skin graft needs to be watched for since an unrecognized hematoma would compromise the integrity of the graft. The development of excessive edema of the area should also be carefully monitored. This could lead to airway compromise necessitating a temporary tracheostomy. A keloid may develop in the donor site in those patients predisposed with a history of keloid formation.
RESULTS
The use of an STSG for the reconstruction of the oral cavity is safe, simple, and reliable. However, careful patient selection is essential. Patients with a large defect, resection of the musculature of the FOM, segmental mandibulectomy, and previous radiation therapy should be excluded.
In my experience, the risk of hematoma is small and a tracheostomy is rarely needed. The expected take rate is about 80% to 100% initially with complete healing in about 4 weeks. Contraction of approximately 10% to 20% of the wound is expected and should be taken into account when assessing the use of STSG. The majority of patients begin an oral diet 7 days after surgery when the bolster is removed. In well-selected patients, long-term cosmesis and function should be excellent (Figs. 2.3 and 2.4).
FIGURE 2.3 Long-term results demonstrate a well-healed skin graft and a natural contour to the FOM.
FIGURE 2.4 The donor site defect is acceptable.
PEARLS
• Rigorous evaluation of the defect and donor site preoperatively is essential for successful reconstruction.
• Use a dermatome depth of 0.012 to 0.030 inch.
• Expect 10% to 20% contraction of the skin graft.
• Keep the bolster in place for 1 week to allow for vascularization of the STSG.
• Inspect for donor site lesions.
PITFALLS
• Contraindicated in large defects or defects with resection of FOM musculature
• Contraindicated in previously radiated patients who will have a marginal mandibulectomy
• Contraindicated in exposed mandibular bone without periosteum or cancellous bed
INSTRUMENTS TO HAVE AVAILABLE
• Dermatome
• Standard head and neck surgical instruments
SUGGESTED READING
Branham GH, Thomas JR. Skin grafts. Otolaryngol Clin North Am 1990;23(5):889–897.
Feldman DL. Which dressing for split-thickness skin graft donor sites? Ann Plast Surg 1991;27(3):288–291.
Petruzelli GJ, Johnson JT. Skin grafts. Otolaryngol Clin North Am 1994;27(1):25–37.
Tran LE, Berry GJ, Fee WE Jr. Split-thickness skin graft attachment to bone lacking periosteum. Arch Otolaryngol Head Neck Surg 2005;131(2):124–128.
Hartig GK. Free flaps in oral cavity reconstruction: when you need them and when you don’t. Int J Radiat Oncol Biol Phys 2007;69:S19–S21.
de Bree R, Rinaldo A, Genden E, et al. Modern reconstruction for oral and pharyngeal defects after tumor resection. Eur Arch Otorhinolayngol 2008;265:1–9.