What are the steps for a pectoralis major musculocutaneous (muscle and skin) flap procedure?

Pectoralis Major Musculocutaneous Flap: Surgical Technique

The pectoralis major musculocutaneous (PMMC) flap should be elevated as a true island flap with maximal skeletonization of the pectoral branch of the thoracoacromial vessels, which serves as the vascular pedicle, allowing for optimal arc of rotation and reduced bulk while maintaining flap viability. 1, 2

Preoperative Planning

• Mark the skin paddle over the pectoralis major muscle, incorporating the nipple-areola complex when possible in male patients to stabilize blood circulation and reduce necrosis risk 3
• Position the patient supine with the ipsilateral arm abducted to expose the chest wall 1
• Design the skin island based on defect size, typically oriented along the axis of the muscle from the sternum toward the axilla 4

Surgical Steps

Flap Elevation

• Incise the skin paddle and dissect down to the pectoralis major muscle fascia 1
• Elevate the muscle from lateral to medial, dividing it from its humeral insertion while preserving the medial sternal attachments initially 2
• Identify and preserve the pectoral branch of the thoracoacromial artery and vein, which emerge from beneath the clavicle approximately 2-3 cm lateral to the sternoclavicular joint 1, 2

Pedicle Skeletonization

• Maximally skeletonize the vascular pedicle by carefully dissecting the pectoral branch free from surrounding muscle tissue, creating a true island flap 1, 2
• Divide the medial muscle attachments to the sternum and ribs, leaving only the neurovascular pedicle intact 2
• This technique increases pedicle length by 3-5 cm compared to traditional methods, improves arc of rotation, and reduces pedicle bulk 2

Flap Transfer

• Create a subcutaneous tunnel from the chest to the defect site, ensuring adequate width to prevent vascular compression 1
• For oral cavity/oropharyngeal defects, the flap can reach easily without tension due to the extended pedicle length 1, 4
• Rotate the flap through the tunnel, monitoring for any kinking or compression of the pedicle 1

Inset and Closure

• Inset the skin paddle to reconstruct the mucosal or cutaneous defect, ensuring the flap lies flat without tension 1
• Close the donor site primarily by advancing the remaining pectoralis muscle medially and approximating the skin edges 2
• Place drains at both the donor and recipient sites 1

Expected Outcomes and Timing

• Mean operative time for PMMC flap preparation is 76 ± 7 minutes, significantly shorter than free flap reconstruction at 145 ± 11 minutes 1
• Flap survival rate is 96-99.2% with proper technique 5, 6
• Total flap loss occurs in only 1-3.6% of cases in experienced hands 5

Clinical Context and Indications

Free flaps are preferred over PMMC flaps when microsurgical expertise and patient medical status permit, as they offer superior versatility and 92% success rates 5. However, PMMC flaps remain indicated for:

• Patients with compromised medical status unable to tolerate prolonged microsurgery 5
• Institutions lacking microsurgical capabilities 5
• Salvage procedures after free flap failure 5
• Coverage of exposed mandibular reconstruction plates 5
• Maxillectomy defects extending into the sinus when dental implantation is not required 7, 5

Critical Complications to Avoid

• Partial skin paddle necrosis occurs in approximately 2-6% of cases but can be managed conservatively 1, 6
• Fistula formation affects 20-47% of cases, though meticulous technique minimizes this risk 8, 6
• Facial asymmetry and malocclusion may result from bulky pedicle flaps, particularly for anterior defects 5
• Intraoral hair growth requires ongoing management in 5-10% of cases 5
• Pedicle compression during tunneling is the most common technical error leading to flap compromise—ensure adequate tunnel width 1