Pedicled Latissimus Dorsi Myocutaneous Flap Transthoracic Transposition for Repairing Neck and Shoulder Soft Tissue Defect Combined with Infection

Background: To explore the clinical application and selection of latissimus dorsi myocutaneous ap in repairing neck and shoulder soft tissue defect combined with infection. Methods: From July 2017 to December 2019, 11 patients with neck and shoulder soft tissue defect combined with infection in our hospital were repaired by the pedicled latissimus dorsi myocutaneous ap (PLDMF) according to the shape and size of the soft tissue defects, including 9 males and 2 females, with an average age of 40.2±12.6 years. The average defect area after debridement of infected and necrotic tissue was (7.0±1.3) cm × (4.8±1.2) cm, and the average area of the aps was (34.4±3.8) cm × (6.0±1.0) cm. The donor site was sutured directly. Results: Seven cases of skin aps healed by the rst intention, while 4 cases developed infections at the distal ends of the skin aps after surgery, which all survived after anti-infection treatment and repeated dressing changes for infection control, and the donor and recipient sites of the aps healed well. Followed up for an average of 17.3±3.8 months with good ap blood supply and limb function, there was no recurrence of infection. Conclusions: PLDMF


Background
Latissimus dorsi myocutaneous ap has been widely used in the repair of adjacent soft tissue defects due to the advantages of large ap area and carrying muscles 1,2 . However, with the development of microsurgery technology, the dorsal thoracic artery perforator ap without latissimus dorsi has achieved better soft tissue repair effects due to its thinner cut and less damaged to the donor site 3,4 . In contrast, although the traditional latissimus dorsi myocutaneous ap in the repair of soft tissue defects caused more trauma and inferior aesthetic, it still has a relatively reliable repair effect in repairing wounds with soft tissue infections, such as when it is necessary to expand the debridement of infection and necrotic tissue 5,6 . The purpose of this study is to further clarify the clinical application value of this ap by analyzing the latissimus dorsi musculocutaneous ap to repair infectious soft tissue defects in the shoulder and neck. This study reported 11 patients with large neck and shoulder soft tissue defects combined with infection. After extensive debridement, the latissimus dorsi myocutaneous ap was applied to cover the soft tissue defect to observe the repair effect of this ap in similar injuries.

Methods
A total of 11 patients with neck and shoulder soft tissue defect combined with infection who were admitted to the Department of Microsurgical Repair at the Orthopedic Center of the First A liated Hospital of Xinjiang Medical University from July 2017 to December 2019 were included in this study, including 9 males and 2 females, with an average age of 40.2±12.6 years. The causes of injuries were tra c accident injury in 8 cases, heavy object crush injury in 2 cases, and shoulder tumor resection in 1 case. After debridement of infected and necrotic tissue, the average defect area was (7.0±1.3) cm × (4.8±1.2) cm. According to the shape and size of the soft tissue defect, PLDMF was used to repair the soft tissue defect, and the average area of the ap was (34.4±3.8)cm × (6.0±1.0)cm. The donor site was sutured directly.
The inclusion criterion was the soft tissue defects of neck and shoulder caused by local debridement or tumor resection, which could not be sutured directly. The exclusion criteria were as follows: a. Patients with serious underlying diseases, such as severe heart failure, renal failure, severe hypertension, and diabetes, who could not tolerate long-term surgery; b. Patients with severe infection on the wound surface of the recipient site, without performing thorough debridement and good control of infection; c. Patients with severe extremities vascular sclerosis, which can lead to ap vascular crisis, and thereby seriously affecting the postoperative effect.

Surgical technique
Under general anesthesia, the patient took a left lateral decubitus position with the right upper limb exed on the front chest. Before ap design, ultrasound Doppler was used to explore the perforator branches of the dorsal thoracic artery at the intersection of 6-8cm below the axillary apex and the dorsal thoracic artery. When designing the ap, point A was marked at the apex of the posterior axillary wall, point B was marked at the right posterior superior iliac spine, and the line between point A and point B was the axis of the latissimus dorsi myocutaneous ap. According to the marked points, lines, and planes, the designed size of skin aps were 38cm × 6cm and 40cm × 8cm, respectively.
With the aid of a head-mounted magnifying glass, cut open the frontal edge skin, subcutaneous tissue, and fascia of the designed ap to fully expose the leading edge of the latissimus dorsi , along which the latissimus dorsi was freed and lifted up. Then cut open the posterior edge skin, subcutaneous tissue and fascia of the designed ap, the latissimus dorsi myocutaneous ap was cut off from the distal end of the designed ap, the free latissimus dorsi myocutaneous ap was dissected from the distal end to the proximal end, and then carefully stop bleeding in the wound (Figure 1). At 6-8cm in the axilla, thoracodorsal arteries and veins, and thoracodorsal nerves were seen into the designed myocutaneous ap. Free the myocutaneous ap to the axilla as the rotation point, where the fascia was loosened and the possible compression caused by the rotation of the myocutaneous ap was relieved, the myocutaneous ap was then protected after being wrapped with wet gauze. Full-thickness suture was performed in the donor site of the myocutaneous ap, a rubber tissue was used for drainage, and a sterile dressing was applied.
The patient's position was changed from side lying to supine, with the back of the affected side hand abducted. Firstly, the surface in ammatory granulation, inactivated and necrotic tissue were removed along the wound edge of neck, shoulder and back, and the branches of cephalic vein and external jugular vein were explored and ligated. Then the wound was rinsed repeatedly with hydrogen peroxide and normal saline to provide a good recipient site for the skin ap. Meanwhile, carefully observe the blood supply of the latissimus dorsi myocutaneous ap, cut open the skin and subcutaneous tissue of the axilla and chest, the ap was transferred to cover the wound through the open channel. Then the latissimus dorsi muscle tissue and the soft tissue inside the wound surface were sutured and xed, thereafter the skin around the ap was sutured. There should be no local tension after the ap was sutured and covered, and the wound surface should be well covered. Rubber tissue was placed around the ap for drainage.

Results
Seven cases of skin aps healed by the rst intention, while 4 cases developed infections at the distal ends of the skin aps after surgery, which all survived after anti-infection treatment and repeated dressing changes for infection control, and the donor and recipient sites of the aps healed well. All patients were followed up for an average of 17.3±3.8 months with good ap blood supply and limb function, and there was no recurrence of infection.

Typical case
A 22-year-old male patient suffered an open fracture of the right clavicle combined with skin and soft tissue defects from a car accident. Debridement treatment was given at the rst intention, and then skin ap transplantation was performed after the wound infection was controlled and the granulation tissue was well formed. In the second stage, after the removal of excess in ammatory granulation, infection, and necrosis tissue of the wound, the area of the soft tissue defect was measured to be 8cm × 6cm, and the fractured end of clavicle and subclavian vascular pulsation could be seen in the wound. The PLDMF was designed based on the soft tissue defect, and clavicle fracture reduction and internal xation were performed at the same time. After 8 months of follow-up, the aps healed well without recurrence of infection, and the fracture was well xed (Figure 2-3).

Discussion
The latissimus dorsi myocutaneous ap is one of the largest skin aps that can be cut in the human body, and can be designed to cut various types of skin aps, muscle aps, myocutaneous aps, lobed myocutaneous aps and composite myocutaneous aps accoring to the characteristics of soft tissue defects 7 . In 1976, Baudet et al. reported the successful case of free latissimus dorsi ap for the rst time, making the application of this ap in wound surface repair gradually widespread 3 . Large-area soft tissue defects caused by severe neck and shoulder trauma or tumor resection often have large volume defects, especially in the case of exposed joint, the application of simple free skin ap to cover soft tissue defects is often di cult to meet the requirements for joint function protection and wound healing 8, 9 . In contrast, the latissimus dorsi myocutaneous ap can not only meet the needs of soft tissue lling in the neck and shoulders, which has a good protective effect on the shoulder joint, but also the ap is close to the neck and shoulders, and can be cut with a pedicle to cover soft tissue defects, making the blood supply of the skin ap possible and the survival rate high 10 . Two patients in this study suffered blood vessels, nerves and bones exposure with severe soft tissue infection. The use of a pedicled skin ap with latissimus dorsi to cover the soft tissue defect after debridement combined with internal xation of clavicle fracture, exhibited good anti-infection ability 11 . Compared with free skin ap, this skin ap can provide higher antiinfection ability and ap blood supply to prevent the occurrence of skin ap necrosis, recurrence of infection and exposure of steel plate, etc. Moreover, vascular anastomosis under the microscope is not required for this skin ap, and the requirements for the surgeon's personal ability and local medical conditions are relatively low 12 . In this study, 1 case of clavicle fracture used atissimus dorsi myocutaneous ap to cover after xation with internal xation plate. Follow-up observation after surgery showed that both the skin ap and the fracture achieved good repair effect.
However, there are still some limitations for PLDMF in repairing soft tissue injury of neck and shoulder.
The main blood supply artery of the atissimus dorsi myocutaneous ap comes from the dorsal thoracic artery (the subscapular artery originates about 3.0cm below the axillary artery), and the dorsal thoracic artery usually gives off the medial and lateral branches. Based on the anatomical characteristics of the latissimus dorsi ap, the length of the vascular pedicle of this ap from which the dorsal thoracic artery and its medial and lateral branches can be freed is about 5.0-8.0 cm, thus there is a certain range limit for pedicled transfer 13,14 . Furthermore, perforating cutaneous vessel branches of the dorsal thoracic artery are small, which makes the surgery di cult to cut the free skin ap for transplantation, and the incidence of postoperative vascular crisis is high 15,16 . Although the PLDMF can meet the requirements for the repair distance of the soft tissue defect of the shoulder and the survival rate of the ap, the scar is located on the shoulder after the skin ap grafting, which is easy to cause friction and has a certain in uence on dressing, especially for female patients who feel discomfort when wearing a bra, and the aesthetic outcome is poor.

Conclusion
The use of the PLDMF to repair large areas of soft tissue defects in the neck and shoulder combined with infection can provide better joint protection to the shoulder joints, and has very good anti-infection ability.
And also, it is very easy to harvest the ap, and the survival rate is high. However, the cut distance of this ap is relatively short. When designing the ap, the distance and range of the soft tissue defect should be measured in detail to avoid the occurrence of changing the surgical plan after the operation. Moreover, the aesthetic outcome of this ap transposition is poor and has a certain impact on dressing, therefore, it should be avoided for young female patients. Figure 1 a Flap design and incision. b Latissimus dorsi ap inverted to cover the soft tissue defect of the shoulder.

Abbreviations Figures
c Appearance after the skin ap transplantation.  c local appearance.