Case 2: Reconstruction of an extensive foot defect using a combined sensory split latissimus dorsi and serratus anterior muscle flap

Keywords: Lower extremity; Flap; Reconstruction; Soft tissue; Trauma; Microsurgery; Foot; Latissimus Dorsi;

Authors: Dr. med. Luisa Lotter, Dr. med. Ilja Käch, PD Dr. med. Volker Schmidt. Institution: Kantonsspital St. Gallen, Switzerland

Abstract

A 67-year-old male patient sustained a complex foot injury with an open Lisfranc dislocation of the medial cuneiform bone and shaft fractures of the 2nd to 4th metatarsals in July 2024, as a result of a crush trauma. After initial osteosynthetic treatment, a pronounced necrosis developed in the area of the hindfoot and forefoot over time and an implant-associated wound infection. The patient was then transferred to our tertiary care hospital for specialized defect reconstruction. At first radical necrosectomy was performed, resulting in a 10 x 12 cm soft-tissue defect in the heel area, which extended medially and laterally. In the area of the forefoot, there was also a full-thickness wound measuring 4 x 3 cm with exposed osteosynthetic material, bone, and tendon.

Patient medical history

The patient has no pre-existing conditions. Blood tests on admission showed a blood glucose level and HbA1c value within the normal range. An angiography was performed, revealing a regular three-vessel supply to the affected lower right leg.

Before and After

Upon admission to our hospital, on assessment, the 67-year-old male patient was in good general health with a slim nutritional status. On the heel area of the right foot was a 10 x 12 cm soft-tissue defect, which extended medially and laterally. In the area of the forefoot, there was also a full-thickness wound measuring 4 x 3 cm with exposed osteosynthetic material, bone, and tendon. Blood tests on admission showed a blood glucose level and HbA1c value within the normal range. An angiography was performed, revealing a regular three-vessel supply to the affected lower right leg.

The reconstruction of complex soft tissue injuries with exposed osteosynthesis material is particularly challenging in the load-bearing areas of the lower extremities. The use of free flap grafts is often the only promising option in these cases. The following preoperative considerations were taken into account:

1. The heel requires adequate soft tissue coverage and stability to withstand the high load in daily life. Flap reconstructions with a muscular component covered with mesh-graft are particularly suitable for this purpose.

2. Due to the size of the defect and the complex spreading pattern, a relatively large free microsurgical flap is required. By harvesting the latissimus dorsi muscle, large defects can be covered. To minimize donor site morbidity and ensure unrestricted shoulder function (especially adduction and internal rotation), the medial part of the latissimus dorsi muscle was preserved. The complete latissimus dorsi muscle as a free microvascular flap is usually too bulky for defect coverage, so splitting the muscle is a suitable approach.

3. To cover the defect in the dorsum of the foot, we need a thin, small, and easily moldable flap. The distal slips of the serratus anterior muscle are well-suited for this purpose. Thus, we have opted for a combined free microvascular flap with shared vascular supply.

4. For anatomical walking, proprioceptive feedback is of critical importance. Therefore, the sensory connection of the flap reconstruction should also be considered.

5. To be able to wear regular footwear after the reconstruction, the integration of the flap into the surrounding tissue is essential.

1

Wound debridement

The wound bed was prepared by debriding non-viable tissue and taking precise measurements of the skin and soft tissue defect. Exposed functional structures were identified and measured. A 3 cm section of the osteosynthesis material, as well as the tendon of the extensor hallucis longus muscle, were exposed. Additionally, there was only a very thin soft tissue covering over the heel.

2

Preparation of the recipient site

Before the defect was covered by a free microsurgical flap, the osteosynthesis material was replaced by the orthopaedic team due to a preceding implant-associated infection. The posterior tibial artery and the saphenous nerve were exposed up to 5 cm.

3

Flap dissection

For the defect coverage, a combined microsurgical flap procedure consisting of the lateral portion of the latissimus dorsi and the distal three slips of the serratus anterior muscle was planned. At the beginning, the vascular supply of the M. latissimus dorsi, including the thoracodorsal nerve, long thoracic nerve, and serratus arcade, is visualized. It is particularly important that the dorsal branch of the thoracodorsal nerve is preserved, as it is essential for the motor function of the medial portion of the latissimus muscle, which will be left in situ.

4

Flap harvesting

This is followed by mobilization of the latissimus dorsi muscle and detachment of the lateral portion, as well as the distal three slips of the serratus anterior muscle. The common vascular pedicle is followed up to the origin of the circumflex scapular artery, and the flap is then detached along with the thoracodorsal nerve. The medial part of the latissimus dorsi muscle is preserved (marked in green).

5

Microsurgical Anastomoses

Microsurgical anastomoses of the perforator: arterial anastomose to the posterior tibial artery were established in an end-to-side fashion using Dafilon 8-0. The vein was anastomosed end to end to the concomitant veins of the posterior tibial artery using a 2.5 mm coupler. The branch of the thoracodorsal nerve was connected to the sensory branch of the saphenous nerve epineurally using a 3 cm nerve allograft and Dafilon 9-0.

6

Transplantation of the flap – covering with mesh graft

The flaps were accurately modelled to meet the defect configuration and two Charrier Redon drains were inserted. The skin was removed, and the entire flap was covered with mesh graft from the ipsilateral thigh.

Swollen foot with visible redness and scarring
7

Follow-up

Follow-up

Pearls

•By splitting the latissimus dorsi muscle with nerve preservation and performing primary wound closure, the morbidity of the donor site can be minimized and unrestricted shoulder function (especially adduction and internal rotation) can be ensured.

•The sensory connection of the flap allows for safe walking through sensory feedback. Additionally, this protects the flap from excessive stress.

•The coverage of a complex and wide injury pattern can be achieved through a combined free microsurgical flap.

Pitfalls

• For coverage in the area of the lower extremities, adequate blood supply is necessary. Therefore, a CT angiography should always be considered in patient > 50y, or with CVRF as well as severe trauma. If a significant stenosis of the lower extremities is present, consideration must be given to performing a percutaneous transluminal angioplasty (PTA), a bypass surgery, or the placement of an arteriovenous (AV) loop.

• Due to the thick subcutaneous fat layer of the M. latissimus dorsi, the skin shifts continuously relative to the muscle under load, which can lead to the formation of a bursa and ulcerations. In recent years, the free muscle graft with mesh graft has proven to be more resilient.

• Once two or more defects in adjacent locations with complex spread patterns need to be covered, a combined free microvascular flap should be used. The entire latissimus dorsi muscle often adds bulk due to its thickness and is difficult to model. Additionally, by splitting the muscle, the morbidity of the donor site remains lower.

• Prolonged surgery time when harvesting combined flaps.

Post-operative plan

• The patient should remain sedentary in bed for five days with hourly monitoring of the perfusion of the flaps for 24 hours.

• Following that, the flaps undergo flap dangling to gradually subject the flaps to the increased venous pressure induced by the gravitational forces.

• The patient must be monitored on an outpatient basis and scheduled for follow-up visits at two weeks, six weeks, three months, and 12 months after the surgery.

• The patient was fitted with a custom-made splint. Due to the osteosynthesis, only partial weight-bearing of 15kg for six weeks was allowed. A notch was made in the flap area to reduce external pressure while simultaneously ensuring a prophylaxis against equinus foot.

References

  • Harvey Chim, Rachel Cohen-Shohet, Mariel M McLaughlin, Tosan Ehanire. Function-Sparing Free Split Latissimus Dorsi Flap for Lower-Extremity Reconstruction: Five-Year Consecutive Single-Surgeon Series. J Bone Joint Surg Am . 2020 Oct 7;102(19):1714-1723. doi: 10.2106/JBJS.20.00022
  • Thomas Albert, Stéphane Guero, Clément Deranque, Pascal Rousseau. Combined free flap of muscle-sparing latissimus dorsi and serratus anterior in the repair of child’s traumatic foot injury: a case report. Pan Afr Med J. 2024 Jul 9;48:91. doi: 10.11604/pamj.2024.48.91.43952

Contents

Case 2: Reconstruction of an extensive foot defect using a combined sensory split latissimus dorsi and serratus anterior muscle flap