The Hemirectus/Anterolateral Thigh Chimeric Flap: An Alternative in the Setting of Variable and Unfavorable Vascular Anatomy

Sir,

Though the thigh is a reconstructive warehouse, the vascular supply of the anterolateral thigh (ALT) flap based off the descending branch of the lateral femoral circumflex artery (LCFA) may be highly variable.¹ When harvesting a chimeric flap for a wound with multiple requirements, this variable anatomy requires creative solutions. In this case report, we describe a 61-year-old diabetic man with 2 wounds of both the medial and lateral malleoli with exposed tibia and fibula as a result of orthopedic hardware placement following a trimalleolar ankle fracture. After fixation, an infection ensued, resulting in deep wounds and osteomyelitis with significant skin deficit necessitating flap coverage.

Our standard approach to wounds of such complexity is to design a chimeric flap composed of fasciocutaneous ALT and muscle from the vastus lateralis based on independent perforating branches off of the descending branch of the LCFA. As favorable anatomy was not present, we turned our attention toward designing a chimeric flap composed of a fasciocutaneous ALT and muscle from the rectus femoris (Fig. 1).

Fig. 1.

Upon harvest, the main blood supply to the vastus lateralis originated directly from the profunda femoris. We found a type III muscle, determined by functional testing: we occluded both branches and dopplered all portions of the rectus femoris. We elected to pursue a hemirectus anterolateral thigh flap.

The vascular anatomy of the rectus femoris flap has been well-characterized by Arai et al² with generally 2–3 muscular branches originating off of the branches of the LCFA and entering the superomedial muscle belly. This group has categorized the intramuscular arterial supply into 3 types based off the dominant branch supplying the muscle belly and noted that the muscle belly is divided into a medial and lateral half by an intramuscular tendon under which arterial branches travel to supply the lateral half. This perfusion pattern would allow us to potentially design a muscle-sparing flap. After identifying 3 muscular branches to the rectus femoris, we proceeded to design a flap of both fasciocutaneous ALT and hemirectus (medial muscle belly) based off the third muscular branch with the proximal 2 branches left behind to perfuse the remaining lateral hemirectus in situ. We performed functional testing of intramuscular perfusion by clamping each branch and ensuring dopplerable signals remained in each half of muscle supplied by the unclamped vessels. As described by Arai et al,² these tests confirmed a Type III muscle, wherein 3 branches exist to the rectus femoris and the third branch adequately perfuses the distal muscle.

Importantly, after division of the hemirectus flap, we were able to stimulate muscle contraction of the remaining orthotopic rectus muscle and to identify dopplerable signals through the muscle belly. We further performed a tenodesis of the remaining rectus femoris muscle to the vastus lateralis distally to allow for stabilization of the knee joint. We believe that harvesting a hemimuscle flap in this way will allow the patient to maintain adequate quadriceps function given the minimal donor morbidity demonstrated in full rectus femoris muscle sacrifice.³

This technique is a novel approach to performing a chimeric flap to cover complex or multiple defects when favorable anatomy is present, while preserving adequate donor site function (Fig. 2). To our knowledge, this is the first description of performing a hemirectus femoris flap in this way.

Fig. 2.

The appearance of the after microvascular anastomosis to the anterotibial artery and flap inset.