Distal major pedicle of sartorius muscle flap: Anatomical study and its clinical implications.

Background: Reconstruction of the popliteal region has limited option in terms of muscle flaps or myocutaneous flaps. Gastrocnemius muscle or the myocutaneous flaps are the option for majority of cases. However, reach of Gastrocnemius is limited if the wound is on the distal one-third thigh or the lateral aspect of knee region. Similarly, if the wound injures the muscle, then coverage becomes all the more difficult. Although inferiorly based fasciocutaneous flaps can cover the wound in case of bony injuries, muscle flaps are beneficial as they help in fracture healing. However, in cases with direct gastrocnemius muscle injury or if the wound on the distal one-third thigh or the lateral aspect then the options of muscle flaps is limited. An inferiorly based sartorius muscle can be one suitable alternative to cover this region.

Aims and Objective: The aim is to devise an inferiorly based sartorius muscle flap for coverage of lower thigh, popliteal and upper one-third leg region.

Objectives: (1) To identify the location of distal major (largest diameter) pedicle in cadavers and its clinical application. (2) To determine the arc of rotation with distal major pedicle as pivot point.

Methods: Ten Cadavers and 20 sartorius muscle dissected out. Prior silicone injection onto the femoral vessels was done to identify the location of the perforators for the sartorius muscle. The distance of perforators from anterior superior iliac spine (ASIS) measured and the diameter of each perforator by transverse cut measured using callipers. In clinical cases, the arc of rotation was measured by keeping the distal perforator intact as pedicle (detaching the muscle from the ASIS without detaching from the insertion and then rotating it).

Results: Out of the 10 cadavers analysed, 6 were male and 4 were female. The mean location of the distal major pedicle was at 35.25 cm from ASIS and range was between 30.4 cm to 38.3 cm. There was no significant variation between right and left limbs in individual cadaver (range 0.2 cm-1.6 cm). The mean diameter of the arterial component of distal major pedicle was 1.54 mm. In three clinical cases where this flap was harvested the arc of rotation were 95°, 110°, 125°. In one of the cases where flap was used to cover the tibial plateau (arc of rotation 155°), distal end of the muscle necrosed.

Conclusion: This cadaver study supported by various other studies show that it has sizeable distal pedicle based on which whole muscle can be harvested as flap. In our study, the usual location of this pedicle is at 35 cm from ASIS. The mean diameter of the widest pedicle in distal one-third was 1.54 mm which along with other small diameter pedicle can support the entire muscle. This flap reached up to the infrapatellar region without any vascular compromise.