Exposure
- The “ABC method” is another method used to identify perforators without the use of intraoperative Doppler. The main “B” perforator is identified according to the method described in the video. The “A” and “C” perforators are found 5cm proximal and distal to the “B” perforator1.
- In patients with muscle atrophy note that the rectus femoris muscle may be more medial than expected. Care should be taken during the initial incision to avoid inadvertently making the incision too lateral. It is often possible to palpate the rectus muscle.
- Placement of medial incision is crucial; too medial will create a wide flap, too lateral will risk injuring perforators.
Perforator Dissection
- The origin of the descending branch can vary. Depending on the study 75-100% of descending branches arises from the lateral circumflex femoral artery (LCFA). However, it can also arise at the origin of the LCFA, the profunda femoris, or from the common femoral artery2-4.
- The origin of perforators can vary as well. Perforators will usually arise from the descending branch but can arise from the ascending branch, the transverse branch, an oblique branch paralleling the descending branch, or rarely from the profunda femoris artery. In 1.8% of cases no perforator is identified2,4.
- 13-21% of perforators are septocutaneous and pass between vastus lateralis and rectus femoris, 79-87% are musculocutaneous and travel through vastus lateralis5,6.
- Compared to Type B and C perforators, a higher proportion of Type A perforators are septocutaneous1,2.
- Perforators can also be identified using a suprafascial dissection above the tensor fascia lata. In these dissections the perforators can be sheared with traction on the skin. We generally prefer to do a subfascial elevation to identify the perforators. In certain reconstructions such as pharynx reconstruction harvesting the fascia with the flap is beneficial. In reconstructions where fascia is not required most of the fascia is able to be preserved with a small cuff of fascia taken around the perforator to prevent twisting. When the fascia is preserved it can be reapproximated in the area that it was preserved but left open in the area where the fascia was resected with the flap.
- Musculocutaneous perforators will give branches to the vastus lateralis. These branches typically arise from posterior and lateral aspect of the perforator, and are rarely anterior5.
Descending Branch Dissection
- Vastus lateralis branch of the posterior division of femoral nerve travels with the descending branch of lateral circumflex femoral artery and can be preserved.
- The profunda femoris (or deep femoral) is the major deep arterial branch of the femoral artery that becomes the popliteal artery. The lateral circumflex femoral arises from the profunda femoris artery, although occasionally it may arise directly from the femoral artery. The profunda femoris or femoral artery are the limits of pedicle dissection.
- The LCFA gives off three branches including the descending branch, which serves as the main pedicle.
- Paired venae comitantes reliably travel alongside the arterial pedicle.
Closure
- The maximum diameter that allows for primary closure is roughly 9cm, although the width that can be harvested ultimately depends on the leg skin laxity5. Pulley stitches can be used to create mechanical creep and help would closure.
Modifications
- Sensate flap can be harvested by incorporating lateral femoral cutaneous nerve.
- Chimeric flap can be designed by using multiple perforators. Two or more perforators are identified in 74% of patients2.
- Tubed flaps for pharyngeal reconstruction. A minimum width of 9cm to achieve a 3cm diameter tube. An extension of this is the “papillon” flap that includes a portion for external skin defects7.
- Innervated vastus lateralis has been described for dynamic midface reanimation for radical parotidectomy defects8.
- It may be possible to pivot to anteromedial thigh skin paddle if no lateral perforators are identified.
References
- Lin S, Rabie A, Yu P. Designing the Anterolateral Thigh Flap without Preoperative Doppler or Imaging. J Reconstr Microsurg. 2010 Jan;26(1):62-72.
- Yu P. Characteristics of the anterolateral thigh flap in a Western population and its application in head and neck reconstruction. Head Neck. 2004;26:759-769.
- Kimata Y, Uchiyama K, Ebihara S, Nakatsuka T, Harii K. Anatomic variations and technical problems of the anterolateral thigh flap: a report of 74 cases. Plast Reconstr Surg. 1998 Oct;102(5):1517-1523.
- Lakhiani C, Lee M, Saint-Cyr M. Vascular Anatomy of the Anterolateral Thigh Flap: A Systematic Review. Plast Reconstr Surg. 2012 Dec;130(6):1254-1268.
- Wei F, Jain V, Celik N, Chen H, Chuang D, Lin C. Have We Found an Ideal Soft-Tissue Flap? An Experience with 672 Anterolateral Thigh Flaps. Plast Reconstr Surg. 2002 Jun;109(7):2219-2226.
- Smith R, Wykes J, Martin D, Niles N. Perforator variability in the anterolateral thigh free flap: a systematic review. Surg Radiol Anat. 2017;39:779-789.
- Ghazali N, Hanna T, Dyalram D, Lubek J. The Value of the "Papillon" Anterolateral Thigh Flap for Total Pharyngolaryngectomy Reconstruction: A Retrospective Case Series. J Oral Maxillofac Surg. 2016 Feb;74(2):406-414.
- Chong L, Eviston T, Ashford B, Ebrahami A, Clark J. Single innervated segmented vastus lateralis for midfacial reanimation during radical parotidectomy. Head Neck. 2017 Mar;39(3):602-604.