Annals of Burns and Fire Disasters - vol. X - n. 3 - September 1997

ANATOMICAL STUDY OF THE MEDIAL SEPTOFASCIAL FLAP OF THE LEG - ITS POSSIBLE CLINICAL APPLICATIONS

Al-Sayed Mandour Ismail

Plastic and Reconstructive Unit, Faculty of Medicine, Tanta University, Tanta, Egypt

SUMMARY. Most anatomical and injection studies on the septocutaneous vessels of the leg have been performed without separation of the septocutaneous flap as an island-pedicled flap. Using observations on work done in our Unit with the distally based adipofascial flap in the leg and foot, we studied the anatomy of the medial septofascial flaps by an injection study on cadaver after separation of the flaps from the surrounding skin. Seventeen limbs were examined in the study. Our results showed that the subfascial plexus is more important than the suprafascial plexus if the flap is used as an island-based flap on the lower septal vessel. If the adipofascial flap is used as an island flap, the fatty layer does not prove a good surface to carry the split-skin graft until after the formation of granulation tissue from the perforating vessels. However, if this fatty layer is removed (septofascial flap), it can be a good surface to carry a split-skin graft, owing to the good blood supply of the fascia. The distally based septofascial flap without the skin and subcutaneous fat can reach any distance, from the midleg to the great toe, and can be a vehicle to carry a split-skin graft, thus solving many clinical problems in the lower leg and foot, such as chronic ulcers and deep burns. This is the basis of research currently in progress in our unit.

Introduction

With regard to skin circulation, some strong anatomical data support the assumption that septocutaneous vessels are at least as important as musculocutaneous and axial vessels. Several types of fasciocutaneous flaps can be based on septal pedicles.1-1 Most anatomical studies on the septocutaneous vessels of the leg describe the fascial network as being composed of two layers, subfascial and suprafascial, and consider the suprafascial layer to be more important than the subfascial plexus.'-' Bearing in mind research already conducted in our Unit using the distally based adipofascial flap in the leg and foot,' we studied the anatomy of the medial septofascial flaps by an injection study of cadavers after separation of the flaps from the surrounding skin.

Material and methods

Seventeen limbs were dissected for the arterial supply of the medial septocutaneous flaps of the leg. Ten limbs were from formalin-preserved cadavers, six were from fresh cadavers, and one was amputated following an accident. Injection studies were performed on the seven fresh limbs. The diameters of the septocutaneous arteries were measured, as well as their distance from the medial malleolus.

Technique
The flap was marked on the skin and raised with the deep fascia (Figs. 1,2). The septal branches were dissected, and their origin, course and distribution identified and left intact (Figs. 3,4). The lowermost septal branch was cannulated at its origin and injected with 20 ml methylene blue or India ink (Fig. 5). Seven limbs were injected through the lowermost septocutaneous vessel (three after separation of all septal branches except the lowest and four before ligation and separation of the other vessels).

Fig. I - Marking the flap (25 x 12 cm). Fig. 2 - Dissection of flap together with deep fascial layer (starting from posterior part)

Fig. 3 - Dissection of medial septocutaneous vessels in fresh cadaver. Fig. 4a - Formalin-preserved leg. Six septocutaneous vessels arising directly from posterior tibial vessels. Lowermost vessel 6 cm and uppermost vessel 18 cm from medial malleolus. Fig. 4b - Formalin-preserved leg.Six septocutaneous vessels arising directly from posterior tibial vessels. Lowermost vessel 6 em and uppermost vessel 18 em from medial malleolus

Results

Anatomical findings
The septal vessels are direct branches of the posterior tibial artery (Figs. 3,4a/b); they do not originate from collateral vessels. Each septocutaneous artery has one and sometimes two venae comitantes (Fig. 4b). These veins directly join the deep trunk. We found three septocutaneous vessels in five limbs, four vessels in four limbs, five vessels in four limbs, and six vessels in four limbs (Figs. 3,4). The distance of their origin measured from the tip of the malleolus was 4 cm for the lowermost one and 18 cm for the uppermost one. The uppermost of these vessels pierces the fascia, pressing through the tibial origin of the soleus just behind the medial border of the tibia. The lowermost medial septocutaneous vessel becomes superficial after passing between the flexor digitorum longus and soleus muscles and the Achilles tendon (Fig. 4).
The external diameters of the arteries varied from 0.5 to 1.7 mm. Arteries of larger diameters were found in the middle of the leg (Fig. 4b).

Results of injection study

Limbs injected before separation and dissection of the skin and subcutaneous fat showed good perfusion of the dye to the skin, dermal and subfascial plexuses. Dissection of the skin and subcutaneous fat from the fascia showed faint colouration of the suprafascial plexus, and fine vessels could be seen in the fat layer (Figs. 5,6).
Limbs injected after cutting and ligation of the middle and upper septal vessels also showed good perfusion of the skin, dermal and subfascial plexuses. However, when the skin and subcutaneous fat were dissected from the fascia, the suprafascial plexus could not be visualized, the fine vessels in the fat layer became fewer, and three or four perforating branches could be seen traversing the fat layer without forming any branches (Figs. 7,8).
In all cases, the subfascial plexus was more prominent and well vascularized (Fig. 9).

Fig. 5 - Lowermost septal vessel cannulated and 20 ml dye (methylene blue) injected. Fig. 6 - Good perfusion of dye to skin and dermal plexus and faint cotouration of superfascial plexus. Fig. 7 - The suprafascial plexus cannot be visualized. Two perforating branches can be seen traversing fat layer without forming any branches to the fat layer. Fig. 8 - Good visualization of subfascial plexus in all cases. Fig. 9 - Good visualization of subfascial plexus in all cases.

Discussion

The coverage of distal soft tissue and bony defects of the leg has long been recognized as a difficult clinical problem. Distally based fasciocutaneous flaps with majorarteries in their pedicles have been described. However, these flaps have the disadvantage of necessitating the sacrifice of a major limb artery. Also, the reversal of venous flow in this type of flap increases the degree of venous compromise
The use of local fasciocutaneous, septocutaneous, myocutaneous and free flaps is often associated with significant donor site defects and is cosmetically unacceptable for the majority of the patients. Gumener et al. designed a distally based pedicled fasciocutaneous flap from the calf to cover soft tissue defects in the malleolar region and heel. Medial island septocutaneous flaps for the repair of soft tissue defects have been used in our Unit for the last eight years.` The island adipofascial flap based on septocutaneous perforators for resurfacing distal lower limb defects was the basis of a study that we conducted. However, we noticed partial graft loss whether the graft was placed on the fatty layer or on the reverse surface. For this reason we decided to perform an anatomical study of the medial island fasciocutaneous flap based on the lower septocutaneous vessels.
Our results showed good perfusion of the whole flap. Removal of the skin will however affect the blood supply of the fatty layer (Fig. 7). The results also showed that the subfascial plexus is larger and more prominent than the suprafascial plexus, contrary to the findings of Carriquiry et al. This may be explained by the fact that in Carriquiry's work the injection studies were performed without separation of the flap, which might affect the haemodynamics inside the flap. Our results also explain why Jayaraman," Mathivanan and Ramakrishnam," and Arianayagam," when describing fascial, inferiorly based turnover flaps, attributed their vascularization to the abundant vascular supply in the under surface of the deep fascia. Lees and Townsend" were the first to report the use of the pedicled fascial flap based on septocutaneous perforators of the posterior tibial artery for repair of a distal lower limb defect (two cases). If this flap is raised as an island on the lower septal vessel, it will have a wide arc of rotation (figs. 10/a/b/c/d).

Fig. 10a - Wide arc of rotation of medial septofascial flap from midleg to great toe. Fig. 10b - Wide are of rotation of medial septofascial flap from midleg to grat toe. Fig. 10c - Wide arc of rotation of medial septofascial flap from midleg to great toe. Fig. 10d - Wide arc of rotation of medial septofascial flap from midleg to great toe.

On the basis of the above findings we can make the following conclusions:

• the medial island septofascial flap has a good blood supply, mainly from the subtascial plexus and partly from the suprafascial plexus, and it can be a good surface to carry split-skin graft for the solution of many problems in the lower leg and foot

• island septocutaneous flaps should be used without separation of the skin from the flap

• turnover of the island adipofascial flap and the positioning of the split-skin graft on the under surface of the fascia affect the subfascial plexus, owing to the thickness of the fatty layer, and the use of fascial flap alone is preferred

Island septofascial flaps have the following advantages:

• simplicity of raising the flap

• significant reduction in donor site morbidity

• either side of the fascia can be grafted

• the flap is useful on the dorsurn of the foot as it provides a surface under which tendons can freely glide

RESUME. La plupart des études anatomiques et d'injection sur les vaisseaux septocutanés de la jambe ont été effectuées sans la séparation du lambeau septocutané comme lambeau à pédicule en îlot. En utilisant des observations sur des recherches faites dans notre Unité avec le lambeau adipofascial à base distale pour la jambe et le pied, nous avons étudié l'anatomie des lambeaux septofasciaux médians à travers une étude d'injection sur le cadavre après la séparation des lambeaux de la peau environnante. Dix-sept membres ont été examinés dans l'étude. Nos résultats ont montré que le plexus subfascial est plus important que le plexus suprafascial si le lambeau est employé comme lambeau à base en îlot sur le vaisseau septal inférieur. Si le lambeau adipofascial est employé comme lambeau en îlot, la couche grasse ne se révèle une bonne surface pour porter la greffe d'épaisseur variable qu'après la formation du tissu granuleux depuis les vaisseaux perforants. Cependant, si cette couche grasse est énlevée (lambeau septofascial), cela peut se révéler une bonne surface pour porter la greffe d'épaisseur variable, à cause du bon afflux de sang dans la fascia. Le lambeau septofascial à base distale sans la peau ni la graisse sous-cutanée peut s'étendre à toutes les distances, du milieu de la jambe au gros orteil. Il peut en outre constituer un véhicule pour porter la greffe d'épaisseur variable pour résoudre beaucoup de problèmes cliniques de la jambe inférieure et du pied, comme par exemple les ulcères chroniques et les brûlures profondes. C'est la base des recherches que nous conduisons actuellement dans notre Unité.

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