Fixation Techniques to Maintain Position for a Cross Leg Flap: Technical Tips and Algorithmic Approach

Le résumé fourni par la source

High-speed road traffic accidents may lead to composite or soft tissue defects in the leg. In cases of severe leg trauma specially in vessel depleted leg, cross leg flap remains the lifeboat solution for wound coverage. With the advent of microsurgical techniques, the frequency and indications of cross leg flaps procedure has reduced. Nevertheless, it is advisable to have cross leg flap in the reconstructive armamentarium to be used in relevant situations as a last resort or in places where the microsurgical expertise is not available.[ 1 ] A cross leg flap is one which has its vascular pedicle attached to the uninjured limb while being inset onto the defect on the injured opposite limb. It may be inferiorly based fasciocutaneous flap or a standard (medially based) cross leg flap or a propeller perforator flap or even a free flap[ 2 ] with anastomosis done to a pedicle taken from the uninjured limb. In case of a cross leg design, the advantages of the propeller flap may be lost as the distal part of the flap may not cover the donor defect as the turn may be just 90 degrees. The common prerequisite in all these cases is a very stable fixator system to maintain the relative position of the two limbs (to prevent undue tension on the carrying segment or the vascular pedicle). This fixation is crucial for the flap survival as well as for patient comfort in the postoperative period. Fixation may be achieved by Plaster of Paris (PoP) splints or by placing external fixators in the limbs. In this paper, the authors discuss the process of decision-making regarding the type of the fixation technique and some technical tips on fixation. Informed consent was taken from all patients for the purpose of this paper. The first step is to “plan-in-reverse.” Placing the flap over the defect, the carrying segment should then be placed on the other (uninjured) limb in the most suitable position. The suitability of the position is decided by the patient's comfort and the ease of the flap to reach the defect in the most efficient manner. The aim is to place the base of the flap close to the defect on the other limb in a comfortable position (to be maintained for 3 weeks). For this purpose, five commonly used limb positions are shown in [ Fig. 1 ]. It is important to understand that these are the most commonly used positions and there may be variations of these both in terms of longitudinal and rotational positioning between the two legs as per the requirement of the situation. Fig. 1 The commonly used positions for performing a cross leg flap. Suitable position must be chosen as per the type of flap and the patient's comfort. Generally, for an inferiorly based flap, it is advisable to place the donor foot flat on the bed and just adjacent to the recipient leg defect and for a standard design, a parallel or crossover placement may be needed. In case of cross leg free flaps, posterior tibial vessels may be best used for anastomosis and therefore the limb placement should aim at attempting to bring the ankle close to the point of pedicle exit on the recipient limb. Planning should always allow separation of minimum 2 to 3 cm between the legs so that they do not touch and form pressure sores. This is important, as despite the best attempts at rigid fixation, there is always some laxity and there is a chance that the legs may touch each other. The flap is raised according to this plan and secured to the donor limb with a mop and bandage. Now the required position is communicated to the orthopaedic surgeon. Often the fixator placement seems daunting and complicated. The authors propose an algorithmic approach to decide on the type of fixator frame that may be devised. There are four sets of pins used ([ Figs. 2 ] and [ 3 ]): Fig. 2 Schematic diagram showing the hierarchy of fixator placement for a cross leg flap. 1st set pins are shown marked in Black , 2nd set rods in Blue , 3rd set rods in Green , and 4th set rods are in Yellow . Fig. 3 Cross leg frame in a patient showing color coding for 1st, 2nd, 3 rd , and 4th set of pins is as described in [ Fig. 2 ]. Opposite side pins have not been colored for the sake of clarity. 1st set: 3.5-mm Shantz pins which take purchase in the bone. Generally, three vertical pins are placed through the subcutaneous border of tibia. Three pins proximal to the fracture site and one or two pins distal to the fracture site are placed in the injured limb. These may be placed little obliquely to avoid colliding with the pins in the other limb. 2nd set: connecting rods to stabilize the 1st set pins. Generally, two horizontally placed rods are connected using universal joints. 3rd set: connecting rods to hold the limb in relative position. At least two 3rd set connecting rods are placed between the 2nd set rods of both legs to keep them in desired relative position. These may be vertical, horizontal, or oblique as the position demands. 4th set: Rods form a kickstand providing elevation to the whole construct. One proximal and one distally placed vertical rod on each limb to form the elevated kickstand. Additional horizontal connecting rods may be added below the legs to prevent splaying of the kickstand rods and to increase the stability of the construct ([ Fig. 3 ]). If the 3rd set rod is horizontally placed, → connects directly to 4th set rod If the 3rd set rod is oblique/vertically placed→ connects to a horizontal rod→ connects to 4th set rod Positioning may be hindered by the fixator pins in the foot→ frame may need to be modified to accommodate space for the adjacent limb If the knee needs to be flexed, additional 1st and 2nd set pins may be placed in the lateral aspect of femur and connected to the tibia pins to maintain the requisite angle as shown in [ Fig. 4 ]. In case of a free flap, the 1st set pins should be put before anastomosis and rest can be applied after that. Fig. 4 1st and 2nd sets of pins may be placed in the lateral aspect of femur and connected to the tibia pins to maintain the requisite angle in case the knee needs to be kept flexed. Final insetting of the flap should be done once the legs are properly fixed in position. The sequence of events for a cross leg free flap is as follows: First, Team 1 creates the defect and performs donor vessel dissection on the opposite leg. Following this Team 1 puts the 1st and 2nd set of fixator pins. In the meantime, Team 2 harvests the flap and following this, the anastomosis is done to the donor vessel while the flap is tagged to that limb with temporary sutures. The anastomosis is done with posterior tibial artery (PTA), either as an end-to-end or an end-to-side (ETS) anastomosis. ETS anastomosis may provide a better configuration for the exit of the pedicle towards the recipient limb as a slightly longer pedicle length may be achieved. It is useful to harvest a fascial flap above the PTA to cover the anastomosis as it travels to the other limb. Dressing is done and 3rd and 4th set of pins are now placed to fix the two legs in proper position. Lastly, the flap is inset into the defect. When the recipient limb has fractures, the 1st set pins are used to stabilize the fracture primarily. In the postoperative period, pin track dressing is given. Both the legs with the frame should be placed over a wide plyboard (and not directly on the wobbly mattress) so as to provide a stable base. Patient should be given a water/air bed and advised position changes to prevent formation of sacral or ischial or scapular pressure sores. Since the fixation is semirigid and slight movement may occur over time, it is important to tighten the link joints on alternate days (as the frame tends to become loose gradually) and to keep air/water-filled gloves or gamjee rolls to maintain the distance between the legs. For doing local flap dressings in between the frame, long forceps may be useful. After 3 weeks, the flap is trained/delayed, which may be done by applying a clamp (if the carrying segment is flat) or by tyi

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.