Complex soft tissue defect in the knee regions often was caused by multiple previous operation, high energy trauma and large soft tissue tumor excisions, those always resulted in various tissue defects, including bones, skin, and extensor mechanism. Soft-tissue reconstruction in the knee regions requires thin, flexible, large cutaneous area and multiple components. It was commonly considered that the local or pedicled flap was the optimal choice in many cases of soft-tissue reconstruction around the knee.11 Recently, Ling et al12 recommended the medial sural artery perforator (MSAP) flap as the first choice for soft-tissue defect reconstruction around the knee. However, the local flaps and pedicled flaps were only the optimal choice for repairing a small to medium-sized defects of the knee because of limitation of the volume soft tissue. Descending branch of anterior lateral thigh perforator (dbALTP) also have been reported as a reconstructive solution for soft tissue defects of the knee13. But it has never gained popularity among reconstructive surgeons because of venous congestion and difficult flap dissection in the presence of a variable anatomy of the vascular pedicle.14 In addition, Limited arc of rotation and reach of those flap are major disadvantages. Those were the impetus to look for an alternative flap.
Previous study showed that free flap would be an ideal choice when local tissue options are unavailable or inadequate, specially, when the vascular web around the knee has been damaged. Free muscle flap such as latissimus dorsi and gracilis muscle flaps has been reported as a reliable alterative approach for reconstruction of the complex tissue defect in the knee region, because of its rich blood supply and large area. 15,16 Those advantages are specifically indicated more complex soft defects with joint and/or prosthesis exposure. However, problems of donor-site morbidity and bulkiness of flaps remain. In this study, we presented a case series of complex soft tissue defects reconstruction in the knee region by using various flap designs, including free ALTP flap, ALTP flap with partial fascia lata, chimeric ALTP flap, dual skin paddles ALTP flap, chimeric TDAP flap and multiple perforator flaps combination with vascularized fascia lata. To our knowledge, this is the largest series to date reporting microvascular reconstruction of complex soft-tissue defects in the knee region by using the free perforator flap. Our report focuses on the individual flap design for customized reconstruction of complex soft tissue defects in the knee region to minimize the donor site morbidity and gain acceptable knee function recovery, that have rarely been addressed before.
Recently, the flap donor site as limited resources has attracted the attention of reconstructive surgeons.17 One of the most important goals of modern reconstructive microsurgery is to minimize donor-site morbidity. Reconstructive surgeon has shifted their focus from pure coverage of soft tissue defect to now include the functional donor site issues and aesthetic appearance of the donor site as well. In this context, harvesting a free perforator flap by using a traditional fashion design may be not suitable to reconstruct very large soft tissue defect because of the limitation of soft-tissue amount which will result in a nonaesthetic donor-site skin graft.8 Recently, dual skin paddles perforator flap was introduced as an ideal approach to reconstruct very large soft tissue defect and maintain the primary closure of donor site.18,19 Zhang et al17 have reported that dual skin paddles perforator flap allows dual skin paddles to be placed side by side and effectively doubling the width of the flap by using a kiss technique. Our previous study also demonstrated that the dual skin paddles ALTP flap was an alternative option to repair extensive soft tissue defect in the foot and ankle.20 However, to our knowledge, there is no literature which has described the use of the dual skin paddle perforator flap for repairing the complex tissue defect in the knee region. In the present cases, the double skin paddle ALTP flap was successfully used to cover very large soft tissue defect in two cases, and the donor site were achievement of primary closure of donor site.
High energy trauma and soft tissue tumor excisions surgery often causes complex three-dimensional extremity defects, which can be accompanied by large surface soft tissue defect, dead space, disruption joint capsule and/or extensor apparatus of the knee, and are challenging to repair precisely and efficiently. One-stage reconstruction of soft tissue defect and lost extensor mechanism in the knee region could provide a reasonable functional outcome.21 In the present series, six patients companied with disruption of joint capsular or extensor mechanism of the knee. The ALTP flap with partial fascia lata was performed on two cases to restore the joint capsule of the knee and simultaneous repair soft tissue defect. However, we also found that it is difficultly to use this approach to cover very large soft tissue defect, because the fascia lata was not completely separated from the skin paddle, and not facilitated to precisely inset in the wound. To overcome those disadvantages, vascularized fascia lata flap combination with free perforator flap was designed to cover the large soft tissue defect, restore extensors apparatus of the knee, and achieve the primary closure of donor site as well. In this case, a contralateral double skin paddles ALTP flap and bilateral superior lateral genicular artery perforator (SLGAP) flap was obtained to cover the soft tissue defect. The vescularized fascia lata flap was harvested to repair the patella tendon. This method provided sufficient soft tissue and double-vascularised layers for the reconstruction of large surface soft tissue defect and restoring the extensor mechanism of the knee at a single stage.
There are several extensor apparatus reconstruction procedure also have been reported in the literature before, such as a gastrocnemius transposition flap22, quadriceps advancement23,24 and tendon graft25. However, multiple operative procedures were required for those methods. Recently, chimeric flap has become one of the most popular procedures for reconstruction of three-dimensional defects because of its more degree freedom and flexible design.17,26−28 Chimeric MSAP flap have been reported as a valuable option for the reconstruction of composite and three-dimensional knee defects,29 However, the problems of donor-site morbidity and inability to repair very large defects at one-stage remain. 30 According to our experience, both TDAP chimeric flap and ALTP chimeric flap were reliable option for the reconstruction of complex tissue defect in the knee region, those flaps can provide a large skin area and enough muscle volume. 28
Selection of appropriate recipient vessels is essential for successful free flap transfer in the knee region. The size, shape, location and depth of soft tissue defect will affect the normal anatomy of the region and will drive the surgeon to different options according to the quality of the available vessels. Park et al31 recommended that the medial genicular artery (MGA) was an excellent alternative because of its proximity to the knee and its reliability, versatility and suitable caliber. Hong and koshima32 have presented a reliable approach which can use the perforator vessels as a recipient vessel for free flap transfer in the knee region, but the perforators are not always reliable in caliber and location. According to our experience, the vascular near the knee should be considered as the first choice for free flap transfer. If vessels near the recipient site were damage and microsurgical anastomosis must be performed outside of the zone of injury, The LCFA, PTA or ATA may be available to choose. In this present series cases, 43.75% arterial anastomoses were performed distal to the knee (PTA or ATA), 50% around the knee (SMGA or MSA), and 6.25% proximal to the knee (LCFA).