Framework exposure is the greatest risk and challenge faced by surgeons who choose to use ear framework materials to complete total auricle reconstruction. The incidence of alloplastic material exposure in ear reconstruction ranged from 7.3 to 13.24%, but in almost all cases, exposure was actually caused by an unstable tissue covering the implant and not the implant itself. Careful attention on some technical issues during the operation and special nursing care after the operation may be helpful to prevent framework exposure. The common causes of framework exposure are as follows: ① The soft tissue that wraps the framework is too small. The size of the superficial temporal fascia and the transplanted skin graft above the framework is too small or the tension between them is too large. When this occurs, poor local blood supply and ischemic necrosis of the fascia and skin may occur in the early stage. This will also lead to the exposure of the material at the highest point of the helix and other convex parts due to fascia and skin contraction in the late stage. Therefore, while preparing fascia flap and skin graft, the size should be large enough to make the contact between superficial temporal fascia and framework tension-free. The preparation of the fascia flap should not only include the superficial temporal fascia but also include the deep temporal fascia. If necessary, it can include the galea aponeurotica to ensure sufficient blood supply to the fascia flap . Regardless of use of the fascial flap or free skin graft, there should be no tension when covering the framework, especially at the earlobe junction. The thickness of the skin differs between the two parts, which makes it easy to cause skin contracture and cracking. ② Collision and extrusion by force. The skin covered on the surface of the ear framework is transplanted from the abdomen or thigh root. It has poor collision resistance and repair ability. Collision, scratching, and extrusion will lead to skin damage and exposure or fracture of the framework. The exposure of the framework after 6 months of the operation was mostly related to external force collision or long-term compression. We suggest that patients sleep with soft pillows or earmuffs and avoid collision sports in daily life. We found that the most common site for framework exposure is the helix. Therefore, for children with a thin fascia flap, a long strip of skull periosteum can be prepared to wrap around the helix framework for strengthening and protection. ③ Postoperative infection and hematoma. Early framework exposure is usually related to infection and hematoma, and the wound usually expands rapidly. In this group of patients, the size of framework exposure caused by infection increased from 0.5 cm × 1.0 cm to 3 cm × 3 cm only in 1 week. During the first 3 months after operation, the incision and skin graft area were still in the healing stage. There may be focal necrosis or infection in the skin flap and fascia flap, which needs close observation. Once hematoma is detected, hematoma and blood clot should be removed promptly, and drainage should be placed to avoid secondary infection. For the wider and thicker blood scab, necrosis and infection under the scab may occur, and a skin defect will be formed after removal, resulting in framework exposure. The scab should be excised in the early stage, and the wound should be treated with some anti-inflammatory and epidermal growth factor gel, such as benzalkonium chloride disinfection or gentamicin flushing. ④ Improper stitching and packing. If the alignment of the incision suture is poor or too sparse, the epidermis can easily crack after removing the suture. While packing the wound, an excessive pressure is induced by the dressing and bandage, which can affect the blood supply to the fascia flap and skin flap, resulting in local necrosis of the skin flap or the fascia flap and framework exposure. Therefore, when dressing the wound, the triangular fossa, boat fossa, and concha cavity should be filled with small strips of gauze to ensure the appearance of the fine structure of the auricle, and the helix should be wrapped with two layers of Vaseline gauze for protection. The total reconstructed auricle should be packed with an antibiotic gauze with proper pressure. Generally, the packing should be removed after 12–14 days. ⑤ The end edges of the framework are too sharp. The flexibility of the ear material is worse than that of autologous cartilage, and all edges should be trimmed smoothly, especially the ends of the framework and the crus of the helix. If these two parts are exposed, they are mostly related to the sharp end of the material. A small burr on the surface of the material can cause rupture of the tissue flap and lead to framework exposure. For treating earlobe junction, the residual earlobe should be separated to form a capsule, and the end of the framework should be fixed in the residual earlobe soft tissue as much as possible. ⑥ The ear framework is not stably fixed. During the operation, the ear framework needs to be accurately fixed on the periosteum of the lateral cranial wall to form an ideal cranioauricular angle. Stable framework placement is crucial to bear the postoperative flap contraction and maintain a good shape. It can also avoid the fracture of the framework due to the movement or loosening of implants by force in the later stage. To strengthen the stability of the implants, a sharp knife can be used to punch holes at the upper, middle, and lower parts of the ear base implants, and the framework can be sutured through these holes and fixed stably on the side wall of the skull. At present, 2-piece porous implants (Medpor/Su-Por) are prepared from a thin helical rim and thick ear base that are melted together to create the final form of the implant. An additional material is soldered between the two pieces to strengthen the implant; however, when a joint is made between two pieces, there is a weak point that can become crack due to stress over time . In 2015, an American surgeon Dr. Lewin created a 3D single intricately shaped piece from porous polyethylene; the base of the 3D ear implant was flat, which can fit well on the skull surface and thus greatly improve the stability of the framework. This implant was reported to reduce the risk of implant fracture to 3%.
Choosing the appropriate tissue flap to repair the damaged framework is very important for the recovery of postoperative appearance and to avoid the occurrence of other complications. At present, the common tissue flaps that can be used for repairing ear framework exposure or fracture include the deep temporal fascia flap, temporal muscle flap, mastoid fascia flap, and local skin flap [8,9,10].
In the present patient group, the superficial temporal fascia flap was used, and the deep temporal fascia was removed in some patients. This makes it more difficult for us to choose the appropriate repair methods. The temporal muscle flap is a pedicled island flap. The tissue flap contains branches of the superficial and deep temporal arteries and veins, with good blood supply and high survival rate . Clinically, it is commonly used to repair soft tissue defects in the orbital region, skull base, and temporomandibular joint [12,13,14]. The temporal muscle is adjacent to the auricle and has sufficient tissue to apply; thus, it can be used as an ideal method to repair the exposure of auricle framework . In the present study, the defect of the upper part of the helix was mostly repaired with a tissue flap containing the deep temporal fascia and a part of temporal muscle, which could reduce the risk of secondary exposure due to fascia flap contracture. In this group, the deep temporal fascia flap was chosen for repair by one child at the first time, and the highest point of the helix was exposed again 6 months later due to wearing spectacles for a long time. The temporal muscle flap was used to repair at the second time. The child has been followed up for 6 months, and the shape of the auricle has recovered well. When preparing the temporal muscle flap, the incision can be directly made upward from the exposed and damaged helix skin surface to the temporal area or directly cut from the previous scalp incision to expose the temporal muscle. One should be careful to separate the fascia flap to avoid damaging the superficial temporal artery and vein branches. When the fascia flap needs to be folded back, careful attention should be given to protect the pedicle by avoiding pressure, especially while moving through the skin tunnel to repair the wound.
For patients with framework exposure in the middle and lower part of the auricle, the mastoid fascia flap can be selected for repair. In 1991, by autopsying the mastoid region, Park found that the mastoid fascia was divided into the superficial and deep layers. The superficial layer, that is, the continuation of the galea aponeurotica, was supplied by the posterior auricular artery, the posterior branch of the superficial temporal artery, and the occipital artery. The deep layer is also called the innominate fascia . Subsequently, Park used the mastoid fascial flap to complete the reconstruction of microtia with framework for the first time. The anterior half of the auricle was wrapped with a skin flap, and the posterior half was covered with a mastoid fascial flap and free skin graft, which reduced the incidence of framework exposure . The maximum preparation size of the mastoid fascia flap can reach 8 × 6 cm, and the mastoid region has a rich vascular network, which makes it easy for the flap to survive. Thus, it can adequately repair a large area of framework exposure, especially in the lower two-thirds of the auricle [18, 19]. When preparing the mastoid fascia flap, the incision can extend from the defect area parallel to the mastoid region, the lower part can be separated close to the surface of sternocleidomastoid muscle, and the upper part can be separated close to the surface of skull.
The application of a local flap is limited due to the lack of definite blood supply and limited supply area. In this patient group, only one defect near the lower part of the helix was repaired by an axial local flap in the mastoid region. There are only a few reports in the literature, such as the use of a preauricular flap to repair the exposure of cartilage framework at the triangular fossa by Jeremie .