2017-18 HSC Section 4 Green Book

Treatment strategies for frontal sinus anterior table fractures and contour deformities

technique can be technically easier than fracture reduc- tion because the exposure and repair are easier with nonmobile bony fragments and the repair does not have to happen in the acute setting. 22,25 In such instances, it is important to restore the ideal forehead contour and pro- vide support for the overlying soft tissue. While a frontal cranioplasty with osteotomies is certainly an option in delayed frontal sinus contour deformity reconstruction, contour deformity camouflaging is more attractive of an option because of its significantly less morbidity, blood loss, and operative time and superior aesthetic outcome for cosmetic problems. A variety of reconstructive materials have been applied for frontal bone contour deformities, including autologous bone, methyl methacrylate, hydroxyapatite cement (HAC), titanium mesh, porous polyethylene implant, and polyether ether ketone (PEEK). 25 e 32 The ideal allograft material should have the following characteristics 30 : Biocompatibility Factors that influence the choice of allograft material include the reconstructive approach, size of the defect, patient comorbidities, and surgeon preference. 26 Large contour deformities generally require an open approach for access and graft placement, whereas smaller contour deformities may be amenable to endoscopy-assisted ap- proaches. The major limitation factor in an endoscopy- assisted approach is the size of its incisions, which dic- tates the size of implant that may be introduced. Autologous bone grafts provide robust resistance to infection and decreased likelihood of graft extrusion, and they are best suited for large defects. Common donor sources include the calvarium, iliac crest, and tibia. In adults, split calvarial grafts can be used to cover defects up to 25 cm 2 . However, bone grafts are difficult to contour, exhibit variable resorption over time, and are associated with donor-site morbidity. Bone graft placement requires an open approach for graft harvest (split calvarial graft) and graft placement. 26 Widely applied in orthopedic surgery and early frontal contour deformity repair, methyl methacrylate use has declined in recent years due to several disadvantages. Methyl methacrylate forms a capsule that is prone to infection. It also undergoes an exothermic reaction, reaching 110 C, during hardening that can cause thermal injury to surrounding tissue. 29,33 As a result, methyl meth- acrylate has been largely replaced by HAC. HAC powder, which is composed of tetra-calcium phos- phate and dicalcium phosphate anhydrous, becomes an easily malleable paste when hydrated. The paste is then used to contour the frontal defect, where it hardens within 20 min without generating heat. Because of its ease of use, mold- ability, and osteoconductive property, HAC has been favored for filling in frontal contour deformities. Over time, HAC will gradually be absorbed and replaced by native bone. 30,31 Both methyl methacrylate and HAC require an open approach for application. These materials are not suitable for the repair of full-thickness anterior table defects. In Moldability to fit any defect Stable shape in size over time Tissue incorporation

addition, HAC may be used as an adjunct at the time of open reduction internal fixation to camouflage contour deformities. 32 Titanium mesh is useful for contouring large frontal de- fects. This material is readily available, inert, nonabsorb- able, rigid, and malleable. Computer-assisted patient- specific titanium implants (PSI) permit an ever-increasing precision. 26 Placement and fixation of the mesh generally requires an open approach, although there has been one reported case of an endoscopically placed titanium mesh, with one-point screw fixation through a stab incision, for contouring of a small frontal depression. 28 Porous polyethylene is a synthetic biocompatible struc- ture that permits tissue ingrowth. The solid form of porous polyethylene requires carving and trimming to achieve its desired shape. 22 Alternatively, PSIs generated from three- dimensional models fashioned out of thin-slice (1-mm) CT scans are now available, obviating the need for intra- operative carving. 34 The use of PSI reduces the need for intraoperative manipulation, thereby reducing operative time. 35 These implants are suitable for defects of any size. Porous polyethylene implants can be placed via an open 27 or endoscopic approach, depending on the size of the implant. 25 The porous polyethylene implant is placed in a subperisoteal plane and secured with a screw. The risk of infection and implant extrusion remains a concern with the usage of this material. 26 Used similarly to porous poly- ethylene, PEEK is a polyaromatic semicrystalline polymer implant with excellent strength, durability, and biocom- patibility that is manufactured as a single- or multiple- component PSI placed via an open approach. 34 Injectable fillers have gained significant popularity for soft tissue augmentation and volume expansion in the face. Collagen, hyaluronic acid, poly- L -lactic acid, and fat in- jectables are generally well tolerated with mild and tran- sient side effects. Injectable fillers seem to be well suited for contour camouflage of frontal deformities. However, historically, the glabellar region has been the most common site to experience injection necrosis, secondary to vascular compromise from external vascular compression, vessel occlusion with filler material, or direct vessel injury. 36 Furthermore, permanent unilateral vision loss has been described in relation to glabellar filler injection, attributed to retrograde arterial embolism of filler material from the peripheral extraorbital branches of the ophthalmic artery, causing retinal vascular occlusion and blindness. 37 Although well tolerated in other regions of the face, filler injection in the glabellar or frontal region carries a rare but significant risk. Therefore, use of injectable fillers in this region is discouraged at this time. Previously failed frontal cranioplasties or individuals with previously irradiated or infected surgical sites may require vascularized bone flaps for reconstruction of frontal defects. The fibula is the most common free vascular donor site. Vascularized free flaps are readily integrated into the surrounding bone and are particularly resistant to infection. 26,38,39 Broyles et al. 39 described the use of the fibular free flap to create a bony frontal bandeau. However, these flaps are difficult to contour, and they have significant donor-site morbidity and long operative times. 26,38,39

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