Fat Grafts

Fat grafting has gained popularity recently among plastic surgeons. It can be a useful adjunct to both reconstructive and cosmetic surgeons. Fat is commonly used in breast reconstruction to correct asymmetries and add volume, in facial rejuvenation as a permanent filler to add volume and restore youthful facial appearance, and in many other challenges such as scar management and body contouring procedures. The literature is replete with studies and reports about fat-grafting techniques and outcomes, and many of these present contradictory findings. This makes a choice of methods/practice confusing for one new to the field. In general, the goal of fat grafting is to achieve a predictable and reproducible outcome. Tissue fragments within the graft survive initially by diffusion, just as with a skin graft. Although relatively simple from a technical standpoint, fat grafting is actually a complex process when viewed in its entirety or from a process engineering perspective. It involves a number of steps, including donor-site preparation, tissue/graft harvest, tissue/graft washing and preparation, tissue/graft delivery, and graft/recipient site preparation and care. Each of these steps is associated with a large number of variables and options that may alter the final outcome of the procedure. For this reason, it is difficult to design and carry out well-controlled studies that will yield robust data.

Although the topic of fat grafting could cover an entire chapter itself, a few basic principles will be mentioned. First, logic would dictate that repeatable and predictable volume maintenance requires that the tissue/graft physiology be returned to normal physiological status as much as possible prior to grafting. ⁴ A large burden of free oil, for instance, can release fatty acids to the surrounding tissues and/or reduce pH, resulting in cell membrane damage. Ideally, the graft should have a known and reproducible aqueous fraction, as this is a volume that will be lost after grafting via resorption. If the graft has a large aqueous component, it will be easier to inject and will be associated with less shear force, but will require relatively more overcorrection to maintain volume. If the graft is particularly concentrated, it will be harder to push through a cannula and result in more cellular damage from shear stress. To minimize cell trauma and damage, it makes sense to use larger bore syringes (i.e., catheter tip syringe vs. Luer lock syringe) and larger bore cannulae for graft delivery. A standard Luer syringe has an internal diameter of 1.8 mm at the tip. The use of syringes, needles, and cannulae with a diameter of 2.5 to 3.0 mm is likely to result in less shear force and cell damage when all other variables are held constant. Further discussion of the many facets and considerations surrounding fat grafting is beyond the scope of this chapter, but the reader is referred to a number of reviews on the subject. ^{5 , 6 , 7 , 8}

Cartilage Grafts

Cartilage grafts are often helpful during nasal, ear, or eyelid reconstruction or during rhinoplasty. The three most common sites for cartilage harvest include costal rib cartilage, conchal bowl of the ear, and nasal septum. Cartilage can be harvested with or without perichondrium. The characteristics of the cartilage are usually maintained at the recipient site, and will usually maintain the natural shape of the cartilage. Nasal septal and auricular cartilage are most often used in nasal surgery, as spreader grafts, or tip reconstruction/augmentation. Costal cartilage is most often used for nasal dorsum and external ear reconstruction. Cartilage donor sites are generally inconspicuous and the material itself is indispensable for achieving the desired results.

Bone Grafts

Bone grafts are common and are often used for reconstruction of the mandible, long bones of extremities, and the facial skeleton (Fig. 5‑2). Autogenous bone grafts or allografts can be used according to surgeon’s preference and the type and extent of the defect. For example, in a patient who needs reconstruction of a large mandibular defect with a history of prior radiation, a free fibula graft is a far superior option as compared to an allograft or a nonvascularized bone graft. In general, allografts have less osteoinductive and osteoconductive properties than autogenous bone grafts but have the distinct advantage of absence of donor-site morbidity. Four general types of autologous bone grafts are described: cancellous grafts, cortical grafts, cortico-cancellous nonvascular grafts, and free vascularized grafts. Cancellous grafts are typically used for reconstruction of the alveolar cleft, nasal reconstruction, or in hand reconstruction after removal of a bone cyst. They tend to vascularize better than cortical grafts but require longer time to gain structural stability and strength. The main mechanism for new bone formation is osteoconduction. Cortical bone grafts take longer to vascularize but may provide better initial stability. They have more limited osteoinductive and osteoconductive properties. Fixation of bone grafts has been shown to reduce graft resorption when grafts are placed under mobile tissues. Some of the common donor sites include calvarium, iliac crest, fibula, rib, and distal radius. ³

Tendon Grafts

Tendon grafting is useful in the management of various upper extremity injuries and defects. It can be done acutely in one stage if the wound is clean with adequate soft-tissue coverage and tendon donor sites are available outside of the zone of injury. If this is not possible, reconstruction can be performed in two stages. In the first stage, silicone rods can be placed to allow for tendon bed preparation, and in the second stage these can be removed and replaced with an appropriate graft. The palmaris longus and plantaris tendons are ideal tendon grafts as they are expendable and easily accessible. It is important to remember that about 20% of patients lack either a palmaris longus or plantaris tendons.

Nerve Grafts

Nerve grafts are commonly used in hand trauma, upper extremity, and facial reconstruction and facial reanimation. Nerve grafts can be allografts or autografts depending on surgeon’s preference. When autograft is used, one has to consider denervation somewhere and sensory deficit. Sural nerve is by far the most common nerve utilized for grafting. It courses along the posterolateral ankle and is easily accessible. It is important to inform the patient that grafted nerve is not immediately healed and it may take months until the final result is achieved. Nerve graft essentially serves as a conduit for axonal growth, which typically begins at 2 weeks after grafting and continues 1 mm/day until the target is reached.

Technique of Flap Transfer

Cutaneous flaps can be classified according to the technique used for flap transfer and the distance between donor and recipient site.

Rotational flaps are semicircular and design and rotate about a pivot axis. The donor site can be closed primarily or skin grafted. To facilitate closure, a burrows triangle or a back cut can be made. If a back cut is made, one has to make sure not to undermine the blood supply to the flap.

Transposition flaps are rotated (laterally) about a pivot point into an immediately adjacent defect. Because the effective length of the flap becomes shorter the farther the flap is rotated, the flap must be designed longer than the defect to be covered, otherwise a back cut may be necessary. The flap donor site can be closed primarily, with a skin graft or another flap such as a bilobed flap.

Rhomboid flap is another type of transposition flap. Limberg flap is commonly used to reconstruct cutaneous defects. It is designed with 60- and 120-degree angles opposing each other. Four different types of flaps can be designed around angles of 60 degrees with recruitment of skin from the area of most laxity (Fig. 5‑3). ¹⁰