Clark A. Rosen
Vocal fold injection for global augmentation of the vocal fold is a successful way to treat glottal closure insufficiency . Autologous fat is an excellent material for this type of vocal fold injection. This chapter discusses the patient selection, clinical aspects, and post-operative management issues related to vocal fold lipoin-jection.
The distinct advantage of vocal fold lipoinjection is the use of an autologous material that is usually readily available. Furthermore, autologous fat has been found to have excellent biomechanical properties associated with vocal fold vibration when placed into the larynx . No discernable stiffness or alteration of normal vibratory function has been seen by this author nor reported in the literature following lipoinjection of the vocal folds [3-8].
There are several important advantages of vocal fold injection vs laryngeal framework surgery; these include the ease of bilateral vocal fold injection (when clinically necessary) and the opportunity for direct visualization of the pathologic defect of the vocal fold(s) (paresis, atrophy, or scar) immediately before and during the vocal fold injection procedure. Laryngeal framework surgery, in contrast, involves augmenting the vocal fold from an "outside to inside" approach relying on fiberoptic imaging and perceptual feedback results to judge an endpoint . A bilateral procedure requires a longer neck incision and more surgical dissection. Some surgeons are not willing to perform bilateral medialization laryngoplasty which results in suboptimal voice outcomes. This is common in patients with a unilateral vocal fold paralysis and contralateral age-related vocal fold atrophy who are treated only with a unilateral medialization laryngoplasty and experience partial improvement in their voice quality due to the failure to address the glottal insufficiency component from the atrophy.
Disadvantages of vocal fold lipoinjection include variable survival of the transplanted autologous fat and the consequent need for over-injection [10, 11]. Given that lipoinjection will involve some loss of the transplanted material in the first 6-week period, a slight to moderate overinjection of the vocal fold is required. This poses a problem clinically if there is an already borderline airway. Furthermore, overinjection can be problematic due to the resulting temporary dysphonia and delayed voice improvement for as long as 4-6 weeks postoperatively.
Another consideration is the labor required and method used to harvest the fat, a disadvantage of lipoinjection compared with an injection using an "off-the-shelf " product. Typically, fat harvest in preparation for lipoinjection is performed as an open removal of subcutaneous fat or liposuction.
Vocal fold lipoinjection is best used to treat insufficiency of glottal closure when the gap is small to medium in size. This is often the case in patients with vocal fold paralysis, paresis, atrophy, and scar. For patients with glottal gaps greater than -4 mm, as well as patients with a shortened or "slack" vocal fold sometimes associated with vocal fold paralysis, lipoinjection is not an optimal treatment method. In the vocal fold paralysis patient, the contralateral vocal fold should be carefully observed pre-operatively to identify (a) patients who have relatively poor abduction of their contralateral vocal fold, and (b) patients with loss of bulk of the contralateral vocal fold. The first group of patients are a relative contraindication for VFL due to the temporary reduction of the airway associated with the overinjection required. In contrast, patients with contralateral loss of vocal fold bulk are excellent candidates for bilateral vocal fold lipoinjection. Patients that have significant concerns regarding open neck surgery and/or foreign substance implantation are also excellent candidates for autologous vocal fold augmentation.
The amount of subcutaneous fat available for harvest should be evaluated prior to VFL. For patients who have an extremely small amount of subcutaneous fat, liposuction is not a reasonable harvest technique, and in fact, even open fat harvest can be problematic. In this specific patient group, subcutaneous open fat harvest will most likely be more involved and may have an increased complication rate than in patients with generous subcutaneous fat deposits. Furthermore, in the extremely lean patient, surgical harvest of subcutaneous fat may not yield adequate amounts of fat for successful VFL.
Given that lipoinjection involves a "deep" or "lateral" vocal fold injection, patients selected should be those with a "global" glottal insufficiency and not those with small, focal lamina propria defects. This contraindication does not apply to patients with a substantive "cookie cutter defect" of the vocal fold following cancer excision. These patients can in fact be quite successfully treated with VFL when performed carefully and properly .
Fat harvest for lipoinjection can be done either via an open, subcutaneous fat harvest or via liposuction. Liposuction is the preferred technique because it is expedient, less invasive and provides perfect-sized injection material. For patients with only modest amounts of subcutaneous fat, open harvest is recommended. The most reasonable location for open harvest is in the infra-umbilical region or through a pre-existing abdominal scar. The former area of the body typically has a plentiful amount of material and an incision immediately underneath the umbilicus can be easily hidden. Fat harvest can be done under local or general anesthesia.
The patient's abdomen is prepped and draped in a sterile fashion. If not performed under a general anesthetic, local injection is done as for a regional block (and in the proposed incision site for hemostasis). A curvilinear incision is made at the junction of the umbilicus and the infra-umbilical region, approximately from 4 o'clock to 8 o'clock position. Subcutaneous elevation of the dermis proceeds in an inferior direction, releasing the subcutaneous fat off the subdermal plane. The fat is sharply dissected out with cold steel instruments, taking care to not violate the skin above or the peritoneum below. Hemostasis can be obtained with electric cautery as needed. Tacking sutures are placed from the deeper aspect of the wound to the subdermal base to minimize the dead space and the cutaneous incision is closed with absorbable sutures. The harvested fat is then carefully cut into small pieces with scissors, approximately 1x2x1 mm. This aspect of the procedure is time-consuming and laborious but important. If the fat graft material is not properly prepared, it will not flow smoothly through the injection needle. These small pieces of fat are then handled in a similar fashion as the liposuction harvested material, described below.
Liposuction should be done using a large-bore, low-pressure liposuction technique. Small-gauge and high-pressure liposuction devices should be avoided to minimize the trauma to the fat during the harvest process. The author uses a 4.6-mm single-hole liposuction cannula (Tulip Products, San Diego, Calif.).
Liposuction from the subcutaneous abdominal space can be done under general or local anesthesia; the latter requires local anesthesia to be injected in the area of the intended liposuction. After the abdominal skin is prepped
Fat Harvest and draped in a sterile fashion, a small skin incision (~ 5 mm) is made in the right upper quadrant of the abdomen. The liposuction cannula is passed through the skin and into the subcutaneous space. Negative pressure is applied from the liposuction device and the cannula is then moved through the subcutaneous plane in a controlled but expedient fashion (Fig. 8.1.1). This results in adequate amounts of fat for vocal fold lipoinjection after approximately 30-90 s of vigorous movement of the liposuction cannula in the subcutaneous plane.
Fat harvested by any method is covered with free fatty acids,blood, andserum (Fig. 8.1.2) . The free fatty acids are from ruptured lipocytes and induce an intense inflammatory response if not removed. The fat must be carefully and
atraumatically cleaned prior to lipoinjection to maximize graft survival. Fat is placed in a sterile funnel that is lined by strips of Merocel (Medtronics/Xomed, Jacksonville, Fla.). Suction tubing is applied to the down spout of the funnel and 2 liter of saline is used to rinse and irrigate blood and fatty acids from the surface of the harvested fat (Fig. 8.1.3) The fat is soaked in a small dish with 100 units of regular insulin for 5 min. The insulin is theorized to stabilize the lipocyte cell membranes and thus improve cell survival during the transplantation process. To remove excessive moisture, the fat is then placed on a dry Merocel sponge and partially dried by the air. It can then be loaded into the injection device in preparation for a VFL. Figure 8.1.4 demonstrates the "cleaned" fat af
ter passing through the injection device. Note the absence of a "greasy" sheen (free fatty acids) and minimal moisture.
done to the extent that at immediate completion of the procedure the membranous vocal folds will be in complete approximation.
Lipoinjection of the vocal folds may be performed through an 18- or 19-G needle. Using any smaller needle is likely to disrupt the injection material and compromise graft survival. Lipoinjection is designed for a deep/lateral vocal fold injection and can be done either via an endoscopically guided direct laryngoscopy approach or suspension microlaryngoscopy approach [1, 14]. Given the viscous nature of the fat, a pressurized injection device such as a Brünings syringe (Storz, St. Louis, Mo.) or a lipoinjection device designed by Instrumentarium (Montreal, Canada) is required. The optimal location for the initial site for lipoinjection is at the junction of a horizontal line drawn through the tip of the vocal process and the superior arcuate line. The approximate depth of this injection should be 5 ± 2 mm. The angle of the needle should be directed in a slightly posterior and lateral direction to ensure that the injection is not placed inferior to the vocal fold nor in a too superficial/medial a plane. The ideal location for deep vocal fold injection is identified by careful observation of the infra-glottic aspect of the vocal fold for an initial infra-glottic "bulge" or appearance of augmentation in the immediate infra-glottic region at the start of the injection. As additional fat is injected into the vocal fold, the vocal fold augmentation will proceed in a cephalad fashion. If this does not occur spontaneously, the needle should be slightly adjusted to find the proper location. The surgeon should perform approximately 30% overinjection of the vocal fold to compensate for expected fat loss in the transplantation process. (Figs. 8.1.5,8.1.6) Often, a second injection site is placed in the mid-membranous vocal fold at the level of the superior arcuate line. Care should be taken to avoid injection anterior to this point because excessive augmentation of the anterior half of the vocal fold typically results in a strained voice quality. Often bilateral VFL in patients with mobile vocal folds will be
Patients are placed on strict voice rest for 6 days following VFL. Routine use of prophylactic antibiotics is not indicated. Both intravenous (peri-operative) and oral steroids (post-operative) are typically used to minimize peri-operative swelling. The patient should be counseled to avoid throat clearing if possible and beware of any signs ofbreathing difficulties.
Duration of Benefit
Vocal fold lipoinjection involves over injection because of partial loss of some of the transplanted material over the 4-6 weeks following the procedure. Although there are no studies comparing different practices, survival of the graft material is thought to be optimized with strict voice rest for the 6 days following surgery, proper harvesting in as non-traumatic a fashion as possible, and proper handling of the fat following harvest. Patients should be warned that their voice may remain dysphonic or actually deteriorate while the swelling and over correction of the vocal fold slowly resolves for as long as 6 weeks following lipoinjection; however, patients typically report that their voice dramatically improves 3-4 weeks following VFL. The degree and nature of the vocal fold augmentation that exists at 6weeks following lipoinjection has been found by the author to be permanent. If a patient has a significant voice improvement prior to 6 weeks or no immediate post-operative dysphonia, then it is likely that injection will be inadequate to yield adequate medialization in the long term.
Recent review of the vocal fold lipoinjection results at the University of Pittsburgh Voice Center found 27 patients available for long-term follow-up (mean 11.3 months, range 3.028.9 months). Twelve of these patients had vocal fold atrophy, 14 had vocal fold paralysis, and 1 patient had both unilateral recurrent laryngeal nerve paresis and bilateral superior laryngeal nerve paralysis. Eleven of the 27 patients were male. Five of the patients in the study group required further laryngeal surgery, as follows: 1 patient experienced a lipogranuloma which was excised 2 months following lipoinjection; 1 patient required medialization laryngoplasty (to further enhance glottic closure following vocal fold lipoinjection); and 3 patients required repeat vocal fold lipoinjection, due to under-augmentation by the initial VFL.
Pre- and post-operative VHI results showed statistically significant difference (p=o.oooi). Pre-operative mean VHI was 69.5 and postoperative was 38.2 with a mean follow up of 12 months. Mean flow rate differences pre- and post-VFL also showed statistically significant improvement from a pre-operative mean flow rate of 490 ml/s to a post-operative result of 283 ml/s (p=o.oi).
Complications of Lipoinjection of tlie 1^/oc«=il Folds
Approximately 1-3% of lipoinjection patients may experience some airway compromise, given that a moderate amount of overinjection of the vocal fold is required and that significant post-operative edema or infection can occur following injection. Airway difficulty following lipoinjection should be managed using the same principles as in other upper airway difficulties, specifically, careful observation, steroids (i.v. or oral) and mechanical intervention for re-establishment of the airway, if needed. Clinicians who are concerned about the patient's airway following bilateral lipoinjection may elect to stage the injections. This allows the surgeon to maximally overinject the vocal fold and minimize the risk of airway difficulties in the post-operative period.
Under-medialization can occur in approximately 5-10% of patients undergoing lipoinjection. This problem most likely represents an inadequate amount of fat material survival and/or an insufficient amount of fat injected into the vocal fold, but can also occur from suboptimal injection location. This can be corrected with a repeat lipoinjection, vocal fold injection with an alternative material, or laryngeal framework surgery.
In rare instances, an excessive amount of fat following lipoinjection can persist, resulting in persistent post-operative dysphonia. When this is suspected, the patient should be observed for the first 2 or 3 months. This allows localized edema to resolve. If after several months it is clear that persistent post-operative dysphonia is due to overinjection, then injected material can be removed via a lateral cordotomy using the principles of phonomicrosurgery. This is done through an incision through the superior surface of the vocal fold at approximately the superior arcuate line. Dissection proceeds down to the deeper aspect of the vocal fold until the injected fat material is identified and removed with cup forceps until an appropriate amount of vocal fold augmentation is still present. In the present author's experience, this has happened only once in over 300 cases.
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