Ronda Alexander, MD
When considering vocal fold augmentation, the lynchpin of success is finding the perfect material for your patient’s indication. For those patients who are either unwilling or unsuitable for operative thyroplasty, injection medialization is an important alternative. There exist a wide array of materials of different origins and effective durations. Whether artificial and permanent, like polytetrafluoroethylene (PTFE aka Teflon®), or autologous and transient, like adipose harvest, each substance has advantages, inadequacies and potential complications. The most recent addition to our armamentarium, Radiesse®, is no different in this sense.
This material has been in use since early this century and was approved by the FDA for use as a laryngeal implant in 2007.1 Subsequently, its manufacturer has engaged in a sweeping educational campaign to ensure that physicians are aware of the new indication. It is made of calcium hydroxyapatite (CaHA) – essentially equivalent to the mineral component of human bone. CaHA has been used for years as a block implant during Type I thyroplasty2 and is often carved to achieve the ideal effect within the larynx. The new twist is that Radiesse© is made up of of CaHA dust (25-46 micrometer-sized particles) suspended in a carrier gel made of carboxymethyl cellulose solution. This change makes it injectable. It was first marketed to Otolaryngologists to treat HIV-associated lipodystrophy then for aesthetic use as facial filler and finally as a bulking agent for the larynx.
CaHA has been demonstrated to provide the mass needed to medialize the vibratory margin of the vocal fold when it is placed deep to the thyroarytenoid muscle. It travels fairly easily through 20-gague needles but its viscosity becomes an issue with smaller needles. It is generally not immune-provocative and should evoke only a localized foreign body giant cell reaction when introduced into the deep structures of the larynx.3 While often casually spoken of as ‘permanent’, micronized CaHA has been shown to provide effective medialization and clinical improvement for 12-24 months. This makes it ideal for patients in whom recovery is not expected but who are not candidates for (or willing to have) general anesthesia for operative laryngoplasty. It does not, however, present a lasting solution to the problem beyond the 2-year time horizon.
Unfortunately, it does come with some cautions. First, location is critical when placing it in the vocal fold. It should never be injected within the vibratory apparatus of the vocal fold. It has been demonstrated to adversely affect vocal quality if inadvertently introduced into the submucosal plane or lamina propria.4 This can be treated with operative excision if the patient is sufficiently disturbed by the deterioration of the voice. Another potential pitfall comes to light when considering patients who undergo injection augmentation in the setting of malignancy. The site of injection can enhance on PET scans which are used commonly in the post-treatment monitoring of oncology patients.5 This should be borne in mind when choosing the injectable material for patients being treated or monitored for cancer.
As our options for laryngoplasty have expanded from open surgery to injections with various materials, it remains pivotal that clinicians carefully consider why the patient needs the procedure and have that drive the choice of material. While calcium hydroxyapatite is a welcome addition to our arsenal against glottal insufficiency, its appropriateness should be judged on a case-by-case basis.