Hydroxyapatite/collagen composite is a reliable material for malar augmentation (summary)
Authors:
Antonio D’Agostino, MD, Associate Professor, Lorenzo Trevisiol, MD, Associate
Professor, Vittorio Favero, MD, Clinical Assistant, Michael J. Gunson, DDS, MD,
Private practice, Federica Pedica, MD, Clinical Assistant, Pier Francesco Nocini, MD,
DDS, Professor, Chief, G. William Arnett, DDS, FACD, Private practice
TLDR AT THE END
Intro
Facial reconstruction and subsequently aesthetic facial surgery became a widely practiced necessity after the first world war. At the time, few alloplastic options were available, and osteotomies were the most common method of achieving a natural contour after all functional requirements were met. With recent advancements, osteotomies of the midface (Lefort II, Lefort III) have fallen out of favor Those methods foresee midfacial advancement, at times in conjunction with bone grafting and stabilization. Given the high surgical invasiveness of these procedures, the need for an extraoral approach (coronal subpalpebral), the technical difficulty in carrying them out and in controlling occlusal problems, they have fallen into disuse as far as traditional orthognathic surgery is concerned and are currently utilized only in cases of malformations in pediatric patients.
Silastic (silicone), medpor (porous polyethylene) is widely used, is easily positioned, does not need stabilization. However, it is associated with relatively high percentage of complications including infections, dislocations, formation of fibrous capsules, lack of integration, and resorption of native bone.
Medpor is widely used in trauma medicine to contour the face. Risks associated with this material are generally low (early and late onset infection, impossible to remove, the formation of pseudo-capsules and osseous integration failure)
Coral derived porous hydroxyapatite (HA) which is available in granule, and block form, is another material that is frequently used in maxillofacial surgery for procedures to augment the splanchnocranium. According to data in the literature, porous HA granules are stable over time and are osteoconductive (17, 18). The prosthesis requires, nevertheless, hypercorrection, and in some cases there may be problems linked to irregularities in facial symmetry; it also seems to be structurally incapable of withstanding functional load. Since porous HA granules are not preshaped or prepackaged for prosthetic use, it is less frequently used with respect to the others cited above.
Over a seven-year period (2005-2012), 430 patients (270 females and 160 males; mean age 28 years, range 18-45 years) underwent procedures using porous HA granules to augment the zygomatic region (a total of 860 prosthesis) to optimize facial aesthetics during orthognathic surgery. All of the procedures were carried out in one of two centers: the Arnett-Gunson Center for Corrective Jaw Surgery located in Santa Barbara, Calif. (USA) and the Unit of Dentistry and the Maxillofacial Surgery Unit of the University of Verona Medical Center in Verona (Italy). The treatment plan, which aimed to achieve functional and aesthetic improvement, proposed to enhance the zygomatic region of patients with inadequate cheekbone projection and/or facial asymmetry of the zygomatic arch.
Overall, the percent of complications was found to be relatively low (5.6%);more specifically 4.3% had contour irregularities and 1.3% had infection and extrusion of granules requiring an overcorrection of 15% of the required volume. Except for the cases of partial or complete resorption (5 = 0.64%), the imaging data collected at T1 demonstrated that the prosthesis maintained its granular structure and that the granules had not migrated to the surrounding soft tissues. The structure of the prosthesis resulted relatively radiotransparent when compared with the compact portion of the zygomatic bone. At time T2, the prosthesis seemed to adhere staunchly to the underlying zygomatic bone in all of the patients. The granular structure was still distinguishable, although it was less evident, and the partial radiotransparency had evolved into a radiopacity similar to that in the compact part of the native bone, making it impossible to distinguish the prosthesis-bone interface (Fig.
. That tendency continued, according to the imaging data available at T3, towards a progressive loss of definition of the granular architecture and an almost complete radiopacity and an apparent corticalization of the bone in contact with the prosthesis. The prosthesis-bone interface at time T3 appeared indistinguishable. Finally, the stability of HA appears to be linked to the material’s osteoconductive properties as it is gradually replaced by native bone tissue with a colonization gradient from the periosteum to the basal cortical bone, as demonstrated by the study’s histological findings which are in accordance with morpho-volumetric data described by Mendelsson and Grybauskas (18, 45).
Our radiologic findings confirm that the prosthetic material becomes modified over time; initially it is radiotransparent with a granular structure, but over time it shows increasing uniformity and radiopacity which
presupposes that the material will be resorbed and replaced over time by the cortical bone.In contrast with other biomaterials, HA seems to be characterized by a low rate of both early and late onset infections (0.2%). This finding has been confirmed by reports by various authors (17) and is in agreement with the hypothesis that porous HA has an antibacterial effect (46). Colonization of bone tissue, the fact that screws are not needed to fix the prosthesis, and a high degree of biocompatibility (47) contribute to limiting the occurence of postoperative and long term infectious phenomena. It should be remembered, in fact, that
with regard to both one-piece and segmental LeFort 1 osteotomies of the upper jaw, healing of the osteotomic site is almost never absolutely complete due to the long-term possibility of bacterial contamination through the nasal passages.The patients judged their perception of their facial contour post-op in the area augmented by the HA. On a 0 to 100% scale, the average judgment about the natural contour of the zygomatic profile was 85.83±22.22/100 (median 95.19). The average judgment about the symmetry of the final result was 85.68±23.00 (median 96.44). The average judgment about the implant’s natural feeling was 80.30±26.28/100 (median 92.10). The patients’ average general satisfaction with the final result was 84.41±23.96/100 (median 96.72).
The large number of patients included makes it one of the most extensive studies on this procedure found in the literature. In the light of what has been emerged in the study, porous HA seems to be a material with excellent biocompatibility and osteoconductivity. In fact, the low rate of complications found and the radiologic, histological, and molecular biology findings support this affirmation and are in agreement with the data of other studies outlined in the literature. It was found that porous HA prostheses for zygomatic augmentation led to long term, stable aesthetic results and, in fact, most of the patients expressed a high degree of satisfaction. These advantages are counterbalanced by the relatively long time needed to prepare the prostheses and the long learning curve involved in creating the subperiosteal pocket and a slight hypercorrection which seem to be necessary to address the short term volumetric reduction. To conclude, given the characteristics outlined here, porous HA granules with microfibrillar collagen seems to be an excellent choice when surgery to harmonize the zygomatic region and to correct facial asymmetry is being planned.
TLDR;
- ~6% complication rate found in literature (4.3% contour irregularities, 1.3% infection, migration, extrusion. Less than one percent instance of granular instability and migration. Infection rate was found to be even lower in this study due to antibacterial effect of HA (0.2%)
- Material is ineffective under functional load of any kind. I imagine this means your face becomes fragile.
- Patients were overall very satisfied with their aesthetic.
- Long term studies show the graft is replaced by native bone
- Lefort 1 never heals? (if someone could elaborate on this that would be appreciated)
If anyone wants to know any of the sources referenced above or any further information from the paper let me know.
