The Molteno M-Sphere

Purpose: To analyze a mammalian hydroxyapatite (HA) implant known as the Mo lteno M-Sphere, recently approved by the Food and Drug Administration of th e United States. Methods: The authors examined the implant macroscopically. with chemical an alysis (x-ray powder diffraction, x-ray fluorescence spectrophotometry), an d microscopically with scanning electron microscopy. Animal implantation of six Molteno M-Spheres was carried out in six adult male New Zealand albino rabbits. Implant vascularization was evaluated by means of magnetic resona nce imaging and histopathologic sectioning. Results: The hi-Sphere was found to have multiple interconnected pores thro ughout with an average pore size of 300 mu m to 600 mu m This implant was v ery lightweight (0.31 g) and fragile. It was made up of pure HA. Magnetic r esonance imaging studies showed implant enhancement to its center by 4 week s after implantation. Histopathologically, fibrovascularization occurred un iformly throughout the 4, 8, and 12-week rabbit implants. Conclusions: The M-Sphere is an alternative type of HA implant that recentl y has been reintroduced into the United States for use after enucleation, e visceration, or as a secondary implant. It has multiple interconnected pore s allowing central fibrovascularization as early as 4 weeks in a rabbit mod el. Its light weight and fine trabecular framework, however, are associated with increased implant fragility when compared with other available HA imp lants (BioEye and FCI3 synthetic HA). The implant requires careful handling because routine handling may damage the implant. The implant is currently approved by the United States Food and Drug Administration.