To analyze a mammalian hydroxyapatite (HA) implant known as the Molteno M-Sphere, recently approved by the Food and Drug Administration of the United States.
The authors examined the implant macroscopically, with chemical analysis (x-ray powder diffraction, x-ray fluorescence spectrophotometry), and 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 resonance imaging and histopathologic sectioning.
The M-Sphere was found to have multiple interconnected pores throughout with an average pore size of 300 μm to 600 μm. This implant was very lightweight (0.31 g) and fragile. It was made up of pure HA. Magnetic resonance imaging studies showed implant enhancement to its center by 4 weeks after implantation. Histopathologically, fibrovascularization occurred uniformly throughout the 4, 8, and 12-week rabbit implants.
The M-Sphere is an alternative type of HA implant that recently has been reintroduced into the United States for use after enucleation, evisceration, or as a secondary implant. It has multiple interconnected pores allowing central fibrovascularization as early as 4 weeks in a rabbit model. Its light weight and fine trabecular framework, however, are associated with increased implant fragility when compared with other available HA implants (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.
*Department of Ophthalmology, University of Ottawa Eye Institute, Ottawa, and Departments of †Pathology and ‡ Radiology, Ottawa Hospital General Site, University of Ottawa, Ottawa, Ontario, Canada; and the §Department of Ophthalmology, Vanderbilt University, Nashville, Tennessee, U.S.A.
Accepted March 22, 2000.
Address correspondence and reprint requests to Dr. David R. Jordan, Department of Ophthalmology, University of Ottawa Eye Institute, 104-340 McLeod Street, Ottawa, Ontario K2P 1A4, Canada.