Hydroxyapatite paste (BoneSource) used as an onlay implant for supraorbital and malar augmentation

This study was designed to evaluate hydroxyapatite paste (BoneSource; Leibinger Corp., Dallas, TX) as an alloplastic implant for supraorbital and malar augmentation. Ten male Sprague-Dawley rats had cylindrical onlay implants made of the hydroxyapatite cement placed above their left orbits on the supraorbital rim. Size-matched Medpor implants were placed similarly on the right side. To test the utility of this new material in the midface, hydroxyapatite paste and Medpor implants were also placed in the right malar regions of a different set of rats. The implants were left in situ for 6 months and examined for evidence of bone ingrowth, infection, migration, resorption, and detrimental effects on the surrounding tissue. All hydroxyapatite cement implants provided excellent soft tissue projection and demonstrated steadfast adherence to the adjacent bone. The surface of the hydroxyapatite implant in contact with the native bone demonstrated evidence of native bony ingrowth into approximately 12% of the implant. There was no evidence of implant migration or gross infection. There was no bony resorption below the hydroxyapatite paste, but four of the Medpor implants showed evidence of this in the underlying bone. Only one negative aspect to the use of hydroxyapatite cement paste as an onlay implant was identified. Two of the supraorbital and one of the malar hydroxyapatite implants had approximately 20 to 25% volume loss during the experimental period (P = 0.05). Overall, the vast majority of the implants retained their original form. We concluded that hydroxyapatite paste may possibly be used to effectively augment bone in the supraorbital and malar regions. Its biocompatibility, excellent bony adherence, and tendency to be replaced by natural bone may make it suitable for the aesthetic patient. The possible resorptive aspects of the material need to be evaluated further.