Coarse Surface Microcavities Permit Bone Ingrowth and Improve Implant Osseointegration

Existing research has shown that implant surface topography influences osseointegration. It was already known that micron and submicron roughness can enhance bone contact. However, no prior work had resolved how adding larger surface features might affect integration. That uncertainty drove this investigation into coarse microcavities. Prior studies focused on uniform surface textures, but this gap motivated exploring multilevel topographies. The role of cavity size and distribution in bone ingrowth remains unclear. This paper addresses the unanswered question of whether uneven cavities improve anchorage. The goal is to determine if such features can enhance implant stability in vivo.

The study aimed to assess how adding coarse microcavities to existing implant surfaces affects osseointegration. Researchers focused on bone ingrowth and implant stability in a rabbit model. The specific problem was whether uneven cavities could improve anchorage compared to smooth surfaces. The motivation was to design implants with better bone integration. The authors tested if cavities influence bone-to-implant contact and removal torque. They also examined if cavity placement affects bone volume density. The study sought to determine if cavities encourage tissue infiltration. The findings may inform future implant surface design strategies.

The study used confocal interferometry to measure surface roughness. Electron microscopy and X-ray analysis characterized surface features. Contact angle and X-ray photoelectron spectroscopy assessed surface energy and chemistry. Fifteen rabbits received implants with and without cavities in their femoral condyles. Implants were left to integrate for 2 and 8 weeks. Bone-to-implant contact, bone volume density, and removal torque were quantified. Histological and scanning electron microscopy confirmed tissue infiltration. The cavities measured 48.4 ± 16.8 μm in diameter and 37.8 ± 36.5 μm in depth.

Cavity-rich implants showed higher bone-to-implant contact at 8 weeks (P = .002). Removal torque was also greater at 8 weeks (P = .059). Bone volume density was higher at both 2 and 8 weeks (P = .031 and P = .078). Cavities covered 5.9% ± 1.1% of the implant surface. Surface chemistry and energy remained unchanged with cavities. Histological analysis confirmed bone inside the cavities. Scanning electron microscopy showed tissue infiltration. These findings suggest that uneven cavities promote bone anchorage.

The authors propose that unevenly distributed cavities allow bone ingrowth and improve implant stability. Their findings suggest that cavity-rich surfaces increase bone contact and torque. They note that cavities do not alter surface chemistry or energy. The results encourage designing implants with multilevel topographies. The study supports the use of uneven cavities to enhance osseointegration. The authors suggest that such surfaces may improve implant-based regeneration. The findings are specific to the rabbit model and 2- and 8-week timepoints. The study does not claim that cavities are essential for integration.