Osseodensification: A Novel Approach to Surgical Hardware Fixation
Christopher D. Lopez, B.A.1, Adham Alifarag, B.A.2, Nick Tovar, Ph.D.2, J. Rodrigo Diaz-Siso, M.D.3, Eduardo D. Rodriguez, M.D., D.D.S.3, Paulo G. Coelho, D.D.S., Ph.D.2.
1Icahn School of Medicine at Mount Sinai, New York, NY, USA, 2New York University College of Dentistry, New York, NY, USA, 3New York University School of Medicine, New York, NY, USA.
PURPOSE: Surgical hardware mechanical stability is essential for complex bone reconstruction. Traditional approaches to hardware fixation attempt to maximize stability by interlocking fixation hardware with subtractive drilling of bone. We investigated the effect of additive drilling (osseodensification drilling) in bone hardware fixation from biological and biomechanical perspectives.
METHODS: Four fixation devices were installed on C3 vertebral bodies of 12 sheep; each measuring 4mm diameter x 10mm length. The two left-sided vertebral body devices were implanted using subtractive drilling while the two right-sided devices were implanted using osseodensification. At t=3 and t=6 weeks post-implantation, the animals were euthanized and the spine segments retrieved. Identical hardware installation was subsequently performed for C2 and C4, providing fixtures at t=0. Hardware competence was measured using biomechanical testing of pullout strength, and quality/degree of new bone formation and remodeling was assessed histologically. Statistical analysis included multiple Wilcoxon matched paired tests (α=0.05).
RESULTS: At t=0, significantly higher (p=0.031 for both C2 and C4) pullout values were observed for osseodensification. Osseodensification also presented significantly higher pullout values at 3 and 6 weeks in vivo (p=0.027). Over time, regular drilling pullout strength increased by ~39.5%, and osseodensification by ~44.2% Histology demonstrated higher degrees of bone surrounding fixtures placed at osseodensification sites relative to regular drilling. Osseodensification bone chips acted as nucleating surfaces for new bone formation.
CONCLUSION: Osseodensification increased the degree of biomechanical fixation at time of installation and maintained it as time elapsed in vivo. Histology depicted that osseodensification was not detrimental to bone healing around fixtures.
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