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[Fusion criteria for cages as vertebral body replacement in thoracolumbar fractures]
K J Schnake1, T Görler, F Kandziora
1Zentrum für Wirbelsäulenchirurgie und Neurotraumatologie, BG Unfallklinik Frankfurt am Main, Friedberger Landstraße 430, 60389, Frankfurt am Main, Deutschland, klaus.schnake@bgu-frankfurt.de.
Background:
No commonly accepted criteria to evaluate bony incorporation of cages as vertebral body replacement in thoracolumbar fractures exist. The goal of this study was a thorough radiological evaluation of the fusion process in posterior-anterior stabilized fractures.
Patients And Methods:
In this study 35 patients were evaluated radiologically including computed tomography (CT) scanning and bone mineral density measurement inside the cages. Correction loss, cage subsidence and tilting, bone growth in and around the cages as well as bone mineral density were assessed. Fusion grading was assessed with defined criteria (i.e. bridging bone, bone growth through the cage, stability in functional X-rays and no radiolucent lines).
Results:
After 12 months minor subsidence and tilting of the cages had caused significant correction loss of the basal plate angle of 2.4° on average. Of the patients 20 (57%) fulfilled the criteria for complete or incomplete fusion and 5 (14%) showed no signs of bony fusion. Bone mineral density measurements were unreliable due to metallic artefacts.
Conclusions:
The advocated criteria allow accurate assessment of bony incorporation of cages. Bony incorporation can be detected in and around the cages over time; however, only 57% of patients showed signs of bony fusion after 1 year.