Intravertebral neotrabecularization as an expression of focal load transfer by a keel-design lumbar total disc arthroplasty

The aim of this study is to direct attention to the specific load transfer characteristics of keel-design total disc arthroplasty (TDA) implants that may be underreported. A variety of implants for lumbar TDA are available on the market. One of the main differences between the design types of lumbar TDA implants is whether they use a keel or small spikes/ridges in order to achieve primary stability. The consequences of such design features on load transfer have not been adequately discussed. We report and discuss a case in which new intravertebral bone trabecula have appeared after double-level implantation of a keel-based TDA. We think that the mid- and long-term follow-up radiographs of patients after TDA with keel-design implants should be examined for the presence or absence of such changes. Should our case turn out to be not a singular occurrence, this might have an impact on the design of future TDA implants.