The lateral access approach is frequently utilized to deliver interbody fusion cages to the lumbar spine. In comparison to conventional anterior or posterior approaches to the lumbar spine, the lateral approach is thought to minimize posterior and/or anterior tissue damage as well as reduce surgery time, associated blood loss, and infection risk.
When multi-level access to the spine is provided through a single minimal access port, the insertion trajectory to the superior and inferior levels is not parallel to those levels. In addition, direct lateral access parallel to the L4/5 and L5/S1 levels is prevented by the presence of the iliac crest.
Accordingly, the angled trajectory required for lateral access to these lower levels requires the cages to be implanted at a “malpositioned” angle that prevents balanced loading across the vertebral endplates and spine. See FIG. 1. This “malpositioned” access, associated endplate damage and device placement can initiate subsidence and spinal instability.
Current spreader and shaver technology includes varying paddle shapes and cutting geometries with rigid drive shafts. US Patent Publication No. 2008-00445966 discloses a chisel cutting guide for excising a portion of a vertebral body.
Conventional dilation systems used in intervertebral fusion procedures are typically rigid and non-steerable. Accordingly, they require a line of sight insertion towards the target disc.
US Patent Publication No. US 2007-0225815 (Annulex) discloses a curved stylet for steering within a disc space Annulex does not disclose an assembly comprising a curved guide wire and a flexible dilator tube.