Instruments and methods for creating an operative corridor to the spine are described. The instruments include, for example, a retractor assembly with at least one retractor blade that may be releasably coupled to a bone anchors via a hoop shim. The hoop shim includes a shim portion that may slidably engage the retractor blade and a hoop portion extending from the shim portion that includes an aperture that receives the bone anchor. The hoop portion may have an unlocked configuration that allows passage of the bone anchor and a locked position which prevents passage of the bone anchor to releasably couple the hoop shim to the bone anchor. The hoop shim may be configured to couple to the bone anchor such that the hoop shim may angulate relative to the bone anchor.