1. A coordinate mapping system comprising: a positioning instrument for controlled delivery of a device to a target site within a bone, comprising a main body and a rail extending from the main body, the rail including a series of indicia corresponding to predetermined grid lines, the instrument further providing a series of device portals configured to guide the device into a subchondral region of the bone for treatment at the target site, the series of device portals provided on the rail for access to the target site; and a template configured to overlay an image or the bone having a defect at the target site, the template including a predefined grid for determining a set of coordinates to locate the target site using the positioning instrument, wherein at least one of the coordinates represents an interval of a radial grid line and at least one of the coordinates represents an angular component for mapping to the target site within the bone.