drilling a plurality of vertebral laminae of vertebrae in a patient spine to provide access holes to each of a corresponding plurality of interspinous ligaments, wherein the drilling is performed percutaneously, and wherein the drilling includes, for each of the plurality of vertebral laminae, creating an access hole that terminates at a ventral portion of the respective interspinous ligament at a location posterior of the corresponding ligamentum flavum, without drilling through the ligamentum flavum;

cutting at least a ventral portion of each of the corresponding plurality of interspinous ligaments; and

delivering collagenase clostridium histolyticum to the each of the corresponding plurality of interspinous ligaments via the access holes.