CPT Category III codes are not referred to the AMA-Specialty RVS Update Committee (RUC) for valuation because no relative value units (RVUs) are assigned to these codes. Payment for these services or procedures is based on the policies of payers and not on a yearly fee schedule.
In general, these codes are archived after five years if the code has not been accepted for placement in the Category I section of the CPT codebook, unless demonstrated that a Category III code is still needed. These codes will not be reused.
http://www.ama-assn.org/resources/doc/cpt/cptcat3codes.pdf
https://www.bcbskc.com/Public/Uploa..._Lumbar_Decompression_for_Spinal_Stenosis.pdf
Here excert of commercial carrier's medical policy for the procedure
Summary
Posterior decompression for lumbar spinal stenosis has been evolving towards increasingly minimally invasive procedures in an attempt to minimize post-operative morbidity and spinal instability. In general, the literature comparing surgical procedures is limited. The evidence available suggests that less invasive surgical decompression may reduce perioperative morbidity without impairing long-term outcomes when performed in appropriately selected patients. In contrast to surgical decompression, the
mild® procedure is a percutaneous decompressive procedure performed solely under fluoroscopic guidance (e.g., without endoscopic or microscopic visualization of the work area). This procedure is indicated for central stenosis only, without the capability of addressing nerve root compression or disc herniation, should it be required. Due to the unknown impact of these limitations on health outcomes, randomized controlled studies in appropriate patients are needed to compare this novel procedure with the established alternatives. Although studies have been initiated, no evidence is available at this time
to evaluate the efficacy of image-guided percutaneous lumbar decompression. Therefore, this procedure is considered investigational.
Additionally from this link
http://www.painphysicianjournal.com/2010/january/2010;13;35-41.pdf
Conclusions: This review demonstrates the acute safety of the mild procedure with no
report of significant or unusual patient complications. To establish complication frequency
and longer-term safety profile associated with the treatment, additional studies are
currently being conducted. Survey data on file at Vertos Medical, Inc.