Characterizing an angle of cannula insertion for Lumbar Medial Branch Radiofrequency Neurotomy: A retrospective observational study.

Objective: Evidence characterizing a starting angle of radiofrequency (RF) cannula insertion during radiofrequency neurotomy is lacking. Using computerized tomography (CT), this retrospective observational study attempts to establish a starting angle for RF cannula placement parallel to the transverse process (TP) at the junction of the superior articular process (SAP) near the targeted medial branch.

Methods: This retrospective observational study utilized lumbar spine CT scans performed on adult cancer patients from January 2016 to May 2021 ​at a single center. No significant lumbar pathology was present on the included CT studies. For each patient, medial branches were assumed to lie at the junction of the right and left TP and SAP at each lumbar level. The angle of insertion from each segment's "squared" superior end plate needed for RF cannula placement parallel to the surface of the TP next to the SAP was calculated.

Results: Images obtained from fifty patients were analyzed. Mean angle of insertion for L1 was 20.15 ​± ​1.82°, L2 was 20.95 ​± ​2.07°, L3 was 25.54 ​± ​1.76°, L4 was 31.01 ​± ​1.83°, and L5 was 40.74 ​± ​1.86°.

Conclusion: This study demonstrates variations in inserting angle for RF cannula placement parallel to the surface of the transverse process at each lumbar level. To our knowledge, there are no studies in the current literature that have described an entry angle for RF cannula positioning parallel to lumbar medial branches using CT images.