True AP imaging during lumbar medial branch radiofrequency neurotomy: Interobserver reliability

True segmental imaging, in AP and lateral planes, is necessary to accurately place an RF cannula contiguous with the targeted medial branch and achieve effective pain relief with lumbar radiofrequency neurotomy (LMBRFN). True lateral imaging and its interobserver reliability during LMBRFN have been described. A complementary true AP imaging technique has recently been described, but its interobserver reliability has yet to be studied.

This study aims to determine the interobserver reliability of the recently described true AP imaging technique for LMBRFN.

After obtaining IRB exemption, true and untrue AP images were collected from consecutive LMBRFN procedures performed during the normal course of the primary author's (PW) practice. A 100-slide testing set was formulated. Each slide contained a true and an untrue counterpart AP image depicting the same single-level RF cannula placement targeting an L3 or L4 medial branch or an L5 dorsal ramus. After slide randomization, a Google Forms test was created to capture observer responses. Two sets of observers were used to represent novice (DB,KG) and experienced (MF,ER) observers. Each observer independently reviewed the testing slide set, recording a total of 300 responses for the three binary decisions on each slide: which image was true, which corrective maneuver (oblique or tilt) was required to make the untrue image a true image, and finally, which was the direction of the appropriate corrective maneuver (right or left oblique/cranial or caudal tilt). Each observer's test was compared to the answer key established by two non-observer authors (PW,TM). Interobserver agreement for both the novice and experienced groups was determined for each of the three decisions using the Kappa score calculation. Individual observer performance was also determined.

For the determination of the true image, the novice group's interobserver agreement (Kappa score) was 0.98 (0.94,1.0); the experienced group's was 0.96 (0.91,1.0). For the oblique or tilt corrective maneuver decision, the novice group's Kappa was 1.0; the experienced group's was 0.98 (0.94,1.0). For the direction of the oblique corrective maneuver, the novice group's Kappa was 1.0; the experienced group's was 0.88 (0.75,1.0). For the direction of the tilt corrective maneuver, the novice group's Kappa was 0.96 (0.88,1.0); the experienced group's was 0.92 (0.81,1.0). Individual observer performance data on the total of 300 decisions ranged from 98% (an experienced observer) to 100% (a novice observer).

Obtaining true AP imaging for LMBRFN by the newly described technique is supported by significant interobserver reliability that ranges from substantial to perfect. This AP imaging technique, when combined with true lateral imaging, provides true lumbar segmental imaging. True segmental imaging is recommended not only for LMBRFN but for other commonly performed lumbar spine procedures.