Usefulness of discography, discoblock and a new mechanical method for identifying a painful segment/disc

We previously described a procedure for eliciting deep spatial discrimination of individual segments in the healthy lumbar spine of normal subjects: the percutaneous mechanical provocation (PMP) test. Our goal was to devise a method for accurate identification of the spinal level of pathology in chronic low back pain (CLBP). In the present study, we validated the PMP test, using a subgroup of CLBP patients with isthmic spondylolisthesis (IS). Because there is clinical consensus that IS back pain originates in the slipped segment/disc, the level of pathology can be directly compared to the result of the PMP test. The test is agnostic with respect to the underlying pathological mechanism, and therefore might be useful in identifying the involved segment(s) irrespective of the painful structure.

In 37 patients with confirmed IS (slippage 3-15mm), we compared sensitivity between the PMP test, the widely used provocative discography test and the discoblock test.

The PMP test reliably identified the slip level in patients with IS, with sensitivity of 92%. Accepting the slipped disc as the origin of pain in IS, the sensitivity of the provocative discography and discoblock tests were 49% and 35%, respectively: i.e., too low to be contributive in clinical practice.

The PMP test reliably identified the origin of localized pain in IS as the slip level, but should be used with care in CLBP patients in selecting discogenic pain patients for fusion surgery, since the specificity of the test is not known and it may be positive for any origin of localized pain.