Spinal Probing: A New Diagnostic Technique for Back Pain
In this procedure, the patient remains awake and is administered with a local anesthetic. A small incision is made and a cannula (tube) is inserted. A probe is inserted into the cannula and down to the disc indicated in the preliminary diagnosis under X-ray guidance.
The disc wall is gently probed to provoke the initial pain symptoms. This could take anywhere from 10 to 15 minutes. This can cause slight discomfort for the patient if the disc wall is inflamed.
If the results are inconclusive, an adjacent disc may be investigated to further explore the cause of the symptoms.
What is Spinal Probing?
Spinal Probing is a modern minimally invasive diagnostic procedure used to maximize the accuracy of a diagnosis.
How is Spinal Probing Performed?
During a spinal probing test, the patient is under light sedation. Under fluoroscopic guidance, the physician introduces a cannula (tube) into the target foraminal entrance. A blunt spinal probe (explorative medical device) is inserted through the cannula to reproduce pain by gentle probing. During the procedure, the cannula is repositioned to different locations but it always remains in the foraminal entrance. The foraminal contents, anterior facet margins, and posterior disc annular tissues are all probed (explored). During a spinal probing test, the patient is awake and is able to report his or her pain response. Each pain generator (source of pain) identified and the patient’s response to the probing is recorded.
Patients who have been benefited from this pioneering test include those with:
While discography is effective for the diagnosis of pain originating in the spinal disc, it is ineffective for diagnosis of pain from other sources. It has been found that many pain generators are located in the intervertebral foramen, such as bone spurs (osteophytes), scar tissues, inflamed tissues, and facet joint hypertrophy. Traditional imaging studies such as CT, MRI, and myelography are not very effective either in identifying pain generators located in the foraminal area. With the use of a spinal probe, however, diagnosis of pain in the foraminal area is becoming much easier.
Discography has been the subject of much controversy and is generally reserved for identification of target levels for spinal fusion. discography alone elicited the predominant presenting symptom in only 50% of cases, but this may be because 38% of study subjects were suffering with non-compressive radiculopathy. Such patients are found at endoscopy to have highly irritated nerves that are sensitive to light touch and may suffer significant symptoms in the absence of positive discographic provocation tests.
Spinal probing alone identified the source of the predominant presenting symptom in an additional 42% of subjects. However, used alone, spinal probing would have been unable to identify the index level in 8% of cases. These patients had central protrusions that were too medial for spinal probing to access but were amenable to discography. This is confirmed by a significant difference in the outcome of endoscopic laser foraminoplasty in patients whose pain source was identified by discography alone compared to those whose pain source was identified by discography and spinal probing, which reflects the presence of more medial pathology that is less likely to produce a positive probing result and is also less adequately addressed by endoscopic laser foraminoplasty.
When combined, spinal probing and discography were able to localize the source of the predominant presenting symptoms in 100% of cases, 98.6% of which were confirmed by endoscopy. Failure to confirm the remaining 1.4% of pain sources may be attributable to gentle tissue handling. These results suggest that discography is a valuable supplement to spinal probing to maximize diagnostic sensitivity.
In this study, the sensitivity of discography and spinal probing at identifying the spinal level responsible for the predominant signs and symptoms of back pain was calculated at over 99% when assessed by either immediate endoscopy or by early post-operative clinical outcome. The fact that this was not a placebo effect was confirmed by the low revision rate at the 2-year review. This high sensitivity may be due in part to appropriate selection of patients to undergo the investigation and to the exclusion of patients with concordant symptoms at multiple levels for further investigation – but both of these factors should also apply to clinical practise.
It has been demonstrated that MRI cannot be relied upon to accurately select the appropriate spinal level for intervention. At over 99%, the sensitivity of discography and spinal probing is much higher than the reported sensitivity of MRI-determined high intensity zones, at 27%.33 However, unlike MRI, discography and spinal probing is an invasive technique, however minimally.
The most significant risk associated with discography is infection, which can be reduced by the use of an introducer sleeve and separate internal needle and by prophylactic antibiotic cover.
In conclusion, discography and spinal probing offers a highly sensitive system for identifying the index level in patients with either compressive radiculopathy or non-compressive radiculopathy. It directs the surgeon to the causal level by concordant feedback with encouraging accuracy where the response from the concordant level is clearly distinguishable from adjacent levels. Addressing the target level is attended by a low revision rate at 2 years. Encouraging early post-operative clinical results attest to the validity and efficacy of this method of investigation and warrant further study in a randomized, controlled clinical trial.