The Functional Anaesthetic Discogram: Description of a Novel Diagnostic Technique and Report of 3 Cases

Kambin's triangle: definition and new classification schema

Kambin's triangle is an anatomical corridor used to access critical structures in a variety of spinal procedures. It is considered a safe space because it is devoid of vascular and neural structures of importance. Nonetheless, there is currently significant variation in the literature regarding the exact dimensions and anatomical borders of Kambin's triangle. This confusion was originally caused by leaving the superior articular process (SAP) unassigned in the description of the working triangle, despite Kambin identifying that structure in his original report. The SAP is the most relevant structure to consider when accessing the transforaminal corridor. Leaving the SAP unassigned has led to an open-handed application of the term "Kambin's triangle." That single eponym currently has two potential meanings, one meaning for endoscopic surgeons working through a corridor in the intact spine and a second meaning for surgeons accessing the disc space after a complete or partial facetectomy. Nevertheless, an anatomical corridor should have one consistent definition to clearly communicate techniques and use of instrumentation performed through that space. As such, the authors propose a new surgically relevant classification of this corridor. Assigning the SAP a border requires adding another dimension to the triangle, thereby transforming it into a prism. The term "Kambin's prism" indicates the assignment of a border to all relevant anatomical structures, allowing for a uniform definition of the 3D space. From there, the classification scheme considers the expansion of the corridor and the extent of bone removal, with a particular focus on the SAP.

Provocative lumbar discography versus functional anesthetic discography: a comparison of the results of two different diagnostic techniques in 52 patients with chronic low back pain

BACKGROUND CONTEXT

There is mounting evidence that the currently available techniques for the diagnosis of discogenic low back pain are insufficiently accurate-this may explain some of the variability in outcomes of surgery for this important clinical problem. New diagnostic methods are needed to address this diagnostic issue; improvements here may do as much to improve overall patient outcomes as improvements in surgical treatment methods.

PURPOSE

To compare the results of standard pressure-controlled provocative discography (PD) to those of the functional anesthetic discogram (FAD) in a series of patients presenting with chronic low back pain and considering surgical treatment.

STUDY DESIGN

Prospective clinical series in an academic spinal surgical practice.

PATIENT SAMPLE

Fifty-two patients presenting with chronic low back pain; mean age 45 years (range, 24-70 years); 28 women, 24 men; and 25% in workman's compensation program.

OUTCOME MEASURES

Oswestry, visual analog scale for back pain, distress and risk assessment method psychometric analysis, demographic data, magnetic resonance imaging scan of lumbar spine. During provocative discogram: pressurization at pain, pain level, and concordancy. During FAD: position or activity used to elicit typical pain, baseline pain level before injection, during injection, at 5, 10, and 20 minutes after the injection, and substance injected.

METHODS

Standard pressure-controlled PD was performed, followed by (in positive cases or in patients with clinical features and imaging studies felt to be highly suggestive of symptomatic disc degeneration) the FAD test-an assessment of the response to injection of a low dose of local anesthetic into the disc during a position productive of the patient's typical pain.

RESULTS

Discordant results of the two tests were noted in 46% of the patients in the series. Of them, 26% of patients with positive PD had negative findings on the FAD test; 16% had positive findings at a single level only, whereas the provocative discogram had been positive at two or more levels; 4% had new positive findings on the FAD test.

CONCLUSIONS

We have presented the results of a new diagnostic technique in 52 patients with chronic low back pain presumed discogenic in origin that was designed to help differentiate between symptomatic and asymptomatic disc degeneration. The findings of the test differed from those of standard pressure-controlled PD in 46% of the cases reported on here. Further studies are needed to demonstrate the clinical utility of the test.