Derby R, Eek B, Mooney V

Intradiscal thermal modulation (ITM) is a procedure to heat the intervertebral disc for the purpose of relieving discogenic pain. We reported our early results at the 1996 ISIS meeting and below report the longer and more detailed follow-up of these same patients.

Methods and Materials: From 3/96 through 12/96 we enrolled our first twenty-one consecutive patients undergoing ITM procedures into a prospective outcome study. We enrolled thirteen males and eight females with an average age of 43 years and a range of 24 years to 60 years. There were 5 patients with worker compensation claims and four patients who had ongoing litigation. All patients had chronic low back pain with or without referred buttock and leg pain. The duration of their pain ranged from 1 year, 5 months to 20 years, six month, with an average duration of 6 years, 6 months. All patients had either gradually increasing or stable daily and constant low back pain that fluctuated in intensity according to the degree and duration of spinal loading. In addition 44% of the patients experienced referred leg pain that was less than their back pain. All patients had undergone extensive conservative treatment including medication, physical therapy, trigger pain injections, posterior column sclerosing injections and epidural injections. All such treatments had either failed or provided only temporary or incomplete improvement.

Prior to IMT all patients underwent pressure-controlled discography to determine the number of symptomatic discs, the location of annular tears, and to categorize the sensitivity of the disc annulus to pressurization. Prior to and after ITM the patients pain status was assessed by changes in the Roland-Morris questionnaire, VA pain scale, and an abbreviated NASS pain questionnaire. At follow-up patients were also asked to score their satisfaction with the procedure results using a four point ordinal scale and to score their satisfaction in regards to their overall degree of pain on a four point ordinal scale.

The first author in an outpatient-imaging center using C-Arm image intensification performed the ITM procedure. A twenty gauge Sluijter needle by Radionics was placed into one or more intervertebral lumbar discs using a lateral approach using either a single or double needle technique. The active tip was placed from the most symptomatic side and lesions were made with the tip approximately 5 mm across the midline and with the tip at or 1 to 2 mm from the midline on the side of insertion. In cases of bilateral pain, two needles on opposite sides were used. Needle positions varied but an attempt was made to place the exposed needle tip as far posterior in the annulus as technically and safely possible. A radio-frequency generator by Radionics was used to heat the adjacent tissue to a temperature of 80 degrees Centigrade for duration of four minutes. A minimum of two lesions and a maximum of four lesions were made at one to two different needle insertion sites. During the procedure the power settings, location, duration, and pain referral location, pain intensity, and pain concordancy was recorded.

Results: At follow-up, all twenty-one patients were contacted by phone by a research assistant and all patients completed the follow-up questionnaires. The follow-up interval from the time of the first ITM procedure was an average of 14 months with a range of 9 to 18 months. There were no complications. The average duration of flare-up in symptoms was 9 days and ranged from 1 day to 21 days. The average number of disc levels burned was 2.33 and ranged from a single level to a maximum of 5 levels. Patients with multilevel painful discs first had their worst levels treated and returned one to two months to have the less symptomatic discs done. Seventeen (81%) of the patients requested repeat burns to be performed on the same or adjacent discs because of incomplete pain relief. Of the patients who requested repeat burns, the average number of repeat sessions was 1.4 with a range of 1 to 4.

The mean VA pain score prior to ITM was 7.9 and the mean Roland & Morris point score was 15.52. At follow-up the mean VA pain score was 5.9 and the mean Roland & Morris point score was 12.9. Fourteen per cent of the patients felt that they were much better, 52% felt that they were better, and 33.3% felt that they were the same. No patients felt that they were worse or much worse. Forty seven per cent of the patients felt that there overall activity was improved and all felt the improvement was the result of having the ITM procedure. Fifty seven per cent of the patients felt the treatment met all their expectations, 33.3 % felt they improved but not as much as they had hoped but would undergo the procedure again for the same outcome, and two stated they were the same and would not undergo the procedure again. Despite their improvement, only 10% of the patients were neutral or satisfied with their current overall level of pain. Prior to the procedure 16 patients were working and at follow-up 17 patients were working.

Conclusions: Intradiscal heating for the purpose of reducing chronic low back pain appears promising. Although patients are not cured and repeat procedures are often necessary, the patient satisfaction index is 90% and aside from a flare of symptoms lasting one to three weeks, the procedure appears safe. Further studies are needed to better define proper needle placement and heating pramaters. Finally, better methods to deliver and measure the heat transfer to the outer annulus are needed and are currently undergoing clinical trials.

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