Vikas V Patel, University of Colorado, Denver, USA recently presented his findings on the predictive value of discography at the North American Spine Society annual meeting in Orlando, USA.
In their study, positive discography was highly predictive of clinical outcomes following artificial disc replacement but was not as successful in a small group of patients that received discograms but did not meet the criteria for positive discography.
Patel noted there have been mixed results on the predictive value of discography for clinical success after surgical treatment. While some studies have reported an 88–89% predictive value, a more recent study used clinical outcomes after fusion as a “gold standard” test and found discography to have only a 27–43% predictive value at the two years postoperative time point. Patel chose artificial disc replacement instead of fusion as the treatment as it treats the disc only, leaving the posterior elements untouched and mobile.
The patients in Patel’s study were enrolled in the FDA study of Pro-Disc L artificial disc replacement and were randomised to artificial disc replacement and underwent discography at a single institution. Positive discography was defined as a concordant pain response of ≥7/10, corresponding abnormal morphology on CT discography and at least one control disc with a pain response of <4/10.
They used two levels of criteria to evaluate clinical success that required a combination of improvements in visual analog score and Oswestry disability index and accounted for net changes, per cent changes and raw scores. High clinical success was defined as visual analog score being one of the following: VAS score <3.5, improvement of ≥2 points or per cent improvement of ≥41.4%, and ODI being one of the following: ODI score <31.3, improvement of ≥18.8 points or per cent improvement of ≥36.8%. A minimum clinically important difference was defined as VAS being one of the following: improvement of ≥2 points or per cent improvement of ≥30% and ODI being one of the following: improvement of ≥ 10 points or per cent improvement of ≥ 30%.
Of the 33 artificial disc replacement patients that had pre-operative discograms, 23 met their criteria for positive discography: 16 females, seven males, average age 42.2 (25–59), L5–S1 (15), L4–L5 (7), L3–L4 (1). Ten patients received discograms that did not meet their criteria for positive discography: one female, nine males, average age 40.1 (23–59), L5–S1 (7), L4–L5 (2), L3–L4 (1). At 24 months postoperatively, 18 (78%) positive discography patients achieved high clinical successful and 21 (91%) reached the criteria for a minimum clinically important change. In contrast, 6 of 10 (60%) non-criteria patients reached high clinical success and 7 (70%) met the minimum clinically important change criteria.
These results suggest that adhering to a strict protocol for “positive” discography can more effectively predict positive outcomes. Given that fusion is associated with variable outcomes, a loss in mobility, and the potential for adjacent segment disease, Patel concluded that artificial disc replacement may represent the best treatment currently available for assessing the predictive value of discography.