By Diana Swift
WebMD Health News
March 21, 2017
A single intradiscal glucocorticoid injection reduced discopathy-related low back pain at 1 month; however, the effect decreased over time. At 12 months, neither pain intensity nor other health-related outcomes differed between patients who did or did not receive an injection, researchers report in an article published online March 20 in the Annals of Internal Medicine.
"The efficacy of [glucocorticoid intradiscal injection] as a possible treatment for chronic [low back pain] associated with active discopathy is questionable, given the lack of long-term benefit," write Christelle Nguyen, MD, PhD, assistant professor of physical medicine and rehabilitation at Paris Descartes University in France, and colleagues.
Dr Nguyen and associates conducted a prospective, parallel-group, double-blind, randomized controlled study between 2009 and 2014 at three French tertiary-care centers with expertise in spine medicine.
The 135 participants all had low back pain of at least 3 months' duration (mean, 6.3 years) and Modic 1 changes with vertebral endplate subchondral bone edema on magnetic resonance imaging. Participants had failed conservative treatments, and all had a mean pain intensity of more than 40 (median, 70 [40 - 80]) on an 11-point numerical rating scale ranging in 10-point increments from 0 (no pain) to 100 (maximum pain). The patients were 60.7% women, and their median age was 46.0 years.
The researchers randomly assigned 67 patients to receive a single intradiscal glucocorticoid injection (25 mg prednisolone) during discography, and 68 patients to discography alone. Patients were assessed at 1, 3, 6, and 12 months.
The study's primary outcome was the proportion of patients reporting pain intensity of less than 40 in the previous 48 hours at 1 month, a cutoff point that corresponds to the patient-acceptable level of symptoms. The main secondary endpoints included pain intensity and active discopathy at 12 months, as well as spine-specific activity limitations, health-related quality of life, anxiety/depression, employment status, and analgesic/nonsteroidal anti-inflammatory drug use at 1 and 12 months.
At 1 month, 36 (55.4%) patients in the injection group and 21 (33.3%) in the control group reported reduced pain intensity, for an absolute risk difference of 22.1 percentage points (95% confidence interval [CI], 5.5 - 38.7; P = .009).
However, starting at 3 months, pain scores increased in the injection group and were higher than in the control group, an outcome the authors said may be a result of the rebound effect of corticosteroids.
On sensitivity analysis, the mean reduction in pain intensity from baseline to 1 month was -32.5 (CI, -38.2 to -26.8) in the treatment group vs -17.5 (CI, -23.3 to -11.7) in controls, for an absolute difference of -15.0 (CI, -22.9 to -7.1; P < .001).
By 12 months, the two groups did not differ in pain intensity, nor did they differ in most secondary outcomes at both 1 and 12 months.
In terms of safety, both groups had a similar rate of adverse events: 97.0% in the injection group and 94.1% in controls. A total of 78 serious adverse events occurred overall, including 25 hospitalizations for usual care of low back pain in the treatment group and 29 in the control group. There were no cases of infectious spondylodiscitis or intervertebral disc calcifications.
By way of limitations, the authors noted that the study population had severe symptoms and poor psychosocial status, which night have affected treatment outcome. "Some researchers have suggested that [glucocorticoid intradiscal injection] should be offered only to patients with [chronic low back pain] with few confounding factors," they write.
In a related editorial commentary, David J. Kennedy, MD, a clinical associate professor of orthopedic surgery at Stanford University in Redwood City, California, commended the French researchers for making progress in the study of lower back pain, as their trial addressed a specific treatment for a specific cause of lower back pain, which is a setting where much research has been done in heterogeneous patients receiving heterogeneous treatments. Nevertheless, he writes, "more granularity is required to determine which treatment is right for which patients."
In terms of study design, Dr Kennedy said even more rigorous inclusion criteria might have produced different results. He also noted that the lack of benefit at 12 months might be a result of disease heterogeneity in these chronic pain sufferers. "[S]ome participants may have had more than 1 cause of pain," he writes. "In some patients, chronic low back pain is not due solely to a musculoskeletal pathology."
According to Dr Kennedy, although glucocorticoid intradiscal injection may be an option for short-term relief in patients who have acute pain episodes plus Modic 1 changes, glucocorticoid injection is not a durable treatment for chronic pain. "The question then arises about the utility of using an invasive treatment for short term relief in the setting of an acute condition with a favorable natural history or for an acute flare of a chronic condition," he writes.
This study was funded by a research grant from the French Ministry of Health. The authors and editorialist disclosed no conflicts of interest.