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The Spine Blog

Friday, March 2, 2018

Annular defect size and lumbar disk reherniation

Most patients undergoing lumbar discectomy do very well, though approximately 10% experience a reherniation in the decade following their index procedure. Multiple studies have looked at risk factors for reherniation, and the most consistent predictors have been a large annular defect and a large remaining disk volume. In order to better synthesize the existing literature, Dr. Miller and colleagues performed a meta-analysis evaluating the relationship between annular defect width (medial-lateral) and reherniation or reoperation. Their literature search yielded 7 relatively high quality studies that have studied this topic, and they classified annular defects as small (<6 mm) or large (> 6mm). Over 1,600 patients were included, with a median follow-up of about 3 years. The authors did not report the actual reherniation and reoperation rates and instead reported the odds ratios (OR). The pooled OR for reherniation for large relative to small annular defects was 2.5, and the OR for reoperation was 2.3. One study by Carragee et al. had ORs of 9.2 and 8.3 for reherniation and reoperation, with most of the other studies reporting ORs between 1.5 and 3.5. Only one study (Wera et al.) reported ORs of less than 1 (0.76 for both outcomes), and the surgeons in this study performed more aggressive subtotal discectomy (as compared to sequestrectomy), which may have reduced the risk of reherniation. Multivariate analysis evaluating other risk factors was limited by what was reported in the studies and the relatively small number of reherniation patients. This limited analysis suggested that subtotal discectomy and age over 45 may reduce the risk of reherniation associated with a large annular defect to some degree. The authors concluded that annular defect width was a strong predictor of re-operation.

The authors have done a nice job synthesizing the current literature on the topic, and their results show rather conclusively that annular defect width is a strong risk factor for lumbar disk reherniation. It would have been nice if a more robust multivariate analysis had been performed to determine the relative strength of different predictors, but this was not possible due to limitations in what was reported by the different studies and the relatively low number of patients who experienced a reherniation. While this paper yielded information that might be helpful for counseling patients about their risk of reherniation following surgery, it is unlikely to change practice as annular defect size is not an easily modifiable risk factor. Surgeons have experimented with annular closure systems, though these have not been widely adopted. These data may encourage surgeons to minimize the size of the annulotomy they create in cases where the annulus remains intact, though most surgeons likely do this already. This study helps to confirm the belief that a large annular defect is a risk factor for recurrent disk herniation. Unfortunately, there is probably not much we can do about it.

Please read Dr. Miller’s article on this topic in the March 1 issue. Does this change your view of risk factors for recurrent disk herniation? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor