Commentary & Perspective

Commentary & Perspective on
"Clinical Outcomes After Lumbar Discectomy for Sciatica: The Effects of Fragment Type and Anular Competence"
by Eugene J. Carragee, MD, et al.

Commentary & Perspective by
William A. Abdu, MD, MS, and James N. Weinstein, DO, MS*,
The Spine Center, Dartmouth Medical School, Hanover, NH

Disc herniation is the most common reason for the performance of lumbar spine surgery¹. The conventional teaching suggests that those most likely to benefit from surgery are patients with dermatomal symptoms, positive objective findings on physical examination (e.g., crossed straight-leg raising), and a pain level that is severe, rather than mild to moderate^2,3. A confirmatory imaging study is a prerequisite.

In this context, Carragee and colleagues have conducted yet another enlightening study of the outcomes of lumbar discectomy in patients with back and leg symptoms associated with a herniated lumbar intervertebral disc. The authors performed a prospective observational study of 187 consecutive patients with sciatica who were scheduled to undergo a single-level primary lumbar discectomy. One hundred and eighty of the 187 patients were evaluated at a minimum follow-up of two years (median, six years). The criteria included a diagnosis of sciatica with predominantly radicular symptoms and a preoperative magnetic resonance imaging study confirming disc herniation.

Herniation type was identified at the time of surgery and, after discectomy, the size of the anular defect was compared with the width of a number-1 Penfield probe (6mm). On the basis of the intraoperative findings, the disc herniations were classified into four categories: 1) Fragment-Fissure (minimal anular defect and an extruded or sequestrated fragment) (n = 89 patients); 2) Fragment-Defect (large anular defect and an extruded or sequestrated fragment) (n = 33 patients); 3) Fragment-Contained (intact anulus and greater than or equal to one subanular detached fragment) (n = 42 patients); and 4) No Fragment-Contained (intact anulus and no subanular detached fragment) (n = 16 patients). This is new terminology that is not typically used, either by interventional radiologists and/or orthopaedists or neurosurgeons, in the diagnosis and treatment of patients with disc herniation. Fardon and Milette reported on the nomenclature and classification of lumbar disc pathology in an article recently published by the North American Spine Society⁴.

Carragee et al. found that patients with Fragment-Fissure herniations, with a disc fragment and a small anular defect, had the best overall outcomes after discectomy with the lowest rates of re-herniation and reoperation (1% for both). The forty-two patients in the Fragment-Contained group had a 10% rate of re-herniation and two (5%) of them underwent a reoperation. Patients in the Fragment-Defect group, who had extruded fragments and massive posterior anular defects had a 27% rate of re-herniation and a 21% re-operation rate. Patients in the No Fragment-Contained group had a poor outcome—38% had recurrent and/or "persistent sciatica" and their standard outcome scores were less improved compared with patients in the other groups. The authors concluded that intraoperative findings, as described in this paper, correlated more clearly with outcomes than did demographic, socioeconomic, or clinical variables.

What's New

The authors of this cohort study have made three important contributions to the literature in regard to the selection of candidates for surgery—one contribution that is new and two that confirm current teaching. The new contribution is the finding that those patients with massive fragments in association with large anular defects had a significantly (p = 0.05 to 0.01) high rate of re-herniation (27%), even at the short-term follow-up. This suggests that if one knew this information preoperatively, during the informed consent process additional information could be provided to patients about the significant risk of re-herniation. Therefore, when this finding is noted intraoperatively, other options for treatment, including fusion, might be considered⁵.

The second finding confirms the contribution of psychometric measures provided with use of health surveys to the surgeon's decision-making process⁶. Caragee et al. noted that those in the No Fragment-Contained group had more psychometric abnormalities and worse outcomes after surgery. These patients tended to have poorer ratings for pain, a longer duration of preoperative work loss, and a smaller herniation size on magnetic resonance imaging scans. The inclusion of psychometric testing data, consisting of percentage changes in preoperative and postoperative scores, in the logistic regression analyses might also have provided some insight.

The third contribution is the confirmation of conventional teaching that imaging studies that demonstrate compressive pathoanatomy are critical to the decision-making process involved in the selection of patients who are suitable candidates for surgery⁷. The underlying premise of intervertebral disc excision is that the removal of nucleus pulposus/anulus fragments that create both compression and inflammation, which are factors in dermatomal pain patterns, is beneficial. The absence of convincing evidence of compressed pathoanatomy on the preoperative magnetic resonance imaging study (and on physical examination) suggests that inconclusive intraoperative findings are likely as well as a poorer surgical outcome in terms of function, pain, and satisfaction.

Physical examination

Carragee et al. did not mention any factoring of physical examination data into the decision-making process. Thus, we do not know whether objective physical findings could be correlated with the anatomic intraoperative findings or the findings of the imaging studies, all of which are of considerable importance in the processes of both surgical decision-making and informed-consent^8,9. The authors stated that their results suggested that the differences in outcomes and in rates of recurrence and reoperation can be predicted on the basis of operative findings. One might suggest that findings of the preoperative physical examination and those of the magnetic resonance imaging study may also have predictive value.

Lastly, throughout the text the authors stated that, on the basis of the numbers available, none of the variables other than disc herniation type had a statistically significant relationship with the rates of reherniation and reoperation. The lack of a more substantial sample size (which carries a potential for type-II error), a power calculation, an a priori hypothesis, or control groups introduces bias into the interpretation of the data. The authors suggested that a control group is not practical in the study of disc herniation; however, many surgical studies, past and current, have utilized control groups.

What's Next?

It is no surprise that those patients with the least convincing indications for lumbar discectomy had the poorest outcomes after surgical intervention. Strict adherence to established indications for the surgery was espoused by Sprangfort³ and Hakelius¹⁰ over thirty years ago and is still a prerequisite for the success of disc excision. Correlating the findings of the physical examination, imaging studies, and established psychometric testing to identify appropriate candidates for lumbar intervertebral disc excision is likely to result in improved outcomes. The proper selection of patients for surgical intervention and the consideration of patient preferences, given the best evidence-based information, remain challenging. However, heeding both patient preference and the medical evidence about possible treatment alternatives is a winning combination. When it comes to the performance of elective procedures in patients who present with a nonemergent herniated disc, adhering to a combination of medical evidence and patient preferences as guidelines in the choice of treatment will yield the best outcomes and satisfaction for both doctor and patient¹⁰.

We commend Carragee et al. on their fine work and their contributions towards a better understanding of the diagnosis and treatment of disorders of the lumbar spine.

*The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

References

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