Commentary & Perspective by
Alexander R. Vaccaro, MD*,
The Rothman Institute, Philadelphia, Pennsylvania
It is widely believed that removal of a herniated lumbar disc to treat nonradicular low-back pain often leads to an unsatisfactory outcome; in fact, many patients report that axial low-back pain is actually worse after the operation. In contrast, it is much easier to predict a reduction of leg pain in the dermatomal distribution of a compressed nerve after discectomy. The authors of this paper reviewed previous studies that evaluated the outcomes of patients who had continuing low-back pain after lumbar discectomy. Weber reported that six (11%) of fifty-six patients had considerable low-back pain four years after the surgical procedure1. Hanley and Shapiro noted that twelve (14%) of eighty-seven patients continued to have low-back pain after lumbar discectomy2. What was unclear from these studies was the prevalence of low-back pain in the patient population before surgery.
In this study, Toyone and coauthors prospectively studied the effects of lumbar discectomy on axial low-back pain. The prospective nature of the study design removed the potential for error that is often inherent in the retrospective recall of symptoms. Thirty-seven of forty patients in this study had improvement in back symptoms, one patient had no appreciable change, one had slight deterioration, and one patient had considerable worsening of discomfort. Considering the limited number of patients, however, it is difficult to determine whether the physical removal of the disc was responsible for the decrease in axial low-back pain or whether the relief of leg pain, the primary disability for these patients, resulted in such an improved overall functional result that other related symptoms (i.e., low-back pain) became less bothersome to the patient.
It is hypothesized that as a disc begins to herniate, it puts pressure on the posterior portion of the anulus fibrosus and the posterior longitudinal ligament, resulting in sensitization of the sinuvertebral nervous system and presenting clinically as axial low back pain. Once a herniated disc extrudes through the posterior longitudinal ligament, patients often have some relief of back pain but may begin to have leg discomfort. Kuslich et al. demonstrated in awake but partially sedated patients that the posterior portion of the anulus and the posterior longitudinal ligament, when irritated or inflamed, were the tissues primarily responsible for the symptoms of low-back and leg pain3. This understanding is the basis for the historical support of percutaneous nuclear decompressive procedures, the premise of which is that relieving the pressure on these structures will result in a reduction of back pain. Unfortunately, this hypothesis has not been supported with any substantial, evidence-based research, to my knowledge. In fact, as stated previously, disc removal in the absence of radicular symptoms often results in a worsening of axial discomfort.
This paper is valuable because it prospectively defines the prevalence of low-back pain in a similar group of patients who underwent excision of a symptomatic, herniated lumbar disc. It does not prove that removal of the disc was the cause of pain relief, but only that a majority of patients reported fewer symptoms following removal of the disc. Interestingly, this outcome is often consistent with the natural history of back pain that has been relieved without surgery. A comparative study of the surgical and the nonsurgical management of patients with substantial back and leg pain is needed to define the influence of surgical intervention on the relief of back pain. Fortunately, the findings of this study do support the contention and often-expressed opinion that back pain, for some reason, appears to decrease postoperatively when the operation is performed primarily as a treatment for radicular symptoms. However, until further evidence is provided to the contrary, it is important to educate patients that the outcome of disc excision that is performed as a treatment for back pain alone is often unpredictable and that the operation may, in fact, result in a worsening of axial pain.
*The author did not receive grants or outside funding in support of his research or preparation of this manuscript. He 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 author is affiliated or associated.
1. Weber H. Lumbar disc herniation: a controlled prospective study with ten years of observation. Spine. 1983;8:131-40.
2. Hanley EN Jr, Shapiro DE. The development of low-back pain after excision of a lumbar disc. J Bone Joint Surg Am. 1989;71:719-21.
3. Kuslich SD, Ulstrom CL, Michael CJ. The tissue origin of low back pain and sciatica: a report of pain response to tissue stimulation during operations on the lumbar spine using local anesthesia. Orthop Clin North Am. 1991:22:181-7.