Introduction: Although buttock pain is common symptom in patients with lumbar degenerative disorders, the nature of buttock pain remains unclear. While most clinicians take it as either nociceptive back pain or radicular leg pain, it is proposed that buttock pain may be a mixed symptom of radicular pain and referred pain. This study aims to determine the occurrence rate, clinical characteristics, risk factors, as well as surgical outcomes of buttock pain in patients with lumbar disc herniation (LDH).
Methods: From 2019 to 2023, patients with a single-level LDH who underwent endoscopic discectomy at the author’s hospital were studied. Buttock pain was defined as the pain between the iliac crest and buttock crease, and was assessed using a numeric rating scale (NRS) before and after discectomy. On lumbar spine MR images, degenerative findings were assessed, and disc herniation was classified as contained and non-contained. The presence or absence of annulus rupture was further examined under endoscopy. The associations of buttock pain with demographics, MR findings, endoscopic findings, and back and leg pain were examined.
Results: A total of 321 single-level LDH patients were studied. Among them, 13 (4%) had a herniated disc at the L3/4 segment, 148 (46.1%) at L4/5, and 160 (49.8%) at L5/S1. Buttock pain presented in 242 (75.4%) patients. The presence of buttock pain was not associated with the spinal level with LDH. Buttock pain was more common in patients with contained LDH than in those with non-contained LDH on MRIs (85.4% vs 70.6%, P<0.05). Similarly, buttock pain was more common in LDH patients with intact annulus fibrosus than those ruptured (86.7% vs 68.7%, P<0.001), as assessed in endoscopy. For all patients, buttock pain significantly alleviated 1 day after discectomy (5.66±2.02 vs 0.82±1.23, P<0.001). There were 240 patients who were followed up 1 year after the surgery (follow-up rate 74.8%). Among the 182 patients who had buttock pain at baseline, 166 (91.2%) were cured (NRS＜2) and 16 (8.8%) patients’ buttock pain improved but still with some residual buttock pain (NRS ≥ 2) at 1 year follow-up. Contained LDH on pre-operative MR images was associated with residual leg pain (OR=3.92, P=0.002). Residual buttock pain after endoscopic discectomy was not associated with age, contained LDH, or any other factors studied.
Discussion: Buttock pain was common in surgical candidates of LDH and was not related to lumbar spinal level. Buttock pain derived from LDH is a surgically treatable symptom, as does radicular leg pain. Contained LDH on MR images and intact annulus identified in endoscopy were associated with the presence of buttock pain, suggesting that the occurrence of buttock pain may relate to abnormal intradiscal pressure in the disc.