Sng as a distinct pain phenotype after minimally invasive spine surgery: Implications for analgesic use and recovery outcomes

BACKGROUND: Chronic postsurgical pain (CPSP) remains a major clinical challenge due to its heterogeneous pathophysiology and variable response to current analgesics. Sng (), a culture-specific sensory term used by Chinese-speaking patients to describe acid-like muscle soreness alongside pain, has been identified as a distinct dimension of chronic pain with unique underlying mechanisms and limited responsiveness to current therapies. This study proposed a CPSP phenotyping framework according to the presence and predominance of sng and non-sng components and evaluated the association of sng with clinical outcomes and analgesic utilization. METHODS: Two independent retrospective cohorts were analyzed, including patients who underwent minimally invasive spine surgery (MISS) and who underwent vertebroplasty for osteoporotic vertebral compression fracture (OVCF). One-year postoperative patient-reported outcome measures (PROMs) and pharmacological burden quantified by the Medication Quantification Scale (MQS), were compared among four pain phenotypes: no CPSP, non-sng, sng, and mixed. RESULTS: In the MISS cohort, 72 patients had resolved pain and 207 had CPSP, including 30 (14.5%) with non-sng-dominant, 91 (44.0%) with sng-dominant, and 86 (41.5%) with mixed phenotypes. In the OVCF cohort, 39 patients had resolved pain and 78 had CPSP after vertebroplasty, including 5 (6.4%) with non-sng-dominant, 46 (59.0%) with sng-dominant, and 27 (34.6%) with mixed phenotypes. In both cohorts, sng-related phenotypes, particularly the mixed phenotype, were associated with poorer clinical outcomes, longer medication use, and greater pharmacological burden. CONCLUSION: Sng represents a major component of CPSP, and incorporating sng into CPSP phenotyping may facilitate mechanism-based, phenotype-specific management strategies.