Sensing tissue acidosis is an important function of the somatosensory nervous system to response to noxious stimuli. In the pain clinic, acid or soreness sensation is a characteristic sensory phenotype of various acute and chronic pain syndromes, such as delayed onset muscle soreness, fibromyalgia, and radicular pain. However, soreness sensation is a sign of successful analgesia for acupuncture and noxipoint therapy. Thus, the nature of acid or soreness sensation is not always nociceptive (or painful) and could be anti-nociceptive. To facilitate the investigation of the molecular and neurobiological mechanisms of soreness sensation, we propose a concept called “sngception (sng- ception)” to describe the response of the somatosensory nervous system to sense tissue acidosis and to distinguish it from nociception. “Sng” is a Taiwanese word that represents the state of soreness while at the same time imitates the natural vocalization of humans feeling sore. Here we propose sngception as a specific somatosensory function that transmits the acid sensation from the peripheral to the central nervous system. Sngception could partially overlap with nociception, but it could also transmit antinociception, proprioception, and pruriception.

Proprioceptors are primary mechanosensory neurons to monitor the status of muscle contraction and/or body position ( 1 ). Although proprioceptors are known as non-nociceptive mechanoreceptors, they also express the pro-nociceptive acid-sensing ion channel 3 (ASIC3) ( 2 – 5 ). To probe the role for proprioceptors in sensing acidosis (or sngception) ( 6 ), we found that genetic deletion of Asic3 in proprioceptors but not in nociceptors abolished acid-induced chronic hyperalgesia in mice. Chemo-optogenetically activating proprioceptors resulted in hyperalgesic priming that favored chronic pain induced by acidosis. In humans, intramuscular acidification induced acid perception but not pain. Conversely, in a spinal cord–injured patient who lost pain sensation in the right leg, proprioception and sngception were remaining somatosensory functions, associated with the spinal dorsal column. Together, evidence from both mouse and human studies suggests a role for proprioceptors in sngception.

Refracture of cemented vertebrae occurs commonly after vertebroplasty (VP) for osteoporotic vertebral compression fracture (OVCF). It can result in severe pain or neurological deficit, but no preventive medication is available. Owing to the bone anabolic benefits of teriparatide (TP), this study was aimed to compare the outcomes of cemented vertebrae with TP to those without TP. Patients who received VP for OVCF with at least 1 year follow-up were included. The anterior body height (ABH) and middle body height (MBH) and kyphotic angle (KA) were measured before VP and 1 week and at least 1 year after VP. Refracture was defined as a 15% decrease in ABH or MBH and 8° decrease in KA compared with those at postoperative 1 week. The clinical outcomes were evaluated. 35 VP procedures in 21 patients treated with TP (TP group), and, matched to that, 29 out of 133 patients treated with VP alone (VP group) were included. One year after VP, ABH and MBH were significantly greater, except KA, in the TP group (VP group vs. TP group: KA − 4.97° ± 12.1 vs. −2.85° ± 12.21°, p = 0.462, ABH 1.56 ± 0.48 cm vs. 1.84 ± 0.56 cm, p = 0.027, MBH 1.49 ± 0.39 cm vs. 1.73 ± 0.41 cm, p = 0.017). The refracture rates of KA, ABH, and MBH were significantly lower in the TP group (VP group vs. TP group: KA 42.11% vs.8.57%, p < 0.001; ABH 76.32% vs. 28.57%, p < 0.0001; MBH 76.32% vs. 28.57%, p < 0.0001). In single-level subgroup comparison, TP was associated with better improvement of pain VAS and better radiological outcomes. TP was associated with higher BHs and fewer refractures than VP alone, with comparable clinical outcomes 1 year after VP. TP may be associated with better improvement of pain VAS in those with single-level VP procedure. Higher BH was due to the better maintenance effect of TP.

Introduction Soreness is a common complaint in patients who receive lumbar spine surgery (LSS) for degenerative lumbar spine diseases (DLSD). However, soreness is not assessed independently and its impacts on outcomes of LSS remains largely unknown. Sng(pronounced sә-ng, 痠) in Chinese language is the word with the closest meaning to soreness, and Chinese-speaking people naturally use sng to describe their non-pain ‘soreness’ symptom. This study was aimed to investigate the prevalence and impacts of soreness or sng on outcome of LSS by introducing Visual Analogue Scale (VAS) of sng on back and leg. Materials and methods This prospective cohort study recruited patients who receive LSS for DLSD. Participants completed the patient-reported outcome measures at 1 week before and 1 years after LSS. The patient-reported outcome measures included (1) VAS for back pain, leg pain, back sng and leg sng, (2) Oswestry Disability Index (ODI) and (3) RAND 36-item Short Form Health Survey. The minimal clinical important difference (MCID) of ODI and physical component health-related quality of life (HRQoL) was used. Results A total of 258 consecutive patients were included and 50 dropped out at follow-up. Preoperatively, the prevalence of sng was comparable to pain both on back and leg; postoperatively, the prevalence of sng was higher than pain. Leg and back sng were associated with preoperative and postoperative mental HRQoL, respectively. The reduction of sng on back and leg were significantly less than pain postoperatively. Leg sng was the only symptom independently associated with attaining MCID. Conclusion Soreness or sng should be assessed independently from pain in patients receiving LSS for DLSD because soreness or sng had substantial clinical impacts on the outcome of LSS.