Osteoarthritis (OA) shows various clinical manifestations depending on the status of its joint components. We aimed to identify the synovial cell subsets responsible for OA pathophysiology by comprehensive analyses of human synovium samples in single-cell resolution. Two distinct OA synovial tissue groups were classified by gene expression profiles in RNA-Seq: inflammatory and fibrotic. The inflammatory group exhibited high expression of inflammatory cytokines, histologically inflammatory infiltrate, and a more severe pain score. The fibrotic group showed higher expression of fibroblast growth factor (FGFs) and bone morphogenetic proteins (BMPs), showed histologically perivascular fibrosis, and showed a lower pain score. In single-cell RNA-Seq (scRNA-Seq) of synovial cells, MERTK ^lo CD206 ^lo macrophages and CD34 ^hi fibroblasts were associated with the inflammatory and fibrotic groups, respectively. Among the 3 fibroblast subsets, CD34 ^lo THY1 ^lo and CD34 ^lo THY1 ^hi fibroblasts were influenced by synovial immune cells, whereas CD34 ^hi fibroblasts were influenced by mural and endothelial cells. Particularly, in CD34 ^hi fibroblast subsets, CD34 ^hi CD70 ^hi fibroblasts promoted proliferation of Tregs, potentially suppressing synovitis and protecting articular cartilage. Elucidation of the mechanisms underlying the regulation of these synovial cell subsets may lead to novel strategies for OA therapeutics.

Background and objectives: Minimally invasive surgery has become popular for posterior lumbar interbody fusion (PLIF). Microendoscope-assisted PLIF (ME-PLIF) utilizes a microendoscope within a tubular retractor for PLIF procedures; however, there are no published reports that compare Microendoscope-assisted to open PLIF. Here we compare the surgical and clinical outcomes of ME-PLIF with those of open PLIF. Materials and Methods: A total of 155 consecutive patients who underwent single-level PLIF were registered prospectively. Of the 149 patients with a complete set of preoperative data, 72 patients underwent ME-PLIF (ME-group), and 77 underwent open PLIF (open-group). Clinical and radiographic findings collected one year after surgery were compared. Results: Of the 149 patients, 57 patients in ME-group and 58 patients in the open-group were available. The ME-PLIF procedure required a significantly shorter operating time and involved less intraoperative blood loss. Three patients in both groups reported dural tears as intraoperative complications. Three patients in ME-group experienced postoperative complications, compared to two patients in the open-group. The fusion rate in ME-group at one year was lower than that in the open group (p = 0.06). The proportion of patients who were satisfied was significantly higher in the ME-group (p = 0.02). Conclusions: ME-PLIF was associated with equivalent post-surgical outcomes and significantly higher rates of patient satisfaction than the traditional open PLIF procedure. However, the fusion rate after ME-PLIF tended to be lower than that after the traditional open method.

Purpose: Dubousset et al. proposed that the “cone of economy” (COE) in the inverted pendulum model of human standing increases in size significantly in patients with balance impairment. The clinical significance of COE size measured by motion capture as a postural sway index in adult spinal deformity (ASD) patients remains unclear. Methods: Twenty-three patients undergoing ASD surgery in a single institution as well as five healthy male participants were enrolled. The motion-capture of the surface reflection markers above the C7 and S1 spinous processes was performed using infrared cameras, and the most appropriate biomarker of postural stability was determined based on the measurement reliability and the correlations with center of pressure (COP) parameters measured by the force plate. The measurement was repeated 6-months later to examine the postoperative change. Results: Among the various COE parameters, the root mean square (RMS) area of C7 spinous process showed the high measurement reliability with strong correlation with RMS area of COP (ICC (3, k): 0.713, rho = 0.606, p < 0.001). Twelve patients showed their RMS area one standard deviation larger than the mean of healthy participants (23–40 years, 1.8 ± 1.3 cm²). These decompensated patients were older than the others (79.6 vs. 68.2 years old, p = 0.006), and showed the significant reduction in COE size (6.1 vs. 3.2 cm², p = 0.02) 6-months post-operatively. Conclusion: Motion-capture based size measurement of COE was a useful assessment tool for postural stability in ASD patients, showing the significant postoperative reduction in the subgroup of ASD patients with preoperative breakdown of balance compensation mechanisms.

Purpose: Degenerative cervical myelopathy (DCM) and idiopathic normal pressure hydrocephalus (iNPH) share symptoms such as gait disturbance and urinary dysfunction, especially in the elderly. While the incidence of DCM in patients with iNPH is reported, the prevalence of iNPH in patients with DCM remains unclear. This study investigates the prevalence of iNPH in DCM patients. Methods: This retrospective cohort study included 83 patients undergoing decompression surgery for DCM between April 2018 and March 2023. Brain MRI performed within three years prior to surgery was analyzed. Patients were categorized into two groups based on the Evans Index (EI): those with EI > 0.3 were classified as the Suspected-iNPH group, and those with EI ≤ 0.3 as the Non-iNPH group. Pre- and postoperative Japanese Orthopedic Association (JOA) scores and Patient-Reported Outcomes (PROs), including the Neck Disability Index (NDI), EuroQOL-5D (EQ-5D), Core Outcome Measure Index (COMI), and Numerical Rating Scale (NRS) for pain, were compared. Suspected-iNPH cases underwent further analysis to identify disproportionately enlarged subarachnoid space hydrocephalus (DESH). Results: Thirty-one patients (37%) were classified as Suspected-iNPH, who were significantly older (p = 0.01). No significant differences were found in pre- or postoperative JOA scores, and PROs. DESH was identified in 6 patients (7%), with 2 diagnosed as probable-iNPH based on cerebrospinal fluid tap tests. Conclusions: A notable proportion of elderly DCM patients exhibit ventricular enlargement and DESH, suggesting a potential overlap with iNPH. Brain MRI should be considered for elderly DCM patients, particularly when neurological symptoms deviate from typical patterns.

Purpose: Dural opening in cranial surgery causes noninfectious prolonged fever, such as aseptic meningitis, often necessitating additional diagnostic testing and medical costs. However, its impact in spinal surgery remains underexplored. Methods: In this propensity-matched, retrospective multicentre study, data from 12,791 spinal surgeries performed between April 2017 and March 2024 at four institutions were reviewed. After excluding cases with pyrexia-inducing conditions and unintended dural injuries, 2,880 patients were identified. Propensity score matching yielded two balanced cohorts: a dural opening group ( n = 166) and the control group without dural opening or injury ( n = 166). Following post-enrolment exclusion of perioperative infections, 135 dural opening and 118 control cases were analysed. The primary outcome was prolonged postoperative fever (≥ 37.7 °C occurring on or after postoperative day 7). Subgroup analysis assessed risk factors for prolonged fever in the dural opening group. Results: Prolonged postoperative fever occurred significantly more in the dural opening group than in the control group (9% vs. 1%, p < 0.05). The dural opening group exhibited higher peak body temperatures, longer fever durations, elevated white blood cell counts, increased cerebrospinal fluid (CSF) leakage, longer operative times, greater blood loss, and extended postoperative hospitalisations ( p < 0.05). Subgroup analysis revealed significant associations between postoperative fever and factors such as higher cranial-most surgical levels, CSF leakage, artificial dural reconstruction, and blood transfusion ( p < 0.05). Conclusion: Dural opening during spinal surgery is associated with noninfectious postoperative fever. Identifying these associated key factors may help refine postoperative management strategies.