RESUMO
Stem cell transplantation is proven to be a promising strategy for intervertebral disc degeneration (IDD) repair. However, replicative senescence of bone marrow-derived mesenchymal stem cells (BMSCs), shear damage during direct injection, mechanical stress, and the reactive oxygen species (ROS)-rich microenvironment in degenerative intervertebral discs (IVDs) cause significant cellular damage and limit the therapeutic efficacy. Here, an injectable manganese oxide (MnOx)-functionalized thermosensitive nanohydrogel is proposed for BMSC transplantation for IDD therapy. The MnOx-functionalized thermosensitive nanohydrogel not only successfully protects BMSCs from shear force and mechanical stress before and after injection, but also repairs the harsh high-ROS environment in degenerative IVDs, thus effectively increasing the viability of BMSCs and resident nucleus pulposus cells (NPCs). The MnOx-functionalized thermosensitive nanohydrogel provides mechanical protection for stem cells and helps to remove endogenous ROS, providing a promising stem cell delivery platform for the treatment of IDD.
RESUMO
OBJECTIVE: Facet joint violation (FJV) is associated with postoperative low-back pain and is a confirmed risk factor for adjacent-segment degeneration, a long-term complication of lumbar fusion surgery. The authors' knowledge of its mechanisms comes from in vitro biomechanical research only; there is a lack of radiographic evidence of the effects of violation on the superior adjacent-segment facet joint, intervertebral disc, and other local radiographic parameters. Furthermore, any differences between unilateral and bilateral violation remain relatively unclear. The authors therefore aimed to explore the effects of nonviolation and unilateral and bilateral violation on radiographic degeneration of the facet joint and intervertebral disc at the fusion and superior adjacent segment. Patient-reported clinical outcomes were compared at the 2-year follow-up. METHODS: The authors retrospectively analyzed data from 148 patients with lumbar degenerative diseases who underwent single-segment minimally invasive transforaminal lumbar interbody fusion between 2016 and 2020. FJV and facet joint degeneration were evaluated and graded using Shah's method and Pathria's standard, respectively. Radiographic parameters, including disc height and intervertebral Cobb angle at the fusion and superior adjacent segment, were measured. Clinical outcomes were evaluated using visual analog scale (VAS) and Japanese Orthopaedic Association scores. RESULTS: Preoperative data were comparable among the 3 groups (nonviolation, unilateral violation, and bilateral violation) (p > 0.05). Patient-reported clinical outcomes were followed up for at least 2 years (average duration 28.17 ± 6.17 months). At the last follow-up, facet joint degeneration grades were sequentially increased in the nonviolation, unilateral violation, and bilateral violation groups (p = 0.006). The unilateral (2.45 ± 2.17 mm) and bilateral (2.70 ± 1.94 mm) violation groups had more severe losses of disc height in the superior adjacent segment than did the nonviolation group (1.31 ± 2.01 mm). The VAS low-back pain and Japanese Orthopaedic Association scores in the bilateral (2.57 ± 1.44 and 19.83 ± 2.84, respectively) and unilateral (2.26 ± 0.79 and 20.43 ± 3.85, respectively) violation groups were significantly worse than in the nonviolation group (1.69 ± 1.12 and 21.80 ± 3.36, respectively) (p < 0.05). By contrast, there were no significant between-group differences in disc height, intervertebral Cobb angle in the fusion segment, or VAS leg pain scores (p > 0.05). CONCLUSIONS: FJV was associated with postoperative low-back pain and worse functional outcomes. It also aggravated facet joint and intervertebral disc changes in the superior adjacent segment, especially when bilateral violation occurred; this may be part of the mechanisms of adjacent-segment degeneration.