Background: The aim of this study was to investigate the correlation between lumbar multifidus fat infiltration and lumbar postoperative surgical site infection (SSI). Several clinical studies have found that spine postoperative SSI is associated with age, diabetes, obesity, and multilevel surgery. However, few studies have focused on the correlation between lumbar multifidus fat infiltration and SSI. Method: A retrospective review was performed on patients who underwent posterior lumbar interbody fusion (PLIF) between 2011 and 2016 at our hospital. The patients were divided into SSI and non-SSI groups. Data of risk factors [age, diabetes, obesity, body mass index (BMI), number of levels, and surgery duration] and indicators of body mass distribution (subcutaneous fat thickness and multifidus fat infiltration) were collected. The degree of multifidus fat infiltration was analyzed on magnetic resonance images using Image J. Results: Univariate analysis indicated that lumbar spine postoperative SSI was associated with urinary tract infection, subcutaneous fat thickness, lumbar multifidus muscle (LMM) fat infiltration, multilevel surgery (≥2 levels), surgery duration, drainage duration, and number of drainage tubes. In addition, multiple logistic regression analysis revealed that spine SSI development was associated with sex (male), age (> 60 years), subcutaneous fat thickness, LMM fat infiltration, and drainage duration. Receiver operating characteristic curve analysis indicated that the risk of SSI development was higher when the percentage of LMM fat infiltration exceeded 29.29%. Furthermore, Pearson's correlation analysis demonstrated that LMM fat infiltration was correlated with age but not with BMI. Conclusion: Indicators of body mass distribution may better predict SSI risk than BMI following PLIF. Lumbar Multifidus fat infiltration is a novel spine-specific risk factor for SSI development.

Objective: This study evaluated the biomechanical changes in the adjacent vertebrae under a physiological load (500 N) when the clinically relevant amount of bone cement was injected into fractured cadaver vertebral bodies. Methods: The embalmed cadaver thoracolumbar specimens in which each vertebral body (T12-L2) had a BMD of < 0.75 g/cm 2 were used for the experiment. For establishing a fracture model, the upper one third of the L1 vertebra was performed wedge osteotomy and the superior endplate was kept complete. Stiffness of specimens was measured in different states. Strain of the adjacent vertebral body and intervertebral disc were measured in pre-fracture, post-fracture, and after augmentation by non-contact optical strain measurement system. Results: The average amount of bone cement was 4.4 ml (3.8-5.0 ml). The stiffness of after augmentation was significantly higher than the stiffness of post-fracture (p < 0.05), but still lower than pre-fracture stiffness (p < 0.05). After augmentation, the adjacent upper vertebral strain showed no significant difference (p > 0.05) with prefracture, while the strain of adjacent lower vertebral body was significantly higher than that before fracture (p < 0.05). In flexion, T12/L1 intervertebral disc strain was significantly greater after augmentation than after the fracture (p < 0.05), but there was no significant difference from that before the fracture (p > 0.05); L1/2 vertebral strain after augmentation was significantly less than that after the fracture (p < 0.05), but there was no significant difference from that before the fracture (p > 0.05). Conclusions: PVP may therefore have partially reversed the abnormal strain state of adjacent vertebral bodies which was caused by fracture.

Non-human primates are most suitable for generating cervical experimental models, and it is necessary to study the anatomy of the cervical spine in non-human primates when generating the models. The purpose of this study was to provide the anatomical parameters of the cervical spine and spinal cord in long-tailed macaques (Macaca fascicularis) as a basis for cervical spine-related experimental studies.Cervical spine specimens from 8 male adult subjects were scanned by micro-computed tomography, and an additional 10 live male subjects were scanned by magnetic resonance imaging. The measurements and parameters from them were compared to those of 12 male adult human subjects. Additionally, 10 live male subjects were scanned by magnetic resonance imaging, and the width and depth of the spinal cord and spinal canal and the thickness of the anterior and posterior cerebrospinal fluid were measured and compared to the relevant parameters of 10 male adult human subjects. The tendency of cervical parameters to change with segmental changes was similar between species. The vertebral body, spinal canal, and spinal cord were significantly flatter in the human subjects than in the long-tailed macaques.The cerebrospinal fluid space in the long-tailed macaques was smaller than that in the human subjects.The anatomical features of the cervical vertebrae of long-tailed macaques provide a reference for establishing a preclinical model of cervical spinal cord injury.