Cervical Myelopathy Caused by Non-Rheumatic Retro-Odontoid Pseudotumor: An Investigation of Underlying Mechanisms and Optimal Surgical Strategy.

STUDY DESIGN: Retrospective case-control study. OBJECTIVE: This study aimed to identify the underlying pathologies of non-rheumatic retro-odontoid pseudotumors (NRPs), which would help establish an appropriate surgical strategy for myelopathy caused by NRP. METHODS: We identified 35 patients with myelopathy caused by NRP who underwent surgery between 2006 and 2017. An age- and sex-matched control group of 70 subjects was selected from patients with degenerative cervical myelopathy. Radiographic risk factors for NRP were compared between cases and controls. We also assessed surgical outcomes following occipital-cervical (O-C) fusion, atlantoaxial (C1-2) fusion, or C1 laminectomy. RESULTS: Patients with NRP had significantly lower C1 sagittal inner diameter, C2-7 range of motion (ROM), C2-7 Cobb angle, and C7 tilt, as well as significantly higher C1-2 ROM, atlantodental interval (ADI), and C1-2 to O-C7 ROM ratio. Multivariate regression analysis revealed that ADI, C2-7 ROM, and C7 tilt were independent risk factors for NRP. Neurological recovery and pseudotumor size reduction were comparable among surgical procedures, whereas post-operative cervical spine function was significantly lower in the O-C fusion group than in the other groups. CONCLUSION: Non-rheumatic retro-odontoid pseudotumor was associated with an increase in ADI, suggesting that spinal arthrodesis surgery is a reasonable strategy for NRP. C1-2 fusion is preferable over O-C fusion because of the high prevalence of ankylosis in the subaxial cervical spine. Given that 29% of patients with NRP have C1 hypoplasia, such cases can be treated by posterior decompression alone. Our study highlights the need to select appropriate surgical procedures based on the underlying pathology in each case.

Accuracy of pedicle screw placement using patient-specific template guide system.

BACKGROUND: Despite repeated efforts for accurate cervical pedicle screw insertion, malpositioning of the inserted screw is commonly noted. To avoid neurovascular complications during cervical pedicle screw insertion, we have developed a new patient-specific screw guide system. This study aimed to evaluate the accuracy of cervical PS placement using the new patient-specific screw guide system. METHODS: This study is a retrospective clinical evaluation of prospectively enrolled patients. Seventeen consecutively enrolled patients who underwent posterior cervical fusion using the guide system were included. Firstly, three-dimensional planning of pedicle screw placement was done using simulation software. A screw guide for each vertebra was constructed preoperatively. A total of 77 screws were inserted with the guides. Postoperative computed tomography was used to evaluate pedicle perforation, and screw deviations, between the planned and actual screw positions, were measured. RESULTS: A total of 76 screws (98.7%) were completely inside the pedicle (C3-7), without neurovascular injuries. The mean screw deviations from the planned trajectory at the narrowest point of the pedicle and at the entry point in the axial and sagittal planes were 0.56 ± 0.43 mm and 0.43 ± 0.35 mm and 0.43 ± 0.30 mm and 0.63 ± 0.50 mm, respectively. There were no significant differences in any parameter at different spinal levels. Angular deviations in the sagittal and axial planes were 2.94 ± 2.04° and 2.53 ± 1.85°, respectively. Sagittal angular deviations tended to increase in the cranial vertebra (C3 and C4) compared to the middle cervical spine. CONCLUSIONS: We demonstrated that our patient-specific screw guide is vital for guiding precise screw insertion in the cervical pedicle. This technique may be an effective solution for achieving precise screw insertion and reducing the incidence of complications.

Is the administration of vancomycin to operative field effective? Studying from operative wound drainage tube culture.

PURPOSE: To investigate the efficacy of application of VCM powder to surgical wounds. METHODS: A total of 314 patients who underwent posterior spinal instrumentation with local application of VCM (VCM group) were compared to 354 patients without VCM (control). The wound drainage tube was submitted for bacterial culture. The number of positive cultures, types of bacteria, and incidence of surgical site infections (SSI) were investigated. RESULTS: Drainage tube culture was positive in 1.6% (5/314 cases) and 7.3% (26/354 cases) of the VCM and control groups, respectively (P = 0.004). Among the five positive cases in the VCM group, one had an SSI, compared to three of 26 in the control group. Among the culture-negative cases, 0 and six, respectively, had an SSI. Finally, the incidence of SSI was 0.3% (1/314 cases) and 2.5% (9/354 cases), respectively. SSI occurred significantly less often in the VCM than in the control group (P = 0.01). The pathogenic bacterium was P. aeruginosa in the VCM group and MSSE, S. marcescens, methicillin-resistant S. aureus (MRSA), etc., in the control group. CONCLUSION: This study indicates that the amount of bacteria in the operative field was decreased by local application of VCM. However, the incidence of positive culture of VCM-resistant bacteria was not decreased by VCM. Importantly, pathogenic bacteria in the VCM group were only VCM-resistant, supporting the efficacy of VCM. In conclusion, local application of VCM decreases the amount of bacteria in the operative field and leads to fewer SSIs.

Subaxial sagittal alignment after atlantoaxial fixation techniques.

STUDY DESIGN: A retrospective clinical case series. OBJECTIVES: To evaluate the association between C1-C2 fixation angle and postoperative C2-C7 alignment in the sagittal plane after C1 lateral mass screw with C2 pedicle screw fixation (C1-LMS) or Magerl with wiring technique. SUMMARY OF BACKGROUND DATA: Various techniques for posterior correction and fusion, such as the Magerl procedure with posterior wiring and C1-LMS procedures, are used for treating atlantoaxial instability. However, only few studies investigating the relationship between postoperative C1-C2 angle and C2-C7 sagittal alignment change after C1-C2 fixation have been reported. METHODS: We retrospectively followed up 42 patients who underwent the C1-LMS (22 patients) or Magerl with wiring procedure (20 patients) to treat C1-C2 instability for >2 years. The atlantodental interval, space available for the spinal cord, and O-C1, C1-C2, C2-C3, and C2-C7 angles were measured. RESULTS: Significant reduction in atlantodental interval and increase in space available for the spinal cord were observed in both groups. Although the preoperative C1-C2 angles were similar, the angle at the final follow-up was higher in the Magerl with wiring group than in the C1-LMS group (P<0.01). The C1-C2 fixation and postoperative C2-C7 angles were negatively correlated in both groups (C1-LMS group, r=-0.55, P<0.01; Magerl with wiring, r=-0.62, P<0.01). CONCLUSIONS: Increased lordotic change in the C1-C2 angle was associated with increased kyphotic changes in the C2-C7 angle after both procedures. The C1-LMS procedure effectively controlled C1-C2 sagittal alignment during surgery. To decrease the risk of postoperative subaxial kyphotic changes, the C1-C2 fixation angle should be carefully determined.

Active immunization against macrophage migration inhibitory factor using a novel DNA vaccine prevents ovariectomy-induced bone loss in mice.

Previous studies have demonstrated that mice deficient in the macrophage migration inhibitory factor (MIF) gene are protected from ovariectomy (OVX)-induced bone loss. We developed a novel MIF-deoxyribonucleic acid (DNA) vaccine by introducing oligonucleotides encoding a helper T epitope into the cDNA sequence of murine MIF. Mice given the MIF-DNA vaccine produced high titers of autoantibody against MIF, and were protected from OVX-induced bone loss. Our results further support the hypothesis that MIF is involved in the pathomechanism of OVX-induced bone loss, and also show that active immunization against MIF using a DNA vaccine may be useful for the prophylactic treatment of postmenopausal osteoporosis.

Macrophage migration inhibitory factor-deficient mice are resistant to ovariectomy-induced bone loss.

A link between macrophage migration inhibitory factor (MIF) and estrogen has recently emerged. We examined the involvement of MIF in osteoporotic changes in bone after ovariectomy (OVX), and revealed that MIF-deficient mice (MIF-KO) were completely protected from this phenomenon. The increase in osteoclast number per bone surface and serum IL-1beta levels, which were observed in wild-type mice after OVX, did not occur in MIF KO. Our data suggest that MIF plays an important role in the pathogenesis of postmenopausal osteoporosis, and could be a novel target for the treatment of this disease.