Computed Tomographic Morphometric Analysis of C1 and C2 for Lamina Cross Screw Placement in Malay Ethnicity

Characteristics and Comparisons of Morphometric Measurements and Computed Tomography Hounsfield Unit Values of C2 Laminae for Translaminar Screw Placement Between Patients With and Without Basilar Invagination

OBJECTIVE

Patients with basilar invagination (BI) had high incidences of vertebral variations and high-riding vertebral artery (HRVA) that might restrict the use of pedicle or pars screw and increase the use of translaminar screw on axis. Here, we conducted a radiographic study to investigate the feasibility of translaminar screws and the bone quality of C2 laminae in patients with BI, which were compared with those without BI as control to provide guidelines for safe placement.

METHODS

In this study, a total of 410 patients (205 consecutive patients with BI and 205 matched patients without BI) and 820 unilateral laminae of the axis were included at a 1:1 ratio. Comparisons with regard to insertion parameters (laminar length, thickness, angle, and height) for C2 translaminar screw placement and Hounsfield unit (HU) values for the assessment of the appropriate bone mineral density of C2 laminae between BI and control groups were performed. Besides, the subgroup analyses based on the Goel A and B classification of BI, HRVA, atlas occipitalization, and C2/3 assimilation were also carried out. Furthermore, the factors that might affect the insertion parameters and HU values were explored through multiple linear regression analyses.

RESULTS

The BI group showed a significantly smaller laminar length, thickness, height, and HU value than the control group, whereas no significant difference was observed regarding the laminar angle. By contrast, the control group showed significantly higher rates of acceptability for unilateral and bilateral translaminar screw fixations than the BI group. Subgroup analyses showed that the classification of Goel A and B, HRVA, atlas occipitalization, and C2/3 assimilation affected the insertion parameters except the HU values. Multiple linear regression indicated that the laminar length was significantly associated with the male gender (B = 0.190, p < 0.001), diagnoses of HRVA (B = -0.109, p < 0.001), Goel A (B = -0.167, p < 0.001), and C2/3 assimilation (B = -0.079, p = 0.029); the laminar thickness was significantly associated with the male gender (B = 0.353, p < 0.001), diagnoses of HRVA (B = -0.430, p < 0.001), Goel B (B = -0.249, p = 0.026), and distance from the top of odontoid to the Chamberlain line (B = -0.025, p = 0.003); laminar HU values were significantly associated with age (B = -2.517, p < 0.001), Goel A (B = -44.205, p < 0.001), Goel B (B = -25.704, p = 0.014), and laminar thickness (B = -11.706, p = 0.001).

CONCLUSION

Patients with BI had narrower and smaller laminae with lower HU values and lower unilateral and bilateral acceptability for translaminar screws than patients without BI. Preoperative 3-dimensional computed tomography (CT) and CT angiography were needed for BI patients.

Bioelectrical Impedance Analysis Can Be an Effective Tool for Screening Fatty Liver in Patients with Suspected Liver Disease

Background and study aims: Although abdominal ultrasound (USG) or controlled attenuation parameter (CAP) score of transient elastography (TE) is recommended for the diagnosis of fatty liver, issues regarding cost and accessibility still exist. The aim of this study was to evaluate if bioelectrical impedance analysis (BIA) can be used as a reliable screening tool for fatty liver. Patients and methods: A total of 249 patients who underwent all three tests including TE, BIA, and USG were enrolled. The correlation between fat mass measured by BIA, CAP score of TE, and fatty liver grade measured by USG was analyzed. In addition, the cut-off value of BIA which can predict the fatty liver grade was calculated. Results: Fat mass index (FMI) assessed by BIA increased significantly along with the rise in fatty liver grade measured by USG (normal: 6.2 ± 2.4, Gr I: 8.0 ± 3.7, Gr II: 10.6 ± 3.5, Gr III: 10.7 ± 3.7 kg/m2, p < 0.001). In addition, a positive correlation was found between the CAP score of TE and the FMI of BIA. Additionally, a total body fat mass increase by 24.3% or 29.8% in men and 34.8% or 35.1% in women increased the possibility of developing any grade of fatty liver or significant fatty liver (≥Gr II fatty liver), respectively. Conclusion: The total fat or fat mass index of BIA was related to fatty liver as assessed by ultrasound or CAP score, and area under the receiver operating characteristic (AUROC) was about 0.8. Thus, BIA can be used as a screening tool for fatty liver in patients with suspected liver disease.

The medial window technique as a salvage method to insert C2 pedicle screw in the case of a high-riding vertebral artery or narrow pedicle: a technical note and case series

PURPOSE

To describe the safety and feasibility of C2 medial window screw (C2MWS) as an alternative salvage method for C2 pedicle screws in cases of high-riding vertebral artery (HRVA) or narrow pedicle.

METHODS

The C2MWS technique involves screw insertion by intentionally breaching the medial cortex of the pedicle to avoid vertebral artery injury. Twelve patients who underwent C2 screw insertion via the C2MWS were retrospectively reviewed. C2MWS was indicated in cases of high-riding vertebral artery (HRVA) or narrow pedicle (pedicle width ≤ 4 mm). The width of the canal breach by screw, vertebral artery groove (VAG) breach, solid fusion, neck pain visual analogue scale (VAS) score, and Japanese Orthopedic Association (JOA) score were assessed as outcome measurements.

RESULTS

C2MWS was indicated due to both HRVA and narrow pedicle for 11 screws, narrow pedicle for one screw, and HRVA for two screws. No screw VAG breach or vertebral artery injury was noted postoperatively. The mean width of canal breach was 2.9 ± 1.3 mm. There were no cases demonstrating neurologic deterioration, and 11 patients (91.7%) demonstrated solid fusion at 1-year follow-up. Furthermore, neck pain VAS and JOA scores significantly improved after the surgery.

CONCLUSIONS

The C2MWS technique can provide 3-column fixation while reliably avoiding VA injury. C2MWS could be considered as a salvage alternative method when the insertion of C2 pedicle screw is complicated by HRVA or a narrow pedicle, while there is a need to provide firmer fixation strength than that provided by pars or translaminar screws.

LEVEL OF EVIDENCE: 4

Translaminar screw of C1 for the reinforcement of subaxial cervical spine reconstruction

Translaminar screws in the cervical spine have been mostly employed at C2 level when conventional trajectories are challenging. However, reports in the literature of translaminar screw of C1 are remarkably anecdotal. We aimed to report a case using C1 translaminar in addition to C1 lateral mass screws for the reinforcement of subaxial cervical spine reconstruction. We present a 22-year-old female patient, who developed persistent cervical pain, and computed tomography scan demonstrated lytic lesions of the vertebral bodies and lateral masses from C3 to C6. Magnetic resonance imaging showed spinal cord compression without myelopathy. Surgical biopsy was inconclusive, and an oncological vertebral instability led to surgical stabilization. Laminectomy and bilateral facetectomy of levels involved was achieved, instrumentation from C1 to T3 and reconstruction with posterolateral fibula bilaterally, and without occipital fixation. A third satellite rod was placed using C1-2–7 translaminar screws. Translaminar screw of C1 is a feasible alternative for increasing the strength of the construct.

Surgical Outcomes for C2 Tear Drop Fractures: Clinical Relevance to Hangman's Fracture and C2-3 Discoligamentous Injury

Objective

To analyze characteristics of surgically managed tear drop (TD) fractures of the C₂ axis associated with other injuries such as hangman's fracture and C_2‐3 discoligamentous injury as well as treatment outcomes.

Methods

A total of 14 patients (eight men and six women) with TD fractures of the C₂, who were surgically treated at four national trauma centers of tertiary university hospitals from January 2000 to December 2017, were included in this retrospective study. The mean age of the patients was 45.5 years (ranging from 19 to 74 years). The characteristics, surgical treatment methods (anterior fusion vs posterior fusion), and results of 14 TD fractures of the C₂ were analyzed retrospectively. And the clinical relevance between C₂ TD fracture and hangman's fracture and C_2‐3 discoligamentous injury was investigated through the co‐occurrence between injuries. The mean follow‐up time after surgery was 22.6 months (ranging from 12 to 60 months).

Results

Among 14 patients with TD fracture of the C₂, four patients (28.6%) had anterior TD fracture and 10 patients (71.4%) had posterior TD fracture. All 10 posterior TD fracture patients had anterior C_2‐3 displacement. While two of four anterior TD fracture patients had posterior C_2‐3 displacement, the remaining two did not. All 14 patients of TD fracture had at least two or more other associated C₂ injuries as well as C_2‐3 discoligamentous injuries. About 92.9% (13/14) of the patients had typical or atypical hangman's fracture; 100% (10/10) of the posterior TD fracture patients had hangman's fracture, but 75% (3/4) of the anterior TD fracture had hangman's fracture. At admission, 13 patients were neurologically intact. However, the remaining patient had spinal cord injury with American Spinal Injury Association (ASIA) impairment scale B with C_2‐3 bilateral facet dislocation. All four anterior TD fracture patients underwent posterior C_2‐3 fusion. While four of 10 posterior TD fracture patients underwent C_2‐3 anterior fusion, the remaining six underwent posterior fusion. At last follow‐up, 100% (14/14) of the patients achieved solid fusion, and visual analog scale for neck pain was significantly improved (5.9 vs 2.2, P < 0.001). One patient with ASIA impairment scale B had significantly improved to scale D. No major complications occurred.

Conclusion

Our study showed that surgically managed TD fractures of the C₂ showed a high incidence of other associated spine injuries including hangman's fracture and C_2‐3 discoligamentous injury. Therefore, special attention and careful radiologic evaluation are needed to investigate the presence of other associated spine injuries including hangman's fracture and C_2‐3 discoligamentous injury, which are likely to require surgery.