Liujun Zhao

Changes of pulmonary function for patients with osteoporotic vertebral compression fractures after kyphoplasty.

One of the consequences of osteoporotic vertebral compression fractures (OVCFs) is progressive collapse of the fractured osteoporotic vertebral body. This can lead to spinal kyphosis that may cause restriction of respiratory function. The balloon kyphoplasty procedure can reduce kyphosis and relieve the pain. There are few studies that have appropriate data and follow-up to evaluate the effect of deformity correction on pulmonary function after the kyphoplasty procedure. The current study explores changes of pulmonary function of 30 older women who suffered from OVCFs in the thoracolumbar segment after kyphoplasty. After kyphoplasty was performed on these women, thoracic kyphotic angle, local kyphotic angle, pain scores, and pulmonary function parameters—vital capacity, inspiratory capacity, residual volume, functional residual capacity, total lung capacity, forced vital capacity (FVC), and maximum voluntary ventilation (MVV) were measured. All measurements were taken before, 3 days after, and 1 month after the kyphoplasty. The height of the vertebral body was restored, the local kyphotic angle was improved, and pain scores were significantly decreased after kyphoplasty. FVC and MVV were significantly increased 3 days after the procedures; whereas only MVV had gone on to improve 1 month later. The decreased values of pain scores had a remarkably positive correlation with the percentage of improvement of FVC (r=0.536) and MVV (r=0.614) measured 3 days after kyphoplasty. In patients with OVCFs, kyphoplasty could partially improve their impaired lung function.

Posterior short-segment fixation and fusion in unstable Hangman's fractures.

Study Design. A retrospective study. Objective. To introduce the method of C2–C3 posterior short-segment fixation and fusion in unstable Hangmans fracture and to evaluate the clinical effects. Summary of Background Data. Hangmans fracture can be managed by closed reduction and immobilization. However, surgery is usually preferable in highly unstable cases and in rigid arthrodesis failure. The outcome of surgical treatment for unstable Hangmans fracture has not been thoroughly investigated. Methods. Thirty-five patients with unstable Hangmans fracture were treated using C2–C3 posterior short-segment fixation and fusion. Twenty-six cases used C2–C3 short-segment pedicle screw fixation. Nine cases used both C2 pedicle screw and C3 lateral mass screw short-segment fixation and fusion. C-arm fluoroscopy was used for the whole procedure. Results. All patients were observed for an average of 44 months, ranging from 12 to 78 months. There was no screw loosening or breakage, nor was there any spinal cord or vertebral artery injury intraoperatively. A total of 140 screws were placed, with 70 screws inserted into the C2 pedicle, 52 into the C3 pedicle, and 18 into the C3 lateral mass. Computed tomography scans indicated 9 screws were placed too close to the vertebral artery canal in C2, and 12 screws were too close to the canal in the C3 pedicle, all without clinical consequences. C3 lateral mass screws were placed successfully. Neurologic status improved from C and D to E in all 8 cases. Static and dynamic films demonstrated that fusion was achieved in all cases 6 months after surgery. No graft or plate-related complications were observed in any patients during the entire follow-up period. Conclusion. C2–C3 posterior short-segment fixation and fusion is an effective method for the management of unstable Hangmans fracture, proving its value as a tech-nique for achieving solid bony fusion combined with a low rate of complications.

Quantitative evaluation of the location of the vertebral artery in relation to the transverse foramen in the lower cervical spine.

Study Design. This study assessed the relationship of the vertebral artery and the transverse foramens in the lower cervical spine by computer tomographic angiography (CTA) measurements. Objective. To study the location and the size of the vertebral artery in relation to the transverse foramens in the lower cervical spine. Summary of Background Data. Although many transverse foramen violations had been reported during pedicle screw insertion, the vertebral artery injury seems not as much as expected. The location and size of the vertebral artery in relation to the transverse foramen in the lower cervical spine is not very clear until now. Methods. Fifty patients were selected in our study group. Several parameters were measured on the CTA axial imagines of C3–C7, including the maximal width (W) and the maximal height (H) of transverse foramen, the diameter of vertebral artery (AL), the shortest distance between the vertebral artery and the border of transverse foramen medial (M), lateral (L), anterior (A) and posterior (P), the shortest distance between the vertebral artery and pedicle (h), the area of vertebral artery (AVA) and transverse foramen (AF), and the ratio between AVA and AF (AVA/AF). Results. W, H, and AF increase from C3–C6. M is shorter than L at all measurements. A is shorter than P at C3, C4, and C5, a little bit longer than P at C6 on the contrary. The shortest distance between vertebral artery and pedicle (h) vary from C3–C7, the shortest 0.5 ± 0.2 mm at C3, the longest 7.3 ± 2.7 mm at C7. AVA/AF decrease from C3–C6, 35.7 ± 15.7% at C3 and 27.4 ± 12.8% at C6. Conclusion. Vertebral artery is in the medial part of transverse foramen. There is a relative “abundance space” for vertebral artery in transverse foramen.

Clinical application of C2 laminar screw technique.

C2 laminar screws have become an increasingly used alternative method to C2 pedicle screw fixation. However, the outcome of this technique has not been thoroughly investigated. A total of 35 cases with upper cervical spinal instability undergoing C2 laminar screw fixation were reviewed. All cases had symptoms of atlantoaxial instability, such as craniocervical junction pain, and were fixed with the Vertex cervical internal fixation system. A total of 68 screws were placed and hybrid constructs (a C2 translaminar screw combined with a C2 pars screw) were incorporated in two patients. In this series, there were no intraoperative complications and no cases of neurological worsening or vascular injury from hardware placement. Computed tomographic scans demonstrated a partial dorsal laminar breach in ten patients. None of these resulted in neurological symptoms. None of the patients was found to have a breach of the ventral laminar cortex. All the C2 laminar screws fixations were performed successfully. There was no instability seen on the films with no evidence of hardware failure or screw loosening during the follow-up period in all patients. In conclusion, C2 laminar screw technique is straightforward and easily adopted; it can efficiently and reliably restore upper cervical stability. It is an alternative method to C2 pedicle screw fixation, especially in patients with unilateral occlusion of vertebral artery and pedicle deformity of C2.

Comparison of two techniques for transarticular screw implantation in the subaxial cervical spine.

Study Design Cross-sectional study. Objective To compare 2 techniques of transarticular screw placement in the subaxial cervical spine. Summary of Background Data Transarticular screws have been used as an alternative method to achieve posterior cervical spine stability. According to current studies there are several techniques for the placement of transarticular screws in the subaxial cervical spine; however, there is no study that has compared these techniques. Methods The techniques of transarticular screw placement by Takayasu (group A) and Dalcanto (group B) were used in 8 cervical specimens. The position, number of facet fractures, involvement of the vertebral artery, encroachment of the anterior branches of cervical nerve roots, and instances that failed to go through the facets were observed and analyzed. Results Sixty-four screws were implanted, 32 for group A and the same for group B. Although no facet fractures were seen in group A, there were 10 in group B (&khgr;2=9.6, P<0.01). Eight screws involved the vertebral artery in group A and 0 in group B (&khgr;2=22.3, P<0.001). Eleven anterior branches of lower cervical nerve roots were encroached in group A and 2 in group B (&khgr;2=22.0, P<0.001). No screws failed to go through the facets in group B whereas 2 screws failed in group A, resulting in no significant difference (&khgr;2=0.52, P>0.05). Conclusions There was a high risk of injury to the vertebral artery and anterior branches of the cervical nerve roots if the screws were too long and Takayasu technique was used. However, more facets were fractured if Dalcanto technique was applied.

Radiological studies on the best entry point and trajectory of anterior cervical pedicle screw in the lower cervical spine

ObjectiveTo explore the best entry point and trajectory of anterior cervical transpedicular screws in the lower cervical spine by radiological studies, and provide reference for clinical application.MethodsFifty patients were scanned by computed tomography and confirmed no obvious defect of the cervical spine. On horizontal axis, camber angle (α) and axial length (AL) were measured from C3 to C7. On sagittal view, the cranial or caudal angle (β) and sagittal length (SL) were also measured from C3 to C7. On the sagittal and horizontal planes vertebrae were respectively divided into four areas, ordered 1–4, on the anterior side of the pedicle. The areas and angles of pedicle intersect into the vertebral body were recorded. We inserted six anterior pedicle screws into the lower cervical spine of three patients by this technique.ResultsOn transverse plane, camber angle (α) of C3–C5 increased gradually, while it decreased from C5 to C7. On sagittal view, C3 and C4 pedicles showed cranial tilting, while C5 to C7 were caudally tilted. AL and SL values increased gradually from C3 to C7. The number of the intersections of C3–C7 in each area was also different. Six pedicle screws of three cases were inserted into the lower cervical spine with proper placement and no complications.ConclusionAnterior transpedicular screw (ATPS) is a theoretically feasible option for internal fixation. The technique described in this paper was subsequently used in three patients without complication. Future improvement of ATPS insertion remains necessary for this technically demanding procedure.

A new technique for anterior cervical pedicle screw implantation

Objective:  To introduce and evaluate a new technique, anterior pedicle screw implantation, for anterior cervical reconstruction.

A free‐hand technique for pedicle screw placement in the lower cervical spine

Objective:  To describe a free‐hand method for pedicle screw placement in the lower cervical spine with no intraoperative imaging monitors, and to evaluate the safety of this technique.

The study on comparison of 3 techniques for transarticular screw placement in the lower cervical spine.

Study Design. Prospective comparative study. Objective. To compare 3 techniques for transarticular screw placement in the lower cervical spine. Summary of Background Data. The transarticular screw is found to have satisfactory biomechanical stability. According to current studies, there are several techniques for the placement of transarticular screws in the lower cervical spine. Although several techniques are available for transarticular screw implantation in the lower cervical spine, only a few studies in the literature have been carried out to compare these techniques. Methods. The techniques of transarticular screw placement used by Takayasu (group A), Dalcanto (group B), and Klekamp (group C) were applied in 24 cervical specimens. The facet fractures, the encroachment of the cervical anterior branches of nerve roots and vertebral arteries and the failure of the screws to go through the facets were observed and analyzed. Results. One hundred ninety-two transarticular screws were implanted on both sides in 24 cervical cadavers, 64 for each group. There were 25 splits of inferior facets in group B, 2 splits in group C, and none in group A. Thirty-six screws encroached the vertebral arteries in group A, none in groups B and C. Forty anterior branches of lower cervical nerve roots were involved in group A, 5 in group B, and 3 in group C. Although all screws went through facets in the study except for 5 in group A, there were no significant differences between each group (&khgr;AB2 = 3.33, P > 0.05; &khgr;AC2 = 3.33, P > 0.05). Conclusion. There is a high risk of injury to the anterior branch of the cervical nerve roots and vertebral artery if the screws were too long, and the Takayasu technique was used. However, the rate of facet splitting is high if the Dalcanto technique was applied. Klekamps technique is recommended.

Anterior Transpedicular Screw Technique for Failed Anterior Cervical Internal Fixation in Revision Surgery: a Case Report

Introduction Anterior cervical corpectomy and fusion (ACDF) is a widely used surgical approach for cervical diseases such as cervical trauma, spondylosis, tumor, deformity and degenerative spondylolisthesis. Although successful in achieving good outcomes, drawbacks to the anterior approach include screw and plate loosening, development of pseudarthrosis and lack of bioabsorbability. Zdeblick et al. reported excellent results can be achieved with repeat anterior decompression and autogenous bone-grafting. Wang et al. perform laminoplasty for failed anterior cervical spine surgery. To our knowledge, a cervical anterior transpedicular screw (ATPS) technique has not been used for revision surgery for failed anterior cervical internal fixation.