Weihu Ma

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.

Short‐term clinical observation of the Dynesys neutralization system for the treatment of degenerative disease of the lumbar vertebrae

Objective:  To explore the safety and short‐term efficacy of the posterior approach of the Dynesys dynamic neutralization system for degenerative disease of the lumbar vertebrae.

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.

Accuracy and complications associated with the freehand C-1 lateral mass screw fixation technique: a radiographic and clinical assessment.

OBJECT The aims of this study were to evaluate a large series of posterior C-1 lateral mass screws (LMSs) to determine accuracy based on CT scanning findings and to assess the perioperative complication rate related to errant screw placement. METHODS Accuracy of screw placement was evaluated using postoperative CT scans obtained in 196 patients with atlantoaxial instability. Radiographic analysis included measurement of preoperative and postoperative CT scans to evaluate relevant anatomy and classify accuracy of instrumentation placement. Screws were graded using the following definitions: Type I, screw threads completely within the bone (ideal); Type II, less than half the diameter of the screw violates the surrounding cortex (safe); and Type III, clear violation of transverse foramen or spinal canal (unacceptable). RESULTS A total of 390 C-1 LMSs were placed, but 32 screws (8.2%) were excluded from accuracy measurements because of a lack of postoperative CT scans; patients in these cases were still included in the assessment of potential clinical complications based on clinical records. Of the 358 evaluable screws with postoperative CT scanning, 85.5% of screws (Type I) were rated as being in the ideal position, 11.7% of screws (Type II) were rated as occupying a safe position, and 10 screws (2.8%) were unacceptable (Type III). Overall, 97.2% of screws were rated Type I or II. Of the 10 screws that were unacceptable on postoperative CT scans, there were no known associated neurological or vertebral artery (VA) injuries. Seven unacceptable screws erred medially into the spinal canal, and 2 patients underwent revision surgery for medial screws. In 2 patients, unilateral C-1 LMSs penetrated the C-1 anterior cortex by approximately 4 mm. Neither patient with anterior C-1 penetration had evidence of internal carotid artery or hypoglossal nerve injury. Computed tomography scanning showed partial entry of C-1 LMSs into the VA foramen of C-1 in 10 cases; no occlusion, associated aneurysm, or fistula of the VA was found. Two patients complained of postoperative occipital neuralgia. This was transient in one patient and resolved by 2 months after surgery. The second patient developed persistent neuralgia, which remained 2 years after surgery, necessitating referral to the pain service. CONCLUSIONS The technique for freehand C-1 LMS fixation appears to be safe and effective without intraoperative fluoroscopy guidance. Preoperative planning and determination of the ideal screw insertion point, the ideal trajectory, and screw length are the most important considerations. In addition, fewer malpositioned screws were inserted as the study progressed, suggesting a learning curve to the technique.

Function-preserving reduction and fixation of unstable Jefferson fractures using a C1 posterior limited construct.

Study Design: This is a retrospective, clinical, and radiologic study of posterior reduction and fusion of the C1 arch in the treatment of unstable Jefferson fractures. Objective: The aim of the study was to describe a new motion-preserving surgical technique in the treatment of unstable Jefferson fracture. Summary of Background Data: The management of unstable Jefferson fractures remains controversial. The majority of C1 fractures can be effectively treated nonoperatively with external immobilization unless there is an injury to the transverse atlantal ligament (TAL). Conservative treatment usually involves immobilization for a long time in Halo vest, whereas surgical intervention generally involves C1–C2 fusion, eliminating the range of motion of the upper cervical spine. We propose a novel method for the treatment of unstable Jefferson fractures without restricting the range of motion. Methods: A retrospective review of 12 patients with unstable C1 fractures between April 2008 and October 2011 was performed. They were treated by inserting bilateral posterior C1 pedicle screws or lateral mass screws interconnected by a transversal rod to achieve internal fixation. There were 8 men and 4 women, with an average age of 35.6 years (range, 20–60 y). Presenting symptoms included neck pain, stiffness, and decreased range of motion but none had neurological injury. Seven patients had bilateral posterior arch fractures associated with unilateral anterior arch fractures (posterior 3/4 Jefferson fracture, Landells type II), and 5 had unilateral anterior and posterior arch fractures (half-ring Jefferson fracture, Landells type II). Seven patients had intact TAL, and 5 patients had fractures and avulsion of the attachment of TAL (Dickman type II). Results: A total of 24 screws were inserted. Five cases had screws placed in the lateral mass: 3 because of posterior arch breakage, and 2 because the height of the posterior arch at the entry point was <4 mm. The remaining 7 cases had pedicle screw fixation. One patient had venous plexus injury during exposure of lower margin of the posterior arch; however, successful hemostasis was achieved with Gelfoam. Postoperative x-ray and computed tomography scan showed partial breach of the transverse foramen caused by a screw in 1 case, and breach of the inner cortex of the pedicle caused by screw displacement in 1 case; however, no spinal cord injury or vertebral artery injury was found. The remaining screws were in good position. Patients were followed up for 6–40 months (average, 22 mo). All cases had recovery of range of motion of the cervical spine to the preinjury level by 3–6 months after surgery, with resolution of pain. At 6 months follow-up, plain radiographs and computed tomography scans revealed satisfactory cervical alignment, no implant failure, and satisfactory bony fusion of the fractures; no C1–C2 instability was observed on the flexion-extension radiographs. Conclusions: C1 posterior limited construct is a valid technique and a feasible method for treating unstable Jefferson fractures, which allows preservation of the function of the craniocervical junction, without significant morbidity.

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.

The Anatomic Study on Replacement of Artificial Atlanto-odontoid Joint through Transoral Approach

SummaryIn order to provide anatomical basis for transoral approach (TOA) in dealing with the ventro lesions of craniocervical junction, and the design and application of artificial atlanto-odontoid joint, microsurgical dissecting was performed on 8 fresh craniocervical specimens layer by layer through transoropharyngeal approach. The stratification of posterior pharyngeal wall, course of vertebral artery, adjacent relationship of atlas and axis and correlative anatomical parameters of replacement of artificial atlanto-odontoid joint were observed. Besides, 32 sets of atlanto-axial joint in adults’ fresh bony specimens were measured with a digital caliper and a goniometer, including the width of bony window of anterior arch of atlas, the width of bony window of axis vertebra, the distance between superior and inferior two atlas screw inserting points, the distance between two axis screw inserting points etc. It was found that the width of atlas and axis which could be exposed were 40.2±3.5 mm and 39.3±3.7 mm respectively. The width and height of posterior pharyngeal wall which could be exposed were 40.1±5.2 mm and 50.2±4.6 mm respectively. The distance between superior and inferior two atlas screw inserting points was 28.0±2.9 mm and 24.0±3.5 mm respectively, and the distance of bilateral axis screw inserting points was 18.0±1.2 mm. The operative exposure position through TOA ranged from inferior part of the clivus to the superior part of the C3 vertebral body. Posterior pharyngeal wall consisted of 5 layers and two interspaces: mucosa, submucosa, superficial muscular layer, anterior fascia of vertebrae, anterior muscular layer of vertebrae and posterior interspace of pharynx, anterior interspace of vertebrae. This study revealed that it had the advantages of short operative distance, good exposure and sufficient decompression in dealing with the ventro lesions from the upper cervical to the lower clivus through the TOA. The replacement of artificial atlanto-odontoid joint is suitable and feasible. The design of artificial atlanto-odontoid joint should be based on the above data.In order to provide anatomical basis for transoral approach (TOA) in dealing with the ventro lesions of craniocervical junction, and the design and application of artificial atlanto-odontoid joint, microsurgical dissecting was performed on 8 fresh craniocervical specimens layer by layer through transoropharyngeal approach. The stratification of posterior pharyngeal wall, course of vertebral artery, adjacent relationship of atlas and axis and correlative anatomical parameters of replacement of artificial atlanto-odontoid joint were observed. Besides, 32 sets of atlanto-axial joint in adults’ fresh bony specimens were measured with a digital caliper and a goniometer, including the width of bony window of anterior arch of atlas, the width of bony window of axis vertebra, the distance between superior and inferior two atlas screw inserting points, the distance between two axis screw inserting points etc. It was found that the width of atlas and axis which could be exposed were 40.2±3.5 mm and 39.3±3.7 mm respectively. The width and height of posterior pharyngeal wall which could be exposed were 40.1±5.2 mm and 50.2±4.6 mm respectively. The distance between superior and inferior two atlas screw inserting points was 28.0±2.9 mm and 24.0±3.5 mm respectively, and the distance of bilateral axis screw inserting points was 18.0±1.2 mm. The operative exposure position through TOA ranged from inferior part of the clivus to the superior part of the C3 vertebral body. Posterior pharyngeal wall consisted of 5 layers and two interspaces: mucosa, submucosa, superficial muscular layer, anterior fascia of vertebrae, anterior muscular layer of vertebrae and posterior interspace of pharynx, anterior interspace of vertebrae. This study revealed that it had the advantages of short operative distance, good exposure and sufficient decompression in dealing with the ventro lesions from the upper cervical to the lower clivus through the TOA. The replacement of artificial atlanto-odontoid joint is suitable and feasible. The design of artificial atlanto-odontoid joint should be based on the above data.