Posterior Transarticular Screw Research Articles

A Clinical Study to Assess the Efficacy of Anterior Transarticular C1-C2 Screw Fixation for Stabilization of AtlantoAxial Instability

Introduction: The upper cervical spine includes the atlas (C1) and Axis (C2). The anatomy of upper twovertebrae is unique from each other. Atlanto-axial articulation is the most unique, mobile segment of spine,which largely depends on ligamentous supports based on integrity of odontoid for its stability. Historically,atlanto-axial subluxation was treated by reduction and fusion of C1-C2 joint. However, High riding vertebralartery precludes the placement of posterior trans-articular screw, which is liable to injury during screwplacement. Socomputed tomography scans can be used to evaluate the risk of “high riding” vertebral arteryduring the management of atlanto-axial subluxation. Hence, anterior trans-articular screw fixation techniqueavoids the course of high riding vertebral artery.Material and Method: Nine patients underwent NCCT cervical spine with 3-D reconstruction and clinicalevaluation of pain was done by recording the VAS score done pre operatively and after surgery.Results: All surgical cohorts underwent anterior C1-C2 fixation with an average follow up for 24 months.All patients were assessed as per fixed protocol of our local hospital guidelines of orthopaedics department.Pain score was clinically evaluated by VAS score before and after surgery yielding 90% excellent result.Conclusion: Anterior Trans-articular C1-C2 screw fixation isa minimally invasive technique with less bloodloss, shorter skins car and faster post-operative recovery. It is an appropriate technique for stabilization ofAtlanto-Axial instabilities.

Minimally Invasive Posterior Transarticular Stand-Alone Screw Instrumentation of C1–C2 Using a Transmuscular Approach: Description of Technique, Results and Comparison with Posterior Midline Exposure

The aim of this study was to compare the feasibility, safety, and fusion results of posterior transarticular stand-alone screw (SAS) instrumentation of C1-C2 with a minimally invasive technique to those of a posterior midline exposure. Between 2008 and 2016, 164 patients underwent surgical treatment for traumatic injuries to the upper cervical vertebrae at our institution. We included 38 patients (27 men and 11 women; age range, 17-81 years) in the study. The posterior midline approach (PMA) group (23 patients) included patients who underwent surgery by means of a conventional midline incision after percutaneous screw insertion. The transmuscular approach (TMA) group (15 patients) included patients who underwent SAS fixation by use of a minimally invasive technique. The mean follow-up period was 58 months (range, 12-118 months). Statistical analysis revealed that the operative time, blood loss volume, and severity of postoperative pain were lower in the TMA group. No significant excess of radiation exposure to the surgical team and the patients occurred in TMA group compared with the PMA group. C1-C2 fusion was observed in 37 patients. Stable fibrous fusion between the C1 and C2 vertebrae was found in 1 patient. A minimally invasive technique by use of a paravertebral transmuscular approach provides an alternative to routine posterior transarticular SAS fixation of C1 and C2 through a posterior midline approach. The minimally invasive technique reduces the duration of surgery and the volume of blood loss, decreases the severity of postoperative pain, and does not increase the amount of radiation exposure for the surgical team and the patient.

A Comparison of the Long-Term Results of Posterior Transarticular Stand-Alone Screw Instrumentation and Magerl Technique in Patients with Traumatic Atlantoaxial Instability: Mean 5-Year Follow-Up Study with Radiological and Patient-Rated Outcomes Assessments

To perform a radiological analysis of the degeneration of C1-C2 joints after C1-C2 transarticular fixation (TAF) and compare the long-term results of a routine Magerl technique (RMT) to a posterior transarticular C1-C2 stand-alone screw instrumentation (SAS) application. A total of 40 patients (26 men and 14 women) were included in the present retrospective observational cohort study. The mean follow-up period was 61.7 months (range, 11-118). The mean patient age at the baseline examination was 48.4 years (range, 22-82). Of the 40 patients, 11 were included in the RMT group and 29 in the SAS group. The structure of 80 atlantoaxial joints was analyzed, with grade 4 degenerative changes observed in 57 joints (71.3%). Of the 40 analyzed atlanto-odontoid joints, grade 4 degenerative changes were revealed in 18 joints (45%). C1-C2 bone fusion was observed in 38 patients (95%) and stable fibrous fusion in 2 patients (5%). No cases of C1-C2 nonunion were revealed. No statistically significant differences in the frequency of C1-C2 fracture consolidation or C1-C2 fusion were revealed between the RMT and SAS groups. The application of cortical lag screws in TAF might result in stable atlantoaxial joint fusion formation without joint curettage. Atlanto-odontoid joint fusion was also observed after C1-C2 TAF. The application of cortical lag screws for bilateral fixation using the SAS technique resulted in C1-C2 fusion in 93.1% of cases, comparable to the results with the Magerl technique.

Anterior retropharyngeal plate screw fixation with bilateral anterior transarticular screws for odontoid fractures ... a new comprehensive technique

Introduction: A certain group of odontoid fractures (Anderson and D’ Alonzo Type-2) are usually offered surgical treatment. Common surgical option is an anterior odontoid screw. Some of the fractures are not suitable for anterior odontoid screw (anterior oblique, displaced distal fragments and those with atlantoaxial instability) and these are usually offered posterior transarticular screws (Magerl’s) or posterior atlantoaxial screw rod/plate fixation (Goel-Harms technique). Posterior surgery involves atlantoaxial fixation with an indirect attempt to reduce and fuse the fracture . Posterior surgery has a risk of injury to the vertebral arteries, hemorrhage from the paravertebral venous plexus and the C2 root ganglion.Methods: A direct anterior submandibular retropharyangeal approach with open reduction and fixation (ORIF) using a customized variable screw placement (VSP) plate was used to realign and fix the fracture fragments in compression mode under direct vision. Twenty patients of type-II odontoid fractures (unsuitable for anterior odontoid screw) underwent an anterior retropharyngeal approach with anterior variable screw position (VSP) plate and screw fixation and eight amongst them, who had associated atlantoaxial instability underwent additional bilateral anterior transarticular screws.Results: All patients treated by this technique had 100% fracture site bone union without any implant failure. Longest follow-up has been for 3 years.Conclusion: Anterior retropharyangeal approach allows direct fracture fragment realignment under vision with an opportunity to fix in compression mode using the VSP plate, which ensures early fusion across the type-II odontoid fracture. Any associated instability can be treated by additional bilateral anterior transarticular screws. The approach is simple and safe without any risk to the vertebral arteries and biomechanically appealing.

Magerl technique for children atlantoaxial rotatory subluxation

Objective To discuss the feasibility and prognosis of magerl technique for children. Atlantoaxial Rotatory Subluxation. Methods 63 patients with Atlantoaxial Rotatory Subluxation were treated in our hospital, and 16 of whom were treated with bilateral C1, 2 posterior transarticular screw fixation and fusion. All cases aged from 8 to 14, with an average age of 11±2.3 years old. According to Fielding classification, 10 cases were in type II, and 6 in type III. 1 patient showed dizziness, 11 patients showed obvious appearance of deviation of head and neck; 14 patients showed varying degrees of occipito-cervical pain, and one patient showed incomplete paralysis. All patients had undergone Halo traction, then the Magerl surgery for atlantoaxial fixation fusion. Through follow-up and photograph of atlantoaxial mouth opening, lateral cervical X-ray and atlantoaxial 3D CT, the screw position and bone graft fusion were evaluated. The clinical and radiological outcomes were evaluated according to the Symon and Lavender clinical standard, the imaging index space available for the cord (SAC), and the atlas-dens interval (ADI). Results All cases were followed up for 3 to 98 months (mean 38±14.6 months). All patients had completed the bilateral UCSS screw fixation, and the symptoms were improved significantly, without neurological symptoms aggravated or complications such as neurovascular injury. All UCSS screw position through the atlantoaxial joint was accurate, without atlanto occipital joint activity limitation. All patients got bony fusion 3 to 6 months post-operation. The clinical recovery rate was 93.8%. The SAC of C1,2 segment increased by 6.06±1.29 mm postoperatively, which showed a significant difference compared with preoperative SAC. The SAC at the latest follow-up was 15.31±0.79 mm, showing no significant difference compared with that just postoperatively. The ADI at one month post-operatively decreased by 5.75±1.53 mm, showing a significant difference compared with preoperative SAC. The ADI at the latest follow-up was 1.94±0.57 mm, showing no significant difference compared with that just postoperatively. Conclusion Preoperative Halo-traction combined with Magerl surgery in treatment of children with atlantoaxial rotatory subluxation is a safe and effective method. Key words: Atlanto-axial joint; Dislocations; Child; Internal fixators; Spinal fusion

Posterior C1-C2 transarticular screw fixation for atlantoaxial instability assisted by intraoperative 3-dimensional fluoroscopy-based navigation

To assess the feasibility, efficacy and indication of posterior C1-C2 transarticular screw fixation for atlantoaxial instability assisted by intraoperative 3-dimensional fluoroscopy-based navigation. From November 2005 to October 2012, 58 patients with atlantoaxial instability underwent posterior C1-C2 transarticular screw fixation assisted by intraoperative 3-dimensional fluoroscopy-based navigation. Those with excellent atlantoaxial reduction and no need for decompression underwent percutaneously minimally invasive procedures. Operative duration, blood loss volume, reduction of atlantoaxial joints and postoperative neurovascular complications were recorded. Screw positions were studied by postoperative computed tomography (CT) and divided into 3 categories. The follow-up period was at least 3 months. Local symptoms (assessed by visual analogue scale (VAS) score), neurological conditions (Nurick classification) and bone graft fusion were evaluated. Among them, the procedure was either open surgery (n = 51) or percutaneously minimally invasive surgery (n = 7). A total of 111 screws were placed satisfactorily. Five patients underwent only unilateral C1-C2 transarticular screw fixation. No severe complications were encountered. The mean operative duration was 202.2 ± 54.2 minutes and the average volume of blood loss 412.6 ± 281.2 ml. And the values were comparable to those for the traditional fluoroscopy-guided free-hand procedures. No statistical significance existed between open and percutaneously minimally invasive procedures in operative duration, blood loss volume and precision of screw placement. The patients with incompletely reduced C1-C2 dislocation had comparable clinical outcomes with those with complete reduction. After a 3-month follow-up, all of them showed significant improvements of local symptoms. VAS score decreased from 4.5 ± 1.3 preoperatively to 0.7 ± 0.8 postoperatively while the Nurick classification improved from 2.4 ± 1.1 to 0.6 ± 1.0. And bone graft fusion was satisfactory. Posterior C1-C2 transarticular screw fixation for atlantoaxial instability assisted by intraoperative 3-dimensional fluoroscopy-based navigation is both feasible and safe. Combined with minimally invasive techniques, this procedure may achieve greater precision and minimal invasion.

Treatment Algorithm for Dens Fractures: Non-Halo Immobilization, Anterior Screw Fixation, or Posterior Transarticular C1-C2 Fixation

The appropriate treatment of dens fractures is unclear. We established a staged treatment protocol for dens fractures and conducted a prospective study to evaluate the outcome of treatment based on this protocol. We prospectively evaluated sixty-nine consecutive patients who presented to our institution with a dens fracture. The mean duration of follow-up was 9.7 months (range, six to fifty-eight months). Fractures were categorized as stable or unstable. Stable fractures were treated by immobilization in a rigid collar. Patients seventy-five years or older with unstable fractures, patients with a neurological deficit, and patients with Anderson and D'Alonzo type-III fractures underwent posterior transarticular C1-C2 stabilization. Unstable fractures in patients younger than seventy-five years were stabilized with direct anterior screw fixation. Thirty-one patients were treated with a Philadelphia collar, twenty-five with posterior transarticular fixation, and thirteen with direct anterior screw fixation. Fracture-healing or solid fusion of C1-C2 was documented in sixty-eight of sixty-nine treated patients at final follow-up. The remaining patient had a stable nonunion of the dens. Secondary procedures were performed in five patients. Our treatment algorithm based on dens fracture type, fracture stability, and patient age was associated with a high success rate. Evaluating fracture stability is crucial when considering nonoperative treatment. External stabilization with a rigid cervical collar was adequate for stable fractures of the dens and was associated with a high healing rate. Posterior transarticular screw fixation of C1-C2 was associated with a high success rate, including in elderly patients. Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Commentary: Anterior atlantoaxial transarticular screws: should this be the preferred atlantoaxial fixation technique?

Commentary on Xu H, Chi YL, Wang XY, et al. Comparison of the anatomic risk for vertebral artery injury associated with percutaneous atlantoaxial anterior and posterior transarticular screws. Spine J 2012;12:656–62 ( in this issue ).

Comparison of the anatomic risk for vertebral artery injury associated with percutaneous atlantoaxial anterior and posterior transarticular screws

As a minimally invasive spine surgery, percutaneous atlantoaxial fixation techniques using anterior transarticular screw (ATS) and posterior transarticular screw (PTS) have promising clinical results. However, transarticular screw fixation is technically demanding and carries a potential risk of iatrogenic vertebral artery (VA) injury. There were no available data comparing the anatomic risk of VA injury associated with these screws. To evaluate the trajectories of percutaneous atlantoaxial ATS and PTS through three-dimensional (3D) computerized tomography. To compare the anatomic risk of VA injury between percutaneous ATS andPTS. Sixty patients ranged in age from 19 to 75 years (mean, 45.08 years) and included 35 men and 25 women. Image measurement of C2 isthmus height and C2 isthmus width and the distance between the medial-most superior articular facet to the medial-most edge of the VA groove of the C2 (D). Sixty consecutive patients (in total) with lower cervical lesions were evaluated through 3D images reconstructed by a rapid 3D system. The maximum possible diameters of the percutaneous atlantoaxial ATS and PTS trajectories were compared and examined. Mean, range, and standard deviations for each type of screw, for left and right trajectories, and for men and women were calculated from 120 percutaneous atlantoaxial ATS and PTS measurements through SPSS. The maximum mean diameter differed significantly between the trajectories of 120 percutaneous atlantoaxial ATS and PTS. For screw trajectories ≤3.5 mm in diameter, 19.2% of the PTS trajectories were judged as risky, whereas all the anterior ones were judged as safe. From an anatomic perspective, percutaneous ATS fixation poses less anatomic risk of VA injury than percutaneous PTS fixation. As an alternative surgical therapy for atlantoaxial subluxation, percutaneous ATS fixation may play a more important role in the future.

Tuberculous altantoaxial subluxation: a case report with review of literature

Involvement of upper cervical and craniovertebral junction is rare but might lead to lethal consequences if the diagnosis is delayed. We present a case of atlantoaxial joint tuberculosis, resulting in gross instability of the joint. The patient was treated with antitubercular medication combined with posterior decompression and transarticular screw fixation. Patient improved neurologically, and clinical and radiological improvements were maintained at the latest follow-up of 2 years.

Modified Brook's technique combined with posterior C1-2 transarticular screw fixation to treat old odontoid fractures

Objective To explore clinical efficacy of modified Brook's technique combined with posterior C1-2 transarticular screw fixation in the management of old odontoid fractures. Methods From January 2007 to June 2010,18 patients with old odontoid fractures were treated surgically by modified Brook' s technique combined with posterior C1-2 transarticular screw fixation in our unit.They were 12 males and 6 females with an average age of 41.8 years (from 21 to 68 years).By the Anderson-D'Alonzo classification,there were 15 cases of type Ⅱ and 3 cases of type Ⅲ.Among them,4 patients were complicated with brain injury and 3 patients with breast injury.The duration from injury to operation averaged 18.4 months,ranging from 41 days to 13 years. Results The average operative tine was 125 minutes (from 100 to 180 minutes) and the average blood loss was 250 mL (from 100 to 600 mL) in this series.No intraoperative injury occurred to the vertebral artery or to the spinal cord.All the patients were followed up for an average of 30.2 months (from 14 to 50 months).By the Mayo (McGrory) evaluation system,the postoperative clinical symptoms were rated as excellent in 7 cases,good in 9 cases and fair in 2 cases,with a good to excellent rate of 88.9％.The mean Visual Analogue Scale (VAS) score was improved significantly from preoperative 1.4 ±0.8 points to postoperative 5.3 ± 1.2 points ( t =15.853,P =0.000).The 6 patients complicated with neural injury obtained improvement by at least one grade.All the patients achieved bone fusion at 6 months postoperation,and no loosening,displacement or breakage of the screws was found in the follow-up.Conclusion As Modified Brook' s technique combined with posterior C1-2 transarticular screw fixation is a safe and reliable treatment of atlantoaxial instability,it can serve as a surgical option for old odontoid fractures. Key words: Bone nails; Dens axis; Fracture fixation; Spinal fusion

Dominant vertebral artery injury during posterior atlantoaxial transarticular screw fixation in a juvenile rheumatoid arthritis patient with atlantoaxial subluxation.

Many authors have reported on iatrogenic vertebral artery (VA) injury, but, to our knowledge, this is the first report of a dominant VA injury with compensatory blood flow from the hypoplastic VA. A 23-year-old woman with juvenile rheumatoid arthritis and atlantoaxial subluxation sustained injury to her dominant VA after occipitocervical fusion using transarticular screws. This did not result in lethal consequences due to compensation from her hypoplastic contralateral VA. Postoperative angiography, however, illustrated occlusion of the dominant left side, while the hypoplastic VA of the right side was enlarged. The patient experienced vertigo and loss of consciousness several times during rehabilitation. At the 4-year follow-up exam, bony fusion was observed, with no neurological deficits or correction loss. She had had no episodes of unconsciousness and no recurrence of any symptoms over the previous 3 years.

Anatomical considerations for the placement of cervical transarticular screws

the object of this study was to determine the safe screw placement technique for cervical transarticular screw fixation. twenty cadaveric adult cervical spines were studied. All soft tissues surrounding the cervical spinal nerves from C-2 to T-1 were dissected carefully to expose the lateral mass, facet joint, transverse process, vertebral artery (VA), and spinal nerves (ventral and dorsal rami). After the proper entrance and exit points for the transarticular screws were determined, posterior transarticular screw implantation was performed under direct visualization from C2-3 to C5-6. A CT scan was performed to check the screw placement. The angle and length of the transarticular screw trajectory, the distance between the tip of the screw and the VA, and the sagittal safety angle were measured on the CT scan. Statistical analysis was performed using ANOVA (p < 0.05). Sagittal and axial orientations of transarticular screws were carefully analyzed. there was no nerve or artery impingement or penetration. The average caudal angle of the screws in the sagittal plane was 37.3° ± 5.0° and the lateral angle in the axial plane was 16.6° ± 4.6°. The average distance between the tip of the screw and the VA (the posterior border of the VA foramen) was 5.8 ± 1.5 mm. The average sagittal safety angle was 41.9° ± 5.6°. No difference was observed according to the vertebral level. The average bone purchase was 18.7 ± 1.4 mm. Bone purchase was significantly greater at C2-3 (23.2 ± 1.6 mm) than at C3-4 through C5-6 (17.2 ± 1.3 mm, p < 0.05). this study establishes anatomical guidelines to allow for safe cervical transarticular screw insertion. The starting point of transarticular screws should be 1 mm medial to the midpoint of the lateral mass. The "ideal" drilling angle is approximately 37° in the inferior direction and 16° in the lateral direction for the C2-3 through the C5-6 levels. The screw should be directed as laterally as possible in the axial plane without causing the lateral mass to fracture and as caudally as the occipital bone permits in the sagittal plane. The ideal screw size would be 3.5 mm in diameter and 18 mm in length.

Biomechanical evaluation of stability and three-dimensional movements of the atlantoaxial joint after artificial atlanto-odontoid joint arthroplasty

To investigate the stability and three-dimensional movements of the atlantoaxial joint after artificial atlanto-odontoid joint (AAOJ) arthroplasty. Ten sets of AAOJ implanted in bony specimens from 10 adults were used to test the pull-out strength of the atlas-axis components with a MTS858 Mini Bionix machine. Another twelve human cadaveric specimens including C(0)-C(4) were used to evaluate the three-dimensional movements of C(1)-C(2) under five different conditions in sequence, that is, the complete specimen, anterior decompression, posterior transarticular screws fixation, AAOJ arthroplasty and fatigue test. There were significant differences between atlas and axis components in the maximum pull-out strength and trajectory length, however the yield length was not significantly different. The maximum pull-out strength of the atlas and axis was positively correlated with trajectory length (r(1)= 0.880, P < 0.05) and yield length (r(2)= 0.606, P < 0.05), respectively. After AAOJ arthroplasty, the range of movement (ROM) with respect to rotation and the neutral zone of the atlantoaxial joint were close to normal (P > 0.05), but the ROM in flexion-extension and lateral bending was significantly smaller compared with the specimens which underwent anterior decompression (P < 0.05). No abrasion and abnormal mobilization were observed after 2000 cycles of flexion, extension, lateral bending and axial rotation in the fatigue test. The self-designed AAOJ has excellent biomechanical performance, and AAOJ arthroplasty can restore excellent instant stability and preserve the movement of the atlantoaxial joint.

A biomechanical comparison between fixation of cervical transfacet pedicle screws and standard pedicle screws.

Objective To compare biomechanical pullout strength of cervical transfacet pedicle screws to that of standard pedicle screws. Methods Ten fresh human cadaveric cervical spines were harvested. On one side, transfacet pedicle screws were placed at the C3,4, C5,6, and C7T1 levels. On the other side, pedicle screws were, placed at the C3, C5, and C7 levels. The screw insertion technique at each level was randomized for right or left. The starting point for the transfacet pedicle screw insertion was about located at the midpoint of the inferolateral quadrant of the lateral mass and the direction of the screw was about 50° caudally in the sagittal plane and about 45° medially in the axial plane. Screws were placed across the facet joint and the pedicle into the body of the caudal vertebra. The entry points for pedicle screw was located at the midpoint of the superolateral quadrant of the lateral mass and the direction of the screw was about 45° toward the midline in the transverse plane and toward the upper third of the vertebral body in the sagittal plane. The pedicle screws were oriented along the axis of the pedicle in an effort to avoid violations of the cortical wall. All the screw insertions were based on direct observation and the CT scan on the pedicles. After screw placement, axial pullout testing was performed. Results The mean pullout strength for the transfacet pedicle screws was (694±42) N. This compares with (670±36) N for the pedicle screws (P< 0.05). The greatest difference at a single level in pullout strength was observed at the C5,6 level, with a mean difference of 38 N. Conclusion Transfacet pedicle screws exhibited statistically greater pullout strength to pedicle screws. At each level the transfacet pedicle screws exhibited greater pullout strength than the pedicle screws. Posterior transarticular pedicle screw fixation in the cervical spine affords an alternative to standard screw placement for plate fixation and cervical stabilization. Key words: Cervical vertebrae; Internal fixators; Biomechanics

173. Unilateral Posterior Atlantoaxial Transarticular Screw Fixation in Patients with Atlantoaxial Instability: Comparison with Bilateral Method

BACKGROUND CONTEXT: Simultaneous bilateral posterior transarticular screw fixation (TAF) and bone grafting with wire loop provides immediate, rigid internal fixation for atlantoaxial instability (AAI). It is the most effective biomechanical technique to attain C1-2 stability, and is superior to conventional wiring methods by virtue of more rigid fixation. Solid atlantoaxial fusion has been reported in 80 to 100% of patients who were treated with this method. However, bilateral TAF across the C1-2 may be contraindicated or impossible in up to 20% of patients because of its structural disfigurements such as anomalous course of the vertebral artery (VA), comminuted fractures of C-1 or C-2, or other pathological processes.

SAFE ANGLE SCOPE FOR POSTERIOR ATLANTO-OCCIPITAL TRANSARTICULAR SCREW FIXATION

To study the technical parameters related to, and explore the clinical significance of, posterior atlanto-occipital transarticular screw fixation. Posterior implantation of Kirschner wires via the atlanto-occipital joint was performed on 20 dry bone specimens with complete atlanto-occipital joints. The angle of the Kirschner wire was measured on a postimplantation x-ray. Three-dimensional computed tomographic reconstruction of the atlanto-occipital joint of 30 healthy adults was performed to measure the simulative safety range for screw placement in posterior atlanto-occipital transarticular screw fixation. The procedure was then conducted on 12 fresh cadaver occipitocervical specimens. X-rays and 3-dimensional computed tomographic reconstruction were performed postsurgery to verify exact screw positioning. The ideal angles for screw placement were cephalocaudal angle in the sagittal plane of 53.3 +/- 3.4 degrees, mediolateral angle in the coronal plane of 20.0 +/- 2.6 degrees, a maximum allowable cephalocaudal angle of 74.6 +/- 2.8 degrees (67.9-80.5 degrees), a minimum allowable cephalocaudal angle of 24.9 +/- 1.9 degrees (22.1-29.4 degrees), a maximum allowable mediolateral angle of 40.5 +/- 2.9 degrees (31.1-49.4 degrees), and a minimum allowable mediolateral angle of 0.7 +/- 1.6 degrees (-4.1-5.9 degrees). Surgery simulation in the fresh cadaver specimens indicated that this safe scope is reliable. There is a safe scope for the angle of the screw placement in posterior atlanto-occipital transarticular screw fixation. Posterior transarticular screw fixation can be safely performed for occipitocervical fusion fixation when utilizing careful screw placement.

Atypische dislozierte Densfraktur Typ II mit rotatorischer atlantoaxialer Luxation nach Reitunfall

We present a rare case of a combined dislocated odontoid dens fracture type II (Anderson/D'Alonzo) and rotational atlantoaxial luxation in a 15-year-old girl who was involved in a riding accident.She fell off her horse after it had stopped suddenly, losing consciousness for a few minutes. At presentation in the hospital, she had no complaints other than limited, painful neck movement. Radiologically, a posterior dislocation of an odontoid type II fracture (Anderson/D'Alonzo) was found. Computed tomography reconstruction demonstrated a rotational, hooklike fixed luxation of the left atlantoaxial facet joint. Manual repositioning after application of a cervical collar failed. Therefore, operative treatment was indicated for this highly unstable fracture. Posterior transarticular atlantoaxial screw fixation according to Magerl was performed; an iliac corticocancellous bone graft was harvested and shaped to conform to the posterior processes of C1 and C2. Additionally a hook-claw atlas fixation of C1 was done.To our knowledge, this is the first case of adolescent atlantoaxial cervical spine trauma in combination with an odontoid fracture and fixed rotational luxation reported in literature.

One stage internal fixation with posterior transarticular screws and anterior plating for treatment of lower cervical spine fractures and dislocations

Objective To evaluate the effects of one stage internal fixation with posterior transartitular screws and anterior plating for the treatment of lower cervical spine fractures and dislocations.Methods From October 2005 to May 2007, 12 patients with fractures and dislocations of lower cervical spine were treated by one stage anterior-posterior internal fixation. Posterior transarticular screw fixation combined with anterior decompression and bone graft and anterior plating were applied for only dislocations.Anterior decompression and bone graft and anterior plating combined with posterior transarticular screw fixation were applied for the fractures and dislocations. The zygapophysial joints were fused. Results All patients were followed up for 6 to 21 (average, 14. 8) months. No loosening of the transarticular screw or nerve-vessel complication was found. Intervertebral and zygapophysial joints all got bony healing. Conclusion One stage internal fixation with posterior transarticular screws and anterior plating is an ideal method of treating lower cervical fractures and dislocations, having the advantages of simple and safe procedures, reliable fixation and a high rate of bone fusion. Key words: Cervical vertebrate; Fractures; Dislocations; Fracture fixation, internal; Screw

Biomechanical Comparison of C1–C2 Posterior Arthrodesis Techniques

Biomechanical comparison of 5 atlantoaxial posterior arthrodesis techniques. To assess the relative value of different posterior wire constructs when one or two transarticular screws are used. A combination of Gallie or Brooks techniques and 2 posterior transarticular screws has been shown to be effective for atlantoaxial arthrodesis. Anatomic constraints may preclude the insertion of a transarticular screw unilaterally or bilaterally. Ten adult human cadaveric upper cervical spine specimens were used. The specimens were tested intact, after odontoidectomy and transverse and capsular ligament section and after stabilization with each of the 5 techniques: Brooks-Jenkins cable fixation, Brooks-Jenkins with unilateral transarticular screw, Gallie posterior wire construct with unilateral transarticular screw, Brooks-Jenkins with bilateral screws, and Gallie with bilateral screws. Pure moments were applied in flexion-extension, lateral bending, and torsion within physiologic limits (<1.5 Nm). In flexion-extension and lateral bending, the range of motion (ROM) and neutral zone (NZ) increased significantly after the specimens were injured as compared with intact spines (P < 0.001). After stabilization, the ROM and NZ were significantly lower than in injured and intact spines in all motions (P < 0.01) except lateral bending in the intact spine. Among the 5 instrumented techniques, the ROM for the Gallie construct with 1 screw was significantly higher than for the Brooks-Jenkins construct with 1 or 2 screws in flexion-extension (P < 0.05). In axial torsion, the Gallie construct with 1 screw displayed a larger NZ and ROM than any of the other 4 constructs (P < 0.05). Gallie or Brooks-Jenkins cable fixation alone may not be adequate for atlantoaxial arthrodesis. If 2 supplemented transarticular screws can beinserted, there is no difference between the Gallie or Brooks techniques. If only a single screw can be inserted, the Brooks-Jenkins technique is recommended rather than a Gallie technique.