Posterior Screw Fixation Research Articles

Posterior cervical screw fixation in children: the treatment experience

Objective. To prove the safety and technical and mechanical validity of posterior screw fixation of the cervical spine in children and to compare different types of the cervical spine fixation based on our own treatment experience and literature data. Material and Methods . A retrospective analysis of 47 patients under the age of 18 years who underwent various types of posterior instrumental fixation of the cervical spine was performed. Level of Evidence – III. Results . The duration of postoperative follow-up varied from 2 months to 6.6 years (mean, 2.1 ± 1.6 years). A total of 186 screws were placed, the number of screws inserted in one patient reached 10 (mean, 3.9 ± 2.4). Postoperative complications were observed in 5 (10.6 %) patients. Conclusion . Posterior screw fixation of the cervical spine provides biomechanically reliable stabilization of the segment, helps to achieve good correction of deformity and reduction of dislocations, shortens the period of rehabilitation, and is a safe method of surgical treatment in children.

Application of intraoperative O-arm-assisted real-time navigation technique for spinal fixation

This study explored the combined use of the O-arm and real-time navigation during spinal fixation. The clinical data for 60 patients undergoing spinal fixation, at Beijing Tsinghua Chang Gung Hospital between May 5, 2015 and May 1, 2017, were retrospectively analyzed. Pre-, intra-, and postoperative imaging findings were assessed. The patients were classified into the occipitocervical fusion (32 cases) and thoracic/lumbar/sacral spine fixation (28 cases, including 6 cases of percutaneous pedicle screw) groups. Lesion resections were performed microscopically. An O-arm, combined with real-time navigation, was used to assess spinal fixation. Efficacy was evaluated using operative times, X-ray times, screw positioning, and complications. Within the occipitocervical fusion group, 182 screws were placed in the cervical spine and 96 in the occipital bone. However, 6 screws penetrated the bone cortex and were adjacent to the vertebral arteries, based on O-arm three-dimensional imaging; therefore, the precision rate was 96.7%. Within the thoracic/lumbar/sacral spine fixation group, 148 pedicle screws were implanted, with 4 initially outside the vertebral body, yielding a precision rate of 97.3%. Ten percutaneous pedicle screws were implanted and well positioned. O-arm scans were performed 3 times/patient, with an average of 20-30 min/time. Screw implantation times were 5-7 min (cervical spine), 8-10 min (thoracic spine), and 6-8 min (lumbar spine). Intraoperative O-arm scans, combined with real-time navigation technology, allow real-time observation of screw angles and depths, improving the accuracy and safety of posterior screw fixations and reducing the radiation dose and frequency experienced by patients and surgeons.

Surgical management of post-traumatic atlantoaxial rotatory fixation due to C2 facet fracture: 5 clinical cases

PurposeReport the results of surgical treatment of post-traumatic atlantoaxial rotatory fixation (AARF) due to C2 articular facet fracture in adults. Material and methodsThe records of five patients treated since 2009 for AARF due to a C2 articular facet fracture were analyzed retrospectively. Three women and two men with an average age of 60 years (27–82) were included, one of whom initially had neurological deficits. In all cases, the surgical strategy consisted of posterior fixation: Harms-type in four cases and trans-articular with hooks in one case. ResultsDislocations due to fracture of the C2 articular facet are rare in adults; various treatment strategies have been described. In our experience, posterior screw fixation leads to satisfactory clinical and radiological outcomes. Fusion is not necessary in these cases because the dislocation is related to an asymmetric fracture without ligament damage. ConclusionPosterior fixation provides satisfactory reduction of these injuries and leads to satisfactory bone union. This surgical treatment can be performed early on after the trauma and is an interesting alternative to conservative treatment.

Application of oblique lateral interbody fusion in the degenerative lumbar disease

Objective To investigate the operation key points and clinical efficacy of oblique lateral interbody fusion (OLIF) for the treatment of degenerative lumbar disease. Methods The clinical data of 22 patients with degenerative lumbar disease treated with OLIF at the Department of Neurosurgery, Sichuan Provincial People’s Hospital from December 2014 to October 2015 were analyzed retrospectively. Eight patients were treated with the combined posterior percutaneous pedicle screw fixation, 11 were treated with the combined anterior percutaneous pedicle screw fixation, and 3 did not treated with the screw-rod system fixation. The visual analogue scale (VAS) score, Oswestry disability index (ODI) score, and imaging findings before and after procedure were compared. The clinical efficacy of the surgical method was evaluated. The follow-up time ranged from 3 to 9 months (mean, 6.6 months). Results Postoperative VAS score (2.73±0.84) and ODI score (20.97±3.83) were significantly decreased compared with before procedure (VAS score: 7.10±0.97; ODI score: 60.86±6.88; all P<0.05). The average operation time was 92.5±14.8 min, the average blood loss was 78.4±29.6 ml, and the average length of stay was 8.2±2.4 d. Compared with before procedure, the postoperative intervertebral space height was increased (after procedure: 9.12±1.09 mm, before procedure: 5.24±1.07 mm, P<0.001) and the intervertebral foramen area was increased in 22 cases (after procedure: 1.81±0.25 cm2, before procedure: 0.83±0.10 cm2, P<0.001). None of them had severe complications, such as vascular injury, lumbar plexus nerve injury, ureteral injury and infection. Conclusions OLIF is a safe, effective, and minimally invasive surgical method for the treatment of lumbar degenerative disease. Its clinical efficacy is reliable in the near future. It has the advantages of short operation time, less intraoperative blood loss, less trauma, and quick recovery. Strict selection of patients and grasping the technical details are the keys to the success of surgery. Key words: Lumbar vertebrae; Intervertebral disc degeneration; Surgical procedures, minimally invasive; Oblique lateral interbody fusion

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

Surgical Management of the Spinal Cord Vascular Lesions Supplied by the Anterior Spinal Artery

Introduction Surgical management of the spinal cord (SC) vascular malformations supplied by the anterior spinal artery (ASA) is still disputable and technically demanding. Treatment options include endovascular, open surgical, or a combination of the two methods. All options have a risk of SC ischemia resulting from retraction or dissection through the SC, coagulation or embolization of the SC supplying artery. The authors consider surgery to be an ultimate solution for this pathology. We present four patients with symptomatic anteriorly placed vascular malformations in which total excision of the lesions was performed by a posterolateral approach with unilateral arthropediculectomy. Materials and Methods The case series included 4 patients (2 male, 2 female), ages 23–56 (mean 32). All patients initially presented with weakness in the lower limbs and (or) pelvic organ dysfunction. The preoperative evaluation consisted of a neurologic/urodynamic evaluation, and imaging studies. In all patients the neuroimaging included magnetic resonance imaging (MRI) and selective spinal angiography (SSA), confirming the diagnosis of arteriovenous malformation in two patients, spinal hemangioma in one, and cavernous angioma in another. Vascular malformations were supplied by the ASA in 2 cases and by both the anterior and posterior spinal arteries in the other two cases. Neurologic status was based on duration of symptoms, the presence of motor, sensory or sphincter dysfunction and grading by the Frankel scale. Two patients with malformations supplied by anterior and posterior spinal arteries underwent endovascular intervention to reduce the intensity of blood flow by means of embolization. In all patients the surgery was three stage procedure made in one operative session: 1. Posterolateral approach with unilateral arthropediculectomy; 2. Microsurgical resection of the malformation; 3. Posterior instrumented fusion (to avoid postlaminectomy kyphosis). The patients were positioned prone on the Jackson table with 3-point Mayfield clamp affixed to the head placed in a neutral position, to allow adequate posterior fusion. Posterolateral approach with unilateral arthropediculectomy allowed to obtain adequate visualization of the anterior and lateral aspects of the SC for direct manipulations on the malformation and its feeding vessels, while avoiding direct manipulations on the SC or its dissection. Cervical/thoracic posterior screw fixation and fusion was performed using freehand technique considering unique osteoligamentous and vascular anatomy. None of the screws were malpositioned or interfered with post-op SSA. Results Postoperative SSA demonstrated complete disappearance of the malformation in all cases. Neurological outcome improved in all patients. Follow-up Frankel grades showed improvement to grade E in 2 patients (50%), and reached grade D in 2 (50%). Conclusion Despite the increasing use of endovascular techniques there is a significant role for operative management of spinal cord (SC) vascular malformations having complicated/combined arterial feeding. Treatment should be individualized and integrated by endovascular and surgical procedures, considering lesional angioarchitecture and clinical status of the patient. Surgical approach should provide the exposure of the anterior and lateral aspects of the SC for direct manipulations on the malformation and its feeding vessels, and exclude manipulations and dissection of the SC.

Dorsal Fusion as Correction of Craniocervical and Atlantoaxial Instability in Patients with Benign and Malignant Lesions using O-Arm System

Introduction A retrospective and prospective analysis of the surgical treatment and results of 99 patients with benign and malignant craniocervical, atlantoaxial and high cervical lesions operated during 36 – month period (2011–2014) at the Department of Neurosurgery, Klinikum Fulda gAG, Germany was performed. The aim of the analysis was to assess the factors affecting dorsal fusion as correction of craniocervical and high cervical instability. Material and Methods The mean age of the patients was 57 years. The female to male ratio was 1:1,3. The most frequent neurological symptoms were quadriparesis, discoordination, cranial and spinal nerves palsy and local pain. We analyzed 67 patients with traumatic lesions, 10 patients with inflammatory lesions, 8 patients with degenerative instability, and 14 patients with high cervical tumors. In the subgroup of patients with traumatic lesions we found 39 odontoid fracture II Type, 11 Hangemann fracture and 17 combined cervical fracture; in the subgroup of patients with tumors we observed 3 cases with plasmocytoma, 3 case with chordoma, 1 case with C2–3 schwanoma, and 7 cases with metastatic lesions; in the inflammatory subgroup we analyzed 6 cases with RA and 4 cases ankylose spondylitis. Results In 99 patients we performed 129 operations. We used posterior cervical, and craniocervical median approach. Because of craniocervical/cervical instability we made posterior screw fixation in all of 99 patients. In 47 patients we performed additionally decompressive laminectomy. To improve screw placement accuracy we performed intraoperative O-Arm in 82 cases. The operative duration was 2.25 hour. in O-Arm operations and 4.35 hour in C-arm operation. The most common operative complications were: CSF leak – in 2 cases, postoperative infection – in 4 cases, and without early operative mortality. The 12-monts follow-up showed good recovery in 65 patients, moderate disabling – 25 patients, severe disabling – 5 patients, vegetative state – 4 patients, death 3 patients with malignant lesions. Conclusion Early correction of craniocervical and high cervical instability facilitated neurological recovery by preserving the existent neurological function. Using of O-Arm increase operative screw placement accuracy, and preserve intraoperative nerve and vertebral artery injury. Recently because of the improvement of neuroimaging techniques, operative approaches, surgical techniques and neurointensive care the results of treatment of these lesions are optimal.

First Sacral Pedicle-A Morphometric Analysis

Background: Human osteology varied in various phases of human evolution. The morphology and morphometry of bones varies across different geographical areas in response to the climatic (topographical) and hereditary factors. Knowledge on Osteology plays a vital role in anthropological studies, forensic aspect, diagnostic and interventional aspects in the field of surgery. Human sacrum is a triangular fusion of five vertebrae. It forms the postero superior wall of the pelvic cavity. Sacral pedicle screw fixations are becoming increasingly popular now a days in interventions like posterior transpedicular screw fixation, pediculocorporeal screw placement for the treatment of unstable lumbosacral spine caused due to trauma, degenerative changes, malignancies and congenital anomalies. Lumbosacral spondylosis is best treated by spinal external fixation. Methods and Results: In this study of 30 sacra in adults (15 males & 15 females), the first sacral pedicle morphometry with parameters like H distance, W distance, XP distance, T angle and AM angle were measured using vernier caliper & goniometer. The total H distance, W distance, XP distance, T angle and AM angle were 20.85 ± 2.46 mm, 21.76 ± 2.50 mm,46.21 ± 3.68mm, 43.17 ± 2.74° and 34.07 ± 2.15° respectively on the right side. The total H distance, W distance, XP distance, T angle and AM angle were 21.33 ± 2.73 mm, 21.69 ± 2.61 mm,45.89 ± 3.58 mm, 43.30 ± 1.69° and 34.17 ± 1.95° respectively on the left side. The results were documented in males and females along with their right and left sides respectively. Conclusion: To update knowledge of human sacrum which proves mandatory for the Forensic, Radiology, orthopaedic fields and to help as a marker for interventions like posterior transpedicular screw fixation, pediculocorporeal screw placement for the treatment of unstable lumbosacral spine caused due to trauma, degenerative changes, malignancies and congenital anomalies, the study has been carried out. K

Inclusion of the fracture level in short-segment fixation of unstable traumatic thoracolumbar spine fractures

Introduction The diagnosis, classifications, and treatment of injuries of the thoracolumbar spine continue to attract controversy. Objective The present study evaluated the efficacy of treatment of unstable thoracolumbar burst fractures by transpedicular screw fixation including the fractured vertebra. Patients and methods From January 2013 to March 2015, 40 patients with thoracolumbar burst fracture underwent posterior pedicle screw fixation consecutively in Al-Azhar University Hospital, Damietta. Results Forty (25 male and 15 female) patients with age ranging between 16 and 66 years (mean 41.8%) were operated upon by posterior transpedicular screw fixation. According to the American Spinal Injury Association scoring system, all patients were grade E. The mean of kyphotic deformities measured preoperatively was 18.4±5.5° and after 12 months of follow-up it was 9.0±4.1°. Conclusion By applying the transpedicular screw fixation of the unstable fractures of the thoracolumbar spine, a stable fracture fixation can be achieved; this kind of fixation prevents secondary spine deformities.

Anaesthetic concerns of a pregnant patient with Pott's spine for spine surgery in prone position.

Sir, Surgical decompression is the treatment of choice in pregnancy complicated by spinal tuberculosis with neurologic deficit.[1] We report the anaesthetic management of a pregnant patient with Pott's spine in prone position and discuss the various anaesthetic concerns including haemodynamic instability. A 23-year-old multipara, 17 weeks of gestation, weighing 52 kg, with Pott's spine involving T7–T10 segments with progressive neurological deficit was scheduled for decompression and posterior screw fixation. Obstetrician's opinion was sought. Preoperative foetal heart rate (FHR) was documented. Anti-aspiration prophylaxis was administered. Her baseline HR was 112/min and blood pressure (BP) was 132/82 mmHg. Invasive arterial BP monitoring could not be done due to the logistic problems. General anaesthesia was induced with propofol and morphine. Endotracheal intubation was facilitated using vecuronium with size 7.0 orotracheal cuffed tube. Injection glycopyrrolate 0.2 mg was administered as anti-sialagogue. Anaesthesia was maintained with isoflurane in 50% nitrous oxide and oxygen mixture. Soon following positioning, patient developed hypotension i.e., more than 20% fall from the baseline systolic BP (SBP). Fluid replacement and pressure-free abdomen were rechecked but the SBP continued to remain between 90 and 100 mmHg. Initially, hydrocortisone 100 mg was administered intravenously. The oozing from the surgical site resolved following injection tranexamic acid 500 mg. Surgery lasted for 5 h but BP persisted in the same aforementioned range. Blood loss was 1000 ml approximately. Haemodynamics and FHR remained stable post-operatively. The anaesthetic concerns related to spine surgery in pregnant patient include both obstetric and surgery-related i.e., prolonged surgery in prone position, major blood loss, relative hypotension and risk of postoperative visual loss.[2] The risk of radiation is of paramount concern due to the inability to use abdominal shield and the proximity of radiation to the foetus. The additional problem with prone position here includes the inability to perform emergent caesarean section. Technical problems may limit the usefulness of continuous FHR monitoring between 16 and 20 weeks and it is recommended to document FHR before and after surgery which was done in our patient. The American College of Obstetricians and Gynaecologists recommends continuous FHR monitoring in non-obstetric surgery from 18 to 20 weeks of gestation, based on the patient and the surgery to be performed.[3] There has been controversy related to the use of controlled hypotension and intraoperative tests/monitoring to detect spinal cord injury during pregnancy. Invasive arterial BP monitoring must be performed, more so, if controlled hypotension is instituted. Various risk factors for haemodynamic instability in these patients include pregnancy-induced aortocaval compression, massive fluid shift, blood loss and prolonged surgery. In addition, autonomic dysfunction has been reported as the cause for high incidence of intraoperative hypotension in adult patients with thoracic spine tuberculosis.[4] In our patient, vasopressor was not considered to treat hypotension:First, because, as the SBP remained in the acceptable range of 90–100 mmHg, and second, its use could have further led to increased blood loss. Since the hypotension occurred soon after positioning, it could be attributed by factors such as pregnancy-induced aortocaval compression, pre-operative hydration status and autonomic neuropathy related to thoracic spine tuberculosis. The initial two factors were ruled out by ensuring adequate fluid replacement and free and hanging abdomen in prone position. It is also reported that prone position in pregnant patient is associated with lesser risk of aortocaval compression than sitting or lateral position.[5] To conclude, intraoperative haemodynamic stability is of paramount anaesthetic concern in pregnant patients with thoracic spine tuberculosis and autonomic dysfunction must be considered as a potential cause for intraoperative hypotension. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

The diagnosis and management for the combination fractures of atlas and axis

Objective To investigate the treatment strategies and clinical effect of the combination fractures of atlas and axis. Methods Data of 56 cases with combination fractures of the atlas and axis treated from July 2006 to March 2014 were retrospectively analyzed. There were 36 males and 20 females with mean age of 38.6 years old (range, 21 to 63 years old). Dickman Atlantoaxial compound fracture classification: C1-II type dens fracture 21 cases, C1 fracture-atlantoaxial stability fracture 8 cases; C1 fracture-III type dens fracture 9 cases; C1 fracture-Hangman fracture 18 cases. 8 cases of C1-atlantoaxial stability fracture, 2 cases of C1-III type dens fracture and 7 cases of C1-Hangman fracture had conservative treatment and the other 39 cases were taken surgery. There were 13 patients who suffered from nerve injury such as limbs numbness, movement and the reflecting barrier before surgery: 2 Frankel B, 4 Frankel C, and 7 Frankel D. The mean preoperative JOA score was 8.6 ranging from 5.5 to 12.8. Results All patients were followed-up for a mean period of 32 months (range, 6-58 months). All the operated segments of atlas and axis showed stability and X ray showed fusion achieved within six months (average 4.5 months). Postoperative pain, upper limb numbness and neck pain were improved. 13 cases who had neurological symptoms before surgery achieved an average of 1-2 degrees of Frankel grade recovery after 6 months. The average JOA scores 6 months after operation were 14.1 ranging from 11.5 to 15.8 and the rate of improvement was 82.7% ranging from 71.5% to 95.3%. At the latest follow-up, 39 cases with surgical treatment had no complications such as fracture fixation, spinal cord injury, vertebral artery injury and cerebrospinal fluid leakage; 1 case occurred wound infection which healed after a month by debridement and dressing. Conclusion C1 fracture-III type dens fracture and stable axis fracture and stable Hangman stability fracture should be undertaken with conservative treatment. C1 fracture-II type dens fracture with atlantoodontoid interval >5 mm and unstable Hangman fracture should be treated with posterior cervical pedicle screw fixation. Occipitocervical fixation could be taken with the atlas anatomical abnormalities, severe comminuted fractures and atlas pedicle screw fixation loosening. Key words: Cervical atlas; Axis; Fractures, bone; Fracture fixation, internal

Prospective, Self-controlled, Comparative Study of Transposterior Arch Lateral Mass Screw Fixation and Lateral Mass Screw Fixation of the Atlas in the Treatment of Atlantoaxial Instability

A prospective self-controlled study. The aim of the present study was to compare the application and clinical outcomes of transposterior arch lateral mass screw and lateral mass screw fixation of the atlas in the treatment of atlantoaxial instability. Atlas posterior screw fixation techniques comprise transposterior arch lateral mass screw fixation and lateral mass screw fixation. Previous studies have focused mainly on the feasibility of the anatomy and the biomechanics of the methods. From June 2006 to February 2011, 66 patients with atlantoaxial instability were randomly assigned for treatment with transposterior arch lateral mass screw or lateral mass screw fixation of the atlas, combined with axis pedicle screw fixation. Patients were followed up regularly. The operation time, blood loss, intraoperative complications, Japan Department of Orthopedics Association Score, visual analog scale score, and bone fusion rates were recorded. The operation was successful in all 66 cases, with all patients showing improvement in clinical symptoms. There were significant differences in operation time and blood loss between the 2 groups (P<0.001). The mean follow-up time was 49 months. At the final follow-up, the Japan Department of Orthopedics Association score was significantly better than the preoperative score (mean, 13.5; P<0.05). The mean postoperative improvement rate was 88.2% and the mean visual analog scale score was 1.9; both results were significant as compared with preoperative results (P<0.05). Bone fusion was achieved within 6 months after operation. No screw loosening, shifting, breakage, or atlantoaxial instability was observed. Six patients with atlas lateral mass screw placement had burst bleeding of C1-C2 venous plexus during surgery. Five patients had immediate pain and numbness at the occipitocervical region. Atlas transposterior arch lateral mass screw fixation is less invasive, simple, has fewer complications, and offers good fixation results for atlantoaxial instability as compared with lateral mass screw fixation.

Treatment of traumatic upper cervical instability with single posterior atlantoaxial pedicle screw system

Objective To investigate the clinical efficacy of atlantoaxial pedicle screw fixation plus bony fusion in treatment of traumatic upper cervical instability. Methods From October 2009 to August 2013, 29 patients with traumatic upper cervical spine instability were treated with posterior atlantoaxial pedicle screws. The patients underwent autografting (n=19) and allografting (n=10) for spinal fusion. Surgical outcomes were recorded including intraoperative blood loss, operation time, with or without nerve, blood vessel and spinal cord injury, wound healing and bone fusion rate. Results All operations were completed smoothly with operation time of 110 minutes (range, 85-135 minutes) and blood loss of 150 ml (range, 80-500 ml). At the follow-up of 10 months to 5 years (mean 18 months), bony fusion was detected for all the patients. Postoperative radiographs verified all patients were bony fusion with satisfactory cervical spine stability. No complications of reduction loss, fixation failure, and spinal cord or vertebral artery injury were observed except for 1 patient with low virulent infection and 2 with delayed wound healing. Conclusion Single posterior atlantoaxial pedicle screw fixation provides security and reliable stability in treatment of upper cervical instability, however wound healing problems should be taken seriously. Key words: Axis; Spinal injuries; Pedicle screws

One stage atlantoaxial pedicle screw fixation for unstable atlas burst fracture

Objective To assess the clinical results of one stage posterior atlanloaxial pedicle screw fixation and fusion for unstable atlas burst fracture. Methods A retrospective analysis of clinical data including 32 cases, which were admitted according to the inclusion and exclusion criteria between May 2010 and December 2013. There were 11 females and 21 males whose age ranged from 22 to 59 years (mean 41.8 years). X-ray, CT scan reconstruction and MRI were done before operation to evaluate the injury of ligament and fracture. There were 17 cases of unstable atlas burst fracture,including 5 cases Jefferson fracture,8 cases untypical Jefferson fracture, and 4 cases lateral mass fracture combined with anterior arch or posterior arch fracture. There were 15 cases combined with axial fracture, 9 cases combined with dens fracture, 4 cases with axial body fracture, and 2 cases with Hangman fracture. The patients had various degrees of occipital neck pain, limited mobility and neurological dysfunction. Degree C in 1 case and degree D in 5 cases were assessed by the American Spinal Cord Injury Association (ASIA) impairment scale. All patients were treated with one stage posterior atlantoaxial pedicle screw fixation and fusion. All patients were assessed clinically by neurologic recovery, atlantoaxial reduc tion and bone graft fusion. The preoperative and postoperative atlanto-dens interval (ADI), lateral mass distance (LMD) and VAS were measured and statistically analyzed. Complications were observed. Clinical outcome of last follow-up was evaluated by dynamic X-ray and CT scan. Results All patients were followed up. The follow-up time ranged from 10 to 24 months (mean 15.6 months). The healing time of bone fusion ranged from 5 to 10 months with an average follow-up time of 6.9 months. The average preoperative VAS score was 5.0±1.4 while the score of last follow-up was 1.0±0.7, with statistically significant differences. Neurological status improved in all patients but one. Four cases with grade D improved to E, and one cases with grade C improved to D. Postoperative cervical spine X-ray and CT showed that the sagittal cervical spine alignment was restored. The preoperative ADI was 4.6±1.2 mm, which was statistically significant different with last follow-up the ADI of 2.4±1.0 mm. There were statistically significant difference between preoperative LMD of 5.6±2.2 mm and postoperative LMD of 1.2±1.0 mm. Conclusion The posterior atlantoaxial pedicle screw for unstable atlas burst fracture combined with atlantoaxial instability seems to be effective. It is technically demanding to place screw into thelateral mass of the atlas. Key words: Cervical atlas; Spinal fractures; Atlanto-axial joint; Joint instability; Spinal fusion

The Importance of 360-Degree Stabilization and Fusion in Lytic Spondylolisthesis. A Minimally Invasive Technique to Revision and Complete the Final Construction after Broken Screw

Introduction The spondylolisthesis lytic is a very unstable pathology and a reduction with a 360-degree stabilization improve solid fusion, only a posterior approach is not enough, is possible to see a broken transpedicular screw. Patient and Methods: We present a case of a 36-year-old woman with a spondylolisthesis lytic grade 2 who underwent just a posterior screw fixation; 6 months after surgery she feels lumbar and radicular pain, the rx shows a left S1 broke screw. Results We present a minimally invasive anterior lumbar interbody fusion plus a revision by posterior way to achieve reduction and circumferential fixation with percutaneous transpedicular screws preserving the muscular and ligamentous posterior tension band. The surgical time was 70 minutes, the blood loos 50 mL, time to discharge 23 hours after surgery and the return to normal activities in 5 days. The VAS pre-op was 8 and post-op 2, oswestry disability index post-op was 4. Conclusion The spondylolisthesis lytic needs a 360-degree approach to produce safe stabilization and possibility of solid fusion and a minimally invasive techniques allow to preserve muscular and ligament injuries and help the patient to return to normal activities shortly.

The clinical effects of atlantoaxial pedicle screw combined with unilateral axial spinous process and lamina screws for atlantoaxial instability

Objective To investigate the clinical effects of the posterior atlantoaxial pedicle screw fixation combined with unilateral axial spinous process and lamina screws and allogeneic bone graft for atlantoaxial instability. Methods From March 2010 to April 2014, data of 10 patients with atlantoaxial instability who had undergone atlanto-axial vertebral pedicle fixation and interbody fusion combined with posterior atlanto-axial spines lamina nails were retrospectively analyzed. There were 6 males and 4 females with an average age of 39 (range, 16-62) years old. The inclusion criteria was atlantoaxial instability together with unilateral vertebral artery segment high cross deformity (7 patients) or atlantoaxial joint break bad involving unilateral pedicle (7 patients). 3 patients have spinal cord disease symptoms and physical signs, both suffered limited neck mobility and pain. The VAS scores were 1-8, with an average of 3.70±2.11. Preoperative X-ray, CT three-dimensional reconstruction and MRI were collected. X-ray and CT examination were performed 7 d and 1, 3, 6, 12 months after operation to evaluate the internal fixation and bone grafting fusion. Results There's no occurrence of cervical spinal cord and vertebral artery injury. Screws were successfully implanted. 1 case's incision occurred infiltration liquid 3 days after operation. For allograft rejection consideration, we changed the plan, and the infiltrating stopped 5 days later. Other incisions were all primary healing. VAS scores were 1.01±0.89 after operation, which was significantly reduced. X-ray showed good recovery of cervical sequence after the operation, and CT revealed 1 patient with atlas pedicle screw in the medial cortex damage. Spinal canal was without infringing, and the other screw positions were normal. 6 months after operation, X-ray or CT examination both showed bony fusion. Conclusion Atlantoaxial pedicle screw fixation combined with unilateral axial spinous process and lamina screws and allograft bone graft fusion for the treatment of atlantoaxial instability can observe good clinical effects. Key words: Cervical atlas; Axis; Joint instability; Internal fixators

Posterior C2 Instrumentation in the Management of Trauma: Accuracy and Risks Associated with Four Techniques

Introduction Posterior instrumentation of C2 is important in treating occipitocervical, atlanto-axial, and subaxial spinal injuries. The variable C2 anatomy can make instrumentation challenging and prone to potentially severe and even life-threatening complications. The goal of this study was to (1) evaluate a large series of posterior C2 screws to determine accuracy as assessed by computed tomography (CT) scan, (2) assess dimensions of “safe bony windows” with CT, and (3) assess the perioperative complication rate related to errant screw placement. We hypothesize that the evolution of a greater variety of options for C2 fixation and the ability to tailor these techniques to patients' specific anatomy has resulted in decreased complications and increased accuracy. Material and Methods A retrospective review of a single Level I trauma center spine database was assessed to identify all patients with operative management for traumatic conditions with C2 instrumentation between December 2002 and September 2008. Radiographic analysis included evaluation of pre- and postoperative CT scans to quantify the patients' bony anatomy as well as to classify the accuracy of C2 screw placement. All C2 screws were graded using the following definitions: Type I: Screw threads completely within the bony cortex. Type II: Less than half the diameter of the screw violates the surrounding cortex. Type III: Clear violation of the transverse foramen or spinal canal. Results A total of 169 patients (99 males and 70 females) underwent posterior C2 screw fixation for traumatic conditions of the spine, including 23 atlanto-occipital dissociations, 16 unstable C1 ring injuries, 79 dens fractures, 9 Hangman fractures, 8 other C2 fractures, 3 C2 hyperextension injuries, 4 C2–C3 flexion–distraction injuries, 14 subaxial injuries, and 19 odontoid nonunions. Average CT measurements of pedicle height, axial width, and laminar width were 8.1 mm (standard deviation 2.1 mm), 5.8 mm (1.9 mm), and 5.7 mm (1.5 mm), respectively, with males having larger pedicle height ( p &lt; 0.001), pedicle width ( p &lt; 0.001), and laminar width ( p &lt; 0.022). A total of 324 screws underwent CT analysis and chart review. A total of 169 pedicle, 85 trans-articular, 50 laminar, and 20 short pars screws were placed with 80.6, 84.4, 96, and 94.4% accuracy rates (Grade I vs. II and III), respectively. Overall 85% of the screws were rated as being in the ideal location. There were no cases of known vertebral artery injury at the time of surgery. Two pedicle screws were unacceptably placed (Grade III). Both patients had screws encroaching on the vertebral artery foramen: one patient had a vertebral artery occlusion and the other had a Grade I dissection documented on CT angiogram without clinical signs of stroke or emboli as measured on transcranial Doppler. No neurological injuries resulted from instrumentation. Conclusion Our findings demonstrate a lower than previously reported incidence of complications associated with posterior C2 screw placement. In the management of 169 patients with 324 screws, only 2 patients had vascular injuries, neither of whom had any sequelae. The multiple techniques of posterior C2 fixation that are currently available allow for unprecedented flexibility in determining which technique is best suited for a given patient's anatomy.

Radiological and anatomical study of posterior occipital condyle screw trajectory

Objective To investigate the optimal trajectory of posterior occipital condyle screw fixation via radiological and anatomical study. Methods Twelve adult craniocervical junction complete specimens were selected. The length, width and height of occipital condyle and the inclination angle of the longest axis were measured by CT scanning and reconstruction. Subsequently, occipital condyle screws were inserted with reference to CT measurements. After screw fixation, accuracy and safety of the placement of occipital condyle screw were verified by gross observation and CT scanning. Results Preoperative measurements of height and width of the occipital condyles indicated the placement of 4. 0 mm bicortical screws was secure. Left vertebral artery horizontal sections of 2 specimens were slightly pressed without damage. CT scanning identified no damage to the inner or outer wall of the occipital condyle and the hypoglossal canal. Trajectory parameters between the right and left sides were slightly different, but no significant difference was observed (P>0. 05). Average screw channel length and inclination angle were (20.8±2.6)mm and (37.1±4.7)°respectively. Angle between screw and skull base tangent was observed as (8.5±1.7)°. Distance between screw axis and hypoglossal canal was observed as (3.1±1.1)mm. And the distance averaged (4.6±1.4)mm between occipital condyle screw entry point and skull base and (6.1±1.5)mm between entry point and inside edge of the occipital condyle. Conclusion Occipital condyle can be used as a new alternative fixed point in occipitocervical fusion. Key words: Occipital bone; Spinal fusion; Occipital condyle screws

Influence of different fusion techniques in lumbar spine over the adjacent segments: A 3D finite element study.

The most conventional technique to treat the intervertebral disc degeneration consists on fusing the affected segment with a posterior screw fixation and sometimes with the insertion of a cage in the intersomatic space. However, this kind of surgeries had controversial results in the adjacent discs. The aim of this work was to prove the stabilization of the spine and the decompression of the disc and to analyze the influence over the adjacent segments. With this purpose, four different models were built and simulated under different loading conditions. The stabilization of the spine was ensured by the screw fixation which reduced dramatically the relative motion in the affected segment. On the other hand, the pore pressure showed a high fall in the operated models proving the decompression of the neural structures. In the adjacent segments, the ROM increased up to 50% in the upper disc and 70% in the lower one. The pore pressure and principal stresses also increased after both surgeries. The observed results suggested that the fusion procedure could trigger a cascade degeneration effect over the adjacent discs, while it is also seen that cage insertion helps to maintain disc height in a better way than screw fixation only.

Stabilization of the craniocervical junction after an internal dislocation injury: an in vitro study

Background contextReconstructive surgeries at the occipitocervical (OC) junction have been studied in treating degenerative conditions. There is a paucity of data for optimal fixation for a traumatically unstable OC joint. In clinical OC dislocations, segmental fixation may be impossible because of vertebral artery injury or fracture. Segmental fixation of the occiput, C1, and C2 demonstrated maximum biomechanical stability in fixation of an unstable craniocervical dislocation. A biomechanical study comparing various points of cervical posterior screw fixation after recreating traumatic injury would illuminate relative advantages between the various techniques. PurposeTo determine the rigidity lost, if any, of segmental C0–C2 posterior screw fixation versus fixation skipping C1 at the OC junction, with or without a cross-connector. Study designThis study is a cadaveric biomechanical investigation. MethodsIntervertebral motions and translations were recorded in seven specimens under conditions in the following order: intact, OC dislocation model with complete disruption of the cruciate ligaments, alar ligaments, and occipitoatlantal/atlantoaxial capsules (injury), segmental posterior fixation (SPF) with posterior instrumentation (ELLIPSE; Globus Medical, Inc., Audubon, PA, USA) at occiput, C1, and C2 levels, endpoint fixation (EPF) with posterior instrumentation at occiput and C1 level skipping C1, and endpoint fixation with a cross-connector (EPFC). Motion was applied through a custom spine simulator with a pure moment load of 2.5 Nm and measured with motion capture markers attached to occiput (C0), anterior C1 ring, and C2. Flexion-extension (FE), lateral bending (LB), axial rotation (AR), and cranial-caudal (CC) motions were recorded in terms of C0–C2. Results were reported as a percentage of injured motion (injury=100%), unless otherwise stated. ResultsThe injury significantly increased the motion to 165%, 263%, and 130%, during FE, LB, and AR, respectively, of intact. The CC translations increased to 164%, 254%, and 121% during FE, LB, AR, respectively, of intact. Segmental posterior fixation significantly reduced motion to 7%, 8%, and 1%, during FE, LB, and AR, respectively, of injury. Endpoint fixation significantly increased motion in FE, resulting in 12%, 6%, and 4% during FE, LB, and AR, respectively, of injury when compared with SPF. The EPFC construct decreased the motion compared with its counterpart to 8.6%, 5.7%, and 3.2% during FE, LB, and AR, respectively. ConclusionsAll fixation constructs significantly reduced motion in all loading modes and CC translations, compared with intact and injury. The construct with the greatest stability against craniocervical dislocation included SPF with instrumentation at the occiput, C1, and C2. By skipping C1 using the EPF, FE and cephalad-caudal translations significantly increased compared with posterior fixation at every level. The addition of a cross-connector increased the stability but was not statistically significant.