Anterior Pedicle Screw Research Articles

The accuracy and feasibility study of freehand pedicle screw insertion for subaxial cervical spine assisted with safe core-referred technique

Objectives: To construct the "safe core" of the pedicle screw trajectory using CT imaging data of the subaxial cervical spine in adults, and to assess the accuracy and feasibility of the pedicle screw insertion assisted with the "safe core-referred technique" for subaxial cervical spine with a cadaver specimen study. Methods: This is an experimental study. From January 2015 to March 2020,60 adults' CT images data of the cervical spine were collected from the database of the First Affiliated Hospital of Gannan Medical University,and were imported into Mimics 20.0 software. Virtual cervical pedicle trajectory and safe core were constructed according to the self-designed "virtual construction method of pedicle in the subaxial cervical spine". The success rate of the construction and the spatial position data of the virtual safe core of was recorded,including the distance between the safe core and the tangent line of the upper and lower outer edge of Luschka's joint on coronal plane,and the distance between the safe core and the posterior edge of the vertebral body on sagittal plane.The 3.5 mm column was used to simulate the pedicle screw placement,using the safe core as the only hub in pedicle screw trajectory.The length of the anterior pedicle screw trajectory,the interval of the abductive angle of the pedicle screw in axial plane, and the projection area of the entry area on periapical radiograph was calculated.In addition,8 adult cervical cadaver specimens were collected for the pedicle screw insertion experiment.The left side group used the "safe core-referred technique" for pedicle screw insertion,while the right side group used the Abumi method for pedicle screw insertion.The accuracy of pedicle screw placement was verified by CT scan.The difference between the accuracy of subjective judgment based on X-ray monitoring of operator and the actual accuracy of pedicle screw insertion verified by CT scan was compared between the two groups.The chi-square test was used to compare the intergroup data. Results: The total success rate of the virtual construction method for the safe core of the subaxial cervical spine was 97.0% (291/300); The distance between the safe core and the tangent line of the upper and lower outer edge of Luschka's joint on coronal plane was (M(IQR)) 0.91 (0.98) mm (range: 0 to 1.85 mm);The distance between the safe core and the posterior wall on the sagittal plane of the vertebral body was (2.01±0.86) mm (range: 0.67 to 3.53 mm). The distance (anterior pedicle screw trajectory) from the posterior cortex to the central point of the safe core was (11.58±1.00)mm (range: 8.27 to 14.93 mm).The projection area of the entry point on the coronal plane was (36.18±11.67) mm2 (range: 13.38 to 83.11 mm2). Pedicle screw insertion experiment in cervical cadaver specimen showed the rate of intraoperative correction of the pedicle screw trajectory was 7.5% (3/40) in the experimental group and 12.5% (5/40) in the control group (χ2=0.139,P=0.709). The operator 's correct rate of subjective judgment on CT in the stage of pedicle screw trajectory preparation was 100% (40/40) in the experimental group and 82.5% (33/40) in the control group, the difference was statistically significant (χ2=5.638,P=0.018). The actual correct rate of CT verification in the stage of pedicle screw insertion was 100% (40/40) in the experimental group and 90.0% (36/40) in the control group, the difference was statistically significant (χ2=2.368,P=0.124); The operator 's correct rate of subjective judgment in the stage of pedicle screw insertion completion was 100% (83/83) in the experimental group and 92.9% (79/85) in the control group (χ2=4.199,P=0.040). Conclusions: The virtual safe-core of subaxial cervical spine can be use as a reliable anatomical fluoroscopy landmark for freehand pedicle screw insertion."Safe core-referred technique" can improve the accuracy rate of the operator's subjective judgment on the intraoperative fluoroscopy monitoring,and hence improve the accuracy of freehand pedicle screw insertion technology for subaxial cervical spine. And it still needs to be further verified in clinical practice.

Feasibility of a novel type of complex anterior cervical fixation by using Mimics software

To investigate the feasibility of mimics software in analyzing a new type of complex anterior cervical fixation -- anterior transpedicular screw fixation+zero notch internal fixation. From January 2021 to September 2022, 50 normal pedestrians who underwent cervical spine CT scanning were selected for C1-C7 segment scanning, including 27 males and 23 females, aged from 25 to 65 years old with an average of (46.0 ± 9.0) years old. The dicom format is exported and engraved into the CD, and use the mimics software to perform 3D reconstruction of each segment. A simulated screw is placed on the image according to the critical value of zero notch screw (head and tail angle 44°, internal angle 29°). The position of zero notch screw in each segment is observed to determine the feasibility of anterior transpedicular screw fixation plus zero notch internal fixation. For the upper zero notch screws the three-dimensional images of the cervical spine across all 50 subjects within the C3-C7 segments demonstrated safe position, with no instances of intersection with ATPS. For the lower zero notch screw, in C3-C4 and C4-C5, 4 out of 50 subjects are in the safe position in the three-dimensional images of cervical vertebrae, and 46 cases could achieve secure screw placement when the maximum caudal angle is(32.3±1.9) ° and (36.1±2.2) °, respectively. In C5-C6 and C6-C7 segments, no lower zero notch screws intersected with ATPS, and all screws are in safe positions. Lower cervical anterior pedicle screw fixation plus zero notch internal fixation can achieve successful nail placement through the selected entry point and position.

Rotational stability of thoracolumbar junction fixation systems

Objective To compare the rotational stability of fusion constructs using bisegmental fixation of Th12-L2 vertebrae with anterior stabilization or pedicle screw fixation.Material and Methods The strength, rigidity and limit of elasticity in the “injured vertebral motion segments (VMS) – bisegmental anterior stabilization” system under dislocating rotational loads were estimated. The data obtained were compared with the similar characteristics of the “injured VMS – bisegmental 4-screw transpedicular metal construction” system and intact spine segments.Results Under rotational loads the limits of elasticity of injured spine segments of Th12-L2 with anterior stabilization and transpedicular screw fixation (TSF) is 45.5 and 41.7%, respectively, and the general strength is 66.4% and 80%, respectively, as compared with those intact VMS. Rigidity parameters of anterior-stabilized and pedicle screw fixated VMS with unstable damage of L1 are 60.2 and 93.9%, accordingly, in comparison with those intact VMS.Conclusion No significant differences were observed between bisegmental anterior stabilization and bisegmental pedicle screw fixation of thoracolumbar junction in terms of the key mechanical properties. When treating patients with unstable thoracolumbar spine injuries using bisegmental anterior stabilization or transpedicular fixation with 4-screw spinal system possible rotation motion amplitude of operated segments must not exceed 50% of maximum physiological limits.

Feasibility of anterior pedicle screw fixation in lumbosacral spine: a radiographic and cadaveric study

BackgroundThe anterior pedicle screw (APS) technique for L5 and S1 is crucial for proper anterior lumbar interbody fusion (ALIF). This study aimed to determine the projection, screw trajectory angle, and bone screw passageway length (BSPL), as well as the screw insertion regularity and the operating area within which it is safe to perform insertion.MethodsForty patients with low back pain, all of whom had lumbar computed tomography scans available, was included in this retrospective analysis. Radiographic parameters were measured, including: the distances from the projection to the upper endplate, lower endplate, and midline; the transverse and sagittal screw angles; and the BSPL. In addition, 10 fresh adult cadaveric lumbosacral spine segments were selected to determine the safe anatomic area in which to operate. Finally, APSs were inserted in L5 and S1 to determine the regularity of APS insertion.ResultsWe measured the anterior projection parameters, including: the distances to the upper endplate (L5: 12.5±1.3 mm; S1: 4.54±0.87 mm), lower endplate (L5: 17.3±1.6 mm), and midline (L5: 6.6±0.7 mm; S1: 6.6±0.6 mm); the screw trajectory angle, including the transverse screw angle (L5: 25.3±2.8°; S1: 25.7±2.6°), sagittal screw angle (L5: 17.1±1.7°; S1: 22.4±1.1°); and the BSPL (L5: 48.6±3.5 mm; S1: 48.0±3.5 mm). The regularity of APS insertion in L5 and S1 was determined. Upon the needle reaching a point in the lateral view, it reached the corresponding point in the anteroposterior (AP) view. The anatomic parameters of the safe operating area were as follows: the distance from the abdominal aortic bifurcation to the L5 lower edge (40.50±9.40 mm); the distance from the common iliac vein confluence to the L5 lower edge (27.80±8.60 mm); and the horizontal distance from the inner edge of the common iliac vein to the L5 lower edge (37.50±1.30 mm). We also determined the distance between S1 holes (29.30±1.30 mm), the L5/S1 intervertebral height (17.20±1.50 mm), and the safe operating area (2,058.20±84.30 mm2).ConclusionsThis study has determined the projection, screw trajectory angle, and BSPL of APSs in L5 and S1, their insertion regularity, and the area in which the operation can be safely performed.

Factors influencing the pedicle screw fixation stability in patients with unstable lumbar and thoracolumbar spine injuries

Background. One of the reasons for the lack of standardized approaches for treatment of lumbar and thoracolumbar spine traumatic injuries is inconclusive information on relative contribution of various factors to pedicle screw fixation stability.Objective. To determine risk factors that influence pedicle screw fixation stability in patients with unstable traumatic injuries of a lumbar spine and thoracolumbar junction.Material and methods. This was a retrospective evaluation of 192 spinal instrumentations. Patients with type А3, A4, B1, B2 and C injuries of lumbar and thoracolumbar spine were enrolled. Pedicle screw fixation was used either as a stand-alone technique or in combination with anterior column reconstruction. If required, decompression of nerve roots and spinal cord was performed. Cases with pedicle screw fixation failure were registered. Logistic regression analysis was used to assess predictive significance of potential risk factors. Results. Complication rate growth was associated with a decrease in bone radiodensity, posterior decompression extensiveness, lumbosacral fixation and residual kyphotic deformity. Anterior column reconstruction and additional pedicle screw installation led to a decline in complication rate while anterior decompression and fixation length did not influence fixation stability. Conclusion. In most cases, pedicle screw fixation system failure is associated with altered bone quality; however, surgical approach may also impact complication rate and should be taken into account planning surgical intervention. Anterior column reconstruction and additional pedicle screw installation are associated with the decline in complication rate; the influence of those options is comparable. Anterior decompression does not influence pedicle screw fixation stability; consequently, it is preferable in cases with considerable risk of pedicle screw fixation failure.

251. Additive manufactured Ti-6Al-4V/polyetheretherketone composite porous cage for interbody fusion: bone growth and biocompatibility evaluation in a porcine model

BACKGROUND CONTEXT Several materials have been used to manufacture the cages, the most common being polyetheretherketone (PEEK) and titanium (Ti) alloy (Ti–6Al–4V). Each material has its advantages and disadvantages. PURPOSE The purpose is to utilize the advantages of each material in combination with additive manufacturing technology to develop a new porous Ti alloy/PEEK composite interbody cage. STUDY DESIGN/SETTING In vitro mechanical tests and cell biocompatibility study; in vivo posterior instrumented interbody fusion porcine model. PATIENT SAMPLE In vitro cell culture analysis for Porous Ti alloy/PEEK composite cages. In vivo animal study used 20 female pigs through an anterior intervertebral lumbar fusion and posterior pedicle screws augmentation. Each level was randomly implanted with one of five testing cages. OUTCOME MEASURES In vitro mechanical tests for shear strength of the interface layer. In vitro cell culture analysis for alkaline phosphatase (ALP) activity, ALP and osteocalcin mRNA expression for in vitro study. Micro–computed tomography (CT), back-scattered-electrons SEM (BSE-SEM) and histological analyses for in vivo study. METHODS In vitro and in vivo study compared 5 groups of cages. The first was a commercialized pure PEEK cage (group 1). The second was a Ti alloy/PEEK composite cage with nonporous Ti alloy end plates (group 2). The third, fourth, and fifth groups were composite cages with porosity of 40%, 60%, and 80% (groups 3, 4, and 5), respectively. Mechanical tests, alkaline phosphatase activity and mRNA expression, osteocalcin mRNA expression, SEM were performed for in vitro study. Micro–computed tomography (CT), back-scattered-electrons SEM (BSE-SEM) and histological analyses were performed for in vivo study. RESULTS The shear strength reached 33.4 MPa at the Ti alloy/PEEK interface. ALP activity and ALP mRNA expression were positively correlated with the porosity rate and peaked at 60% porosity. Micro-CT and BSE-SEM demonstrated that structures with high porosities, especially 60% and 80%, facilitated more bone formation inside the implant but not outside the implants. Histological analysis also showed that bone formation was better in Ti alloy groups than in the PEEK group. CONCLUSIONS In vitro cell culture showed higher porous structure exhibited superior bone growth. Micro-CT and histological analyses showed improved bone growth in high-porosity composite cage groups. Composite cage implant takes the biological advantages of Ti alloy porous end plates and the mechanical and radiographic advantages of PEEK central core to incorporate as a single implant suitable for intervertebral fusion. FDA DEVICE/DRUG STATUS Unavailable from authors at time of publication.

A Novel Anterior-Only Surgical Approach for Reduction and Fixation of Cervical Facet Dislocation

The anterior-only surgical procedure, including discectomy, open reduction, fusion, and fixation, is a recommended approach in the treatment of cervical facet dislocations. This approach has a reduction failure rate of up to 40%. When it fails, a posterior approach is usually required. To report a novel anterior-only surgical approach for reduction and fixation in patients with cervical facet dislocation, even for severe vertebral fracture, articular process fracture, and delayed surgical management. Sixty-three consecutive patients with unilateral/bilateral facet dislocation of the subaxial cervical spine were treated with this anterior-only procedure. After discectomy, kyphotic paramedian distraction reduction with Caspar pins plus vertebral screw plate fixation was performed. If the reduction failed, anterior facetectomy reduction plus anterior cervical pedicle screw plate fixation was introduced. Among the 63 patients treated, 52 patients achieved successful reduction with the technique of kyphotic paramedian distraction with Caspar pins; the remaining 11 patients with failure of the former technique experienced successful reduction with the anterior facetectomy technique. No supplemental posterior approach surgery was performed. The American Spinal Injury Association grade was improved by at least 1 grade in 23 patients after this procedure, and no neurologic deterioration occurred in any of the patients. After at least 12 months of follow-up, all patients achieved satisfactory fusion, and there was no implant failure. An anterior-only surgical procedure including kyphotic paramedian distraction with Caspar pins, anterior facetectomy, and anterior pedicle screw plate fixation is safe and effective for subaxial cervical facet dislocations.

Hot issues in diagnosis and treatment of thoracolumbar fractures

In recent years, the surgical treatment of thoracolumbar fractures has made great progress. The thoracolumbar injury classification and severity score (TLICS) of thoracolumbar injuries and the new AO classification, as the most widely used classification score in clinical application, have a clear guiding significance for clinical treatment and scientific research. With the extensive application of CT and MRI, the divergence in the diagnosis of posterior ligament complex (PLC) injury in scoring systems has been narrowed. With the wide application of pedicle screw and the deeper understanding of the anatomical and mechanical characteristics of spine, posterior pedicle screw fixation has been gradually adopted as the major method, while anterior or posterior pedicle screw fixation is only used in special cases. Because of the in-depth study of pedicle screw mechanics, more and more attention has been paid to the fixation of injured vertebrae. Moreover, with the intensive study of sagittal balance of the spine, the reconstruction of injured vertebrae has been proposed as a new concept and further investigated. The author discusses thoracolumbar fracture scoring system, surgical approach, surgical fixation segment, bone graft reconstruction and minimally invasive treatment so as to provide some reference. Key words: Spinal fractures; Thoracic vertebrae; Lumbar vertebrae

A quantitative anatomical study of ideal insertion pathway of anterior axis pedicle screw fixation

Objective To explore an ideal screw insertion point and optimal trajectory for anterior axis pedicle screw (AAPS) so as to provide an anatomical basis for AAPS placement. Methods CT scan of the cervical spine was performed for 40 healthy Chinese adults. Then, the CT data were imported into the Mimics software to reconstruct the three-dimensional images of the axes. The data were divided into two groups according to the gender. The following data were measured: pedicle centerline minimal diameter on both left and right sides, pedicle axial length, the distance between entrance point and upper endplate, the distance between entrance point and median sagittal plane, the distance between entrance point and peak of crista lambdoidalis of C2 vertebral body, extraversion angle and sagittal angle. The screw fixation parameters for AAPS were measured using the Mimics software. Results There was no statistical difference between the left and right sides as well as between the genders(P>0.05). The entrance point for insertion of AAPS was recommended to be on (4.39±0.67)mm from the upper endplate, and on (3.95±0.44)mm from the median sagittal plane. The ideal pedicle axial length was (34.15±2.93)mm, and the pedicle centerline minimal diameter was (7.04±0.87)mm. The distance between the entrance point and the peak of crista lambdoidalis of C2 vertebral body was (1.45±0.19)mm. The ideal extraversion angle was (30.80±2.79)°, and the ideal sagittal angle was (36.35±3.26)°. Conclusion The ideal insertion pathway of AAPS placement can avoid spinal canal, foramen intervertebrale and other important anatomical structure, which is feasible in regard of anatomy. The insertion point can refer to the peak of crista lambdoidalis of C2 vertebral body. However, AAPS placement should be individualized in term of its anatomy variability. Key words: Axis; Pedicle screws; Anatomy

Accuracy of 3D fluoro-navigated anterior transpedicular screws in the subaxial cervical spine: an experimental study on human specimens.

Pedicle screw stabilization, the standard technique in the thoracic and lumbar spine, is increasingly used in the cervical spine. Initial studies on the use of anterior pedicle screws (ATPS) in the cervical spine have been recently published. ATPS use has theoretical advantages over posterior stabilization. We have already established a 3D-fluoroscopy navigation setup in a study of artificial bones. The aim of the current study was to evaluate the positioning quality/accuracy of ATPS introduced to human specimens. 36 cannulated screws (3.5mm) were implanted anteriorly into the C3-C7 segments of four spines (unfixed, frozen, cadaveric specimens) using a 3D-fluoroscopy navigation system. Placement accuracy was evaluated using a recently published classification on postoperative CT scans. Grade 1 is perfect position with pedicle wall perforation <1mm, grade 2 is perforation <2mm, etc., and finally grade 5 is cortical perforation of >4mm and/or transverse foramen entry. 36 anterior pedicle screws were inserted into four human cervical spine specimens. Of these, seven screws were introduced to C3, five to C4 and eight each to C5, C6, and C7. Classified with the modified G&R, 21 of 36 (58.3%) were grade 1. Ten screws (27.8%) were grade 2. Grade 4 was assessed for two screws and grade 5 for three. Customary "good" positioning, combining grades 1 and 2, was thus found in 86.1%. Five screws (13.9%) did not meet this criterion (grade ≥3). With 86.1% of good positioning (grade 2 or better), a 3D-fluoroscopy navigation of ATPS screws into human c-spine specimens achieved a satisfying results. These are at least comparable to results presented in the literature for posteriorly introduced subaxial pedicle screws.

Modified pedicle screw\u2013rod fixation as a minimally invasive treatment for anterior pelvic ring injuries: an initial case series

BackgroundUnstable pelvic ring injuries often involve high mortality and morbidity. This study was aimed to evaluate the modified minimally invasive pedicle screw–rod fixation for anterior pelvic ring injuries, in the respects of its feasibility, merits, and limitations.MethodsTwenty-three patients with unstable pelvic ring injuries underwent the modified anterior pedicle screw–rod fixation, with or without posterior fixation. The clinical outcomes were assessed using Majeed scores, and the quality of reduction was evaluated according to the criteria of Matta.ResultsMajeed scores showed that the clinical outcomes at postoperatively 1 year were excellent in 14 patients, good in 7, and fair in 2. One woman complained of persistent pain at the pubic tubercle during sexual intercourse. Iatrogenic neuropraxia of the unilateral lateral femoral cutaneous nerve occurred in 3 patients. Unilateral femoral nerve palsy occurred in 1 patient. The reduction was found to be excellent in 12 patients, good in 8, and fair in 3. Heterotopic ossification occurred in 8 patients, all being asymptomatic.ConclusionsThe modified pedicle screw–rod fixation with the minimally invasive technique offered an effective alternative for unstable anterior pelvic ring injuries.

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

Accuracy of 3D fluoroscopy-navigated anterior transpedicular screw insertion in the cervical spine: an experimental study

The technique of pedicle screw stabilization is finding increasing popularity for use in the cervical spine. Implementing anterior transpedicular screws (ATPS) in cervical spine offers theoretical advantages compared to posterior stabilization. The goal of the current study was the development of a new setting for navigated insertion of ATPS, combining the advantage of reduced invasiveness of an anterior approach with the technical advantages of navigation. 20 screws were implanted in levels C3 to C6 of four cervical spine models (SAWBONES(®) Cervical Vertebrae with Anterior Ligament) with the use of 3D fluoroscopy navigation system [Arcadis Orbic 3D, Siemens and VectorVision fluoro 3D trauma software (BrainLAB)]. The accuracy of inserted screws was analyzed according to postoperative CT scans and following the modified Gertzbein and Robbins classification. 20 anterior pedicle screws were placed in four human cervical spine models. Of these, eight screws were placed in C3, two screws in C4, six screws in C5, and four screws in C6. 16 of 20 screws (80%) reached a grade 1 level of accuracy according to the modified Gertzbein and Robbins Classification. Three screws (15%) were grade 2, and one screw (5%) was grade 3. Grade 4 and 5 positions were not evident. Summing grades 1 and 2 together as "good" positions, 95% of the screws achieved this level. Only a single screw did not fulfill these criteria. The setting introduced in this study for navigated insertion of ATPS into cervical spine bone models is well implemented and shows excellent results, with an accuracy of 95% (Gertzbein and Robbins grade 2 or better). Thus, this preliminary study represents a prelude to larger studies with larger case numbers on human specimens.

Anterior pedicle screw and plate fixation for cervical facet dislocation: case series and technical note

Background ContextThe anterior-only surgical procedure is used as a recommended approach in the treatment of cervical facet dislocations, but an anterior cervical spine implant that offers higher three-column instabilities for stronger fixation is lacking. PurposeThis study aimed to report a new surgical technique of anterior pedicle screw (APS) fixation for cervical facet dislocations and the results of 12 patients with successful application and described safety. Study DesignThe study design includes case series and technical report. Patient SampleThe sample comprises 12 patients with cervical facet dislocations. Outcome MeasuresAnalyses of plain lateral neutral and oblique radiographs and computed tomography scans were conducted to assess reduction, fusion, and the accuracy of pedicle screw placement. Spinal cord compression and decompression was defined by a 1.5-Tesla magnetic resonance imaging. Neurologic status was evaluated according to classification of American Spinal Injury Association (ASIA). MethodsTwelve patients with cervical facet dislocations were surgically treated by the anterior cervical pedicle screw and plate fixation. In these 12 patients (9 male and 3 females), the distribution of spine level was from C3–C4 to C6–C7; the etiologic diagnosis included four unilateral and eight bilateral facet dislocations; the neurologic status comprised four patients with ASIA A, two with ASIA B, two with ASIA D, and four with ASIA E. After discectomy, reduction, and insertion of a peek cage containing autologous bone graft, the APS was inserted along the pedicle axis with the fluoroscope-assisted view imaging. ResultsPostoperatively, all patients had obtained successful reduction and satisfactory anatomic sagittal alignment. There was no complication or instrument failure owing to the use of this technique. Four ASIA A and one ASIA B patients showed no neurologic improvement; one ASIA B patient was improved neurologically to ASIA C; two patients with ASIA D were improved neurologically to ASIA E; no ASIA E patients showed neurologic deterioration. ConclusionsAnterior pedicle screw and plate fixation represents a safe and efficacious but technically challenging option for the treatment of cervical facet dislocations.

Radiographic and clinical assessment on the accuracy and complications of C1 anterior lateral mass and C2 anterior pedicle screw placement in the TARP-III procedure: a study of 106 patients.

To investigate the (1) radiographic and clinical accuracy of C1 anterior lateral mass screw (C1ALMS) and C2 anterior pedicle screw (C2APS) placement in the transoral atlantoaxial reduction plate (TARP)-III procedure, (2) screw insertion-associated clinical complications and (3) fusion status between C1 and C2. Radiographic and clinical data were obtained from the electronic medical record system. Studies were carried out to assess the accuracy of C1ALMS and C2APS placement, the screw insertion-associated clinical complications and the fusion status between C1 and C2. Placement of the screws was assessed using the modified All India Institute of Medical Sciences outcome-based classification. Two-hundred and twelve C1ALMS and 207 C2APS in 106 patients were assessed. The ideal accurate rates were 92.0% (195) and 53.1% (110), and the acceptable accurate rates were 97.6% (207) and 87.0% (180), respectively. One patient died postoperatively due to C2 screw misplacement. There were no symptoms of neurologic and vertebral artery injuries in the rest of the patients. 102 patients (97.1%) achieved solid fusion between C1 and C2. No instrumentation failure due to delayed union or nonunion was observed. C1ALMS placement in TARP-III procedures appears to be safe. The cortical breach rate of C2APS is high though clinically the neurovascular complication rate is similar to that of posterior atlantoaxial procedures. Advanced navigation strategies may help improve the accuracy of C2APS placement and decrease potential complications.

English

Introduction Osteonecrosis of the vertebral body, also known as Kummell’s disease, occurs relatively rarely after vertebral compression fractures. However, as the life expectancy and resulting osteoporosis are on the rise, the incidence of the disease is bound to increase. We attempt to review the literature and discuss the future challenges about this not so well-known entity. The update is accompanied by a representative case report. Case Report A 58-year-old physician presented with pain in mid-back region for a period of 15 days with a similar episode 5 months back lasting 3 weeks. Diagnosis of Kummell’s disease was established on history pattern and radiographic examination. Anterior decompression and posterior pedicle screw fixation was performed in same sitting. Conclusion A thorough knowledge of Kummell’s disease and index of suspicion in appropriate situations is necessary for detection and discharge of effective

Anterior pedicle screw fixation of C2: an anatomic analysis of axis morphology and simulated surgical fixation

Human cadaveric study measuring the morphology of C2 vertebra, description of anterior placement of pedicle screw with post-fixation computed tomography (CT) analysis. To assess the potential feasibility and safety anterior placement of C2 pedicle screws. Posterior pedicle screw fixation has become an established technique for upper cervical reconstruction. To our knowledge few reports in the previous literature have described the placement of or anatomy related to anteriorly approach C2 pedicle screws. The morphology of 60 human C2 vertebrae was measured directly to assess the size, position, and relative approach angle of the pedicles from an anterior perspective. In an additional 20 cadaveric cervical spines, bilateral 3.5 mm titanium C2 pedicle screws were placed and analyzed for pedicle morphology and placement accuracy with thin cut, 1 mm axial CT. The mean C2 pedicle width measured directly and by CT scan was 7.8 and 6.6 mm, and the average length of the right and left pedicle was 26.4 and 25 mm, respectively. The mean transverse angle (α) was 17.6° and 21.4°, whereas declination angle (β) anterior to posterior was 13.8° and 10.6°, respectively. Quantitative data regarding C2 pedicle shape and location with respect to the anterior placement of pedicle screws have not been previously reported. This study indicates that anterior placement of 3.5 mm C2 pedicle screws through a transoral approach may be both feasible and safe and also provides an important anatomic analysis that may guide clinical application.

Surgical treatment strategies of odontoid fractures

To explore the characteristics of both odontoid fractures and adjacent section instability so as to devise proper surgical strategies and achieve better curative effect. A total of 37 patients (including 26 males and 11 females) with odontoid fractures treated from January 2005 to June 2012 with a mean age of (21-65) 36 years were analyzed retrospectively. Among 25 cases of simple odontoid fractures, there were type II (n = 20) and low type III (n = 5). There were 12 cases of odontoid fractures with adjacent section instability with C1/2 instability (n = 6), C2/3 instability (n = 4) and C1/2 and C2/3 instability (n = 2). The Frankel scale was used to assess nerve function. There were Grade A (n = 1), Grade B (n = 2), Grade C (n = 3) and Grade D (n = 6) at preoperation. Treatment included anterior and/or posterior pedicle screw fixation for reducing fracture and stabilizing upper cervical vertebrae. The Japanese Orthopedic Association (JOA) standards were used to evaluate the therapeutic effect. According to Frankel grade, nerve functional restoration of spinal cord injury was gauged. Fracture healing, bone graft fusion and spinal stability were monitored by radiology or computed tomography. All patients underwent surgery safely without severe complications. The average follow-up period was 18 (12-48) months. There was significant difference (t = 13.464, P = 0.000) in JOA score between pre-operation (12.11 ± 2.09) and post-operation (15.36 ± 3.17). And the rate of improvement was 90.8% ± 11.6% and that of "excellent" or "good" 98%. Degree 1-2 recovery of neural function was achieved in all except for 1 case of Frankel B. All patients were immobilized in a hard collar for 3 months postoperatively. Fusion occurred in all cases within a mean time of (3-6) 4.5 months. Radiology confirmed a proper screw position at postoperation. There were no occurrences of such complications as loosening, displacement or breakage of internal fixations. Proper surgical approaches may be selected according to the characteristics of both odontoid fractures and adjacent section instability.

Anterior internal fixator versus a femoral distractor and external fixation for sacroiliac joint compression and single stance gait testing: a mechanical study in synthetic bone

The purpose of this study was to evaluate the biomechanical stability and compressive forces across the sacroiliac (SI) joint of an anterior internal fixator compared to the femoral distractor and external fixator for vertically unstable pelvic fractures. Five composite pelvises with a simulated APC type III injury fixed with a femoral distractor, external fixator, or anterior internal fixator were tested. A pressure-sensitive film (Tekscan) was placed in the disrupted SI joint recording the magnitude of force. Then, in a single-leg stance model (Instron machine), a load was applied through the sacrum. We recorded displacement at the pubic symphysis and SI joint using high-speed video. Peak load and displacement were measured, and axial stiffness was calculated. Values were compared using a Student's t-test (p < 0.05). The SI joint was compressed significantly (p < 0.001) more using the anterior internal fixator (18.9 N) and femoral distractor (18.6 N) than the two-pin external fixator (2.5 N). There was no significant difference between the anterior internal fixator and the femoral distractor in displacement at the SI joint. The pubic symphysis displaced less with the femoral distractor than the anterior internal fixator (5.5 mm vs. 4.1 mm; p < 0.05). The anterior pedicle screw internal fixator allows for indirect compression across the sacroiliac joint that is superior to two-pin external fixation and comparable to the femoral distractor. The anterior internal fixator may be an option for temporary anterior pelvic fixation in situations where external fixation or the femoral distractor have otherwise been used.

Preliminary clinical application of anterior pedicle screw fixation of lower cervical spine

Objective To discuss the feasibility and safety of anterior pedicle screw (APS) fixation in treatment of lower cervical spine injuries. Methods A total of 10 patients with lower cervical spine injuries were treated with APS fixation.All the patients received preoperative cervical CT scans,and then three-dimensional model was reconstructed by using Mimics software to measure the screw placement parameters (insertion point,screw placement angle,screw length and diameter).All APS fixations were performed through anterior cervical approach,and then centrums antetheca and bilateral outer edges were exposed to distinguish the vertebral end plates.Screw insertion was strictly operated under the fluoroscopic assistance and preoperative screw placement parameters.The postoperative efficacy of APS fixation was evaluated by radiologist and other orthopedist via anteroposterior and lateral radiation,CT scan,three-dimensional model reconstruction and MRI.A follow-up was carried out at 1,3,6 and 12 months after operation. Results Except for one screw for C4 and one for C7,another 24 crews for C3-C7 were successfully inserted.Postoperative CT scan demonstrated four screws breaking the outer vertebral wall.Except for one patient suddenly died from acute myocardial infarction one week after operation,the other nine patients received follow-up.Of three trauma patients,one patient at Grade A did not get improvement but with no aggravation and two achieved improvement for 2-3 grades according to Frankel grade.Among six non-trauma patients,spinal function score by JOA was averagely elevated to 13.4 points,with improvement rate of 60.7％ according to Hirabayashi method.There were no serious complications except for two patients of dysphagia among the patients who were followed up. Conclusions APS fixation is feasible for lower cervical spine injuries.The keys to successful screw insertion are preoperative measurement of individualized screw insertion parameters and appropriate application of intraoperative fluoroscope technique. Key words: Cervical vertebrae; Internal fixators; Pedicle screw