C1–2 transarticular screws combined with C1 laminar hooks fixation: a modified posterior atlantoaxial fixation technique and outcome in 72 patients

Purpose

To retrospectively evaluate the outcome of C1–2 transarticular screws combined with C1 laminar hooks fixation.

Methods

All patients underwent atlantoaxial fixation during a 5-year period. The surgical technique and treatment procedures were intensively reviewed and clinical symptoms, neurological function and imaging appearance were retrospectively evaluated.

Results

The clinical and radiology follow-up indicated a stable arthrodesis and clinical relief from symptoms for all patients. All patients with neurological defects improved an average of 1.33 grade at their most recent clinical assessment, P < 0.05; their average admission ASIA motor score, pin prick score and light touch score improved to an average follow-up ASIA score of 99.80 (99.83 ± 0.38), 111.83 (111.83 ± 0.45), and 111.89 (111.89 ± 0.32), respectively. No neurovascular impairment and case of implant failure were observed.

Conclusions

The C1–2 transarticular screws combined with C1 laminar hooks fixation is a reliable technique for atlantoaxial instability.     

Bilateral C1 laminar hooks combined with C2 pedicle screws fixation for treatment of C1–C2 instability not suitable for placement of transarticular screws

The study design described here is a posterior C1–C2 fusion technique composed of bilateral C1 hooks and C2 pedicle screws. In addition, the clinical results of using this method on 13 patients with C1–C2 instability are reported. The objectives are to introduce a new technique for posterior C1–C2 fusion and to evaluate the clinical outcome of using it to treat C1–C2 instability. From October 2006 to August 2008, 13 patients (9 men and 4 women) with C1–C2 instability were included in this study: 3 had acute odontoid fractures, 4 had obsolete odontoid fractures, 4 had os odontoideum and 2 had traumatic rupture of the transverse ligament. All patients underwent posterior atlantoaxial fixation with bilateral C1 hooks and C2 pedicle screws. The mean follow-up duration was 25 months (range 13–30 months). Each patient underwent a complete cervical radiograph series, including anterior–posterior, lateral, and flexion–extension views, and a computed tomographic scan. The clinical course was evaluated according to the Frankel grading system. No clinically manifested injury of the nerve structures or the vertebral artery was observed in any of these cases. Five patients with neurological symptoms showed significant improvement in neurological function postoperatively. Bony fusion and construction stability were observed in all 13 patients (100%) on their follow-up radiographs, and no instrument failure was observed. Bilateral C1 hooks combined with C2 pedicle screws can be used as an alternative treatment method for C1–C2 dislocation, especially in cases not suitable for the use of transarticular screws. The clinical follow-up shows that this technique is a safe and effective method of treatment.     

Morphological and clinical feasibility of C3 pedicle screw instrumentation in patients with congenital C2–3 fusion

Purpose

Congenital C2–3 fusion (C2–3CF) is often involved in patients with atlantoaxial dislocation, and posterior occipitocervical fixation surgery is usually required. Hypoplasia of C2 pedicle is common in such patients, making C2 pedicle screws (PS) instrumentation inapplicable. Because of congenital fusion, C3PS instrumentation would be an ideal alternative for it will not sacrifice an additional motion segment; however, the morphological and clinical feasibility has not been previously reported.

Methods

We included 42 C2–3CF patients to this study and evaluated pedicle trajectories of C2 and C3 using a three-dimensional CT. Clinical applications of C3PS instrumentation were evaluated and followed.

Results

Among the 42 patients, 23 (54.8 %) and 8 (19.0 %) had C2 and C3 pedicle trajectory diameters <4.0 mm, respectively. The bisection line of the fused C2–3 lamina was used to represent the superior border of C3 articular mass; the entry point of C3 pedicle was located at 3 mm inferior to the assumed superior border and 3.2 mm medial to the lateral border. Bilateral C3PS instrumentations were successfully adopted in 22 patients. No spinal cord or vertebral artery injury occurred; postoperative CT showed a trajectory breach rate of 17.4 % for C3PS. After mean of 3.6-year follow-up, no implant failure was documented.

Conclusions

C3PS instrumentation is morphologically and clinically feasible for a large proportion of patients with C2–3CF and can serve as another reliable alternative for C2PS instrumentation. Preoperative evaluation of pedicle trajectory of C2–3CF with three-dimensional CT is highly valuable in the choice of proper fixation methods.     

C2 translaminar screw as the optimal choice for atlantoaxial dislocation with C2–C3 congenital fusion

Objective and importance  

The entry point and trajectory are very important for transarticular screw (TAS) and C2 pedicle screw (PDS) plantation. When the physical size is not large enough for the screw passing through, an accurate entry point is the most important point for successful screw insertion without vertebral artery (VA) injury and spinal cord injury. Once the laminas of C2 and C3 are fused, the normal anatomic mark might disappear and the insertion point would be hard to find. As a result, the complication of TAS or PDS implantation increases rapidly. We used C2 translaminar screws (TLSs) with C1 lateral mass screws as the optimal fixation for atlantoaxial dislocation in order to reduce the risk of VA injury and spinal cord injury.     

Superior pubic ramus fractures fixed with percutaneous screws: what predicts fixation failure?

OBJECTIVE: The purpose of this study is to present the early complications of percutaneous screw fixation of superior pubic ramus fractures and to present a new classification scheme for superior pubic ramus fractures. DESIGN: Retrospective. SETTING: Level 1 trauma center. PATIENTS: One hundred and twelve patients with pelvic fracture between the ages of 14 to 89 years underwent percutaneous screw fixation of 145 pubic ramus fractures. Eighty-one patients with 107 surgically repaired fractures were followed to fracture union. Follow-up averaged 9 months (range 2-52 months). One additional patient who sustained fixation failure 4 days after surgery was included to yield a study group of 82 patients with 108 surgically repaired ramus fractures. INTERVENTION: Patients underwent percutaneous screw fixation of a superior pubic ramus fracture. MAIN OUTCOME MEASUREMENTS: Superior pubic ramus fractures were classified according to a new scheme, the Nakatani system, which categorizes superior ramus fractures according to location with respect to the obturator foramen. Patient radiographs were examined for evidence of loss of reduction, defined as any motion at the ramus fracture site or hardware motion, after fracture surgery. RESULTS: Of the 82 patients followed to union or fixation failure, 12 (15%) had loss of reduction on follow-up radiographs. The average age of patients who lost reduction was 55 years. The most common mechanism of reduction loss was a collapse of the pubic ramus over the screw, with recurrence of an internal rotation deformity of the injured hemipelvis. Ten patients who lost reduction were women, and 11 had undergone ramus screw placement in retrograde fashion. No loss of reduction was seen in Zone III ramus fractures (those that involve the bone lateral to the obturator foramen). No patient sustained recognized neurologic, vascular, or urologic injury as a result of percutaneous screw fixation of a superior pubic ramus fracture. CONCLUSIONS: The prevalence of loss of reduction after percutaneous screw fixation of pubic ramus fractures is 15%. Loss of reduction is more common in elderly and female patients and in patients whose ramus screws are placed in a retrograde fashion. Also, loss of reduction appears to be more common in fractures medial to the lateral border of the obturator foramen.     

Mini-open approach combined with percutaneous transarticular screw fixation for C1–C2 fusion

This paper describes a limited exposure for posterior C1–C2 arthrodesis aided by percutaneous transarticular fixation. The purpose of this study was to report the fusion rate using the aforementioned method. Fifty-seven patients (54 females and three males) with C1–C2 instability due to rheumatoid disease constituted the material of this study. The exposure was restricted to C0–C3 levels. The drilling and insertion of the screws was done through two mini stab wounds. A special sleeve and screwdriver were developed to facilitate this step. An autogenous iliac bone graft was fixed between the decorticated posterior arch of the atlas and the lamina of the axis vertebra. The mean of the atlantodental interval decreased from 8.5 mm (SD 2.3 mm) to 2.6 mm (SD 0.6 mm) at the immediate postoperative periods and reached 2.7 mm (SD 0.7 mm) after a mean follow-up of 30.4 months (SD 5.6 months). Malposition of the screws was observed in two patients and warranted a second operation in one. Fusion was evident in 98% of the cases. Percutaneous insertion of the screws in posterior C1–C2 transarticular fixation reduces the size of the exposure and the surgical trauma to the cervical segments below the fixation.     

Pedicle anatomy in a patient with severe early-onset scoliosis: can pedicle screws be safely inserted?

OBJECTIVE: With the rapid increase in the use of pedicle screws in the thoracic spine for various pathologies, knowledge of the pedicle anatomy is critical. Previous authors, in discussing pedicle morphology, have usually reported their findings in nondeformed adult specimens. More recently, the use of pedicle screws in adolescent idiopathic scoliosis has been reported. METHODS: The authors studied the pedicle diameters in the spine of a patient with infantile idiopathic scoliosis who died at age 28 of cor pulmonale. The concave pedicles from T6 to L3 were measured both directly and with thin-section computed tomography (CT) scanning (the curve apex was T8-T11). RESULTS: By direct measurement, the concave pedicle width at its narrowest point (the isthmus) ranged from 2.9 (T9) to 6.7 (L1, L3) mm. Three apical concave pedicles (T8, T9, T10) had no cancellous cavity. By CT scan measurement, the four apical concave pedicles measured 3.4 (T8), 2.8 (T9), 2.6 (T10), and 3.4 (T11) mm, respectively. CONCLUSIONS: In conclusion, the authors confirm others' findings that the concave pedicles can be so small that pedicle screw insertion is impossible. We also found that these findings can be confirmed preoperatively with thin-section CT scanning. In such situations, extrapedicular screw placement should be considered.     

Nitrofen-induced congenital diaphragmatic hernia in rat embryo: what model?

Purpose

The aim of this study was to investigate the natural history of congenital diaphragmatic hernia (CDH) in rat embryos with special attention to the pathomorphologic changes of diaphragm, liver, intestines, and lungs at various stages of embryonic development.

Methods

Pregnant Sprague-Dawley rats were given, via a gavage tube, 100 mg nitrofen (Wako Chemicals, Neuss, Germany) on day 10.5 of gestation. Fetuses were harvested by laparotomy on day 15.5, 16.5, 18, and 21. Anatomic study of the diaphragm, herniated viscera, and lungs was performed under stereoscope with special attention to the diaphragmatic defect.

Results

CDH occurred in 44 embryos on right, in 10 on the left, and in 34 bilateral. In the youngest embryos, the small defect was located in the dorsomedial portion of the diaphragm very close to the aortic hiatus. During pregnancy, the defect enlarged progressively to occupy more than half of the affected hemidiaphragm on day 21. In all animals, regardless of their age and side of the defect, the liver was found inside the chest. The intrathoracic mass was formed by ingrown hepatic tissue originating from the dorsal surface of the intraabdominal liver. It appeared as an accessory liver lobe. The amount of intrathoracic liver increased rapidly. From around day 18, the thoracic portion of liver, when examined in sagittal plane, was bent forward and assumed an uncinate shape. The stomach and small bowel loops were displaced into the chest in the oldest examined fetuses. The first sign of reduction of size of the lung was seen in 16, 5-day old embryos, and at further stages of embryonic development the lung growth impairment strictly paralleled the ingrowth of the liver. The natural history of the right and left CDH were very similar. In fetuses with bilateral CDH, asymmetry regarding size of the defect and volume of intrathoracic hepatic mass was noted with larger defects on the left side in more than 60% of animals.

Conclusions

Pathogenesis of nitrofen-induced diaphragmatic defect in the rat embryo and CDH in the human fetus seem to differ significantly. Nitrofen induces a complex malformation of the embryonic diaphragm and the liver. CDH in rat embryo bears more resemblance to a model of space-occupying lesion than to human CDH. The induction of localized hepatic proliferation may be a result of disturbance of as yet unknown regulatory interaction between hepatic and mesenchymal diaphragmatic cells.     

Pedicle morphology in thoracic adolescent idiopathic scoliosis: is pedicle fixation an anatomically viable technique?

STUDY DESIGN: A radiographic study of thoracic pedicle anatomy in a group of adolescent idiopathic scoliosis (AIS) patients. OBJECTIVE: To investigate the anatomic constraints of the thoracic pedicles and determine whether the local anatomy would routinely allow pedicle screw insertion at every level. SUMMARY OF BACKGROUND DATA: In spite of the clinical successes reported with limited thoracic pedicle screw-rod constructs for thoracic AIS, controversy exists as to the safety of this technique. MATERIAL AND METHODS: Twenty-nine patients with right thoracic AIS underwent preoperative thoracic CT scans and plain radiographs. Anatomic parameters were measured from T1 to T12. RESULTS: Information on 512 pedicles was obtained. The transverse width of the pedicles from T1 through T12 ranged from 4.6-8.25 mm. The medial pedicle to lateral rib wall transverse width from T1 through T2 ranged from 12.6 to 17.9 mm. Measured dimensions from the CT scans showed the actual pedicle width to be 1-2 mm larger than would have been predicted from the plain radiographs. Age, Risser grade, curve magnitude, and the amount of segmental axial rotation did not correlate with the morphology or size of the thoracic pedicles investigated. In no case would pedicle morphology have precluded the passage of a pedicle screw. CONCLUSION: Based on the data identified in this group of adolescent patients, it is reasonable to consider pedicle screw insertion at most levels and pedicle-rib fixation at all levels of the thoracic spine during the treatment of thoracic AIS.     

Low-density versus high-density thoracic pedicle screw constructs in adolescent idiopathic scoliosis: do more screws lead to a better outcome?

Background contextThoracic pedicle screw (TPS) constructs have improved curve correction measurements compared with hook and hybrid constructs in the treatment of adolescent idiopathic scoliosis (AIS), but the optimal implant density, or the number of screws per level, remains unknown in the treatment of flexible thoracic curves.PurposeTo determine how implant density affects clinical outcome, radiographic outcome, and cost in the treatment of Lenke Curve Type I AIS.Study designA retrospective clinical study.Patient sampleNinety-one consecutive AIS patients with Lenke Type I curves who underwent surgical correction with a minimum follow-up of 24 months.Outcome measuresRadiographic outcomes included assessment of preoperative and 2-year postoperative thoracic Cobb angle, T5–T12 kyphosis, and curve flexibility. We also assessed SRS-22 outcome measures and thoracic angle of trunk rotation (ATR) before surgery and at the 2-year postoperative time point. The cost of each construct was also evaluated.MethodsBivariate analysis was conducted between implant density and the following factors: percent correction of the major curve, ATR, and change in kyphosis. The correlation between curve flexibility and percent correction of the major curve was determined. Patients were then divided into two groups: the low-density (LD) TPS group defined by implant density below the mean number of screws per level for the entire cohort (less than 1.3 screws per level) and the high-density (HD) TPS group defined by implant density above the mean number of screws per level (more than 1.3 screws per level). Independent sample t tests were used to compare demographic data as well as radiographic and clinical outcomes at baseline and at follow-up between the two groups.ResultsSixty-one female and 30 male patients met inclusion criteria. No significant correlations were found between implant density and the following parameters: percent correction of the major curve (p=.25), ATR (p=.75), and change in T5–T12 kyphosis (p=.40). No correlation was found between curve flexibility and percent correction of the major curve (p=.54). The LD group consisted of 57 patients, whereas the HD group had 34 patients. There were no differences between the HD group and the LD group in regard to major curve correction, change in T5–T12 kyphosis, or change in ATR. Total implant costs were significantly higher in the HD group ($13,272 vs. $10,819; p<.01). The SRS-22 image domain and overall score improved at 2 years within both groups, but there were no group differences in any of the SRS-22 domains or the overall score.ConclusionsWe identified no clinical, radiographic, perioperative, or complication-related advantage of constructs with higher TPS implant density in this patient cohort with flexible idiopathic scoliosis. Cost was significantly higher with HD constructs in comparison with LD constructs. Optimal implant density chosen by the surgeon should rely on a number of factors including curve magnitude and rigidity, bone density, and desired correction.     

Type C pelvic ring injuries in polytrauma patients: can percutaneous iliosacral screws reduce morbidity and costs?

Forty-two polytrauma patients with pelvic injuries were included in this retrospective study to evaluate the benefits of percutaneous iliosacral screwing. All patients were followed up for at least 1 year, and their mean age was 39 years. According to Tile’s classification, all cases were type C pelvic injuries. After primary anterior fixation, the iliosacral screws were applied percutaneously. Twenty-two cases had excellent reduction, 15 cases had good reduction, 4 cases had fair reduction and one case had poor reduction. The unsatisfactory final displacements were common among dislocations of the sacroiliac joints and operated cases during the second week. The final clinical outcome was satisfactory in 31 cases and unsatisfactory in 11 cases. Unsatisfactory clinical results were due to persistent posterior pelvic pain and limited activities in 7 cases and residual neurological disability in four cases. No posterior infection or iatrogenic nerve injuries were encountered; however, two cases had loosening of the applied improper screws. There was significant direct reduction in the hospital stay, transfused blood amount, ventilator time and complications when the percutaneous iliosacral screwing was carried out early during the first week. Therefore, indirect reduction in the hospital cost and polytraumatized patient morbidity was achieved.     

Inflammation in uremic patients: what is the link?

Uremic patients suffer to an extremely high degree from cardiovascular disease. Cardiovascular disease results mainly from atherosclerotic remodeling of the arterial system. Inflammation is considered to contribute significantly to development of atherosclerosis, and albeit many different factors may lead to inflammation, generation of enhanced oxidative stress is believed to be an important common feature of pro-inflammatory causes. Studies in the general population without renal disease could clearly show that markers of inflammation, in particular C-reactive protein, predict the cardiovascular risk. In this review article, we discuss the presence and the predictive value of inflammation in patients with end-stage renal disease, and analyze whether uremic patients are exposed to specific pro-inflammatory and pro-oxidative conditions. Particular emphasis is set on oxidative stress induced by oxidatively modified lipoproteins and angiotensin II. Based on pathophysiological considerations valid for uremic patients, we discuss therapeutical options that might help to reduce cardiovascular disease in uremic patients.     

Modified technique for C1–2 screw-rod fixation and fusion using autogenous bicortical iliac crest graft

Introduction  

Various techniques have been described for posterior atlantoaxial fusion. Sublaminar passage of the wire/cable is cumbersome with a risk of spinal cord injury. Packing morselized bone grafts into the C1–2 facet joints may be difficult and it may cause massive bleeding and neuropathic pain or posterior scalp numbness postoperatively. We introduce a modified method by using C1–2 screw-rod fixation (SRF) to compress a structural iliac bone graft between the posterior elements of C1 and C2 without supplemental wiring construct.     

C1–C2 type Harms internal fixation for unstable C2 fracture in a 6-year-old boy: Case report

BackgroundDecision-making is often difficult in odontoid fracture in children.Case reportWe present the case of a 6-year-old boy who sustained cervical trauma on falling out of a tree. Initial cervical X-ray and CT-scan did not find any traumatic lesion. Three-week check-up revealed an unstable C2 fracture in the synchondrosis at the base of the odontoid bone, with anterior displacement (type IC on the classification of Hosalkar et al.), without neurological symptoms except for cervical pain and limitation of head rotation. MRI confirmed the absence of medullary lesion. The Harms technique was used to fix C1 and C2, using adult instrumentation without bone graft. Bone fusion was obtained at 8 months. Hardware was removed at 10 months. No complications were reported.ConclusionsPosterior internal fixation for unstable C2 fractures in children can be effective and relatively safe.     

Risk of vertebral artery injury: comparison between C1–C2 transarticular and C2 pedicle screws

Background contextTo our knowledge, no large series comparing the risk of vertebral artery injury by C1–C2 transarticular screw versus C2 pedicle screw have been published. In addition, no comparative studies have been performed on those with a high-riding vertebral artery and/or a narrow pedicle who are thought to be at higher risk than those with normal anatomy.PurposeTo compare the risk of vertebral artery injury by C1–C2 transarticular screw versus C2 pedicle screw in an overall patient population and subsets of patients with a high-riding vertebral artery and a narrow pedicle using computed tomography (CT) scan images and three-dimensional (3D) screw trajectory software.Study designRadiographic analysis using CT scans.Patient sampleComputed tomography scans of 269 consecutive patients, for a total of 538 potential screw insertion sites for each type of screw.Outcome measuresCortical perforation into the vertebral artery groove of C2 by a screw.MethodsWe simulated the placement of 4.0 mm transarticular and pedicle screws using 1-mm-sliced CT scans and 3D screw trajectory software. We then compared the frequency of C2 vertebral artery groove violation by the two different fixation methods. This was done in the overall patient population, in the subset of those with a high-riding vertebral artery (defined as an isthmus height ≤5 mm or internal height ≤2 mm on sagittal images) and with a narrow pedicle (defined as a pedicle width ≤4 mm on axial images).ResultsThere were 78 high-riding vertebral arteries (14.5%) and 51 narrow pedicles (9.5%). Most (82%) of the narrow pedicles had a concurrent high-riding vertebral artery, whereas only 54% of the high-riding vertebral arteries had a concurrent narrow pedicle. Overall, 9.5% of transarticular and 8.0% of pedicle screws violated the C2 vertebral artery groove without a significant difference between the two types of screws (p=.17). Among those with a high-riding vertebral artery, vertebral artery groove violation was significantly lower (p=.02) with pedicle (49%) than with transarticular (63%) screws. Among those with a narrow pedicle, vertebral artery groove violation was high in both groups (71% with transarticular and 76% with pedicle screws) but without a significant difference between the two groups (p=.55).ConclusionsOverall, neither technique has more inherent anatomic risk of vertebral artery injury. However, in the presence of a high-riding vertebral artery, placement of a pedicle screw is significantly safer than the placement of a transarticular screw. Narrow pedicles, which might be anticipated to lead to higher risk for a pedicle screw than a transarticular screw, did not result in a significant difference because most patients (82%) with narrow pedicles had a concurrent high-riding vertebral artery that also increased the risk with a transarticular screw. Except in case of a high-riding vertebral artery, our results suggest that the surgeon can opt for either technique and expect similar anatomic risks of vertebral artery injury.