Occipitocervical fusion with C1 laminectomy in children

Complications of Posterior Fusion for Atlantoaxial Instability in Children With Down Syndrome

Objective

To clarify the complications of posterior fusion for atlantoaxial instability (AAI) in children with Down syndrome and to discuss the significance of surgical intervention.

Methods

Twenty pediatric patients with Down syndrome underwent posterior fusion for AAI between February 2000 and September 2018 (age, 6.1±1.9 years). C1–2 or C1–3 fusion and occipitocervical fusion were performed in 14 and 6 patients, respectively. The past medical history, operation time, estimated blood loss (EBL), duration of Halo vest immobilization, postoperative follow-up period, and intra- and perioperative complications were examined.

Results

The operation time was 257.9±55.6 minutes, and the EBL was 101.6±77.9 mL. Complications related to the operation occurred in 6 patients (30.0%). They included 1 major complication (5.0%): hydrocephalus at 3 months postoperatively, possibly related to an intraoperative dural tear. Other surgery-related complications included 3 cases of superficial infections, 1 case of bone graft donor site deep infection, 1 case of C2 pedicle fracture, 1 case of Halo ring dislocation, 1 case of pseudoarthrosis that required revision surgery, and 1 case of temporary neurological deficit after Halo removal at 2 months postoperatively. Complications unrelated to the operation included 2 cases of respiratory infections and 1 case of implant loosening due to a fall at 9 months postoperatively.

Conclusion

The complication rate of upper cervical fusion in patients with Down syndrome remained high; however, major complications decreased substantially. Improved intra- and perioperative management facilitates successful surgical intervention for upper cervical instability in pediatric patients with Down syndrome.

Is Initial Posterior Atlantoaxial Fixation and Fusion Applying Bilateral C1-2 Transarticular Screws and C1 Laminar Hooks Reliable for Acute Pediatric Atlantoaxial Instability?: A Minimal 10-Year Analysis of Outcome and Radiological Evaluation

STUDY DESIGN

A retrospective case series study with at least 10 years of follow-up data.

OBJECTIVE

To validate the reliability of bilateral C1-2 transarticular screws and C1 laminar hooks and a bone autograft for acute pediatric atlantoaxial instability.

SUMMARY OF BACKGROUND DATA

The reliability of initial posterior atlantoaxial fusion in pediatric patients is still controversial. To date, however, only a few published articles with short-term follow-up data are available to help spinal surgeons understand the effects of posterior atlantoaxial fusion in the skeletally immature spine.

METHODS

Five pediatric patients with acute atlantoaxial instability underwent atlantoaxial fusion using the above technique over a 3-year period. During a minimum 10-year follow-up period, not only outcomes and complications were investigated, but the vertical growth of the constructed spine in relation to the growth of the entire cervical spine, overall cervical spinal alignment, and adjacent-segment instability were evaluated.

RESULTS

The clinical follow-up indicated solid fusion and complete clinical relief from symptoms. No neural or vascular impairment was observed. The radiological evaluation showed that all patients had growth within the fusion construct reaching a mean 35.4% of the entire cervical spine. There were no radiological indicators of subaxial instability, even when cervical sagittal alignments became straight with a mean C2-7 angle of 6.4°.

CONCLUSION

The results showed that initial posterior atlantoaxial fusion accomplished with bilateral C1-2 transarticular screws, C1 laminar hooks fixation, and bony autograft is a reliable surgical technique for treating acute pediatric atlantoaxial instability without negative effects on vertical growth at the fused level or the stability of the subaxial spine.

LEVEL OF EVIDENCE

3.

Craniovertebral junction fixation in children less than 5 years

PURPOSE

Whilst rigid fixation for craniovertebral instability is the gold standard, in very young, small children conventional management may have to be modified. We present a single-centre experience of craniocervical fixation in children under 5 years.

METHODS

A retrospective review of cases that had undergone atlantoaxial (AA) or occipitocervical (OC) fixation aged under 5 years. Fusion was assessed using computerised tomography or flexion extension X-rays.

RESULTS

Twenty-six children (median age 2.3, range 0.8-4.9 years, 19 under the age of 3) underwent OC (n = 19) or AA (n = 7) fusion between 1999 and 2016. Pathology comprised 17 congenital, five trauma, two tumour and two post-infection cases. Twenty-one patients underwent sublaminar cable fixation with calvarial, autologous bone graft and halo-body orthosis immobilisation. An occipital plate and rods to sublaminar wire construct were used in four cases. A rigid instrumented fixation with occipital plate and C2 pedicle screws was utilised in one case. Follow-up was for a median of 2.8 years (range 0.03-16.3 years). Initial fusion rate was 91%, reaching 100% following two re-operations. Ninety-two per cent of patients were neurologically stable or improved following surgery. Twenty-one patients had a good overall outcome. Two patients had post-operative neurological deteriorations, and four died due to non-procedure related causes. Pin site morbidity secondary to halo use occurred in five cases.

CONCLUSION

High fusion rates with good outcomes are achievable using semi-rigid fixation in the under 5-year-olds. Full thickness, autologous calvarial bone graft secured with wire cables and halo external orthosis offers a safe and effective alternative technique when traditional screw instrumentation is not feasible. These slides can be retrieved under Electronic Supplementary Material.

C1-C2 Pedicle Screw Fixation for Pediatric Atlantoaxial Dislocation: Initial Results and Long-term Follow-up

BACKGROUND

There are few studies reporting the use of atlantoaxial pedicle screws and the long-term effects of C1-C2 posterior fusion in children. Our study is to investigate the initial results of C1-C2 pedicle screw fixation for pediatric atlantoaxial dislocation (AAD) and assessed spontaneous change of postoperative radiography after a long-term follow-up period.

METHODS

Posterior pedicle screw fixations were performed in 21 pediatric patients with AAD. All the patients underwent implant removal 1 year after their initial surgery and had regular follow-up with an average duration of 76.4 months (range, 52 to 117 mo). Clinical and radiographic data were then collected and compared.

RESULTS

Frankel Grade was significantly improved at 3 months follow-up compared with pretreatment values. All patients had good bony fusion at a mean of 4.2±0.9 months (range, 3 to 6 mo) after treatment. None of the patients experienced worsening neurological symptoms or injury to the vertebral artery. However, 2 cases experienced minor complications. Following removal of the implants, no spinal deformities or subaxial instabilities were found. The mean angle of sagittal curvature increased from 12.1±2.4 degrees (range, 0 to 22 degrees) immediately postoperatively to 19.1±2.7 degrees (range, 6 to 31 degrees) at the final follow-up (P>0.05).

CONCLUSIONS

The results demonstrated that C1-C2 pedicle screw fixation could achieve satisfactory initial results for the management of the pediatric AAD. Moreover, removal of the metal implant after bony fusion did not increase the risk of spinal deformity or subaxial instability at long-term follow-up.

A Dual Approach for the Management of Complex Craniovertebral Junction Abnormalities: Endoscopic Endonasal Odontoidectomy and Posterior Decompression with Fusion

BACKGROUND

Ventral brainstem compression secondary to complex craniovertebral junction abnormality is an infrequent cause of neurologic deterioration in pediatric patients. However, in cases of symptomatic, irreducible ventral compression, 360° decompression of the brainstem supported by posterior stabilization may provide the best opportunity for improvement in symptoms. More recently, the endoscopic endonasal corridor has been proposed as an alternative method of odontoidectomy associated with less morbidity. We report the largest single case series of pediatric patients using this dual-intervention surgical technique. The purpose of this study was to evaluate the surgical outcomes of pediatric patients who underwent posterior occipitocervical decompression and instrumentation followed by endoscopic endonasal odontoidectomy performed to relieve neurologic impingement involving the ventral brainstem and craniocervical junction.

METHODS

Between January 2011 and February 2017, 7 patients underwent posterior instrumented fusion followed by endonasal endoscopic odontoidectomy at our unit. Standardized clinical and radiological parameters were assessed before and after surgery. A univariate analysis was performed to assess clinical and radiologic improvement after surgery.

RESULTS

A total of 14 operations were performed on 7 pediatric patients. One patient had Ehlers-Danlos syndrome, 1 patient had a Chiari 1 malformation, and the remaining 5 patients had Chiari 1.5 malformations. Average extubation day was postoperative day 0.9. Average day of initiation of postoperative feeds was postoperative day 1.0.

CONCLUSIONS

The combined endoscopic endonasal odontoidectomy and posterior decompression and fusion for complex craniovertebral compression is a safe and effective procedure that appears to be well tolerated in the pediatric population.

Pediatric occipitocervical fusion: long-term radiographic changes in curvature, growth, and alignment

OBJECTIVE The authors assessed the rate of vertebral growth, curvature, and alignment for multilevel constructs in the cervical spine after occipitocervical fixation (OCF) in pediatric patients and compared these results with those in published reports of growth in normal children. METHODS The authors assessed cervical spine radiographs and CT images of 18 patients who underwent occipitocervical arthrodesis. Measurements were made using postoperative and follow-up images available for 16 patients to determine cervical alignment (cervical spine alignment [CSA], C1-7 sagittal vertical axis [SVA], and C2-7 SVA) and curvature (cervical spine curvature [CSC] and C2-7 lordosis angle). Seventeen patients had postoperative and follow-up images available with which to measure vertebral body height (VBH), vertebral body width (VBW), and vertical growth percentage (VG%-that is, percentage change from postoperative to follow-up). Results for cervical spine growth were compared with normal parameters of 456 patients previously reported on in 2 studies. RESULTS Ten patients were girls and 8 were boys; their mean age was 6.7 ± 3.2 years. Constructs spanned occiput (Oc)-C2 (n = 2), Oc-C3 (n = 7), and Oc-C4 (n = 9). The mean duration of follow-up was 44.4 months (range 24-101 months). Comparison of postoperative to follow-up measures showed that the mean CSA increased by 1.8 ± 2.9 mm (p < 0.01); the mean C2-7 SVA and C1-7 SVA increased by 2.3 mm and 2.7 mm, respectively (p = 0.3); the mean CSC changed by -8.7° (p < 0.01) and the mean C2-7 lordosis angle changed by 2.6° (p = 0.5); and the cumulative mean VG% of the instrumented levels (C2-4) provided 51.5% of the total cervical growth (C2-7). The annual vertical growth rate was 4.4 mm/year. The VBW growth from C2-4 ranged from 13.9% to 16.6% (p < 0.001). The VBW of C-2 in instrumented patients appeared to be of a smaller diameter than that of normal patients, especially among those aged 5 to < 10 years and 10-15 years, with an increased diameter at the immediately inferior vertebral bodies compensating for the decreased width. No cervical deformation, malalignment, or detrimental clinical status was evident in any patient. CONCLUSIONS The craniovertebral junction and the upper cervical spine continue to present normal growth, curvature, and alignment parameters in children with OCF constructs spanning a distance as long as Oc-C4.

Pediatric occipitocervical fixation: radiographic criteria, surgical technique, and clinical outcomes based on experience of a single surgeon

OBJECTIVE If left untreated, occipitocervical (OC) instability may lead to serious neurological injury or death. Open internal fixation is often necessary to protect the neurovascular elements. This study reviews the etiologies for pediatric OC instability, analyzes the radiographic criteria for surgical intervention, discusses surgical fixation techniques, and evaluates long-term postoperative outcomes based on a single surgeon's experience. METHODS The charts of all patients < 18 years old who underwent internal OC fixation conducted by the senior author were retrospectively reviewed. Forty consecutive patients were identified for analysis. Patient demographic data, OC junction pathology, radiological diagnostic tools, surgical indications, and outcomes are reported. RESULTS The study population consisted of 20 boys and 20 girls, with a mean age of 7.3 years. Trauma (45% [n = 18]) was the most common cause of instability, followed by congenital etiologies (37.5% [n = 15]). The condyle-C1 interval had a diagnostic sensitivity of 100% for atlantooccipital dislocation. The median number of fixated segments was 5 (occiput-C4). Structural bone grafts were used in all patients. Postsurgical neurological improvement was seen in 88.2% (15/17) of patients with chronic myelopathy and in 25% (1/4) of patients with acute myelopathy. Preoperatively, 42.5% (17/40) of patients were neurologically intact and remained unchanged at last follow-up, 42.5% (17/40) had neurological improvement, 12.5% (5/40) remained unchanged, and 2.5% (1/40) deteriorated. All patients had successful fusion at 1-year follow-up. The complication rate was 7.5% (3/40), including 1 case of vertebral artery injury. CONCLUSIONS Occipitocervical fixation is safe in children and provides immediate immobilization, with excellent survival and arthrodesis rates. Of the radiographic tools evaluated, the condyle-C1 interval was the most predictive of atlantooccipital dislocation.

Allograft versus autograft for pediatric posterior cervical and occipito-cervical fusion: a systematic review of factors affecting fusion rates

OBJECT Fusion rates are high for children undergoing posterior cervical fusion (PCF) and occipito-cervical fusion (OCF). Autologous bone has been widely used as the graft material of choice, despite the risk of donor-site morbidity associated with harvesting the bone, possibly because very low fusion rates were reported with posterior allograft cervical fusions in children several decades ago. Higher overall fusion rates using allograft in adults, associated with improvements in internal fixation techniques and the availability of osteoinductive substances such as bone morphogenetic protein (BMP), have led to heightened enthusiasm for the use of bank bone during pediatric PCF. A systematic review was performed to study factors associated with successful bone fusion, including the type of bone graft used. METHODS The authors performed a comprehensive PubMed search of English-language articles pertaining to PCF and OCF in patients less than 18 years old. Of the 561 abstracts selected, 148 articles were reviewed, resulting in 60 articles that had sufficient detail to be included in the analysis. A meta-regression analysis was performed to determine if and how age, fusion technique, levels fused, fusion substrate, BMP use, postoperative bracing, and radiographic fusion criteria were related to the pooled prevalence estimates. A systematic review of the literature was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. RESULTS A total of 604 patients met the specific inclusion and exclusion criteria. The overall fusion rate was 93%, with a mean age of 9.3 years and mean follow-up of 38.7 months. A total of 539 patients had fusion with autograft (94% fusion rate) and 65 patients with allograft (80% fusion rate). Multivariate meta-regression analysis showed that higher fusion rates were associated with OCF compared with fusions that excluded the occiput (p < 0.001), with the use of autograft instead of allograft (p < 0.001), and with the use of CT to define fusion instead of plain radiography alone. The type of internal fixation, the use of BMP, patient age, and the duration of follow-up were not found to be associated with fusion rates in the multivariate analysis. CONCLUSIONS Fusion rates for PCF are high, with higher rates of fusion seen when autograft is used as the bone substrate and when the occiput is included in the fusion construct. Further study of the use of allograft as a viable alternative to autograft bone fusion is warranted because limited data are available regarding the use of allograft in combination with more rigid internal fixation techniques and osteoinductive substances, both of which may enhance fusion rates with allograft.

Long-term growth and alignment after occipitocervical and atlantoaxial fusion with rigid internal fixation in young children

OBJECT The long-term consequences of atlantoaxial (AA) and occipitocervical (OC) fusion and instrumentation in young children are unknown. Anecdotal reports have raised concerns regarding altered growth and alignment of the cervical spine after surgical intervention. The purpose of this study was to determine the long-term effects of these surgeries on the growth and alignment of the maturing spine. METHODS A multiinstitutional retrospective chart review was conducted for patients less than or equal to 6 years of age who underwent OC or AA fusion with rigid instrumentation at 9 participating centers. All patients had at least 3 years of clinical and radiographic follow-up data and radiographically confirmed fusion. Preoperative, immediate postoperative, and most recent follow-up radiographs and/or CT scans were evaluated to assess changes in spinal growth and alignment. RESULTS Forty children (9 who underwent AA fusion and 31 who underwent OC fusion) were included in the study (mean follow-up duration 56 months). The mean vertical growth over the fused levels in the AA fusion patients represented 30% of the growth of the cervical spine (range 10%-50%). Three different vertical growth patterns of the fusion construct developed among the 31 OC fusion patients during the follow-up period: 1) 16 patients had substantial growth (13%-46% of the total growth of the cervical spine); 2) 9 patients had no meaningful growth; and 3) 6 patients, most of whom presented with a distracted atlantooccipital dislocation, had a decrease in the height of the fused levels (range 7-23 mm). Regarding spinal alignment, 85% (34/40) of the patients had good alignment at follow-up, with straight or mildly lordotic cervical curvatures. In 1 AA fusion patient (11%) and 5 OC fusion patients (16%), we observed new hyperlordosis (range 43°-62°). There were no cases of new kyphosis or swan-neck deformity, evidence of subaxial instability, or unintended subaxial fusion. No preoperative predictors of these growth patterns or alignment were evident. CONCLUSIONS These results demonstrate that most young children undergoing AA and OC fusion with rigid internal fixation continue to have good cervical alignment and continued growth within the fused levels during a prolonged follow-up period. However, some variability in vertical growth and alignment exists, highlighting the need to continue close long-term follow-up.

Computed tomographic morphometric analysis of pediatric clival screw placement at the craniovertebral junction

STUDY DESIGN

A computed tomography-based morphometric measurement of the pediatric craniovertebral junction for clival screw placement.

OBJECTIVE

To identify morphometric differences of the pediatric clivus at different ages and establish guidelines for pediatric clival screw fixation.

SUMMARY OF BACKGROUND DATA

Anterior fixation of the pediatric craniovertebral junction, a viable alternative to posterior occipital-cervical fixation, requires clival screw placement. The morphology of the pediatric clivus may be associated with greater difficulty in adequate purchase because of the spheno-occipital synchondrosis (clival fissure).

METHODS

Morphometric analysis was conducted on computed tomographic scans of the craniocervical junction in 87 pediatric patients who were assigned into groups based on their ages (2-5 yr, 6-9 yr, 10-13 yr, and 14-16 yr). Measurements were made of the sagittal and axial planes to determine the clival length, widest and narrowest clival diameter, clival fissure distance, clival-cervical angle, and putative screw lengths.

RESULTS

The mean clival length, widest diameter, narrowest diameter, fissure distance, and putative screw lengths were 29.4 mm, 28. 9 mm, 17.3 mm, 21.9 mm, and 9.6 mm, respectively. These measurements were significantly different among the groups and highly correlated to age (P < 0.01). There was no significant difference in clival-cervical angle among the groups, with a mean angle of 129.2°± 6.4°. A clival screw (ø3.5 mm) was accommodated for all children older than 10 years, 89% of children aged 6 to 9 years, and 80% of children aged 2 to 5 years.

CONCLUSION

A clival screw fixation is feasible in the pediatric craniovertebral junction, particularly in children aged 10 years or older. The dimensions of the clivus were highly dependent on age. We suggest that all pediatric patients should undergo high-resolution, thin-slice computed tomography preoperatively to assess suitability for clival screw fixation.

LEVEL OF EVIDENCE

3.

Evaluation of occipitocervical neutral position using lateral radiographs

Background

Intraoperative assessment of neutral occipitocervical balance during a fusion procedure is challenging. We designed this study to introduce a more comprehensive method of evaluating the occipitocervical neutral position using lateral radiographs.

Methods

One hundred neutral lateral cervical spine radiographs interpreted as normal were studied. Cervical spine radiographs were performed using a standard technique. The occipitocervical angle, the occipitocervical distance, and the mandible cervical distance were measured by different observers.

Results

A difference analysis was performed between males and females. The mean mandible cervical distances were 11.0 and 11.2 mm in males and females, respectively. The mean occipitocervical distances were 22.0 mm (male) and 19.6 mm (female), and the occipitocervical angles were 47.2° (male) and 45.5° (female). The occipitocervical distance revealed significant differences between males and females (p <0.01). However, there were no significant differences between sexes for the occipitocervical angle or the mandible cervical distance (p >0.01).

Conclusions

This study offers reference values for the occipitocervical angle and occipitocervical distance for the estimation of the occipitocervical neutral position. The introduction of the mandible cervical distance may make the evaluation more direct and more comprehensive during surgery because of its sensitivity to changes in head position.

Occipitocervical fusion in skeletal dysplasia: a new surgical technique

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

This study describes clinical and radiological results of a new cable technique for occipitocervical fusion (OCF) in children with skeletal dysplasia (SD).

SUMMARY OF BACKGROUND DATA

Anatomical variability and poor bone quality make upper cervical surgery technically challenging in patients with SD. We present a new cable technique for OCF in children with SD when the posterior elements are not of a size or quality for other types of instrumentation.

METHODS

Retrospective review of 24 patients with SD (8 boys, 16 girls) who underwent OCF between 2001 and 2011. In this technique, cables provide compression across a bone graft that is prevented from entering the canal and the graft resists excessive lordosis. Demographic and radiographical data are presented. All patients were followed for initial outcomes of surgery, and 20 patients (83%) were followed for 2 years or more for mid- and long-term outcomes.

RESULTS

Mean age at surgery was 6.5 years and mean follow-up was 4.1 ± 2.4 years. This technique was used as a primary procedure in 20 and a revision procedure in 4 patients. Diagnoses included Morquio syndrome (6), spondyloepiphyseal dysplasia (9), spondyloepimetaphyseal dysplasia (5), metatropic dysplasia (3), and Kniest syndrome (1). Ten patients had upper cervical instability and features of cervical myelopathy, and the remaining 14 patients had instability and signal changes on magnetic resonance image. Fusion extended from occiput to C2 in 71% patients, and upper cervical decompression was needed in 92% patients. Postoperatively, all patients were immobilized in a halo vest for mean duration of 12 weeks. Fusion was achieved in all patients. Complications included halo pin-tract infections (7), junctional instability (2), and extension of fusion (4).

CONCLUSION

This new cable technique is a good alternative for OCF in patients with SD who have altered anatomy at the craniocervical junction not amenable to rigid internal fixation.

LEVEL OF EVIDENCE

4.

Upper cervical fusion in children with Morquio syndrome: intermediate to long-term results

BACKGROUND

Paraplegia or death secondary to upper cervical spine instability and spinal cord compression are known consequences of Morquio syndrome. Decompression and fusion of the upper cervical spine are indicated to treat spinal cord compression. The purpose of this study was to report the intermediate to long-term results of upper cervical spine fusion in children with Morquio syndrome.

METHODS

Twenty patients (nine female and eleven male) with Morquio syndrome who underwent upper cervical spine fusion at a mean age of sixty-three months were retrospectively analyzed with use of hospital records. Radiographic and clinical results were reported.

RESULTS

The average follow-up period was eight years and ten months. Fusion was achieved in all patients except one; this patient underwent a revision with transarticular C1-C2 screw fixation. Seven patients developed symptomatic instability below the fusion mass that required extension of fusion to lower levels at a mean of ninety-one months after the initial operation. Two patients required decompression and fusion of a site other than the upper cervical spine. Asymptomatic cervicothoracic and thoracolumbar kyphosis was prevalent among our patients. All patients were neurologically stable at the time of the latest follow-up visit.

CONCLUSIONS

Upper cervical spine fusion provides reliable fusion and a stable neural outcome in patients with Morquio syndrome. However, distal junctional instability is a major problem at long-term follow-up. Kyphotic deformity of the cervicothoracic and thoracolumbar junction may be present in a large number of patients with Morquio syndrome and evaluation for spinal stenosis at these levels should also be considered.

Clinical application of a revised screw technique via the C1 posterior arch and lateral mass in the pediatric population

OBJECTIVE

Pediatric patients with insufficient height (≤4 mm) of the C1 posterior arch may restrict atlas screw placement via the posterior arch and lateral mass (PALM). For these patients, we modified this technique, called the 'pedicle exposure technique' (PET). We aimed to analyze the clinical feasibility and safety of the PET in the pediatric population.

METHODS

Twenty pediatric patients with atlantoaxial instability (AAI) were enrolled in this study. The average C1 posterior arch was 3.1 (2.5-3.9) mm on CT scan. All patients underwent the C1 PET and C2 pedicle screw fixation. The imaging was performed to evaluate the accuracy of screw placement and bony fusion.

RESULTS

Forty screws were inserted via C1 PALM using the PET. Venous plexus bleeding occurred in 1 patient and the internal wall of the C1 lateral mass was perforated in 1 patient. There were no perioperative neurological deficits or vertebral artery injury. Follow-up was performed in all 20 cases over a period ranging from 6 to 80 months. Bony union was seen within 3-6 months. At the final follow-up visit, 14 patients had experienced an improvement, while 6 had complete resolution of their neck pain. Myelopathy symptoms were improved in 9 patients with spinal compression.

CONCLUSION

The PET is an effective alternative for pediatric AAI when the height of the C1 posterior arch is <4 mm. Because of the higher screw entry point through the C1 posterior arch, there is effective biomechanical stability and less irritation of the venous plexus and C2 nerve root.

In vivo analysis of cervical range of motion after revised C1-C2 pedicle screw technique for pediatric atlantoaxial instability

OBJECTIVE

The purpose of this study was to analyze the cervical range of motion (ROM) after revised C1-C2 pedicle screw fixation for pediatric patients with atlantoaxial instability.

METHODS

17 pediatric patients (age range 5-14 years; mean 8.3 years) underwent the revised C1-C2 pedicle screw technique. Pre- and postoperative cervical ROM during flexion/extension, rotation and lateral bending were measured using a head-mounted motion goniometer. Plain radiographs, CT scans and MRI were performed to assess spinal cord compression, the accuracy of screw placement, and bone fusion. The American Spinal Injury Association classification was used to evaluate neurological function.

RESULTS

Revised atlantoaxial pedicle screw fixation was successfully performed in all 17 pediatric patients. There were no perioperative complications. All cases showed evidence of bone fusion 6 months after surgery by CT scan. During the follow-up period (24-92 months), of 6 patients with preoperative myelopathy, 3 improved from grade D to grade E and 3 from grade C to grade D. The final follow-up cervical ROM was significantly greater than the preoperative and 6-month postoperative ROM. There was a statistically significant difference between preoperative and 6-month postoperative ROM for flexion, extension, and left and right axial rotation movements.

CONCLUSION

As a short-segmental fixation technique, revised C1-C2 pedicle screw fixation can provide effective biomechanical stability. Final follow-up cervical ROM is significantly increased through alleviating cervical pain and symptoms of myelopathy after surgery and possible subaxial compensation.

Os odontoideum: case report

OBJECTIVE: To report the difficulties in managing a case of os odontoideum. METHODS: Female patient, 12 years old who developed a quadiparesis after minor cervical trauma in October 2005. In the emergency department a congenital cervical anomaly was identified. The patient was placed in a Stryker® frame and, few days later, in a halo bracing. After 3 months, an infection around the pins emerged and the halo vest had to be removed. A severe C1-2 instability persisted and a C1-C2 Gallie procedure was attempted. In the following weeks the bone disappeared and another procedure was attempted in June 2006 - C1 laminectomy and occiput-C3 fusion. In the following months the neurological status of the patient improved and a complete mass of occiput-C3 fusion was observed. RESULTS: We choose a posterior cervical arthrodesis of C1-C2 using the Gallie technique. Since the condition was not resolved we performed a second surgery, C1 laminectomy (determined by SAC of 8, 3 mm in MRI) followed by posterior occiput-C3 fusion. In our case, until now, there is no evidence of axial decompensation, but a more prolonged follow-up is needed. CONCLUSIONS: The treatment of os odontoideum has many considerations but the essential that in the presence of instability and neurological deficit a solid fusion is achieved. In case of failure of posterior atlantoaxial wiring, the occiput-C2 or C3 fusion with rods seems to be an excellent option with a high rate of success, avoiding the need for additional support.

Outcomes of instrumented fusion in the pediatric cervical spine

Object

The most common cause of cervical spine arthrodesis in the pediatric population is instability related to congenital or traumatic pathology. Instrumenting the cervical spine can be challenging given smaller anatomical structures, less ossified bone, and future growth potential and development. Studies in adult patients have suggested that using screw constructs results in improved outcomes with lower rates of instrumentation failure. However, the pediatric literature is limited to small retrospective series. Based on a review of the literature and their own patient series, the authors report that instrumenting the pediatric cervical spine with screw constructs may be safer and more effective than using wiring techniques.

Methods

The authors reviewed the existing pediatric cervical spine arthrodesis literature and contributed 31 of their own cases from September 1, 2007, to January 1, 2011. They reviewed 204 abstracts from January 1, 1966, to December 31, 2010, and 80 manuscripts with 883 total patients were included in the review. They recorded demographic, radiographic, and outcomes data—as well as surgical details—with a focus on fusion rates and complications.

Patients were then grouped into categories based upon the procedure performed: 1) patients who underwent fusions bridging the occipitocervical junction and 2) patients who underwent fusion of the cervical spine that did not include the occiput, thus including atlantoaxial and subaxial fusions. Patients were further subdivided according to the type of instrumentation used—some had posterior cervical fusion with wiring (with or without rod implantation); others had posterior cervical fusion with screws.

Results

The entire series comprised 914 patients with a mean age of 8.30 years. Congenital abnormalities were encountered most often (in 55% of cases), and patients had a mean follow-up of 32.5 months. From the entire cohort, 242 patients (26%) experienced postsurgical complications, and 50 patients (5%) had multiple complications. The overall fusion rate was 94.4%.

For occipitocervical fusions (N = 285), both screw and wiring groups had very high fusion rates (99% and 95%, respectively, p = 0.08). However, wiring was associated with a higher complication rate. From a sample of 252 patients, 14% of those treated with screw instrumentation had complications, compared with 50% of patients treated with wiring (p < 0.05).

In cervical fusions not involving the occipitocervical junction (N = 181), screw constructs had a 99% fusion rate, whereas wire instrumentation only had an 83% fusion rate (p < 0.05). Similarly, patients who underwent screw fixation had a lower complication profile (15%) when compared with those treated with wiring constructs (54%, p < 0.05).

Conclusions

The results of this study are limited by variations in construct design, use of orthoses, follow-up duration, and newer adjuvant products promoting fusions. However, a literature review and the authors' own series of pediatric cases suggest that instrumentation of the cervical spine in children may be safer and more efficacious using screw constructs rather than wiring techniques.

Complications and outcomes of posterior fusion in children with atlantoaxial instability

INTRODUCTION

Atlantoaxial instability (AAI) is an uncommon disease in children. Surgical treatment of pediatric patients with AAI poses a challenge to spine surgeons because of the patients' immature bone quality, extensive anatomical variability, and smaller osseous structures. In this study, the authors report complications and outcomes after posterior fusion in children with AAI.

METHODS

The authors reviewed medical records of patients 13 years old and younger with AAI who underwent posterior fusion in the Nagoya Spine Group hospitals, a multicenter cooperative study group, from January 1995 to December 2007. We identified 11 patients who underwent posterior fusion, and analyzed their clinical outcomes and complications. To determine if vertical growth within the construct continued after posterior fusion, in three patients at 5 or more years following occipito-cervical (O-C) fusion, intervertebral disc heights and vertebral heights between the fused and non-fused levels were compared on the final follow-up.

RESULTS

The initial surgeries were C1-C2 fusions in six patients and O-C fusion in five patients. Successful fusion ultimately occurred in all patients, however, the complication rate related to the operations was high (64%). Complications included neurologic deterioration, pedicle fracture with pedicle screw insertion, C1 posterior arch fracture with lateral mass screw insertion, perforation of the skull with a head pin placement, and fusion extension to adjacent vertebrae. Two patients required reoperation. The mean fixed and non-fixed intervertebral disc heights on the final follow-up were 2.6 and 5.3 mm, respectively, showing that the disc height of the fixed level was less than the non-fused level. Each vertebra lengthened similarly between fused and non-fused levels except for C2 which had a lower growth rate than the other vertebrae.

CONCLUSIONS

A high complication rate should be anticipated after posterior fusion in children with AAI. Careful consideration should be paid to pediatric patients with AAI treated by screw and/or rod systems. After posterior fusion in pediatric patients, each vertebra continued to grow, in contrast the disc height decreased between fused levels.

Pediatric bony craniovertebral junction abnormalities: Institutional experience of 10 years

Objective:

To study the clinical features and treatment outcome of pediatric patients with bony craniovertebral abnormalities.

Materials and Methods:

The authors studied 189 consecutive cases of pediatric bony craniovertebral junction abnormalities operated between 2001 and March, 2010.

Results:

The pathologies were developmental (n = 162), traumatic (n = 18) and tuberculous (n = 9). Surgical procedures included transoral decompression (n = 118), occipitocervical fusion (OCF, n = 139), C 1 -C 2 fusion (n = 45), and posterior fossa decompression (n = 5). Methods for OCF included contoured stainless steel rods (n = 86), titanium lateral mass screws and plates (n = 47) and steel wires (n = 6). Constructs of all patients of posterior fixation with contoured rods and wires or lateral mass screw and rod who could be followed up were either stable/fused or were fused and stable. No implant failure was noticed among these two surgical procedures. However, 6 patients with C 1-C 2 fusion had broken wires on follow-up requiring repeat posterior fixation. Good neurological outcome was observed even in poor-grade patients. No significant effect on the curvature or growth of the spine was observed at follow-up.

Conclusions:

Pediatric craniovertebral junction anomalies can be managed successfully with good outcomes using a low cost contoured rod and wires.

Posterior instrumentation for occipitocervical fusion

Since 1995, 29 consecutive patients with craniocervical spine instability due to several pathologies were managed with posterior occipitocervical instrumentation and fusion. Laminectomy was additionally performed in nineteen patients. The patients were divided in two groups: Group A which included patients managed with screw-rod instrumentation, and Group B which included patients managed with hook-and-screw-rod instrumentation. The patients were evaluated clinically and radiographically using the following parameters: spine anatomy and reconstruction, sagittal profile, neurologic status, functional level, pain relief, complications and status of arthrodesis. The follow-up was performed immediately postoperatively and at 2, 6, 12 months after surgery, and thereafter once a year. Fusion was achieved in all but one patient. One case of infection was the only surgery related complication. Neurological improvement and considerable pain relief occurred in the majority of patients postoperatively. There were neither intraoperative complications nor surgery related deaths. However, the overall death rate was 37.5% in group A, and 7.7% in group B. There were no instrument related failures. The reduction level was acceptable and was maintained until the latest follow-up in all of the patients. No statistical difference between the outcomes of screw-rod and hook-and-screw-rod instrumentation was detected. Laminectomy did not influence the outcome in either group. Screw-rod and hook-and-screw-rod occipitocervical fusion instrumentations are both considered as safe and effective methods of treatment of craniocervical instability.

A 6-year experience of 100 cases of pediatric bony craniovertebral junction abnormalities: treatment and outcomes

The authors studied 100 consecutive cases of pediatric bony craniovertebral junction abnormalities operated between 2001 and 2006. The pathologies were developmental (n = 86), traumatic (n = 10) and tuberculous (n = 4). Surgical procedures included transoral decompression (n = 59), occipitocervical fusion (OCF, n = 69), C(1)-C(2) fusion (n = 22), occiput-C(2) wiring (n = 5), and posterior fossa decompression (n = 5). Implants for OCF included contoured stainless steel rods (n = 47), titanium lateral mass screws and plates (n = 16) and steel wires (n = 5). Adequate bone fusion was observed in all patients with OCF at a mean follow-up of 16.5 months, irrespective of the type of implant used for posterior fixation. Good neurological outcome was observed even in poor-grade patients. No significant effect on the curvature or growth of the spine was observed at follow-up.

Biomechanical evaluation of an atlantoaxial lateral mass fusion cage with C1-C2 pedicle fixation

STUDY DESIGN

A biomechanical testing protocol was used to evaluate atlantoaxial fixation techniques in a human cadaveric model.

OBJECTIVE

To compare in vitro biomechanics of atlantoaxial lateral mass fusion cage combined with C1-C2 pedicle screw technique with those of C1-C2 pedicle screw technique alone and C1-C2 transarticular screws combined with Gallie wires.

SUMMARY OF BACKGROUND DATA

An atlantoaxial lateral mass fusion cage was designed, knowing that the cage, when rigidly combined with C1-C2 pedicle screws, could offer other fusion spots for atlantoaxial stabilization in cases when the posterior arch of the atlas is absent or removed for decompression and a Gallie fixation is impossible. No comparative in vitro biomechanical test has been conducted previously to evaluate the feasibility of this method.

METHODS

Anatomic measurements of the atlantoaxial lateral masses were taken using computed tomography in normal human subjects. Six fresh-frozen human cadaveric cervical spines (C0-C4) were used in the biomechanical study. Specimens were tested in their intact condition, after destabilization via transverse-alar-apical ligament disruption, and after implantation of 3 fixation constructs: (1) transarticular screws combined with Gallie wires, (2) C1-C2 pedicle screws, and (3) atlantoaxial lateral mass fusion cage combined with C1-C2 pedicle screws. Pure moment loading up to 1.5 Nm in flexion/extension, right-left lateral bending, and right-left axial rotation was applied to the occiput, and relative intervertebral rotations were determined using stereophotogrammetry. Range of motion for the intact, destabilized, and 3 fixation scenarios were determined.

RESULTS

The anatomic data indicated that feasible cage design were in 3 sizes: 11/8, 12/9, and 13/10 mm for length/width, and 3.5, 4, and 4.5 mm for height. The biomechanical data indicated that transverse-alar-apical ligament disruption significantly increased C1-C2 motion for all directions. All the 3 fixation techniques significantly reduced motion compared with the intact and destabilized cases. There were no statistically significant differences among the 3 fixation techniques.

CONCLUSION

The biomechanical study indicated that, contrary to expectation, addition of a cage did not increase the stability compared with C1-C2 pedicle screw alone. However, the C1 + C2 + Cage technique may be a viable alternative for atlantoaxial stabilization when the posterior arch of the atlas is absent or removed for decompression and a Gallie fixation is impossible.

Changes in cervical spine curvature in pediatric patients following occipitocervical fusion

OBJECTIVE

The study aims to assess changes in cervical spine curvature following occipitocervical fusion (OCF) in the pediatric population.

METHODS

In a retrospective study, the angle of sagittal curvature and whole cervical spine alignment were determined in the preoperative, immediate postoperative, and follow-up radiographs in 14 patients (<20 years of age) who underwent OCF for developmental atlantoaxial instability between 1995 and 2006. At follow-up, the mean angle of sagittal curvature showed a statistically significant increase from 22+/-10.1 degrees immediately following surgery to 35.9+/-18 degrees at follow-up (p = 0.001). Six patients had exaggerated lordosis (defined as >10 degrees increase in the angle of sagittal curvature). The sagittal curvature angle did not show any worsening in seven patients following removal of the implant.

CONCLUSIONS

OCF in the pediatric population can result in an increase in the lordotic curvature of the cervical spine that might stabilize following removal of the metal implant within a year of surgery.

The lasso technique for posterior C1-C2 fusion

OBJECTIVE

Posterior atlantoaxial arthrodesis requires placement of a bone graft in a properly prepared environment that includes decorticated bony surfaces, compressive forces between graft and native bone, and limited motion. To achieve posterior atlantoaxial arthrodesis, various cable-and-graft constructs have been used, all of which require an intact posterior arch of C1. For patients who lack an intact arch owing to congenital, iatrogenic, or traumatic causes, we have devised the "lasso technique," which uses the remnants of the posterior arch of C1 for placement of the graft to achieve fusion isolated to C1-C2 or to be part of an occipitocervical construct.

METHODS

A retrospective record review was conducted of all patients who underwent the lasso technique. Clinical and radiographic history, perioperative course, and time to fusion were recorded. We describe the technique in detail.

RESULTS

During the last 13 years, we have used this technique successfully in five female and four male patients. The absent or incompetent posterior arch was a congenital defect in one patient, a result of prior surgical removal in four patients, and caused by fracture associated with prior failed fusion attempts in four other patients. All patients experienced successful fusion after an average of 6.8 months.

CONCLUSION

Securing a bone graft in the absence of an intact C1 lamina is a challenge when a patient presents with atlantoaxial instability. We have devised the lasso technique to secure an interpositional C1-C2 graft using the remnants of the posterior atlantal arch. Although this technique has been required relatively infrequently, we have found it to be valuable and effective in our practice.

Selection of a rigid internal fixation construct for stabilization at the craniovertebral junction in pediatric patients

OBJECT

Atlantoaxial and occipitocervical instability in children have traditionally been treated with posterior bone and wire fusion and external halo orthoses. Recently, successful outcomes have been achieved using rigid internal fixation, particularly C1-2 transarticular screws. The authors describe flow diagrams created to help clinicians determine which method of internal fixation to use in complex anatomical circumstances when bilateral transarticular screw placement is not possible.

METHODS

The records of children who underwent either atlantoaxial or occipitocervical fixation with rigid internal fixation over an 11-year period were retrospectively reviewed to define flow diagrams used to determine treatment protocols.

RESULTS

Among the 95 patients identified who underwent atlantoaxial or occipitocervical fixation, the craniocervical anatomy in 25 patients (six atlantoaxial and 19 occipitocervical fixations [26%]) required alternative methods of internal fixation. Types of screw fixation included loop or rod constructs anchored by combinations of C1-2 transarticular screws (15 constructs), C-1 lateral mass screws (11), C-2 pars screws (24), C-2 translaminar screws (one), and subaxial lateral mass screws (six). The mean age of the patients (15 boys and 10 girls) was 9.8 years (range 1.3-17 years). All 22 patients with greater than 3-month follow-up duration achieved solid bone fusion and maintained stable constructs on radiographic studies. Clinical improvement was seen in all patients who had preoperative symptoms.

CONCLUSIONS

Novel flow diagrams are suggested to help guide selection of rigid internal fixation constructs when performing pediatric C1-2 and occipitocervical stabilizations. Use of these flow diagrams has led to successful fusion in 25 pediatric patients with difficult anatomy requiring less common constructs.

Augmentation of occipitocervical contoured rod fixation with C1-C2 transarticular screws

BACKGROUND CONTEXT

The technique of occipitocervical fusion using a threaded contoured rod attached with sublaminar wires to the occiput and upper cervical vertebrae is widely used throughout the world and has been clinically proven to provide effective fixation of the destabilized spine. However, this system has some disadvantages in maintaining stability, especially at C1-C2 because of the large amount of axial rotation at this level. In some clinical situations such as fracture of the C1 lamina, C1 laminectomy, and excessively lordotic curvature, it is not always possible to wire C1 directly into the construct. In such cases, combination of other stabilization methods that include C1 indirectly can be used to achieve a reliable posterior internal fixation.

PURPOSE

Primarily, to evaluate whether a contoured rod construct in which C1 is indirectly included using C1-C2 transarticular screws is biomechanically equivalent to a standard, fully wired contoured rod construct. Secondarily, to evaluate the biomechanical benefit of adding C1-C2 transarticular screws to a fully wired contoured rod construct.

STUDY DESIGN

Repeated-measures nondestructive in vitro biomechanical testing of destabilized cadaveric human occipitocervical spine specimens.

METHODS

Six human cadaveric specimens from the occiput to C3 were studied. Angular and linear displacement data were recorded while nonconstraining nondestructive loads were applied. Three methods of fixation were tested: contoured rod incorporating C1 with and without transarticular screws and contoured rod with transarticular screws without incorporating C1.

RESULTS

All three constructs reduced motion to well within normal range. In contoured rod constructs with C1 wired, addition of transarticular screws slightly but significantly improved stability. In constructs with transarticular screws, incorporation of C1 into the contoured rod wiring did not improve stability significantly.

CONCLUSIONS

Adding C1-C2 transarticular screws to a wired contoured rod construct where C1 is included only slightly improves stability. As the absolute reduction in motion from adding transarticular screws is small (<1 degree), it is doubtful whether any enhanced fusion from this additional procedure outweighs the surgical risks. However, transarticular screws provide an effective alternate method to fixate C1 when the posterior arch of C1 is absent or has been fractured.

Change in lordosis at the occipitocervical junction following posterior occipitocervical fusion in skeletally immature children

STUDY DESIGN

Retrospective case series.

OBJECTIVE

Evaluate the change in lordosis at the occipitocervical junction occurring during growth in skeletally immature children treated with posterior occipitocervical arthrodesis versus patients skeletally mature at arthrodesis.

SUMMARY OF BACKGROUND DATA

Posterior occipitocervical arthrodesis is often indicated for children who have instability of the upper cervical spine develop. Theoretically, in skeletally immature children, this approach retards the growth of the posterior spinal elements but allows the anterior spinal column to continue to grow with the risk of excessive lordosis of the cervical spine developing.

METHODS

There were 21 children, younger than 11 years (range 1.9-10.9) at surgery and expected to have normal spinal growth, followed radiographically for an average of 6.3 years (range 2.0-12.4). Postoperative lateral neutral radiographs were compared to those at most recent follow-up to measure the change in occipitocervical angle. These results were then compared to a series of control patients who were skeletally mature at surgery.

RESULTS

Average overall change in lordosis at the occipitocervical junction was -4.6 degrees (range -12.8 degrees to +6.5 degrees). Average annualized change was -0.28 degrees per vertebral level per year (range -1.13 degrees to +0.67 degrees). This annualized change in angle was statistically significant compared to the average change of +0.01 degrees (range -0.09 degrees to +0.11 degrees) measured in the control series of patients skeletally mature at surgery (P = 0.01).

CONCLUSIONS

Increasing lordosis occurs at the occipitocervical junction following fusion in skeletally immature children. If occipitocervical arthrodesis is indicated in a skeletally immature child, fusion in excessive extension and overtightening of posterior wires should be avoided.

Long-term maintenance of cervical alignment after occipitocervical and atlantoaxial screw fixation in young children

OBJECT

Despite decades of surgical experience, the long-term consequences of occipitocervical (OC) and atlantoaxial (C1-2) fusions in children are unknown. The purpose of this study was to determine the long-term effects of these fusions on growth and alignment of the maturing cervical spine.

METHODS

A retrospective chart review was conducted for patients 6 years of age or younger (mean 4.7 years, range 1.7-6.8 years) who underwent OC or C1-2 fusion at the Primary Children's Medical Center at the University of Utah within the last 10 years. Immediate postoperative plain radiographs and computed tomography (CT) scans were compared with the most recent plain and dynamic radiographs to assess changes in spinal growth and alignment. Seventeen children met entry criteria for the study. All patients had fusion documented on follow-up radiography or CT scans. At a mean follow up of 28 months, there were no cases of sagittal malalignment (kyphotic or swan-neck deformity), subaxial instability (osteophyte formation or subluxation), or unintended fusion of adjacent levels. The lordotic curvature of the cervical spine increased from a mean of 15 degrees postoperatively to 27 degrees at follow up (p = 0.06). A mean of 34% of the vertical growth of the cervical spine occurred within the fusion segment. When data were analyzed pertaining to a subgroup of five patients who underwent follow-up periods for longer than 48 months (mean 50.2 months, range 48-54 months), similar results were seen.

CONCLUSIONS

Preliminary follow-up results indicate that, compared with older children, children 6 years of age or younger undergoing OC or C1-2 fusion are not at an increased risk of spinal deformity or subaxial instability. Longer follow-up periods, during which measurements of the spinal canal are taken, will be necessary to determine precisely how children's spines grow and remodel after an upper cervical spine fusion.

Radiographic assessment of segmental motion at the atlantoaxial junction in the Klippel-Feil patient

STUDY DESIGN

A retrospective review of 33 consecutive Klippel-Feil syndrome (KFS) patients at a single institution.

OBJECTIVES

To assess in KFS patients the presence and degree of radiographic segmental motion at the atlantoaxial junction, factors contributing to such motion, and associated clinical manifestations.

SUMMARY OF BACKGROUND DATA

Studies suggest that abnormal segmentation in KFS patients may result in cervical hypermobility, increasing the risk of developing neurologic compromise and the need for surgical intervention. The use of the anterior and posterior atlantodens interval (AADI/PADI) has gained interest as a method for assessing atlantoaxial instability and for space available for the cord. Although helpful for identifying instability after trauma, these measurements are not understood in KFS patients. In addition, the effects of the fusion process associated with KFS on atlantoaxial motion and associated clinical findings have not been properly addressed.

METHODS

Radiographs were analyzed for the presence of occipitalization, number/location of congenitally fused segments, and the AADI and PADI.

RESULTS

There were 15 males and 18 females (mean age, 13.9 years). Occipitalization occurred in 48.5% of patients. A fused C2-C3 segment was noted in 72.7% of cases. More motion with respect to AADI was evident on O-C1 and C2-C3 fusion only patients, which were all asymptomatic. Overall, 24.2% of patients were symptomatic. Mean AADI and PADI difference was 2.0 mm (symptomatic: mean, 1.5 mm; asymptomatic: mean, 2.1 mm) and -1.7 mm (symptomatic: mean, -1.0 mm; asymptomatic: mean, -2.0 mm), respectively (P > 0.05).

CONCLUSIONS

Hypermobility of the atlantoaxial junction, as indicated by increased AADI on flexion-extension radiographs, is not necessarily associated with an increased risk for the development of symptoms or neurologic signs in the KFS patient. Occipitalization plays an integral role in the degree of motion at the atlantoaxial region. Greatest AADI values were in patients with occipitalization and a fused C2-C3 segment. The presence of symptoms was not related to the degree of AADI change. Evaluation of the PADI provides additional information for identifying patients at risk for developing symptoms. Nonetheless, KFS patients remain largely asymptomatic.

Occipitocervical reconstruction with the Ohio Medical Instruments Loop: results of a multicenter evaluation in 30 cases

OBJECT

Stabilization of the craniocervical junction (CCJ) remains a significant challenge. In this multicenter study, the authors present the results of an evaluation of a precontoured titanium implant, the Ohio Medical Instruments (OMI) Loop, for craniocervical fixation.

METHODS

In this multicenter retrospective study the authors evaluated 30 patients (16 female, 14 male; mean age 53.8 years) with rheumatoid arthritis (15 cases), traumatic occipitoatlantoaxial instability (six cases), congenital vertebral anomalies (two cases), instability due to basilar invagination in the setting of Chiari malformation (two cases), or Down syndrome (one case), tumor (one case), os odontoideum (two cases), and pseudarthrosis/other (one case), who underwent OMI Loop-assisted occipitocervical reconstruction. The mean follow-up period was 25.4 months (range 6-60 months). A solid reconstruction was achieved in 29 of 30 cases; there was only one case of hardware failure requiring reoperation. Noncritical hardware failure occurred in two patients in whom partial occipital screw backout occurred but did not necessitate reoperation. There were no perioperative neurological complications. One patient (3.3%) experienced a delayed postoperative worsening of myelopathy at 1 year that resolved with further surgery. Postoperatively, in 66.6% of patients the degree of myelopathy remained stable (as measured by American Spinal Injury Association [ASIA] scores), whereas 30% improved by one or more ASIA grade. The rate of osseous fusion was 96.6% at a mean follow-up period of 25.4 months.

CONCLUSIONS

The authors found that the OMI Loop is a versatile precontoured occipitocervical fixation device that can be applied to a wide range of CCJ lesions. It provides excellent immediate rigid fixation of the CCJ, a high rate of osseous fusion, and a low rate of hardware failure.

C1-C2 posterior fusion in growing patients: long-term follow-up

STUDY DESIGN

A retrospective review of patients undergoing C1-C2 posterior fusion during childhood was undertaken.

OBJECTIVES

The aim of this study was to investigate the change in the sagittal curvature of the cervical spine in children after C1-C2 posterior fusion.

SUMMARY OF BACKGROUND DATA

There have been only a few reports on postoperative changes in the sagittal curvature of the cervical spine after C1-C2 posterior fusion in children. However, they have all described the onset of sagittal postoperative cervical deformities.

METHODS

Between January 1977 and December 1992, a total of 12 children underwent C1-C2 posterior fusion for atlantoaxial instability resulting from congenital malformation in eight, juvenile rheumatoid arthritis in one, and rotatory subluxation in three. The average age at the time of surgery was 10.9 years (range 7-12 years). All children underwent a similar treatment program with gradual preoperative reduction in halo cast, followed by C1-C2 posterior fusion with Mersilene loops in two cases, wiring in eight (Gallie's or Brooks' techniques), and interlaminar clamps in the remaining two. The halo cast made it possible to avoid a hyperextended or hyperflexed C1-C2 position while performing the atlantoaxial fusion, thus ensuring a more anatomic position during C1-C2 fusion. In the postoperative period, the halo cast was maintained for 7 to 9 weeks. RESULTS Follow-up ranged from 7 years to 13 years. Preoperative alignment of the cervical spine was classified into two groups: lordosis (eight patients) and straight (four patients). Postoperative subaxial malalignment (kyphosis) occurred in four cases (33%): these patients showed evidence of spontaneous and gradual sagittal improvement and presented either a straight (two cases) or a lordotic (two cases) cervical spine at follow-up. Immediately after surgery, the cervical spine was normally aligned in the remaining eight patients (lordosis and straight alignment in six and two cases, respectively) and was unchanged at follow-up. At follow-up, none of the 12 patients had a cervical deformity on sagittal plane.

CONCLUSION

In children, a spontaneous realignment of the subaxial kyphosis observed after C1-C2 posterior fusion can be noted at follow-up, when a postoperative deformity occurs (33% in the present series). According to the present findings, it is not always mandatory to perform occipitocervical fusion in children with atlantoaxial instability just to prevent subaxial deformity in the cervical spine.

Atlantooccipital dislocation in children: presentation, diagnosis, and management

Atlantooccipital dislocation (AOD) injuries are highly unstable, and usually result in significant neurological injury and death. Recently the postinjury survival period has increased. In a review of the literature the authors found 41 cases in which survival was greater than 48 hours. This is likely due to improved on-scene resuscitation, spinal immobilization, transportation, new diagnostic techniques, and a higher index of suspicion.

Diagnosis is usually made with plain cervical radiographs, but there are shortcomings associated with this modality in the pediatric population. Diagnosis is aided by high-resolution computerized tomography and magnetic resonance imaging. Infants and toddlers may undergo orthotic immobilization alone, whereas older children usually undergo early occipital cervical fusion. Those with incomplete AOD may be managed successfully with orthotic immobilization.