Intended and non-intended kinematic effects of atlanto-axial rotational high-velocity, low-amplitude techniques.

INTRODUCTION: The study of neck kinematics during high-velocity, low-amplitude manipulations of the atlanto-axial segment is essential to understanding cervical motion mechanisms and their impact and possible risk for soft-tissue injuries during treatment of spine disorders. METHODS: Twenty fresh-frozen specimens were tested during manual application of an axial rotation technique. FINDINGS: The kinematics indicate the thrust induced motion components of approximately 1° at the treated segment around all three axes of the local embedded reference frame. Moreover, an equal amount of axial rotation motion took place at the adjacent atlanto-occipital joint. INTERPRETATION: Overall atlanto-axial motion remained below the level of slow regional mobilization of the cervical spine. These findings can be correlated to literature data concerning the limited increase in vertebral artery strain during high-velocity, low-amplitude manipulation.

Effect of Atlas Vertebrae Realignment in Subjects with Migraine: An Observational Pilot Study.

Introduction. In a migraine case study, headache symptoms significantly decreased with an accompanying increase in intracranial compliance index following atlas vertebrae realignment. This observational pilot study followed eleven neurologist diagnosed migraine subjects to determine if the case findings were repeatable at baseline, week four, and week eight, following a National Upper Cervical Chiropractic Association intervention. Secondary outcomes consisted of migraine-specific quality of life measures. Methods. After examination by a neurologist, volunteers signed consent forms and completed baseline migraine-specific outcomes. Presence of atlas misalignment allowed study inclusion, permitting baseline MRI data collection. Chiropractic care continued for eight weeks. Postintervention reimaging occurred at week four and week eight concomitant with migraine-specific outcomes measurement. Results. Five of eleven subjects exhibited an increase in the primary outcome, intracranial compliance; however, mean overall change showed no statistical significance. End of study mean changes in migraine-specific outcome assessments, the secondary outcome, revealed clinically significant improvement in symptoms with a decrease in headache days. Discussion. The lack of robust increase in compliance may be understood by the logarithmic and dynamic nature of intracranial hemodynamic and hydrodynamic flow, allowing individual components comprising compliance to change while overall it did not. Study results suggest that the atlas realignment intervention may be associated with a reduction in migraine frequency and marked improvement in quality of life yielding significant reduction in headache-related disability as observed in this cohort. Future study with controls is necessary, however, to confirm these findings. Clinicaltrials.gov registration number is NCT01980927.

Plough fracture of the anterior arch of the atlas: a biomechanical investigation.

PURPOSE: "Plough" fracture, in which the odontoid ploughs through and causes a high-energy shear fracture of the anterior arch of the atlas, has been documented in clinical case studies and classified as clinically unstable. Our objectives were to develop a biomechanical model to simulate atlantal plough fracture and investigate injury mechanisms. METHODS: Horizontally aligned head impacts into a padded barrier were simulated using a human upper cervical spine specimen (occiput through C3) mounted to a surrogate torso mass on a sled and carrying a surrogate head. We divided 13 specimens into 3 groups based upon head-impact location: upper forehead in the midline, upper lateral side of the forehead, and upper lateral side of the head. Post-impact fluoroscopy and anatomical dissection documented the injuries. Time-history biomechanical responses were determined for neck loads, accelerations, and motions. RESULTS: A single specimen sustained a plough fracture variant to the atlantal anterior arch due to impact to the upper forehead and continued forward torso momentum. Horizontal velocity of C3 at the time of forehead impact was 2.7 m/s. This specimen had an anteriorly displaced fracture fragment consisting of the inferior portion of the atlantal anterior arch together with multiple complete fractures of the axis. Peak force occurred first at the impact barrier (1,903.0 N; 47 ms) followed by the neck (1,715.9 N; 58 ms). Forward translation ended at 48 ms for the head and 72 ms for the C3 vertebra. CONCLUSIONS: Our present results, though preliminary, indicate that plough fracture of the anterior arch of the atlas likely occurred immediately following or simultaneously with associated axis fractures at approximately 58 ms following impact to the upper forehead. The present injury response data highlighted the role of load transfer from torso momentum to the upper cervical spine to produce anterior shear force and forward displacement of the dens and bony fragment of the anterior arch of the atlas relative to the C1 ring.

[Scoliotic spine deformity in children and adolescents associated with the craniovertebral junction pathology].

This literature review is devoted to the clinical and pathogenic aspects of the relationship between Chiari type I malformation (CMT) and scoliosis. The view of the clinical presentation development in CMT associated with scoliosis is considered on the basis of both the CSF dynamics disturbances and vascular pathology of the craniovertebral junction. The role of the posterior atlanto-occipital membrane is evaluated. Case reports of the risk factors for scoliosis progression in patients with CMT are presented.

Prescriptive proprioceptive insoles and dental orthotics change the frontal plane position of the atlas (C1), mastoid, malar, temporal, and sphenoid bones: a preliminary study.

The purpose of this series of case studies was to determine if the frontal plane position of the cranial bones and atlas could be altered using dental orthotics, prescriptive insoles, or both concurrently. The cranial radiographs of four patients were reviewed for the study. Three of the patients were diagnosed as having a temporomandibular joint (TMJ) dysfunction and a preclinical clubfoot deformity. The fourth patient was diagnosed as having a TMJ dysfunction, a preclinical clubfoot deformity and a Catetgory II sacral occipital subluxation, as designated in the chiropractic's Sacro Occipital Technique (SOT). Each patient had a series of four cranial radiographs taken using a modified orthogonal protocol. In two patients, improvement towards orthogonal was achieved when using both prescriptive dental orthotics and prescriptive insoles concurrently. Improvement towards orthogonal was less apparent when using only the prescriptive dental orthotic. No improvement or a negative frontal plane shift was noted when using only the prescriptive proprioceptive insoles. In the third patient, the frontal plane position of the cranial bones and atlas increased (away from orthogonal) when using the generic proprioceptive insoles alone or in combination with a prescriptive dental orthotic. In the fourth patient, the frontal plane position of the cranial bones improved using the dental orthotic. However, the proprioceptive insoles, when used alone or in combination with the dental orthotic, increased the frontal plane position of the cranial bones and atlas. This study demonstrates that changes in the frontal plane position of the cranial and atlas bones can occur when using proprioceptive insoles and/or dental orthotics.

Neurologic findings of craniovertebral junction disease.

In this review, we explain the origins of central cord syndrome and Bell's cruciate paralysis and the intricate detail of neural pathways located in this region and their influence on motor and sensory function. Although lesion studies and tract tracing studies on primates over the past 50 years refute the theory of a somatotopically organized corticospinal tract, this concept continues to pervade many neuroanatomic texts. We categorized the various pathologies of the craniovertebral junction and their unique neurologic presentations. New developments in the fields of neuroscience of spinal tract lesioning are also discussed.

Atlas fractures.

OBJECTIVE: To provide a comprehensive review of the biomechanics, pathophysiology, and clinical management of atlas fractures. METHODS: Selected literature review. RESULTS: Atlas fractures account for 25% of craniocervical injuries, 3% to 13% of cervical spine injuries, and 1% to 3% of all spinal injuries. Motor vehicle accidents account for 80% to 85% of atlas fractures, and the mechanism of injury is axial loading. Isolated atlas fractures are more common; however, 40% to 44% of atlas fractures have concomitant axis fractures. Fractures of isolated anterior or posterior arches are more common and typically seen with concomitant spine fractures. Isolated burst fractures are the second most common type and rarely cause neurological injury. Treatment of atlas fractures is based on whether they occur in isolation or in combination with other cervical spine injuries and on the integrity of the transverse ligament, which is best assessed with high-resolution magnetic resonance imaging. Isolated atlas fractures without injury of the transverse ligament or associated with bony avulsion of the transverse ligament can be treated with halo-brace immobilization and should be followed for instability with flexion-extension radiography. Surgical fixation is recommended for nonbony avulsion of the transverse ligament or if instability is present. The type of surgical fixation is determined by the concomitant craniocervical injuries if present. CONCLUSION: Atlas fractures can be treated with halo-brace immobilization with acceptable outcomes. The role of surgical fixation, especially for atlas burst fractures, requires further study for clarification.

Biomechanical assessment of bilateral C1 laminar hook and C1-2 transarticular screws and bone graft for atlantoaxial instability.

UNLABELLED: STUDYDESIGN: In vitro biomechanical test was conducted to compare the stability of 5 different atlantoaxial posterior fusion techniques. OBJECTIVE: To evaluate the biomechanical stability of an atlas laminar hook combined with transarticular (TA) screws relative to 4 different conventional fusion techniques. SUMMARY OF BACKGROUND DATA: The atlantoaxial instability caused by fractures, rheumatoid arthritis, congenital deformity, or traumatic lesions of the transverse ligament often result in acute or chronic spinal cord compression, a possible threat to a patient's life. Posterior atlantoaxial fixations are used to reconstruct the stability of atlantoaxial articulation. Conventional posterior atlantoaxial fixations are associated with high rates of pseudoarthrosis and carry the potential risk of neurologic complication. TA screw fixation can provide an excellent biomechanical stability. As a modified 3-point fixation technique, the bilateral C1-2 TA screws have been combined with C1 laminar hook and bone grafts. This modified technique had carried good clinical outcomes. METHODS: Eight human specimens (C0-C4) were loaded nondestructively with pure moments and the range of motion at the level of C1-C2 was measured. Eight specimens were implanted with each of the following techniques, respectively: Gallie fixation, C1-2 TA screw fixation combined with Gallie fixation, C1-2 TA screw fixation, C1 laminar hook combined with C1-2 TA screw fixation plus bone grafts, and the C1 lateral mass screws in the atlas combined with C2 isthmic screws in axis. RESULTS: Although the C1-2 TA screws best restricted lateral bending and axial rotation, the modified 3-point fixation technique additionally restricted flexion-extension and provided the excellent stability. Differences in axial rotation and lateral bending (with + or - 1.5 Nm load) were observed when the 3-point fixation techniques (TA + Gallie and TA + hook) were compared with atlas lateral mass screws in the atlas combined with isthmic screws in axis. CONCLUSIONS: The modified C1 laminar hook combined with C1-2 TA screws and bone graft fixation provided the best biomechanical stability. The C1 lateral mass screws in the atlas combined with isthmic screws in axis fixation is a sound alternative when the C1-2 TA screw fixation is not feasible.

Traumatic spondylolisthesis of the axis: a biomechanical comparison of clinically relevant anterior and posterior fusion techniques.

OBJECT: Surgical management of unstable traumatic spondylolisthesis of the axis includes both posterior and anterior fusion methods. The authors performed a biomechanical study to evaluate the relative stability of anterior fixation at C2-3 and posterior fixation of C-1 through C-3 in hangman's fractures. METHODS: Fresh-frozen cadaveric spine specimens (occipital level to T-2) were subjected to stepwise destabilization of the C1-2 complex, replicating a Type II hangman's fracture. Intact specimens, fractured specimens, and fractured specimens with either anterior screw and plate or posterior screw and rod fixation were each tested for stability. Each spine was subjected to separate right and left rotation, bending, flexion, and extension testing. RESULTS: Anterior fixation restored stiffness in flexion and extension movements to values greater than those for intact specimens. For other movement parameters, the values approximated those for intact specimens. Posterior fixation increased the stiffness to above those values seen for anterior fixation specimens. CONCLUSIONS: In cadaveric spine specimens subjected to a Type II hangman's fracture, both anterior fixation at C2-3 and posterior fixation with C-1 lateral mass screws and C-2 and C-3 pedicle screws resulted in a consistent increase in stiffness, and hence in stability, over intact specimens.

Evaluation of occipitocervical subluxation in rheumatoid arthritis patients, using coronal-view reconstructive computed tomography.

STUDY DESIGN: Reconstructive computed tomography (CT) study of occipito-atlanto and atlantoaxial joints in RA patients. SUMMARY OF BACKGROUND DATA: The occipitocervical region is one of the most common sites of rheumatoid arthritis (RA). Although lateral radiography has been used for the diagnosis of atlantoaxial subluxation and vertical subluxation, reconstructive CT imaging of the occipito-atlanto and atlantoaxial joints is more sensitive in detecting morphologic changes in this region. We investigated this region in RA patients, using coronal-view reconstructive CT images, and examined the relationship between the morphology and other radiographic parameters. METHODS: The occipitocervical region was examined in 58 female RA patients by reconstructive CT, plain radiography, and MRI. The degree of destructive change on reconstructive CT was compared to that on other radiographic evaluations. RESULTS: Coronal-view reconstructive CT revealed primary destructive changes before detection by lateral radiography, using Redlund-Johnell or Ranawat values. A Redlund-Johnell value less than 34 mm was diagnostic for occipitocervical subluxation in female RA patients. CONCLUSION: Coronal-view reconstructive CT is useful for the diagnosis of occipitocervical joint subluxation in RA.

Sleep apnea in rheumatoid arthritis patients with occipitocervical lesions: the prevalence and associated radiographic features.

Since sleep apnea is a risk factor for high mortality of rheumatoid arthritis (RA) patients, this study examined the prevalence in RA patients with occipitocervical lesions, and the associated radiographic features. Twenty-nine RA patients requiring surgery for progressive myelopathy due to occipitocervical lesions (3 males, 26 females, average age 65 years) were preoperatively evaluated. Twenty-three (79%) had sleep apnea defined as apnea-hypopnea index >5 events per hour measured by a portable monitoring device, and all of them were classified as the obstructive type. Among gender, age, bone mass index (BMI), and radiographic parameters related to occipitocervical lesions: atlantodental interval (ADI), cervical angles (O/C1, C1/2, and C2/6), and cervical lengths (O-C2 and O-C6), the ADI and cervical lengths were shown to be significantly associated with the presence of sleep apnea by parametric statistical analysis. Since there were positive correlations between the ADI and cervical lengths by Pearson's test, we performed a multivariate logistic regression analysis after adjustment for confounding factors and found that small ADI was the principle parameter associated with sleep apnea. We therefore conclude that the prevalence of sleep apnea is higher than that in a general RA population that was reported previously, and believe that occipitocervical lesions are an independent risk factor for this condition. Small ADI and short neck, secondary to the vertical translocation by RA, may cause obstructive sleep apnea, probably through mechanical or neurological collapse of the upper airway.

C1 arch regeneration, tight cisterna magna, and cervical syringomyelia following foramen magnum surgery.

BACKGROUND: Although bone regrowth following craniocervical decompression has been rarely reported to cause late recurrence of Chiari symptoms, syringomyelia has not been observed in such cases. We report a unique case of cervical syringomyelia resulting from spontaneous regeneration of the posterior C1 arch after foramen magnum decompression. CASE DESCRIPTION: A 38-year-old male patient underwent resection of a symptomatic foramen magnum meningioma. Three years later, he developed neuropathic pain in his left upper extremity with worsening dysphagia and dysphonia. MRI revealed regeneration of the posterior arch of C1 with tight tonsillar impaction of the foramen magnum and extensive cervical syringomyelia. Surgical exploration was undertaken. Neo-ossification of the posterior arch of C1 and thick arachnoid adhesions were found to obstruct cerebrospinal fluid flow through the foramen of Magendie. Foramen magnum decompression, arachnoid dissection, and duraplasty were thus performed and cerebrospinal fluid flow was reestablished through the foramen of Magendie. Postoperatively, patient's symptoms improved dramatically and repeat MRI showed complete resolution of the syrinx cavity. CONCLUSION: Spontaneous bone regrowth and arachnoid scarring may lead to the development of cervical syringomyelia several years after foramen magnum surgery. Neurosurgeons should be aware of this rare complication whose management is similar to that of Chiari malformations, namely craniocervical decompression and establishment of a patent foramen of Magendie.

Biomechanical analysis of atlas fractures: a study on 40 human atlas specimens.

STUDY DESIGN: Forty isolated specimens of the first cervical vertebra were tested by the application of pure axial force to failure. To exclude ligamentous side effects, transverse ligaments were dissected in all specimens. OBJECTIVE: To investigate the biomechanical characteristics of the human atlas and to describe the influence of different speeds of force impact on the fracture types. SUMMARY OF BACKGROUND DATA: Atlas fractures have been reproduced in some studies in the literature. However, the characteristics of isolated atlas fractures under pure axial loading at different speeds has not been reported so far. METHODS: After dissection of soft tissue and generation of a peripheral quantitative computed tomography scan, the atlas preparations were tested to failure by displacement-controlled axial force application at constant speeds of either 0.5 mm/s (Group 1) or 300 mm/s (Group 2). The fracture types were classified according to Gehweiler. RESULTS: At slow loading speed (Group 1), 2 Type-I (anterior arch), 3 Type-II (posterior arch), 2 Type-III (anterior and posterior arch), and 13 Type-IV (lateral mass) fractures occurred out of 20 specimens. At high loading speed (Group 2), Type-III fractures (burst fractures of 2 to 4 parts) occurred in all 20 tested specimens. CONCLUSION: The presented results strongly suggest that the Type of atlas fracture depends on the speed of axial force impact. The present study demonstrates that Type-III fractures (2- to 4-part burst fractures) result from fast force impact whereas slow force impact is responsible for Type-IV atlas fractures of the lateral mass.

Spontaneous rotatory atlantoaxial dislocation without neurological compromise in a child with Down syndrome: a case report.

Spontaneous atlantoaxial dislocation is a rare recognised complication of Down syndrome. In the majority of cases, dislocation takes place in an anteroposterior direction and is often associated with abnormalities of odontoid development or ossification. Rotatory atlantoaxial dislocation is extremely rare in Down syndrome and this is to our knowledge the first reported case in which modern imaging methods have been described; surface shaded reformats derived from a multislice CT scan were of fundamental importance in making the diagnosis.

Case report: nonoperative treatment of an unstable Jefferson fracture using a cervical collar.

The treatment of unstable burst fractures of the atlas (Jefferson fractures) is controversial. Unstable Jefferson fractures have been managed successfully with either immobilization, typically halo traction or halo vest, or surgery. We report a patient with an unstable Jefferson fracture treated nonoperatively with a cervical collar, frequent clinical examinations, and flexion-extension radiographs. Twelve months after treatment, the patient achieved painless union of his fracture. The successful treatment confirms prior studies reporting unstable Jefferson fractures have been treated nonoperatively. The outcome challenges the clinical relevance of treatment algorithms that rely on the "rules of Spence" to guide treatment of unstable Jefferson fractures and illustrates instability may not necessarily be present in patients with considerable lateral mass widening. Additionally, it emphasizes a more reliable way of assessing C1-C2 stability in unstable Jefferson fractures is by measuring the presence and extent of anterior subluxation on lateral flexion and extension views.

Screw fixation via diploic bone paralleling to occiput table: anatomical analysis of a new technique and report of 11 cases.

Several types of posterior approaches have been adopted for occipitocervical fusion. Prior to this study, Foerater et al. in 1927 used a fibular strut graft in the site between the occiput and the lower cervical spine to achieve fusion. Since then, various techniques including wrings, Hartshill loop, AO reconstructive plate, and AXIS occipital plate were described and used widely. As far as we know, all these techniques involve the screw placement vertical to the diploic bone; however none has ever addressed the feasibility of screw placement in occiput parallelling to the diploic bone. In our study, 30 dry specimens of human occiputs were measured manually using vernier calipers and protractors. The intradiploic screw was first supposed to be inserted inferiorly to the superior nuchal line (SNL) prominence. The entry point located at the superior edge of the SNL prominence. Afterward, the measurements of extracranial occiput in SNL area on midline and bilateral 15 mm to the midline saggital-cutting planes of the occiput were conducted. The thickness of the occipital bone at the location of SNL prominence, the entry point, the exit point and the screw orientation were measured, respectively. Afterward, 11 patients with craniocervical malformation were treated surgically using this alternative and their X-ray radiographs and CT scans were evaluated postoperatively. The data showed that the occipital at the site of SNL prominence was the thickest. The thickest point was external occipital protuberance (EOP), which was up to 14 mm. The thickness decreased gradually from the site of SNL to the superior border of surgical decompressed area. The actual length of screw channel was about 26 mm. The mean thickness for safe screw insertion ranged from 5.73 to 14.14 mm. A total of 22 intraocciput screws parallel to diploic bone were placed precisely, without injury to the cerebral and inner occipital venous sinus. The results confirm that occiput is available for holding intraocciput screw paralleling to diploic bone.

A detailed morphologic and functional magnetic resonance imaging study of the craniocervical junction in adolescent idiopathic scoliosis.

STUDY DESIGN: Conventional and phase-contrast magnetic resonance (MR) imaging were used to evaluate the morphology and cerebrospinal fluid (CSF) flow dynamics at craniocervical junction in adolescent idiopathic scoliosis (AIS). OBJECTIVES: To determine the morphology of cerebellar tonsil, foramen magnum, and dynamic flow of CSF at the craniocervical junction in AIS patients versus normal controls and their correlation with somatosensory cortical evoked potentials (SSEP). SUMMARY OF BACKGROUND DATA: Previous studies have documented obstructed CSF flow in patients with Chiari I malformation. Low-lying cerebellar tonsils and syringomyelia are also observed in AIS patients. We sought to investigate whether disturbed CSF flow is also evident in AIS subjects at the foramen magnum level and its association with level of cerebellar tonsils and dimensions of foramen magnum. METHODS: Conventional and phase-contrast MR were performed in 105 adolescent girls (69 AIS subjects and 36 age-matched controls). Measurements of cerebellar tonsillar level related to the basion-opsithion (BO) line, anteroposterior (AP), transverse (TS) diameter, and area of foramen magnum, and peak velocity of CSF flow in both the anterior and posterior subarachnoid space through foramen magnum were obtained. Correlations were made among different parameters and SSEP findings. RESULTS: A total of 42% of subjects in the AIS group had the cerebellar tonsillar tip positioned 1 mm below the BO line. The cerebellar tonsillar level in AIS subjects was significantly lower than the median tonsillar level in normal controls (P < 0.01). The AP diameter and area of foramen magnum were significantly larger in AIS subjects when compared with normal controls (P < 0.05), but the peak CSF velocities through foramen magnum showed no significant difference (P > 0.05). CONCLUSION: Peak CSF velocities through foramen magnum were not significantly different in AIS subjects despite the presence of low-lying cerebellar tonsils. This might be explained by the compensatory effect of larger foramen magnum in AIS subjects.