Radiologic Evaluation of Basilar Invagination Without Obvious Atlantoaxial Instability (Group B Basilar Invagination): Analysis Based on a Study of 75 Patients

Anatomical Implications of Chiari I and Basilar Invagination (Type B) in the IV Ventricle and Cisterna Magna

OBJECTIVE

To analyze the anatomical changes of the IV ventricle and cisterna magna in the Chiari malformation I (CMI) and basilar invagination (type B).

METHODS

This is a controlled study with 161 exams of magnetic resonance imaging (MRI) of adults grouped into control (n = 37), basilar invagination (BI; n = 31), Chiari malformation I (CMI; n = 37), and CMI+BI (n = 56). The MRIs were analyzed using the visualization software Osirix (Pixmeo, Bernex, Geneva, version 3.8.2). The morphometric variables were: distance from the obex to the McRae line; length of the IV ventricle floor; and the area and volume of the cisterna magna. The univariate ANOVA followed by Tukey's post-hoc test was applied to evaluate the difference between the groups. The difference between sexes was evaluated by the t test for each group.

RESULTS

Alterations in the cisterna magna and IV ventricle were more evident only in the CMI and CMI+BI groups. For both sexes, the CMI and CMI+BI groups showed: a reduction in the CSF space (P < 0.001), cisterna magna with volume reduction (P < 0.001), low position of the obex (P < 0.001), and IV ventricle more elongated (male P = 0.007 and female P < 0.001). The BI group had no significant change in the analysis by sex.

CONCLUSIONS

The CMI (isolated and associated with BI) showed a low obex position and elongation of the IV ventricle due to traction towards the spinal canal. The reduction of cisterna magna volume added to the occupation of the cerebellar tonsils can impact in the cerebrospinal fluid dynamics. The BI when isolated was not related to alterations in the parameters of cerebrospinal fluid spaces studied.

Chamberlain's Line Violation in Basilar Invagination Patients Compared with Normal Subjects: A Systematic Literature Review and Meta-Analysis

OBJECTIVE

To compare the measured odontoid tip violation above Chamberlain's line described in the literature to diagnose basilar invagination (BI) and to establish the normal placement of the dens tip defining individuals without BI (normal subjects).

METHODS

A systematic literature review was performed to identify clinical or radiological studies that expressed the amount of odontoid violation above Chamberlain's line in patients with a BI diagnosis. In addition, a meta-analysis was performed to evaluate normal subjects' values of Chamberlain's line violation (CLV).

RESULTS

There were 23 studies included (13 radiological and 10 clinical). Most studies used computed tomography and/or magnetic resonance imaging. Eight different cutoff values were used to measure dislocated odontoid apexes above Chamberlain's line regardless of the radiological modality. The mean measured amount of CLV was 3.95 mm (median 5 mm; range, 0-9 mm). The meta-analysis included 8 studies (1233 patients) with a normal sample population with a mean normal CLV of -0.63 mm (below the line) (95% confidence interval [-0.8, 1.18 mm], random effects model).

CONCLUSIONS

Different values were found in the assessed studies used for CLV in BI diagnosis. This variability is especially important for type B BI, as type A BI has other craniocervical diagnostic parameters. Considering the results obtained in this meta-analysis, BI should be diagnosed in the case of any dens violation >1.18 mm.

Evolving Concepts of Craniovertebral and Spinal Instability

Weakness of the muscles of the nape of the neck and back of the spine and its related instability is the nodal point of pathogenesis of a number of clinical and pathological events at the craniovertebral junction and the spine. Whilst acute instability results in sudden and relatively severe symptoms, chronic or long-standing instability is associated with a range of musculoskeletal and structural spinal alterations. Telescoping of the spinal segments results in "vertical" spinal instability in the subaxial spine and central or axial atlantoaxial instability (CAAD) at the craniovertebral junction. Instability in such cases might not be observed on dynamic radiological imaging. Chiari formation, basilar invagination, syringomyelia, and Klippel-Feil alteration are some of the secondary alterations as a result of chronic atlantoaxial instability. Radiculopathy/myelopathy related to spinal degeneration or ossification of posterior longitudinal ligament appears to have their origin from vertical spinal instability. All the secondary alterations in the craniovertebral junction and subaxial spine that are traditionally considered pathological and to have compressive and deforming role are essentially protective in nature, are indicative of instability, and are potentially reversible following atlantoaxial stabilization. Stabilization of unstable spinal segments is the basis of surgical treatment.

Central Atlantoaxial Dislocation: Presenting Symptoms, Diagnostic Parameters, and Surgical Treatment from Reports on 15 Surgically Treated Patients

AIM

This chapter reviews the clinical entity of central or axial atlantoaxial instability (CAAD).

MATERIAL AND METHODS

From January 2018 to November 2020, 15 patients were identified as having CAAD, wherein there was no atlantoaxial instability when analyzed by conventional radiological parameters and wherein there was no evidence of neural or dural compression due to the odontoid process. The patients were identified as having atlantoaxial instability on the basis of the alignment of facets on lateral profile imaging and a range of telltale clinical and radiological indicators. The clinical statuses of the patients were recorded both before and after surgical treatment by using the specially designed Goel symptom severity index and visual analog scale (VAS) scores. All patients were treated via atlantoaxial fixation.

RESULTS

There were six men and nine women ranging in age from 18 to 45 years (average: 37 years). The presenting clinical symptoms were relatively subtle and long-standing. Apart from symptoms that are generally related to neural compromise at the craniovertebral junction, a range of nonspecific cranial and spinal symptoms were prominent. The follow-up time after surgery ranged from 6 to 34 months. All patients showed early postoperative and sustained clinical recovery.

CONCLUSIONS

The correct diagnosis and appropriate surgical treatment of CAAD can provide an opportunity for quick and lasting clinical recovery.

Basilar invagination without atlantoaxial dislocation: treatment by correction of clivus canal angle with interfacet distraction and fixation

BACKGROUND

This study reports on the surgical technique used and clinical outcomes obtained during the treatment of basilar invagination (BI) without atlantoaxial dislocation (AAD) through the correction of the clivus canal angle (CCA) using interfacet distraction and fixation.

METHODS

Nineteen cases with BI without AAD treated by the correction of the clivus canal angle were retrospectively analyzed. Pre- and postoperative computed tomography scans and three-dimensional reconstruction views were obtained to measure the size of the CCA, pB-C2 distance, and degree of BI. Chiari malformation and syringomyelia were evaluated by magnetic resonance imaging (MRI). The clinical outcomes for all patients were measured using the Japanese Orthopedic Association (JOA) scale. The CCA was corrected by using interfacet distraction and fixation techniques. The Wilcoxon test was used to compare pre- and postoperative measurements.

RESULTS

All the patients were followed up for 24.95 ± 5.22 months (range 12-36 months); no patient suffered intraoperative nerve or vascular injury. Clinical symptoms improved in 17 patients (89.5%). The mean JOA score increased from 12.32 ± 1.89 to 14.37 ± 1.30 (Z = -3.655, P < 0.001). The mean CCA improved from 129.34 ± 8.52° preoperatively to 139.75 ± 8.86° postoperatively (Z = -3.824, P < 0.001). The mean pB-C2 decreased from 7.47 ± 2.21 to 5.68 ± 3.13 (Z = -3.060, P = 0.002). Syringomyelia was significantly reduced in 10 out of 13 patients by the first follow-up year. All patients achieved bony fusion.

CONCLUSION

Posterior interfacet distraction and fixation to correct the CCA is a feasible and effective method for treating BI without AAD.

Rotatory atlantoaxial dislocation presenting as spinal kyphoscoliosis

A 16-year-old male presented with primary complaint of worsening dorsal spinal kyphoscoliosis (SKS) for 3 years. More recently, he developed spasticity in legs, breathlessness on mild exertion, and sleep apneas. Apart from SKS, investigations revealed rotatory atlantoaxial dislocation. Atlantoaxial fixation resulted in rapid recovery from all symptoms including from spinal deformity. Observations in this patient suggest that rotatory dislocation can be a cause of spinal deformity.

Radiological approach to basilar invagination type B: Reliability and accuracy

OBJECTIVES

This study aims to determine the reliability of the radiological tests used in the diagnosis of basilar invagination (BI).

METHODS

Patients diagnosed with type B basilar invagination, who had both magnetic resonance (MR) and computed tomography (CT) imaging between January 2014 and November 2019 were included in this retrospective reliability study. In this study, distance from odontoid apex to Chamberlain's line (OA-CL) was accepted as a reference method for the diagnosis. Forty-two BI cases and 79 controls were included. Three radiologists with different levels of experience individually evaluated OA-CL, Boogard's angle (BoA), clivo-axial angle (CXA), clivo-dens angle (CDA), and clivo-palate angle (CPA) on midsagittal CT and MR images. Statistical analysis was made with the intraclass correlation coefficient (ICC), t-test, and receiver operating characteristic (ROC) curve.

RESULTS

The ICC for CT and MR were; 0.977-0.973 (OA-CL), 0.912-0.882 (BoA), 0.845-0.846 (CXA), 0.862-0.864 (CDA), and 0.762-0.747 (CPA) respectively (P < 0.001). The areas under the ROC curve were 0.977 (BoA), 0.832 (CXA), 0.852 (CDA), and 0.719 (CPA) (P < 0.001). The cut-off measures were ≥137.84° (BoA), ≤149.25° (CXA), ≤129.58° (CDA), and ≤61.83° (CPA). The diagnostic accuracies were 0.954 (BoA), 0.664 (CXA), 0.704 (CDA), 0.438 (CPA) (P < 0.001).

CONCLUSIONS

OA-CL and BoA express excellent inter-rater agreement than CXA, CDA, and CPA, which are limited due to morphological variations and head spatial position. BoA is the second most reliable diagnostic test. CXA, CDA, should only be used for complementary information. CPA was found inadequate for the diagnosis of BI..

Atlantoaxial fixation for failed foramen magnum decompression in patients with Chiari formation

Background:

Relationship of atlantoaxial instability with Chiari formation is further analyzed in the report.

Objective:

The outcome of 25 patients who had failed conventional treatment for Chiari formation that included foramen magnum decompression surgery and were treated by atlantoaxial fixation is analyzed.

Materials and Methods:

During the period January 2010 to November 2019, we treated 25 patients who had undergone conventionally described surgical procedures; all included foramen magnum decompression for Chiari formation. None of the patients had any craniovertebral junction anomaly. All patients had syringomyelia. All patients had worsened in their neurological condition following surgery either in the immediate or in the delayed postoperative phase. Atlantoaxial instability was diagnosed on the basis of facetal alignment and on the basis of direct observation of joint status by bone manipulation during surgery. The patients were treated by atlantoaxial fixation. Goel clinical grading scale and Japanese Orthopedic Association Score assessed the clinical status both before and after surgery.

Results:

Following surgery, all patients improved in the clinical condition. The improvement began in the immediate postoperative period and progressed. During the follow-up period that ranged from 4 to 123 months, “significant” neurological recovery and amelioration of presenting symptoms were observed. During the period of follow-up, reduction in the size of syrinx was observed in 14 out of 18 cases where postoperative magnetic resonance imaging was possible.

Conclusions:

Clinical results reinforce the belief that atlantoaxial instability is the nodal point of pathogenesis of Chiari formation. Atlantoaxial fixation is the treatment.

Alternative technique of C1-2-3 stabilization-sectioning of muscles attached to C2 spinous process and C2-3 fixation

Aim:

An alternative technique of C1-2-3 fixation is described that blocks the critical anteroposterior odontoid process movements and retains rotatory movement at the atlantoaxial joint. The technique involves sharp section of the muscles attached to the C2 spinous process and C2-3 transarticular interfacetal screw fixation.

Materials and Methods:

We successfully used this technique of fixation in 14 cases wherein in similar case situation; we earlier advocated inclusion of C1 in the fixation construct. Eleven patients had multisegmental spinal degeneration, 1 patient had Hirayama disease, and 2 patients had ossified posterior longitudinal ligament.

Results and Technical Advantages:

The procedure avoids manipulating C1 vertebra and excludes it from the fixation process, disables movement of C2 vertebra but retains rotation movements of the atlantoaxial joint that are executed by the muscles attached to the transverse process of atlas. The net effect is that the anteroposterior odontoid process movements that threaten the cervicomedullary neural structures are blocked and the critical rotatory atlantoaxial movements are retained.

Conclusions:

The discussed technique can be useful for cases undergoing multisegmental fixation that includes atlantoaxial joint.

Chiari 1 Formation Redefined-Clinical and Radiographic Observations in 388 Surgically Treated Patients

OBJECTIVE

The subject of Chiari formation is revisited and redefined. Results of surgical treatment of patients with Chiari formation by atlantoaxial fixation are presented.

METHODS

Results were analyzed of 388 patients with Chiari formation surgically treated during 2010 to June 2019.

RESULTS

Two hundred and sixty-six patients had syringomyelia. Two hundred and three patients had no craniovertebral bone abnormality and 74 patients had group A and 111 patients had group B basilar invagination. Twenty-nine patients had been earlier treated by foramen magnum decompression surgery with or without duroplasty. Clinical parameters, analysis of video recordings both before and after surgery, and patient self-assessment were included in the analysis of outcome. Immediate postoperative and sustained clinical improvement was observed in 385 patients (99.4%).

CONCLUSIONS

Satisfactory clinical outcome in most patients after atlantoaxial fixation and without any manipulation of neural structures, dura, or bone in the region of foramen magnum consolidates the viewpoint that atlantoaxial instability is the nodal point of pathogenesis of Chiari 1 formation. The study suggests that Chiari 1 formation may be a secondary natural neural alteration in the face of atlantoaxial instability. The role of foramen magnum decompression surgery needs to be reassessed.

External syringomyelia in longstanding benign foramen magnum tumors

BACKGROUND

The effect of benign foramen magnum tumours on cranial and spinal dimensions and cerebrospinal fluid (CSF) spaces is unclear. In this study, we measured alterations in cerebrospinal fluid (CSF) spaces in the spinal canal and in the posterior cranial fossa distant from the site of benign foramen magnum tumors.

METHODS

Twenty-nine magnetic resonance imaging scans of patients with foramen magnum tumors (8 meningiomas and 21 C2 neurinomas) were identified for radiological morphometric analysis and compared with normal control scans. The anterior-posterior distance between the pontomedullary junction and the clivus, the spinal canal diameter, spinal cord diameter, and cord-canal ratios were measured at the C6 and T2 levels.

RESULTS

The mean spinal canal diameter was significantly higher in tumor scans at both the C6 and T2 spinal levels than in controls (13.8 mm vs. 11.4 mm at C6; p<0.0001, and 12.9 mm vs. 11.9 mm at T2; P=0.01). Further, the mean cord:canal ratio was significantly lower in tumor scans at both levels (0.49 vs. 0.64 at C6; P<0.0001, and 0.45 vs. 0.54 at T2; P=0.0009). There was no significant difference in mean anteroposterior distance from the clivus to the pontomedullary junction (10.4 mm vs. 10.3 mm; P=0.91).

CONCLUSION

In the presence of benign foramen magnum tumors, the spinal canal diameter and CSF volume in the spinal canal increased at the C6 and T2 levels, distant from the tumor site, a phenomenon we describe as "external syringomyelia".

Is C2-3 fusion an evidence of atlantoaxial instability? An analysis based on surgical treatment of seven patients

Objective:

The authors analyze the rationale of atlantoaxial fixation in patients presenting with symptoms related to cervical myelopathy and wherein the radiological images depicted C2–3 fusion and presence of single or multiple level neural compression of the subaxial cervical spinal cord attributed to “degenerative” spine.

Materials and Methods:

Seven adult males were analyzed who presented with long-standing symptoms of progressive cervical myelopathy and where imaging showed presence of C2–3 fusion, no cord compression related to odontoid process, and evidence of single or multiple level lower cervical cord compression conventionally attributed to spinal degeneration. There was no other bone or soft tissue abnormality at the craniovertebral junction. There was no evidence of atlantoaxial instability when assessed by conventional radiological diagnostic parameters. Atlantoaxial instability was diagnosed on the basis of clinical understanding, atlantoaxial facetal malalignment, and manual assessment of instability by bone handling during surgery. All the seven patients underwent atlantoaxial fixation and no surgical manipulation at lower cervical spinal levels.

Results:

At an average follow-up of 34 months, all patients have recovered satisfactorily in their neurological function.

Conclusion:

The presence of C2–3 fusion is an indication of atlantoaxial instability and suggests the need for atlantoaxial stabilization. Effects on the subaxial spine and spinal cord are secondary events and may not be surgically addressed.

Cervicomedullary angle as an independent radiological predictor of postoperative neurological outcome in type A basilar invagination

To propose an independent radiological index to evaluate surgical outcomes of A type basilar invagination, a retrospective study was conducted to compare the clinical outcome between procedures 1 and 2 by applying intraoperative consistent traction and manual reduction. Moreover, the atlantodental interval (ADI), cervicomedullary angle (CMA), bilateral sagittal inclination of atlantoaxial joint (SIAA) were measured and compared to pre-operation. Postoperatively, only these patients undergoing procedure 2 achieved significant neurological improvement. The ADIs and the SIAAs decreased in both groups, these differences are statistically significant between pre- and post- operation. For postoperative CMAs, only these patients undergoing modified surgery gained significant improvement of angle with mean 141°. We concluded that the CMA or SIAA could be a radiological predictor to evaluate surgical outcome in BI, among which the CMA is a more independent and easily measurable predictor that is closely correlated with satisfactory neurological improvements. Moreover, procedure 2 with intraoperative resistant cranial traction and manual reduction can help us achieve a good CMA.

Hybrid and double insurance atlantoaxial facetal fixation

The authors report a case of a 19-year-old female patient having basilar invagination with complex musculoskeletal abnormalities wherein atlantoaxial fixation was done with a combination of Goel and Magerl techniques on a single articulation on one side and two transarticular screws (Magerl technique) were deployed on the contralateral side articulation. The combination of Goel and Magerl techniques used in a novel fashion resulted in strong fixation and provided an environment for bone fusion. The special joint architecture and location of facet of atlas anterior and rostral to the facet of axis in the form of facetal-spondyloptosis were used to advantage as it provided a direct screw trajectory for transarticular screw insertion. The patient recovered after surgery in her neurological function. Craniovertebral junction realignment could be observed. Solid bone fusion was observed after 8 months of the surgical procedure.

A Review of a New Clinical Entity of 'Central Atlantoaxial Instability': Expanding Horizons of Craniovertebral Junction Surgery

The author discusses the novel form of central or axial atlantoaxial instability and analyses its clinical significance. High degree of clinical and radiological understanding of the region is mandatory to diagnose and then treat such atlantoaxial instability. Evaluation of alignment of facets of atlas and axis and observations on direct manipulation of facets of atlas and axis forms the basis of diagnosis. The treatment of clinical entities like basilar invagination, Chiari formation, syringomyelia and myelopathy related to cervical spinal degeneration, spinal deformities, ossified posterior longitudinal ligament, and Hirayama disease can be influenced by the understanding of central or axial atlantoaxial instability.

Role of Subaxial Spinal and Atlantoaxial Instability in Multisegmental Cervical Spondylotic Myelopathy

AIM

In this paper the role of atlantoaxial and multilevel subaxial spinal instability as the primary nodal point of the pathogenesis of degenerative cervical spinal disease-related myelopathy, and the focus of surgical treatment for it, is evaluated.

MATERIALS AND METHODS

The series analyses the treatment of 73 patients with single or multilevel degenerative cervical spinal disease by fixation of the involved spinal segment(s) alone, aimed at arthrodesis. No bone decompression or disc/osteophyte resection was done. In 23 patients, the atlantoaxial joint was included in the spinal fixation, as atlantoaxial instability was identified by facetal malalignment on imaging or by observations on direct bone manipulation during surgery. There were 70 males and 3 females. The ages of the patients ranged from 35 to 76 years (average 57 years). The transarticular screw method was deployed for subaxial spinal fixation and a lateral mass plate/rod and screw technique was used for atlantoaxial fixation.

RESULTS

During the follow-up period, which ranged from 3 to 42 months (average 27 months), all patients improved in terms of their clinical symptoms. There were no surgery- or implant-related complications.

CONCLUSION

Atlantoaxial joint instability is frequently associated with subaxial multilevel spinal instability in degenerative spinal disease. Fixation of the spinal segments provides a safe, effective and rational treatment for single or multilevel spinal degeneration.

Cervical Fusion as a Protective Response to Craniovertebral Junction Instability: A Novel Concept

The author reviews the various types of cervical fusion that are associated with instability of the craniovertebral junction. Assimilation of the atlas, C2-3 fusion, the Klippel-Feil abnormality, and pancervical fusion are amongst the more common types of bone abnormalities. It is conceptualised that these types of cervical fusion are not related to any kind of embryological dysgenesis or fault, but instead emerge due to longstanding muscle spasms of the neck in response to atlantoaxial instability. Such bone fusions could be secondary protective responses to longstanding atlantoaxial instability.

Radiological Evaluation of Craniocervical Region in Patients with Basilar Invagination

STUDY DESIGN

A retrospective analysis of collected data.

OBJECTIVE

Our study aims to present the morphology of cranial-cervical spinal canal in basilar invagination (BI) patients.

SUMMARY OF BACKGROUND DATA

BI is characterized by protrusion of the odontoid process into the foramen magnum (C0), leading to compression of the cervicomedullary junction. However, no study has ever clarified the anatomical diameters of spinal canal in patients with BI.

METHODS

The study retrospectively examined computed tomography (CT)-based anatomical characteristics in a cohort of 84 patients with and without BI. We measured the anteroposterior diameter (APD) and transversal diameter (TVD) of spinal canal from C0 to C4, together with the area of vertebral canal (Area). Independent samples t test was used for statistical analysis.

RESULTS

The APD in the BI group was shorter than the control group from C0 to C2 (C0: 27.98 vs. 35.11 mm, P < 0.001; C1: 11.87 vs. 16.91 mm, P < 0.001; C2: 12.91 vs. 14.84 mm, P < 0.001), but it became longer from C3 to C4. The TVD of the BI group was significantly wider from C0 to C3 (C0: 30.59 vs. 28.54 mm, P < 0.001; C1: 31.31 vs. 25.98 mm, P < 0.001; C2: 21.56 vs. 20.40 mm, P = 0.01; C3: 22.45 vs. 21.23 mm, P = 0.013), and it had no significance at C4. The Area showed no difference between the two groups from C1 to C2, but it turned larger at C3 and C4 in BI patients.

CONCLUSION

BI patients may have shorter APD from C0 to C2, which could be the leading cause of neurological compression, necessitating decompression on sagittal plane. Below the pathological levels, BI patients have larger spinal canal than general population.

LEVEL OF EVIDENCE

3.

Central or Axial Atlantoaxial Dislocation as a Cause of Cervical Myelopathy: A Report of Outcome of 5 Cases Treated by Atlantoaxial Stabilization

OBJECTIVE

The implications of diagnosis and treatment of central or axial atlantoaxial dislocation (CAAD) as a cause of symptoms of cervical myelopathy are evaluated.

METHODS

This is a report of a series of 5 patients who presented with the primary symptoms of spasticity and motor weakness and paresthesias in all the limbs. There was no evidence of any significant compression of the dural tube or neural structures at the craniovertebral junction. There was no craniovertebral junction instability when assessed by classically described radiologic parameters. CAAD was diagnosed based on our recently discussed parameter of facetal alignment, corroborative clinical and radiologic evidence, and direct observation of atlantoaxial instability by manual manipulation of the bones of the region. All patients underwent atlantoaxial fixation.

RESULTS

There was remarkable improvement in the clinical symptoms in the immediate postoperative period and during the follow-up period of 12-24 months (average, 16 months). All patients have continued to have progressive clinical recovery. Clinical assessments were done using Goel clinical evaluation scale, Japanese Orthopedic Association score, and visual analog scale.

CONCLUSIONS

Identification and treatment of CAAD can have a significant management impact on patients where the cause of spastic quadriparesis is otherwise undiagnosed.

Multilevel Spinal Segmental Fixation for Kyphotic Cervical Spinal Deformity in Pediatric Age Group-Report of Management in 2 Cases

OBJECTIVE

We discuss the role of instability of multiple spinal segments including the atlantoaxial joint in the pathogenesis of cervical kyphotic deformity.

MATERIAL AND METHODS

Two male patients (5 and 17 years old) had severe cervical kyphosis and presented with symptoms related to myelopathy. The patients underwent multisegmental spinal distraction and fixation that included atlantoaxial joint. No bone decompression was done.

RESULTS

At a follow-up of >30 months, both patients had significant neurologic recovery. Investigations at follow-up showed successful arthrodesis of treated spinal segments. Although incomplete, there was recovery in kyphosis.

CONCLUSIONS

Multisegmental spinal distraction and fixation can lead to reduction in kyphosis and relief from symptoms related to myelopathy. Role of spinal instability in general and atlantoaxial joint instability in particular in pathogenesis of cervical kyphosis need to be assessed on the basis of studies with a larger number of patients.