Atlantoaxial Angle Research Articles

Peculiarities of changes in the sagittal balance of the cervical spine in cervicobrachial syndrome

Objective. To analyze clinical manifestations of cervicobrachial syndrome and identify their relationship with sagittal imbalance using data of MRI and radiological examination.Material and Methods. Clinical manifestations of cervicobrachial syndrome associated with degenerative changes in the spine were studied in 22 patients. Clinical examination, radiography of the cervical spine, electroneuromyography of the upper extremities, and MRI study were performed. The intensity of the pain syndrome was assessed by VAS, and the quality of life – by the NDI questionnaire. The sagittal balance of the cervical spine was evaluated according to the following characteristics: angle of T1 slope, atlantoaxial (C1–C2) angle, degree of shift of the center of gravity of C2–C7, and Cobb angle.Results. The pain intensity in cervicobrachial syndrome correlates with sagittal balance changes in the C2–C7 Cobb angle (r = 0.656; p < 0.05), the angle of T1 vertebra slope (r = 0.520; p < 0.05), and in the degree of shift of the center of gravity of C2–C7 (r = 0.756; p < 0.02). Differences between MRI and radiological results of the sagittal balance measurement are not significant (p < 0.04).Conclusion. The study of the sagittal balance can be included in the algorithm for diagnosing osteochondrosis of the cervical spine. The MRI, along with spondylography, can be used to assess the state of sagittal balance. Understanding the identified relationships can help in determining the program of etiopathogenetic treatment of patients with cervicobrachial syndrome with obligatory including the sagittal balance correction in the program.

Torticollis Caused by Nontraumatic Craniovertebral Junction Abnormalities.

Torticollis could be the only symptom and sign of craniovertebral junction (CVJ) abnormality. It could be difficult to identify CVJ abnormality as a cause of torticollis due to their rarity, especially for the subjects with torticollis caused by nontraumatic CVJ abnormalities. There has been no report to focus on nontraumatic CVJ abnormalities as a cause of torticollis. The objective of this study was to report 27 patients of torticollis caused by nontraumatic CVJ abnormalities, with the aim of helping clinicians to identify nontraumatic CVJ abnormalities as a cause of torticollis. This is a retrospective cohort study including 27 subjects who had torticollis caused by nontraumatic CVJ abnormalities. The CVJ was examined in terms of atlanto-occipital angle, atlanto-axial angle, and lateral and anterior atlanto-dens intervals for the evaluation of occipital condylar hypoplasia, rotation of atlanto-axial joint, and lateral and anterior shift of the dens, respectively. Abnormalities of the lower cervical or thoracic spine were also evaluated. Occipital condylar hypoplasia, rotation of atlanto-axial joint, and lateral shift of the dens were the most common CVJ abnormalities. The 18.5% of the subjects had concurrent anomalies of lower cervical or thoracic vertebrae along with CVJ abnormalities. Each subject had 2.22 ± 1.10 types of CVJ abnormalities on average. In conclusion, comprehensive evaluation of CVJ abnormalities is recommended for differential diagnosis of subjects with unexplained torticollis. Once CVJ abnormalities are identified, concurrent abnormalities of other vertebrae need to be evaluated.

Long-Term Influence of C1-C2 Pedicle Screw Fixation on Occipitoatlantal Angle and Subaxial Cervical Spine in the Pediatric Population

Objective: The goal of this study was to evaluate the impact of C₁-C₂ pedicle screw fixation on the occipitoatlantal angle and subaxial cervical spine for a pediatric population, and the clinical efficacy and adjacent-segment degeneration after C₁-C₂ pedicle screw fixation with a minimum of 2 years of follow-up. Methods: Twenty-two pediatric patients with atlantoaxial dislocation who were enrolled in this study underwent atlantoaxial pedicle screw fixation. The correlation between C₀-C₁, C₂-C₇, and C₁-C₂ pre- and postoperative sagittal angles was assessed using plain radiographs, and adjacent-segment degeneration (ASD) and JOA scores (Japanese Orthopaedic Association scores) were evaluated after atlantoaxial pedicle screw fixation. Results: The C₁-C₂ angle increased from 16.1 ± 13.37 to 28.1 ± 5.1° (p < 0.01). The pre- and postoperative C₁-C₂ angles were negatively correlated with the pre- and postoperative C₀-C₁ and C₂-C₇ angles, respectively. In accordance with the optimal atlantoaxial fusion angle (25-30°) obtained from the literature, postoperative JOA scores were greater in the groups with angles of more than 30° and less than 25°, although the difference in ASD was not statistically significant. Postoperative JOA scores were not relevant to the postoperative C₁-C₂ angle; however, there was a positive correlation between JOA improvement rate and the change of the C₁-C₂ angle postoperatively. Conclusion: Atlantoaxial pedicle screw fixation can be used easily to reduce atlantoaxial dislocation in the pediatric population; however, outside the range of the optimal atlantoaxial fusion angle it can change the occipitoatlantal angle and subaxial alignment, which induces ASD and influences the clinical efficacy. It is necessary to achieve an optimal atlantoaxial angle when using atlantoaxial pedicle screw fixation.

Non-traumatic Atlanto-axial Rotatory Subluxation- Grisel’s Syndrome Case Report and Literature Review

Study design: Case report of conservatively treated non-traumatic Atlanto-axial rotatory sublaxation. Objective: To report our case with this rare condition (non-traumatic Atlanto-axial rotatory subluxation-Grisel Syndrome) in a 9-year old girl presenting with torticollis and neck pain and literature review. Summary of background data: Atlanto-axial rotatory fixation or non-traumatic atlanto-axial subluxation which is usually secondary to an infection or an inflammation at the head and neck region is a rare subtype of subluxation in which a pathologic fixation of the atlas on the axis is present. It is most common in paediatric patients and it can be managed conservatively in the acute stage. In contrast, cases of chronic non-traumatic atlanto-axial rotatory subluxation are usually treated with operative reduction, according to literature data. Although high success rates have been achieved with operative reduction in chronic cases, a significant reduction in neck motion occurs due to the atlanto-axial fusion. Methods: A 9-year-old girl developed torticollis established longer than 10 weeks as a result of an upper respiratory tract infection. Computed tomography showed a type 1 rotatory subluxation of the Atlanto-axial joint according to the classification of Fielding and Hawkins. The patient was treated by manual reduction according to Jeszenszky (Jeszenszky transoral Citation Nr 22) under general anaesthesia and fluoroscopy control, and then a halo vest had been applied for 6 weeks. Results: We successfully treated this patient with chronic non-traumatic Atlanto-axial rotatory subluxation with manual reduction and immobilisation by applying a halo-body-jacket. She showed full recovery of neck motion and normal Atlanto-axial angle on clinical and radiological follow-up after 1 month and 3 months respectively. Conclusion: Chronic non-traumatic Atlanto-axial rotatory subluxation is a rare condition which can easily escape the attention of physicians especially in children. Conservative treatment with complete reduction under anaesthesia and subsequent immobilisation via halo-body-jacket for at least 6 weeks is a viable option as presented in this case report. Surgical treatment should be reserved only for cases of failure of conservative management (recurrence or irreducible subluxation).

Effect of a reduction of the atlanto-axial angle on the cranio-cervical and subaxial angles following atlanto-axial arthrodesis in rheumatoid arthritis

We retrospectively investigated the radiographic findings in patients with atlanto-axial subluxation (AAS) due to rheumatoid arthritis, and clarified the effect of reduction of the atlanto-axial angle (AAA) on the cranio-cervical and subaxial angles. Forty-one patients, consisting of 29 females and 12 males, with AAS treated by surgery were reviewed. The average patient age at surgery was 61.0years, and the average follow-up period was 4.0years. We investigated the AAA at the neutral position in lateral cervical radiographs before surgery and at the last follow-up. In addition, we also investigated the clivo-axial angle (CAA) and the subaxial angle (SAA) at the neutral position before and after surgery. Due to pre-operative AAA, the patients were classified into three groups as follows: (1) the kyphotic group (K group), (2) the neutral group (N group), and (3) the lordotic group (L group). The average AAA values at the neutral position in the K group before and after surgery were 6.0° and 18.1°, respectively (P<0.001). In the N group 19.7° and 21.7°, respectively (P<0.05), and in the L group 31.6° and 27.0°, respectively (P<0.01). However, no significant differences in the average CAA values were found before and after surgery in all groups. Furthermore, no significant differences in the SAA values were seen before and after surgery in all groups. A proper reduction of the AAA did not affect the cranial angles or induce kyphotic malalignment of the subaxial region after atlanto-axial arthrodesis. However, if we can obtain a significant and large reduction of AAA in patients showing kyphosis before surgery, then this reduction will be offset in the atlanto-occipital joint and we should therefore pay special attention to its morphology after surgery.

Rheumatoid vertical and subaxial subluxation can be prevented by atlantoaxial posterior screw fixation

Literature has described a risk for subsequent vertical subluxation (VS) and subaxial subluxation (SAS) following atlantoaxial subluxation in rheumatoid patients; however, the interaction of each subluxation and the radiographic findings for atlantoaxial fixation has not been described. The purpose of this study was to evaluate the effects of two different posterior atlantoaxial screw fixation on the development of subluxation in patients with rheumatoid atlantoaxial subluxation. Between 1996 and 2006, rheumatoid patients treated with transarticular fixation and posterior wiring (TA) or C1 lateral mass-C2 pedicle screw fixations (SR) in the Nagoya Spine Group hospitals, a multicenter cooperative study group, were included in this study. VS, SAS, craniocervical sagittal alignment, and range of motion (ROM) at the atlantoaxial adjacent segments were investigated to determine whether posterior atlantoaxial screw fixation is a prophylactic or a risk factor for the development of VS and SAS. The mean follow-up was 7.2 years (4-12). No statistically significant difference was observed among the patients treated with either of the procedure during the follow-up period. Of 34 patients who underwent posterior atlantoaxial screw fixation, SAS was observed in 26.5 % during the follow-up period; however, VS was not observed. Postoperative C2-7 angle, and Oc-C1 and C2-3 ROM were significantly different between patients with and without postoperative SAS. The incidence of SAS was 38.9 % for TA and 12.5 % for SR; statistically significant differences were observed in the postoperative C1-2 and C2-7 angles, and C2-3 ROM. Atlantoaxial posterior screw fixation may be an appropriate prophylactic intervention for VS and SAS if the atlantoaxial joint develops bony fusion following physiological alignment. Compared to TA, SR provided optimal atlantoaxial angle and prevented lower adjacent segment degeneration, thereby reducing SAS.

Atlanto-axial joint of atlanto-axial subluxation patients due to rheumatoid arthritis before and after surgery, morphological evaluation using CT reconstruction

This study investigated the preoperative morphology and postoperative fusion of the atlanto-axial joint (AAJ) in patients with atlanto-axial subluxation (AAS) due to rheumatoid arthritis (RA) using computed tomography (CT). Furthermore, we examined the relationship between the preoperative morphology of AAJ and other radiographic results. Thirty patients with AAS due to RA treated by C1-2 transarticular screw fixation (TSF) were reviewed. The morphology of the AAJ was evaluated using sagittal reconstruction views on CT before and 1 year after surgery. Thereafter, the atlanto-dental interval (ADI) value at the neutral and maximal flexion position and atlanto-axial angle (AAA) at the neutral position was assessed in preoperative lateral cervical radiographs. The preoperative morphology of the AAJ on CT reconstruction views was graded as follows: Grade 1 showed maintenance of the joint space, Grade 2 showed the joint space narrowing and Grade 3 showed the destructive abnormality of subchondral bone. After surgery, the ADI value at the neutral position was assessed in lateral cervical radiographs. Furthermore, the fusion in the AAJ was investigated using CT sagittal reconstruction views taken 1 year after surgery. The preoperative CT image of the AAJ demonstrated Grade 1 in 12 cases (Group A), Grade 2 in 9 cases (Group B) and Grade 3 in 9 cases (Group C). There was no significant difference in age, gender and duration of RA among the three groups. The average ADI value at the flexion position was 11.0 mm in Group A, 12.3 mm in Group B and 12.7 mm in Group C (p>0.313). The average ADI value at the neutral position before surgery was 4.5 mm in Group A, 7.3 mm in Group B and 11.4 mm in Group C (p<0.003). The mean AAA value was 20.8° in Group A, 21.8° in Group B and 8.4° in Group C (p<0.033). The average ADI value after TSF was 1.7 mm in Group A, 2.1 mm in Group B and 3.0 mm in Group C (p>0.144). Fusion in the AAJ 1 year after surgery was demonstrated in 14 cases (46.7%; Group A, 0 case; Group B, 5 cases; Group C, 9 cases). According to the preoperative grading of the AAJ, the postoperative fusion in the AAJ was demonstrated in 0 of 32 joints (0%) in Grade 1, 7 of 18 joints (38.9%) in Grade 2 and all of 10 joints (100%) in Grade 3. In conclusion, this study showed that a destructive abnormality of subchondral bone in the AAJ induced an enlargement of the ADI and anterior inclination of the atlas in patients with AAS due to RA. The current study also showed that fusion in the AAJ was demonstrated in 14 of 30 patients after C1/2 TSF. This was easy to recognize in AAS patients whose joint destruction extended to the subchondral bone.

Subaxial sagittal alignment and adjacent-segment degeneration after atlantoaxial fixation performed using C-1 lateral mass and C-2 pedicle screws or transarticular screws

The purpose of this study was to evaluate the effect of a fixed atlantoaxial angle on subaxial sagittal alignment, and that of atlantoaxial fixation on adjacent-segment motion and degeneration. The authors retrospectively reviewed 65 patients in whom atlantoaxial instability was treated with atlantoaxial fixation by C-1 lateral mass and C-2 pedicle screw fixation (30 patients, Goel-Harms [GH] group) or a combination of transarticular screw fixation and posterior wiring (35 patients, Magerl-Brooks [MB] group). Angles of Oc–C1, C1–2, C2–3, and C2–7 were determined based on an upright lateral radiograph in flexion, neutral, and extension positions. The range of motion (ROM) at Oc–C1 and C2–3 was also determined. All patients were examined before and 2 years after surgery. The mean preoperative atlantoaxial angles in the GH and MB groups were 20.9 ± 8.3° and 18.3 ± 7.2°, respectively, and the mean postoperative atlantoaxial angles in the same groups were 23.5 ± 5.6° and 29.7 ± 6.3°, respectively, with a statistically significant difference between the 2 groups (p < 0.05). The mean preoperative angles of C2–7 in the GH and MB groups were 15.4 ± 7.8° and 13.7 ± 9.5°, respectively, and after surgery, the angles were 11.8 ± 12° and 2.48 ± 12°, respectively, with a statistically significant difference between the 2 groups (p < 0.05). The postoperative angle of C1–2 showed a negative correlation with the extent of change observed in the C2–7 angle pre- and postoperatively in each of these 2 surgical procedures. The Oc–C1 ROM increased after surgery in both groups, but the difference was not statistically significant (p = 0.38). The C2–3 ROM decreased after surgery in both groups, and the difference was statistically significant (p < 0.05). Atlantoaxial fixation in a hyperlordotic position produced kyphotic sagittal alignment after surgery in both GH and MB groups. Reduction of the atlantoaxial joint can be easily achieved through screw fixation at an optimal angle, thereby ameliorating the risk for subsequent subaxial kyphosis. Degeneration of lower adjacent segments appeared to be less with this procedure compared with using a combination of transarticular screw fixation and posterior wiring.

C1–C2 Intra-articular Screw Fixation for Atlantoaxial Subluxation Due to Rheumatoid Arthritis

While various surgical procedures have been developed for the treatment of atlantoaxial subluxation due to rheumatoid arthritis, C1-C2 intra-articular screw fixation was developed to reduce intraoperative injuries to vertebral arteries. The purpose of this study was to report the therapeutic outcome of this procedure, which was followed for >2 years. Preoperative symptoms were alleviated in all patients. Only 1 patient with subaxial canal stenosis underwent additional laminoplasty during follow-up. All patients with class IIIA or milder neural deficit according to Ranawat's classification showed improvement to class I or II. There were no surgery-related complications or incidents, including injuries to vertebral arteries. Bone union was observed in all patients. No change was observed in the reduced atlas-dens interval during follow-up. The atlantoaxial angle was -6 degrees to 30 degrees (average, 19.4 degrees) at follow-up, and was >or=30 degrees after surgery (fusion in an overextended position) in only 1 patient. Although postoperative deterioration of cervical alignment was observed in 4 patients (18.2%), there was no additional surgery due to deterioration of cervical alignment. With no surgery-related complications or incidents, this procedure could be a safe and acceptable option for atlantoaxial subluxation due to rheumatoid arthritis.

Relationship between the morphology of the atlanto-occipital joint and the radiographic results in patients with atlanto-axial subluxation due to rheumatoid arthritis

The upper cervical spine is a common focus of destruction from rheumatoid arthritis (RA). Atlanto-axial subluxation (AAS) presents with marked frequency among patients with instability. However, there are occasional patients who show no motion between the occipital bone and atlas on a dynamic cervical radiograph in AAS patients. This study investigated the morphology of the atlanto-occipital joint (AOJ) in AAS patients due to RA using computed tomography, and examined the relationship between its morphology and other radiographic results. Twenty-six consecutive patients with AAS due to RA treated by surgery were reviewed. The subjects included 18 females and 8 males. The average patient age was 59.3 years. The mean duration of RA was 14.3 years. In all the patients, the AOJ was morphologically evaluated using sagittal reconstruction view on computed tomography before surgery. Moreover, the ADI value was investigated at the neutral and maximal flexion position, and atlanto-axial angle (AAA) at the neutral position in preoperative lateral cervical radiographs. The morphology of the AOJ on a CT sagittal reconstruction view was classified into three types as follows: a normal type which showed a maintenance of the joint space, a narrow type which showed a disappearance of the joint space and a fused type which showed the fusion of the AOJ. The pre-operative CT sagittal reconstruction image of the AOJ demonstrated a normal type bilaterally in six cases (Group A). In 15 cases (Group B), CT image demonstrated narrowing on at least one side of the AOJ. In five cases (Group C), CT images demonstrated fusion on at least one side of the AOJ. The average ADI value at the flexion position was 10.7 mm in Group A, 11.7 mm in Group B, and 12.6 mm in Group C. There was no significant difference among those groups. The average ADI value at the neutral position before surgery was 2.8 mm in Group A, 5.9 mm in Group B, and 10.4 mm in Group C. There was no significant difference between Group A and B (P > 0.105), and Groups B and C (P > 0.032), however, there was a significant difference between Groups A and C (P < 0.004). The average AAA value was 25.3 degrees in Group A, 19.3 degrees in Group B and 3.4 degrees in Group C. There was no significant difference between Groups A and B (P > 0.230), however, there was a significant difference between Groups A and C (P < 0.002), and Groups B and C (P < 0.007). This study showed that fusion or ankylosis of the AOJ induced an enlargement of the ADI and anterior inclination of the atlas in the neutral position, despite the fact that normal findings of AOJ showed a slight displacement of the atlas to axis in RA patients showing AAS involvement. This morphology may progress to SAS and VS due to AOJ after atlanto-axial arthrodesis.

Relation between atlantoaxial (C1/2) and cervical alignment (C2–C7) angles with Magerl and Brooks techniques for atlantoaxial subluxation in rheumatoid arthritis

BackgroundA few studies have reported the relation between the atlantoaxial (C1/2) angle and cervical alignment (C2–C7) angle after a Magerl and Brooks (M&B) surgical procedure to treat atlantoaxial subluxation (AAS) in patients with rheumatoid arthritis (RA). However, no study has examined an optimum preoperative C1/2 angle reduction. We aimed to assess the relation between the C1/2 angle reduction and the C2–C7 angle change in patients with progressive RA who underwent the M&B procedure. MethodsWe retrospectively analyzed the relation between the preoperative C1/2 angle and C2–C7 angle in 28 consecutive RA patients using their clinical and radiological data. Differences in the preoperative and postoperative C1/2 and C2–C7 angles were detected. Correlations of these angles and the reduced degree of angles were examined. The Ranawat grading scale and Japanese Orthopaedic Association (JOA) scores were used to determine myelopathy. Pain was categorized into five categories according to severity. Clinical and Xray evaluations were collected before surgery, at 3 and/or 6months after surgery, and at final follow-up. ResultsClinical symptoms, Ranawat grade, and JOA scores improved postoperatively, and patients achieved bony union within 3months. We observed a strong and significant correlation between the reduced C1/2 angle and the change in the C2–C7 angle. Patients with a preoperative C1/2 angle of <20° had markedly reduced cervical lordotic angle but this condition was not seen in patients with a preoperative C1/2 angle of ≥20°. The optimum C1/2 angle was estimated as [20°−(preoperative C1/2 angle)] in patients with a C1/2 angle <20° or as an in situ angle in patients with a C1/2 angle of ≥20°. ConclusionsSurgeons performing the M&B procedure need to select patients carefully and avoid complete or overreduction of the C1/2 angle to prevent serious postoperative SAS and myelopathy.

Successful Reduction for a Pediatric Chronic Atlantoaxial Rotatory Fixation (Grisel syndrome) With Long-term Halter Traction

Clinical case report of atlantoaxial rotatory fixation (AARF) in a girl presenting with torticollis and neck pain. To report this rare case that was successfully treated with long-term traction and a brace. AARF is a rare kind of subluxation that is a pathologic fixation of the atlas on the axis. It is most common in pediatric patients and is usually reduced easily with conservative treatments only in the acute stage. However, previously reported chronic AARFs have usually been treated with operative reductions. Although high success rates have been achieved with operative reduction in chronic cases of AARF, even successful operative reduction may result in significant neck motion limitation. A 9-year-old girl had torticollis of more than 3 months duration develop as a result of an upper respiratory infection. Dynamic computerized tomography showed consistent fixation of the atlantoaxial joint consistent with type 1 AARF according to the classification of Li and Pang. The patient was treated with halter traction of 5-lb weight for 6 weeks, and with a brace for 4 months and collar for 2 months. We successfully treated this patient with chronic AARF only with cervical traction. She had full recovery of neck motion and normal atlantoaxial angle on follow-up computerized tomography after 6 months. From this case, we suggest that long-term traction could be another treatment method for chronic AARF, especially in children.

Impact of interlaminar graft materials on the fusion status in atlantoaxial transarticular screw fixation

Structural interlaminar graft materials were used for atlantoaxial transarticular screw fixation (TSF), and its impact on the fusion status was investigated. Forty-two patients (10 men, 32 women, mean age 51 years, mean follow-up period 45 months; 30 with rheumatoid arthritis, and 12 with os odontoideum) underwent TSF and modified Brooks posterior wiring involving titanium cables. As interlaminar graft materials, autologous bone from posterior iliac crest alone was used in 20 patients (Group A), and a structural spacer (13 ceramic spacers, nine titanium mesh cages) in 22 (Group B). Lateral radiographs were evaluated to determine bone fusion, alignment of the cervical spine, and wire loosening. Solid osseous fusion was obtained in 95% of Group A and 96% of Group B patients. The mean atlantoaxial angle was 19.1+/-9.7 degrees and 16.7+/-10.4 degrees before surgery (p = 0.45), and 27.4+/-7.8 degrees and 22.1+/-5.5 degrees after surgery (p = 0.02) in Groups A and B, respectively. Atlantoaxial hyperlordosis (atlantoaxial angle > or = 30 degrees) was observed in 32% of Group A and 18% of Group B patients (p = 0.26). Postoperative kyphosis occurred in 40% of Group A and 23% of Group B patients (p = 0.28). Loosening of the cable was demonstrated in 50% of Group A and 36% of Group B patients(p = 0.37). In Group B patients maintenance of cervical lordosis was more likely than in those in Group A, although the differences did not reach statistical significance. These results indicate that structural interlaminar spacers can maintain proper cervical alignment without a decease in the fusion rate; the authors recommend their use in conjunction with TSF.

Pitfalls of magnetic resonance imaging of alar ligament.

An observational study of variations in the appearance of the alar ligament on magnetic resonance imaging (MRI) and the normal range of lateral flexion and rotation of the atlas was performed to validate some of the premises underlying the use of MRI for the detection of injuries to the alar ligament. Fifteen healthy volunteers were included. Three sets of coronal proton-density images, and axial T2-weighted images of the craniovertebral junction, were obtained at 0.5 T with the neck in neutral position and laterally flexed (coronal proton density) or rotated (axial T2). Five of the subjects also underwent imaging at 1.5 T. The scans were independently examined twice by two radiologists. The presence of alar ligaments was recorded and a three-point scale used to grade the extent of hyperintensity exhibited by the structures: the ligament were graded as 2 and 3 if, respectively, less or more of its cross-section was hyperintense, whereas grade 1 represented a hypointense ligament. The effect of lateral flexion on image quality was assessed. Concordance analysis of the data were performed before and after dichotomising the data on grading. The atlanto-axial angle and rotation of the atlas were measured. The magnitude of movement to right was normalised to that to the left to give, respectively, the flexion index and the rotation index. The alar ligaments were most reliably seen on coronal proton-density scans, with a Maxwell's RE of 0.96 as compared with 0.46 for sagittal images. Flexion of the neck improved definition of the ligaments in only rare instances. Inter-observer disagreement was marked with respect to grading of the ligament on both coronal [composite proportion of agreement (p0)=0.44; 95% confidence intervals: 0.26, 0.64)] and sagittal scans [p0=0.40 (0.19, 0.63)]. Dichotomising the data did not appreciably improve reliability [Maxwell's RE: -0.11 (coronal scans), -0.20 (sagittal scans)]: for ligaments which demonstrated hypertensive areas (grades 2 and 3) there was complete lack of agreement for both coronal [p2=0 (0, 0.25)] and sagittal scans [p2=0 (0-0.30)]. A large response bias was found in the reports of both readers albeit in opposite directions. There was poor concordance between scans obtained at different field strengths [RE (coronal images)=0.25; RE (sagittal images)=0.14). Mean flexion index and mean rotation index were 1.00 (SD 0.03) and 1.01 (SD 0.06), respectively. The MR imaging may not be the investigation of choice for the investigation of subtle injuries to the alar ligament. Whether it can be substituted by kinematic assessment of the occipito-atlanto-axial complex with MRI warrants investigation.

Atlantoaxial rotatory fixation-subluxation revisited: a computed tomographic analysis of acute torticollis in pediatric patients.

Cross-sectional clinical and radiologic study with a normal control group. To compare the range of motion of the atlantoaxial joint in patients with acute torticollis with those of normals as measured from computed tomography scans, to look for the existence of atlantoaxial rotatory fixation in any position (subluxation or normal range of motion) in this group of patients, and to clarify the definition of atlantoaxial rotatory subluxation by measuring the atlantodental interval and analyzing the location of the center of rotation in patients as well as normal controls. Although acute acquired torticollis is usually termed atlantoaxial rotatory subluxation or atlantoaxial rotatory fixation, the radiologic definition of these conditions is not clear. Thirty-three consecutive pediatric patients (average age 8.5 years, range 2-18 years) with acute acquired torticollis were analyzed. All were neurologically intact. Anteroposterior and lateral radiographs were obtained in all atlantoaxial computed tomography scans in 31 patients (dynamic in 23 and static in 8). Twelve age-matched patients with normal cervical spines were also analyzed with dynamic computed tomography as normal controls. Atlantoaxial rotatory subluxation, atlantoaxial angle, center of rotation, and presence of atlantoaxial rotatory fixation were analyzed in each computed tomography. All patients were treated conservatively. Eight had control dynamic computed tomography scans at the end of the treatment. All patients had atlantoaxial rotatory subluxation <or=3 mm. On dynamic computed tomography, the range of atlantoaxial rotation was 30.4 degrees (range 11-54 degrees) toward deformity and 28.3 degrees (range 18-54 degrees) away from deformity (P = 0.333). Atlantoaxial rotatory fixation was not noted in any of the patients. The same measurement for the normal control group was 28 degrees (range 5-41 degrees) (P = 0.770). Of the eight patients with repeat control computed tomography, the atlantoaxial rotatory subluxation was 26 degrees before and 29 degrees after treatment (P = 0.691 to right and P= 0.199 to left). The center of rotation was within dens in 15 of 19 patients, outside dens in 2 of 19, and undetectable in 2 of 19. In the control group, it was within dens in 8 of 11, outside dens in 2 of 11, and undetectable in 1 of 11. All patients were symptom free at the end of the conservative treatment. We could not demonstrate the presence of atlantoaxial rotatory subluxation or atlantoaxial rotatory fixation in our series of 33 consecutive pediatric patients with acute torticollis. Our findings suggest that the existence of these phenomena are doubtful, although not associated with acute acquired torticollis. Acute acquired torticollis is not necessarily the sign of a pathologic condition of the atlantoaxial joint. Finally, it is probably not necessary to obtain computed tomography scans (static or dynamic) in this group of patients at the time of presentation.

Atlantoaxial Rotatory Fixation–Subluxation Revisited

Study Design. Cross-sectional clinical and radiologic study with a normal control group. Objectives. To compare the range of motion of the atlantoaxial joint in patients with acute torticollis with those of normals as measured from computed tomography scans, to look for the existence of atlantoaxial rotatory fixation in any position (subluxation or normal range of motion) in this group of patients, and to clarify the definition of atlantoaxial rotatory subluxation by measuring the atlantodental interval and analyzing the location of the center of rotation in patients as well as normal controls. Summary of Background Data. Although acute acquired torticollis is usually termed atlantoaxial rotatory subluxation or atlantoaxial rotatory fixation, the radiologic definition of these conditions is not clear. Patients and Methods. Thirty-three consecutive pediatric patients (average age 8.5 years, range 2–18 years) with acute acquired torticollis were analyzed. All were neurologically intact. Anteroposterior and lateral radiographs were obtained in all atlantoaxial computed tomography scans in 31 patients (dynamic in 23 and static in 8). Twelve age-matched patients with normal cervical spines were also analyzed with dynamic computed tomography as normal controls. Atlantoaxial rotatory subluxation, atlantoaxial angle, center of rotation, and presence of atlantoaxial rotatory fixation were analyzed in each computed tomography. All patients were treated conservatively. Eight had control dynamic computed tomography scans at the end of the treatment. Results. All patients had atlantoaxial rotatory subluxation ≤3 mm. On dynamic computed tomography, the range of atlantoaxial rotation was 30.4° (range 11–54°) toward deformity and 28.3° (range 18–54°) away from deformity (P = 0.333). Atlantoaxial rotatory fixation was not noted in any of the patients. The same measurement for the normal control group was 28° (range 5–41°) (P = 0.770). Of the eight patients with repeat control computed tomography, the atlantoaxial rotatory subluxation was 26° before and 29° after treatment (P = 0.691 to right and P = 0.199 to left). The center of rotation was within dens in 15 of 19 patients, outside dens in 2 of 19, and undetectable in 2 of 19. In the control group, it was within dens in 8 of 11, outside dens in 2 of 11, and undetectable in 1 of 11. All patients were symptom free at the end of the conservative treatment. Conclusion. We could not demonstrate the presence of atlantoaxial rotatory subluxation or atlantoaxial rotatory fixation in our series of 33 consecutive pediatric patients with acute torticollis. Our findings suggest that the existence of these phenomena are doubtful, although not associated with acute acquired torticollis. Acute acquired torticollis is not necessarily the sign of a pathologic condition of the atlantoaxial joint. Finally, it is probably not necessary to obtain computed tomography scans (static or dynamic) in this group of patients at the time of presentation.

Ｏｓ ｏｄｏｎｔｏｉｄｅｕｍに伴う環軸椎亜脱臼の病態と手術法の検討

Atlantoaxial subluxation (AAS) with os odontoideum is more unstable than AAS without it. We investigated the surgical results of symptomatic AAS with os odontoideum. Eleven males and 16 females (mean age: 38 years) underwent surgery. Fifteen patients showed myelopathy (mean JOA score: 9.4), and 12 had only local symptoms without myelopathy. Three parameters on the lateral radiographs (minimum diameter in flexion, maximum diameter in extension and atlanto-axial angle in flexion and extension) were measured preoperatively, and the instability index was calculated. Manipulation (18) or anterior release (3) reduced AAS in 21 patients. Posterior atlanto-axial fusion and bone graft were performed with wiring (9), transarticular screw fixation with wiring (9), and Olerud Cervical fixation (3). In 6 patients, AAS was not reduced and occipito-cervical fusion was performed. Correction loss and union rate were investigated on the postoperative lateral radiograph. The mean follow-up was 5 years and 4 months. There was no significant difference between preoperative radiological values and clinical symptoms. The mean JOA score improved to 13.0 after surgery, and the improvement rate was 52.3%. Four patients treated with wiring showed correction loss. Three of them developed non-union and required re-operation. Bone union was achieved with other fixations.

Progression of rheumatoid arthritis of the cervical spine: radiographic and clinical evaluation

Cross-sectional and longitudinal studies were conducted to observe progression of rheumatoid arthritis in the cervical spine. Two hundred and ninety-seven patients were enrolled in the cross-sectional study. Both upper and lower cervical spine involvement increased with disease duration. The relationship between atlanto-axial motion and the development of subaxial subluxation was inconclusive. Eighty-seven patients were enrolled in the longitudinal study and were followed for at least 5 years. In about half of these patients, rheumatoid changes started from the upper cervical spine, with rheumatoid changes beginning from the lower cervical spine in about 8% of patients. Neurological deficits were correlated with radiographic changes but neck pain did not correlate with radiographic changes. As to the upper cervical spine, the parameter most influencing neurological deficits was found to be the minimum value of the atlanto-axial angle in flexion, by multivariate analysis using a multiple logistic model. Neurological deficits were seen in more than half the patients when the atlanto-axial angle in flexion was 5° or less.

ATLANTOAXIAL INSTABILITY IN OS ODONTOIDEUM WITH MYELOPATHY

Study design This study analyzed the correlation between the atlantoaxial instability (especially sagittal plane rotatory instability) and myelopathy. Thirty-four patients with os odontoideum were reviewed in clinical symptoms and radiographs. Objectives The results were correlated to provide a rationale for the genesis of myelopathy. Summary of background data Instability of the atlantoaxial joint has been evaluated with atlantodental interval, space available for the spinal cord, instability index, and others. These are excellent indices for anteroposterior instability. However, they are insufficient for the evaluation of the multidirectional instability in os odontoideum. Methods Thirty-four patients were analyzed in three parameters on the lateral radiographs: the minimum distance from the posterior border of the C2 body to the posterior arch of atlas, the difference of the atlanto-axial angle between the flexion and extension position (sagittal plane rotation angle), and the change of space available for the spinal cord from flexion to extension (Instability Index). Results The correlation between the sagittal plane rotation angle and the instability index was low (r = 0.561). In patients with more than 20 degrees of the sagittal plane rotation angle, myelopathy was shown at a high rate (86%). Myelopathy was also shown at a high rate (90%) in the patients with more than 40% of the instability index. Conclusions It is important to check the sagittal plane rotation angle and the instability index to evaluate the instability in os odontoideum. If the patient has either a sagittal plane rotation angle of more than 20 degrees or an instability index of more than 40%, he or she is likely to have the cord signs.

Atlantoaxial instability in os odontoideum with myelopathy.

This study analyzed the correlation between the atlantoaxial instability (especially sagittal plane rotatory instability) and myelopathy. Thirty-four patients with os odontoideum were reviewed in clinical symptoms and radiographs. The results were correlated to provide a rationale for the genesis of myelopathy. Instability of the atlantoaxial joint has been evaluated with atlantodental interval, space available for the spinal cord, instability index, and others. These are excellent indices for anteroposterior instability. However, they are insufficient for the evaluation of the multidirectional instability in os odontoideum. Thirty-four patients were analyzed in three parameters on the lateral radiographs: the minimum distance from the posterior border of the C2 body to the posterior arch of atlas, the difference of the atlanto-axial angle between the flexion and extension position (sagittal plane rotation angle), and the change of space available for the spinal cord from flexion to extension (Instability Index). The correlation between the sagittal plane rotation angle and the instability index was low (r = 0.561). In patients with more than 20 degrees of the sagittal plane rotation angle, myelopathy was shown at a high rate (86%). Myelopathy was also shown at a high rate (90%) in the patients with more than 40% of the instability index. It is important to check the sagittal plane rotation angle and the instability index to evaluate the instability in os odontoideum. If the patient has either a sagittal plane rotation angle of more than 20 degrees or an instability index of more than 40%, he or she is likely to have the cord signs.