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

Radiographic Predictors of Subaxial Subluxation After Atlantoaxial Fusion

STUDY DESIGN

A retrospective study.

OBJECTIVE

The aim of this study was to clarify preoperative radiographic predictors associated with the development of subaxial subluxation (SAS) after surgery.

BACKGROUND

The incidence of atlantoaxial fusion for atlantoaxial instability has been increasing. SAS can develop after surgery despite atlantoaxial fusion with the optimal C1-C2 angle. We hypothesized that preoperative discordant angular contribution in the upper and subaxial cervical spine is associated with the occurrence of postoperative SAS.

MATERIALS AND METHODS

Patients who underwent surgery for atlantoaxial instability with a minimum 5-year follow-up and control participants were included. The O-C2 angle, C2 slope (C2S), C2-C7 cervical lordosis (CL), and T1 slope (T1S) were measured. We focused on the angular contribution ratio in the upper cervical spine to the whole CL, and the preoperative C2/T1S ratio was defined as the ratio of C2S to T1S.

RESULTS

Twenty-seven patients (SAS=11, no-SAS=16; mean age, 60.7 y old; 77.8% female; mean follow-up duration, 6.8 y) and 23 demographically matched control participants were enrolled. The SAS onset was at 4.7 postoperative years. Preoperatively, the O-C2 angle, C2-C7 CL, and T1S were comparable between the SAS, no-SAS, and control groups. The preoperative C2S and C2/T1S ratio were smaller in the SAS group than in the no-SAS or control group (C2S, 11.0 vs. 18.4 vs. 18.7 degrees; C2/T1S ratio, 0.49 vs. 0.77 vs. 0.78, P <0.05). The receiver operating characteristic curve analysis demonstrated that the C2/T1S ratio had higher specificity and similar sensitivity as a predictor of postoperative SAS than C2S (specificity: 0.90 vs. 0.87; sensitivity: 0.73 vs. 0.73). The estimated cutoff values of the C2S and C2/T1S ratio were 14 degrees and 0.58, respectively.

CONCLUSIONS

The preoperative C2/T1S ratio was closely associated with postoperative SAS. Patients with a C2/T1S ratio <0.58 were at a high risk of SAS after atlantoaxial fusion.

LEVEL OF EVIDENCE

Level 4.

Subaxial lordosis loss and influence factors after posterior atlantoaxial fusion

Summary of background data

Cervical sagittal balance is an important evaluation index of cervical physiological function and surgical efficacy. Subaxial kyphosis after atlantoaxial fusion is negatively associated with worse clinical outcomes and higher incidence of lower cervical disk degeneration.

Objectives

This study aimed to confirm the factors that influence subaxial lordosis loss after posterior atlantoaxial fusion.

Methods

We performed a retrospective review of all patients following posterior C1–C2 fusion for atlantoaxial dislocation between January 2015 and December 2017. All charts, records, and imaging studies were reviewed for each case, and preoperative, immediate postoperative, and final follow-up plain films were evaluated. Comparing final follow-up and preoperative C2–C7 angle, patients were divided into two groups for further comparison: subaxial lordosis loss group and subaxial lordosis increase group.

Results

A total of 18 patients were included in the review, with an average radiographic follow-up of 8.4 ± 3.7 months (range 6–17 months). Subaxial lordosis loss was observed in 5 cases (27.8%) at the final follow-up, whereas 13 cases had an increase in subaxial lordosis. The cervical sagittal parameters of preoperative and final follow-up between two groups were compared, the preoperative C2–C7 angle of the subaxial lordosis loss group was bigger than the subaxial lordosis increase group (27.6° ± 10.5° vs 10.5° ± 10.5°, P < 0.05), but there was no statistical difference in other parameters. Univariate chi-square analysis showed that reduction in subaxial lordosis after posterior atlantoaxial fusion was associated with preoperative C2–C7 angle ≥ 20° (χ² = 4.923, P = 0.026). However, Logistic regression analysis showed that the preoperative C2–C7 angle ≥ 20° was not an independent risk factor (OR = 0.147, P = 0.225).

Conclusion

Our study demonstrates that subaxial lordosis loss may occur after posterior atlantoaxial fusion, and preoperative C2–C7 angle ≥ 20° was a risk factor of postoperative loss of subaxial lordosis.

Surgical resection of intradural extramedullary tumors in the atlantoaxial spine via a posterior approach

BACKGROUND

The anatomical features of the atlantoaxial spine increase the difficulty of complete and safe removal of atlantoaxial intradural extramedullary (IDEM) tumors. Studies concerning surgical interventions via a posterior approach are limited.

AIM

To investigate the safety and efficacy of atlantoaxial IDEM tumor resection using a one-stage posterior approach.

METHODS

We retrospectively analyzed clinical databases for one-stage atlantoaxial IDEM tumor resection via a posterior approach between January 2008 and January 2018. The analyzed data included tumor position, histopathological type, pre- and post-operative Japanese Orthopedic Association (JOA) scores and Nurick grades, postoperative complication and recurrence status.

RESULTS

A total of 13 patients who underwent C1-C2 Laminectomy and/or unilateral facetectomy via the posterior approach were enrolled in the study. In all cases reviewed, total tumor resection and concomitant C1-C2 fusion were achieved. The average follow-up was 35.3 ± 6.9 mo (range, 26-49 mo). A statistically significant difference was noted between the preoperative JOA score (11.2 ± 1.1) and the score at the last final follow-up (15.6 ± 1.0) (P < 0.05). A statistically significant difference was noted between the preoperative Nurick grade (2.3 ± 0.9) and that at the last follow-up (1.2 ± 0.4) (P < 0.05). However, no statistically significant difference was noted between the preoperative and last follow-up C1-2 Cobb angle and C2-7 Cobb angle (P > 0.05). No mortalities, severe complications or tumor recurrence were observed during the follow-up period.

CONCLUSION

Total resection of atlantoaxial IDEM tumors is feasible and effective via a posterior approach. Surgical reconstruction should be considered to avoid iatrogenic kyphosis and improve spinal stability and overall clinical outcomes.

Radiological changes in sagittal parameters after C1-C2 arthrodesis and their clinical correlation: Is there a difference between traumatic and non-traumatic causes?

Background: Compensatory changes in cervical sagittal alignment after C1-C2 arthrodesis have been reported in a few studies. No studies have explored the differences in these compensatory changes between traumatic and non-traumatic pathologies. Conflicting reports exist on the correlation between cervical sagittal parameters and neck pain or function.Methodology: Medical records of 81 consecutive patients [Jan 2010 - Dec 2018] who underwent Harms arthrodesis were retrospectively reviewed. 53 patients were included in the final analysis. Radiological parameters [C0-C1, C1-C2, C2-C7 angles and T1 slope] and clinical parameters [VAS (Visual analogue scale) and NDI (Neck disability index)] were compared between the two groups, Group A (traumatic) and Group B (non-traumatic).Results: The 53 patients [Group A (n = 24,) and Group B (n = 29)] had a mean age of 49.98 ± 21.82 years (42 males, 11 females). Mean follow up duration was 48.9 months. Δ C1-C2 angle is significantly correlated with ΔC2-C7 angle (Group A, p = 0.004; Group B, p = 0.015) but not with ΔC0-C1 angle (Group A, p = 0.315; Group B, p = 0.938). Though significant improvement in the clinical parameters (VAS/NDI) has been noted in both groups, Group A showed a greater improvement in VAS scores [Group A, (p < 0.001); Group B, (p < 0.023)].Conclusions: The sub-axial sagittal profile was strongly correlated with the ΔC1-C2 angle in both groups. Group B showed greater changes in sagittal parameters after Harms fixation and Group A showed greater improvement in long-term functional outcomes. The final functional outcomes were not related to the initial or final radiological sagittal profile in both groups.

Relationship between the atlantodental interval and T1 slope after atlantoaxial fusion in patients with rheumatoid arthritis

BACKGROUND

Atlantoaxial fusion has been widely used for the treatment of atlantoaxial instability (AAI). However, atlantoaxial fusion sacrifices the motion of atlantoaxial articulation, and postoperative loss of cervical lordosis and aggravation of cervical kyphosis are observed. We investigated various factors under the hypothesis that the atlantodental interval (ADI) and T1 slope may be associated with sagittal alignment after atlantoaxial fusion in patients with rheumatoid arthritis (RA).

METHODS

We retrospectively investigated 64 patients with RA who underwent atlantoaxial fusion due to AAI. Radiological factors, including the ADI, T1 slope, Oc-C2 angle, cervical sagittal vertical axis, and C2-C7 angle, were measured before and after surgery.

RESULTS

The various factors associated with atlantoaxial fusion before and after surgery were compared according to the upper and lower preoperative ADIs. There was a significant difference in the T1 slope 1 year after surgery (p = 0.044) among the patients with lower preoperative ADI values. The multivariate logistic regression analysis showed that the preoperative ADI (> 7.92 mm) defined in the receiver-operating characteristic curve analysis was an independent predictive factor for the increase in the T1 slope 1 year after atlantoaxial fusion (odds ratio, 4.59; 95% confidence interval, 1.34-15.73; p = 0.015).

CONCLUSION

We found an association between the preoperative ADI and difference in the T1 slope after atlantoaxial fusion in the patients with RA. A preoperative ADI (> 7.92 mm) was an independent predictor for the increase in the T1 slope after atlantoaxial fusion. Therefore, performing surgical treatment when the ADI is low would lead to better cervical sagittal alignment.

Risk factor analysis of postoperative kyphotic change in subaxial cervical alignment after upper cervical fixation

OBJECTIVE

Little is known about the risk factors for postoperative subaxial cervical kyphosis following craniovertebral junction (CVJ) fixation. The object of this study was to evaluate postoperative changes in cervical alignment and to identify the risk factors for postoperative kyphotic change in the subaxial cervical spine after CVJ fixation.

METHODS

One hundred fifteen patients were retrospectively analyzed for postoperative subaxial kyphosis after CVJ fixation. Relations between subaxial kyphosis and radiological risk factors, including segmental angles and ranges of motion (ROMs) at C0-1, C1-2, and C2-7, and clinical factors, such as age, sex, etiology, occipital fixation, extensor muscle resection at C2, additional C1-2 posterior wiring, and subaxial laminoplasty, were investigated. Univariate and multivariate logistic regression analyses were conducted to identify the risk factors for postoperative kyphotic changes in the subaxial cervical spine.

RESULTS

The C2-7 angle change was more than -10° in 30 (26.1%) of the 115 patients. Risk factor analysis showed CVJ fixation combined with subaxial laminoplasty (OR 9.336, 95% CI 1.484-58.734, p = 0.017) and a small ROM at the C0-1 segment (OR 0.836, 95% CI 0.757-0.923, p < 0.01) were related to postoperative subaxial kyphotic change. On the other hand, age, sex, resection of the C2 extensor muscle, rheumatoid arthritis, additional C1-2 posterior wiring, and postoperative segmental angles were not risk factors for postoperative subaxial kyphosis.

CONCLUSIONS

Subaxial alignment change is not uncommon after CVJ fixation. Muscle detachment at the C2 spinous process was not a risk factor of kyphotic change. The study findings suggest that a small ROM at the C0-1 segment with or without occipital fixation and combined subaxial laminoplasty are risk factors for subaxial kyphotic change.

Retrospective analysis of surgical outcomes for atlantoaxial subluxation

Background

Atlantoaxial subluxation (AAS) is characterized by excessive movement at the junction between the atlas (C1) and axis (C2) as a result of either a bony or ligamentous abnormality. Surgical intervention is a therapeutic choice for AAS. In addition to C1 laminectomy (LAM), surgical fixation for subluxation or instability is performed by various techniques. While surgical treatment options for AAS have increased, the outcomes of different surgical techniques remain unclear.

Methods

The authors conducted a retrospective analysis of the outcomes of 30 consecutive spinal surgeries performed for AAS patients, C1 LAM in 11 cases and C1/2 fixation in 19 cases. We investigated the correlation between the clinical outcomes and the surgical methods. We also examined the factors related to poor outcomes (the recovery rate of the Japanese Orthopedic Association score for cervical myelopathy < 40%) following AAS surgeries.

Results

From a surgical method perspective, the patients in the C1 LAM group were older than those in the C1/2 fixation group (74.6 years vs 68.0 years), and the average recovery rate from the preoperative status was as follows: the C1 LAM group, 39.4%; the C1/2 fixation group, 49.8%. The C-JOA score was significantly improved after surgery in the C1/2 fixation group (from 9.8 to 13.1 points). The fixation technique seemed to successfully reduce C1/2 displacement. Each group exhibited a slight increase in the C1/2 angle and a decrease in the C2–7 angles after the operation. A higher preoperative atlantodental interval (ADI) was associated with good outcomes after the C1/2 fixation. The postoperative ADI was significantly reduced from 8.6 mm to 3.8 mm in the good outcome group after fixation. Patients with higher C1/2 angle showed good outcomes after C1 LAM. Despite the good neurological improvement, the C1/2 fixation method showed higher complication rates compared with C1 LAM method.

Conclusions

The results of this study showed that the C1/2 fixation technique exhibited effectiveness in terms of neurological recovery. However, there was a high complication rate in surgeries for AAS, especially in the C1/2 fixation. C1 LAM would be considered for high-risk AAS cases such as elderly patients with multiple comorbidities.

Influence of Atlantoaxial Fusion on Sagittal Alignment of the Occipitocervical and Subaxial spines in Os Odontoideum with Atlantoaxial Instability

Study Design

Retrospective case analysis.

Purpose

We hypothesized that larger the C1–C2 fusion angle, greater the severity of the sagittal malalignment of C0–C1 and C2–C7.

Overview of Literature

In our experience, instances of sagittal malalignment occur at C0–C1 and C2–C7 following atlantoaxial fusion in patients with Os odontoideum (OO).

Methods

We assessed 21 patients who achieved solid atlantoaxial fusion for reducible atlantoaxial instability secondary to OO. The mean patient age at the time of the operation was 42.8 years, and the mean follow-up duration was 4.9 years. Radiographic parameters were preoperatively measured and at the final follow-up. The patients were divided into two groups (A and B) depending on the C1–C2 fusion angle. In group A (n=11), the C1–C2 fusion angle was ≥22°, whereas in group B, it was <22°. The differences in the radiographic parameters of the two groups were evaluated.

Results

At the final follow-up, the C1–C2 angle was increased. However, this increase was not statistically significant (18° vs. 22°, p=0.924). The C0–C1 angle (10° vs. 5°, p<0.05) and C2–C7 angle (22° vs. 13°, p<0.05) significantly decreased. The final C1–C2 angle was negatively correlated with the final C0–C1 and C2–C7 angles. The final C0–C1 angle (4° vs. 6°, p<0.05) and C2–C7 angle (8° vs. 20°, p<0.05) were smaller in group A than in group B. After atlantoaxial fusion, the C0–C1 range of motion (ROM; 17° vs. 9°, p<0.05) and the C2–C7 ROM (39° vs. 31°, p<0.05) were significantly decreased.

Conclusions

We found a negative association between the sagittal alignment of C0–C1 and C2–C7 after atlantoaxial fusion and the C1–C2 fusion angle along with decreased ROM. Therefore, overcorrection of C1–C2 kyphosis should be avoided to maintain good physiologic cervical sagittal alignment.

Postoperative Cervical Sagittal Realignment Improves Patient-Reported Outcomes in Chronic Atlantoaxial Anterior Dislocation

BACKGROUND

Chronic atlantoaxial anterior dislocation (AAD) not only results in myelopathy, but dislocation-related kyphosis also results in cervical malalignment, which permanently affects neck function and patient-reported outcomes (PROs).

OBJECTIVE

To investigate the effect of kyphotic correction on realigning cervical spine and independent cervical alignment parameters, which may be correlated with an improvement of PROs.

METHODS

The study included 21 patients with chronic AAD-related kyphosis who underwent C1-2 reduction and correction surgery. Radiographic parameters were measured to assess cervical realignment preoperatively and postoperatively. Neck disability index (NDI), short form 12 physical component summary (SF-12 PCS), and Japanese Orthopaedic Association (JOA) scores were recorded to reveal changes in PROs. The independent parameters correlated with the improvements of PROs were analyzed.

RESULTS

Of the radiographic parameters, the C1-2 Cobb angle, the C2-7 Cobb angle, thoracic inlet angle, cervical tilt, and T1 slope were significantly changed from -4.0° ± 16.2°, -29.2° ± 11.2°, 73.1° ± 13.3°, 30.4° ± 8.5°, and 29.1° ± 8.8° preoperatively to -13.5° ± 8.1° (P = .005), -18.0° ± 12.0° (P < .001), 67.1° ± 11.6° (P = .042), 23.1° ± 10.3° (P = .007), and 24.0° ± 7.0° (P = .011) at last follow-up, respectively. NDI, JOA, and SF-12 PCS scores were significantly improved postoperatively. The C1-2 Cobb angle was an independent parameter correlated with the improvements in SF-12 PCS, NDI, and JOA scores.

CONCLUSION

Correction and reduction surgery can realign cervical spine in chronic AAD patients. The C1-2 Cobb angle was an independent parameter correlated with the improvements of PROs.

Radiographic and clinical outcomes of C1-C2 intra-articular screw fixation in patients with atlantoaxial subluxation

Background

The Magerl and Goel-Harms techniques have been reported to produce excellent treatment outcomes in cases of atlantoaxial subluxation, but they also carry a risk of vertebral artery injuries. In order to completely prevent such injuries, we developed a surgical procedure, involving bone grafting between the C1 posterior arch and C2 lamina with clamp- or hook-and-rod-based fixation combined with the insertion of an interference screw into the posterior atlantoaxial joint.

Methods

This was a retrospective single-center study. The subjects were 58 patients in whom atlantoaxial subluxation was treated with the abovementioned procedure after 1995 (33 patients with rheumatoid arthritis (RA group) and 25 patients without rheumatoid arthritis (non-RA group)). The clinical outcomes and imaging findings of anterior subluxation at ≥ 2 years after surgery were compared between the RA and non-RA groups.

Results

No vertebral artery injuries occurred during surgery. Seven and two patients died during the follow-up period in the RA and non-RA groups, respectively, but none of these deaths were associated with surgery. At ≥ 2 years after surgery, the visual analogue scale score, Japanese Orthopaedic Association score, and Ranawat classification had significantly improved in both groups (p < 0.001). Radiologically, bone fusion was noted in all patients. Significant changes in the atlas-dens interval (ADI) were seen immediately after surgery in both groups (p < 0.001). In the non-RA group, significant changes in the corrected atlantoaxial height were observed immediately after surgery (p < 0.01), and loss of correction was seen at the final follow-up, but it was not significant (p = 0.1965). No significant changes were noted in any other parameter. Regarding the postoperative alignment of the cervical spine, lordosis tended to decrease, but additional surgery was only performed in one patient, who had developmental stenosis at the mid-lower level and belonged to the RA group. No reoperations due to fused adjacent segmental disease or exacerbated curvature were required.

Conclusion

In the present study, no vertebral artery injuries occurred during surgery, and no major perioperative complications developed. Favorable clinical outcomes were observed at ≥ 2 postoperative years although the patients’ diseases varied. This procedure produced superior outcomes, especially in terms of spinal correction and the maintenance of the ADI.

Incidence and risk factors for adjacent segment degeneration following occipitoaxial fusion for atlantoaxial instability in non-rheumatoid arthritis

PURPOSE

To investigate the incidence and risk factors for adjacent segment degeneration (ASD) following occipitoaxial fusion (OAF) for atlantoaxial instability (AAI) in non-rheumatoid arthritis (RA).

METHODS

The study group comprised 41 patients without RA who underwent OAF due to AAI. Fifteen patients with postoperative ASD after OAF were classified as the ASD group, and the other 26 patients without postoperative ASD were included in the non-ASD group. There were 12 men and 3 women with a mean age of 43.52 years in the ASD group, and 19 men and 7 women with a mean age of 45.31 years in the non-ASD group. The mean follow-up period was 6.1 and 5.9 years in the ASD group and non-ASD group, respectively. Clinical outcomes and plain radiographs were retrospectively reviewed and compared between the two groups.

RESULTS

The difference between pre- and postoperative O-C2 angles in the non-ASD group was significantly greater than that in the ASD group. The C2-7 angles changed significantly between the pre- and postoperative periods. It was suggested that the small O-C2 angle and large C2-7 angle observed in the early postoperative period were risk factors for the development of ASD. We also demonstrated a high incidence of subaxial subluxation (SAS) and swan neck deformity in the ASD group (27 versus 3.8% and 20 versus 0%, respectively).

CONCLUSION

Under-correction of the O-C2 angle is likely to cause malalignment of the cervical spine, resulting in the development of postoperative ASD, SAS, and swan neck deformity.

Surgical overreduction and hyperlordotic fusion of C1-C2 joint are associated with cervical sagittal malalignment

INTRODUCTION

Previous studies have shown that hyperlordotic C1-C2 fusion was related to postoperative subaxial kyphosis. However, most of the patients in these studies were complicated with rheumatoid arthritis (RA). Moreover, no studies have specifically evaluated the relationship between C1-C2 fusion angle and cervical sagittal vertical axis (cSVA), T1 slope or cranial tilt (CRT) after posterior C1-C2 fusion. This study aimed to investigate the cervical sagittal alignment in non-RA patients following posterior C1-C2 fusion and the correlation between C1-C2 fusion angle and postoperative cervical sagittal alignment.

MATERIALS AND METHODS

From August 2004 to December 2015, twenty-eight consecutive patients with an average age of 39.2 years (range 6-70 years) who underwent posterior C1-C2 fusion from a single institution were enrolled. The mean follow-up period was 30.7 months (range 12-77 months). Angles of Oc-C1, C1-C2, C2-C3 and C2-C7, cSVA, T1 slope and CRT were measured in lateral cervical radiographs in neutral position before surgery and at the final follow-up.

RESULTS

C1-C2 angle significantly increased from 13.6° ± 12.4° to 22.0° ± 8.1° at the final follow-up (P < 0.001). A significant decrease was found both in Oc-C1 and C2-C7 angles from pre-operation to the final follow-up (P < 0.001 and P = 0.011, respectively). Moreover, cSVA and CRT dramatically increased from pre-operation to the final follow-up (P < 0.001). C1-C2 fusion angle was significantly associated with Oc-C1, C2-C7 angle, cSVA and CRT at the final follow-up. A significant correlation was also observed between postoperative change of C1-C2 angle and that of Oc-C1, C2-C7 angle, cSVA and CRT.

CONCLUSIONS

Apart from decreased subaxial lordosis, posterior C1-C2 fusion in hyperextension may also lead to kyphotic change of atlanto-occipital alignment and increased tilting forward of the cervical spine. Therefore, intraoperative overreduction of C1-C2 angle and hyperlordotic C1-C2 fusion should be avoided to maintain the physiologic cervical sagittal alignment.

Treatment of atlanto-axial subluxation secondary to rheumatoid arthritis by short segment stabilization with polyaxial screws

OBJECTIVE

The main aim of this study was to analyse the compex clinical and radiographic findings in a group of RA patients with atlanto-axial slip (AAS) treated with free-hand short C1 lateral mass and C2 trans-pedicular screw fixation. The surgical technique used and the pathology treated were the same in all patients, producing a very homogeneous cohort of patients This allowed the study and measurement of radiographic parameters and fusion process.

METHODS

Twenty-nine patients (21 female, 8 male, mean age 54.9 years, duration of RA 17.3 years) with AAS and without CS were treated by short C1/2 fixation. Mean follow-up was 4.5 years. Pain intensity was monitored using VAS. Radiographic assessment consisted of lateral cervical radiographs in neutral and dynamic views, MR and CT of the cervical spine. The AADI, PADI, AAA, sub-axial cervical Cobb angle and canal-clivus angle (CCA) were measured pre-operatively and during the follow-up.

RESULTS

Significant malposition was recorded in 4 (3.4%) out of 116 inserted screws. AADI, PADI, AAA and CCA values changed significantly after surgery and remained stable during follow-up. The Cobb C angle value showed no significant change after surgery. There was a significant decrease of the VAS after the surgery. Fusion or a stable situation was achieved in all patients at 2-year follow-up. Pannus regression was observed in the vast majority of patients; only in two cases was rheumatic tissue detected on MR at 2 years post-operatively.

CONCLUSION

C1 lateral mass and C2 trans-pedicular fixation with polyaxial screws followed by an autograft between C1 and C2 lamina allowed, with an acceptable complication rate and favourable clinical results, adequate slip reposition, introduction of optimal sagittal alignment in terms of the final AAA with no radiographic consequences for the sub-axial cervical spine and assurance of long-term stability.

A Retrospective Analysis of Subaxial Subluxation After Atlanto-axial Arthrodesis in Patients With Rheumatoid Arthritis Based on Annual Radiographs Obtained for 5 Years

STUDY DESIGN

Retrospective study.

OBJECTIVE

The purpose of this study was to investigate the incidence of subaxial subluxation (SAS) after atlanto-axial arthrodesis in rheumatoid arthritis (RA) patients using annual radiographs obtained for 5 years and clarify the characteristics of SAS after surgery.

SUMMARY OF BACKGROUND DATA

Rheumatoid SAS has been reported to occur after atlanto-axial arthrodesis. Many authors have noted that excessive correction of the atlanto-axial angle (AAA) results in a decrease in subaxial lordosis, thereby inducing SAS; therefore, we paid special attention to acquiring a suitable AAA in patients with atlanto-axial arthrodesis.

METHODS

Twenty-five patients with AAS treated with surgery were reviewed. In all patients, lateral cervical radiographs were obtained in neutral, maximal flexion, and maximal extension positions every year for 5 years after surgery. We investigated the occurrence and progression of SAS using these annual radiographs.

RESULTS

There were no significant differences between preoperative and postoperative value in AAA and subaxial angle (SAA), respectively. Before surgery, SAS was found in 10 patients. The occurrence and progression of SAS after surgery was found in 12 cases (SAS P+ group). There were no significant differences in age, sex, or the duration of RA between the SAS P+ group and the remaining 13 cases. We also found no differences in the preoperative and postoperative AAA and SAA between the 2 groups.

CONCLUSIONS

Although SAA was maintained after atlanto-axial arthrodesis in RA-AAS patients, 12 of 25 patients (48%) with AAS developed SAS after atlanto-axial fusion. Further surgery was not needed for SAS up to 5 years after the initial surgery. We did not find any relationship between the occurrence of SAS and the AAA and SAA before and after surgery. Therefore, our findings suggest that proper reduction of AAA in patients with atlanto-axial arthrodesis does not affect the occurrence of SAS at 5 years after surgery.

Distal Junctional Disease after Occipitothoracic Fusion for Rheumatoid Cervical Disorders: Correlation with Cervical Spine Sagittal Alignment

Study Design Retrospective radiographic study. Objective We have performed occipitothoracic (OT) fusion for severe rheumatoid cervical disorders since 1991. In our previous study, we reported that the distal junctional disease occurred in patients with fusion of O-T4 or longer due to increased mechanical stress. The present study further evaluated the association between the distal junctional disease and the cervical spine sagittal alignment. Methods Among 60 consecutive OT fusion cases between 1991 and 2010, 24 patients who underwent O-T5 fusion were enrolled in this study. The patients were grouped based on whether they developed postoperative distal junctional disease (group F) or not (group N). We measured pre- and postoperative O-C2, C2-C7, and O-C7 angles and evaluated the association between these values and the occurrence of distal junctional disease. Results Seven (29%) of 24 patients developed adjacent-level vertebral fractures as distal junctional disease. In group F, the mean pre- and postoperative O-C2, C2-C7, and O-C7 angles were 12.1 and 16.8, 7.2 and 11.2, and 19.4 and 27.9 degrees, respectively. In group N, the mean pre- and postoperative O-C2, C2-C7, and O-C7 angles were 15.9 and 15.0, 4.9 and 5.8, and 21.0 and 20.9 degrees, respectively. There were no significant differences between the two groups. The difference in the O-C7 angle (postoperative angle - preoperative angle) in group F was significantly larger than that in group N (p = 0.04). Conclusion Excessive correction of the O-C7 angle (hyperlordotic alignment) is likely to cause postoperative distal junctional disease following the OT fusion.

Factors influencing feasibility of direct posterior reduction in irreducible traumatic atlantoaxial dislocation secondary to isolated odontoid fracture

INTRODUCTION

Direct posterior reduction by intraoperative manipulation of joints for irreducible traumatic atlantoaxial dislocation (IrTAAD) has gained acceptance in the recent past. However, factors determining its feasibility have not been elucidated. Our study aims to examine the clinico-radiological factors predicting feasibility of direct posterior reduction in IrTAAD secondary to isolated odontoid fracture, in an attempt to differentiate the "truly irreducible" from those "deemed irreducible."

MATERIALS AND METHODS

The onset and progression of neck pain and myelopathy was studied in 6 patients of IrTAAD with fracture odontoid, which failed to reduce despite traction. The dynamic X-rays and computed tomography (CT) scans of craniovertebral junction, along with the vertebral artery angiogram were studied to look for the slightest mobility, interface of fractured fragments, malunion, callous, and relationship of the C1-2 facets and vertebral artery.

RESULTS

All 6 patients had progressive worsening of neck pain. Three patients had progressive myelopathy. Three patients presented 6 months after trauma. Radiology showed type-II fracture with IrTAAD (anterolisthesis in 5 and retrolisthesis with lateral dislocation in 1) and locked facets in all. X-rays showed doubtful callous formation in 3 patients and CT confirmed non-union. Three patients showed angular movement on dynamic X-rays despite irreducibility and locked facets. Angiogram showed thrombosis of vertebral artery in one patient. Intraoperative reduction could be achieved in all 6 patients with good clinico-radiological outcome.

CONCLUSION

Worsening pain, progression of myelopathy, some movement on dynamic X-rays, a malunion ruled out on CT scan, and the presence of locked facets make direct posterior reduction feasible in patients with IrTAAD. The difficulty increases in remote fractures due to fibrosis around the dislocated joints. The role of the CT angiogram, in defining the relationship of Vertebral artery (VA) to the dislocated facets, and in determining the extent of VA injury, is vital. Preoperative detection of VA injury reduces the chance of intraoperative reduction, especially if only unilateral joint approach is planned.

Posterior fixation for atlantoaxial subluxation in a case with complex anomaly of persistent first intersegmental artery and assimilation in the C1 vertebra

We report a very rare case of atlantoaxial subluxation (AAS) with persistent first intersegmental artery (PFIA) and assimilation in the atlas (C1) vertebra. This case demonstrates the difficulty of deciding on a surgical strategy for complex anomalies. A 63-year-old man presented with gait disturbance, neck pain, and severe dysesthesia in his left arm. Past history included a whiplash injury. Dynamic X-ray studies demonstrated an irreducible AAS and assimilation of C1. This subluxation was slightly deteriorated in an extended position. A three-dimensional computed tomography angiography (3DCTA) indicated that the PFIA was located on the left side. We performed a C1 posterior arch resection and C1 lateral mass–axis pedicle screw (C1LM–C2PS) fixation using the modified technique of skewering the occipital condyle and C1 lateral mass. The patient had no postoperative morbidity and his symptoms disappeared immediately after operation. Complex anomalies cause difficulty in determining surgical strategy although several surgical methods for simple craniovertebral junction anomaly have been reported. To avoid significant morbidities associated with vertebral artery injury, surgical strategies for these complex conditions are discussed. The modified technique of a C1 lateral mass screw penetrating the occipital condyle is a viable treatment option.

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

PURPOSE

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.

METHODS

Forty-one patients, consisting of 29 females and 12 males, with AAS treated by surgery were reviewed. The average patient age at surgery was 61.0 years, and the average follow-up period was 4.0 years. 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.

RESULTS

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.

CONCLUSIONS

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.

Is inclusion of the occiput necessary in fusion for C1-2 instability in rheumatoid arthritis?

OBJECT

The atlantoaxial joint is the location most and earliest affected in patients with rheumatoid arthritis (RA). In longstanding disease, ligamentous and osseous destruction can progress and involve all cervical segments. If surgical intervention is necessary, some prefer, to be safe, undertaking fusion to the occiput, whereas others advocate 1-level fusion of C1-2. Sparing the occiput (Oc)-C1 segment would allow retention of a considerable amount of physiological range of motion and seems beneficial against subaxial overload. Previous clinical studies on this topic have provided only nonspecific data after short-term follow-up, rendering a segment-sparing approach questionable. The purpose of the present investigation was to assess long-term progression of inflammatory or degenerative destruction in the Oc-C1 segment after isolated C1-2 fusion for RA.

METHODS

In a series of 113 consecutive patients with RA-related destruction restricted to the craniocervical junction, 14 individuals underwent Oc-C2 fusion and 99 underwent surgery exclusively at the C1-2 level. After a mean follow-up period of 9.4 years (range 4.9-14.7 years), 46 patients were available for clinical and radiographic examination, including CT imaging.

RESULTS

None of the 46 patients needed additional surgery to extend the fusion to the occiput. Despite marked deterioration in the subaxial cervical spine, in general there were little or no changes in the atlantooccipital region. All but one patient presented with bony fusion of the fixed C1-2 level at follow-up.

CONCLUSIONS

The results of this investigation suggest that if the Oc-C1 joint is free of osseous destructions on conventional radiographs and free of abnormalities on MRI scans at the time of surgery (for transarticular fixation and fusion of C1-2), there is a very low risk for relevant destruction in the following 5-14 years. Thus, no prophylactic oligosegmental approach, but rather a segment-sparing monosegmental approach, is preferred, even in patients with high inflammatory levels.

Atlantoaxial fusion with transarticular screws: meta-analysis and review of the literature

OBJECTIVE

To review published series describing C1-2 posterior instrumented fusions and summarize clinical and radiographic outcomes of patients treated with transarticular screw (TAS) fixation.

METHODS

Online databases were searched for English-language articles published between 1986 and April 2011 describing posterior atlantoaxial instrumentation with C1-2 TAS fixation. There were 45 studies including 2073 patients treated with TAS that fulfilled inclusion criteria. Meta-analysis techniques were used to calculate outcomes.

RESULTS

All studies provided class III evidence. The 30-day perioperative mortality rate was 0.8%, and the incidence of neurologic injury was 0.2%. The incidence of clinically significant malpositioned screws was 7.1% (confidence interval [CI], 5.7%-8.8%), the incidence of vertebral artery injury was 3.1% (CI, 2.3%-4.3%), and the rate of fusion with the TAS technique was 94.6% (CI, 92.6%-96.1%).

CONCLUSIONS

TAS fixation is a safe and effective treatment option for C1-2 instability with high rates of fusion (approximately 95%). Screw malposition and vertebral artery injury occurred in approximately 5% of patients. The successful insertion of TAS requires a thorough knowledge of atlantoaxial anatomy.

Relation between alignments of upper and subaxial cervical spine: a radiological study

OBJECTIVE

To reveal the relation between alignments of upper and subaxial cervical spine and deduce the optimal atlantoaxial fusion angle by a radiological study.

METHODS

414 asymptomatic volunteers (213 males, 201 females) underwent cervical lateral radiographs in neutral position. The Oc-C2 angle, C1-C2 angle and C2-C7 angle were measured. Relations among these three angles and relations between angles and age were analyzed.

RESULTS

The mean Oc-C2 angle was 16.3° ± 7.0° in females, significantly larger than 14.9° ± 6.5° in males. The mean C1-C2 angles were 28.2° ± 4.0° in females and 26.4° ± 4.6° in males, and C2-C7 angles were 12.7° ± 6.6° and 16.3° ± 7.3°, correspondingly. The mean C1-C2 angle in females was significantly larger than that in males, while C2-C7 angle smaller than that in males. The C2-C7 angle correlated significantly not only with C1-C2 angle but also with Oc-C2 angle. And correlation between C1-C2 angle and C2-C7 angle was stronger than that between Oc-C2 angle and C2-C7 angle. There were also significant positive correlations between C1-C2 and Oc-C2 angles. Oc-C2 angle, C1-C2 angle, and C2-C7 angle correlated significantly with age in both sexes.

CONCLUSIONS

There were negative correlations between C1-C2 angle and C2-C7 angle as well as between Oc-C2 angle and C2-C7 angle, and the former correlation was stronger. C1-C2 fixation angle was the key to regulate postoperative subaxial alignment in atlantoaxial arthrodesis. The optimal atlantoaxial fusion angle may be between 25° and 30°.

Risk factors for development of subaxial subluxations following atlantoaxial arthrodesis for atlantoaxial subluxations in rheumatoid arthritis

STUDY DESIGN

Retrospective radiographic/imaging study.

OBJECTIVE

To evaluate preoperative and sequential postoperative radiographs following C1-C2 arthrodesis for atlantoaxial subluxation in patients with rheumatoid arthritis (RA) to determine risk factors for the development of subaxial subluxations (SAS).

SUMMARY OF BACKGROUND DATA

The development of SAS has often been observed after C1-C2 arthrodesis. However, there have been no previous reports on the correlation between radiographic parameters and the incidence of postoperative SAS.

METHODS

The study group comprised of 58 patients with RA who underwent C1-C2 arthrodesis due to atlantoaxial subluxation. There were 5 men and 53 women with a mean age of 55.8 years. The mean follow-up period was 137 months. Nineteen patients with a postoperative SAS after C1-C2 arthrodesis were classified as the SAS+ group. Other 39 patients without a postoperative SAS were included in the SAS- group. Clinical outcomes and plain radiographs were reviewed retrospectively and compared between the 2 groups.

RESULTS

The difference between pre- and postoperative atlantoaxial (AA) angles in the SAS+ group was significantly greater than those in the SAS- group (P = 0.039). The C2-C7 angles changed significantly between pre- and postoperative periods in the SAS+ group (P = 0.039), but not in the SAS- group (P = 0.897). It was suggested that a large AA angle and a small C2-C7 angle observed at the early postoperative period were the risk factors for the development of SAS. We also demonstrated that a high incidence of the C3-C4 SAS resulted from excessive bone fusion at the C2-C3.

CONCLUSION

Excessive correction of AA angle is likely to cause loss of cervical lordosis, resulting in the development of postoperative SAS. In addition, extensive bony union at C2-C3 following C1-C2 arthrodesis frequently leads to the development of extensive SAS at the C3-C4.

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.

Subaxial subluxation after atlantoaxial transarticular screw fixation in rheumatoid patients

The most common cervical abnormality associated with rheumatoid arthritis (RA) is atlantoaxial subluxation, and atlantoaxial transarticular screw fixation has proved to be one of the most reliable, stable fixation techniques for treating atlantoaxial subluxation. Following C1-C2 fixation, however, subaxial subluxation reportedly can bring about neurological deterioration and require secondary operative interventions. Rheumatoid patients appear to have a higher risk, but there has been no systematic comparison between rheumatoid and non-rheumatoid patients. Contributing radiological factors to the subluxation have also not been evaluated. The objective of this study was to evaluate subaxial subluxation after atlantoaxial transarticular screw fixation in patients with and without RA and to find contributing factors. Forty-three patients who submitted to atlantoaxial transarticular screw fixation without any concomitant operation were followed up for more than 1 year. Subaxial subluxation and related radiological factors were evaluated by functional X-ray measurements. Statistical analyses showed that aggravations of subluxation of 2.5 mm or greater were more likely to occur in RA patients than in non-RA patients over an average of 4.2 years of follow-up, and postoperative subluxation occurred in the anterior direction in the upper cervical spine. X-ray evaluations revealed that such patients had a significantly smaller postoperative C2-C7 angle, and that the postoperative AA angle correlated negatively with this. Furthermore, anterior subluxation aggravation was significantly correlated with the perioperative atlantoaxial and C2-C7 angle changes, and these two changes were strongly correlated to each other. In conclusion, after atlantoaxial transarticular screw fixation, rheumatoid patients have a greater risk of developing subaxial subluxations. The increase of the atlantoaxial angel at the operation can lead to a decrease in the C2-C7 angle, followed by anterior subluxation of the upper cervical spine and possibly neurological deterioration.

Atlantoaxial transarticular screw fixation with posterior wiring using polyethylene cable: facet fusion despite posterior graft resorption in rheumatoid patients

STUDY DESIGN

A comparative retrospective study on the posterior graft union and the facet fusion in atlantoaxial transarticular screw fixation.

OBJECTIVE

To evaluate the posterior graft union and the facet fusion in atlantoaxial transarticular screw fixation when a polyethylene (PE) cable was used in rheumatoid and nonrheumatoid patients.

SUMMARY OF BACKGROUND DATA

In atlantoaxial transarticular screw fixation, metal wires or cables for posterior bone graft fixation can cause intraoperative or delayed spinal cord compression. PE cables do not have the risk, but there has been no comparative report. Also, a precise evaluation on the posterior graft union and the facet fusion has not been reported.

METHODS

Thirty-eight patients who submitted to atlantoaxial transarticular screw fixation and posterior bone graft without any concomitant operation were followed up for more than 2 years. The posterior graft union and the facet fusion were evaluated by functional radiographs and computed tomography scans.

RESULTS

Seven patients showed the posterior graft nonunion. All of them were rheumatoid patients and received PE cable wiring for posterior internal fixation. However, 5 of the 7 cases presented stable C1-C2 with the facet fusion demonstrated by functional radiographs and computed tomography scans, achieving an overall fusion rate of 95%.

CONCLUSION

In atlantoaxial transarticular screw fixation, the use of PE cable and rheumatoid background are 2 of the unfavorable factors for the posterior graft union. However, atlantoaxial transarticular screws can bring the facet fusion despite the posterior graft failure in such cases.