Impact of the occiput and external acoustic meatus to axis angle on dysphagia in patients suffering from anterior atlantoaxial subluxation after occipitocervical fusion

Preoperative radiological indicators for prediction of difficult laryngoscopy in patients with atlantoaxial dislocation

Background

Difficult airway remains a great challenge in patients with atlantoaxial dislocation (AAD). Preoperative evaluation and reliable prediction are required to facilitate the airway management. We aimed to screen out reliable radiological indicators for prediction of difficult laryngoscopy in patients with AAD.

Methods

A retrospective nested case-control study within a single center longitudinal AAD cohort was conducted to investigate the radiological indicators. All the patients with difficult laryngoscopy from 2010 to 2021 were enrolled as the difficult laryngoscopy group. Others in the cohort without difficult laryngoscopy were randomly selected as the non-difficult laryngoscopy group by individually matching with the same gender, same surgery year, and similar age (±5 years) at a ratio of 6:1. Radiological data on preoperative lateral X-ray images between the two groups were compared. Bivariate logistic regression model was applied to screen out the independent predictive indicators and calculate the odds ratios of indicators associated with difficult laryngoscopy. Receiver operating characteristic curve and area under the curve (AUC) were used to describe the discrimination ability of indicators.

Results

A total of 154 patients were finally analyzed in this study. Twenty-two patients with difficult laryngoscopy and matched with 132 controls. Four radiological parameters showed significant difference between the two groups. Among which, ΔC1C2D (the difference of the distance between atlas and axis in the neutral and extension position), owned the largest AUC.

Conclusions

ΔC1C2D could be a valuable radiologic predictor for difficult laryngoscopy in patients with AAD.

Intraoperative occipital to C2 angle and external acoustic meatus-to-axis angular measurements for optimizing alignment during posterior fossa decompression and occipitocervical fusion for complex Chiari malformation

Background

Excess flexion or extension during occipitocervical fusion (OCF) can lead to postoperative complications, such as dysphagia, respiratory problems, line of sight issues, and neck pain, but posterior fossa decompression (PFD) and OCF require different positions that require intraoperative manipulation.

Objective

The objective of this study was to describe quantitative fluoroscopic morphometrics in Chiari malformation (CM) patients with symptoms of craniocervical instability (CCI) and demonstrate the intraoperative application of these measurements to achieve neutral craniocervical alignment while leveraging a single axis of motion with the Mayfield head clamp locking mechanism.

Methods

A retrospective cohort study of patients with CM 1 and 1.5 and features of CCI who underwent PFD and OCF at a single-center institution from March 2015 to October 2020 was performed. Patient demographics, preoperative presentation, radiographic morphometrics, operative details, complications, and clinical outcomes were analyzed.

Results

A total of 39 patients met the inclusion criteria, of which 37 patients (94.9%) did not require additional revision surgery after PFD and OCF. In this nonrevision cohort, preoperative to postoperative occipital to C2 angle (O-C2a) (13.5° ± 10.4° vs. 17.5° ± 10.1°, P = 0.047) and narrowest oropharyngeal airway space (nPAS) (10.9 ± 3.4 mm vs. 13.1 ± 4.8 mm, P = 0.007) increased significantly. These measurements were decreased in the two patients who required revision surgery due to postoperative dysphagia (mean difference - 16.6°° in O C2a and 12.8°° in occipital and external acoustic meatus to axis angle). Based on these results, these fluoroscopic morphometrics are intraoperatively assessed, utilizing a locking Mayfield head clamp repositioning maneuver to optimize craniocervical alignment prior to rod placement from the occipital plate to cervical screws.

Conclusion

Establishing a preoperative baseline of reliable fluoroscopic morphometrics can guide surgeons intraoperatively in appropriate patient realignment during combined PFD and OCF, and may prevent postoperative complications.

Radiographic measurements for the prediction of dysphagia after occipitocervical fusion: a systematic review

BACKGROUND

Occipitocervical fusion (OCF) is a procedure performed for multiple upper cervical pathologies. A common postprocedural complication of OCF is dysphagia, which has been linked to the narrowing of the pharyngeal space due to fixation in a hyper-flexed angle. Postoperative dysphagia is linked to reduced quality of life, prolonged hospital stay, aspiration pneumonia, and increased mortality. This has led to investigations of the association between sagittal radiographic angles and dysphagia following OCF.

METHODS

A systematic review of the literature was performed to explore the current evidence regarding cervical sagittal radiographic measurements and dysphagia following OCF. A search strategy was carried out using the PubMed, Embase, and Web of Science databases from their dates of inception until August 2022. Only original English-language studies were considered. Moreover, studies had to include the correlation between dysphagia and at least one radiographic measurement in the sagittal plane.

RESULTS

The search and subsequent selection process yielded eight studies that were included in the final review, totaling 329 patients in whom dysphagia had been assessed and graded. The dysphagia score by Bazaz et al. (Spine 27, 22:2453-2458, 2002) was used most often. The pooled incidence of dysphagia, in the early postoperative period, was estimated at 26.4%. At long-term follow-up (range: 17-72 months), about one-third of patients experienced resolution of symptoms, which resulted in a long-term post-OCF dysphagia incidence of 16.5%. Across the studies included, six different radiographic parameters were used to derive several measures which were repeatedly and significantly associated with the occurrence of dysphagia.

CONCLUSIONS

The high incidence of postoperative dysphagia following OCF warrants close monitoring of patients, especially in the short-term postoperative period. These patients may be assessed through standardized tools where the one by Bazaz et al. was the most commonly used. Moreover, there are several radiographic measurements that can be used to predict the occurrence of dysphagia. These findings may serve as a basis for strategies to prevent the occurrence of dysphagia after OCF.

A new radiological parameter as a predictor of dysphagia based on oro-pharyngeal stenosis in a cohort of pediatric patients undergoing mal-reduced C1-2 pedicle screw fixation

PURPOSE

C1 pedicle screw technique showed further advantages since it avoids the negative results from the sacrificed range of motion of the atlantooccipital joint compared to the occipitocervical fusion. However, some intractable complications are unavoidable. In the pediatric population, dysphagia after the atlantoaxial fixation can be accidentally serious. We aimed to determine the incidence of dysphagia in the pediatric population's cohort and its radiological predictor.

METHODS

Between January 2010 and August 2018, this retrospective study included 42 pediatric patients with atlantoaxial dislocation due to trauma. They were followed up with an average duration of 8 years (range 5-18 years). Twenty-seven were males and 15 females with a mean age of 8.2 years (range 5-15 years) when undergoing operations. Patients were classified according to the presence of postoperative dysphagia according to the Bazaz dysphagia grading scale. The measurements, including pre- and postoperative CVT/NSL, O-C2, and C2-C7 sagittal angles, were performed.

RESULTS

26.2% of the patients (11/42) experienced postoperative dysphagia. A significant difference in the postoperative CVT/NSL (115.2 ± 13.2 vs.134.8 ± 17.3, P = 0.002), ΔCVT/NSL (7.0 ± 11.2 vs. 20.3 ± 10.5, P = 0.001), ΔO-C2 (- 3.2 ± 5.8 vs. 2.1 ± 5.1, P = 0.026), postoperative nPAS (9.4 ± 3.7 vs. 12.6 ± 4.2, P = 0.031) and ΔPAS (- 1.5 ± 4.1 vs. 2.0 ± 3.5, P = 0.010) between dysphagia group and non-dysphagia group were found. Adjustment for age, gender, and BMI, the multivariate logistic analysis showed that ΔCVT/NSL < 8.35° (OR = 5.23; 95% CI 4.97-5.50; P = 0.001) and ΔO-C2 (OR = 3.34; 95% CI 3.17-3.51; P = 0.001) remained associated with the occurrence of the swallowing problems.

CONCLUSION

In comparison with ΔO-C2, ΔCVT/NSL might better predict postoperative dysphagia in children.

LEVEL OF EVIDENCE I

Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Analysis of risk factors for postoperative dysphagia after C1-2 fusion

Objective

This study aimed to analyze the risk factors for dysphagia after C1-2 fusion in patients with C1-2 junction diseases.

Summary of the background data

Dysphagia is a common postoperative complication of posterior C1-2 junction surgery. The incidence is 9.5% to 26.3%. However, the etiopathogenisis of postoperative dysphagia remains controversial.

Methods

This retrospective study included patients who underwent C1-2 fusion from January 2016 to January 2020. The patients were divided into dysphagia group and control group in accordance with the Bazaz R dysphagia scoring system. The patients' age, gender, BMI(body mass index), cause of disease, and changes in the C01cobb, C02cobb, C12cobb, C27cobb, dC02cobb, dC01cobb, dC12cobb, d C27cobb angles before and after operation, were recorded. The parameters and changes were compared to analyze the risk factors for dysphagia after C1-2 fusion.

Results

65 cases (15, with dysphagia; 50, without dysphagia) were included. The incidence of postoperative dysphagia was 23%. The differences in age, gender ratio, and BMI between the two groups were not significant (P > 0.05). The differences among postoperative C12 (29.8° ± 11.24° vs. 20.46° ± 13.39°), postoperative C27cobb (10.56° ± 8.53° vs. 20.21° ± 13.21°), and dC12cobb (9.49° ± 5.16° vs. 1.07° ± 12.44°) between the two groups were significant (P < 0.05). Multiple logistic regression analyses revealed that dC12cobb > 5° was a significant independent risk factor for postoperative dysphagia, And preoperative C27cobb was a preventive factor of postoperative dysphagia.

Conclusions

Dysphagia after the C1-2 fusion was common. dC02cobb and dC12cobb were the significant independent risk factors for postoperative dysphagia. Preoperative c27cobb was a preventive factor of dysphagia.

Anatomical Parameters for Occipital Condyle Screws: An Analysis of 500 Condyles Using CT Scans

STUDY DESIGN

Retrospective observational study.

OBJECTIVE

To establish occipital condyle dimensions (length, width, height), as well as the medialization angle necessary for safe occipital condyle screw placement in occipitocervical fixation.

METHODS

Between 1/2014-6/2014, patients who presented to a single level 1 academic trauma center emergency room and received computed tomography (CT) imaging of the cervical spine as part of routine clinical care were identified. After excluding patients with cervical fractures, neoplastic disease, or infection, 500 condyles representing 250 patients were analyzed. Condyle length, height, and width (all reported in millimeters [mm]) were evaluated on the sagittal, coronal, and axial series, respectively. Medialization angle (reported in degrees) was evaluated on the axial series of CT imaging. Measurements were compared by sex and age.

RESULTS

The average condyle length, width, and height were 18.6 millimeters (mm) (range, 14.5-23.0 mm), 10.5 mm (range, 7.4-13.8 mm), and 11.3 mm (7.1-15.3 mm), respectively. Additionally, the average occipital condyle medialization angle was 23° (range, 14-32°). Occipital condyles of men were significantly longer, wider, and taller (all comparisons, p < 0.05). The medialization angle was significantly steeper for women than men (p < 0.05). No measurement differences were appreciated by age.

CONCLUSION

Our findings are similar to previous studies in the field; however, length appears slightly shorter. Further, measurement differences were appreciated by sex but not age. Thus, our measurement findings emphasize the importance of preoperative planning utilizing individual patient anatomy to ensure safe placement of occipital condyle screws for optimal outcomes.

[Research on effectiveness of occipito-odontoid angle in predicting dysphagia after occipitocervical fusion in patients with C 2, 3 Klippel-Feil syndrome]

OBJECTIVE

To introduce a new occipitocervical angle parameter, occipito-odontoid angle (O-Da), for predicting dysphagia after occipitocervical fusion (OCF) in patients with C _{2, 3} Klippel-Feil syndrome (KFS) and analyze its effectiveness.

METHODS

A total of 119 patients met selective criteria between April 2010 and November 2019 were retrospectively included as the study subjects. There were 56 males and 63 females. The age ranged from 14 to 76 years, with a median age of 51 years. There were 44 cases of basilar invagination and 75 cases of atlantoaxial subluxation. Forty patients were combined with C _{2, 3} KFS. Seven patients underwent anterior decompression combined with posterior OCF and 112 patients underwent posterior OCF. The fixed segments were O-C ₂ in 36 cases, O-C ₃ in 51 cases, O-C ₄ in 25 cases, and O-C ₅ in 7 cases. All patients were followed up 21-136 months, with a median time of 79 months. The lateral cervical X-ray films before operation and at last follow-up were used to measure the occipital to C ₂ angle (O-C ₂a), the occipital and external acoustic meatus to axis angle (O-EAa), the occipital protuberance to axial angle (Oc-Axa), the O-Da, and the narrowest oropharyngeal airway space (nPAS). The differences of the above parameters between the last follow-up and the preoperative values were calculated (represented as dO-C ₂a, dO-EAa, dOc-Axa, dO-Da, and dnPAS). Patients were divided into two groups according to whether they suffered dysphagia after operation, and the differences in clinical data and radiographic parameters were compared between the two groups. The correlation between occipitocervical angle parameters and nPAS in 40 patients with C _{2, 3} KFS was analyzed respectively. In addition, sensitivity and specificity analyses were used to assess the effectiveness of dO-Da≤-5° for the prediction of postoperative dysphagia.

RESULTS

Thirty-one patients (26.1%) suffered dysphagia after OCF (dysphagia group), including 10 patients with C _{2, 3} KFS; no dysphagia occurred in 88 patients (non-dysphagia group). There was no significant difference in age, follow-up time, fixed segment, proportion of patients with rheumatoid arthritis, proportion of patients with atlantoaxial subluxation, and proportion of patients with C _{2, 3} KFS between the two groups ( P>0.05). The proportion of female patients was significantly higher in dysphagia group than in non-dysphagia group ( χ ²=7.600, P=0.006). The difference in preoperative O-C ₂a between the two groups was significant ( t=2.528, P=0.014). No significant differences were observed in preoperative O-EAa, Oc-Axa, O-Da, and nPAS ( P>0.05). There was no significant difference in dO-C ₂a, dO-EAa, dOc-Axa, dO-Da, and dnPAS between the two groups ( P>0.05). The dO-C ₂a, dO-EAa, dOc-Axa, and dO-Da were positively correlated with dnPAS in 40 patients with C _{2, 3} KFS ( r=0.604, P<0.001; r=0.649, P<0.001; r=0.615, P<0.001; r=0.672, P<0.001). Taking dO-Da≤-5° as the standard, the sensitivity and specificity of dO-Da to predict postoperative dysphagia in patients with C _{2, 3} KFS were 80.0% (8/10) and 93.3% (28/30), respectively.

CONCLUSION

The dO-Da is a reliable indicator for predicting dysphagia after OCF in patients with C _{2, 3} KFS.

The predictive ability of occipital to C3 angle for dysphagia after occipitocervical fusion in patients with combined C2-3 Klippel-Feil syndrome

Background

Improper occipitocervical alignment after occipitocervical fusion (OCF) may lead to devastating complications, such as dysphagia and/or dyspnea. The occipital to C2 angle (O-C2a), occipital and external acoustic meatus to axis angle (O-EAa) have been used to evaluate occipitospinal alignment. However, it may be difficult to identify the inferior endplate of the C2 vertebra in patients with C2–3 Klippel-Feil syndrome (KFS). The purpose of this study aimed to compare four different parameters for predicting dysphagia after OCF in patients with C2–3 KFS.

Methods

There were 40 patients with C2–3 KFS undergoing OCF between 2010 and 2019. Radiographs of these patients were collected to measure the occipital to C3 angle (O-C3a), O-C2a, occipito-odontoid angle (O-Da), occipital to axial angle (Oc-Axa), and narrowest oropharyngeal airway space (nPAS). The presence of dysphagia was defined as the patient complaining of difficulty or excess endeavor to swallow. Patients were divided into two groups according to whether they had postoperative dysphagia. We evaluated the relationship between each of the angle parameters and nPAS and analyzed their influence to the postoperative dysphagia.

Results

The incidence of dysphagia after OCF was 25% in patients with C2–3 KFS. The Oc-Axa, and nPAS were smaller in the dysphagia group compared to non-dysphagia group at the final follow-up (p < 0.05). Receiver-operating characteristic (ROC) curves showed that dO-C3a had the highest accuracy as a predictor of the dysphagia with an area under the curve (AUC) of 0.868. The differences in O-C3a, O-C2a, O-Da, and Oc-Axa were all linearly correlated with nPAS scores preoperatively and at the final follow-up within C2–3 KFS patients, while there was a higher R² value between the dO-C3a and dnPAS. Multiple linear regression analysis showed that the difference of O-C3a was the only significant predictor for dnPAS (β = 0.670, p < 0.001).

Conclusions

The change of O-C3a (dO-C3a) is the most reliable indicator for evaluating occipitocervical alignment and predicting postoperative dysphagia in C2–3 KFS patients. Moreover, dO-C3a should be more than − 2° during OCF to reduce the occurrence of postoperative dysphagia.

CORRELATION OF craniovertebral PARAMETERS WITH THE RETROPHARYNGEAL SPACE IN POSTERIOR C1-C2 ARTHRODESIS

ABSTRACT Introduction/Objective: The craniovertebral junction (CVJ) requires a detailed evaluation, as the changes in alignment caused by surgery can affect adjacent structures in a secondary way. Examples of these effects are dyspnea or dysphagia after posterior occipitocervical arthrodesis, due to decreased caliber of the oropharynx. These changes can be identified perioperatively by several radiographic parameters that aim to predict possible postoperative respiratory complications. Such complications appear to be related to the narrowest oropharyngeal airway space (nPAS), and may also occur following atlantoaxial (C1-C2) arthrodesis. This work aims to correlate the variation in CVJ alignment parameters before and after C1-C2 arthrodesis with the variation in nPAS. Methods: Patients who underwent posterior C1-C2 arthrodesis between 2011 and 2019 at the National Institute of Traumatology and Orthopedics (INTO) were included in the study, totaling 26 patients. The parameters evaluated included cervical lordosis, C1-C2 angle, slope of C2, Occipito-C2 angle (O-C2), pharyngeal inlet angle (PIA), pharyngeal tilt angle (PTA), occiput and external acoustic meatus to axis angle (O-EAa), cranial transverse motion against C2 angle (C2TA), axial tilt (AT) and the percentage of change in nPAS (%∆nPAS). Results: A correlation was observed between the change in C1-C2 angle, O-C2, PTA, C2TA and the %∆nPAS. Conclusion: The change in cervical alignment and CVJ parameters is correlated with %∆nPAS and should, therefore, be evaluated before and after atlantoaxial fusion as a means of predicting a possible respiratory complication. Level of Evidence: III; Cross sectional study .

[Relationship between O-EA angle and lower cervical curvature in patients with anterior atlantoaxial dislocation before and after occipitocervical fusion]

Objective

To investigate the relationship between O-EA angle and lower cervical curvature in patients with anterior atlantoaxial dislocation undergoing occipitocervical fusion, and to analyze the effect of O-EA angle on lower cervical curvature.

Methods

The clinical data of 61 patients with anterior atlantoaxial dislocation undergoing occipitocervical fusion who were admitted between April 2010 and July 2018 and met the selection criteria were retrospectively analyzed. There were 32 males and 29 females, with an age of 14-76 years (mean, 50.7 years). The fixed segment included 19 cases of C ₀-C ₂, 27 cases of C ₀-C ₃, 14 cases of C ₀-C ₄, and 1 case of C ₀-C ₅. The O-EA angle, C _2-7 Cobb angle, and T ₁ tilt angle were measured before operation and at last follow-up. According to the O-EA angle measured at last follow-up, the patients were divided into <95° group (group A), 95°-105° group (group B), and >105° group (group C), and compared the differences of gender, age, fixed segment (short segment was at C ₃ and above, long segment was beyond C ₃), and C _2-7 Cobb angle. Correlation analysis between the O-EA angle and C _2-7 Cobb angle before operation and at last follow-up, as well as the changes of O-EA angle and C _2-7 Cobb angle between before operation and at last follow-up were analyzed.

Results

All 61 patients were followed up 12-24 months, with an average of 22.4 months. There was no significant difference in O-EA angle, C _2-7 Cobb angle, and T ₁ tilt angle before operation and at last follow-up ( P>0.05). According to the last follow-up O-EA angle grouping, there were 14 cases in group A, 29 cases in group B, and 18 cases in group C. There was no significant difference in age, gender composition, and fixed segment composition among the three groups ( P>0.05); the differences in C _2-7 Cobb angles among the three groups were significant ( P<0.05), groups A, B, and C showed a gradually increasing trend. The O-EA angle was positively correlated with C _2-7 Cobb angle before operation and at last follow-up ( r=0.572, P=0.000; r=0.618, P=0.000); O-EA angle change at last follow-up was also positively correlated with C _2-7 Cobb change ( r=0.446, P=0.000).

Conclusion

The O-EA angle of patients with anterior atlantoaxial dislocation is positively correlated with C _2-7 Cobb angle. Too large O-EA angle should be avoided during occipitocervical fixation, otherwise it may accelerate the degeneration of the lower cervical spine.

[Predictive abilities of O-C2 angle, O-EA angle, and Oc-Ax angle for the development of dysphagia in patients after occipitocervical fusion]

Objective

To compare the predictive abilities of O-C2 angle (O-C2a), O-EA angle (O-EAa), and Oc-Ax angle (Oc-Axa) for development of dysphagia in patients after occipitocervical fusion (OCF).

Methods

Between April 2010 and May 2019, 114 patients who underwent OCF and met the selection criteria were selected as the research objects. Among them, 54 were males and 60 were females; they were 14-76 years old, with an average of 50.6 years old. The follow-up time was 13-122 months (median, 60.5 months). The O-C2a, O-EAa, Oc-Axa, and the narrowest oropharyngeal airway space (nPAS) were measured by the lateral X-ray films before operation and at last follow-up, and the differences before and after operation (dO-C2a, dO-EAa, dOc-Axa, and dnPAS) were calculated. Patients were divided into two groups according to whether they had developed postoperative dysphagia. The general data including age, gender, fixed segment, proportion of patients with rheumatoid arthritis (RA), atlantoaxial subluxation (AS), and combined with anterior release surgery (ARS), and imaging indicators were compared between the two groups. The correlations between dO-C2a, dO-EAa, and dOc-Axa and dnPAS in 114 patients were analyzed to further compare the predictive value of three imaging indicators for occurrence of dysphagia after OCF.

Results

Dysphagia occurred after OCF in 31 cases with the incidence of 27.2%. There was significant difference in gender between the dysphagia group and the non-dysphagia group ( χ ²=7.940, P=0.005). There was no significant difference between the two groups in age, fixed segment, the proportion of patients with RA, the proportion of patients with AS, and the proportion of patients combined with ARS ( P>0.05). There was no significant difference in O-C2a and Oc-Axa of 114 patients before operation and at last follow-up ( P>0.05). The differences in O-EAa and nPAS were significant ( P<0.05). There was no significant difference in preoperative O-EAa, Oc-Axa, and nPAS between the dysphagia group and the non-dysphagia group ( P>0.05); the difference in the O-C2a was significant ( t=2.470, P=0.016). At last follow-up, the differences in the above imaging indicators were significant ( P<0.05). There were significant differences in the dO-C2a, dO-EAa, dOc-Axa, and dnPAS between the two groups ( P<0.05). Correlation analysis showed that the dO-C2a, dO-EAa, dOc-Axa were all positively correlated with dnPAS ( P<0.05). The dO-C2a≤-5°, postoperative O-EAa≤100°, postoperative Oc-Axa≤65° were all related to postoperative dysphagia ( P<0.05), and the highest risk factor suffering postoperative dysphagia was dO-C2a ≤-5° with a significant OR of 14.4.

Conclusion

The dO-C2a, postoperative O-EAa, and postoperative Oc-Axa can be used as the predictive indexes of dysphagia after OCF, among which dO-C2a has the highest predictive value.

Predictive abilities of O-C2a and O-EAa for the development of postoperative dysphagia in patients undergoing occipitocervical fusion

BACKGROUND CONTEXT

Dysphagia is a common postoperative complication in patients undergoing occipitocervical fusion (OCF). Previous studies had proposed the use of two measures-the occipital to C2 angle (O-C2a) and the occipital and external acoustic meatus to axis angle (O-EAa)-to predict postoperative dysphagia after OCF. However, these studies had small sample sizes and the predictive abilities of both measures are still not clear.

PURPOSE

To evaluate the predictive ability of O-EAa and O-C2a for dysphagia after OCF.

STUDY DESIGN

A retrospective clinical study.

PATIENT SAMPLE

A total of 109 consecutive patients who had undergone OCF.

OUTCOME MEASURES

Presence of postoperative dysphagia, O-C2a, C2 tilting angle (C2Ta), O-EAa, and the narrowest oropharyngeal airway space (nPAS).

METHODS

Between April 2010 and June 2018, 109 consecutive patients who had undergone OCF were reviewed. Patients were divided into two groups according to the presence of postoperative dysphagia. Radiographic measurements, including O-C2a, C2Ta, O-EAa, and nPAS, were evaluated at preoperative and 1 month postoperative and the findings were compared. Simple linear regression was used to measure the correlations between the parameters and the presence of dysphagia, and the correlations within the parameters. Multiple regression analysis was used to examine the variables that affected the change of nPAS (dnPAS%). Sensitivity and specificity analyses were used to evaluate the effectiveness of the previously proposed measures ("O-C2a change≤-5°" and "postoperative O-EAa<100°") for prediction of post-OCF dysphagia.

RESULTS

The incidence of dysphagia after OCF was 26.6% (29/109). Preoperative values for the radiographic parameters were similar between patients with and without dysphagia. In the dysphagia group, both O-C2a and O-EAa values showed a dramatic decrease after surgery, which was accompanied by a decrease in nPAS. Postoperative O-C2a, O-EAa, and nPAS in the dysphagia group were significantly smaller than those in the nondysphagia group (p<.05). The changes in O-EAa, O-C2a, and nPAS showed a linear correlation with the presence of dysphagia (p<.05). In addition, linear correlations were found between two of the three parameters. Multiple regression showed the change of O-C2a and O-EAa were significant predictors for dnPAS% (β=0.200, p=.022 and β=0.549, p=.000). The sensitivity and specificity of "O-C2a change≤-5°" in predicting dysphagia were 75.9% and 80.0% respectively, and those of "postoperative O-EAa<100°" were 75.9% and 62.5%, respectively. However, the sensitivity of the combination of these two values in predicting postoperative dysphagia was as high as 96.6%.

CONCLUSION

Both O-EAa and O-C2a could be critical predictors for postoperative dysphagia. During surgery, ensuring that the O-EAa exceeds 100° and simultaneously avoiding an O-C2a reduction greater than 5° could effectively avert postoperative dysphagia.