Short-term Effect of Chewing Gum in Patients With Mild-moderate Dysphagia After Anterior Cervical Fusion
Phase: NA
Conditions: Dysphagia
Sponsor: Guangdong Provincial People's Hospital

Short-term Effect of Chewing Gum in Patients with Mild-moderate Dysphagia  
After Anterior Cervical Fusion 
 
Study Protocol & Statistical Analysis Plan 
(version 20180427) 
 
1. Trial design: A randomized, two arms, parallel-controlled, superiority trial.  
Allocation ratio = 1:1 
 
2. Participants:  
2.1 Eligibility criteria for participants 
(1) Inclusion criteria: 
- age from 18 years to 80 years. 
- underwent anterior cervical fusion surgery for degenerative cervical disease. 
- diagnosed with mild or moderate postoperative dysphagia 1 day after surgery 
using Bazaz scale. 
(2) Exclusion criteria: 
- Patients underwent revision procedures or procedures treating conditions other 
than degenerative cervical disease. 
- Patients with preoperative dysphagia. 
- Patients unable to chew, or unable to follow the directions for chewing gum. 
- Patients unable to attend follow-up visits or finish the dysphagia 
questionnaires. 
2.2 Settings and locations of data collection 
 The data is obtained face to face at the time of hospitalization, and via 
telephone after discharge.  
 
3. Interventions 
3.1 Arms:  
1) Chewing Gum Group - standard cares + chewing gum 
2) Control Group - standard cares only 
3.2 Chewing Gum Group 
Subjects assigned to the Chewing Gum Group are asked to chew gum four 
times a day for 5 days (15 minutes each time) after surgery in addition to standard 
cares. Standard cares include cleaning the wound every 2 days, wearing a collar, 
pain management, and education. 
3.3 Control Group 
Subjects assigned to the Control Group receive standard cares and are asked 
not to chew gum within 5 days after surgery. Standard cares include cleaning the 
wound every 2 days, wearing a collar, pain management, and education.  
 
4. Outcomes 
4.1 Primary outcome measurement 
Name: Dysphagia Short Questionnaire score (DSQ) 

Construct: DSQ is designed for the evaluation of swallowing difficulty after 
anterior cervical spine surgery. It is calculated by summing up the points given for 
each item, from 0 point to a maximum of 18 points, where lower scores represent 
milder symptoms and vice versa. (see Appendix I, quoted from Skeppholm M, et 
al. Spine, 2012, 37(11):996) 
Time Frame: change from the 1st day after surgery to the 7th day after surgery. 
4.2 Secondary outcome measurement 
1) Name: Bazaz grading system 
Construct: Bazaz grading system is designed for the evaluation of swallowing 
difficulty after anterior cervical spine surgery. The patients are graded as having 
none, mild, moderate, or severe dysphagia based on their symptoms. A none or 
mild dysphagia is considered to be a better outcome. (see Appendix II, quoted from 
Bazaz R, et al. Spine, 2002, 27(22):2453-2458.) 
Time Frame: change from the 1st day after surgery to the 7th day after surgery. 
2) Name: Prevertebral soft tissue swelling 
Construct: The measurement of the soft tissue space is made on the line parallel 
to the upper end plate from the midpoint of the anterior surface of each vertebral 
body to the border of the airway shadow. This scale ranges from 0 to approximately 
30 mm for each vertebra, where a lower value represents a milder soft tissue 
swelling. (see Appendix III, quoted from Suk K, et al. International Orthopaedics, 
2006, 30(4):290-4.) 
Time Frame: the 3rd days after surgery. 
 
5. Sample size 
It is estimated that 90 participants (45 per group, allowing for 15% attrition) 
would be required to detect a 1 score difference of DSQ between the groups with 
80% power and alpha of 0.05, based on our preliminary results.  
 
6. Randomisation 
At the first study visit after surgery, patients are invited to participate by 
providing written informed consent. Participants are randomly allocated according 
to a randomization schedule, which is generated by a designated person in our 
statistics department, who is not involved in the rest of the study. 
 
7. Blinding 
The outcomes assessors are masked to patient allocation, but patients and 
treatment providers are open-labelled. 
 
8. Statistical analysis plan 
The differences of change value of DSQ and postoperative Prevertebral Soft-
tissue Swelling between two group are compared using student t-test. The 
differences of change grading of Bazaz scale between two groups are compared 
using Wilcoxon rank sum test. P<0.05 is considered statistically significant. 
 

9. Appendix 
 
Appendix I: Dysphagia Short Questionnaire 
 
Please tick one box only, under each heading. 
Ability to swallow 
Points  
I have no difficulty in swallowing 
0 
Food occasionally gets stuck in my throat if I have not chewed it thoroughly 
enough 
1 
I find it hard to swallow solid food 
2 
I find it hard to swallow liquid food 
3 
I find it hard to swallow saliva 
4 
Incorrect swallowing 
 
I do not feel that I swallow incorrectly 
0 
I sometimes feel I’m swallowing incorrectly, though it does not cause me to 
cough 
1 
I sometimes cough in connection with swallowing 
2 
I frequently cough in connection with swallowing 
3 
I always get a fit of coughing when I swallow 
4 
Lump feeling 
 
I do not have the feeling there is a lump in my throat 
0 
I sometimes have the feeling there is a lump in my throat 
1 
I always have the feeling there is a lump in my throat 
2 
Involuntary loss of weight 
 
I have not lost weight recently 
0 
I have lost three or four pounds recently 
2 
I have lost more than five pounds recently 
4 
Pneumonia 
 
I have not had pneumonia  
0 
I have had the occasional bout of pneumonia  
2 
I have had repeated bouts of pneumonia  
4 
 
 
Appendix II: Bazaz grading system 
 
Severity of dysphagia 
Symptoms 
Liquid 
Solid 
None 
None 
None 
Mild 
None 
Rare 
Moderate 
None or rare 
Occasionally (only with specific food) 
Severe 
None or rare 
Frequently (majorty of solids) 
 
 

 
Appendix III: Prevertebral soft tissue swelling 
 
 
*The prevertebral soft tissue swelling is measured as the distance between the anterior 
surface of each vertebral body and the air shadow of the airway.