The incidence of postoperative dysphagia after ACDF varies widely in previous studies, ranging from 5% to 69% [4
] (Table ). This disparity is likely related to variations in study design and in the definition and measurement of dysphagia. Many of the existing studies of postoperative dysphagia are retrospective in nature and draw conclusions based on data that exist in the medical chart. A recent study [9
] showed that postoperative dysphagia after anterior cervical spine surgery was underreported by physicians in the medical chart. We therefore (1) prospectively determined the incidence and severity of dysphagia after ACDF using lumbar decompression patients as a control group; and (2) determined which factors, if any, are associated with increased postoperative dysphagia. [4
Reported incidence of dysphagia after anterior cervical spine surgery
Our study had several limitations. First, we had no objective measurements of dysphagia. Although videofluoroscopic swallow evaluation (VSE) is often considered the “gold standard” in the evaluation of swallowing function, such objective measures of dysphagia are extremely sensitive in patients undergoing anterior cervical surgery. In 2002, Frempong-Boadu et al. [12
] performed a prospective study of the incidence of dysphagia in anterior cervical surgery patients, performing VSE on the patients before and after surgery. These authors found 48% of patients had objective evidence of dysphagia on VSE preoperatively. None of these patients, however, had preoperative subjective complaints of swallowing difficulty. Although objective evaluation of dysphagia provides important information, patient-reported measures of dysphagia may be more clinically relevant. Second, there were differences between groups at baseline that may have affected the results of this study, including gender, operative time, and positioning of the patient (ie, prone versus supine). These differences are reflective of the patient population and nature of surgery of each group. Ideally, a control group with similar positioning and operative time would be used to control for operative variables. Third, our data in this study may not be applicable to patients undergoing anterior cervical surgery on greater than two levels, revision anterior cervical surgery, or anterior cervical surgery for etiologies other than degenerative disease such as trauma, infection, or tumor. We focused on the most common anterior cervical procedures performed. Inclusion of less commonly performed procedures and indications for surgery would have likely led to the enrollment of small numbers of patients within these subgroups, data from which would be difficult to interpret. Fourth, the outcome measures that we used to measure the incidence and severity of postoperative dysphagia (ie, the Bazaz score [4
] and dysphagia numeric rating score) are not validated measures. It should be noted that the Bazaz scores seem more severe than the dysphagia numeric rating score in the cervical group. For example, the mean dysphagia numeric rating score is 3.24 in the cervical group at 2 weeks followup, whereas 61% of patients having cervical spine surgery have moderate to severe dysphagia at 2 weeks according to the Bazaz score. This disparity is reflective of the lack of validation of these two measures. The Bazaz score [4
] is, however, the most widely used dysphagia measurement tool used to study postoperative dysphagia in anterior cervical surgery, and therefore its use in this study allows for the comparison of the results to the results of prior studies. Finally, this study has relatively short-term followup. Although the nature of dysphagia is most commonly a transient finding in the early postoperative period, there is a minority of patients who develop long-term issues with swallowing. It will be important to follow this patient population to gain a better understanding of the long-term effects of anterior cervical surgery on swallowing.
We found a relatively high incidence and severity of dysphagia in the early postoperative period after ACDF. The differences noted between the study and control groups suggest postoperative dysphagia is the result of the anterior cervical surgery itself rather than potential confounding factors such as general anesthesia or endotracheal intubation. The incidence of dysphagia in the early postoperative period after anterior cervical surgery in previous prospective analyses ranges from 30% to 50% [4
]. Bazaz et al. [4
] performed a prospective study on 221 patients on dysphagia after anterior cervical surgery. These authors reported an overall incidence of postoperative dysphagia of 50% at 1 month, 32% at 2 months, and 18% at 6 months. The incidence of moderate to severe dysphagia at 6 months was 5%. Papavero et al. [23
] reported a 49% incidence of postoperative dysphagia after anterior cervical surgery. This study only included followup data out to the fifth postoperative day. Chin et al. [7
] prospectively studied the effect of plate thickness on postoperative dysphagia after anterior cervical fusion surgery. Patients with a plate that did not protrude past the anterior margin of the preoperative anterior osteophytes had a 30% incidence of dysphagia lasting a mean of 38 days compared with a 38% incidence of dysphagia lasting a mean of 76 days in patients in whom the plate extended past the anterior margin of preoperative anterior osteophytes. The only existing prospective, controlled analysis of postoperative dysphagia is that by Smith-Hammond et al. [27
], who compared patients undergoing ACDF with those undergoing either posterior cervical or posterior lumbar surgery. These authors reported that 47% of patients having anterior cervical spine surgery had evidence of dysphagia on postoperative VSE. The dysphagia in 70% of these patients resolved within 2 months from surgery, whereas 23% had some degree of dysphagia that persisted for up to 10 months. In a large prospective study of 310 patients undergoing anterior cervical surgery with 2-year followup, Lee et al. [18
] reported a 54% incidence of dysphagia at 1 month, an 18.6% incidence of dysphagia at 6 months, and a 13.6% incidence of dysphagia at 2 years postoperatively. We found a higher incidence of postoperative dysphagia in the early postoperative period than previously reported with 71% of patients demonstrating dysphagia at 2 weeks followup. The postoperative dysphagia was, however, relatively transient compared with previous reports with only 8% of patients demonstrating dysphagia at 12 weeks followup.
We did not find that the location of cervical surgery (ie, high versus low) or the level of surgery (ie, one versus two) affected the risk of developing postoperative dysphagia. It should be noted, however, that the subgroup analysis within the cervical surgery patients (ie, location and number of levels of surgery) resulted in relatively small group sizes (Tables , ). Therefore, it is possible that there was not adequate power to show differences that may exist between these subgroups. These findings are consistent with the findings of Smith-Hammond et al. [27
] and Chin et al. [7
]. Both Bazaz et al. [4
] and Lee et al. [18
] reported that the location of surgery did not influence the incidence of postoperative dysphagia but that patients undergoing multilevel ACDF had a greater incidence of postoperative dysphagia compared with those undergoing single-level surgery at 1- and 2-month followup. Frempong-Boadu et al. [12
] also reported that patients undergoing multilevel anterior cervical surgery demonstrated an increased incidence of postoperative swallowing abnormalities as demonstrated on VSE compared with those undergoing single-level surgery. Unlike the findings of Smith-Hammond et al. [27
] and Chin et al. [7
], who did not see increased operative time in those patients with postoperative dysphagia, we found that patients with postoperative dysphagia at the time of most recent followup (ie, 12 weeks) did have greater operative time. We found no differences in gender, age, or BMI when comparing patients with and without postoperative dysphagia. Several previous prospective studies have reported that females are more prone to developing postoperative dysphagia after anterior cervical surgery [4
Postoperative dysphagia after ACDF is a relatively common occurrence in the early postoperative period. It is, however, a relatively transient finding with the vast majority of cases resolving within 3 months. Given the differences observed in the incidence and severity of dysphagia when comparing the cervical and lumbar groups, it is likely that dysphagia after ACDF is the result of local factors relating to the surgery rather than other potential confounding factors, including endotracheal tube placement and general anesthesia. Although some disparity exists in the literature, age, gender, the number of levels of surgery, and the location of surgery do not seem to be related to postoperative dysphagia. Increased operative time, however, may be associated with greater incidence of persistent postoperative dysphagia.