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Osteophyte formation after multilevel anterior cervical discectomy and fusion causing a delayed presentation of functional dysphagia
The Spine Journal 10 (2010) e1–e5
Case Report
Osteophyte formation after multilevel anterior cervical discectomy and fusion causing a delayed presentation of functional dysphagia Patrick Shih, MDa, Patrick E. Simon, MDb, Harold J. Pelzer, DDS, MDb, John C. Liu, MDa,* a
Department of Neurological Surgery, Northwestern University, Feinberg School of Medicine, 676 N. St. Clair St., Ste 2210, Chicago, IL 60611, USA b Department of Otolaryngology, Northwestern University Feinberg School of Medicine, 303 East Chicago Avenue, Chicago, IL 60611, USA Received 14 December 2009; revised 13 February 2010; accepted 8 April 2010
Abstract
BACKGROUND CONTEXT: Anterior cervical discectomy and fusion (ACDF) is a common procedure used to treat radiculopathy and myelopathy from cervical degenerative disc disease. The complications for this procedure are well known. Dysphagia can occur in the postoperative setting. However, it is typically transient and does not last longer than 1 month after an operation. A de novo presentation of dysphagia occurring years after an operation is unique. Osteophyte formation can cause mass effect on the esophagus leading to obstruction of this conduit. However, there have been no reported cases of osteophyte growth fusing to surrounding structures leading to a functional dysphagia. PURPOSE: The authors describe a delayed presentation of functional dysphagia 9 years after an ACDF. This resulted from osteophyte formation originating from the cervical plate and tethering the thyroid cartilage and hyoid bone, thus limiting mobilization of the larynx. STUDY DESIGN/SETTING: Case report. METHODS: The osteophyte was disconnected at the origin of the plate allowing the contents of the neck to move independently. RESULT: After removal of the osteophyte complex at the base of the cervical plate, this patient experienced resolution of his dysphagia. CONCLUSION: Functional dysphagia can occur in a delayed fashion after ACDF from osteophytes tethering the cervical plate to the surrounding contents of the neck used for swallowing. Freeing the contents of the neck from the tethering osteophytes can alleviate symptoms related to a dysfunctional swallowing mechanism. Ó 2010 Elsevier Inc. All rights reserved.
Keywords:
Anterior cervical fusion; Dysphagia; Osteophytes
Introduction Anterior cervical discectomy and fusion (ACDF) is a common procedure performed by surgeons, with approximately 540,000 procedures performed in the United States between 1990 and 1999 [1]. It was first described by Robinson and Smith in 1955 [2] and popularized by FDA device/drug status: not applicable. Author disclosures: JCL (consulting, Medtronic; speaking/teaching arrangements, Medtronic; fellowship support, DePuy, Medtronic). * Corresponding author. Department of Neurological Surgery, Northwestern University, Feinberg School of Medicine, 676 N. St. Clair St, Ste 2210, Chicago, IL 60611, USA. Tel.: (312) 695-4299; fax: (312) 695-0225. E-mail address: [email protected] (J.C. Liu) 1529-9430/$ – see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.spinee.2010.04.014
Cloward [3]. Since that time, the complications of the procedure have been well documented in the literature [4–6]. Immediate complications occurring from surgery include dural tear or esophageal, tracheal, carotid artery, vertebral artery, spinal cord injury, or peripheral nerve injury. Over the course of a week after the operation, an epidural hematoma may develop, the airway may be compromised from edema or hematoma, or radiculopathy may ensue. The intermediate period is found to have complications related to dysphagia, dysphonia, bone graft extrusion, or wound infection. The major complications occurring in the longterm include graft and implant complications, pseudoarthrosis, and adjacent-level disease [7]. A delayed presentation of esophageal perforation has also been reported as a long-term complication [8]. Dysphagia is mentioned as
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P. Shih et al. / The Spine Journal 10 (2010) e1–e5
Fig. 1. X-ray of the cervical spine showing an osseous growth off the cervical plate.
a complication occurring in the intermediate period with the possibility of ensuing for a couple of years. It does not present in a delayed fashion. The authors proceed to describe an individual who underwent a three-level ACDF who had a normal swallowing mechanism but presented 9 years later with functional swallowing difficulties resulting from immobility of the pharynx secondary to tethering of the pharynx to osteophytes that developed anterior to the cervical plate.
History and presentation A 62-year-old man with a past medical history of hemorrhoids and diagnosis of cervical stenosis with myeloradiculopathy treated with a previous C3–C6 ACDF with a C2–C6 posterior cervical laminectomy and fusion presented with dysphagia. The initial operation was performed 9 years and 3 months before the presentation of dysphagia. Before his initial operation, his only regimented medication was multivitamins. During the initial operation, iliac crest allograft was placed into the disc spaces with no other substances used to augment fusion. An anterior cervical dynamic ABC plate (Aesculap, Tuttlingen, Germany) was placed at the time of the surgery. At the surgeon’s discretion, a posterior cervical laminectomy and instrumented fusion was performed in the same setting. No complications were noted from the operation. The estimated blood loss resulting from the combined operation was 2.8 liters. After discharge from the hospital, the patient had encountered some swallowing difficulties but has always been able to digest liquids. On presentation to the hospital 9 years and 3 months later, he was noted to have 3 days of difficulties swallowing his own saliva. This condition left him regurgitating fluids through his nose and created a choking sensation. During the interim time between his initial operation and current presentation, he had experienced a probable myocardial ischemic event, but otherwise had no surgical or medical treatment that may have contributed to the osteophyte formation or explained his dysphagia. Initial plain
Fig. 2. Computed tomography image of the neck in the (Top) axial and (Bottom) sagittal planes showing a bone osteophyte complex tethering the thyroid cartilage to the titanium cervical plate.
radiographs of his cervical spine showed a large osseous lesion originating from his anterior cervical plate and extending anteriorly (Fig. 1). On computed tomography scan of the neck, a large bony excrescence extending from the left anterolateral aspect of the C4 vertebral body developed a pseudoarticulation with the left hyoid bone and appeared fused to the left thyroid cartilage (Fig. 2). Furthermore, this bony osteophyte caused mass effect on the left posterior lateral hypopharynx at the level of the piriform sinus. A chest radiograph performed preoperatively revealed a new hazy opacification in the right middle lobe that was consistent with aspiration pneumonia. Examination On his examination, the patient was noted to be in no apparent distress but was expectorating all his oral secretions. His cranial nerves were intact, and he had a nonfocal examination. No masses or lesions were seen in the oral cavity, floor of mouth, buccal mucosa, or palate. His oral pharynx was obscured by a Mallampati Grade 4 view. No cervical lymphadenopathy was palpable. His neck examination was notable for near-complete limitation in range of motion in all vectors. An immobile trachea was noted on palpitation. Flexible fiberoptic laryngoscopy was performed revealing severe edema of the hypopharynx and an anteriorly tilting larynx. Operation An incision was made through the original incision on the left side of his neck through the skin, subcutaneous tissue, and platysma muscle. Flaps were elevated superiorly and inferiorly in the subplatysmal plane. The sternocleidomastoid
P. Shih et al. / The Spine Journal 10 (2010) e1–e5
e3
Fig. 3. Barium swallow study showing a thyroid cartilage and detached osseous structure that is mobile with swallowing.
muscle was mobilized and retracted laterally. The internal jugular vein, vagus nerve, and carotid artery were identified with some difficulty because of scar tissue. The internal jugular vein had multiple clips on it from previous surgery and, ultimately, had to be transected and ligated. The carotid artery and vagus nerve were retracted laterally. The omohyoid muscle and posterior belly of the digastric muscle were transected. The floor of the neck was identified, and all the soft tissue was mobilized from the level of the posterior belly of the digastric muscle to the omohyoid muscle. The larynx was fixed to the osteophyte growth from the plate, and it was extremely difficult to dissect the pharyngoesophageal complex off the underlying scar tissue and hardware. An abnormal hard growth was felt anterolaterally that was recognized as the osteophyte complex seen on imaging. The entire anterior spine region, including the trachea, was felt to be immobile because of tethering from the osteophyte complex. The osteophyte was approached from the lateral edge. As dissection proceeded inferiorly, the cervical plate became obvious. The surgical goal at this point shifted toward disconnecting the osteophyte at the level of the plate. A high-speed drill was used to disconnect this space. As drilling occurred across the base of the osteophyte complex, the trachea was recognized as being much more mobile. Once the pharyngoesophageal complex was noted to be free, the site was inspected and the wound was closed. Postoperative course After the patient was extubated on postoperative day number 1, a bedside swallow examination revealed significant improvement in his swallowing mechanism. A diet
was advanced from liquids to soft solids, and he did not encounter any swallowing difficulties or new signs of aspiration. He was noted to have a mildly horse voice. A gastrogaffin study on postoperative day 1 showed no esophageal perforation and minimal reflux into the nasopharynx, with mild aspiration. A cookie swallow examination on postoperative day 4 showed moderate oropharyngeal dysphagia but no evidence of aspiration (Fig. 3). Visualization of the cervical spine showed the thyroid bone and the osseous structures anterior to the plate to be mobile with relation to swallowing.
Discussion The act of deglutition requires a highly complex and coordinated interaction between the upper digestive tract and the larynx. In normal swallowing, as the oropharyngeal bolus breaches the faucial arches, a reflex in the brainstem swallowing center triggers a series of physiological events. To prevent direct passage of the oral contents past the larynx and into the trachea, the true vocal cords close, and the arytenoids tilt anteriorly to close the laryngeal entrance. As the bolus proceeds into the hypopharynx, it mechanically forces the epiglottis to cover the laryngeal entrance and guides its passage toward the upper esophageal sphincter (UES) [9,10]. In conjunction with these events the neck muscles (suprahyoid, thyrohyoid, and stylohyoid) contract to move the larynx and hyoid anteriorly. Immediately after glottic closure, the cricopharyngeal muscle relaxes and is pulled anteriorly, given its attachments to the lateral aspects of the cricoid cartilage [10,11]. The movement of the bolus through the UES completes the normal act of deglutition.
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The dysphagia experienced by the patient described in this case deviates from normal deglutition by two separate mechanisms. First, the hypopharynx was forced anteriorly by the presence of the osteophyte. This obstructed the passage of the bolus past the cricopharyngeal muscle. Second, the ability of the neck muscles to move the hyoid and larynx anteriorly was inhibited by the growth of the osteophyte into the thyroid cartilage. Thus, the risk of aspiration was compounded by an abnormal posteriorly positioned glottis, and a physically obstructed UES, leaving the bolus in prolonged contact with the laryngeal entrance. In patients undergoing ACDF, there may be some preexisting dysphagia seen on radiographic swallowing studies [12]. After surgery, subjective complaints of dysphagia and abnormal radiographic swallowing studies may be seen in the first week but typically resolve within 1 month after the operation. Three prospective studies have assessed the incidence of dysphagia [12–14]. One study found that the incidence of dysphagic postoperative ACDF to be 50.5% at 1 month after surgery but decreased to 12.5% at 1 year after surgery [13]. There have been correlations linking the cervical levels of surgery and the amount of swelling assessed on imaging with the incidence of dysphagia [15]. Despite all this, the etiology of dysphagia in the first 12 months after the operation is still poorly understood. Suspected causes during this period include vocal cord paralysis, localized edema, hardware complications, incompatibility of cervical graft, cervical and pharyngeal plexus injury, and vagal nerve injury causing reduced laryngeal elevation and reduced pharyngeal contractions. After ACDF, adjacent-level ossification has been noted to occur with plates that encroach the adjacent disc space. Adjacent-level ossification is noted to occur in 67% and 45% of cases in the cephalad and caudal segments, respectively when the plate to disc distance is less than 5 mm [16]. The occurrence of adjacent-level ossification is lower when the plate to disc distance is greater that 5 mm (24% and 5% for cephalad and caudal segments, respectively) [16]. When external immobilization is used instead on an internal plating system, the overall incidence of adjacentlevel ossification is extremely low and reported to occur in 3% of adjacent segments [17]. Any ossification present in the first 12 months after surgery has a higher likelihood of developing into advanced ossification at 24 months [18]. If no ossification is seen in the first 12 months, then the incidence of advance ossification occurring at 24 months is 1.8% [18]. Limiting the encroachment of the cervical plate to the disc space is encouraged to prevent future symptomatic ossification. Osteophyte formation in the setting of diffuse idiopathic skeletal hyperostosis has been shown to cause swallowing disorders. A retrospective analysis of patients experiencing swallowing difficulties from diffuse idiopathic skeletal hyperostosis undergoing surgical resection of large osteophytes has shown improvement of dysphagia in seven of nine study patients within 1 month after surgery with delayed
improvement in the remaining two patients [19]. Osteophytes in a more cranial location (C3/C4 and C45/C5) are felt to be restricting the epiglottis from closing the larynx and thus causing intradeglutitive aspiration. At C5/C6 and C6/C7, osteophytes restrict deglutition of solid food and limit elevation of the larynx during swallowing [20]. A thorough evaluation by otolaryngology with barium swallow, laryngeal endoscopy, or esophageal manometry can reveal normal results in these patients with postoperative dysphagia. Although, the literature has not been able to pinpoint a cause of dysphagia in postoperative ACDF patients, where there is no obvious cause of mass effect or tethering, surgical removal of instrumentation has been shown to provide success in treating dysphagia in 55% of patients who elect for elective removal of cervical plate for treatment of dysphagia [21]. It is hypothesized that the release of adhesions connecting the cervical plate to the esophagus allows a normal swallowing mechanism to occur. In our case report, it was felt that the tethering of bony osteophytes to the thyroid cartilage and surrounding pharynx contributed to a functional dysphagia. Although osteophytes over cervical plates are commonly seen in revision anterior cervical fusions, there have been no reported incidences of tethering of these osteophytes to surrounding structures. For suspected cases of delayed dysphagia in a patient who has undergone a previous cervical fusion, appropriate management should include plain radiographs of the cervical neck and computed tomography of the cervical spine to assess the amount of ossification that may lead to tethering of the surrounding neck structures. An otolaryngologist should perform an evaluation that should include a flexible laryngoscopy to evaluate for obvious causes of swallowing difficulties. Barium swallow studies can be helpful in providing additional information regarding the orchestrated movements needed for a functional swallow to occur. In addition, the radiographic series in a barium swallow study can assess the mobility of the thyroid cartilage and any osseous structures that appear attached to the cervical plate. Given the rarity of this condition, the chance of recurrences after treatment is unknown. Future follow-up for recurrence should be based on the current understanding of ossification occurring in patients after anterior cervical discectomy. Thus, ossified growth should be monitored closely in the first 12 months with imaging. If any ossification is seen during this time, then follow-up may be extended up to 2 years during which advanced ossification has been noted to occur. Options that may be exercised as a means of postoperative prophylaxis include the use of nonsteroidal antiinflammatories or radiation.
Conclusions Swallowing difficulties are common after ACDFs. Furthermore, large osteophyte formation causing mass effect
P. Shih et al. / The Spine Journal 10 (2010) e1–e5
on the esophagus is recognized as a potential cause of mechanical obstruction. However, tethering osteophytes after ACDFs leading to a functional dysphasia is a rare entity. Osteophyte formation can extend to tether the cervical spine to the surrounding structure of the neck. This tethering can impair the functional component of the swallowing mechanism in a delayed fashion. Surgical untethering of the thyroid cartilage and hyoid bone from the cervical spine can allow these structures to function independently and orchestrate a coordinated movement for swallowing to occur. References [1] Angevine PD, Arons RR, McCormick PC. National and regional rates and variation of cervical diskectomy with and without anterior fusion, 1990-1999. Spine 2003;28:931–40. [2] Robinson RA, Smith G. Anterolateral cervical disk removal and interbody fusion for cervical disk syndrome. Bulls Johns Hopkins Hosp 1955;96:223–4. [3] Cloward RB. The anterior approach for the removal of ruptured cervical disks. J Neurosurg 1958;15:602–17. [4] Daniels AH, Yoo JU, Ching A, et al. Adverse events associated with anterior cervical spine surgery. J Am Acad Orthop Surg 2008;16: 729–38. [5] Tew JM, Mayfield FH. Complications of surgery of the anterior cervical spine. Clin Neurosurg 1999;23:424–34. [6] Fountas KN, Kapsalaki EZ, Nikolakakos LG, et al. Anterior cervical discectomy and fusion associated complications. Spine 2007;32:2310–7. [7] Yue W, Brodner W, Highland TR. Persistent swallowing and voice problems after anterior cervical discectomy and fusion with allograft and plating: a 5- to 11-year follow-up study. Eur Spine J 2005;14: 677–82. [8] Lu DC, Theordore P, Korn WM, Chou D. Esophageal erosion 9 years after anterior cervical plate implantation. Surg Neurol 2008;69:310–3.
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[9] Logemann JA, Kahrilas PJ, Cheng J, et al. Closure mechanisms of laryngeal vestibule during swallow. Am J Physiol 1992;262(2 Pt 1): G338–44. [10] Mendell DA, Logemann JA. Temporal sequence of swallow events during the oropharyngeal swallow. J Speech Lang Hear Res 2007;50:1256–71. [11] Kahrilas PJ, Lin S, Chen J, Logemann JA. Oropharyngeal accommodation to swallow volume. Gastroenterology 1996;111:297–306. [12] Frempong-Boadu A, Houten JK, Osborn B, et al. Swallowing and speech dysfunction in patients undergoing anterior cervical discectomy and fusion: a prospective, objective preoperative and postoperative assessment. J Spinal Disord Tech 2002;15:362–8. [13] Bazaz R, Lee MJ, Yoo JU. Incidence of dysphagia after anterior cervical spine surgery. Spine 2002;27:2453–8. [14] Smith-Hammond CA, New KC, Pietrobon R, et al. Prospective analysis of incidence and risk factors of dysphagia in spine surgery patients: comparison of anterior cervical, posterior cervical, and lumbar procedure. Spine 2004;29:1441–6. [15] Riley LH, Skolasky RL, Albert TJ, et al. Dysphagia after anterior cervical decompression and fusion: prevalence and risk factors from a longitudinal cohort study. Spine 2005;30:2564–9. [16] Park JB, Cho YS, Riew KD. Development of adjacent-level ossification in patients with an anterior cervical plate. J Bone Joint Surg Am 2005;87:558–63. [17] Yang JY, Song HS, Lee M, et al. Adjacent level ossification development after anterior cervical fusion without plate fixation. Spine 2009;34:30–3. [18] Park JB, Watthanaaphisit T, Riew KD. Timing of development of adjacent-level ossification after cervical arthrodesis with plates. Spine J 2007;7:633–6. [19] Oppenlander ME, Orringer DA, La Marca F, et al. Dysphagia due to anterior cervical hyperosteophytosis. Surg Neurol 2009;72:266–70. ` lvarez JC, Wonneberger K. Dysphagia caused by [20] Seidler TO, Pe`rez A ventral osteophytes of the cervical spine: clinical and radiographic findings. Eur Arch Otorhinolaryngol 2009;266:285–91. [21] Fogel GR, McDonnell MF. Surgical treatment of dysphagia after anterior cervical interbody fusion. Spine J 2005;5:140–4.
Case Report
Osteophyte formation after multilevel anterior cervical discectomy and fusion causing a delayed presentation of functional dysphagia Patrick Shih, MDa, Patrick E. Simon, MDb, Harold J. Pelzer, DDS, MDb, John C. Liu, MDa,* a
Department of Neurological Surgery, Northwestern University, Feinberg School of Medicine, 676 N. St. Clair St., Ste 2210, Chicago, IL 60611, USA b Department of Otolaryngology, Northwestern University Feinberg School of Medicine, 303 East Chicago Avenue, Chicago, IL 60611, USA Received 14 December 2009; revised 13 February 2010; accepted 8 April 2010
Abstract
BACKGROUND CONTEXT: Anterior cervical discectomy and fusion (ACDF) is a common procedure used to treat radiculopathy and myelopathy from cervical degenerative disc disease. The complications for this procedure are well known. Dysphagia can occur in the postoperative setting. However, it is typically transient and does not last longer than 1 month after an operation. A de novo presentation of dysphagia occurring years after an operation is unique. Osteophyte formation can cause mass effect on the esophagus leading to obstruction of this conduit. However, there have been no reported cases of osteophyte growth fusing to surrounding structures leading to a functional dysphagia. PURPOSE: The authors describe a delayed presentation of functional dysphagia 9 years after an ACDF. This resulted from osteophyte formation originating from the cervical plate and tethering the thyroid cartilage and hyoid bone, thus limiting mobilization of the larynx. STUDY DESIGN/SETTING: Case report. METHODS: The osteophyte was disconnected at the origin of the plate allowing the contents of the neck to move independently. RESULT: After removal of the osteophyte complex at the base of the cervical plate, this patient experienced resolution of his dysphagia. CONCLUSION: Functional dysphagia can occur in a delayed fashion after ACDF from osteophytes tethering the cervical plate to the surrounding contents of the neck used for swallowing. Freeing the contents of the neck from the tethering osteophytes can alleviate symptoms related to a dysfunctional swallowing mechanism. Ó 2010 Elsevier Inc. All rights reserved.
Keywords:
Anterior cervical fusion; Dysphagia; Osteophytes
Introduction Anterior cervical discectomy and fusion (ACDF) is a common procedure performed by surgeons, with approximately 540,000 procedures performed in the United States between 1990 and 1999 [1]. It was first described by Robinson and Smith in 1955 [2] and popularized by FDA device/drug status: not applicable. Author disclosures: JCL (consulting, Medtronic; speaking/teaching arrangements, Medtronic; fellowship support, DePuy, Medtronic). * Corresponding author. Department of Neurological Surgery, Northwestern University, Feinberg School of Medicine, 676 N. St. Clair St, Ste 2210, Chicago, IL 60611, USA. Tel.: (312) 695-4299; fax: (312) 695-0225. E-mail address: [email protected] (J.C. Liu) 1529-9430/$ – see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.spinee.2010.04.014
Cloward [3]. Since that time, the complications of the procedure have been well documented in the literature [4–6]. Immediate complications occurring from surgery include dural tear or esophageal, tracheal, carotid artery, vertebral artery, spinal cord injury, or peripheral nerve injury. Over the course of a week after the operation, an epidural hematoma may develop, the airway may be compromised from edema or hematoma, or radiculopathy may ensue. The intermediate period is found to have complications related to dysphagia, dysphonia, bone graft extrusion, or wound infection. The major complications occurring in the longterm include graft and implant complications, pseudoarthrosis, and adjacent-level disease [7]. A delayed presentation of esophageal perforation has also been reported as a long-term complication [8]. Dysphagia is mentioned as
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P. Shih et al. / The Spine Journal 10 (2010) e1–e5
Fig. 1. X-ray of the cervical spine showing an osseous growth off the cervical plate.
a complication occurring in the intermediate period with the possibility of ensuing for a couple of years. It does not present in a delayed fashion. The authors proceed to describe an individual who underwent a three-level ACDF who had a normal swallowing mechanism but presented 9 years later with functional swallowing difficulties resulting from immobility of the pharynx secondary to tethering of the pharynx to osteophytes that developed anterior to the cervical plate.
History and presentation A 62-year-old man with a past medical history of hemorrhoids and diagnosis of cervical stenosis with myeloradiculopathy treated with a previous C3–C6 ACDF with a C2–C6 posterior cervical laminectomy and fusion presented with dysphagia. The initial operation was performed 9 years and 3 months before the presentation of dysphagia. Before his initial operation, his only regimented medication was multivitamins. During the initial operation, iliac crest allograft was placed into the disc spaces with no other substances used to augment fusion. An anterior cervical dynamic ABC plate (Aesculap, Tuttlingen, Germany) was placed at the time of the surgery. At the surgeon’s discretion, a posterior cervical laminectomy and instrumented fusion was performed in the same setting. No complications were noted from the operation. The estimated blood loss resulting from the combined operation was 2.8 liters. After discharge from the hospital, the patient had encountered some swallowing difficulties but has always been able to digest liquids. On presentation to the hospital 9 years and 3 months later, he was noted to have 3 days of difficulties swallowing his own saliva. This condition left him regurgitating fluids through his nose and created a choking sensation. During the interim time between his initial operation and current presentation, he had experienced a probable myocardial ischemic event, but otherwise had no surgical or medical treatment that may have contributed to the osteophyte formation or explained his dysphagia. Initial plain
Fig. 2. Computed tomography image of the neck in the (Top) axial and (Bottom) sagittal planes showing a bone osteophyte complex tethering the thyroid cartilage to the titanium cervical plate.
radiographs of his cervical spine showed a large osseous lesion originating from his anterior cervical plate and extending anteriorly (Fig. 1). On computed tomography scan of the neck, a large bony excrescence extending from the left anterolateral aspect of the C4 vertebral body developed a pseudoarticulation with the left hyoid bone and appeared fused to the left thyroid cartilage (Fig. 2). Furthermore, this bony osteophyte caused mass effect on the left posterior lateral hypopharynx at the level of the piriform sinus. A chest radiograph performed preoperatively revealed a new hazy opacification in the right middle lobe that was consistent with aspiration pneumonia. Examination On his examination, the patient was noted to be in no apparent distress but was expectorating all his oral secretions. His cranial nerves were intact, and he had a nonfocal examination. No masses or lesions were seen in the oral cavity, floor of mouth, buccal mucosa, or palate. His oral pharynx was obscured by a Mallampati Grade 4 view. No cervical lymphadenopathy was palpable. His neck examination was notable for near-complete limitation in range of motion in all vectors. An immobile trachea was noted on palpitation. Flexible fiberoptic laryngoscopy was performed revealing severe edema of the hypopharynx and an anteriorly tilting larynx. Operation An incision was made through the original incision on the left side of his neck through the skin, subcutaneous tissue, and platysma muscle. Flaps were elevated superiorly and inferiorly in the subplatysmal plane. The sternocleidomastoid
P. Shih et al. / The Spine Journal 10 (2010) e1–e5
e3
Fig. 3. Barium swallow study showing a thyroid cartilage and detached osseous structure that is mobile with swallowing.
muscle was mobilized and retracted laterally. The internal jugular vein, vagus nerve, and carotid artery were identified with some difficulty because of scar tissue. The internal jugular vein had multiple clips on it from previous surgery and, ultimately, had to be transected and ligated. The carotid artery and vagus nerve were retracted laterally. The omohyoid muscle and posterior belly of the digastric muscle were transected. The floor of the neck was identified, and all the soft tissue was mobilized from the level of the posterior belly of the digastric muscle to the omohyoid muscle. The larynx was fixed to the osteophyte growth from the plate, and it was extremely difficult to dissect the pharyngoesophageal complex off the underlying scar tissue and hardware. An abnormal hard growth was felt anterolaterally that was recognized as the osteophyte complex seen on imaging. The entire anterior spine region, including the trachea, was felt to be immobile because of tethering from the osteophyte complex. The osteophyte was approached from the lateral edge. As dissection proceeded inferiorly, the cervical plate became obvious. The surgical goal at this point shifted toward disconnecting the osteophyte at the level of the plate. A high-speed drill was used to disconnect this space. As drilling occurred across the base of the osteophyte complex, the trachea was recognized as being much more mobile. Once the pharyngoesophageal complex was noted to be free, the site was inspected and the wound was closed. Postoperative course After the patient was extubated on postoperative day number 1, a bedside swallow examination revealed significant improvement in his swallowing mechanism. A diet
was advanced from liquids to soft solids, and he did not encounter any swallowing difficulties or new signs of aspiration. He was noted to have a mildly horse voice. A gastrogaffin study on postoperative day 1 showed no esophageal perforation and minimal reflux into the nasopharynx, with mild aspiration. A cookie swallow examination on postoperative day 4 showed moderate oropharyngeal dysphagia but no evidence of aspiration (Fig. 3). Visualization of the cervical spine showed the thyroid bone and the osseous structures anterior to the plate to be mobile with relation to swallowing.
Discussion The act of deglutition requires a highly complex and coordinated interaction between the upper digestive tract and the larynx. In normal swallowing, as the oropharyngeal bolus breaches the faucial arches, a reflex in the brainstem swallowing center triggers a series of physiological events. To prevent direct passage of the oral contents past the larynx and into the trachea, the true vocal cords close, and the arytenoids tilt anteriorly to close the laryngeal entrance. As the bolus proceeds into the hypopharynx, it mechanically forces the epiglottis to cover the laryngeal entrance and guides its passage toward the upper esophageal sphincter (UES) [9,10]. In conjunction with these events the neck muscles (suprahyoid, thyrohyoid, and stylohyoid) contract to move the larynx and hyoid anteriorly. Immediately after glottic closure, the cricopharyngeal muscle relaxes and is pulled anteriorly, given its attachments to the lateral aspects of the cricoid cartilage [10,11]. The movement of the bolus through the UES completes the normal act of deglutition.
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The dysphagia experienced by the patient described in this case deviates from normal deglutition by two separate mechanisms. First, the hypopharynx was forced anteriorly by the presence of the osteophyte. This obstructed the passage of the bolus past the cricopharyngeal muscle. Second, the ability of the neck muscles to move the hyoid and larynx anteriorly was inhibited by the growth of the osteophyte into the thyroid cartilage. Thus, the risk of aspiration was compounded by an abnormal posteriorly positioned glottis, and a physically obstructed UES, leaving the bolus in prolonged contact with the laryngeal entrance. In patients undergoing ACDF, there may be some preexisting dysphagia seen on radiographic swallowing studies [12]. After surgery, subjective complaints of dysphagia and abnormal radiographic swallowing studies may be seen in the first week but typically resolve within 1 month after the operation. Three prospective studies have assessed the incidence of dysphagia [12–14]. One study found that the incidence of dysphagic postoperative ACDF to be 50.5% at 1 month after surgery but decreased to 12.5% at 1 year after surgery [13]. There have been correlations linking the cervical levels of surgery and the amount of swelling assessed on imaging with the incidence of dysphagia [15]. Despite all this, the etiology of dysphagia in the first 12 months after the operation is still poorly understood. Suspected causes during this period include vocal cord paralysis, localized edema, hardware complications, incompatibility of cervical graft, cervical and pharyngeal plexus injury, and vagal nerve injury causing reduced laryngeal elevation and reduced pharyngeal contractions. After ACDF, adjacent-level ossification has been noted to occur with plates that encroach the adjacent disc space. Adjacent-level ossification is noted to occur in 67% and 45% of cases in the cephalad and caudal segments, respectively when the plate to disc distance is less than 5 mm [16]. The occurrence of adjacent-level ossification is lower when the plate to disc distance is greater that 5 mm (24% and 5% for cephalad and caudal segments, respectively) [16]. When external immobilization is used instead on an internal plating system, the overall incidence of adjacentlevel ossification is extremely low and reported to occur in 3% of adjacent segments [17]. Any ossification present in the first 12 months after surgery has a higher likelihood of developing into advanced ossification at 24 months [18]. If no ossification is seen in the first 12 months, then the incidence of advance ossification occurring at 24 months is 1.8% [18]. Limiting the encroachment of the cervical plate to the disc space is encouraged to prevent future symptomatic ossification. Osteophyte formation in the setting of diffuse idiopathic skeletal hyperostosis has been shown to cause swallowing disorders. A retrospective analysis of patients experiencing swallowing difficulties from diffuse idiopathic skeletal hyperostosis undergoing surgical resection of large osteophytes has shown improvement of dysphagia in seven of nine study patients within 1 month after surgery with delayed
improvement in the remaining two patients [19]. Osteophytes in a more cranial location (C3/C4 and C45/C5) are felt to be restricting the epiglottis from closing the larynx and thus causing intradeglutitive aspiration. At C5/C6 and C6/C7, osteophytes restrict deglutition of solid food and limit elevation of the larynx during swallowing [20]. A thorough evaluation by otolaryngology with barium swallow, laryngeal endoscopy, or esophageal manometry can reveal normal results in these patients with postoperative dysphagia. Although, the literature has not been able to pinpoint a cause of dysphagia in postoperative ACDF patients, where there is no obvious cause of mass effect or tethering, surgical removal of instrumentation has been shown to provide success in treating dysphagia in 55% of patients who elect for elective removal of cervical plate for treatment of dysphagia [21]. It is hypothesized that the release of adhesions connecting the cervical plate to the esophagus allows a normal swallowing mechanism to occur. In our case report, it was felt that the tethering of bony osteophytes to the thyroid cartilage and surrounding pharynx contributed to a functional dysphagia. Although osteophytes over cervical plates are commonly seen in revision anterior cervical fusions, there have been no reported incidences of tethering of these osteophytes to surrounding structures. For suspected cases of delayed dysphagia in a patient who has undergone a previous cervical fusion, appropriate management should include plain radiographs of the cervical neck and computed tomography of the cervical spine to assess the amount of ossification that may lead to tethering of the surrounding neck structures. An otolaryngologist should perform an evaluation that should include a flexible laryngoscopy to evaluate for obvious causes of swallowing difficulties. Barium swallow studies can be helpful in providing additional information regarding the orchestrated movements needed for a functional swallow to occur. In addition, the radiographic series in a barium swallow study can assess the mobility of the thyroid cartilage and any osseous structures that appear attached to the cervical plate. Given the rarity of this condition, the chance of recurrences after treatment is unknown. Future follow-up for recurrence should be based on the current understanding of ossification occurring in patients after anterior cervical discectomy. Thus, ossified growth should be monitored closely in the first 12 months with imaging. If any ossification is seen during this time, then follow-up may be extended up to 2 years during which advanced ossification has been noted to occur. Options that may be exercised as a means of postoperative prophylaxis include the use of nonsteroidal antiinflammatories or radiation.
Conclusions Swallowing difficulties are common after ACDFs. Furthermore, large osteophyte formation causing mass effect
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on the esophagus is recognized as a potential cause of mechanical obstruction. However, tethering osteophytes after ACDFs leading to a functional dysphasia is a rare entity. Osteophyte formation can extend to tether the cervical spine to the surrounding structure of the neck. This tethering can impair the functional component of the swallowing mechanism in a delayed fashion. Surgical untethering of the thyroid cartilage and hyoid bone from the cervical spine can allow these structures to function independently and orchestrate a coordinated movement for swallowing to occur. References [1] Angevine PD, Arons RR, McCormick PC. National and regional rates and variation of cervical diskectomy with and without anterior fusion, 1990-1999. Spine 2003;28:931–40. [2] Robinson RA, Smith G. Anterolateral cervical disk removal and interbody fusion for cervical disk syndrome. Bulls Johns Hopkins Hosp 1955;96:223–4. [3] Cloward RB. The anterior approach for the removal of ruptured cervical disks. J Neurosurg 1958;15:602–17. [4] Daniels AH, Yoo JU, Ching A, et al. Adverse events associated with anterior cervical spine surgery. J Am Acad Orthop Surg 2008;16: 729–38. [5] Tew JM, Mayfield FH. Complications of surgery of the anterior cervical spine. Clin Neurosurg 1999;23:424–34. [6] Fountas KN, Kapsalaki EZ, Nikolakakos LG, et al. Anterior cervical discectomy and fusion associated complications. Spine 2007;32:2310–7. [7] Yue W, Brodner W, Highland TR. Persistent swallowing and voice problems after anterior cervical discectomy and fusion with allograft and plating: a 5- to 11-year follow-up study. Eur Spine J 2005;14: 677–82. [8] Lu DC, Theordore P, Korn WM, Chou D. Esophageal erosion 9 years after anterior cervical plate implantation. Surg Neurol 2008;69:310–3.
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