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Anterior cervical discectomy and fusion for the management of axial neck pain in the absence of radiculopathy or myelopathy

Study design: Systematic review Study rationale: Anterior cervical discectomy and fusion (ACDF) is a proven, effective treatment for relieving neck pain due to degenerative conditions of the cervical spine. Since most patients also present with radiculopathy or myelopathy, little is known as to the effectiveness of ACDF to relieve pain and improve function in patients without radicular or myelopathic symptoms. Objective: To examine the clinical outcome in patients undergoing (ACDF) for axial neck pain without radicular or myelopathic symptoms. Methods: A systematic review was undertaken for articles published up to March 2010. Electronic databases and reference lists of key articles were searched to identify studies evaluating ACDF for the treatment of axial neck pain only. Radiculopathy and myelopathy, patients who suffered severe trauma, or with tumor/metastatic disease or infection were excluded. Two independent reviewers assessed the strength of evidence using the grading of recommendations assessment, development and evaluation (GRADE) system, and disagreements were resolved by consensus. Results: No comparative studies were identified. Three case series met our inclusion criteria and were evaluated. All studies showed a mean improvement of pain of at least 50% approximately 4-years following surgery. Functional outcomes improved between 32% and 52% from baseline. Most patients reported satisfaction with surgery, 56% in one study and 79% in another. Complications varied among studies ranging from 1% to 10% and included pseudoarthrosis (9%), nonunion and revision (3%) and screw removal (1%). Conclusion: There is low evidence suggesting that patients with axial neck pain without radicular or myelopathic symptoms may receive some improvement in pain and function following ACDF. However, whether this benefit is greater than nontreatment or other treatments cannot be determined with the present literature.


STUDY RATIONALE AND CONTEXT
ACDF is a commonly performed procedure for degenerative conditions of the cervical spine with a successful fusion rate of approximately 95% and with overall good to excellent results [1,2]. The majority of patients present with combined complaints of axial neck pain with associated upper extremity radicular or myelopathic symptoms. There is considerable controversy, however, regarding the role of ACDF for neck pain without radiculopathy or myelopathy, and clinical outcome studies of ACDF with validated outcome measures in this patient population are scarce.

OBJECTIVES
To analyze the clinical outcome in patients treated with ACDF for axial neck pain in the absence of radiculopathy or myelopathy, especially with regard to changes in pain and function.

RESULTS
We found no studies comparing ACDF with conservative treatment for axial neck pain without radiculopathy or myelopathy. However, three case series, all graded class of evidence IV, met our inclusion criteria and form the basis for this report (Fig 1). Further details on the class of evidence determination can be found in the web appendix at www.aospine.org/ebsj.
Characteristics of each study are outlined in Table 1.
Overall, a total of 166 patients were included, with ages ranging from 21 to 76 years of age, and comprised of slightly more females than males. The majority of patients underwent 1 or 2-level fusion (84%, n = 140) followed by 3 or 4 level fusion (16%, n = 26).

Pain (Fig 2)
• All studies reported a mean improvement of over 50% at approximately 4-years follow-up, regardless of the number of levels fused.

Patient reported functional outcomes (Fig 3)
• Overall mean functional scores improved significantly compared with preoperative scores at approximately 4 years after surgery. Mean percent age improvement in ODI ranged from 32.3% to 51.9% across the three studies [3,4,5]. For the RMDI, a mean improvement of over 50% was seen in all patients, including sub-group analyses of 1 to 2-level and ≥ 3-level fusion, in one study [4].
Patient satisfaction and repeat surgery ( Table 2) • In two studies, 56% (n = 49) and 79% (n = 30) of patients reported that they were satisfied with the surgical outcome [4,5]. • Over 85% of patients in two studies said they would repeat the surgery [2,4].

CLINICAL GUIDELINES
No clinical guidelines were found addressing this question.

ILLUSTRATIVE CASE
A 43-year-old physically fit woman, with a history of tobacco abuse presented with a prolonged history of axial neck pain, recalcitrant to nonoperative treatments (Fig 4). Preoperative lateral x-rays showing degenerative disc disease at C4-7, with mild kyphosis (Fig 5). We strongly discouraged surgical treatment and recommended aerobic exercise. She returned several years later, having undergone a C4-7 ACDF with allograft elsewhere. The surgery helped for only a few months. X-rays, CT, and MRI revealed degenerative changes and mild anterolisthesis at C7-T1 and pseudoarthroses at C4-5 and C6-7 (Figs 6-8). Pseudoarthrosis repair was performed, noting that C7-T1 might require future surgery. Revision ACDF resulted in approximately 75% resolution of her axial pain (Fig 9).   Table 3) • Limitations of our SR: 1. Small number of studies available to address the issue, all with small sample sizes (n = 38, n = 41, n = 87). 2. No comparative studies available to compare outcomes with nonsurgical treatment. 3. All studies are case series, class of evidence IV. 4. The proportion of patients who achieve a clinically meaningful improvement in pain and function >30% is not reported. 5. There is no reference made to restoration of physiologic sagittal cervical spine with fusion patients. 6. Selection of fusion levels and integrity of discs adjacent to the operated levels is insufficiently addressed. 7. The role of provocative testing (ie, injections, blocks, cervical discography) was not addressed in this review and was not systematically used in the case series analyzed in this systematic review. • There is no class of evidence I-III data regarding the success rate of surgical treatment for axial neck pain. The lack of data may reflect the reluctance of academic spine surgeons to operate on axial neck pain in the absence of neurological symptoms. • Surgery for the treatment of axial neck pain remains controversial and there is scant literature to guide treatment of any form-operative and nonoperative. • In two studies, 56% (n = 49) and 79% (n = 30) of patients reported that they were satisfied with the surgical outcome. • A prospective randomized controlled study comparing surgical treatment to nonoperative measures, including aerobic exercise is needed, and due to the demonstrated relative therapeutic equipoise, appears ethically warranted.

EDITORIAL STAFF PERSPECTIVE
The subject of treatment for neck pain with anterior cervical discectomy and fusion and the methodology and findings of our authors evoked considerable debate among our reviewers. The inclusion of only three articles with a limited overall cohort was mentioned as a considerable limitation to the ability to conduct meaningful data analysis. Of course the vast mainstay of the available scientific literature reflects the overwhelming clinical indication for an anterior cervical discectomy and fusion in the setting of a degenerative disc disease. As is apparent in this formal systematic review, few authors have ventured beyond the accepted gold standards for ACDF to date. The second biggest controversy revolved around a subject, which will become increasingly contentious in the future, of the degree of improvement as measured in clinically related health outcomes questionnaires. In the three studies that met the inclusion criteria of the authors, the objective percentage of improvement in neck pain was between 50% and 60% at 4 years; the patient satisfaction was 56% and 79% in the two studies from which the data can be abstracted, and functional outcomes improved between 32% and 52% from baseline. Are these differences meaningful enough to warrant performing these procedures? The questions of level selection, restoration of normal sagittal alignment and actually achieving a solid fusion were felt to be considerable variables potentially affecting patient outcomes. Furthermore, how long do these results last? And the as yet unanswered question: does the presence of a rigidly fused level in the lower C-spine set an affected patient up for a cascade effect on other levels later on?
Certainly ACDF seems to have a positive treatment effect on patients who have failed nonoperative care for symptomatic cervical disc disease. The presented results do provide a justification of more formal study of this subject area.