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Comparison of clinical and radiographic outcome in instrumented anterior cervical discectomy and fusion with or without direct uncovertebral joint decompression
The Spine Journal 4 (2004) 629–635
Comparison of clinical and radiographic outcome in instrumented anterior cervical discectomy and fusion with or without direct uncovertebral joint decompression Francis H. Shen, MD, Dino Samartzis, BS, Nitin Khanna, MD, Edward J. Goldberg, MD, Howard S. An, MD* Department of Orthopedic Surgery, Rush Medical College, Rush-Presbyterian-St. Luke’s Medical Center, 1725 West Harrison St., Suite 1063 POB, Chicago, IL 60612, USA Received 7 August 2003; accepted 18 April 2004
Abstract
BACKGROUND CONTEXT: Anterior cervical discectomy and fusion (ACDF) is an established procedure for the operative treatment of cervical disc disease in patients with radiculopathy resulting from impingement from uncovertebral joint osteophytes. Studies demonstrate that direct decompression of the lesion provides good result. However, known complications include vertebral artery injury, dural tears, nerve root injury, loss of biomechanical stability and increased operative time. Other studies suggest that disc space distraction may play an important role by indirectly decompressing neural elements. Therefore, if equivalent functional outcomes can be achieved without sacrificing the uncovertebral joint, then potential morbidity and mortality could be decreased. PURPOSE: To assess and compare clinical and radiographic outcomes of patients with neck pain and cervical radiculopathy who underwent instrumented ACDF with or without direct uncovertebral joint decompression. STUDY DESIGN/SETTING: Retrospective clinical chart and radiographic review to assess clinical outcome and graft fusion in 109 patients who underwent one- or two-level ACDF with rigid anterior plate fixation. PATIENT SAMPLE: Radiographs and clinical charts for 109 patients (mean, 46 years; range, 27 to 83) who underwent ACDF with rigid anterior plate fixation were retrospectively reviewed at a single institution. Patients with radiculopathy resulting from herniated disc, spondylosis or a combination of both refractory to conservative treatment underwent surgery using a standard Smith-Robinson leftsided approach. Seventy-one patients who received direct uncovertebral joint decompression (Group 1) were compared with 38 patients without direct decompression but indirect decompression by disc space distraction (Group 2). In Group 1, 37 one-level and 34 two-level ACDFs were performed. In Group 2, 11 and 27 were one-level and two-level ACDFs, respectively. Smoking and workrelated injuries involved 26.7% and 38.0% of Group 1 and 28.9% and 28.9% of Group 2, respectively. Autologous iliac crest grafts were used in 51 patients, whereas 58 patients received allograft. OUTCOME MEASURES: Independent blinded analyses of plain lateral neutral, flexion and extension radiographs were conducted to assess fusion, evaluate graft and plate and screw integrity (mean, 12 months). Clinical outcomes were reported as excellent, good, fair or poor (mean, 23 months) based on Odom’s criteria. METHODS: Postoperative clinical outcome and radiographic studies of graft and instrument integrity were assessed in 71 patients undergoing ACDF with uncovertebral joint decompression and 38 patients without uncovertebral joint decompression, but with indirect decompression through disc space distraction.
FDA device/drug status: anterior cervical plate (approved for this indication). Nothing of value received from a commercial entity related to this research.
1529-9430/04/$ – see front matter doi:10.1016/j.spinee.2004.04.009
쑖 2004 Elsevier Inc. All rights reserved.
* Corresponding author. Department of Orthopedic Surgery, RushPresbyterian-St. Luke’s Medical Center, 1725 West Harrison Street, Suite 1063 POB, Chicago, IL 60612, USA. Tel.: (312) 243-4244; fax: (312) 942-1516. E-mail address: [email protected] (H.S. An)
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RESULTS: Fusion occurred in 95.8% of Group 1 and 100% of Group 2. In Group 1, 26.8% of the patients reported excellent results, 57.7% reported good results, 12.7% reported fair results and 2.8% reported poor results. In Group 2, 23.7% of the patients reported excellent results, 60.5% reported good results and 15.8% reported fair results. All nonunions reported good outcomes. Postoperative respiratory distress developed in one patient and dysphagia developed in another both from Group 1. No other complications were noted. The presence or absence of direct uncovertebral joint decompression and clinical outcome was not statistically significant (p⬎.05). The use of grafttype, operative level, presence of smoking and work-related injury in relation to clinical outcome was not found to be significant (p⬎.05). CONCLUSION: Good to excellent results were obtained in 84.5% and 84.2% of patients for Groups 1 and 2, respectively. Indirect foraminal decompression through distraction remains somewhat controversial during ACDF. However, sacrificing the uncovertebral joint can increase operative time and potentially increase complication rates. This study demonstrates that ACDF with or without direct uncovertebral joint decompression can provide good clinical results for neck pain with cervical radiculopathy. Therefore, routine direct uncovertebral joint decompression should not be undertaken during ACDF. 쑖 2004 Elsevier Inc. All rights reserved. Keywords:
Anterior cervical discectomy and fusion; Spondylosis; Radiculopathy; Uncovertebral joint; Fusion; Outcome
Introduction
Materials and methods
In selected patients who have failed conservative treatment, anterior cervical discectomy and fusion (ACDF) is an established procedure for the management of cervical neck pain and radiculopathy [1–7]. Patients with clinical evidence of radiculopathy and imaging studies consistent with anterior nerve root impingement may benefit from an ACDF. Because exiting cervical nerve roots are closely related to the posterior aspect of the uncovertebral joint [8], osteophytes arising from the uncinate process can produce foraminal stenosis resulting in cervical radiculopathy [9]. Although most authors believe that as much of the intervertebral disc as possible should be removed during ACDF [5,10–12], the role of direct uncovertebral joint decompression has been somewhat controversial and is rarely addressed. Some authors argue that the optimal and quickest results are achieved through decompression with direct removal of the offending bone spurs [1,13–17], whereas others believe that symptomatic relief can be achieved through disc space distraction, indirect decompression and resorption of the osteophytic spurs after solid arthrodesis [1,2,5,18,19]. However, clinical results of ACDFs that rely on indirect decompressions through disc space distraction can be compromised in cases of excessive graft subsidence and/or nonunions [20–22]. In the attempt to address these concerns, the use of rigid anterior plate fixation has enhanced fusion rates, reduced motion at the graft–end plate segment, maintained segmental cervical alignment, minimized graft subsidence and preserved desired disc space distraction [23–29]. Theoretically, if equivalent functional outcomes can be achieved without sacrificing the uncovertebral joint, then potential morbidity and mortality could be decreased. The goal of our study was to determine the clinical and radiographic outcome of patients who underwent ACDF with rigid anterior plate fixation with or without direct uncovertebral joint decompression.
The study is a retrospective clinical and radiographic review of 109 consecutive patients at a single institution over an 8-year period who underwent ACDF with rigid anterior plate fixation with or without uncovertebral joint decompression with a minimum of 1-year clinical follow-up. Indications for surgery included patients with radiculopathy secondary to herniated disc, spondylosis or a combination of both refractory to conservative treatment. Failure of conservative treatment was defined as either 1) progressive neurologic deficits, 2) failure of medical treatment for more than 3 months and 3) severe symptoms adversely affecting activities of daily living for a period less than 3 months [30]. Medical management included activity modification, anti-inflammatory medications, physical therapy and selective nerve root injections. Preoperative imaging studies assessed included anteroposterior, neutral lateral and flexion/extension radiographs and magnetic resonance imaging (MRI) of the cervical spine. Clinical examinations were carefully correlated with imaging studies, and patients who demonstrated evidence of compression of the nerve root(s) at either one or two cervical disc levels were included in the study. Patients who underwent a corpectomy, had three-level or greater disc disease, evidence of spinal cord involvement or myelopathy or whose clinical examination did not correlate with imaging studies were excluded from the study. Using these criteria, there were no differences between the two groups based on imaging studies. Operative procedures were performed by two fellowshiptrained orthopedic spine surgeons. The decision of whether to decompress the uncovertebral joint directly or indirectly through disc space distraction was based on the surgeon performing the procedure. At our institution, one surgeon routinely decompresses the uncovertebral joint osteophytes during every ACDF (Group 1), and the other surgeon
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obtains indirect foraminal decompression through disc space distraction (Group 2). Based on these selection criteria, this resulted in 109 consecutive patients for inclusion in the study. Group 1 consisted of 71 patients who underwent uncovertebral joint decompression. This group consisted of 44 men and 27 women with a mean age of 46 years (range, 27 to 83 years). In this group, 36 patients (50.7%) received autograft and 35 patients (49.3%) received allograft. Levels operated on included 37 one-level ACDFs (52.1%) at C3–C4 (n⫽2), C4– C5 (n⫽1), C5–C6 (n⫽17) and C6–C7 (n⫽17) and 34 twolevel ACDFs (47.9%) at C3–C5 (n⫽1), C4–C6 (n⫽8) and C5–C7 (n⫽25). Similarly, Group 2 consisted of 38 patients who did not receive decompression of the uncovertebral joints, but indirect decompression by means of disc space distraction. This group consisted of 21 men and 17 women with a mean age of 47 years (range, 28 to 67 years). Autograft and allograft were used in 15 (39.5%) and 23 (60.5%) patients, respectively, in Group 2. Patients in this group entailed 11 one-level ACDFs (28.9%) involving C3–C4 (n⫽2), C4– C5 (n⫽4), C5–C6 (n⫽2) and C6–C7 (n⫽3) and 32 two-level ACDFs (71.1%) involving C3–C5 (n⫽2), C4–C6 (n⫽7) and C5–C7 (n⫽18). In all patients where two-level ACDFs were performed, contiguous levels were fused. Smokers represented 26.7% and 28.9% of Group 1 and Group 2, respectively. All smokers were urged to adhere to a smoking cessation program before and after surgery. Work-related injuries involved 38.0% of Group 1 and 28.9% of Group 2. All ACDFs were performed using cervical traction, neuromonitoring and somatosensory evoked potentials. A standard Smith-Robinson anteromedial left-sided cervical approach was used in all cases [31]. After adequate exposure, intraoperative radiographs were obtained to confirm the appropriate level(s). Discectomies were performed by entering into the disc space with a number 15 scalpel blade at both the superior and inferior borders, followed by removal of the disc material sequentially with pituitary rongeurs and curettes. An intervertebral body spreader was carefully placed to allow for distraction of the disc space. Overhanging anterior osteophytes were removed to provide unobstructed access to the intervertebral disc space. In both groups, the decompression was taken to the posterior longitudinal ligament posteriorly and laterally out to the uncovertebral joints on both sides. In all patients a complete discectomy was performed and all articular cartilage was removed preserving the bony end plates. At this point, in patients undergoing direct uncovertebral joint decompression, a small curved microcurette is used to detach the posterior longitudinal ligament from the caudad vertebral body. In this plane, the curette is gradually advanced laterally over to the posterior portion of the uncovertebral joint. The safety of this technique is ensured by remaining on bone at all times. Once the uncovertebral joint is reached, the posterior longitudinal ligament is detached. Using loupe magnification, a 1-mm microkerrison punch is
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used to start the direct decompression of the uncovertebral joint. Once adequate space is created with the 1-mm kerrison punch, a 2-mm kerrison punch is used to complete the decompression of the neuroforamen. It is thought that an adequate decompression is obtained once a 2-mm kerrison punch and a nerve hook can be passed easily into the neuroforamen. After this point, both groups underwent fusion and plating. Autograft and allograft options with associated risks were discussed with each patient before surgery, and selection was based on patient preference. In cases where autogenous bone graft was selected, tricortical anterior iliac crest was harvested with a low-speed oscillating saw. Allografts were fresh frozen, vacuum-sealed, nonradiated tricortical grafts that were supplied by a single bone bank and defrosted in saline for 20 minutes before use. All grafts were fashioned in a typical Smith-Robinson formation. The disc spaces were measured with trials and the appropriate size bone graft selected. In patients who underwent indirect decompression, the graft sizes were selected to provide an additional 2 to 3 mm of distraction over the preoperative disc height [18]. The tricortical grafts were then inserted with the cortical surface anteriorly and countersunk 2 mm from the anterior vertebral border. Rigid anterior cervical plate fixation was applied in all cases and consisted of 37 PEAK (Depuy-Acromed, Rayham, MA), 30 Orion (Sofamor-Danek, Memphis, TN), 28 Atlantis (Sofamor-Danek, Memphis, TN), 3 AO Synthes, 8 VueLock EBI (Biomet, Warsaw, IN), 2 Codman (Johnson & Johnson, New Brunswick, NJ) and 1 Reflex (Stryker, Kalamazoo, MI). Selection of plate type was determined by generational design availability at the time of surgery and based on the surgeon’s preference. Before application of the plate, the anterior cervical surfaces of the operative vertebrae were burred down and each plate was contoured to accommodate vertebral convexity and obtain desired cervical lordosis and maximal bone–plate contact. Surgical midline was established based on anatomic landmarks. To avoid penetration into the spinal canal and cranial and caudal intervertebral disc spaces, unicortical screw purchase was achieved using a 14- or 16-mm drill guide directed toward the midline and parallel to the vertebral end plate. Meticulous hemostasis was achieved, and the incision was closured in layers over a deep drain. Postoperatively, all patients were placed in a soft collar for 3 to 4 weeks, the neck exercises were initiated, and gradual return to normal activity was permitted as tolerated. Follow-up lateral neutral, flexion and extension radiographs were used to assess fusion. Blinded analyses of plain radiographs were conducted (mean, 12 months; range, 3 to 55 months) to assess for evidence of fusion in both groups. Fusion had occurred if a bony bridge incorporated the graft and adjacent end plates and there was no evidence of motion or radiolucencies around the instrumentation. Patient charts on latest follow-up and prospective cervical spine outcome questionnaires and a modified outcomes questionnaire
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were used to assess patient function [32]. Clinical outcomes were reported as excellent, good, fair or poor (mean, 23 months; range, 12 to 60 months) based on Odom’s criteria (Table 1) [4]. Excellent and good outcomes were considered satisfactory. The data were collected and stored in a spreadsheet format and analyzed by SPSS statistical software. Statistical tests used to analyze different data parameters for statistical significance included analysis of variance, t tests and chi-squared analyses. Statistical significance was established at p⬍.05.
Table 2 Clinical outcome of instrumented one- and two-level anterior cervical discectomy and fusion, patients with or without direct decompression of the uncovertebral joints Direct uncovertebral joint decompression Yes
No
Odom’s score
Percent
n
Percent
n
Excellent Good Fair Poor Total count
26.8% 57.7% 12.7% 2.8% 100%
19 41 9 2 71
23.7% 60.5% 15.8% 0.0% 100%
9 23 6 0 38
Results An overall fusion rate of 97.2% was obtained for this series of one- and two-level ACDF patients with rigid anterior plate fixation. A 100% solid fusion rate was achieved in Group 2 (indirect decompression with disc space distraction), and a 95.8% fusion rate was noted in Group 1 (direct uncovertebral joint decompression). Fusion was achieved in 96.1% of autografts and in 98.3% of allografts. Fusion was noted in 96.7% of smokers and 97.2% of nonsmokers. Nonunion was noted in two patients who were nonsmokers at the level of C5–C6 with one-level instrumented ACDF and autograft. Nonunion was also noted in one two-level instrumented ACDF patient at the level of C4–C6 who was a smoker with allograft and developed dysphagia because of a pronounced inferior edge of the plate. Additional complications were noted in one patient in Group 1 who developed respiratory distress after surgery and required reintubation. No other intra- or postoperative clinical or radiographic complications were noted in this patient series. All nonunions were evaluated radiographically at a minimum of 1-year following surgery. Patients were followed clinically for a minimum of 1 year. The average clinical follow-up for all patients in this study was 23 months (range, 12 to 60 months). All nonunions achieved good clinical outcomes. Complete resolution of neck and radiculopathic pain was noted in 26.8% and 23.7% of Group 1 and Group 2, respectively (Table 2). Satisfactory clinical outcomes were achieved in 84.5% and 84.2% for Group 1 and Group 2, respectively. No statistical significance was noted between patients’ demographics, smoking, work-related injuries, operative level, type of graft, occurrence of fusion and presence of uncovertebral joint decompression to variation of clinical outcome (p⬎.05). Table 1 Odom’s clinical outcome ratings Excellent: Good: Fair: Poor:
No complaint referable to cervical disease; able to perform daily occupation without impairment. Intermittent discomfort referable to cervical disease; no significant interference with work. Subjective improvement in symptoms; physical activity significantly impaired Worsening or no improvement.
Discussion Anterior cervical discectomy and fusion was first described by Robinson and Smith in 1955. In their classic description, the original procedure was performed without the removal of the uncovertebral osteophytic spurs [33]. In subsequent modifications, Cloward emphasized that all compressive structures should be addressed and that direct decompression of the offending uncovertebral osteophytes was vital [34]. In response to this, Robinson stated, “Remodeling may well remove such spurs over time following stabilization of the spine and eliminat[e] abnormal mechanical forces, which are associated with spur formation” [5]. Since that time, there has been much debate over the need for direct uncovertebral joint decompression [1,13–17] versus indirect decompression through interbody height distraction [18,19] and osteophyte resorption [1,2,5,19,35,36]. In this current study, similar functional outcomes were found between the patients who underwent direct decompression (Group 1) as compared with those who had indirect decompression through interbody distraction (Group 2). At a mean follow-up of 23 months, excellent or good results occurred in 84.5% (60 of 71) and 84.2% (32 of 38) of Group 1 and Group 2 patients, respectively. Complete resolution of the neck and radicular arm pain was seen in 26.8% (19 of 71) of Group 1 and 23.7% (9 of 38) of Group 2 patients. However, there was no statistically significant difference between the results (p⬍.05). This study further confirms previous work from other authors that in the properly selected patient ACDF is a good surgical option for the treatment of patients with neck pain and cervical radiculopathy [1–7]. In the patients who underwent ACDF without direct uncovertebral joint decompression, the improvement in the radicular symptoms may be secondary to several factors, including indirect decompression through intervertebral disc space distraction and elimination of pathologic motion by achieving a solid arthrodesis. In patients with cervical spondylosis, the uncovertebral joint osteophytes impinge on nerve roots as they exit behind the uncovertebral joint [8]. Anatomically, the posterior aspect of the uncovertebral joint forms the anterior wall of the neuroforamen [8,37], and
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apical osteophytes arising from the uncinate process can result in foraminal stenosis [4,8,9,38]. In addition, disc height settling, as seen during disc degeneration, potentially narrows the neuroforamen in both the superior-inferior direction (foraminal height) and to some degree in the anterior-posterior direction (foraminal width). The associated bulge of the ligamentum flavum, posterior longitudinal ligament and other soft tissue restraints combined with any degree of associated subluxation will contribute to the narrowing of the neuroforamen. Therefore, adequate disc height distraction with restoration of sagittal alignment can potentially increase both foraminal height and width (Fig. 1). This is analogous to the lumbar spine, where a reduction in foraminal height and cross-sectional area is associated with nerve root entrapment and compression [39]. Using cadaveric spines and computed tomography analysis, it has been shown that foraminal cross-sectional area in the cervical spine can be increased during ACDF by increasing the interbody graft height [18]. This increase in foraminal cross-sectional area represents increased space for the exiting nerve root; it may result in improved vascular supply and relieves direct compression on an already compromised nerve. An overall fusion rate of 97.2% was seen in this group of 109 patients, with 95.8% of Group 1 and 100% of Group 2 patients eventually resulting in a solid arthrodesis. In our series, smoking, operative level and type of graft (autograft versus allograft) did not reach statistical significance (p⬍.05) for effecting eventual fusion. Although not statistically significant, all three nonunions occurred in patients who underwent direct uncovertebral joint decompression (Group 1). Two of the patients were plated, one-level ACDF with autograft and nonsmokers. The third nonunion occurred in a smoker who received allograft for plated two-level ACDF. Although various plate types were used in our series, all instrumentation fixation was rigid and assumed a load-bearing role. Furthermore, both allograft and autograft were used in both groups; however, high fusion rates and similar degree of graft settling are associated with rigid anterior plate fixation in one- or multilevel ACDF for both allograft and
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autograft [24,40,41]. Although smoking is also a factor associated with high rates of nonunion in noninstrumented ACDF [42–44], the use of instrumentation in ACDF decreases such a risk factor for nonunion [27,28,40,41,45]. As is evident in our series, patients with a history of smoking were urged to follow a smoking cessation program before and after surgery and did not demonstrate a significant difference in fusion rate in comparison to nonsmokers. Although many other factors may contribute to a successful fusion, retention of the uncovertebral joint may play some role. Biomechanically, sequential uncovertebral joint resection results in progressive cervical spine instability, especially in the patient who has undergone a discectomy [37,46,47]. Depending on the cervical level examined, the uncovertebral joint contributes 48% to 60% of the total stability at each level, with the posterior aspect of the uncovertebral joint providing greatest stability. Therefore, the standard cervical foraminotomy that decompresses the posterior portion of the uncovertebral joint, just anterior to the neuroforamen, actually removes the most stabilizing portion of the joint [37]. Critics argue that the importance of the role of the uncovertebral joint in cervical stability is irrelevant in the presence of a solid fusion. On this point, the authors would agree. However, if stability remains a vital component in achieving a successful fusion, then instability and motion at the graft site would lower ultimate fusion rate. If equivalent functional outcomes can be achieved without direct decompression, then preservation of the uncovertebral joint would theoretically provide the optimal environment in which to encourage a successful fusion. Overall complication rates associated with ACDF have been reported to range from 0 to 17% [35,48–56]. In our series there were two complications for an overall complication rate of 1.8%. One patient developed a transient dysphagia secondary to prominent spinal instrumentation. The second patient developed respiratory distress in the immediate perioperative period and required reintubation. Although both cases occurred in patients from Group 1, neither complication was attributed to the fact that the uncovertebral joint was directly decompressed.
Fig. 1. Preoperative schematic drawing of a parasagittal section demonstrating loss of the intervertebral disc height with subsequent neuroforaminal stenosis and nerve root impingement from uncovertebral joint osteophytes and loss of sagittal alignment. Postoperatively, indirect decompression is achieved through disc space distraction and sagittal realignment.
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Although the majority of complications are minor, major complications have been reported. In particular, because of the proximity of the vertebral artery to the uncovertebral joint, vertebral lacerations during foraminotomies or removal of the posterior lateral quadrant of the vertebral body have been reported [54,57]. Although no vascular injuries occurred in this series, the reported rate ranges from 0.3% to 0.5% during anterior cervical spine surgery. More importantly, although infrequent, when they do occur, the consequences can be catastrophic, resulting in significant ischemia, neurologic injury and potentially death [49,51,53,57,58]. In summary, in this current series the overall fusion rate was 97.2%, with good to excellent clinical results occurring in 84.4% of patients who underwent direct uncovertebral joint decompression and in patients with indirect decompression by distraction and leaving the uncovertebral joint intact. Indirect foraminal decompression through distraction remains somewhat controversial during ACDF. However, sacrificing the uncovertebral joint can increase operative time and potentially increase complication rates. This study demonstrates that ACDF with indirect decompression can provide good clinical results for neck pain with cervical radiculopathy. As a result, the authors do not recommend routine direct decompression of the uncovertebral joint during ACDF. However, the authors emphasize that indirect decompression is not a substitute for careful patient selection and proper surgical technique. A thorough and complete discectomy and proper disc space distraction of 2 to 3 mm is still required in order to achieve appropriate distraction and the eventual fusion necessary to obtain a good clinical outcome.
References [1] Bohlman HH, Emery SE, Goodfellow DB, Jones PK. Robinson anterior cervical discectomy and arthrodesis for cervical radiculopathy. J Bone Joint Surg [Am] 1993;75:1298–307. [2] Connolly ES, Seymour RJ, Adams JE. Clinical evaluation of anterior cervical fusions for degenerative cervcial disc disease. J Neurosurg 1965;23:431–7. [3] Dillin W, Boothe R, Cluckler J, Balderston R, Simeone F, Rothman R. Cervical radiculopathy. Spine 1986;11:988–91. [4] Odom G, Finney W, Woodhall B. Cervical disc lesions. JAMA 1958; 166:23–8. [5] Robinson RA, Walker AE, Ferlic DC, Wieking DK. The results of anterior interbody fusion of the cervical spine. J Bone Joint Surg [Am] 1962;44:1569–87. [6] White AA, Southwick W, Deponte R, Gainor JW, Hardy R. Relief of pain by anterior cervical spine fusion for spondylosis. A report of sixty-five patients. J Bone Joint Surg [Am] 1973;55:525–34. [7] Whitecloud T, Sherk H. Modern alternatives and techniques for onelevel discectomy and fusion. Clin Orthop Rel Res 1999;359:67–76. [8] Ebraheim NA, Jike L, Biyani A, Brown JA, Yeasting RA. Anatomic considerations for uncovertebral involvement in cervical spondylosis. Clin Orthop Rel Res 1997;334:200–6. [9] Tanaka N, Fujimoto Y, An H, Ikuta Y, Yasuda M. The anatomic relation among the nerve roots, intervertebral foramina, and intervertebral discs of the cervical spine. Spine 2000;25:286–91.
[10] Emery SE. Cervical disc disease and cervical spondylosis. In: An HS, editor. Principles and techniques of spine surgery. Philadelphia: Williams and Wilkins, 1998:401–12. [11] Fellrath RF, Hanley EN. Anterior cervical discectomy and arthrodesis for radiculopathy. In: Clark CR, editor. The cervical spine. Philadelphia: Lippincott-Raven, 1998:785–98. [12] Fischgrund J, Herkowitz HH. Anterior surgical procedures for cervical spondylotic radiculopathy and myelopathy. In: An HS, Simpson JM, editors. Surgery of the cervical spine. Philadelphia: Williams and Wilkins, 1994:195–212.Philadelphia: Williams and Wilkins: 1994: 195–212. [13] Brigham CD, Tsahakis PJ. Anterior cervical foraminotomy and fusion. Spine 1995;20:766–70. [14] Davis RA. A long-term outcome study of 170 surgically treated patients with compressive cervical radiculopathy. Surg Neurol 1996;46: 523–33. [15] Hakuba A. Transuncodiscal approach: a combined anterior and lateral approach to cervical discs. J Neurosurg 1976;45:284–91. [16] Jho HD. Microsurgical anterior cervical foraminotomy for radiculopathy: a new approach to cervical disc herniation. J Neurosurg 1983;13: 504–12. [17] Sonntag VKH, Han PP, Vishteh AG. Anterior cervical discectomy. Neurosurgery 2001;49:909–12. [18] An HS, Evanich CJ, Nowicki BH, Haughton VM. Ideal thickness of Smith-Robinson graft for anterior cervical fusion. Spine 1993;18: 2043–7. [19] Bayley JC, Yoo JU, Kruger DM, Schlegel J. The role of distraction in improving the space available for the cord in cervical spondylosis. Spine 1995;20:771–5. [20] Emery SE, Bolesta MJ, Banks MA, Jones PK. Robinson anterior cervical fusion comparison of the standard and modified techniques. Spine 1994;19:660–3. [21] Jenis LG, An HS, Simpson JM. A prospective comparison of the standard and reverse Robinson cervical grafting techniques: radiographic and clinical analyses. J Spinal Disord 2000;13:369–73. [22] Martin GJJ, Haid RWJ, MacMillian M, Rodts GEJ, Berkman R. Anterior cervical discectomy with freeze-dried fibula allograft: overview of 317 cases and literature review. Spine 1999;24:852–9. [23] Kaiser MG, Haid RWJ, Subach BR, Barnes B, Rodts GEJ. Anterior cervical plating enhances arthrodesis after discectomy and fusion with cortical allograft. Neurosurgery 2002;50:229–36. [24] Samartzis D, Shen FH, An HS. Effects of rigid plating on healing of anterior cervical grafts: preliminary results with the PEAK polyaxial plating system. Paper presented at: World Spine II; August 10–13, 2003; Chicago, IL. [25] Samartzis D, Shen FH, Matthews D, Yoon S, Goldberg E, An HS. Comparison of allograft to autograft in multilevel anterior cervical discectomy and fusion with rigid plate fixation. Spine J 2003;3:451–9. [26] Troyanovich SJ, Stroink AR, Kattner KA, Dornan WA, Gubina I. Does anterior plating maintain cervical lordosis versus conventional fusion techniques? A retrospective analysis of patients receiving single-level fusions. J Spinal Disord 2002;15:69–74. [27] Wang JC, McDonough PW, Endow KK, Delamarter RB. Increased fusion rates with cervical plating for two-level anterior cervical discectomy and fusion. Spine 2000;25:41–5. [28] Wang JC, McDonough PW, Endow KK, Kanim LE, Delamarter RB. The effect of cervical plating on single-level anterior cervical discectomy and fusion. J Spinal Disord 1999;12:467–71. [29] Wang JC, McDonough PW, Kanim LEA, Endow KK, Delamarter RB. Increased fusion rates with cervical plating for three-level anterior cervical discectomy and fusion. Spine 2001;26:643–7. [30] Bohlman HH, Emery SE. The pathophysiology of cervical spondylosis and myelopathy. Spine 1988;13:843–6. [31] Smith G, Robinson RA. The treatment of certain cervical spine disorders by anterior removal of the intervertebral disc and interbody fusion. J Bone Joint Surg [Am] 1958;40:607–24.
F.H. Shen et al. / The Spine Journal 4 (2004) 629–635 [32] BenDebba M, Heller J, Ducker TB, Eisinger JM. Cervical spine outcomes questionnaire: its development and psychometric properties. Spine 2002;27:2116–23. [33] Robinson R, Smith G. Anterolateral cervical disc removal and interbody fusion for cervical disc syndrome. Bull Johns Hopkins Hosp 1955;96:223–4. [34] Cloward RB. The anterior approach for removal of ruptured cervical discs. J Neurosurg 1958;15:602–14. [35] DePalma AF, Rothman R, Lewinneck G, Canale ST. Anterior interbody fusion for cervical disc degeneration. Surg Gynecol Obstet 1972;134:755–8. [36] Gore DR, Sepic SB. Anterior cervical fusion for degenerated or protruded discs. A review of one hundred forty-six patients. Spine 1984; 9:667–71. [37] Kotani Y, McNulty P, Abumi K, Cunningham B, Kaneda K, McAfee P. The role of anteromedial foraminotomy and the uncovertebral joints in the stability of the cervical spine: a biomechanical study. Spine 1998;23:1559–65. [38] MacNab I. Cervical spondylosis. Clin Orthop 1975;109:69–77. [39] Hasegawa T, An HS, Haughton VM, Nowicki BH. Lumbar foraminal stenosis: critical heights of the intervertebral discs and foramina. A cryomicrotome study in cadavera. J Bone Joint Surg [Am] 1995;77: 32–8. [40] Samartzis D, Lyon C, Phillips M, Goldberg EJ, An HS. Does rigid instrumentation increase the fusion rate in one-level anterior discectomy and fusion? Spine J 2004 (in press). [41] Samartzis D, Shen FH, Matthews D, Yoon S, Goldberg EJ, An HS. Comparison of allograft to autograft in multilevel anterior cervical discectomy and fusion with rigid plate fixation. Spine J 2003;3:451–9. [42] An HS, Simpson JM, Glover JM, Stephany J. Comparison between allograft plus demineralized bone matrix versus autograft in anterior cervical fusion. A prospective multicenter study. Spine 1995;15: 2211–6. [43] Cauthen JC, Kinard RE, Vogler JB, et al. Outcome analysis of noninstrumented anterior cervical discectomy and interbody fusion in 348 patients. Spine 1998;23:188–92. [44] Hilibrand AS, Fye MA, Emery SE, Palumbo MA, Bohlman HH. Impact of smoking on the outcome of anterior cervical arthrodesis with interbody or strut-grafting. J Bone Joint Surg Am 2001;83A:668–73.
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[45] Bose B. Anterior cervical instrumentation enhances fusion rates in multilevel reconstruction in smokers. J Spinal Disord 2001;14:3–9. [46] Chen T-Y, Crawford NR, Sonntag VKH, Dickman C. Biomechanical effects of progressive anterior cervical decompression. Spine 2001; 26:6–13. [47] White AA, Panjabi MM. Kinematics of the spine. In: White AA, Panjabi MM, editors. Clinical biomechanics of the Spine, 2nd ed. Philadelphia: J.B. Lippincott, 1990:85–126. [48] Flynn TB. Neurologic complications of anterior cervical interbody fusion. Spine 1982;7:536–9. [49] Golfinos JG, Dickman CA, Zabramski JM, Sonntag VLH, Spetzler RF. Repair of vertebral artery injury during anterior cervical decompression. Spine 1994;19:2552–6. [50] Herkowitz HH. The surgical management of cervical spondylotic radiculopathy and myelopathy. Clin Orthop 1989;239:94–108. [51] Pait T, Killefer J, Arnautovi K. Surgical anatomy of the anterior cervical spine: the disc space, vertebral artery, and associated bony structures. Neurosurgery 1996;39:769–75. [52] Shinomiya K, Okawa A, Nakao K, et al. Morphology of C5 ventral rootlets as part of dissociated motor loss of deltoid muscle. Spine 1994;19:2501–4. [53] Shintani A, Zervas NT. Consequences of ligation of the vertebral artery. J Neurosurg 1972;36:447–50. [54] Smith MD, Emery SE, Dudley A, Murray KJ, Leventhal M. Vertebral artery injury during anterior decompression of the cervical spine. A retrospective review of ten patients. J Bone Joint Surg [Br] 1993; 75:410–5. [55] Weinberg PE, Flom RA. Traumatic vertebral arteriovenous fistula. Surg Neurol 1973;1:162–7. [56] Whitecloud TS. Complications of anterior cervical fusion. American Academy of Orthopaedic Surgeons, Instructional Course Lectures, vol. 27. St. Louis: CV Mosby, 1978. [57] Curylo L, Mason H, Bohlman H, Yoo J. Tortuous course of the vertebral artery and anterior cervical decompression. Spine 2000; 25:2860–4. [58] Milne N. The role of zygapophyseal joint orientation and uncinate process in controlling motion in the cervical spine. J Anat 1991; 178:189–201.
Comparison of clinical and radiographic outcome in instrumented anterior cervical discectomy and fusion with or without direct uncovertebral joint decompression Francis H. Shen, MD, Dino Samartzis, BS, Nitin Khanna, MD, Edward J. Goldberg, MD, Howard S. An, MD* Department of Orthopedic Surgery, Rush Medical College, Rush-Presbyterian-St. Luke’s Medical Center, 1725 West Harrison St., Suite 1063 POB, Chicago, IL 60612, USA Received 7 August 2003; accepted 18 April 2004
Abstract
BACKGROUND CONTEXT: Anterior cervical discectomy and fusion (ACDF) is an established procedure for the operative treatment of cervical disc disease in patients with radiculopathy resulting from impingement from uncovertebral joint osteophytes. Studies demonstrate that direct decompression of the lesion provides good result. However, known complications include vertebral artery injury, dural tears, nerve root injury, loss of biomechanical stability and increased operative time. Other studies suggest that disc space distraction may play an important role by indirectly decompressing neural elements. Therefore, if equivalent functional outcomes can be achieved without sacrificing the uncovertebral joint, then potential morbidity and mortality could be decreased. PURPOSE: To assess and compare clinical and radiographic outcomes of patients with neck pain and cervical radiculopathy who underwent instrumented ACDF with or without direct uncovertebral joint decompression. STUDY DESIGN/SETTING: Retrospective clinical chart and radiographic review to assess clinical outcome and graft fusion in 109 patients who underwent one- or two-level ACDF with rigid anterior plate fixation. PATIENT SAMPLE: Radiographs and clinical charts for 109 patients (mean, 46 years; range, 27 to 83) who underwent ACDF with rigid anterior plate fixation were retrospectively reviewed at a single institution. Patients with radiculopathy resulting from herniated disc, spondylosis or a combination of both refractory to conservative treatment underwent surgery using a standard Smith-Robinson leftsided approach. Seventy-one patients who received direct uncovertebral joint decompression (Group 1) were compared with 38 patients without direct decompression but indirect decompression by disc space distraction (Group 2). In Group 1, 37 one-level and 34 two-level ACDFs were performed. In Group 2, 11 and 27 were one-level and two-level ACDFs, respectively. Smoking and workrelated injuries involved 26.7% and 38.0% of Group 1 and 28.9% and 28.9% of Group 2, respectively. Autologous iliac crest grafts were used in 51 patients, whereas 58 patients received allograft. OUTCOME MEASURES: Independent blinded analyses of plain lateral neutral, flexion and extension radiographs were conducted to assess fusion, evaluate graft and plate and screw integrity (mean, 12 months). Clinical outcomes were reported as excellent, good, fair or poor (mean, 23 months) based on Odom’s criteria. METHODS: Postoperative clinical outcome and radiographic studies of graft and instrument integrity were assessed in 71 patients undergoing ACDF with uncovertebral joint decompression and 38 patients without uncovertebral joint decompression, but with indirect decompression through disc space distraction.
FDA device/drug status: anterior cervical plate (approved for this indication). Nothing of value received from a commercial entity related to this research.
1529-9430/04/$ – see front matter doi:10.1016/j.spinee.2004.04.009
쑖 2004 Elsevier Inc. All rights reserved.
* Corresponding author. Department of Orthopedic Surgery, RushPresbyterian-St. Luke’s Medical Center, 1725 West Harrison Street, Suite 1063 POB, Chicago, IL 60612, USA. Tel.: (312) 243-4244; fax: (312) 942-1516. E-mail address: [email protected] (H.S. An)
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RESULTS: Fusion occurred in 95.8% of Group 1 and 100% of Group 2. In Group 1, 26.8% of the patients reported excellent results, 57.7% reported good results, 12.7% reported fair results and 2.8% reported poor results. In Group 2, 23.7% of the patients reported excellent results, 60.5% reported good results and 15.8% reported fair results. All nonunions reported good outcomes. Postoperative respiratory distress developed in one patient and dysphagia developed in another both from Group 1. No other complications were noted. The presence or absence of direct uncovertebral joint decompression and clinical outcome was not statistically significant (p⬎.05). The use of grafttype, operative level, presence of smoking and work-related injury in relation to clinical outcome was not found to be significant (p⬎.05). CONCLUSION: Good to excellent results were obtained in 84.5% and 84.2% of patients for Groups 1 and 2, respectively. Indirect foraminal decompression through distraction remains somewhat controversial during ACDF. However, sacrificing the uncovertebral joint can increase operative time and potentially increase complication rates. This study demonstrates that ACDF with or without direct uncovertebral joint decompression can provide good clinical results for neck pain with cervical radiculopathy. Therefore, routine direct uncovertebral joint decompression should not be undertaken during ACDF. 쑖 2004 Elsevier Inc. All rights reserved. Keywords:
Anterior cervical discectomy and fusion; Spondylosis; Radiculopathy; Uncovertebral joint; Fusion; Outcome
Introduction
Materials and methods
In selected patients who have failed conservative treatment, anterior cervical discectomy and fusion (ACDF) is an established procedure for the management of cervical neck pain and radiculopathy [1–7]. Patients with clinical evidence of radiculopathy and imaging studies consistent with anterior nerve root impingement may benefit from an ACDF. Because exiting cervical nerve roots are closely related to the posterior aspect of the uncovertebral joint [8], osteophytes arising from the uncinate process can produce foraminal stenosis resulting in cervical radiculopathy [9]. Although most authors believe that as much of the intervertebral disc as possible should be removed during ACDF [5,10–12], the role of direct uncovertebral joint decompression has been somewhat controversial and is rarely addressed. Some authors argue that the optimal and quickest results are achieved through decompression with direct removal of the offending bone spurs [1,13–17], whereas others believe that symptomatic relief can be achieved through disc space distraction, indirect decompression and resorption of the osteophytic spurs after solid arthrodesis [1,2,5,18,19]. However, clinical results of ACDFs that rely on indirect decompressions through disc space distraction can be compromised in cases of excessive graft subsidence and/or nonunions [20–22]. In the attempt to address these concerns, the use of rigid anterior plate fixation has enhanced fusion rates, reduced motion at the graft–end plate segment, maintained segmental cervical alignment, minimized graft subsidence and preserved desired disc space distraction [23–29]. Theoretically, if equivalent functional outcomes can be achieved without sacrificing the uncovertebral joint, then potential morbidity and mortality could be decreased. The goal of our study was to determine the clinical and radiographic outcome of patients who underwent ACDF with rigid anterior plate fixation with or without direct uncovertebral joint decompression.
The study is a retrospective clinical and radiographic review of 109 consecutive patients at a single institution over an 8-year period who underwent ACDF with rigid anterior plate fixation with or without uncovertebral joint decompression with a minimum of 1-year clinical follow-up. Indications for surgery included patients with radiculopathy secondary to herniated disc, spondylosis or a combination of both refractory to conservative treatment. Failure of conservative treatment was defined as either 1) progressive neurologic deficits, 2) failure of medical treatment for more than 3 months and 3) severe symptoms adversely affecting activities of daily living for a period less than 3 months [30]. Medical management included activity modification, anti-inflammatory medications, physical therapy and selective nerve root injections. Preoperative imaging studies assessed included anteroposterior, neutral lateral and flexion/extension radiographs and magnetic resonance imaging (MRI) of the cervical spine. Clinical examinations were carefully correlated with imaging studies, and patients who demonstrated evidence of compression of the nerve root(s) at either one or two cervical disc levels were included in the study. Patients who underwent a corpectomy, had three-level or greater disc disease, evidence of spinal cord involvement or myelopathy or whose clinical examination did not correlate with imaging studies were excluded from the study. Using these criteria, there were no differences between the two groups based on imaging studies. Operative procedures were performed by two fellowshiptrained orthopedic spine surgeons. The decision of whether to decompress the uncovertebral joint directly or indirectly through disc space distraction was based on the surgeon performing the procedure. At our institution, one surgeon routinely decompresses the uncovertebral joint osteophytes during every ACDF (Group 1), and the other surgeon
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obtains indirect foraminal decompression through disc space distraction (Group 2). Based on these selection criteria, this resulted in 109 consecutive patients for inclusion in the study. Group 1 consisted of 71 patients who underwent uncovertebral joint decompression. This group consisted of 44 men and 27 women with a mean age of 46 years (range, 27 to 83 years). In this group, 36 patients (50.7%) received autograft and 35 patients (49.3%) received allograft. Levels operated on included 37 one-level ACDFs (52.1%) at C3–C4 (n⫽2), C4– C5 (n⫽1), C5–C6 (n⫽17) and C6–C7 (n⫽17) and 34 twolevel ACDFs (47.9%) at C3–C5 (n⫽1), C4–C6 (n⫽8) and C5–C7 (n⫽25). Similarly, Group 2 consisted of 38 patients who did not receive decompression of the uncovertebral joints, but indirect decompression by means of disc space distraction. This group consisted of 21 men and 17 women with a mean age of 47 years (range, 28 to 67 years). Autograft and allograft were used in 15 (39.5%) and 23 (60.5%) patients, respectively, in Group 2. Patients in this group entailed 11 one-level ACDFs (28.9%) involving C3–C4 (n⫽2), C4– C5 (n⫽4), C5–C6 (n⫽2) and C6–C7 (n⫽3) and 32 two-level ACDFs (71.1%) involving C3–C5 (n⫽2), C4–C6 (n⫽7) and C5–C7 (n⫽18). In all patients where two-level ACDFs were performed, contiguous levels were fused. Smokers represented 26.7% and 28.9% of Group 1 and Group 2, respectively. All smokers were urged to adhere to a smoking cessation program before and after surgery. Work-related injuries involved 38.0% of Group 1 and 28.9% of Group 2. All ACDFs were performed using cervical traction, neuromonitoring and somatosensory evoked potentials. A standard Smith-Robinson anteromedial left-sided cervical approach was used in all cases [31]. After adequate exposure, intraoperative radiographs were obtained to confirm the appropriate level(s). Discectomies were performed by entering into the disc space with a number 15 scalpel blade at both the superior and inferior borders, followed by removal of the disc material sequentially with pituitary rongeurs and curettes. An intervertebral body spreader was carefully placed to allow for distraction of the disc space. Overhanging anterior osteophytes were removed to provide unobstructed access to the intervertebral disc space. In both groups, the decompression was taken to the posterior longitudinal ligament posteriorly and laterally out to the uncovertebral joints on both sides. In all patients a complete discectomy was performed and all articular cartilage was removed preserving the bony end plates. At this point, in patients undergoing direct uncovertebral joint decompression, a small curved microcurette is used to detach the posterior longitudinal ligament from the caudad vertebral body. In this plane, the curette is gradually advanced laterally over to the posterior portion of the uncovertebral joint. The safety of this technique is ensured by remaining on bone at all times. Once the uncovertebral joint is reached, the posterior longitudinal ligament is detached. Using loupe magnification, a 1-mm microkerrison punch is
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used to start the direct decompression of the uncovertebral joint. Once adequate space is created with the 1-mm kerrison punch, a 2-mm kerrison punch is used to complete the decompression of the neuroforamen. It is thought that an adequate decompression is obtained once a 2-mm kerrison punch and a nerve hook can be passed easily into the neuroforamen. After this point, both groups underwent fusion and plating. Autograft and allograft options with associated risks were discussed with each patient before surgery, and selection was based on patient preference. In cases where autogenous bone graft was selected, tricortical anterior iliac crest was harvested with a low-speed oscillating saw. Allografts were fresh frozen, vacuum-sealed, nonradiated tricortical grafts that were supplied by a single bone bank and defrosted in saline for 20 minutes before use. All grafts were fashioned in a typical Smith-Robinson formation. The disc spaces were measured with trials and the appropriate size bone graft selected. In patients who underwent indirect decompression, the graft sizes were selected to provide an additional 2 to 3 mm of distraction over the preoperative disc height [18]. The tricortical grafts were then inserted with the cortical surface anteriorly and countersunk 2 mm from the anterior vertebral border. Rigid anterior cervical plate fixation was applied in all cases and consisted of 37 PEAK (Depuy-Acromed, Rayham, MA), 30 Orion (Sofamor-Danek, Memphis, TN), 28 Atlantis (Sofamor-Danek, Memphis, TN), 3 AO Synthes, 8 VueLock EBI (Biomet, Warsaw, IN), 2 Codman (Johnson & Johnson, New Brunswick, NJ) and 1 Reflex (Stryker, Kalamazoo, MI). Selection of plate type was determined by generational design availability at the time of surgery and based on the surgeon’s preference. Before application of the plate, the anterior cervical surfaces of the operative vertebrae were burred down and each plate was contoured to accommodate vertebral convexity and obtain desired cervical lordosis and maximal bone–plate contact. Surgical midline was established based on anatomic landmarks. To avoid penetration into the spinal canal and cranial and caudal intervertebral disc spaces, unicortical screw purchase was achieved using a 14- or 16-mm drill guide directed toward the midline and parallel to the vertebral end plate. Meticulous hemostasis was achieved, and the incision was closured in layers over a deep drain. Postoperatively, all patients were placed in a soft collar for 3 to 4 weeks, the neck exercises were initiated, and gradual return to normal activity was permitted as tolerated. Follow-up lateral neutral, flexion and extension radiographs were used to assess fusion. Blinded analyses of plain radiographs were conducted (mean, 12 months; range, 3 to 55 months) to assess for evidence of fusion in both groups. Fusion had occurred if a bony bridge incorporated the graft and adjacent end plates and there was no evidence of motion or radiolucencies around the instrumentation. Patient charts on latest follow-up and prospective cervical spine outcome questionnaires and a modified outcomes questionnaire
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were used to assess patient function [32]. Clinical outcomes were reported as excellent, good, fair or poor (mean, 23 months; range, 12 to 60 months) based on Odom’s criteria (Table 1) [4]. Excellent and good outcomes were considered satisfactory. The data were collected and stored in a spreadsheet format and analyzed by SPSS statistical software. Statistical tests used to analyze different data parameters for statistical significance included analysis of variance, t tests and chi-squared analyses. Statistical significance was established at p⬍.05.
Table 2 Clinical outcome of instrumented one- and two-level anterior cervical discectomy and fusion, patients with or without direct decompression of the uncovertebral joints Direct uncovertebral joint decompression Yes
No
Odom’s score
Percent
n
Percent
n
Excellent Good Fair Poor Total count
26.8% 57.7% 12.7% 2.8% 100%
19 41 9 2 71
23.7% 60.5% 15.8% 0.0% 100%
9 23 6 0 38
Results An overall fusion rate of 97.2% was obtained for this series of one- and two-level ACDF patients with rigid anterior plate fixation. A 100% solid fusion rate was achieved in Group 2 (indirect decompression with disc space distraction), and a 95.8% fusion rate was noted in Group 1 (direct uncovertebral joint decompression). Fusion was achieved in 96.1% of autografts and in 98.3% of allografts. Fusion was noted in 96.7% of smokers and 97.2% of nonsmokers. Nonunion was noted in two patients who were nonsmokers at the level of C5–C6 with one-level instrumented ACDF and autograft. Nonunion was also noted in one two-level instrumented ACDF patient at the level of C4–C6 who was a smoker with allograft and developed dysphagia because of a pronounced inferior edge of the plate. Additional complications were noted in one patient in Group 1 who developed respiratory distress after surgery and required reintubation. No other intra- or postoperative clinical or radiographic complications were noted in this patient series. All nonunions were evaluated radiographically at a minimum of 1-year following surgery. Patients were followed clinically for a minimum of 1 year. The average clinical follow-up for all patients in this study was 23 months (range, 12 to 60 months). All nonunions achieved good clinical outcomes. Complete resolution of neck and radiculopathic pain was noted in 26.8% and 23.7% of Group 1 and Group 2, respectively (Table 2). Satisfactory clinical outcomes were achieved in 84.5% and 84.2% for Group 1 and Group 2, respectively. No statistical significance was noted between patients’ demographics, smoking, work-related injuries, operative level, type of graft, occurrence of fusion and presence of uncovertebral joint decompression to variation of clinical outcome (p⬎.05). Table 1 Odom’s clinical outcome ratings Excellent: Good: Fair: Poor:
No complaint referable to cervical disease; able to perform daily occupation without impairment. Intermittent discomfort referable to cervical disease; no significant interference with work. Subjective improvement in symptoms; physical activity significantly impaired Worsening or no improvement.
Discussion Anterior cervical discectomy and fusion was first described by Robinson and Smith in 1955. In their classic description, the original procedure was performed without the removal of the uncovertebral osteophytic spurs [33]. In subsequent modifications, Cloward emphasized that all compressive structures should be addressed and that direct decompression of the offending uncovertebral osteophytes was vital [34]. In response to this, Robinson stated, “Remodeling may well remove such spurs over time following stabilization of the spine and eliminat[e] abnormal mechanical forces, which are associated with spur formation” [5]. Since that time, there has been much debate over the need for direct uncovertebral joint decompression [1,13–17] versus indirect decompression through interbody height distraction [18,19] and osteophyte resorption [1,2,5,19,35,36]. In this current study, similar functional outcomes were found between the patients who underwent direct decompression (Group 1) as compared with those who had indirect decompression through interbody distraction (Group 2). At a mean follow-up of 23 months, excellent or good results occurred in 84.5% (60 of 71) and 84.2% (32 of 38) of Group 1 and Group 2 patients, respectively. Complete resolution of the neck and radicular arm pain was seen in 26.8% (19 of 71) of Group 1 and 23.7% (9 of 38) of Group 2 patients. However, there was no statistically significant difference between the results (p⬍.05). This study further confirms previous work from other authors that in the properly selected patient ACDF is a good surgical option for the treatment of patients with neck pain and cervical radiculopathy [1–7]. In the patients who underwent ACDF without direct uncovertebral joint decompression, the improvement in the radicular symptoms may be secondary to several factors, including indirect decompression through intervertebral disc space distraction and elimination of pathologic motion by achieving a solid arthrodesis. In patients with cervical spondylosis, the uncovertebral joint osteophytes impinge on nerve roots as they exit behind the uncovertebral joint [8]. Anatomically, the posterior aspect of the uncovertebral joint forms the anterior wall of the neuroforamen [8,37], and
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apical osteophytes arising from the uncinate process can result in foraminal stenosis [4,8,9,38]. In addition, disc height settling, as seen during disc degeneration, potentially narrows the neuroforamen in both the superior-inferior direction (foraminal height) and to some degree in the anterior-posterior direction (foraminal width). The associated bulge of the ligamentum flavum, posterior longitudinal ligament and other soft tissue restraints combined with any degree of associated subluxation will contribute to the narrowing of the neuroforamen. Therefore, adequate disc height distraction with restoration of sagittal alignment can potentially increase both foraminal height and width (Fig. 1). This is analogous to the lumbar spine, where a reduction in foraminal height and cross-sectional area is associated with nerve root entrapment and compression [39]. Using cadaveric spines and computed tomography analysis, it has been shown that foraminal cross-sectional area in the cervical spine can be increased during ACDF by increasing the interbody graft height [18]. This increase in foraminal cross-sectional area represents increased space for the exiting nerve root; it may result in improved vascular supply and relieves direct compression on an already compromised nerve. An overall fusion rate of 97.2% was seen in this group of 109 patients, with 95.8% of Group 1 and 100% of Group 2 patients eventually resulting in a solid arthrodesis. In our series, smoking, operative level and type of graft (autograft versus allograft) did not reach statistical significance (p⬍.05) for effecting eventual fusion. Although not statistically significant, all three nonunions occurred in patients who underwent direct uncovertebral joint decompression (Group 1). Two of the patients were plated, one-level ACDF with autograft and nonsmokers. The third nonunion occurred in a smoker who received allograft for plated two-level ACDF. Although various plate types were used in our series, all instrumentation fixation was rigid and assumed a load-bearing role. Furthermore, both allograft and autograft were used in both groups; however, high fusion rates and similar degree of graft settling are associated with rigid anterior plate fixation in one- or multilevel ACDF for both allograft and
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autograft [24,40,41]. Although smoking is also a factor associated with high rates of nonunion in noninstrumented ACDF [42–44], the use of instrumentation in ACDF decreases such a risk factor for nonunion [27,28,40,41,45]. As is evident in our series, patients with a history of smoking were urged to follow a smoking cessation program before and after surgery and did not demonstrate a significant difference in fusion rate in comparison to nonsmokers. Although many other factors may contribute to a successful fusion, retention of the uncovertebral joint may play some role. Biomechanically, sequential uncovertebral joint resection results in progressive cervical spine instability, especially in the patient who has undergone a discectomy [37,46,47]. Depending on the cervical level examined, the uncovertebral joint contributes 48% to 60% of the total stability at each level, with the posterior aspect of the uncovertebral joint providing greatest stability. Therefore, the standard cervical foraminotomy that decompresses the posterior portion of the uncovertebral joint, just anterior to the neuroforamen, actually removes the most stabilizing portion of the joint [37]. Critics argue that the importance of the role of the uncovertebral joint in cervical stability is irrelevant in the presence of a solid fusion. On this point, the authors would agree. However, if stability remains a vital component in achieving a successful fusion, then instability and motion at the graft site would lower ultimate fusion rate. If equivalent functional outcomes can be achieved without direct decompression, then preservation of the uncovertebral joint would theoretically provide the optimal environment in which to encourage a successful fusion. Overall complication rates associated with ACDF have been reported to range from 0 to 17% [35,48–56]. In our series there were two complications for an overall complication rate of 1.8%. One patient developed a transient dysphagia secondary to prominent spinal instrumentation. The second patient developed respiratory distress in the immediate perioperative period and required reintubation. Although both cases occurred in patients from Group 1, neither complication was attributed to the fact that the uncovertebral joint was directly decompressed.
Fig. 1. Preoperative schematic drawing of a parasagittal section demonstrating loss of the intervertebral disc height with subsequent neuroforaminal stenosis and nerve root impingement from uncovertebral joint osteophytes and loss of sagittal alignment. Postoperatively, indirect decompression is achieved through disc space distraction and sagittal realignment.
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Although the majority of complications are minor, major complications have been reported. In particular, because of the proximity of the vertebral artery to the uncovertebral joint, vertebral lacerations during foraminotomies or removal of the posterior lateral quadrant of the vertebral body have been reported [54,57]. Although no vascular injuries occurred in this series, the reported rate ranges from 0.3% to 0.5% during anterior cervical spine surgery. More importantly, although infrequent, when they do occur, the consequences can be catastrophic, resulting in significant ischemia, neurologic injury and potentially death [49,51,53,57,58]. In summary, in this current series the overall fusion rate was 97.2%, with good to excellent clinical results occurring in 84.4% of patients who underwent direct uncovertebral joint decompression and in patients with indirect decompression by distraction and leaving the uncovertebral joint intact. Indirect foraminal decompression through distraction remains somewhat controversial during ACDF. However, sacrificing the uncovertebral joint can increase operative time and potentially increase complication rates. This study demonstrates that ACDF with indirect decompression can provide good clinical results for neck pain with cervical radiculopathy. As a result, the authors do not recommend routine direct decompression of the uncovertebral joint during ACDF. However, the authors emphasize that indirect decompression is not a substitute for careful patient selection and proper surgical technique. A thorough and complete discectomy and proper disc space distraction of 2 to 3 mm is still required in order to achieve appropriate distraction and the eventual fusion necessary to obtain a good clinical outcome.
References [1] Bohlman HH, Emery SE, Goodfellow DB, Jones PK. Robinson anterior cervical discectomy and arthrodesis for cervical radiculopathy. J Bone Joint Surg [Am] 1993;75:1298–307. [2] Connolly ES, Seymour RJ, Adams JE. Clinical evaluation of anterior cervical fusions for degenerative cervcial disc disease. J Neurosurg 1965;23:431–7. [3] Dillin W, Boothe R, Cluckler J, Balderston R, Simeone F, Rothman R. Cervical radiculopathy. Spine 1986;11:988–91. [4] Odom G, Finney W, Woodhall B. Cervical disc lesions. JAMA 1958; 166:23–8. [5] Robinson RA, Walker AE, Ferlic DC, Wieking DK. The results of anterior interbody fusion of the cervical spine. J Bone Joint Surg [Am] 1962;44:1569–87. [6] White AA, Southwick W, Deponte R, Gainor JW, Hardy R. Relief of pain by anterior cervical spine fusion for spondylosis. A report of sixty-five patients. J Bone Joint Surg [Am] 1973;55:525–34. [7] Whitecloud T, Sherk H. Modern alternatives and techniques for onelevel discectomy and fusion. Clin Orthop Rel Res 1999;359:67–76. [8] Ebraheim NA, Jike L, Biyani A, Brown JA, Yeasting RA. Anatomic considerations for uncovertebral involvement in cervical spondylosis. Clin Orthop Rel Res 1997;334:200–6. [9] Tanaka N, Fujimoto Y, An H, Ikuta Y, Yasuda M. The anatomic relation among the nerve roots, intervertebral foramina, and intervertebral discs of the cervical spine. Spine 2000;25:286–91.
[10] Emery SE. Cervical disc disease and cervical spondylosis. In: An HS, editor. Principles and techniques of spine surgery. Philadelphia: Williams and Wilkins, 1998:401–12. [11] Fellrath RF, Hanley EN. Anterior cervical discectomy and arthrodesis for radiculopathy. In: Clark CR, editor. The cervical spine. Philadelphia: Lippincott-Raven, 1998:785–98. [12] Fischgrund J, Herkowitz HH. Anterior surgical procedures for cervical spondylotic radiculopathy and myelopathy. In: An HS, Simpson JM, editors. Surgery of the cervical spine. Philadelphia: Williams and Wilkins, 1994:195–212.Philadelphia: Williams and Wilkins: 1994: 195–212. [13] Brigham CD, Tsahakis PJ. Anterior cervical foraminotomy and fusion. Spine 1995;20:766–70. [14] Davis RA. A long-term outcome study of 170 surgically treated patients with compressive cervical radiculopathy. Surg Neurol 1996;46: 523–33. [15] Hakuba A. Transuncodiscal approach: a combined anterior and lateral approach to cervical discs. J Neurosurg 1976;45:284–91. [16] Jho HD. Microsurgical anterior cervical foraminotomy for radiculopathy: a new approach to cervical disc herniation. J Neurosurg 1983;13: 504–12. [17] Sonntag VKH, Han PP, Vishteh AG. Anterior cervical discectomy. Neurosurgery 2001;49:909–12. [18] An HS, Evanich CJ, Nowicki BH, Haughton VM. Ideal thickness of Smith-Robinson graft for anterior cervical fusion. Spine 1993;18: 2043–7. [19] Bayley JC, Yoo JU, Kruger DM, Schlegel J. The role of distraction in improving the space available for the cord in cervical spondylosis. Spine 1995;20:771–5. [20] Emery SE, Bolesta MJ, Banks MA, Jones PK. Robinson anterior cervical fusion comparison of the standard and modified techniques. Spine 1994;19:660–3. [21] Jenis LG, An HS, Simpson JM. A prospective comparison of the standard and reverse Robinson cervical grafting techniques: radiographic and clinical analyses. J Spinal Disord 2000;13:369–73. [22] Martin GJJ, Haid RWJ, MacMillian M, Rodts GEJ, Berkman R. Anterior cervical discectomy with freeze-dried fibula allograft: overview of 317 cases and literature review. Spine 1999;24:852–9. [23] Kaiser MG, Haid RWJ, Subach BR, Barnes B, Rodts GEJ. Anterior cervical plating enhances arthrodesis after discectomy and fusion with cortical allograft. Neurosurgery 2002;50:229–36. [24] Samartzis D, Shen FH, An HS. Effects of rigid plating on healing of anterior cervical grafts: preliminary results with the PEAK polyaxial plating system. Paper presented at: World Spine II; August 10–13, 2003; Chicago, IL. [25] Samartzis D, Shen FH, Matthews D, Yoon S, Goldberg E, An HS. Comparison of allograft to autograft in multilevel anterior cervical discectomy and fusion with rigid plate fixation. Spine J 2003;3:451–9. [26] Troyanovich SJ, Stroink AR, Kattner KA, Dornan WA, Gubina I. Does anterior plating maintain cervical lordosis versus conventional fusion techniques? A retrospective analysis of patients receiving single-level fusions. J Spinal Disord 2002;15:69–74. [27] Wang JC, McDonough PW, Endow KK, Delamarter RB. Increased fusion rates with cervical plating for two-level anterior cervical discectomy and fusion. Spine 2000;25:41–5. [28] Wang JC, McDonough PW, Endow KK, Kanim LE, Delamarter RB. The effect of cervical plating on single-level anterior cervical discectomy and fusion. J Spinal Disord 1999;12:467–71. [29] Wang JC, McDonough PW, Kanim LEA, Endow KK, Delamarter RB. Increased fusion rates with cervical plating for three-level anterior cervical discectomy and fusion. Spine 2001;26:643–7. [30] Bohlman HH, Emery SE. The pathophysiology of cervical spondylosis and myelopathy. Spine 1988;13:843–6. [31] Smith G, Robinson RA. The treatment of certain cervical spine disorders by anterior removal of the intervertebral disc and interbody fusion. J Bone Joint Surg [Am] 1958;40:607–24.
F.H. Shen et al. / The Spine Journal 4 (2004) 629–635 [32] BenDebba M, Heller J, Ducker TB, Eisinger JM. Cervical spine outcomes questionnaire: its development and psychometric properties. Spine 2002;27:2116–23. [33] Robinson R, Smith G. Anterolateral cervical disc removal and interbody fusion for cervical disc syndrome. Bull Johns Hopkins Hosp 1955;96:223–4. [34] Cloward RB. The anterior approach for removal of ruptured cervical discs. J Neurosurg 1958;15:602–14. [35] DePalma AF, Rothman R, Lewinneck G, Canale ST. Anterior interbody fusion for cervical disc degeneration. Surg Gynecol Obstet 1972;134:755–8. [36] Gore DR, Sepic SB. Anterior cervical fusion for degenerated or protruded discs. A review of one hundred forty-six patients. Spine 1984; 9:667–71. [37] Kotani Y, McNulty P, Abumi K, Cunningham B, Kaneda K, McAfee P. The role of anteromedial foraminotomy and the uncovertebral joints in the stability of the cervical spine: a biomechanical study. Spine 1998;23:1559–65. [38] MacNab I. Cervical spondylosis. Clin Orthop 1975;109:69–77. [39] Hasegawa T, An HS, Haughton VM, Nowicki BH. Lumbar foraminal stenosis: critical heights of the intervertebral discs and foramina. A cryomicrotome study in cadavera. J Bone Joint Surg [Am] 1995;77: 32–8. [40] Samartzis D, Lyon C, Phillips M, Goldberg EJ, An HS. Does rigid instrumentation increase the fusion rate in one-level anterior discectomy and fusion? Spine J 2004 (in press). [41] Samartzis D, Shen FH, Matthews D, Yoon S, Goldberg EJ, An HS. Comparison of allograft to autograft in multilevel anterior cervical discectomy and fusion with rigid plate fixation. Spine J 2003;3:451–9. [42] An HS, Simpson JM, Glover JM, Stephany J. Comparison between allograft plus demineralized bone matrix versus autograft in anterior cervical fusion. A prospective multicenter study. Spine 1995;15: 2211–6. [43] Cauthen JC, Kinard RE, Vogler JB, et al. Outcome analysis of noninstrumented anterior cervical discectomy and interbody fusion in 348 patients. Spine 1998;23:188–92. [44] Hilibrand AS, Fye MA, Emery SE, Palumbo MA, Bohlman HH. Impact of smoking on the outcome of anterior cervical arthrodesis with interbody or strut-grafting. J Bone Joint Surg Am 2001;83A:668–73.
635
[45] Bose B. Anterior cervical instrumentation enhances fusion rates in multilevel reconstruction in smokers. J Spinal Disord 2001;14:3–9. [46] Chen T-Y, Crawford NR, Sonntag VKH, Dickman C. Biomechanical effects of progressive anterior cervical decompression. Spine 2001; 26:6–13. [47] White AA, Panjabi MM. Kinematics of the spine. In: White AA, Panjabi MM, editors. Clinical biomechanics of the Spine, 2nd ed. Philadelphia: J.B. Lippincott, 1990:85–126. [48] Flynn TB. Neurologic complications of anterior cervical interbody fusion. Spine 1982;7:536–9. [49] Golfinos JG, Dickman CA, Zabramski JM, Sonntag VLH, Spetzler RF. Repair of vertebral artery injury during anterior cervical decompression. Spine 1994;19:2552–6. [50] Herkowitz HH. The surgical management of cervical spondylotic radiculopathy and myelopathy. Clin Orthop 1989;239:94–108. [51] Pait T, Killefer J, Arnautovi K. Surgical anatomy of the anterior cervical spine: the disc space, vertebral artery, and associated bony structures. Neurosurgery 1996;39:769–75. [52] Shinomiya K, Okawa A, Nakao K, et al. Morphology of C5 ventral rootlets as part of dissociated motor loss of deltoid muscle. Spine 1994;19:2501–4. [53] Shintani A, Zervas NT. Consequences of ligation of the vertebral artery. J Neurosurg 1972;36:447–50. [54] Smith MD, Emery SE, Dudley A, Murray KJ, Leventhal M. Vertebral artery injury during anterior decompression of the cervical spine. A retrospective review of ten patients. J Bone Joint Surg [Br] 1993; 75:410–5. [55] Weinberg PE, Flom RA. Traumatic vertebral arteriovenous fistula. Surg Neurol 1973;1:162–7. [56] Whitecloud TS. Complications of anterior cervical fusion. American Academy of Orthopaedic Surgeons, Instructional Course Lectures, vol. 27. St. Louis: CV Mosby, 1978. [57] Curylo L, Mason H, Bohlman H, Yoo J. Tortuous course of the vertebral artery and anterior cervical decompression. Spine 2000; 25:2860–4. [58] Milne N. The role of zygapophyseal joint orientation and uncinate process in controlling motion in the cervical spine. J Anat 1991; 178:189–201.