Does rigid instrumentation increase the fusion rate in one-level anterior cervical discectomy and fusion?

Abstract

Background context

Although plate fixation enhances the fusion rate in multilevel anterior cervical discectomy and fusion (ACDF), debate exists regarding the efficacy of nonplating to rigid plate fixation in one-level ACDF.

Purpose

To determine the efficacy of nonplating to rigid plate fixation in regards to fusion rate and clinical outcome in patients undergoing one-level ACDF with autograft.

Study design

A review of 69 consecutive patients who underwent one-level ACDF with autograft and with or without rigid anterior cervical plate fixation.

Patient sample

Sixty-nine patients who underwent one-level ACDF (mean age, 45 years) were evaluated for radiographic evidence of fusion (mean, 14 months) and for clinical outcome. All patients received tricortical iliac crest autografts. Disc space distraction was 2 mm, the grafts were inserted with the cortical surface positioned anteriorly, and each graft was countersunk 2 mm from the anterior vertebral border. Thirty-eight patients underwent nonplated ACDF and 31 patients underwent plated ACDF. Eighteen Orion (Sofamor-Danek, Memphis, TN), eight Atlantis (Sofamor-Danek) and five PEAK polyaxial (Depuy-Acromed, Rayham, MA) anterior cervical plating systems were used. Rigid plate fixation was used in all patients with instrumentation. Postoperatively, hard collars were worn 6 to 8 weeks in nonplated patients and soft collars were worn for 3 to 4 weeks in plated patients. Twenty-four patients were smokers (54.2% nonplating; 45.8% plating) and work-related injuries entailed 23 patients (47.8% nonplating; 52.2% plating).

Outcome measures

Fusion was assessed based on last follow-up of lateral neutral, flexion and extension radiographs. Radiographs were evaluated blindly to assess fusion and instrumentation integrity between nonplated and plated patients. Clinical outcomes were assessed with the Cervical Spine Outcomes Questionnaire and also assessed on last follow-up as excellent, good, fair or poor based on Odom's criteria.

Methods

Fusion rate and postoperative clinical outcome were assessed in 69 patients who underwent one-level ACDF with autograft and with or without rigid anterior plate fixation. Additional risk factors were also analyzed. Statistical significance was established at p<.05.

Results

Sixty-six patients (95.7%) achieved a solid fusion (100% nonplated; 90.3% plated). Nonunions occurred in three patients (1 smoker; 2 nonsmokers) with Orion instrumentation. Slight screw penetration into the involved and uninvolved interbody spaces occurred in one patient who was a nonsmoker and did not achieve fusion. One superficial cervical wound infection was noted in a nonplated patient. No other intraoperative or postoperative complications were noted. No statistically significant difference was noted between nonplating to rigid plating upon fusion rate (p>.05). All nonunions occurred at the C5–C6 level. Mean estimated intraoperative blood loss was significantly greater in plated patients (p=.043). Revision surgery involved 9.7% of the plated patients, whereas none of the nonplated patients required reoperation. Postoperative clinical outcome was assessed in all patients (mean, 21 months). Excellent results were noted in 18.8%, good results in 72.5% and fair results in 8.7% of the patients. Nonunion patients reported satisfactory clinical outcome. No statistical significance was noted between clinical outcome of fused and nonfused patients, the presence of a work-related injury and the use of plating (p>.05). Demographics and history of smoking were not factors influencing fusion or clinical outcome in this series (p>.05). The effect on fusion by various plate types could not be discerned from this study.

Conclusion

A 100% and 90.3% fusion rate was obtained for one-level nonplated and plated ACDF procedures with autograft, respectively. The effects of smoking or level of fusion could not be discerned from these one-level cases. Excellent and good clinical outcome results were obtained for 91.3%. Nonplating or rigid plate fixation for ACDF in properly selected patients to treat radiculopathy with or without myelopathy has a high fusion rate and yields a satisfactory clinical outcome. Although controversy exists as to the efficacy of rigid plate fixation in one-level ACDF, solid bone fusion can be adequately obtained without plate fixation and instrumentation-related complications can be avoided. In line with the literature, plate fixation should be reserved for patients unwilling or unable to wear a hard orthosis postoperatively for an extended period of time or for those patients who seek a quicker return to normal activities. Proper patient selection, meticulous operative technique and postoperative care is essential to promote optimal graft-host incorporation.

Introduction

Anterior cervical discectomy and fusion (ACDF) is an established procedure for the treatment of cervical degenerative disease. Although a successful procedure, the risk of nonunion and further graft complications is a concern in both one-level and multilevel constructs [1], [2], [3], [4], [5], [6], [7], [8]. In an effort to optimize fixation of the graft–host interface, promote successful fusion, maintain cervical alignment and enhance postoperative outcome, the application of an anterior cervical plating device has gained widespread acceptance and has evolved to include rigid, semirigid and dynamic fixation designs. Although the optimal plate type has been scrutinized throughout the years, it has been postulated that rigid or semi-rigid anterior cervical plating acts as a load-bearing device to promote ideal fusion of interbody grafts but allowing minimal to no graft settling [9]. In contrast, dynamic plate systems promote load sharing and graft settling, but the construct stability is generally inferior [10], [11], [12], [13].

In multilevel ACDFs, studies have demonstrated that rigid plate fixation dramatically increases fusion rates [6], [14], [15]. However, the efficacy of rigid plate fixation on interbody fusion in one-level ACDF is not as clear in comparison to multilevel constructs. In studies that directly compare instrumented with noninstrumented one-level ACDF, some authors have reported higher union rates in plated cases [14], [16], whereas others report similar rates [3]. Although such studies have attempted to elucidate on the fusion rate in one-level ACDF with or without plating, they contain various drawbacks that mainly entail no delineation on type of plate-screw fixation used [14], [16], insufficient patient size [3], inconsistency in graft material and use of instrumentation [17] or implementation of historical cohorts and allograft [14]—graft material the cellular, dimensional and biomechanical properties of which vary and could adversely affect the healing process in contrast to the gold standard of autograft. It has also been suggested that rigid plate fixation in one-level ACDF may actually decrease fusion rates and result in inferior clinical outcomes by increasing stress shielding and hold the graft in excessive distraction, thus preventing appropriate graft settling and eventual graft-host incorporation [3], [18], [19], [20], [21].

Various local and systemic risk factors have also been associated with various spine procedures that may contribute to nonunion and poor clinical outcome [22], [23], [24], [25], [26], [27], [28], [29], [30]. The role of smoking and its relationship to the development of nonunion has primarily received attention in lumbar spine procedures [26], [31], [32], [33], [34], [35], [36], [37]. Addressing the role of smoking as a risk factor in anterior cervical spine surgery with or without anterior cervical plating has rarely been reported [16], [38], [39], especially as it pertains to one-level ACDF with or without plate fixation [16].

Although rigid plate fixation increases fusion rate in multilevel ACDF cases [6], [14], [15], the efficacy of rigid plate fixation in one-level ACDF is controversial. The purpose of this study is to evaluate fusion rate in patients undergoing one-level ACDF with autograft and with or without rigid anterior cervical plate fixation. Potential risk factors affecting osseous union and clinical outcome are secondary aspects that will also be addressed.