Biomechanical study on the effect of cervical spine fusion on adjacent-level intradiscal pressure and segmental motion

Reoperation rates and patient-reported outcomes of single and two-level anterior cervical discectomy and fusion

INTRODUCTION

The purposes of this study were to identify the 2 year rate of reoperation and determine patient-reported outcomes after elective one- and two-level anterior cervical discectomy and fusion (ACDF) with structural allograft and anterior plating using indications similar to cervical disc arthroplasty.

MATERIALS AND METHODS

A retrospective chart review was performed on 116 consecutive one- and two-level primary ACDF for adult degenerative disease with structural allograft and anterior plating in one surgeon's practice. Patient-reported visual analog score (VAS), Oswestry disability index (ODI) and radiographs, collected prospectively on all operative patients preoperatively and postoperatively at 6 weeks, 3 months, 6 months, 1 year, and 2 years were reviewed. Patient demographics and reoperation rates were obtained from the chart.

RESULTS

One hundred and four patients were identified with a final reoperation rate of 2.9% at a mean final follow-up 2 years (95% CI 17.2-29.0). No reoperations occurred within 90 days. After 1 year, three patients required reoperation. The mean patient-reported outcomes improved (VAS, 6.6 preoperatively to 3.0 at final follow-up and ODI, 24.3 preoperatively to 12.3 at final follow-up). These improvements were statistically significant (p < 0.01). No significant patient risk factors for reoperation were found.

CONCLUSIONS

The rate of reoperation for one- and two-level anterior cervical discectomy and fusion at follow-up was found to be lower than those previously published in the literature quoted for CDA. Arthrodesis continues to demonstrate improvements in patient-reported outcomes.

Long-term follow-up MRI shows no hastening of adjacent segment degeneration following cervical disc arthroplasty

Cervical disc arthroplasty is an established procedure, but studies with data on long-term clinical outcome, reoperation for symptomatic adjacent segment degeneration (sASD), and degenerative changes based on MRI findings are rare. Thus, a file review was performed and patients with complete documentation of neurological status at preoperative, postoperative, 12 month, 3–4 years follow-up including surgical reports for reoperation with a minimum follow-up of 9 years were included. Final follow-up assessment included a physical examination, assessment of pain levels, Odoms criteria, Neck disability index. The degeneration of each cervical segment at preoperative and at final follow-up was assessed using an MRI. Forty-six out of 68 included patients participated, the mean follow-up was 11 (range 9–15) years, at which 71.7% of patients were free of arm pain, 52.2% of patients were free of neck pain, 63% of patients had no sensory dysfunction, and full motor strength was noted in 95.6% of patients. The clinical success rate was 76.1%, the mean NDI was 12%. Overall repeated procedure rate was 17%, the reoperation rate for sASD was 9%, and removal of CDA was performed in 4%. MRI showed progressive degeneration but no significant changes of SDI from preoperative to final follow-up.

Mid- to long-term rates of symptomatic adjacent-level disease requiring surgery after cervical total disc replacement compared with anterior cervical discectomy and fusion: a meta-analysis of prospective randomized clinical trials

Background

Thus far, no meta-analysis focusing on the mid- to long-term incidence of adjacent segment disease requiring surgery after cervical total disc replacement and anterior cervical discectomy and fusion has been published yet. This study aimed to compare mid- to long-term rates of symptomatic adjacent-level disease requiring surgery after cervical disc replacement and anterior cervical fusion.

Methods

A meta-analysis was performed, and only randomized controlled trials with a follow-up period of more than 48 months reporting rates of symptomatic adjacent-level disease requiring surgery after cervical total disc replacement and anterior cervical discectomy and fusion were included.

Results

The analysis revealed that the overall rate of symptomatic adjacent-level disease requiring surgery in the cervical disc replacement group was significantly lower than that of the anterior cervical fusion group at 48–120 months’ follow-up. The subgroup analysis of different follow-up periods also yielded the same results. The rate of symptomatic adjacent-level disease requiring surgery in the cervical disc replacement group using unrestricted prosthesis was significantly lower than that of the anterior cervical fusion group (p < 0.001); however, the cervical disc replacement group using semi-restricted prosthesis showed no statistical difference compared with the fusion group.

Conclusions

Our review suggests that cervical disc replacement is preferable to anterior cervical fusion in reducing the incidence of symptomatic adjacent-level disease requiring surgery at mid- to long-term follow-up. A review of the literature also demonstrated that randomized controlled trials investigating the rate of symptomatic adjacent-level disease requiring surgery were insufficient; therefore, studies focusing on this subject with longer-term follow-up are warranted.

Reliability and scientific use of a surgical planning software for anterior cervical discectomy and fusion (ACDF)

PURPOSE

Software-based planning of a spinal implant inheres in the promise of precision and superior results. The purpose of the study was to analyze the measurement reliability, prognostic value, and scientific use of a surgical planning software in patients receiving anterior cervical discectomy and fusion (ACDF).

METHODS

Lateral neutral, flexion, and extension radiographs of patients receiving tailored cages as suggested by the planning software were available for analysis. Differences of vertebral wedging angles and segmental height of all cervical segments were determined at different timepoints using intraclass correlation coefficients (ICC). Cervical lordosis (C2/C7), segmental heights, global, and segmental range of motion (ROM) were determined at different timepoints. Clinical and radiological variables were correlated 12 months after surgery.

RESULTS

282 radiographs of 35 patients with a mean age of 53.1 ± 12.0 years were analyzed. Measurement of segmental height was highly accurate with an ICC near to 1, but angle measurements showed low ICC values. Likewise, the ICCs of the prognosticated values were low. Postoperatively, there was a significant decrease of segmental height (p < 0.0001) and loss of C2/C7 ROM (p = 0.036). ROM of unfused segments also significantly decreased (p = 0.016). High NDI was associated with low subsidence rates.

CONCLUSIONS

The surgical planning software showed high accuracy in the measurement of height differences and lower accuracy values with angle measurements. Both the prognosticated height and angle values were arbitrary. Global ROM, ROM of the fused and intact segments, is restricted after ACDF.

Adjacent segment degeneration following ProDisc-C total disc replacement (TDR) and anterior cervical discectomy and fusion (ACDF): does surgeon bias effect radiographic interpretation?

PURPOSE

Many investigators have reported the financial conflicts of interest (COI), which could result in potential bias in the reporting of outcomes for patients undergoing total disc replacement (TDR) rather than anterior cervical discectomy and fusion (ACDF). This bias may be subconsciously introduced by the investigator in a non-blinded radiographic review. The purpose of this study was to determine if bias was present when a group of spine specialists rated adjacent segment degeneration (ASD) following cervical TDR or ACDF.

METHODS

Potential bias in the assessment of ASD was evaluated through the reviews of cervical radiographs (pre- and 6 years post-operative) from patients participating in the ProDisc-C FDA trial (ProDisc-C IDE #G030059). The index level was blinded on all radiographs during the first review, but unblinded in the second. Five reviewers (a radiologist, two non-TDR surgeons, and two TDR surgeons), two of whom had a COI with the ProDisc-C trial sponsor, assessed ASD on a three point scale: yes, no, or unable to assess. Intra- and inter-rater reliabilities between all raters were assessed by the Kappa statistic.

RESULTS

The intra-rater reliability between reviews was substantial, indicating little to no bias in assessing ASD development/progression. The Kappa statistics were 0.580 and 0.644 for the TDR surgeons (p < 0.0001), 0.718 and 0.572 for the non-TDR surgeons (p < 0.0001), and 0.642 for the radiologist (p < 0.0001). Inter-rater reliability for the blinded review ranged from 0.316 to 0.607 (p < 0.0001) and from 0.221 to 0.644 (p < 0.0001) for the unblinded review.

CONCLUSIONS

The knowledge of the surgical procedure performed did not bias the assessment of ASD.

Anterior cervical discectomy and fusion (ACDF) versus cervical disc arthroplasty (CDA) for two contiguous levels cervical disc degenerative disease: a meta-analysis of randomized controlled trials

BACKGROUND

Anterior cervical discectomy and fusion (ACDF) has been considered as a gold standard for symptomatic cervical disc degeneration (CDD), which may result in progressive degeneration of the adjacent segments. The artificial cervical disc was designed to reduce the number of lesions in the adjacent segments. Clinical studies have demonstrated equivalence of cervical disc arthroplasty (CDA) for anterior cervical discectomy and fusion in single segment cervical disc degeneration. But for two contiguous levels cervical disc degeneration (CDD), which kind of treatment method is better is controversial.

PURPOSE

To evaluate the clinical effects requiring surgical intervention between anterior cervical discectomy and fusion (ACDF) and cervical disc arthroplasty (CDA) at two contiguous levels cervical disc degeneration.

METHODS

We conducted a comprehensive search in multiple databases, including PubMed, Cochrane Central Register of Controlled Trials, EBSCO and EMBASE. We identified that six reports meet inclusion criteria. Two independent reviewers performed the data extraction from archives. Data analysis was conducted with RevMan 5.3.

RESULTS

After applying inclusion and exclusion criteria, six papers were included in meta-analyses. The overall sample size at baseline was 650 patients (317 in the TDR group and 333 in the ACDF group). The results of the meta-analysis indicated that the CDA patients had significant superiorities in mean blood loss (P < 0.00001, standard mean differences (SMD) = -0.85, 95 % confidence interval (CI) = -1.22 to -0.48); reoperation (P = 0.0009, risk ratio (RR) = 0.28, 95 % confidence interval (CI) = 0.13-0.59), adjacent segment degeneration (P < 0.00001, risk ratio (RR) = 0.48, 95 % confidence interval (CI) = 0.40-0.58) and Neck Disability Index (P = 0.002, SMD = 0.31, 95 % CI = 0.12-0.50). No significant difference was identified between the two groups regarding mean surgical time (P = 0.84, SMD = -0.04, 95 % CI = -0.40 to 0.32), neck and arm pain scores (P = 0.52, SMD = 0.06, 95 % CI = -0.13 to 0.25) reported on a visual analog scale and rate of postoperative complications [risk ratio (RR) = 0.79; 95 % CI = 0.50-1.25; P = 0.31]. The CDA group of sagittal range of motion (ROM) of the operated and adjacent levels, functional segment units (FSU) and C2-7 is superior to ACDF group by radiographic data of peroperation, postoperation and follow-up.

CONCLUSION

We can learn from this meta-analysis that the cervical disc arthroplasty (CDA) group is equivalent and in some aspects has more significant clinical outcomes than the ACDF group at two contiguous levels CDD.

Cervical spine alignment in disc arthroplasty: should we change our perspective?

PURPOSE

The alignment at the cervical spine has been considered a determinant of degeneration at the adjacent disc, but this issue in cervical disc replacement surgery is poorly explored and discussed in this patient population. The aim of this systematic review is to compare anterior cervical fusion and total disc replacement (TDR) in terms of preservation of the overall cervical alignment and complications.

METHODS

A systematic review of the current literature was performed, together with the evaluation of the methodological quality of all the retrieved studies.

RESULTS

In most of the retrieved studies, a tendency towards a more postoperative kyphotic alignment in TDR was reported. The reported mean complication rate was of 12.5 % (0-66.2 %). Complications associated with cervical prosthesis included heterotopic ossification, device migration, mechanical instability, failure, implant removal, reoperations and revision.

CONCLUSIONS

Even though cervical disc arthroplasty leads to similar outcomes compared to arthrodesis in the middle term follow-up, no evidence of superiority of cervical TDR is available up to date. We understand that the overall cervical alignment after TDR tends towards the loss of lordosis, but only longer follow-up can determine its influence on the clinical results.

Cervical adjacent segment pathology following fusion: Is it due to fusion?

Adjacent segment pathology affects 25% of patients within ten years of anterior cervical diskectomy and fusion (ACDF). Laboratory studies demonstrate fused segments increase adjacent level stress including elevated intradiscal pressure and increased range of motion. Radiographic adjacent segment pathology (RASP) has been associated to ACDF in multiple statistically significant studies. Randomized controlled trials (RCTs) comparing anterior cervical discectomy and arthroplasty (ACDA) and ACDF have confirmed ACDF accelerates RASP. The question of greatest clinical interest is whether ACDA, artificial disc surgery, results in fewer adjacent level surgeries than ACDF. Current RCT follow up results reveal only non statistically significant trends favoring ACDA yet the post operative periods are only two to four years. Statistically significant increased RASP in ACDF patients however is already documented. The RCT patients’ average ages are in the mid forties with an expected longevity of up to forty more years. Early statistically significant increased RASP in the ACDF patients supports our prediction that given sufficient follow up of ten or more years, fusion will lead to statistically significant higher rate of adjacent level surgery compared to artificial disc surgery.