Early results and review of the literature of a novel hybrid surgical technique combining cervical arthrodesis and disc arthroplasty for treating multilevel degenerative disc disease: opposite or complementary techniques?

Biomechanical Effects on the Prostheses and Vertebrae of Three-Level Hybrid Surgery: A Finite Element Study

PURPOSE

Three-level hybrid surgery (HS) consisting of cervical disc arthroplasty (CDA) and anterior cervical discectomy and fusion (ACDF) has been partly used for the treatment of multi-level cervical degenerative disc disease (CDDD). The complications related to the implants and the collapse of the surgical vertebral bodies had been reported in multi-level anterior cervical spine surgery. Thus, this study aimed to explore the biomechanical effects on the prostheses and vertebrae in three-level HS.

METHODS

A FE model of cervical spine (C0-T1) was constructed. Five surgical models were developed. They were FAF model (ACDF-CDA-ACDF), AFA model (CDA-ACDF-CDA), FFF model (three-level ACDF), SF model (single-level ACDF), and SA model (single-level CDA). A 75-N follower load and 1.0-N·m moment was applied to produce flexion, extension, lateral bending, and axial rotation.

RESULTS

Compared with the intact model, the range of motion (ROM) of total cervical spine in FAF model decreased by 34.54%, 54.48%, 31.76%, and 27.14%, respectively, in flexion, extension, lateral bending, and axial rotation, which were lower than those in FFF model and higher than those in AFA model. The ROMs of CDA segments in FAF and AFA models were similar to the intact model and SA model. Compared with the intact model, the ROMs at C3/4 segment in FFF model increased from 5.71% to 7.85%, and increased from 5.31% to 6.81% at C7/T1 segment, following by FAF model, then the FAF model. The maximum interface pressures of the Prestige-LP in FAF model were similar to SA model, however the corresponding values were increased in AFA model. The maximum interface pressures of the Zero-P were increased in FAF and AFA model compared with those in SF and FFF models. The stress was mainly distributed on the screws. In AFA model, the maximum pressures of the ball and trough articulation in superior and inferior Prestige-LP were all increased compared with those in SA and FAF model. In FFF model, the maximum pressures of the vertebrae were higher than those in other models. The stress was mainly distributed on the anterior area of the vertebral bodies.

CONCLUSIONS

HS seemed to be more suitable than ACDF for the surgical treatment of three-level CDDD in consideration of the biomechanical effects, especially for the two-level CDA and one-level ACDF construct. But a more appropriate CDA prosthesis should be explored in the future.

Anterior cervical hybrid constructs reduce superior adjacent segment burden compared to multilevel anterior cervical discectomy and fusion

Background

Traditional surgical treatment for symptomatic cervical degenerative disc disease is anterior cervical discectomy and fusion (ACDF), yet the increased risk of adjacent segment degeneration (ASD) requiring additional surgery exists and may result in limiting long-term surgical success when it occurs. Disc arthroplasty can preserve or restore physiologic range of motion (ROM), decreasing adjacent level stress and subsequent surgery. For patients with multilevel pathology requiring at least a 1-level fusion, interest is growing in anterior cervical hybrid (ACH) surgery as a partial motion-preserving procedure to decrease the adjacent level burden. This radiographic study compares postoperative superior adjacent segment motion between ACH and ACDF. Secondarily, total global motion, construct motion, inferior adjacent segment motion, and sagittal alignment parameters were compared.

Methods

This is a single-center, multi-surgeon, retrospective cohort study of 2- and 3-level ACH and ACDF cases between 2013 and 2021. Degrees of motion were analyzed on flexion/extension views using Cobb angles to measure global (C2-C7) construct and adjacent segment lordosis. Neutral lateral X-rays were analyzed for alignment parameters, including global lordosis, cervical sagittal vertical axis (cSVA), and T1 slope (T1S). Differences were determined by independent t-test and Fisher's exact test.

Results

Of 100 patients, 38% were 2-level cases (47% ACH, 53% ACDF) and 62% were 3-level cases: (52% ACH, 48% ACDF). Postoperatively, superior adjacent segment motion increased with ACDF and decreased with ACH (-1.3°±5.3° ACH, 1.6°±4.6° ACDF, P=0.005). Postoperatively, the ACH group had greater ROM across the construct (16.3°±8.7° ACH, 4.7°±3.3° ACDF, P<0.001) and total global ROM (38.0°±12.8° ACH, 28.0°±11.1° ACDF, P<0.001). ACH resulted in a significant reduction of motion loss across the construct (-10.0°±11.7° ACH, -18.1°±10.8° ACDF, P<0.001). Postoperative alignment restoration was similar between both cohorts (-2.61°±8.36° ACH, 0.04°±12.24° ACDF, P=0.21).

Conclusions

Compared to ACDF, hybrid constructs partially preserved motion across operative levels and had greater postoperative global ROM without increasing superior adjacent segment mobility or sacrificing alignment restoration. This supports the consideration of ACH in patients with multilevel degenerative cervical pathology requiring at least a 1-level fusion and suggests a propensity for long-term success by reducing the superior adjacent segment burden.

Could the different surgical goals of fusion and non-fusion also be achieved in combination within the same patient? Clinical and radiological outcome of hybrid cervical spine surgery

PURPOSE

Hybrid cervical spine surgery (HS) is a novel surgical strategy wherein an artificial disc replacement is done with a cervical fusion nearby with a stand-alone titanium cage to combine the advantages in both procedures. The aim of this study was to evaluate interactions of these devices within the same patient, and to analyze, if the different goal of each implant is accomplished.

METHODS

Thirty-six patients were treated surgically within a non-randomized retrospective study framework with HS. Patients were examined preoperatively followed by clinical and radiological examination at least one year postoperative. Clinical outcome was detected with NDI, VAS arm/neck, pain self-assessment questionnaires and subjective patient satisfaction. Radiological assessments included RoM, segmental lordosis, cervical lordosis of C2-C7, subsidence, ap-migration and heterotopic ossifications (HO) at the cTDR levels.

RESULTS

Statistically significant improvement of all clinical scores was observed (NDI 37.5 to 5.76; VASarm 6.41 to 0.69; VASneck 6.78 to 1.48). Adequate RoM was achieved at cTDR levels. RoM in the ACDF levels was reduced statistically significant (p < 0.001), and solid fusion (> 2°) was achieved in all evaluated fusion level. Global lordosis (C2-C7) increased statistically significant (2.4° to 8.1°). Subsidence and HO at the cTDR levels did not occur.

CONCLUSIONS

HS results in preservation of the segmental motion in the cTDR and fast and solid fusion in the cage cohort simultaneously. Patient safety was proven. In carefully selected cases, HS is a safe and viable treatment option by choosing the right "philosophy" level per level.

Biomechanical analysis of single and multi-level artificial disc replacement (ADR) in cervical spine using multi-scale loadings: A finite element study

Artificial disc replacement (ADR) is a clinical procedure used to diagnose cervical degenerative disc disease, preserving range of motion (ROM) at the fixation level and preventing adjacent segment degeneration (ASD). This study analyzed the biomechanics of ADR by examining range of motion (ROM), stress levels in bone and implants, and strain in the bone-implant interface using multi-scale loadings. The study focused on single- and double-level patients across various loading scales during physiological motions within the cervical spine. Results showed increased ROM in single-level and double-level fixations during physiological loadings, while ROM decreased at the adjacent level of fixation with the intact cervical spine model. The Prodisc-Implant metal endplate experienced a maximum von Mises stress of 432 MPa during axial rotation, confirming the long durability and biomechanical performance of the bone-implant interface.

Segment selection for fusion and artificial disc replacement in the hybrid surgical treatment of noncontiguous cervical spondylosis: a finite element analysis

Introduction: The treatment of skip-level cervical degenerative disease (CDD) with no degenerative changes observed in the intervening segment (IS) is complicated. This research aims to provide a reference basis for selecting treatment approaches for noncontiguous CDD. Methods: To establish accurate finite element models (FEMs), this study included computed tomography (CT) data from 21 patients with CDD (10 males and 11 females) for modeling. The study primarily discusses four cross-segment surgical approaches: upper (C3/4) anterior cervical discectomy and fusion (ACDF) and lower (C5/6) cervical disc arthroplasty (CDA), FA model; upper CDA (C3/4) and lower ACDF (C5/6), AF model; upper ACDF (C3/4) and lower ACDF (C5/6), FF model; upper CDA (C3/4) and lower CDA (C5/6), AA model. An initial axial load of 73.6 N was applied at the motion center using the follower load technique. A moment of 1.0 Nm was applied at the center of the C2 vertebra to simulate the overall motion of the model. The statistical analysis was conducted using STATA version 14.0. Statistical significance was defined as a p value less than 0.05. Results: The AA group had significantly greater ROM in flexion and axial rotation in other segments compared to the FA group (p < 0.05). The FA group consistently exhibited higher average intervertebral disc pressure in C2/3 during all motions compared to the AF group (p < 0.001); however, the FA group displayed lower average intervertebral disc pressure in C6/7 during all motions (p < 0.05). The AA group had lower facet joint contact stresses during extension in all segments compared to the AF group (p < 0.05). The FA group exhibited significantly higher facet joint contact stresses during extension in C2/3 (p < 0.001) and C6/7 (p < 0.001) compared to the AF group. Discussion: The use of skip-level CDA is recommended for the treatment of non-contiguous CDD. The FA construct shows superior biomechanical performance compared to the AF construct.

Restoration of Range of Motion in the Cervical Spine through Single-Segment Artificial Disc Replacement Using the Baguera®C Prosthesis

Background: Anterior cervical discectomy and fusion (ACDF) is a standard procedure for degenerative diseases of the cervical spine, providing nerve decompression and spinal stabilization. However, it limits cervical spine motility, restricts fused segment activity, and may lead to adjacent degeneration. Cervical disc arthroplasty (CDA) is an accepted alternative that preserves the structure and flexibility of the cervical spine. This study aimed to explore the dynamic changes in the range of motion (ROM) of the cervical spine after CDA using a viscoelastic artificial disc, as well as the factors affecting mobility restoration. Methods: A retrospective analysis was conducted on 132 patients who underwent single-level anterior cervical discectomy and CDA from January 2015 to June 2022. Result: Analysis of data from 132 patients revealed a significant improvement in clinical outcomes. The mean ROM of C2-C7 and functional spinal unit (FSU) segments significantly increased from 2 to 36 months post-operatively. Cervical spine flexibility was preserved and enhanced after prosthesis implantation. However, it took six months for the cervical spine motility to stabilize. In addition, sex and age were found to impact motility restoration, with female and younger patients exhibiting larger ROMs post-surgery. Additionally, CDA at the C5-C6 level resulted in the greatest increase in ROM, potentially improving overall kinematic ability. Conclusions: Single-segment artificial disc arthroplasty effectively restores the ROM in degenerative cervical spine conditions.

The Evidence for the Use of Osteobiologics in Hybrid Constructs (Anterior Cervical Discectomy and Fusion and Total Disc Replacement) in Multilevel Cervical Degenerative Disc Disease: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVE

Examine the clinical evidence for the use of osteobiologics in hybrid surgery (combined anterior cervical discectomy and fusion (ACDF) and total disc replacement (TDR)) in patients with multilevel cervical degenerative disc disease (DDD).

METHODS

PubMed and Embase were searched between January 2000 and August 2020. Clinical studies investigating 18-80 year old patients with multilevel cervical DDD who underwent hybrid surgery with or without the use of osteobiologics were considered eligible. Two reviewers independently screened and assessed the identified articles. The methodological index for non-randomized studies (MINORS) tool and the risk of bias (RoB 2.0) assessment tool were used to assess risk of bias. The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) was used to evaluate quality of evidence across studies per outcome.

RESULTS

Eleven studies were included. A decrease in cervical range of motion was observed in most studies for both the hybrid surgery and the control groups consisting of stand-alone ACDF or TDR. Fusion rates of 70-100% were reported in both the hybrid surgery and control groups consisting of stand-alone ACDF. The hybrid surgery group performed better or comparable to the control group in terms of adjacent segment degeneration. Studies reported an improvement in visual analogue scale for pain and neck disability index values after surgery compared to preoperative scores for both treatment groups. The included studies had moderate methodological quality.

CONCLUSIONS

There is insufficient evidence for assessing the use of osteobiologics in multilevel hybrid surgery and additional high quality and controlled research is deemed essential.

AO Spine Guideline for the Use of Osteobiologics (AOGO) in Anterior Cervical Discectomy and Fusion for Spinal Degenerative Cases

STUDY DESIGN

Guideline.

OBJECTIVES

To develop an international guideline (AOGO) about the use of osteobiologics in anterior cervical discectomy and fusion (ACDF) for treating degenerative spine conditions.

METHODS

The guideline development process was guided by AO Spine Knowledge Forum Degenerative (KF Degen) and followed the Guideline International Network McMaster Guideline Development Checklist. The process involved 73 participants with expertise in degenerative spine diseases and surgery from 22 countries. Fifteen systematic reviews were conducted addressing respective key topics and evidence was collected. The methodologist compiled the evidence into GRADE Evidence-to-Decision frameworks. Guideline panel members judged the outcomes and other criteria and made the final recommendations through consensus.

RESULTS

Five conditional recommendations were created. A conditional recommendation is about the use of allograft, autograft or a cage with an osteobiologic in primary ACDF surgery. Other conditional recommendations are about the use of osteobiologic for single- or multi-level ACDF, and for hybrid construct surgery. It is suggested that surgeons use other osteobiologics rather than human bone morphogenetic protein-2 (BMP-2) in common clinical situations. Surgeons are recommended to choose 1 graft over another or 1 osteobiologic over another primarily based on clinical situation, and the costs and availability of the materials.

CONCLUSION

This AOGO guideline is the first to provide recommendations for the use of osteobiologics in ACDF. Despite the comprehensive searches for evidence, there were few studies completed with small sample sizes and primarily as case series with inherent risks of bias. Therefore, high-quality clinical evidence is demanded to improve the guideline.

Current and Expanded Indications for Cervical Disc Arthroplasty: Beyond the FDA IDE Studies

The widespread success of cervical disc arthroplasty (CDA) has led to an interest in expanding indications beyond those outlined in the initial Food and Drug Administration investigational device exemption studies. Some of these off-label indications currently include 3-level and 4-level CDA, hybrid constructs with adjacent segment anterior cervical discectomy and fusion or corpectomy constructs, pre-existing kyphosis, revision of a failed anterior cervical discectomy and fusion to a CDA, CDA in the setting of significant degenerative disc disease and/or facet joint arthropathy, CDA for congenital cervical stenosis, and CDA in the presence of ossification of the posterior longitudinal ligament. This review article will summarize the current literature pertaining to the aforementioned indications.

Current Evidence for Hybrid Constructs: Simultaneous ACDF/Arthroplasty and Arthroplasty Adjacent to Previous ACDF

It is not surprising that the utilization of hybrid constructs, combining cervical disc arthroplasty with anterior cervical disc arthroplasty, has steadily increased over the last decade. Known limitations exist with multi-level anterior cervical disc arthroplasty and cervical disc arthroplasty procedures. Hybrid surgery offers the possibility to address patient-specific pathology in a more tailored manner by restoring functional mobility and promoting fusion where appropriate. This review discusses the current evidence, both biomechanical and clinical, of hybrid surgery for 2-level and 3-level cervical disease.

Anterior cervical discectomy and fusion for the treatment of giant cervical disc herniation

OBJECTIVE

Giant cervical disc herniation (GCDH) was defined as a herniated intervertebral disc that accounted for more than 50% of the spinal canal. The purpose of this study was to analyse the feasibility of anterior cervical discectomy and fusion (ACDF) for the treatment of GCDH.

METHODS

Patient demographic and imaging data, clinical results, and perioperative complications were analysed retrospectively.

RESULTS

A total of 23 patients were included in the study. Spinal cord recovery pulsation was observed under a microscope in all cases. Postoperative magnetic resonance imaging showed complete decompression of the spinal cord and no residual intervertebral disc. The patients were followed up for 12 to 18 months. The average visual analogue scale score and Neck Disability Index decreased from 8.6 ± 0.5 and 86.0 ± 2.7% to 2.2 ± 0.2 and 26.7 ± 2.0%, respectively, three days after surgery. The average Japanese Orthopedic Association score increased from 6.9 ± 2.1 to 13.9 ± 1.1. The cervical spinal cord function improvement rate was 69.3%. No neurological complications after surgery were observed.

CONCLUSION

This study shows that ACDF is feasible for the treatment of GCDH disease. The results indicate that this approach can be used to safely remove herniated disc fragments, effectively relieve compression of the spinal cord, and improve neurological function.

A real-world analysis of hybrid CDA and ACDF compared to multilevel ACDF

BACKGROUND

Multilevel anterior cervical discectomy and fusion (mACDF) is the gold standard for multilevel spinal disease; although safe and effective, mACDF can limit regular spinal motion and contribute to adjacent segment disease (ASD). Hybrid surgery, composed of ACDF and cervical disc arthroplasty, has the potential to reduce ASD by retaining spinal mobility. This study examined the safety of hybrid surgery by utilizing administrative claims data to compare real-world rates of subsequent surgery and post-procedural hospitalization within populations of patients undergoing hybrid surgery versus mACDF for multilevel spinal disease.

METHODS

This observational, retrospective analysis used the MarketScan Commercial and Medicare Database from July 2013 through June 2020. Propensity score matched cohorts of patients who received hybrid surgery or mACDF were established based on the presence of spinal surgery procedure codes in the claims data and followed over a variable post-period. Rates of subsequent surgery and post-procedural hospitalization (30- and 90-day) were compared between hybrid surgery and mACDF cohorts.

RESULTS

A total of 430 hybrid surgery patients and 2,136 mACDF patients qualified for the study; average follow-up was approximately 2 years. Similar rates of subsequent surgery (Hybrid: 1.9 surgeries/100 patient-years; mACDF: 1.8 surgeries/100 patient-years) were observed for the two cohorts. Hospitalization rates were also similar across cohorts at 30 days post-procedure (Hybrid: 0.67% hospitalized/patient-year; mACDF: 0.87% hospitalized/patient-year). At 90 days post-procedure, hybrid surgery patients had slightly lower rates of hospitalization compared to mACDF patients (0.23% versus 0.42% hospitalized/patient-year; p < 0.05).

CONCLUSIONS

Findings of this real-world, retrospective cohort study confirm prior reports indicating that hybrid surgery is a safe and effective intervention for multilevel spinal disease which demonstrates non-inferiority in relation to the current gold standard mACDF. The use of administrative claims data in this analysis provides a unique perspective allowing the inclusion of a larger, more generalizable population has historically been reported on in small cohort studies.

Neurological outcomes after surgery and postoperative rehabilitation for cervical radiculopathy due to disc disease: a 2-year-follow-up of a randomized clinical trial

Reports on neurological outcomes in patients with cervical radiculopathy (CR) undergoing surgery and postoperative rehabilitation are important to inform prognosis. This 2-year-follow-up of a randomized clinical trial aimed to compare secondary neurological outcomes between structured postoperative rehabilitation and a standard approach after surgery for CR. A secondary aim was to increase knowledge about recovery of neurological impairments in relation to patient-reported neck disability. Neurological outcomes included assessment of sensibility, motor function, arm reflexes and the Spurling test. A total of 153 and 135 participants (> 70% response rate) completed the clinical examination. Between-group differences, changes over time, and associations between persistent neurological impairments and the Neck Disability Index were investigated. No between-group differences were reported (p > 0.07), and neurological impairments in sensibility, motor function, and a positive Spurling test decreased over time in both groups (p < 0.04). Persistent impairments in sensibility and reflex arm were most frequent at follow-up, whereas, a persistent positive Spurling test, and impairments in motor function were associated with higher NDI score. Neurological outcomes improved over time in patients undergoing surgery for CR with no between-group differences., However, persistent neurological impairments were common, and associated with poorer outcome for patient-reported neck disability.Clinical registration: clinicaltrial.gov NCT01547611, 08/03/2012, Title: Outcome of physiotherapy after surgery for cervical disc disease: a prospective multi-centre trial.

Hybrid Implants in Anterior Cervical Spine Surgery: The State of the Art and New Trends for Multilevel Degenerative Disc Disease

BACKGROUND

Anterior cervical discectomy and fusion (ACDF) still represents the first surgical option in the treatment of cervical degenerative disc disease (DDD) but is still burdened by several complications secondary to the loss of mobility at the treated segment and adjacent segment diseases (ASDs). To overcome those complications, hybrid surgery (HS) incorporating ACDF and cervical disc arthroplasty (CDA) is increasingly performed for DDD.

METHODS

We retrospectively reviewed the clinical, surgical, and outcome data of 85 consecutive patients (M/F, 41/44) harboring cervical disc herniation with or without osteophytes, with radiculopathy and with or without myelopathy, who underwent the anterior approach to a cervical discectomy on two or more levels with at least one disc prosthesis, along with a cage and plate or an O Profile screwed plate.

RESULTS

All the patients improved regardless of the cervical construct used. No significant relationship between different kinds of prosthesis and their surgical level; the number of cages; and the site of the cages (screwed and/or plated) was found concerning immediate stability, dynamic prosthesis effectiveness, and clinical improvement in all the patients up to the maximum follow-up time.

CONCLUSIONS

Although the optimal surgical technique for cervical DDD remains controversial, HS represents a safe and effective procedure in select patients with multilevel cervical DDD, as demonstrated by biomechanical and clinical studies and the present series.

Risk Factors for Adjacent Segment Disease Following Anterior Cervical Discectomy and Fusion with Plate Fixation: A Systematic Review and Meta-Analysis

BACKGROUND

Adjacent segment disease (ASD) following anterior cervical discectomy and fusion with plating (ACDF-P) may yield a poor prognosis or reoperation. This review aimed to summarize risk factors for radiographic ASD (RASD) and clinical ASD (CASD) after ACDF-P.

METHODS

Six electronic databases were searched from inception to October 30, 2021. Four reviewers independently screened titles, abstracts, and full-text articles to identify relevant studies. Methodological quality of the included studies was evaluated. Meta-analyses for risk factors were conducted, if possible.

RESULTS

Sixteen cohort and 3 case-control studies (3,563 participants) were included. These studies showed low (n = 2), moderate (n = 9), and high (n = 8) risk of bias. One risk factor for RASD was pooled for 2 meta-analyses based on the follow-up period. Four different risk factors for CASD at ≥4 years were pooled for meta-analyses. Limited evidence showed that multi-level fusion, greater asymmetry in total or functional cross-sectional area of the cervical paraspinal muscle, and preoperative degeneration in a greater number of segments were associated with a higher RASD incidence <4 years after ACDF-P. In contrast, no significant risk factors were identified for CASD <4 years after ACDF-P. At ≥4 years after ACDF-P, limited evidence supported that both cephalad and caudal plate-to-disc distances of <5 mm were associated with a higher RASD incidence, and very limited evidence supported that developmental canal stenosis, preoperative RASD, unfused C5-C6 or C6-C7 adjacent segments, use of autogenous bone graft, and spondylosis-related ACDF-P were associated with a higher CASD incidence.

CONCLUSIONS

Although several risk factors for RASD and CASD development after ACDF-P were identified, the supporting evidence was very limited to limited. Future prospective studies should extend the existing knowledge by more robustly identifying risk factors for RASD and CASD after ACDF-P to inform clinical practice.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Incorporating strategy in hybrid surgery for continuous two-level cervical spondylosis from a biomechanical perspective

BACKGROUND AND OBJECTIVE

Hybrid surgery, incorporating cervical disc replacement and anterior cervical discectomy and fusion, has shown good clinical results in the treatment of multilevel cervical spondylosis according to early follow-ups. This study investigated the surgical strategy of hybrid surgery for two-level cervical spondylosis by distinguishing the biomechanical characteristics with different incorporating modes.

METHOD

A finite element model of a healthy cervical spine including C2-T1 was developed, and hybrid surgery was simulated by replacing at one level with Prestige-LP and fusion at another level with the anterior plate in C3-C5 (Hybrid-S1: replaced at C3-C4, Hybrid-S2: replaced at C4-C5), and in C4-C6 (Hybrid-M1: replaced at C4-C5, Hybrid-M2: replaced at C5-C6) and in C5-C7 (Hybrid-U1: replaced at C5-C6, Hybrid-U2: replaced at C6-C7). The motion of C2 vertebrae in flexion, extension, axial rotation, and lateral bending was imposed on all hybrid models following the displacement control testing protocol.

RESULTS

The largest range of motion (ROM) in a healthy spine was observed at C5-C6, followed by C3-C4, C4-C5 and C6-C7. On average, the ROM at the replaced segment increased by 175.7%, 202.7%, 176.3%, 117.1%, 139.4%, and 236.0% in Hybrid-S1, Hybrid-S2, Hybrid-M1, Hybrid-M2, Hybrid-U1, and Hybrid-U2, respectively. The facet joint stress at the replaced segment increased by 186.9%, 124.4%, 111.1%, 60.3%, 62.7%, and 144.7%, and the adjacent intradiscal pressure (IDP) increased by 45.2%, 38.7%, 2.7%, 2.1%, 13.9%, and 20.1%.

CONCLUSIONS

Incorporating mode in hybrid surgery affects cervical biomechanics. Hybrid surgery with replacement at a segment with a greater ROM and fusion at a segment with a lower ROM can results in fewer changes in terms of overall cervical stiffness, ROM at the operative level, facet joint stress, and adjacent IDP. In hybrid surgery, it is better to implement disc replacement at a level with a greater ROM and fusion of another segment.

Classification of three-level hybrid surgery for the treatment of cervical degenerative disc disease: a retrospective study of 108 patients

INTRODUCTION

According to the different numbers and locations of cervical disc arthroplasty (CDA) and anterior cervical discectomy and fusion (ACDF), three-level hybrid surgery (HS) has many constructs. The purpose of the present study was to introduce a classification system for three-level HS and compare the two types with each other and with ACDF.

METHODS

A retrospective study was conducted involving patients with three-level cervical degenerative disc disease (CDDD) who underwent ACDF or HS in our hospital between June 2012 and May 2019. According to the different numbers and locations of ACDFs and CDAs, we classified the three-level HS into two types (type I: one-level CDA and two-level ACDF, and type II: two-level CDA and one-level ACDF). The differences of clinical and radiological outcomes were compared with each other and with three-level ACDF.

RESULTS

A total of 108 patients were analyzed. The Neck Disability Index (NDI) of the ACDF group at 3 months postoperatively was significantly higher than that in the type I and type II groups (p < 0.05). The cervical lordosis was significantly lower in the ACDF group than that in the type I and II groups at 3 days, 6, 12 months postoperatively and the final follow-up (p < 0.05). The range of motion (ROM) of the total cervical spine decreased significantly in all three groups at 3, 6, and 12 months postoperatively and at the final follow-up (p < 0.05). The ACDF group was observed with the most severe loss of ROM of the total cervical spine, followed by the type I group. The type II group could preserve the most ROM of the total cervical spine. The ROM of adjacent segments increased most in the ACDF group, followed by the type I group.

CONCLUSIONS

Compared with ACDF, three-level HS may yield a faster recovery rate and superior radiological outcomes, such as a superiority in maintaining the cervical curvature and ROM of the total cervical spine and a smaller increase in the ROM of adjacent segments. The advantages were most remarkable in the type II group.

Clinical and Radiological Comparison of Hybrid Surgery and Fusion Application with Peek Cage in Patients Undergoing Three-Level Anterior Cervical Discectomy

OBJECTIVE

In this study, we aimed to compare patients with degenerative cervical disc herniation (CDH) who had undergone three-level anterior cervical discectomy (ACD) and fusion with a peek cage supported by synthetic bone graft in all levels to the cases with CDH with hybrid surgery (HS) regarding their radiological findings and surgical results.

MATERIALS AND METHODS

The patients who had undergone three-level ACD were evaluated retrospectively. The cases who were followed up for 2 years and longer were evaluated regarding gender, age, radiological findings, and patient satisfaction. A radiological assessment was made by calculating the Cobb angle on lateral cervical radiographs. Clinical assessment was performed by the Neck Disability Index (NDI).

RESULTS

In the first group, 13 patients had undergone ACD and fusion with peek cage and bone graft, and in the hybrid group, there were 11 patients in whom fusion with peek cage and bone graft were made in two levels, and cervical disc arthroplasty was performed throughout the distance in-between. In the hybrid group, the 1-month and 24-month changes in cervical range of motion in hyperflexion were statistically significant (p < 0.05). In both groups, significant improvements of NDI were determined postoperatively (p < 0.05). When the groups were compared, the 1-month and 24-month improvements were statistically significantly increased in the hybrid surgery group compared to the group that underwent fusion surgery with a cage (p < 0.05).

CONCLUSIONS

HS is a reliable and effective treatment method in the three-level cervical disk disease for preserving and improving cervical ROM, particularly in the flexion position.

Two-Level Anterior Cervical Discectomy and Fusion versus Hybrid Total Disc Replacement for Bilevel Pathology with Cervical Radiculopathy/Myelopathy: A Comparative Study with a Minimum 2-Year Follow-up in an Indian Population

Study Design

Retrospective study.

Purpose

To study the outcomes of two-level anterior cervical discectomy and fusion (2L-ACDF) versus hybrid total disc replacement (H-TDR) for cervical myeloradiculopathy.

Overview of Literature

For bilevel disc issues of the cervical spine, 2L-ACDF has been a historical tool with numerous implants used at different time frames. Recent developments in total disc replacement at mobile level with fusion at a spondylotic level known as hybrid fixation have added a new armamentarium for such disorders.

Methods

An analysis of 49 consecutive patients who underwent 2L-ACDF (n=22) and H-TDR (n=27) from January 1, 2014 to December 31, 2017 was performed. Data were studied as retrieved from InstaPACS ver. 4.0 (Mediff Technologies Pvt. Ltd., Bengaluru, India) and medical records.

Results

Twenty-two patients with 2L-ACDF and 27 patients with H-TDR were included. The mean±standard deviation (SD) follow-up duration was 4.0±1.5 years in H-TDR and 3.1±1.1 years in 2L-ACDF. The mean±SD Neck Disability Index (NDI) decreased from 26.1±7.6 to 6.5±3.9 in the H-TDR group and from 27.6±7.2 to 6.4±4.8 in the 2L-ACDF group at final follow-up. Disc height at suprajacent level in the 2L-ACDF group was 4.12±0.48 mm, 4.10±0.45 mm, and 4.05±0.48 mm preoperatively, at 1-year, and final follow-up, respectively. Disc height at supradjacent level in the H-TDR group was 4.28±0.36 mm, 4.20±0.32 mm, and 4.19±0.34 mm preoperatively, at 1-year, and final follow-up, respectively.

Conclusions

There was significantly improved NDI in both groups. Adjacent segment disc height loss was greater in the 2L-ACDF group than in H-TDR but not statistically significant (p =0.304). Supradjacent segment range of motion was greater in the 2L-ACDF group than in the H-TDR group (p =0.003). Both findings supported radiographic adjacent segment degeneration (ASD), but symptomatic ASD was absent in both groups.

Hybrid Anterior Cervical Discectomy and Fusion and Cervical Disc Arthroplasty: An Analysis of Short-Term Complications, Reoperations, and Readmissions

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

Although cervical disc arthroplasty (CDA) has become a well-established and effective treatment for symptomatic cervical degeneration, many patients with multilevel disease are not good candidates for CDA at all levels. For such patients, hybrid surgery (HS)-a combination of adjacent anterior cervical discectomy and fusion (ACDF) and CDA-may be more appropriate. Given the novelty of HS and the relative dearth of studies adequately assessing short-term perioperative complications, this current study sought to assess the short-term morbidity profile of HS, differences in operative duration, length of stay (LOS), and readmission and reoperation rates and reasons relative to a 2-level ACDF cohort.

METHODS

All patients who underwent HS and 2-level ACDF were identified between 2011 and 2018 using a large, prospectively collected registry. Baseline patient characteristics and postoperative complications were compared using bivariate and/or multivariate analysis.

RESULTS

A total of 390 patients undergoing HS were identified. Two-level procedures were the most common (74.9%). Patients undergoing HS were more likely to be younger, male, and have fewer comorbidities. There were no differences between HS and 2-level ACDF in rates of any postoperative complication, transfusion, readmissions, and operative duration. However, HS had a decreased LOS (0.5 days), relative to a 2-level ACDF. HS patients had low rates of reoperation (1.28%) with 1 case for hematoma evacuation and another for revision CDA.

CONCLUSIONS

This study represents one of the largest cohorts of patients undergoing HS reported to date. Patients undergoing HS are not at increased risk of perioperative complications relative to a 2-level ACDF and may benefit from shorter LOS.

Cervical balance and clinical outcomes in cervical spondylotic myelopathy treated by three-level anterior cervical discectomy and fusion and hybrid cervical surgery: A CONSORT-compliant study with minimum follow-up period of 5 years

As the technology of combining with fusion and nonfusion procedure, cervical hybrid surgery (HS) is an efficacious alternative for treatment with cervical spondylotic myelopathy. While studies on cervical alignment between 3-level HS and anterior cervical discectomy and fusion (ACDF) were seldom reported. The effects of cervical imbalance on its related clinical outcomes are yet undetermined as well.Patients with cervical spondylotic myelopathy, who underwent 3-level ACDF or HS, were included to compare cervical alignment parameters after surgery and then explore the relationship between cervical balance and clinical outcomes.Forty-one patients with HS (HS group) and 32 patients who with ACDF (ACDF group) were reviewed from February 2007 to September 2013 with the mean follow-up of 90.3 ± 25.5 (m) and 86.3 ± 28.9 (m), respectively. Cervical alignments parameters including the C2 to C7 cervical lordosis (CL), C2 to C7 sagittal vertical axis, T1 slope. and T1SCL (T1 slope minus CL), and the clinical outcomes like neck disability index (NDI) and Japanese Orthopedic Association (JOA) score were measured and recorded preoperatively (PreOP), intraoperatively, and on the first preoperative day and the last follow-up (FFU). The balance and imbalance groupings were sorted based on the T1SCL: T1SCL≤20°,balance; T1SCL > 20°, imbalance.We found significant improvements (P < .001) in NDI and JOA at intraoperatively and FFU after ACDF and HS, and no difference on cervical alignment and clinical outcomes between the 2 procedures on the basis of intergroup comparisons. By between-subgroups comparisons, however, we found significant differences in CL and T1SCL at PreOP (P < .05). Nonetheless, there was no significant difference on the clinical outcomes between balance and imbalance subgroups at FFU at PreOP (P > .05), indicating that the change of T1SCL was not correlated to NDI and JOA at FFU.Both HS and ACDF groups showed significant clinical improvements after surgery. There was no correlation between cervical balance and clinical symptoms.

Hybrid implants in anterior cervical decompressive surgery for degenerative disease

Background:

Anterior cervical discectomy and fusion (ACDF) still represent the mainstream surgical approach in the treatment of degenerative cervical Degenerative Disc Disease (DDD), being a loss of mobility at the treated segment and adjacent segment diseases well-known complications. To overcome those complications, hybrid surgery (HS) incorporating ACDF and cervical disk arthroplasty is increasingly performed for DDD.

Methods:

We retrospectively reviewed the clinical, surgical, and outcome data of 62 consecutive patients (male/female, 29/37) harboring cervical disk herniation with or without osteophytes, with radiculopathy with or without myelopathy, who underwent a cervical discectomy on two or more levels with the anterior approach with at least one disk prosthesis along with cage and plate or O Profile screwed plate.

Results:

All the patients improved regardless of the cervical construct used. No significant relationship between different kind of prostheses as well as their surgical level, the number and the site of the cages (screwed and/or plated) was found out concerning immediate stability, dynamic prosthesis effectiveness, and clinical improvement in all the patients up to the maximum follow-up.

Conclusions:

Although the optimal surgical technique for cervical DDD remains controversial, HS represents a safe and effective procedure in selected patients with multilevel cervical DDD, as demonstrated by biomechanical and clinical studies and the present series. Some technical aspects should be considered when dealing with this procedure, like the drilling of the endplate, and some radiological findings have to be detected because potentially predictive of future misplacement.

Viscoelastic cervical total disc replacement devices: Design concepts

Cervical disc replacement (CDR) is a motion-preserving surgical procedure for treating patients with degenerative disorders. Numerous reports of first generation CDR "ball-and-socket" articulating devices have shown satisfactory clinical results. As a result, CDR devices have been safely implemented in the surgeon's armamentarium on a global scale. However, only minor design improvements have been made over the last few years, as first generation CDRs devices were based on traditional synovial joint arthroplasty designs. As a consequence, these articulating designs have limited resemblance to the complex kinematic behavior of a natural disc. This has driven the development of deformable viscoelastic CDR devices to better mimic the biomechanical behavior of a natural disc. As a result, several viscoelastic CDR devices have been developed in recent years that vary in terms of materials, design and clinical outcomes. Since these viscoelastic CDR devices are fairly new, their weaknesses and strengths, which are related to their design characteristics, have not been well described. Therefore, this literature review discusses design related advantages and disadvantages of deformable viscoelastic CDR devices. As such, this paper can provide insight for surgeons and engineers on specific design characteristics of several viscoelastic devices and could potentially help to develop and design future implants. Eleven viscoelastic CDR devices were identified. An extensive database search on the devices' tradenames in Medline and PubMed was performed next. The devices were categorized based on common design characteristics to give an overview of both category and device specific complications and advantages. Overall, literature shows that most of these viscoelastic CDR devices can provide motion in all six degrees-of-freedom and have a variable center of rotation. Nevertheless, the viscoelastic materials used do not have an extensive history in orthopedics, so the long-term material behavior in vivo is still unknown. Although the viscoelastic devices have common benefits and risks, each specific design and category also has its own design related advantages and drawbacks that are described in this review. Altogether, viscoelastic total disc replacements seem to be a promising option for the future of cervical arthroplasty, but long-term clinical outcome is needed to confirm the advantages of mimicking the viscoelasticity of a natural disc.

A Comparison of 2 Anterior Hybrid Techniques for 3-Level Cervical Degenerative Disc Disease

Background

Novel hybrid surgical techniques that incorporate anterior cervical discectomy and fusion with total disc replacement are widely used. Based on the number of implanted discs, 3-level hybrid surgery can be classified as single fusion combined with double replacement and single replacement combined with double fusion. Few studies to date have directly compared these hybrid techniques. The present study compared the clinical and radiological outcomes of these methods and assessed their characteristics and benefits.

Material/Methods

Clinical and radiological outcomes were retrospectively evaluated in 64 consecutive patients who underwent 3-level hybrid surgery by single fusion combined with double replacement or single replacement combined with double fusion.

Results

Significant differences between the 2 groups were observed in postoperative range of motion of C2–C7. C2–C7 cervical lordosis assessed preoperatively and at final follow-up differed significantly in patients who underwent single replacement combined with double fusion. This group showed a higher incidence of heterotopic ossification than patients who underwent double replacement combined with single fusion.

Conclusions

Both types of hybrid surgery are safe and effective in treating 3-level cervical degenerative disc diseases. Single replacement combined with double fusion showed greater accuracy in correcting cervical lordosis, but was associated with a higher incidence of heterotopic ossification. In contrast, single fusion combined with double replacement was superior in maintaining cervical range of motion.

Is Cervical Disc Replacement Valuable in 3-Level Hybrid Surgery Compared with 3-Level Anterior Cervical Discectomy and Fusion?

BACKGROUND

Cervical degenerative disc disease is common in clinical practice. Surgery is among the most effective treatments for patients with cervical radiculopathy, myelopathy, or stenosis. Which treatment is the best option for multilevel cervical degenerative disc disease is controversial. Hybrid surgery, combined cervical disc replacement and anterior cervical discectomy and fusion, may be an alternative treatment for multilevel cervical degenerative disc disease.

METHODS

Sixty-four patients with 3-level hybrid surgery and 37 patients with 3-level anterior cervical discectomy and fusion were reviewed retrospectively. Clinical outcomes were based on visual analog scale, Neck Disability Index, 36-Item Short Form Survey, and Japanese Orthopaedic Association scores and Japanese Orthopaedic Association recovery rate. Radiologic assessments included range of motion (ROM) of C2-C7 and adjacent level and cervical lordosis of C2-C7. Perioperative parameters, fusion condition, and complications were assessed.

RESULTS

There were no statistical differences observed between the 2 groups for Japanese Orthopaedic Association, Neck Disability Index, or visual analog scale scores. The hybrid surgery group had better physical and mental 36-Item Short Form Survey scores than the fusion group at 1-year follow-up (physical component summary: 49.34 vs. 46.70, P = 0.012; mental component summary: 45.67 vs. 43.95, P = 0.004). ROM of C2-C7 and adjacent levels was less compromised in the hybrid group compared with baseline (64.60% vs. 51.34%, P < 0.001). Cervical lordosis was decreased with time in both groups but was acceptable at final follow-up, and both groups showed solid fusion.

CONCLUSIONS

Normal ROM and solid fusion were achieved at both arthroplasty and arthrodesis levels. ROM of replacement levels in different locations of the 3-level construct was acceptable.

Clinical Outcomes of Cervical Hybrid Reconstructions: A Prospective Study

BACKGROUND

The study design was a prospective clinical cohort study. The aim of this study was to assess the patient-reported outcome measures (PROMs), patient satisfaction, as well as complication and reoperation rate of cervical hybrid procedures for symptomatic cervical multilevel degenerative disc disease (MLDDD). Cervical total disc replacement (CTDR) has been shown to be safe and effective for the treatment of degenerative pathologies. However, there is minimal PROMs data on the outcomes of combined CTDR and anterior cervical decompression and fusion procedures, commonly referred to as cervical hybrid surgery.

METHODS

Prospectively collected PROMs were analyzed from patients receiving cervical hybrid surgery for symptomatic cervical MLDDD. Between 2004 and 2016, data were collected preoperatively and postoperatively at 3, 6, and 12 months, then yearly thereafter. Patient reported outcome measures included patient satisfaction, visual analog score for neck and arm, and Neck Disability Index. Complication and reoperation rates were also assessed.

RESULTS

A total of 151 patients (80 males, 71 females) who had a minimum of 12 months follow up were included. The mean age was 53 years (range = 24-81), and median follow up was 2 years (range = 1-10). The median number of levels treated was 3, with 29.8%, 49.0%, and 21.2% of patients having 2, 3, and 4 levels treated, respectively. The most common indication for surgery was multilevel cervical spondylotic radiculopathy (52.8%), followed by combined cervical spondylotic radiculomyelopathy (16.7%), axial neck pain (16%), and cervical spondylotic myelopathy (13.9%). Improvement in pain and disability scores were both clinically and statistically significant (P < .001), and these improvements were sustained throughout the course of follow up. There was a 16% incidence of minor adverse events, and 3 (1.9%) reoperations.

CONCLUSIONS

Cervical hybrid surgery for cervical MLDDD demonstrates favorable and sustained clinical outcomes at short-term to midterm follow up.

LEVEL OF EVIDENCE

4.

CLINICAL RELEVANCE

Statistically and substantial clinical benefits can be achieved by cervical hybrid surgery, in the treatment of cervical pathologies including radiculopathy and myelopathy. The key principles is to follow strict indications, and to match technology with the pathology.

Stand-alone polyetheretherketone cages for anterior cervical discectomy and fusion for successive four-level degenerative disc disease without plate fixation

Background:

Anterior cervical discectomy with fusion became the most frequently performed technique for the treatment of symptoms related to cervical disc prolapse. Multilevel anterior cervical discectomy has been combined with anterior cervical plate application to help maintain the cervical lordosis and enhance fusion. This was associated with more soft-tissue separation and retraction with increased incidence of surgically related complications and postoperative dysphagia.

Aim of the Study:

The aim of this study is to evaluate the safety and efficacy of the stand-alone cervical polyetheretherketone (PEEK) cages in four-level discectomy and to determine if it is possible to avoid anterior plate fixation and to achieve satisfactory outcomes.

Methodology:

This is a retrospective study which was performed between June 2011 and December 2018 at one institute. The clinical and radiological data were collected from patients who underwent successive four-level anterior cervical discectomy and fusion with PEEK cages for degenerative cervical disc disease without plate fixation.

Results:

This study included 66 patients, 35 males and 31 females. The follow-up period was 24 months. Mean Japanese Orthopedic Association scores were 13.3 ± 1.41 preoperative and 15.9 ± 0.86 postoperative (P = 0.046). The cervical curvature index “Ishihara” (ICI) was 9.9 ± 5.90 preoperative and the mean of ICI was 10.5 ± 6.65 postoperative, which is insignificant, P = 0.7). The lordotic curvature according to these results was preserved till the end of the year and half of the follow-up period postoperative.

Conclusion:

Consecutive four-level anterior discectomy with PEEK cage interbody fusion without plate and screw is a safe and effective procedure in the absence of instability, and it may be a reliable alternative for the treatment of multilevel cervical disc.

Optimization of Three-Level Cervical Hybrid Surgery to Prevent Adjacent Segment Disease: A Finite Element Study

Hybrid surgery (HS) allows surgeons to tailor fusion and arthroplasty in the treatment of multiple-level cervical disc degeneration. However, the decision making of selecting either ACDF or ADR for each level in three-level HS remains controversial and has not been fully investigated. This study was aimed to optimize three-level cervical hybrid constructs by systematically investigating their biomechanical properties and their effect on adjacent levels. A finite element model of cervical spine (C2–C7) was developed, and eight C3–C6 surgical models including six HS were constructed. The range of motion (ROM) in flexion, extension, lateral bending, and axial rotation under 2.0 Nm moments with 30 N follower load were simulated. The von Mises stress, strain energy at the adjacent intervertebral disc (IVD) and force at the adjacent facet were calculated. The ROM of the hybrid constructs and adjacent levels was close to that of the intact spine. HS with arthroplasty performed at C5-6 had better performance in terms of ROM reduction at the inferior adjacent level (C6-7). Moreover, C-D-D and 3ADR had best performance in reducing the von Mises stress and strain energy at C6-7. All HS reduced the facet burden at both C2-3 and C6-7 levels. However, the major drawback of HS revealed here is that the effect of C6-7 protection is at the cost of increased C2-3 IVD burden. In conclusion, we recommend C-D-D and 3ADR for patient with C3–C6 disc degeneration without predisposing C2-3 condition. C-C-D could be a good alternative with a lower medical cost. This analysis guides the decision making in three-level cervical HS before future cadaver studies or human clinical trials.

Hybrid decompression and reconstruction technique for cervical spondylotic myelopathy: case series and review of the literature

The primary treatment of choice for patients with cervical spondylotic myelopathy (CSM) is surgical decompression. The benefit of operative intervention has been well established but, the surgeons' decision of operative approach remains nuanced based on patient-specific variables and surgeon preference. Decompression can involve a cervical corpectomy or a discectomy. A hybrid construct is when both a cervical corpectomy and a discectomy are done in the same patient. The purpose of this study was to review the evidence on the clinical and biomechanical outcomes of hybrid decompression and reconstruction techniques in patients with multilevel CSM. A retrospective study was performed on consecutive patients who received hybrid anterior decompression and reconstruction at Rush University between 2013-2018. Preoperative clinical and radiographic variables were analyzed to characterize specific factors leading to the decision of the surgical approach. In addition, we performed a systematic review and meta-analysis to assess superiority in terms of operative time, blood loss, cervical lordosis, patient-reported outcomes (PRO), fusion rates, and complications. Hybrid surgery (HS) was utilized in cases where multilevel CSM was present in conjunction with stenosis posterior to the vertebral body or acute kyphotic deformity. Our meta-analysis highlighted comparable PRO, complications, and rate of success fusion between 3-level anterior cervical discectomy and fusion (ACDF) and hybrid technique. Furthermore, hybrid fusion led to increased postoperative cervical lordosis, higher fusion rate, lower total complication rate, lower implant failure/mesh subsidence rate, and lower blood loss than 2-level corpectomy. The cervical hybrid technique that combines cervical corpectomy and discectomy represents a balanced option with the benefits of two commonly utilized cervical spine procedures in patients with multilevel CSM. The literature on hybrid technique suggests in cases where multilevel ACDF is not feasible, combining discectomy and corpectomy is superior to two-level corpectomy with lower complication rates, improved clinical outcome, spinal alignment correction, and stronger biomechanical properties.

The appropriate hybrid surgical strategy in three-level cervical degenerative disc disease: a finite element analysis

Objective

The purpose of this FE study was to analyze the biomechanical characteristics of different HS strategies used in the treatment of three-level CDDD (one-level CDA and two-level ACDF).

Methods

We validated the FE model of an intact cervical spine established by transferring the data, collected by 3D CT scan, to the FE software ABAQUS and comparing these data with the data from published studies. Then, the FE model of hybrid surgery was reconstructed to analyze the range of motion (ROM), facet joint force, and stress distribution on an ultrahigh molecular weight polyethylene (UHMWPE) core.

Results

The current cervical FE model was able to measure the biomechanical changes in a follow-up hybrid surgery simulation. The total ROM of the cervical HS models was substantially decreased compared with the total ROM of the intact group, and the M2 (C3/4 ACDF, C4/5 CDA, and C5/6 ACDF) model had the closest total ROM to the intact group, but the facet joint force adjacent to the treatment levels showed very little difference among them. The stress distribution showed noticeable similarity: two flanks were observed in the center core, but the inlay of M2 was more vulnerable.

Conclusions

Through the comparison of ROM, the facet joint force after CDA, and the stress distribution of the prosthesis, we find that M2 model has a better theoretical outcome, especially in preserving the maximum total ROM.

Clinical and Radiographic Outcome of Patients With Cervical Spondylotic Myelopathy Undergoing Total Disc Replacement

STUDY DESIGN

A nonrandomized, prospective, and single-center clinical trial.

OBJECTIVE

The aim of this study was to investigate the clinical and radiographic efficacy of ProDisc Vivo cervical total disc replacement (cTDR) in patients with clinical and radiographic documented cervical spondylotic myelopathy (CSM), due to degenerative changes at the index level.

SUMMARY OF BACKGROUND DATA

Decompression and fusion is still the gold standard in patients with cervical myelopathy. Very limited data are available regarding the application of cTDR in patients with clinical and radiological documented CSM in context of clinical and radiographic outcomes.

METHODS

Clinical outcome scores included the Neck Disability Index (NDI), Visual Analogue Scale (VAS), arm and neck pain self-assessment questionnaires as well as the Nurick grade and the Japanese Orthopaedic Association (JOA) score. The radiological outcome included the range of motion (ROM), the segmental and global (C2-C7) lordosis, and the occurrence of heterotopic ossifications.

RESULTS

Eighteen consecutive patients (10 males, 8 females) with documented clinical and radiological signs of myelopathy were included in this investigation. The study population had a mean age of 52.4 years and a follow-up period of 20.3 months in average (range 3-48 months). The mean range ROM of the index level stayed consistent with 6.8° preoperatively and 7.2° (P = 0.578) at the last follow-up; the global lordosis in neutral position changed from 3.5° to 14.2° significantly (P = 0.005) in mean. The JOA score improved from 11.3 to 16.6 (P < 0.001) as well as the NDI 36.7 to 10.3 (P < 0.001) and the VAS score from 5.7/6.1 (arm/neck) to 1.3/2.0 (P < 0.001/P < 0.001). The mean Nurick grade was 1.33 preoperatively and dropped down in all cases to Nurick grade of 0 (P < 0.001).

CONCLUSION

cTDR (with ProDisc Vivio) in patients with CSM yielded good clinical and radiographic outcomes and found as a reliable, safe, and motion-preserving surgical treatment option, although its indication is very limited due to numerous exclusion criteria.

LEVEL OF EVIDENCE

4.

Biomechanical effects on the intermediate segment of noncontiguous hybrid surgery with cervical disc arthroplasty and anterior cervical discectomy and fusion: a finite element analysis

BACKGROUND CONTEXT

Surgery for cervical degenerative disc disorder (CDDD) at two noncontiguous segments is infrequent. Few studies have explored the biomechanical effects on the intermediate adjacent segment of anterior cervical discectomy and fusion (ACDF) or cervical disc arthroplasty (CDA) in this situation. No study has examined biomechanical differences between ACDF and hybrid surgery (HS) constructs for noncontiguous CDDD. Differences in the biomechanical changes between the intermediate and adjacent segments are unknown.

PURPOSE

This study was conducted to compare the biomechanical changes resulting from noncontiguous ACDFs and HS.

STUDY DESIGN

A finite element analysis study.

METHODS

A finite element model of a healthy cervical spine (C2-C7) was constructed. Three surgical models were developed: (1) ACDF at C3/4 and C5/6 (FF), (2) ACDF at C3/4 and CDA at C5/6 (FA) and (3) CDA at C3/4 and ACDF at C5/6 (AF). A 75-N follower load with 1.0 N·m moments was applied to the top of the C2 vertebra in the intact model to simulate flexion, extension, lateral bending, and axial rotation. Surgical models achieved identical motion angles of the intact model in each direction following the displacement-control protocols.

RESULTS

The FF model required much higher moments than did the AF and FA models to achieve the same amount of motion. In the FF model, the motion contributions of the unfused segments were unevenly increased. The magnitude of the increased motion in the intermediate segment was larger than those in the supra- or infra-adjacent segments. The facet contact force (FCF) and intradiscal pressure (IDP) at the intermediate segment were also more susceptible to impact. In the FA and AF models, the motion contributions of the untreated levels were evenly changed, and the intermediate segment did not experience additive motion, FCF, or IDP. The segment adjacent to the level of ACDF had greater FCF and IDP than did the segment adjacent to the level of CDA in the two HS constructs.

CONCLUSIONS

HS constructs resulted in less altered biomechanics and kinematics of the untreated levels and showed no additive biomechanical effects on the intermediate segments compared with ACDF at noncontiguous levels. However, the effects were associated with the relative location of the ACDF and CDA levels.

CLINICAL SIGNIFICANCE

This study provides a biomechanical rationale for the use of HS to treat patients with noncontiguous CDDD.

Is the behavior of disc replacement adjacent to fusion affected by the location of the fused level in hybrid surgery?

BACKGROUND CONTEXT

Hybrid surgery (HS), consisting of cervical disc arthroplasty (CDA) at the mobile level, along with anterior cervical discectomy and fusion at the spondylotic level, could be a promising treatment for patients with multilevel cervical degenerative disc disease (DDD). An advantage of this technique is that it uses an optimal procedure according to the status of each level. However, information is lacking regarding the influence of the relative location of the replacement and the fusion segment in vivo.

PURPOSE

We conducted the present study to investigate whether the location of the fusion affected the behavior of the disc replacement and adjacent segments in HS in vivo.

STUDY DESIGN

This is an observational study.

PATIENT SAMPLE

The numbers of patients in the arthroplasty-fusion (AF) and fusion-arthroplasty (FA) groups were 51 and 24, respectively.

OUTCOME MEASURES

The Japanese Orthopedic Association (JOA), Neck Disability Index (NDI), and Visual Analog Scale (VAS) scores were evaluated. Global and segmental lordosis, the range of motion (ROM) of C2-C7, and the operated and adjacent segments were measured. Fusion rate and radiological changes at adjacent levels were observed.

METHODS

Between January 2010 and July 2016, 75 patients with cervical DDD at two contiguous levels undergoing a two-level HS were retrospectively reviewed. The patients were divided into AF and FA groups according to the locations of the disc replacement. Clinical outcomes were evaluated according to the JOA, NDI, and VAS scores. Radiological parameters, including global and segmental lordosis, the ROM of C2-C7, the operated and adjacent segments, and complications, were also evaluated.

RESULTS

Although the JOA, NDI, and VAS scores were improved in both the AF and the FA groups, no significant differences were found between the two groups at any follow-up point. Both groups maintained cervical lordosis, but no difference was found between the groups. Segmental lordosis at the fusion segment was significantly improved postoperatively (p<.001), whereas it was maintained at the arthroplasty segment. The ROM of C2-C7 was significantly decreased in both groups postoperatively (AF p=.001, FA p=.014), but no difference was found between the groups. The FA group exhibited a non-significant improvement in ROM at the arthroplasty segment. The ROM adjacent to the arthroplasty segment was increased, although not significantly, whereas the ROM adjacent to the fusion segment was significantly improved after surgery in both groups (p<.001). Fusion was achieved in all patients. No significant difference in complications was found between the groups.

CONCLUSIONS

In HS, cephalic or caudal fusion segments to the arthroplasty segment did not affect the clinical outcomes and the behavior of CDA. However, the ROM of adjacent segments was affected by the location of the fusion segment; segments adjacent to fusion segments had greater ROMs than segments adjacent to arthroplasty segments.

Primary cervical disc arthroplasty versus cervical disc arthroplasty adjacent to previous fusion: A retrospective study with 48 months of follow-up

The outcomes of cervical disc arthroplasty (CDA) following a previous fusion are ill -defined. The aim of this study was to share our experience and to assess mid-term outcomes in patients receiving CDA adjacent to a previous fusion compared with primary CDA.Patients with cervical radiculopathy and/or myelopathy or patients who had undergone a previous cervical fusion surgery and had developed adjacent segment disease (ASD) between January 2008 and April 2013 were enrolled. Clinical and radiographic outcomes were compared for patients undergoing CDA at a level adjacent to a previous fusion (previous group) and those undergoing primary CDA (primary group).Fifty-two patients in the primary group and 9 patients in the previous group had adequate follow-up data. The mean follow-up periods were 61.96 months and 61.78 months, respectively. The clinical outcomes all significantly improved after surgery, and no significant difference was found between groups. The disc height and range of motion of the operated level were preserved, and the values were similar between groups. Subsidence occurred in 2 (3.8%) patients in the primary group and 1 (11.11%) patient in the previous group. Heterotopic ossification (HO) was detected in 4 (44.44%) patients in the previous group and 18 (34.62%) patients in the primary group. None of the patients required reoperation.Patients treated with a Prestige-LP disc maintained improved clinical outcomes and segmental motion in both the primary and previous groups. Additionally, CDA-treated patients who had a previous fusion surgery could safely undergo the surgery with complication rates similar to that of the first CDA surgery after 48 months of follow-up. CDA adjacent to a previous fusion may be an alternative treatment strategy in the future.

Clinical and Radiologic Features of 3 Reconstructive Procedures for the Surgical Management of Patients with Bilevel Cervical Degenerative Disc Disease at a Minimum Follow-Up Period of 5 Years: A Comparative Study

OBJECTIVE

To assess the mid-long-term follow-up of the safety and efficacy of anterior cervical discectomy and fusion (ACDF), cervical artificial disc replacement (CADR) and hybrid surgery (HS) for bilevel cervical degenerative disc disease (cDDD).

METHODS

77 patients who underwent ACDF, HS, and CADR were retrospectively reviewed. Clinical effects were evaluated based on Neck Disability Index (NDI), Visual Analog Scale (VAS), and Japanese Orthopedic Association (JOA) scores and the Odom criteria. Radiographic outcomes were evaluated, including cervical range of motion (ROM), ROM in the operative and adjacent segments, incidence of degeneration in the adjacent segments (ASD), and heterotopic ossification (HO).

RESULTS

NDI, VAS, and JOA scores significantly improved in all patients after surgery without significant differences between groups. The excellent-to-good ratio in the Odom scale was 28/30 for the HS group, 30/33 for the ACDF group, and 13/14 for the CADR group. No significant differences in clinical outcomes or complication were found between groups (P > 0.05). Furthermore, the HS and CADR groups had less decreased ROM in the cervical and operative segments and less compensatory ROM in adjacent segments (P < 0.05). By contrast, the ACDF group had decreased ROM in the cervical and operative segments and significantly increased ROM in adjacent segments (P < 0.05). Moreover, the incidence of ASD was higher in the ACDF group, but the difference was not statistically significant (P > 0.05). HO was found in 10 patients (33.3%) in the HS group and 5 patients (35.7%) in the CADR group.

CONCLUSION

HS was superior to ACDF with regard to equivalent clinical outcomes in the mid-long-term follow-up. Furthermore, HS was superior in the maintenance of ROM and had less impact on its adjacent segments. The efficacy of HS is similar to that of CADR.

A Prospective Study of Interbody Fat Graft Application With the Anterior Contralateral Cervical Microdiscectomy to Preserve Segmental Mobility

BACKGROUND

Any surgical procedure aims at protecting mobile segments at the operated level, and the sagittal balance of the columna vertebralis. Interbody fusion has become an often applied technique in anterior cervical discectomy.

OBJECTIVE

To indicate that a minimally invasive technique in which we use interbody fat graft placement showed great results and effectiveness, especially in patients who were suffering from cervical paramedian disc herniation.

METHODS

In this study, 432 patients were observed from 2000 to 2013. All these consecutive patients had paramedian disc herniation. The initial 239 patients (group 1) underwent microdiscectomy without graft placement, whereas the remaining 193 patients (group 2) had a microdiscectomy with interbody fat graft insertion. The Neck Disability Index (NDI) and Short Form-36 (SF-36) were used to evaluate clinical outcomes. They were followed up for 5.3 years (range 2-13 years).

RESULTS

Spontaneous radiological fusion was noticed in 12% of group 1 patients and none of the group 2 patients. It has been observed that the mean overall cervical curvature (C2-7) angles and segmental lordosis did not change significantly in late follow-up findings. During both early and late follow-ups, all patients indicated a decreasing NDI score, but in late follow-up, an improving SF-36 score.

CONCLUSION

This surgical technique provides good direct decompression and preserves mobility at the treated level, while preventing disc collapse.

A comparison of anterior cervical discectomy and fusion combined with cervical disc arthroplasty and cervical disc arthroplasty for the treatment of skip-level cervical degenerative disc disease: A retrospective study

Anterior cervical discectomy and fusion (ACDF) has been widely performed for the treatment of multilevel cervical degenerative disc disease (CDDD). In recent decades, cervical disc arthroplasty (CDA) and hybrid surgery (HS) have been developed to overcome the shortcomings of ACDF. Controversy still remains with regard to the optimal surgical procedure for skip-level CDDD.A total of 55 patients who received surgical treatment for skip-level CDDD in our department were reviewed. The patients were divided into the HS group (n = 29) and the CDA group (n = 26). The collected data included Japanese Orthopedic Association (JOA), Neck Disability Index (NDI), and Visual Analog Scale (VAS) scores, and cervical lordosis (CL), range of motion (ROM), and intervertebral disc height (IDH). Radiological changes at the intermediate segment (IS) were also collected. All data were collected preoperatively and at routine postoperative intervals of 1 week and 3, 6, and 12 months and at the last follow-up period.Compared with preoperative values, mean JOA, NDI, and VAS scores significantly improved after surgery in both the HS and CDA groups (P < .05). However, there were no significant differences between the groups (P > .05). The HS group had better CL recovery than the CDA group after surgery (P < .05). There was no significant difference in the ROM of C2-C7 between the 2 groups (P > .05). A significant difference in the ROM of the IS was found at the last follow-up between the 2 groups (P < .05). At the last-follow-up, 4 discs (14.29%) in the CDA group and 6 discs (19.36%) in the HS group had adjacent segment degeneration (ASD) without symptoms.Both HS and CDA might be considered safe and effective surgical strategies for the treatment of skip-level CDDD. Although the clinical outcomes were similar in the 2 groups, CDA altered the ROM of the IS to a lesser degree.

Artificial Disk Replacement Combined With Fusion Versus 2-Level Fusion in Cervical 2-Level Disk Disease With a 5-Year Follow-up

STUDY DESIGN

Prospective study.

OBJECTIVE

The purpose of this study was to compare the long-term clinical and radiologic outcomes of hybrid surgery (HS) and 2-level anterior cervical discectomy and fusion (2-ACDF) in patients with 2-level cervical disk disease.

SUMMARY OF BACKGROUND DATA

In a previous study with a 2-year follow-up, HS was shown to be superior to 2-ACDF, with a better Neck Disability Index (NDI) score, less postoperative neck pain, faster C2-C7 range of motion (ROM) recovery, and less adjacent ROM increase.

MATERIALS AND METHODS

Between 2004 and 2006, 40 patients undergoing 2-level cervical disk surgery at our hospital were identified as 2-level degenerative disk disease. Forty patients were included in the previous study; 35 patients were followed up for 5 years. Patients completed the NDI and graded their pain intensity before surgery and at routine postoperative until 5 years. Dynamic cervical radiographs were obtained before surgery and at routine postoperative intervals and the angular ROM for C2-C7 and adjacent segments was measured.

RESULTS

The HS group had better NDI recovery until 3 years after surgery (P<0.05). Postoperative neck pain was lower in the HS group at 1 and 3 years after surgery (P<0.05), but arm pain relief was not differently relieved. The HS group showed more angular ROM for C2-C7 at 2 and 3 years after surgery. The superior adjacent segment ROM showed hypermobility in the 2-ACDF group and hypomobility in the HS group at all follow-up periods without statistically significance, but the inferior adjacent segment ROM differed significantly (P<0.05).

CONCLUSION

HS is superior to 2-ACDF; it leads to better NDI recovery, less postoperative neck pain, faster C2-C7 ROM recovery, and less adjacent ROM increase over a 2-year follow-up, but these benefits of HS become similar to those of 2-ACDF with 5 years of follow-up.

Clinical and radiographic features of hybrid surgery for the treatment of skip-level cervical degenerative disc disease: A minimum 24-month follow-up

We describe the radiographic changes of IS and investigate the safety and feasibility of hybrid surgery (HS) coupling cervical disc arthroplasty (CDA) and anterior cervical discectomy and fusion (ACDF) for the treatment of skip-level cervical degenerative disc disease (CDDD). Twenty-seven patients who received HS were retrospectively reviewed. Clinical evaluation based on the Japanese Orthopedic Association (JOA) and Neck Disability Index (NDI) and Visual Analog Scale (VAS) scores. Radiographic parameters included cervical alignment (CA), functional spine unite (FSU) angle of intermediated segment (IS), range of motion (ROM) and intervertebral disc height (IDH). Data regarding radiographic changes at IS were collected. The mean follow-up duration of 30.10months. Compared with preoperative value, JOA, NDI and VAS scores significantly improved after surgery (p<0.05). The CA was recovered significantly after surgery (p<0.05). There was no significant difference in the FSU angle and the IDH of IS between before and at 24months postoperatively (p>0.05). The ROM of IS significantly decreased at the first week after surgery (p<0.05), was similar to preoperative value at 3months postoperatively and significantly increased after 6months (p<0.05). Radiographic changes at IS were observed in 2 patients and Class II Heterotopic ossification (HO) was detected in 2 patients. HS is a safe and feasible alternative procedure for the treatment of skip-level CDDD. It preserved the IS intact and achieved satisfactory clinical and radiographic outcomes over a 24-month follow-up.

Four-level anterior cervical discectomy and fusion for cervical spondylotic myelopathy

PURPOSE

To review the outcome of 32 consecutive patients who underwent 4-level anterior cervical discectomy and fusion (ACDF) with cages and plates and were followed up for at least 5 years.

METHODS

Records of 19 men and 13 women aged 48 to 69 years who underwent 4-level ACDF with cages and plates for myelopathy (n=11) or myeloradiculopathy (n=21) at C3 to C7 by a single surgeon and were followed up for a minimum of 5 years were reviewed. Clinical outcome was assessed using the visual analogue scale (VAS), Neck Disability Index (NDI), and modified Japanese Orthopaedic Association (JOA) score for pain or myelopathic symptoms. Radiographic evaluation included fusion rate, range of motion, cervical lordosis (C2-to-C7 Cobb angle), and disc height.

RESULTS

The mean follow-up was 66 months. All patients had good recovery of muscle strength and resolution of limb sensory disturbance, except for 4 who still had some numbness. The mean VAS for neck and arm pain improved from 14.2 to 6.84 (p=0.012); the mean NDI improved from 31.62 to 12.17 (p<0.01); and the mean JOA score improved from 10.1 to 13.9 (p=0.027). The mean percentage of recovery was 62.9. The mean Cobb angle improved from 10.24º to 1.28º (p=0.019); the mean disc height improved from 4.12 to 6.58 mm (p<0.01). 30 (94%) patients achieved solid fusion.

CONCLUSION

Multilevel ACDF using PEEK cages and plates is safe and effective for multilevel cervical spondylotic myelopathy and achieves satisfactory mid-term outcome.

Treating multi-level cervical disc disease with hybrid surgery compared to anterior cervical discectomy and fusion: a systematic review and meta-analysis

PURPOSE

The traditional surgical approach to treat multi-level cervical disc disease (mCDD) has been anterior cervical discectomy and fusion (ACDF). There has been recent development of other surgical approaches to further improve clinical outcomes. Collectively, when elements of these different approaches are combined in surgery, it is known as hybrid surgery (HS) which remains a novel treatment option. A systematic review and meta-analysis was conducted to compare the outcomes of HS versus ACDF for the treatment of mCDD.

METHODS

Relevant articles were identified from six electronic databases from their inception to January 2016.

RESULTS

From 8 relevant studies identified, 169 patients undergoing HS were compared with 193 ACDF procedures. Operative time was greater after HS by 42 min (p < 0.00001), with less intraoperative blood loss by 26 mL (p < 0.00001) and shorter return to work by 32 days (p < 0.00001). In terms of clinical outcomes, HS was associated with greater C2-C7 range of motion (ROM) preservation (p < 0.00001) and less functional impairment (p = 0.008) after surgery compared to ACDF. There was no significant difference between HS and ACDF with respect to postoperative pain (p = 0.12). The postoperative course following HS was not significantly different to ACDF in terms of length of stay (p = 0.24) and postoperative complication rates (p = 0.18).

CONCLUSIONS

HS is a novel surgical approach to treat mCDD, associated with a greater operative time, less intraoperative blood loss and comparable if not superior clinical outcomes compared to ACDF. While it remains a viable consideration, there is a lack of robust clinical evidence in the literature. Future large prospective registries and randomised trials are warranted to validate the findings of this study.

Biomechanical consideration of prosthesis selection in hybrid surgery for bi-level cervical disc degenerative diseases

PURPOSE

Hybrid surgery (HS) coupling total disc replacement and fusion has been increasingly applied for multilevel cervical disc diseases (CDD). However, selection of the optimal disc prosthesis for HS in an individual patient has not been investigated. This study aimed to distinguish the biomechanical performances of five widely used prostheses (Bryan, ProDisc-C, PCM, Mobi-C, and Discover) in HS for the treatment of bi-level CDD.

METHODS

A finite element model of healthy cervical spine (C3-C7) was developed, and five HS models using different disc prostheses were constructed by arthrodesis at C4-C5 and by arthroplasty at C5-C6. First, the rotational displacements in flexion (Fl), extension, axial rotation, and lateral bending in the healthy model under 1.0 Nm moments combined with 73.6 N follower load were achieved, and then the maximum rotations in each direction combined with the same follower load were applied in the surgical models following displacement control testing protocols.

RESULTS

The range of motion (ROM) of the entire operative and adjacent levels was close to that of the healthy spine for ball-in-socket prostheses, that is, ProDisc-C, Mobi-C, and Discover, in Fl. For Bryan and PCM, the ROM of the operative levels was less than that of the healthy spine in Fl and resulted in the increase in ROMs at the adjacent levels. Ball-in-socket prostheses produced similar reaction moments (92-99 %) in Fl, which were close to that of the healthy spine. Meanwhile, Bryan and PCM required greater moments (>130 %). The adjacent intradiscal pressures (IDPs) in the models of ball-in-socket prostheses were close to that of the healthy spine. Meanwhile, in the models of Bryan and PCM, the adjacent IDPs were 25 % higher than that of the ball-in-socket models. The maximum facet stress in the model of Mobi-C was the greatest among all prostheses, which was approximately two times that of the healthy spine. Moreover, Bryan produced the largest stress on the bone-implant interface, followed by PCM, Mobi-C, ProDisc-C, and Discover.

CONCLUSION

Each disc prosthesis has its biomechanical advantages and disadvantages in HS and should be selected on an individual patient basis. In general, ProDisc-C, Mobi-C, and Discover produced similar performances in terms of spinal motions, adjacent IDPs, and driving moments, whereas Bryan and PCM produced similar biomechanical performances. Therefore, HS with Discover, Bryan, and PCM may be suitable for patients with potential risk of facet joint degeneration, whereas HS with ProDisc-C, Mobi-C, and Discover may be suitable for patients with potential risk of vertebral osteoporosis.

Comparison of Hybrid Surgery Incorporating Anterior Cervical Discectomy and Fusion and Artificial Arthroplasty versus Multilevel Fusion for Multilevel Cervical Spondylosis: A Meta-Analysis

BACKGROUND Few studies have reported the safety and efficacy of hybrid surgery (HS), and some of the studies comparing HS with ACDF have reported conflicting results. We conducted this meta-analysis to clarify the advantages of HS in the treatment of multilevel cervical spondylosis. MATERIAL AND METHODS We performed a systematic literature search in PubMed, Medline, and CNKI to identify relevant controlled trials published up to October 2015. The standardized mean difference (SMD) and 95% confidence interval (95% CI) of the perioperative parameters, visual analogue scale pain score (VAS), neck disability index (NDI), and range of motion (ROM) of C2-C7 and adjacent segments were calculated. We also analyzed complications and Odom scale scores using risk difference (RD) and 95% CI. RESULTS In total, 7 studies were included. The pooled data exhibited significant differences in blood loss between the 2 groups. However, there was no evidence indicating significant differences in operation time, complications, VAS, NDI, or Odom scale scores. Compared with the ACDF group, the HS group exhibited significantly protected C2-C7 ROM and reduced adjacent-segment ROM. CONCLUSIONS The safety of HS may be as good as that of ACDF. Furthermore, HS is superior to ACDF in conserving cervical spine ROM and decreasing adjacent-segment ROM. However, the results should be accepted cautiously due to the limitations of the study. Studies with larger sample sizes and longer follow-up periods are required to confirm and update the results of the present study.

Biomechanics of Artificial Disc Replacements Adjacent to a 2-Level Fusion in 4-Level Hybrid Constructs: An In Vitro Investigation

Background

The ideal procedure for multilevel cervical degenerative disc diseases remains controversial. Recent studies on hybrid surgery combining anterior cervical discectomy and fusion (ACDF) and artificial cervical disc replacement (ACDR) for 2-level and 3-level constructs have been reported in the literature. The purpose of this study was to estimate the biomechanics of 3 kinds of 4-level hybrid constructs, which are more likely to be used clinically compared to 4-level arthrodesis.

Material/Methods

Eighteen human cadaveric spines (C2–T1) were evaluated in different testing conditions: intact, with 3 kinds of 4-level hybrid constructs (hybrid C3–4 ACDR+C4–6 ACDF+C6–7ACDR; hybrid C3–5ACDF+C5–6ACDR+C6–7ACDR; hybrid C3–4ACDR+C4–5ACDR+C5–7ACDF); and 4-level fusion.

Results

Four-level fusion resulted in significant decrease in the C3–C7 ROM compared with the intact spine. The 3 different 4-level hybrid treatment groups caused only slight change at the instrumented levels compared to intact except for flexion. At the adjacent levels, 4-level fusion resulted in significant increase of contribution of both upper and lower adjacent levels. However, for the 3 hybrid constructs, significant changes of motion increase far lower than 4P at adjacent levels were only noted in partial loading conditions. No destabilizing effect or hypermobility were observed in any 4-level hybrid construct.

Conclusions

Four-level fusion significantly eliminated motion within the construct and increased motion at the adjacent segments. For all 3 different 4-level hybrid constructs, ACDR normalized motion of the index segment and adjacent segments with no significant hypermobility. Compared with the 4-level ACDF condition, the artificial discs in 4-level hybrid constructs had biomechanical advantages compared to fusion in normalizing adjacent level motion.