INTRODUCTION
The concept of spine arthrodesis surgery was given by Albee over hundred years ago for Pott’s spine.[1] Since the inception, this surgery has been the most widely performed spine surgery procedure with an incidence of around 400,000 fusion surgeries conducted in the US alone every year.[2]Over the years, the indications for fusion surgery have been increasing drastically. Early success rates of fusion surgery during the evolution masked the long-term complications of the surgery. Reoperation rates following the fusion surgery were reported to be around 20% at 5 years from the primary surgery.[3,4] Studies suggest that adjacent segment disease (ASD) forms the major indication for reoperation in the long-term accounting for up to 51% of reoperations.[5,6] Initially, the cause for ASD was attributed to increased stress on the adjacent segment following fusion.[7] Recent studies have theorized that damage to the paraspinal muscle and ligaments in open surgical procedures, as compared to percutaneous procedures, is one of the reasons for ASD.[8,9] However, the big question is whether ASD is actually an entity, and one school of thought believes that changes in adjacent segments are due to the natural course of the degenerative process.[10,11] There are few evidences of genetical predispositions for degenerative disease supporting this debate of biological etiology.[12]
As the number of fusion surgeries increases in number so are the number of revision surgeries and also the surgeries to prevent ASD, that is, motion preservation technologies. Even though there are various indications for their usage, their results are inconsistent.[13,14]
The objective of this review is to give the reader a brief overview of adjacent segment pathology and motion preservative technologies, their current status, and long-term outcome through evidence-based literature review.
MATERIALS AND METHODS
A search was conducted in PubMed using the terms (“adjacent segment”) AND (“disease” OR “degeneration” or “pathology”). The articles were then shortlisted based on time of publication (2005 onward), publication in English and inclusion of human subjects. This resulted in 253 articles. Another search for ((“Motion preservation”) AND (“Spine”)) OR (“Adjacent segment disease”) OR (“Adjacent segment pathology”) OR (“Adjacent segment degeneration”) yielded 76 articles. The manuscripts were excluded if they were letters, editorials, commentaries, case series, etc. Once studies had been identified, duplicates were removed, and then the titles and abstracts of the remaining articles were screened by two independent reviewers. They checked the title and abstract of all the studies for relevance. In case of disagreement, consensus was obtained by mutual discussion.
DEFINITION
Adjacent segment degeneration (ASDgen) refers to the radiographic changes in the intervertebral disc (IVD) adjacent to the operated spinal level, regardless of the presence of symptoms. Radiographic criteria, which can be considered ASDgen, are given in Table 1.[9] Symptomatic ASDgen is called adjacent segment disease (ASDz).[15] Because of the lack of precision in describing these terminologies. Lawerence et al.,[16] in their systematic review, proposed the term adjacent segment pathology (ASP), which covers both clinical adjacent segment pathology (CASP) and radiological adjacent segment pathology (RASP) [Table 1].
;)
Table 1: Radiographic criterion for ASDgen
ETIOPATHOGENESIS
The biomechanics of spine is complex. IVDs behave like biological shock absorbers transmitting forces from one level to the next for appropriate spinal column mobility. It is subjected to diverse loading conditions. The complex functional orchestra of supporting structures results in physiological segmental movement, which is compatible in protecting neurological structures.[17]
According to a meta-analysis, which included 55 studies, the incidence of lumbar ASP requiring reoperation was up to 8%,[18] and in cervical spine, it was up to 2.4%–3% per year.[19]
Motion segment fusion increases stress in the adjacent disc due to the nonphysiological center of motion and long lever arm.[20] A 20% increase in shear strain in the adjacent disc was seen following multiple-level fusion surgery.[21] Flexion and extension moment increases intra discal pressure by 73.2% and 45.3% proximal and distal to fusion segment, respectively.[22]
Sagittal alignment of the spine has got an important role to play in the pathogenesis of ASP. Park et al.[23] stated that malalignment at cervical fusion level increased the chances of CASP. Lumbar spine fused in hypo lordosis showed an increase in shear forces by 29% in the adjacent segment.[24]
Biochemical factors are also a reason for the development of ASDgen. A static compression promotes catabolic response in the adjacent disc and the other way round in the dynamic compression mode.[25,26] Abnormal loading in the adjacent disc triggers pro-inflammatory cytokines IL-1b and TNF-alpha, which degrades the proteoglycans and activates catabolic enzymes.[27] Disc is an inherently hypoxic structure. A small increase in compression or an abnormal mobility reduces the diffusion of oxygen and nutrients across the endplates, accelerating disc degeneration and in turn ASD.[28,29]
There are also studies that propose ASP is a part of multilevel degenerative spine disease.[10,11] Wang and Ding[30] conducted a meta-analysis that compared the corelation between the presence of degeneration in adjacent disc preoperatively using Pfirrmann’s classification and the incidence of ASD in these cases postoperatively. They concluded that the incidence of ASD increases in postoperative period with a higher grade of Pfirrmann’s classification. This has been supported by the fact that the rate of ASD in spine fused for traumatic and congenital etiology was less compared to degenerative etiology.[31] Hence, preexisting disease also plays a role in its etiopathogenesis. But whether ASD is a consequence of fusion or it is related to ongoing degeneration is still a debate.
Of late, there has been a lot of research on genomic studies, which has shown predisposing genes for disc degeneration.[32]
In future, it might facilitate defining a high-risk population with the help of genetic mapping.
Risk factors
Risk factors for ASP after lumbar and cervical fusion surgery have been mentioned in Tables 2 and 3, respectively.
Table 2: Risk factors for ASP after lumbar fusion surgery[33]
Table 3: Risk factors for ASP after cervical fusion surgery[33]
Depicting ASD following lumbar and cervical fusion with literature review [Tables 4 and 5].
Table 4: Important studies on lumbar adjacent segment failure
Table 5: Important studies on cervical adjacent segment failure
STRATEGIES TO AVOID ADJACENT SEGMENT PATHOLOGY IN LUMBAR AND CERVICAL SPINE: MOTION PRESERVING SURGERIES
It is a long-term controversy whether ASPs, like ASDz and ASDgen, are separate entities or simply reflections of the natural history of cervical and lumbar degenerative disease or iatrogenic induced.[30] Now focus has shifted to prevent future ASPs due to the index surgery, which lead to the concept of motion-preserving surgeries.[46]
The aim of motion-preserving surgeries is to replicate the near-normal biomechanics with a view to minimize the chances of the development of ASPs. It is simply restoring the function of motion segment. In the last decade, there has been a significant increase in the use of motion preservation surgery, especially cervical disc replacement, with up to 17% increase in cervical disc replacement per year.[47]
Motion-preserving devices can be categorized into four main types [Table 6]:
Table 6: Summary of the motion preserving surgeries and its evidence
- (1) Total disc replacement (TDR),
- (2) Prosthetic nucleus replacement,
- (3) Posterior dynamic devices, and
- (4) Facet replacement.
TDR
TDRs necessitate complete removal of the disc. It contains endplate portions, which is usually metallic component and are fixed to the vertebral endplates. The articulating portion of the device is interposed between the endplates portion and can be composed of various materials.
Lumbar total disc replacement (LTDR)
Biomechanical and kinematic studies have depicted that increased load and movement in adjacent segment leads to early degeneration of adjacent disc. The benefits of motion preservation and protection of adjacent discs from nonphysiologic loading make prosthetic replacement of the IVD a potentially attractive choice.
The LTDR must restore motion, have the ability to transmit and absorb loads and permit translation to accommodate changes in the axis of rotation. It should restore foraminal, disc height, and sagittal alignment.
There are three main LTDR designs[54] for the lumbar spine [Figures 1-3]:
Figure 1: Lumbar disc replacement prosthesis (a) Charite’ III (Depuy Acromed Inc., Mountain View, California), (b) InMotion (DePuy Spine, Raynham, Massachusetts), (c) Kineflex (Spinal Motion, Mountain View, California)
Figure 2: Lumbar disc replacement prosthesis (a) Maverick (Medtronic Sofamor Danek, Memphis, Tennessee), (b) Flexicore (Stryker, Allendale, New Jersey), (c) ProDisc (ProDiscSynthes Inc., West Chester, Pennsylvania)
Figure 3: Lumbar disc replacement prosthesis (a) Activ-L (Aesculap B. Braun, Tuttlingen, Germany), (b) Freedom (Axiomed Spine, Cleveland, Ohio), (c) Triumph (Globus Medical, Audubon, Pennsylvania), (d) Mobidisc (LDR, Troyes, France), (e) XL TDR (NuVasive, San Diego, California)
- (1) the three-component ball and socket design with gliding surfaces (Charite, InMotion, Kineflex-L),
- (2) the two-component ball and socket design with gliding surfaces (Maverick, Flexicore), and
- (3) the one-piece design (Freedom, M6-L).
Indications of LTDR[55]
Lumbar TDR is indicated for patient with severe discogenic low back pain who have failed conservative trial. Patient selection remains an important aspect in attaining optimal outcomes.
- Age 18–60 years,
- Male or female with visual analog scale (VAS) > 4 and Oswestry score > 40%, and
- Symptomatic DDD with radiographic evidence: vacuum disc sign, Modic changes, contained herniated disc, high-intensity zone signal, absence of facet degeneration.
Contraindications of LTDR[55]
There are various contraindications for the use of lumbar TDR
- Posterior element disease (facet joint arthritis or previous facet joint resection),
- Spondylolisthesis,
- Spondylosis, and
- Fixed deformity.
A systematic review was conducted by Cui et al.[56] in which 13 studies were considered for the determination of the mid and long-term outcomes of total lumbar disc replacement. It showed that patients had a satisfactory clinical outcome ranging from good to excellent in 75.5%–93.3% (in the last follow-up). 65.9% of the patients had part-time or full-time job following the LTDR. Amongst the 13 studies, 10 had reported complication rates, which ranged from 0% to 34.4%, and reoperation rates of 0%–39.3%. It is to be noted that 8 out of 13 studies showed reoperation rates of less than 10%.
However, two studies showed reoperation rates of more than 30%. These studies were on the use of AcroFlex prosthesis with high reoperations rates between 33% and 39.3%. Even though the mid and long-term results of this study were favorable, they failed to establish superiority over fusion procedures.
The majority of experts concur that one of the most crucial elements influencing TDR outcomes is patient selection. Lumbar TDR may be a good alternative to lumbar fusion, particularly for young patients with DDD who don’t have any major facet joint degeneration, deformity, instability, or osteopenia/osteoporosis. However, worries about long-term results, implant durability, and potential extremely late problems may still prevent lumbar TDR from being widely used.
CERVICAL TOTAL DISC REPLACEMENT (CTDR)
Both CTDR and LTDR rely on the same principle of neural decompression in addition to maintaining near-normal motion,[57] maintaining segmental lordosis, and maintaining anatomical disc height.[58] Although the outcomes of ACDF are safe and effective over decades, CTDR counters the negative aspect of the ACDF.[59]
Indications for CTDR are[60]:
- Requirement of surgical treatment at one to two levels from C3 to T1 after a failed conservative treatment lasting at least 6 weeks for any one or more of the following: (1) PIVD with radiculopathy, (2) spondylotic radiculopathy, (3) PIVD with myelopathy, or (4) spondylotic myelopathy.
Contraindications for CTDR are[60]:
- Ankylosing spondylitis, rheumatoid arthritis, OPLL, or diffuse idiopathic skeletal hyperostosis,
- Insulin-requiring diabetes mellitus,
- Prior cervical spinal infection,
- Chronic steroid use or a medical condition requiring,
- Chronic steroid administration, and
- Obesity.
The artificial cervical discs, which are approved, include Bryan disc, Prestige ST, Mobi-C, ProDisc C PCM, Secure C, and Prestige LP [Figure 4].[61]
Figure 4: Cervical disc replacement prosthesis (a) Mobi-C (LDR Spine USA, Inc., Austin, TX, USA), (b) Prodisc-C (Synthes Spine, Paoli, PA, USA), (c) Bryan (Medtronic Sofamor Danek, Memphis, TN, USA), (d) Prestige ST (Medtronic Sofamor Danek)
A meta-analysis by Peng et al.[62] included 30 RCT’s comparing outcomes of CTDR and ACDF showed that prolonged surgical time, better overall neurological success, and neck disability index (NDI) success rates were found in CTDR in short-, mid-, and long-term follow-up periods, with lower dysphagia/dysphonia during short-term follow-up. CTDR group showed a lower incidence of ASD, and reoperation rates in long-term follow-up periods. Comparable length of hospital stay and blood loss were found in both groups.
Wang et al.[63] in their meta-analysis of 11 RCT’s concluded in comparison to ACDF, CTDR achieved significantly higher overall success rates, improvement of NDI, neurological success, patients’ satisfaction. Functional outcome measures such as VAS for neck pain and upper limb pain, the Short Form-36 (SF-36 PCS), and the Short Form-36 (SF-36 MCS) revealed superiority in the CTDR group. CTDR group had a lower rate of symptomatic adjacent segment, resurgery at the index level, and surgery at the adjacent level.
Meta-analysis by Gao et al.,[64] Luo et al.,[65] Rao et al.,[66] and Findlay et al.[67] showed similar findings with a superiority of ADR over ACDF.
CTDR is a great surgical choice since it preserves segmental mobility, has the potential to lessen ASP, and doesn’t require plating or bone graft harvesting. The body of research supporting the efficacy and durability of arthroplasty is expanding, and it is a crucial technique in a spine surgeon’s toolbox.
Prosthetic nucleus replacement
On the contrary to TDR, prosthetic nucleus replacements necessitate evacuation of only the nucleus pulposus through an annulotomy. Otherwise, the annulus remains largely intact. The implant is usually a deformable material that is inserted into the disc space with or without a fixation method.
Ray[68] designed prosthetic disc nucleus (PDN) and also its subsequent design changes (PDN; Raymedica, Minneapolis, MN). Indications for PDN are discogenic low-back pain due to degenerative disc disease (DDD) or postdiscectomy. PDN implantation is done through standard laminectomy and annulotomy approach. Hydrophilic gel pillow that absorbs water and expands once implanted form the vital component of PDN. Prevention of device expulsion postimplantation forms the core strategy for implant design[69] [Figure 5].
Figure 5: Prosthetic nucleus replacement. (a) PDN (Raymedica, Minneapolis, Minnesota), and (b) DASCOR (Disc Dynamics, Eden Prairie, Minnesota)
Currently, in the United States of America, no nucleus replacements or augmentation devices are approved. Complications of nucleus replacement devices typically include (1) implant expulsion, especially with devices without any fixation points, because annulotomy is done to introduce the device; (2) subsidence due to stress shielding in the center of the endplate; (3) endplate remodeling with disc height collapse; and (4) poor disc kinematics resulting in canal stenosis and facet arthritis or fracture.[70,71]
Presently, there is a lack of any level 1 evidence to ascertain the clinical efficacy of nuclear disc replacement. But a retrospective review to determine the long-term results of the DASCOR system (Disc Dynamics, Eden Prairie, MN) by Golan et al.[53] showed that out of 22 patients, mean ODI was 33.4 ± 18.4 and mean VAS was 4 ± 2.8, and both were on improvement side. Among these, 46% patients developed ASDgen in follow-up, revision surgery rates were high with six patients undergoing surgery at index level and three patients needing surgery at adjacent level.
When suggesting nuclear replacement as a treatment for individuals with DDD, the surgeon must evaluate endplate integrity, disc height, endplate form, annular integrity, and BMI.
Posterior Dynamic Devices
Posterior dynamic devices are of many forms. Dynamic, or so-called soft stabilization and semirigid are both typically pedicle screw based. The screws are connected by a flexible longitudinal rod. Currently available devices vary from articulating ball joints to longitudinal Silastic rods.
Interspinous devices can also be considered posterior dynamic stabilization devices. These devices consist of an implant that is interposed between the adjacent spinous processes. Some are held in place by their design alone, whereas others require supplemental tethering fixation.
The dynamic stabilization systems may be classified into four categories as follows:
- Interspinous distraction devices (Minns silicone distraction device Wallis system X-stop),
- Inter-spinous ligament devices (elastic ligament (Bronsard’s ligament across the spinous processes) loop system),
- Ligaments across pedicle screws (Graf ligament, dynesis device), and
- Semirigid metallic devices across the pedicle screws (FASS (fulcrum assisted soft stabilization) system DSS (dynamic soft stabilization) system).
DYNAMIC STABILIZATION
Dynamic fixation of the lumbar spine would favorably alter the movement and load the transmission of a spinal motion segment without the intention of fusion.[72] A dynamic stabilization, also known as soft stabilization or flexible stabilization, leaves the spinal segment mobile, and its intention is to alter the load-bearing pattern of the motion segment, as well as to control any abnormal motion at the segment.[73]
The flexibility of these systems is achieved by either of the two different configurations of these implants: flexible rods or special connections (dampers or hinges) between pedicle screws and rigid rods (Isobar TTL Semi-rigid Spinal System, Cosmic Posterior Dynamic System). As far as flexible rods are concerned, their flexibility is derived from the fact that these rods are made either of elastic materials like polyethylene (Dysnesys, Zimmer) or PEEK (CD-Horizon Legacy PEEK Rod), or of rigid materials manufactured in such a way that some degree of flexibility is possible (i.e., in the case of AccuFlex Rod System the double helical cuts in the rods make the rods to bend) [Figures 6, 7].[74,75]
Figure 6: Posterior dynamic stabilization. (a) PercuDyn (Interventional Spine, Irvine, California), (b) IsoBar (Scient’X, Beaurains, France), (c) Stabilimax (Applied Spine Technologies, New Haven, Connecticut), (d) Transition (Globus Medical, Audubon, Pennsylvania)
Figure 7: Posterior dynamic stabilization. (a) AcccuFlex (Globus Medical, Audubon, Pennsylvania), (b) Graf system (Graf ligamentous system, France), (c) Dynesys (Zimmer Spine, Minneapolis, MN)
Indications
Indications for this type of implant include[73]: (1) moderate DDD, (2) mild facet arthropathy, and (3) low-grade spondylolisthesis or instability and spinal stenosis (always with an additional decompressive procedure).
Contraindications[76]
Spinal instability and listhesis greater than grade 1, advanced DDD or disc collapse more than 50%, osteoporosis, and scoliotic deformity.
In individuals with degenerative lumbar spine, dynamic stabilization system does provide good and stable clinical mid-term outcomes, and it appears to be a viable option to fusion surgery with similar clinical outcomes but fewer reoperations.[77]
INTERSPINOUS DEVICES
As the name suggests, these are positioned in the interspinous region of the vertebrae and distracts the posterior aspect of the motion segment. This distraction of the posterior elements leads to the decompression of neural elements through three different mechanisms.[78]
- (a) Increase in the dimension of neural foramens, especially in foraminal stenosis,
- (b) Unbuckling and stretching of the buckled ligamentum flavum,
- (c) Distraction of the posterior aspect of the disc and also vertebral body resulting in decompression of the anterior–central part of the spinal canal.
Interspinous devices are broadly classified into restricted and unrestricted devices. Restricted devices (Wallis, Diam, intraspine) control both excessive flexion and extension, acting as dynamic stabilization devices, while unrestricted devices (X-STOP. Aperious, Bacjac, Ellipse, etc.) limit only the excessive extension of the spine. Limitation of spinal flexion in the case of restricted implants is achieved through synthetic laces attached to the cranial and caudal spinous processes [Figure 8].[50]
Figure 8: Interspinous devices. (a) DIAM system (Medtronic Sofamor Danek), (b) CoFlex (Paradigm Spine LLC, New York, New York), (c) X-stop (Kyphon, Sunnyvale, California), (d) Wallis system (Abbott Spine, Austin, TX; acquired in 2008 by Zimmer)
Tram et al.,[79] in their systematic review comparing traditional decompressive surgery versus interspinous devices, showed that there was no collective advantage of one procedure over the other, and both were unique surgical interventions with different therapeutic efficacies and complications.
Wu et al.,[80] in their systematic review and meta-analysis, concluded that they obtained some benefits in the interspinous device group, but it was not significant as compared to only decompression group. However, interspinous spacers had a higher incidence of complications, reoperation, and higher cost as compared to the decompression group. Li et al.[81] conducted a systematic review of RCT’s and the pooled analysis showed a higher reoperation rate with interspinous devices. These devices were not superior in giving symptomatic relief in neurological claudication as compared to laminectomy.
Due to a lack of significant clinical and surgical evidence of safety and efficacy in published peer‐reviewed medical research, justification of interspinous devices usage is still questionable. Additional clinical studies are required to demonstrate the effectiveness with reference to postoperative results.
FACET REPLACEMENT
As the disc height reduces in the degenerative cascade of the IVD, facet load increases leading to facet arthritis and osteophyte formation, causing low-back pain. Facet replacement is an invasive procedure as compared to interspinous devices, wherein a laminectomy followed by bilateral facetectomy is performed, and a prosthetic facet device implanted. Facet replacement decompresses the canal and foraminal stenosis and also provides some motion at the affected level.
Total facet arthroplasty system (TFAS) is a pedicle-based sliding ball-in-bowl-type joint system. Its indication includes lumbar canal stenosis. TFAS, unlike fusion procedure, retains segmental motion and provides stability, and restores lumbar lordosis.[82]
TOPS is another facet joint replacement system that is composed of titanium construct, which has interlocking, flexible articulating core, surrounded by polyurethane elastomer cover, which is capable of transmitting tensile and compressive loads in addition to shear forces. Two other systems for facet replacement are ACADIA and Stabilmax NZ [Figure 9].
Figure 9: Facet replacement. (a) TFAS (Archus Orthopedics, Redmond, Washington), (b) ACADIA (Globus Medical, Audubon, Pennsylvania), (c) TOPS (Impliant’s system Princeton, New Jersey)
Four multicentre, prospective, RCT’s analyzing the long-term results of four distinct total facet arthroplasty (TFA) devices were conducted in the US since early 2000. These studies were given permission by the US FDA as investigational device exemption studies. Dismal results of these trials lead to the unavailability of the TFA products commercially.[52,82]
Any recommendations for treatment using artificial facet joints are presently not attainable because clinical trials have not yet been completed, and there is an inadequate amount of clinical data. Position statements and guidelines on motion preserving surgeries of various well known societies has been mentioned in Table 7.
Table 7: Position statements and guidelines regarding motion preservation surgeries
CONCLUSION
ASDgen is very commonly seen after cervical and lumbar fusion. However, ASDz is still an enigma, and regular follow-up is required. Evidence supports alteration in biomechanical properties in adjacent segments, both proximal and distal to fusion levels. With a shift in focus to restore the near-normal biomechanics of adjacent segments, various types of motion preservation surgeries have been developed, and there is ongoing research with varying levels of evidence for each type. There is Level I evidence in favour of cervical disc replacement, lumbar disc replacement as well as posterior dynamic stabilization and Level II evidence in favour of Interspinous devices. However, Level IV evidence in favour of lumbar facet replacement as well as nucleus pulposus replacement. Thus justification for the use of motion preservation surgeries is still investigational and is subjected to outcomes of well-conducted long-term studies, especially for motion preservation surgeries other than cervical and lumbar disc replacement.[90]
Ethical policy and institutional review board statement
Not applicable.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
REFERENCES
1. Albee FH. THE CLASSIC: Transplantation of a portion of the Tibia into the Spine for Pott’s disease: A preliminary report Clin Orthop. 2007;460:14–6
2. Rajaee SS, Bae HW, Kanim LEA, Delamarter RB. Spinal fusion in the United States: Analysis of trends from 1998 to 2008 Spine. 2012;37:67–76
3. Sato S, Yagi M, Machida M, Yasuda A, Konomi T, Miyake A, et al Reoperation rate and risk factors of elective spinal surgery for degenerative spondylolisthesis: Minimum 5-year follow-up Spine J. 2015;15:1536–44
4. Lad SP, Babu R, Ugiliweneza B, Patil CG, Boakye M. Surgery for spinal stenosis: Long-term reoperation rates, health care cost, and impact of instrumentation Spine. 2014;39:978–87
5. Gerling MC, Leven D, Passias PG, Lafage V, Bianco K, Lee A, et al Risk factors for reoperation in patients treated surgically for lumbar stenosis: A subanalysis of the 8-year data from the SPORT trial Spine. 2016;41:901–9
6. Gerling MC, Leven D, Passias PG, Lafage V, Bianco K, Lee A, et al Risk factors for reoperation in patients treated surgically for degenerative spondylolisthesis: A subanalysis of the 8-year data from the SPORT trial Spine. 2017;42:1559–69
7. Hilibrand AS, Robbins M.
Adjacent segment degeneration and
adjacent segment disease: the consequences of spinal fusion? Spine J. 2004;4:S190–4
8. Bresnahan L, Ogden AT, Natarajan RN, Fessler RG. A biomechanical evaluation of graded posterior element removal for treatment of lumbar stenosis: Comparison of a minimally invasive approach with two standard laminectomy techniques Spine. 2009;34:17–23
9. Regev GJ, Lee YP, Taylor WR, Garfin SR, Kim CW. Nerve Injury to the posterior rami medial branch during the insertion of pedicle screws: Comparison of mini-open versus percutaneous pedicle screw insertion techniques Spine. 2009;34:1239–42
10. Song KJ, Choi BW, Jeon TS, Lee KB, Chang H. Adjacent segment degenerative disease: Is it due to disease progression or a fusion-associated phenomenon? Comparison between segments adjacent to the fused and non-fused segments Eur Spine J. 2011;20:1940–5
11. Saavedra-Pozo FM, Deusdara RAM, Benzel EC.
Adjacent segment disease perspective and review of the literature Ochsner J. 2014;14:78–83
12. Patel AA, Spiker WR, Daubs M, Brodke D, Cannon-Albright LA. Evidence for an inherited predisposition to lumbar disc disease J Bone Jt Surg. 2011;93:225–9
13. Gelalis ID, Papadopoulos DV, Giannoulis DK, Tsantes AG, Korompilias AV. Spinal motion preservation surgery: Indications and applications Eur J Orthop Surg Traumatol. 2018;28:335–42
14. Park P, Garton HJ, Gala VC, Hoff JT, McGillicuddy JE.
Adjacent segment disease after lumbar or lumbosacral fusion: Review of the literature Spine. 2004;29:1938–44
15. Harrop JS, Youssef JA, Maltenfort M, Vorwald P, Jabbour P, Bono CM, et al Lumbar
adjacent segment degeneration and disease after arthrodesis and total disc arthroplasty Spine. 2008;33:1701–7
16. Lawrence BD, Wang J, Arnold PM, Hermsmeyer J, Norvell DC, Brodke DS. Predicting the risk of
adjacent segment pathology after lumbar fusion: A systematic review Spine. 2012;37:S123–132
17. Fujii R, Sakaura H, Mukai Y, Hosono N, Ishii T, Iwasaki M, et al Kinematics of the lumbar spine in trunk rotation: in vivo three-dimensional analysis using magnetic resonance imaging Eur Spine J. 2007;16:1867–74
18. Burch M, Wiegers N, Patil S, Nourbakhsh A. Incidence and risk factors of reoperation in patients with
adjacent segment disease: A meta-analysis J Craniovertebral Junction Spine. 2020;11:9
19. Zhu Y, Zhang B, Liu H, Wu Y, Zhu Q. Cervical disc arthroplasty versus anterior cervical discectomy and fusion for incidence of symptomatic
adjacent segment disease: A meta-analysis of prospective randomized controlled trials Spine. 2016;41:1493–502
20. Prasarn ML, Baria D, Milne E, Latta L, Sukovich W. Adjacent-level biomechanics after single versus multilevel cervical spine fusion: Laboratory investigation J Neurosurg Spine. 2012;16:172–7
21. Matsunaga S, Kabayama S, Yamamoto T, Yone K, Sakou T, Nakanishi K. Strain on intervertebral discs after anterior cervical decompression and fusion Spine. 1999;24:670–5
22. Eck JC, Humphreys SC, Lim TH, Jeong ST, Kim JG, Hodges SD, et al Biomechanical study on the effect of cervical spine fusion on adjacent-level intradiscal pressure and segmental motion Spine. 2002;27:2431–4
23. Chung JY, Park JB, Seo HY, Kim SK.
Adjacent segment pathology after anterior cervical fusion Asian Spine J. 2016;10:582
24. Senteler M, Weisse B, Rothenfluh DA, Farshad MT, Snedeker JG. Fusion angle affects intervertebral adjacent spinal segment joint forces—Model-based analysis of patient specific alignment J Orthop Res. 2017;35:131–9
25. Wang DL, Jiang SD, Dai LY. Biologic response of the intervertebral disc to static and dynamic compression in vitro Spine. 2007;32:2521–8
26. Xia W, Zhang LL, Mo J, Zhang W, Li HT, Luo ZP, et al Effect of static compression loads on intervertebral disc: an in vivo bent rat tail model Orthop Surg. 2018;10:134–43
27. Molinos M, Almeida CR, Caldeira J, Cunha C, Gonçalves RM, Barbosa MA. Inflammation in intervertebral disc degeneration and regeneration J R Soc Interface. 2015;12:20150429
28. Risbud MV, Guttapalli A, Albert TJ, Shapiro IM. Hypoxia activates MAPK activity in rat nucleus pulposus cells: Regulation of integrin expression and cell survival Spine. 2005;30:2503–9
29. Tao Y, Zhou X, Liang C, Li H, Han B, Li F, et al TGF-β3 and IGF-1 synergy ameliorates nucleus pulposus mesenchymal stem cell differentiation towards the nucleus pulposus cell type through MAPK/ERK signaling Growth Factors. 2015;33:326–36
30. Wang T, Ding W. Risk factors for
adjacent segment degeneration after posterior lumbar fusion surgery in treatment for degenerative lumbar disorders: A meta-analysis J Orthop Surg. 2020;15:582
31. Lee MJ, Dettori JR, Standaert CJ, Ely CG, Chapman JR. Indication for spinal fusion and the risk of
adjacent segment pathology: Does reason for fusion affect risk? A systematic review Spine. 2012;37:S40–51
32. Song YQ, Karasugi T, Cheung KMC, Chiba K, Ho DWH, Miyake A, et al Lumbar disc degeneration is linked to a carbohydrate sulfotransferase 3 variant J Clin Invest. 2013;123:4909–17
33. Hashimoto K, Aizawa T, Kanno H, Itoi E.
Adjacent segment degeneration after fusion spinal surgery—A systematic review Int Orthop. 2019;43:987–93
34. Ekman P, Möller H, Shalabi A, Yu YX, Hedlund R. A prospective randomised study on the long-term effect of lumbar fusion on adjacent disc degeneration Eur Spine J. 2009;18:1175–86
35. Rahm MD, Hall BB. Adjacent-segment degeneration after lumbar fusion with instrumentation: A retrospective study J Spinal Disord. 1996;9:392–400
36. Ogawa H, Hori H, Oshita H, Akaike A, Koyama Y, Shimizu T, et al Sublaminar wiring stabilization to prevent
adjacent segment degeneration after lumbar spinal fusion Arch Orthop Trauma Surg. 2009;129:873–8
37. Wimmer C, Gluch H, Krismer M, Ogon M, Jesenko R. AP-translation in the proximal disc adjacent to lumbar spine fusion: A retrospective comparison of mono- and polysegmental fusion in 120 patients Acta Orthop Scand. 1997;68:269–72
38. Park JY, Chin DK, Cho YE. Accelerated L5-S1 segment degeneration after spinal fusion on and above L4-5: minimum 4-year follow-up results J Korean Neurosurg Soc. 2009;45:81
39. Gillet P. The fate of the adjacent motion segments after lumbar fusion J Spinal Disord Tech. 2003;16:338–45
40. Disch AC, Schmoelz W, Matziolis G, Schneider SV, Knop C, Putzier M. Higher risk of
adjacent segment degeneration after floating fusions: Long-term outcome after low lumbar spine fusions J Spinal Disord Tech. 2008;21:79–85
41. Kanayama M, Togawa D, Hashimoto T, Shigenobu K, Oha F. Motion-preserving surgery can prevent early breakdown of adjacent segments: Comparison of posterior dynamic stabilization with spinal Fusion J Spinal Disord Tech. 2009;22:463–7
42. Bolesta MJ, Rechtine GR, Chrin AM. One- and two-level anterior cervical discectomy and fusion: The effect of plate fixation Spine J. 2002;2:197–203
43. Kawakami M, Tamaki T, Yoshida M, Hayashi N, Ando M, Yamada H. Axial symptoms and cervical alignments after cervical anterior spinal fusion for patients with cervical myelopathy J Spinal Disord. 1999;12:50–6
44. Matsumoto M, Okada E, Ichihara D, Watanabe K, Chiba K, Toyama Y, et al Anterior cervical decompression and fusion accelerates
adjacent segment degeneration: Comparison with asymptomatic volunteers in a ten-year magnetic resonance imaging follow-up study Spine. 2010;35:36–43
45. Marotta N, Landi A, Tarantino R, Mancarella C, Ruggeri A, Delfini R. Five-year outcome of stand-alone fusion using carbon cages in cervical disc arthrosis Eur Spine J. 2011;20(S1):8–12
46. Murtagh R, Castellvi AE. Motion preservation surgery in the spine Neuroimag Clin N Am. 2014;24:287–94
47. Jain NS, Nguyen A, Formanek B, Alluri R, Buser Z, Hah R, et al Cervical disc replacement: Trends, costs, and complications Asian Spine J. 2020;14:647–54
48. Nunley PD, Coric D, Frank KA, Stone MB. Cervical disc arthroplasty: Current evidence and real-world application Neurosurgery. 2018;83:1087–106
49. Ding F, Jia Z, Zhao Z, Xie L, Gao X, Ma D, et al Total disc replacement versus fusion for lumbar degenerative disc disease: A systematic review of overlapping meta-analyses Eur Spine J. 2017;26:806–15
50. Fabrizi AP, Maina R, Schiabello L. Interspinous spacers in the treatment of degenerative lumbar spinal disease: Our experience with DIAM and Aperius devices Eur Spine J. 2011;20:20–6
51. Lee CH, Jahng TA, Hyun SJ, Kim CH, Park SB, Kim KJ, et al Dynamic stabilization using the Dynesys system versus posterior lumbar interbody fusion for the treatment of degenerative lumbar spinal disease: A clinical and radiological outcomes-based meta-analysis Neurosurg Focus. 2016;40:E7
52. McAfee P, Khoo LT, Pimenta L, Capuccino A, Coric D, Hes R, et al Treatment of lumbar spinal stenosis with a total posterior arthroplasty prosthesis: Implant description, surgical technique, and a prospective report on 29 patients Neurosurg Focus. 2007;22:1–11
53. Golan JD, Martens F, Griebel J, LoPresti DC, Hess MG, Ahrens M. Long-term outcomes following lumbar nucleus replacement Int J Spine Surg. 2021;15:1096–102
54. Zweig T, Aghayev E, Melloh M, Dietrich D, Röder CSWISSspine Registry Group. . Influence of preoperative leg pain and radiculopathy on outcomes in mono-segmental lumbar total disc replacement: Results from a nationwide registry Eur Spine J. 2012;21:729–36
55. Bertagnoli R, Yue JJ, Shah RV, Nanieva R, Pfeiffer F, Fenk-Mayer A, et al The treatment of disabling multilevel lumbar discogenic low back pain with total disc arthroplasty utilizing the prodisc prosthesis: A prospective study with 2-year minimum follow-up Spine. 2005;30:2192–9
56. Cui XD, Li HT, Zhang W, Zhang LL, Luo ZP, Yang HL. Mid- to long-term results of total disc replacement for lumbar degenerative disc disease: A systematic review J Orthop Surg. 2018;13:326
57. Phillips FM, Garfin SR. Cervical disc replacement Spine. 2005;30:S27–33
58. Shin JJ, Kim KR, Son DW, Shin DA, Yi S, Kim KN, et al Cervical disc arthroplasty: What we know in 2020 and a literature review J Orthop Surg. 2021;29:230949902110069
59. Radcliff K, Davis RJ, Hisey MS, Nunley PD, Hoffman GA, Jackson RJ, et al Long-term evaluation of cervical disc arthroplasty with the Mobi-C© cervical disc: A randomized, prospective, multicenter clinical trial with seven-year follow-up Int J Spine Surg. 2017;11:31
60. Auerbach JD, Jones KJ, Fras CI, Balderston JR, Rushton SA, Chin KR. The prevalence of indications and contraindications to cervical total disc replacement Spine J. 2008;8:711–6
61. Fiani B, Nanney JM, Villait A, Sekhon M, Doan T. Investigational research: Timeline, trials, and future directions of spinal disc arthroplasty Cureus. 2021;13:e16739
62. Peng Z, Hong Y, Meng Y, Liu H. A meta-analysis comparing the short- and mid- to long-term outcomes of artificial cervical disc replacement (ACDR) with anterior cervical discectomy and fusion (ACDF) for the treatment of cervical degenerative disc disease Int Orthop. 2022;46:1609–25
63. Wang Q, Tu Z, Hu P, Kontos F, Li Y, Li L, et al Long-term results comparing cervical disc arthroplasty to anterior cervical discectomy and fusion: A systematic review and meta-analysis of randomized controlled trials Orthop Surg. 2020;12:16–30
64. Gao Y, Liu M, Li T, Huang F, Tang T, Xiang Z. A meta-analysis comparing the results of cervical disc arthroplasty with anterior cervical discectomy and fusion (ACDF) for the treatment of symptomatic cervical disc disease J Bone Jt Surg. 2013;95:555–61
65. Luo J, Gong M, Huang S, Yu T, Zou X. Incidence of
adjacent segment degeneration in cervical disc arthroplasty versus anterior cervical decompression and fusion meta-analysis of prospective studies Arch Orthop Trauma Surg. 2015;135:155–60
66. Rao MJ, Nie SP, Xiao BW, Zhang GH, Gan XR, Cao SS. Cervical disc arthroplasty versus anterior cervical discectomy and fusion for treatment of symptomatic cervical disc disease: a meta-analysis of randomized controlled trials Arch Orthop Trauma Surg. 2015;135:19–28
67. Findlay C, Ayis S, Demetriades AK. Total disc replacement versus anterior cervical discectomy and fusion: a systematic review with meta-analysis of data from a total of 3160 patients across 14 randomized controlled trials with both short- and medium- to long-term outcomes Bone Jt J. 2018;100-B:991–1001
68. Ray CD. The PDN® prosthetic disc-nucleus device Eur Spine J. 2002;11:S137–42
69. Serhan H, Mhatre D, Defossez H, Bono CM. Motion-preserving technologies for degenerative lumbar spine: The past, present, and future horizons SAS J. 2011;5:75–89
70. Bertagnoli R, Schönmayr R. Surgical and clinical results with the PDN® prosthetic disc-nucleus device Eur Spine J. 2002;11:S143–8
71. Jin D, Qu D, Zhao L, Chen J, Jiang J. Prosthetic Disc Nucleus (PDN) Replacement for Lumbar Disc Herniation: Preliminary Report with Six Months’ Follow-Up J Spinal Disord Tech. 2003;16:331–7
72. Sengupta D. Dynamic stabilization devices in the treatment of low back pain Neurol India. 2005;53:466
73. Bono CM, Kadaba M, Vaccaro AR. Posterior pedicle fixation-based dynamic stabilization devices for the treatment of degenerative diseases of the lumbar spine J Spinal Disord Tech. 2009;22:376–83
74. Yu SW, Yen CY, Wu CH, Kao FC, Kao YH, Tu YK. Radiographic and clinical results of posterior dynamic stabilization for the treatment of multisegment degenerative disc disease with a minimum follow-up of 3 years Arch Orthop Trauma Surg. 2012;132:583–9
75. Schwarzenbach O, Berlemann U, Stoll TM, Dubois G. Posterior dynamic stabilization systems: DYNESYS Orthop Clin North Am. 2005;36:363–72
76. Prud’homme M, Barrios C, Rouch P, Charles YP, Steib JP, Skalli W. Clinical outcomes and complications after pedicle-anchored dynamic or hybrid lumbar spine stabilization: a systematic literature review J Spinal Disord Tech. 2015;28:E439–48
77. Greiner-Perth R, Sellhast N, Perler G, Dietrich D, Staub LP, Röder C. Dynamic posterior stabilization for degenerative lumbar spine disease: a large consecutive case series with long-term follow-up by additional postal survey Eur Spine J. 2016;25:2563–70
78. Lo TP, Salerno SS, Colohan ART. Interlaminar spacer: A review of its mechanism, application, and efficacy World Neurosurg. 2010;74:617–26
79. Tram J, Srinivas S, Wali AR, Lewis CS, Pham MH. Decompression Surgery versus Interspinous Devices for Lumbar Spinal Stenosis: A Systematic Review of the Literature Asian Spine J. 2020;14:526–42
80. Wu AM, Zhou Y, Li QL, Wu XL, Jin YL, Luo P, et al Interspinous spacer versus traditional decompressive surgery for lumbar spinal stenosis: a systematic review and meta-analysis PLoS One. 2014;9:e97142
81. Li M, Yang H, Wang G. Interspinous process devices for the treatment of neurogenic intermittent claudication: a systematic review of randomized controlled trials Neurosurg Rev. 2017;40:529–36
82. Gu BJ, Blue R, Yoon J, Welch WC. Posterior lumbar facet replacement and arthroplasty Neurosurg Clin N Am. 2021;32:521–6
83. Bono CM, Ghiselli G, Gilbert TJ, Kreiner DS, Reitman C, Summers JT, et al North American spine society. An evidence-based clinical guideline for the diagnosis and treatment of cervical radiculopathy from degenerative disorders Spine J. 2011;11:64–72
84. Bono CM, Ghiselli G, Gilbert TJ, Kreiner DS, Reitman C, Summers JT, et al North American spine society. An evidence-based clinical guideline for the diagnosis and treatment of cervical radiculopathy from degenerative disorders Spine J. 2011;11:64–72
85. Kreiner DS, Hwang SW, Easa JE, Resnick DK, Baisden JL, Bess S, et al North American spine society. An evidence-based clinical guideline for the diagnosis and treatment of lumbar disc herniation with radiculopathy Spine J. 2014;14:180–91
86. Chou R, Loeser JD, Owens DK, Rosenquist RW, Atlas SJ, Baisden J, et al Interventional therapies, surgery, and interdisciplinary rehabilitation for low back pain: an evidence-based clinical practice guideline from the American Pain Society Spine. 2009;34:1066–77
87. Chou R, Baisden J, Carragee EJ, Resnick DK, Shaffer WO, Loeser JD. Surgery for low back pain: a review of the evidence for an American Pain Society Clinical Practice Guideline Spine. 2009;34:1094–109
88. Guyer R, Musacchio M, Cammisa FP, Lorio MP. ISASS recommendations/coverage criteria for decompression with interlaminar stabilization - Coverage indications, limitations, and/or medical necessity Int J Spine Surg. 2016;10:41
89. Watters WC 3rd, Bono CM, Gilbert TJ, Kreiner DS, Mazanec DJ, Shaffer WO, et al North American spine society. An evidence-based clinical guideline for the diagnosis and treatment of degenerative lumbar spondylolisthesis Spine J. 2009;9:609–14
90. Kreiner DS, Shaffer WO, Baisden JL, Gilbert TJ, Summers JT, Toton JF, et al North American spine society. An evidence-based clinical guideline for the diagnosis and treatment of degenerative lumbar spinal stenosis (update) Spine J. 2013;13:734–43
