Peer-Review ReportBiomechanical Analysis of Disc Pressure and Facet Contact Force After Simulated Two-Level Cervical Surgeries (Fusion and Arthroplasty) and Hybrid Surgery
Introduction
Adjacent-segment degeneration (ASD) is a long-term complication of cervical fusion procedures that requires additional surgical intervention with time 8, 9. Great effort has been devoted to preventing this type of progressive deterioration, including the development of artificial cervical discs and the introduction of hybrid surgical techniques involving single-level treatments (anterior cervical discectomy and fusion [ACDF] plus arthroplasty) as opposed to 2-level ACDF. A number of biomechanical studies, including our preliminary reports (2, 3, 4), also have documented the changes that range of motion (ROM) spinal movements exact at the adjacent vertebral level after spinal fusion, hybrid surgery, or cervical arthroplasty. Unfortunately, these investigations do not fully explain the degenerative disc changes that ensue.
According to recent speculation, altered spinal biomechanics may create pressure changes within adjacent discs after surgery. Although Nachemson (13) was first to use intradiscal pressure (IDP) for estimating in vivo load, others have examined the effects of spinal fusion on IDP in various postures 5, 6, and some have suggested that assessing the load transmitted by facet joints (facet contact force [FCF]) is another critical component in biomechanical evaluation of the spine 11, 15.
We subsequently sought to stratify adjacent-level IDP and FCF in vivo according to type of surgery performed: 2-level cervical fusion, 2-level disc arthroplasty, or single-level hybrids thereof. Using cadaveric simulations of these procedures, we sought to gauge the potential for later development of ASD.
Section snippets
In Vitro Cadaveric Testing
Twenty-four cadaveric human cervical spines (C3-T2) were selected for study, excluding those with bony deformity by fluoroscopic radiographs (anteroposterior and lateral views) and low bone mineral density by dual-energy X-ray absorptiometry scan (Discovery QDR Series; Hologic, Inc, Bedford, Massachusetts, USA), equating osteoporosis with a T score < −2.5. The specimens were thawed overnight at room temperature and were meticulously stripped of muscles, with careful preservation of spinal
Results
All cadaveric specimens selected were free of osteoporosis (T score >2.5 by dual-energy X-ray absorptiometry scan), corresponding with a bone mineral density of 0.56–0.83 g/cm2. There were no instrument-related fractures during placement of cervical screws and artificial disc prosthetics.
Discussion
Compared with ACDF, a number of authors have reported that cervical disc replacement is more likely to maintain physiologic segmental motion after implantation and therefore improve clinical outcomes 7, 10, 12, 14, 18. However, others have insisted that single-level hybrid (ACDF/arthroplasty) procedures and single-level arthroplasty may be reasonable alternative treatments because 2-level arthroplasty may allow excessive motion at treated levels 16, 19. We previously reported that full C4−T1
Conclusions
The present study demonstrates that adjacent-level IDP and FCF in vivo differ, depending upon the nature of spinal surgery performed (2-level fusion, 2-level arthroplasty, or hybrid surgery). On the basis of our simulations, IDP increased at the anterior annulus of distal adjacent-level disc during flexion and axial rotation and at the center of proximal adjacent-level disc during flexion following 2-level cervical arthrodesis. It was also evident that cervical fusion surgeries tend to
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2023, Journal of Clinical NeuroscienceBiomechanical effects of uncinate process excision in cervical disc Arthroplasty
2021, Clinical BiomechanicsCitation Excerpt :These findings suggest that the uncinate process has nonuniform but lower (less than 10%) effect on the anterior column loads at the adjacent segments (two exceptions). This phenomenon of decreased motion and pressure is also observed in other studies, while the significance of the decrease was not consistent, and as stated earlier, experimental design and artificial disc design differences are considered as plausible factors (Chang et al., 2007; Dmitriev et al., 2005; Park et al., 2014; Volkheimer et al., 2015; Welke et al., 2016). The excision of the uncinate process decreased the facet loads for the Bryan disc and increased for the Mobi-C disc under extension and lateral bending, while it increased under extension and decreased under lateral bending for the Prestige LP disc.
Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.