The Efficacy of Lumbar Hybrid Fusion for the Prevention of Adjacent Segment Disease: Fact or Artifact? A Meta-analysis

Effectiveness of Interspinous Process Devices in Managing Adjacent Segment Degeneration Following Lumbar Spinal Fusion: A Systematic Review and Meta-Analysis

Background: Adjacent segment degeneration (ASD) is a significant complication following lumbar spinal fusion, often necessitating further surgical interventions and impairing patient outcomes. Interspinous process devices were introduced as an alternative treatment for spinal stenosis and degenerative spondylolisthesis and can potentially reduce the incidence of ASDd. This systematic review and meta-analysis aims to evaluate the effectiveness of interspinous process devices or IPDs in managing ASD following a previous spinal fusion compared to traditional fusion techniques. Methods: Electronic databases, including PubMed, Embase, and the Cochrane Library, were queried for studies assessing IPDs against traditional lumbar fusion methods for managing ASD after previous lumbar fusion, which had been published between January 2014 and the present. Statistical analysis was conducted using Review Manager 5.4. Results: Seven retrospective cohort studies involving 546 patients met the inclusion criteria. The analysis revealed that IPDs were associated with a statistically significant reduction in the incidence of ASD (OR = 0.28, 95% CI: 0.16 to 0.51, p < 0.0001, and I2 = 0% after excluding outliers). The ODI demonstrated a non-significant trend towards improved outcomes with IPDs at the 2-year follow-up (SMD = -3.94; 95% CI: -11.72 to 3.85). Range of motion (ROM) was better preserved with IPDs compared to fusion (SMD = 0.00, 95% CI: -0.41 to 0.41, p = 1.00, I2 = 60%). The visual analogue scale or VAS lower back pain scores were significantly reduced at the 2-year follow-up (SMD = -0.69, 95% CI: -1.18 to -0.19, p = 0.006, and I2 = 74%). VAS leg pain showed consistent improvements (SMD = -0.29; 95% CI: -0.63 to 0.04). Intraoperative blood loss was significantly lower with IPDs (SMD = -2.07; 95% CI: -3.27 to -0.87, p = 0.0007, and I2 = 95%), and operation times were shorter (SMD = -2.22, 95% CI: -3.31 to -1.12, p < 0.0001, and I2 = 94%). Conclusions: The judicious use of IPDs might benefit a subset of patients, particularly those who are not suitable candidates for major corrective surgery.

Biomechanical Effects of Different Prosthesis Types and Fixation Ranges in Multisegmental Total En Bloc Spondylectomy: A Finite Element Study

OBJECTIVE

Multi-segmental total en bloc spondylectomy (TES) gradually became more commonly used by clinicians. However, the choice of surgical strategy is unclear. This study aims to investigate the biomechanical performance of different prosthesis types and fixation ranges in multisegmental TES.

METHODS

In this study, a validated finite element model of T12-L2 post-spondylectomy operations were carried out. The prostheses of these models used either 3D-printed artificial vertebrae or titanium mesh cages. The fixed range was two or three segment levels. Range of motion, stress distribution of the endplate and internal fixation system, intervertebral disc pressure, and facet joint surface force of four postoperative models and intact model in flexion and extension, as well as lateral bending and rotation were analyzed and compared.

RESULTS

The type of prosthesis used in the anterior column reconstruction mainly affected the stress of the adjacent endplate and the prosthesis itself. The posterior fixation range had a greater influence on the overall range of motion (ROM), the ROM of the adjacent segment, the stress of the screw-rod system, and adjacent facet joint surface force. For the model of the same prosthesis, the increase of fixed length resulted in an obvious reduction of ROM. The maximal decrease was 70.23% during extension, and the minimal decrease was 30.19% during rotation.

CONCLUSION

In three-segment TES, the surgical strategy of using 3D-printed artificial prosthesis for anterior column support and pedicle screws for posterior fixation at both two upper and lower levels respectively can reduce the stress on internal fixation system, endplates, and adjacent intervertebral discs, resulting in a reduced risk of internal fixation failure, and ASD development.

Biomechanical comparison of spinal column shortening - a finite element study

BACKGROUND

At present, research on spinal shortening is mainly focused on the safe distance of spinal shortening and the mechanism of spinal cord injury, but there is no research on the biomechanical characteristics of different shortening distances. The purpose of this study was to study the biomechanical characteristics of spine and internal fixation instruments at different shortening distances by the finite element (FE) method.

METHODS

An FE model of lumbar L1-S was established and referred to the previous in vitro experiments to verify the rationality of the model by verifying the Intradiscal pressure (IDP) and the range of motion (ROM) of the motion segment. Five element models of spinal shortening were designed under the safe distance of spinal shortening, and the entire L3 vertebra and both the upper and lower intervertebral discs were resected. Model A was not shortened, while models B-E were shortened by 10%, 20%, 30% and 50% of the vertebral body, respectively. Constraining the ROM of the sacrum in all directions, a 7.5 N ·m moment and 280 N follower load were applied on the L1 vertebra to simulate the motion of the lumbar vertebrae in three planes. The ROM of the operated segments, the Von Mises stress (VMS) of the screw-rod system, the VMS of the upper endplate at the interface between the titanium cage and the L4 vertebral body, and the ROM and the IDP of the adjacent segment (L5/S) were recorded and analysed.

RESULTS

All surgical models showed good stability at the operated segments (L1-5), with the greatest constraint in posterior extension (99.3-99.7%), followed by left-right bending (97.9-98.7%), and the least constraint in left-right rotation (84.9-86.3%) compared with the intact model. The VMS of the screw-rod system and the ROM and IDP of the distal adjacent segments of models A-E showed an increasing trend, in which the VMS of the screw-rod system of model E was the highest under flexion (172.5 MPa). The VMS of the endplate at the interface between the cage and L4 upper endplate of models A-E decreased gradually, and these trend were the most obvious in flexion, which were 3.03, 2.95, 2.83, 2.78, and 2.61 times that of the intact model, respectively.

CONCLUSION

When performing total vertebrae resection and correcting the spinal deformity, if the corrected spine has met our needs, the distance of spinal shortening should be minimized to prevent spinal cord injury, fracture of internal fixations and adjacent segment disease (ASD).

Comparison of long-term outcomes of spinal fusion surgeries supplemented with "topping-off" implants in lumbar degenerative diseases: A systematic review and network meta-analysis

Background Context

Spinal fusion surgery is a common treatment for lumbar degenerative diseases and has been associated with the long-term complication of adjacent segment disease (ASD). In recent years, the "topping-off" technique has emerged as a new surgical method, combining spinal fusion with a hybrid stabilization device (HSD) or interspinous process device (IPD) proximal to the fused vertebrae.

Methods

A literature search using the PubMed, Cochrane Central Register of Controlled Trials, EMBASE, and Web of Science databases identified eligible studies comparing topping-off implant(s) with spinal fusion surgery for lumbar degenerative diseases. Risk of bias was assessed using the Cochrane RoB 2.0 tool for randomized controlled trials and the Newcastle-Ottawa scale for retrospective studies. Each outcome was analyzed using the statistical Confidence in NMA (CINeMA) 1.9.0 software.

Results

17 RCTs and retrospective studies that included 1255 participants and five interventions were identified. The topping-off implants device for intervertebral assisted motion (DIAM; OR = 0.235, p < 0.001), Dynesys (OR = 0.413, p < 0.001), and Coflex (OR = 0.417, p < 0.01) significantly lowered the incidence of radiographic adjacent segment degeneration (RASDeg) compared with spinal fusion surgery alone. Spinal fusion supplemented with DIAM significantly reduced the incidence of clinical adjacent segment disease (CASD) (OR = 0.358, p = 0.032).

Conclusions

Spinal fusion supplemented with DIAM substantially reduced the incidence of radiographic and clinical adjacent segment disease. No significant difference was observed between the treatment comparators for reoperation due to ASD and back pain relief score.

Application of dual-trajectory screws in revision surgery for lumbar adjacent segment disease: a finite element study

BACKGROUND

Advancements in medicine and the popularity of lumbar fusion surgery have made lumbar adjacent segment disease (ASDz) increasingly common, but there is no mature plan for guiding its surgical treatment. Therefore, in this study, four different finite element (FE) ASDz models were designed and their biomechanical characteristics were analysed to provide a theoretical basis for clinical workers to choose the most appropriate revision scheme for ASDz.

METHODS

According to whether internal fixation was retained, different FE models were created to simulate ASDz revision surgery, and flexion, extension, axial rotation and lateral bending were simulated by loading. The biomechanical characteristics of the adjacent segments of the intervertebral disc and the internal fixation system and the range of motion (ROM) of the lumbar vertebrae were analysed.

RESULTS

The difference in the ROM of the fixed segment between FE models that did or did not retain the original internal fixation was less than 0.1°, and the difference was not significant. However, the stress of the screw-rod system when the original internal fixation was retained and prolonged fixation was performed with dual-trajectory screws was less than that when the original internal fixation was removed and prolonged fixation was performed with a long bar. Especially in axial rotation, the difference between models A and B is the largest, and the difference in peak stress reached 30 MPa. However, for the ASDz revision surgery segment, the endplate stress between the two models was the lowest, and the intradiscal pressure (IDP) of the adjacent segment was not significantly different between different models.

CONCLUSION

Although ASDz revision surgery by retaining the original internal fixation and prolonging fixation with dual-trajectory screws led to an increase in stress in the fusion segment endplate, it provides stability similar to ASDz revision surgery by removing the original internal fixation and prolonging fixation with a long bar and does not lead to a significant change in the IDP of the adjacent segment while avoiding a greater risk of rod fracture.