Implant Preservation versus Implant Replacement in Revision Surgery for Adjacent Segment Disease After Thoracolumbar Instrumentation: A Retrospective Study of 43 Patients

Comparative study of percutaneous endoscopic lumbar decompression and traditional revision surgery in the treatment of symptomatic adjacent segment degeneration

OBJECTIVE

The objective of this study is to evaluate and compare the surgical outcomes and complications of Percutaneous Endoscopic Lumbar Decompression (PELD) and traditional revision surgery in treating symptomatic Adjacent Segment Degeneration (ASD). This comparison aims to delineate the advantages and disadvantages of these methods, assisting spine surgeons in making informed surgical decisions.

METHODS

66 patients with symptomatic ASD who failed conservative treatment for more than 1 month and received repeated lumbar surgery were retrospectively collected in the study from January 2015 to November 2018, with the average age of 65.86 ± 11.04 years old. According to the type of surgery they received, all the patients were divided in 2 groups, including 32 patients replaced the prior rod in Group A and 34 patients received PELD at the adjacent level in Group B. Patients were followed up routinely and received clinical and radiological evaluation at 3, 6, 12 months and yearly postoperatively. Complications and hospital costs were recorded through chart reviews.

RESULTS

The majority of patients experienced positive surgical outcomes. However, three cases encountered complications. Notably, Group B patients demonstrated superior pain relief and improved postoperative functional scores throughout the follow-up period, alongside reduced hospital costs (P < 0.05). Additionally, significant reductions in average operative time, blood loss, and hospital stay were observed in Group B (P < 0.05). Notwithstanding these benefits, three patients in Group B experienced disc re-herniation and underwent subsequent revision surgeries.

CONCLUSIONS

While PELD offers several advantages over traditional revision surgery, such as reduced operative time, blood loss, and hospital stay, it also presents a higher likelihood of requiring subsequent revision surgeries. Future studies involving a larger cohort and extended follow-up periods are essential to fully assess the relative benefits and drawbacks of these surgical approaches for ASD.

Revision Extension of Fusion Surgery in Thoracolumbar Spine Using a Newly Designed Revision Rod - Comparative Matched Cohort Study Versus Implant-Replacement Surgery

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To compare the results of revision extension of fusion surgery using the newly designed revision rod and implant-replacement surgery in thoracolumbar spine.

METHODS

Thirty-one patients who underwent extension of fusion surgery using the revision rod for adjacent segment disease were included in this study. Thirty-one patients who underwent implant-replacement revision surgery were selected as a control group by matching age, sex, preoperative diagnosis, and number of revision segments.

RESULTS

The mean age was 70.7 ± 8.0 years in the revision rod (RR) group and 69.0 ± 8.4 years in the control group. Preoperative diagnoses, underlying diseases, and mean number of revision segments (2.2 ± 1.1) were similar in both groups. The change of hemoglobin (1.0 ± 1.9 vs 2.5 ± 1.5 g/dl; P < .01), hematocrit (4.1 ± 4.9 vs 7.2 ± 4.4 % P < .01) and albumin (.8 ± .9 vs 1.3 ± .4 g/dl; P < .01) levels before and after surgery showed significant differences between the two groups. Hemovac drainage was significantly less in the RR group (P = .01). The mean operative time was shorter in the RR group (203.5 ± 9.5 min vs 233.5 ± 8.7 min; P = .12) with no statistical difference. Radiological results showed that the average lumbar lordosis 2 years after surgery was lower in the RR group compared to the control group (25.1 ± 9.9° vs 32.9 ± 9.8°; P = .02). Union rates and clinical outcomes were not different between the two groups.

CONCLUSIONS

Revision extension of fusion surgery using a newly designed revision rod had less hemovac drainage and superior laboratory findings compared to implant-replacement revision surgery.

Risk factors for mechanical complications after fusion extension surgery for lumbar adjacent segment disease

PURPOSE

Adjacent segment disease (ASD) is a common complication in fusion surgery. In the event of solid segmental fusion, previous implants can be removed or preserved during fusion extension for ASD. To compare the surgical outcomes of patients with and without implants and analyzes the risk factors for postoperative mechanical complications.

METHODS

Patients who underwent fusion extension for lumbar ASD from 2011 to 2019 with a minimum 2 year follow-up were retrospectively reviewed. Spinopelvic parameters were measured preoperatively and postoperatively. Clinical outcomes and surgical complications were compared between groups with implants preserved and removed. Risk factors for mechanical complications, including clinical, surgical, and radiographic factors were analyzed.

RESULTS

Sixty-nine patients (mean age, 69.9 ± 6.9 years) were included. The mean numbers of initial and extended fused segments were 2.8 ± 0.7 and 2.7 ± 0.7, respectively. Previous implants were removed in 43 patients (R group) and preserved in 26 patients (P group). Both groups showed an improvement in clinical outcomes without between-group differences. The operation time was significantly longer in R group (260 vs 207 min, p < 0.001). Mechanical complications occurred in 13 patients (12 in R group and 1 in P group) and reoperation was needed in 3 patients (R group). Implant removal, index fusion surgery including L5-S1, and postoperative sagittal malalignment were risk factors for mechanical complications.

CONCLUSION

Implant removal was a risk factor for mechanical complications. Index fusion surgery including L5-S1 and postoperative sagittal malalignment were also risk factors for mechanical complications.

Biomechanical comparison of different rod-to-rod connectors to a conventional titanium- and cobalt chromium posterior spinal fixation system

Introduction

Several types of rod-to-rod connectors are available for the extension of spinal fixation systems. However, scientific literature regarding the mechanical performance of different rod-to-rod connector systems is lacking.

Research question

The goal of this study was to evaluate the mechanical characteristics of axial and lateral rod connectors in comparison to a conventional pedicle screw rod (titanium and cobalt chromium) construct.

Material and method

Six types of instrumentations were investigated in a standardized test model to quantify the mechanical differences: 1: titanium rod; 2: titanium rod with axial connector; 3: titanium rod with lateral connector; 4: cobalt chromium rod; 5: cobalt chromium rod with axial connector; 6: cobalt chromium rod with lateral connector. All groups were tested in static compression, static torsion and dynamic compression and statistically compared regarding failure load and stiffness.

Results

In static compression loading, the use of connectors increased the construct stiffness, but unaffected the yield load. The use of a cobalt chromium rod significantly increased by approximately 40% the yield load and stiffness in comparison to the titanium rod configurations. Under dynamic compression, a similar or higher fatigue strength for all tested groups in comparison to the titanium rod configuration was evaluated, with the exception of titanium rod with axial connector.

Conclusion

Biomechanically, using rod connectors is a secure way for the extension of a construct and is mechanically equal to a conventional screw rod construct. However, in clinical use, attention should be paid regarding placement of the connectors at high loaded areas.

How I do it: biportal endoscopic spinal surgery for revision of adjacent segment disease after instrumented lumbar fusion

BACKGROUND

Lumbar fusion with rigid fixation can be complicated by adjacent segment degeneration, which may cause neurological deficits and back pain, and occasionally necessitates revision surgery. This type of revision surgery is difficult to perform in a minimally invasive manner because it requires the revision of the original internal fixation instruments.

METHOD

We describe a biportal endoscopic spinal surgery (BESS) procedure for revision surgery due to adjacent segment disease after lumbar fusion with rigid fixation instruments. The radiological images and complete surgical procedure are presented.

CONCLUSIONS

BESS effectively enabled nerve decompression, intervertebral fusion, and revision of lumbar fusion with fixation instruments in a minimally invasive manner.

Effects of Revision Rod Position on Spinal Construct Stability in Lumbar Revision Surgery: A Finite Element Study

Revision surgery (RS) is a necessary surgical intervention in clinical practice to treat spinal instrumentation–related symptomatic complications. Three constructs with different configurations have been applied in RS. One distinguishing characteristic of these configurations is that the revision rods connecting previous segments and revision segments are placed alongside, outside, or inside the previous rods at the level of facetectomy. Whether the position of the revision rod could generate mechanical disparities in revision constructs is unknown. The objective of this study was to assess the influence of the revision rod position on the construct after RS. A validated spinal finite element (FE) model was developed to simulate RS after previous instrumented fusion using a modified dual-rod construct (DRCm), satellite-rod construct (SRC), and cortical bone trajectory construct (CBTC). Thereafter, maximum von Mises stress (VMS) on the annulus fibrosus and cages and the ligament force of the interspinous ligament, supraspinous ligament, and ligamentum flavum under a pure moment load and a follower load in six directions were applied to assess the influence of the revision rod position on the revision construct. An approximately identical overall reducing tendency of VMS was observed among the three constructs. The changing tendency of the maximum VMS on the cages placed at L4-L5 was nearly equal among the three constructs. However, the changing tendency of the maximum VMS on the cage placed at L2-L3 was notable, especially in the CBTC under right bending and left axial rotation. The overall changing tendency of the ligament force in the DRCm, SRC, and CBTC was also approximately equal, while the ligament force of the CBTC was found to be significantly greater than that of the DRCm and SRC at L1-L2. The results indicated that the stiffness associated with the CBTC might be lower than that associated with the DRCm and SRC in RS. The results of the present study indicated that the DRCm, SRC, and CBTC could provide sufficient stabilization in RS. The CBTC was a less rigid construct. Rather than the revision rod position, the method of constructing spinal instrumentation played a role in influencing the biomechanics of revision.