Biomechanical comparison of different interspinous process devices in the treatment of lumbar spinal stenosis: a finite element analysis

Background

Lumbar spinal stenosis (LSS) is a common disease among elderly individuals, and surgery is an effective treatment. The development of minimally invasive surgical techniques, such as the lumbar interspinous process device (IPD), has provided patients with more surgical options.

Objective

To investigate the biomechanical properties of different IPDs, including BacFuse, X-Stop and Coflex, in the treatment of LSS.

Methods

Based on the computed tomography images of a patient with LSS, four finite element (FE) models of L3-S5 were created in this study. The FE models included a surgical model of the intact lumbar spine and surgical models of the lumbar IPDs BacFuse, X-Stop, and Coflex. After validating the models, they were simulated for four physiological motions: flexion, extension, lateral bending and axial rotation, and range of motion (ROM). Stress distribution of discs and facet joints in each segment, stress distribution of the spinous process in the operated section, and stress distribution of the internal fixation were compared and analysed.

Results

Compared to the model of the intact lumbar spine, the other three models showed a decrease in ROM and disc and facet joint stresses in the surgical segment during movement and an increase in ROM and disc and facet joint stresses in the adjacent segments. These effects were greater for the proximal adjacent segment with BacFuse and more pronounced for the distal adjacent segment with Coflex, while X-Stop had the greatest stress effect on the spinous process in the surgical segment.

Conclusion

BacFuse, Coflex and X-Stop could all be implemented to effectively reduce extension and disc and facet joint stresses, but they also increase the ROM and disc and facet joint stresses in adjacent segments, which may cause degeneration.

Biomechanics and Mechanism of Action of Indirect Lumbar Decompression and the Evolution of a Stand-alone Spinous Process Spacer

Objective

Objective Interspinous process spacers are used in the treatment of lumbar spinal stenosis by preventing extension at the implanted level and reducing claudication, which is a common symptom of lumbar spinal stenosis. This review assessed the current safety and performance of lumbar spinal stenosis treatments and the biomechanical effects of spinal position, range of motion, and the use of interspinous process spacers.

Method

Method EMBASE and PubMed were searched to find studies reporting on the safety and performance of nonsurgical treatment, including physical therapy and pharmacological treatment, and surgical treatment, including direct and indirect lumbar decompression treatment. Results were supplemented with manual searches to include studies reporting on the use of interspinous process spacers and the review of biomechanical testing performed on the Superion device.

Results

Results The effects of spinal position in extension and flexion have been shown to have an impact in the variation in dimensions of the spinal canal and foramina areas. Overall studies have shown that spinal positions from flexion to extension reduce the spinal canal and foramina dimensions and increase ligamentum flavum thickness. Biomechanical test data have shown that the Superion device resists extension and reduces angular movement at the implantation level and provides significant segmental stability.

Conclusions

Conclusions Superion interspinous lumbar decompression is a minimally invasive, low-risk procedure for the treatment of lumbar spinal stenosis, which has been shown to have a low safety profile by maintaining sagittal alignment, limiting the potential for device dislodgment or migration, and to preserve mobility and structural elements.

Interspinous implants: are the new implants better than the last generation? A review

PURPOSE OF REVIEW

Interspinous process devices (IPDs) are used in the surgical treatment of lumbar spinal stenosis. The purpose of this review is to compare the first generation with the next-generation devices in terms of complications, device failure, reoperation rates, symptom relief, and outcome.

RECENT FINDINGS

Thirty-seven studies were included from 2011 to 2016. Device failure occurred at a mean of 3.7%, with a lower tendency to happen with next-generation IPDs. Reoperations occurred at a lower rate with the next-generation devices, with a mean follow up of 24 months (3.7% vs. 11.1%). The clinical outcome is not influenced by the type of IPD. The long-term functionality of these devices is questionable, with radiologic changes and recurrence of symptoms often seen by 2 years following implantation. Next-generation devices do not appear to be subject to the same "bounce back" effect of symptom re-emergence after several years.

Lumbar lateral shift in a patient with interspinous device implantation: a case report

BACKGROUND

Lumbar lateral shift (LLS) is a common clinical observation but has rarely been described in a patient with a history of lumbar surgery. The purpose of the current case report was to describe the use of the McKenzie Method of Mechanical Diagnosis and Therapy (MDT) in the multi-modal treatment of a patient with an LLS and a history of multiple surgical procedures in the lumbar spine, including interspinous process device (IPD) implantation.

CASE DESCRIPTION

A 72-year-old female with chronic low back pain (LBP) and a surgical history in the lumbar spine was referred to physical therapy for radiating leg pain and presented with a right LLS. Her chief complaints included sitting for long periods, vacuuming and ascending stairs into her home.

OUTCOMES

The patient was treated during eight visits over 30 days. Treatment interventions included manual shift correction, self-correction and management, joint mobilisation below the level of IPD implantation ,neurophysiology education, and development of a home exercise programme. At discharge, her leg pain was resolved and all goals had been met. The patient reported maintenance of gains at 6-month follow-up.

DISCUSSION

Utilisation of the MDT approach, including LLS correction, produced positive outcomes in a complex patient with previous IPD implantation. Future research should investigate treatment and outcomes after invasive spinal procedures in similar patient populations to better inform clinical management.

LEVEL OF EVIDENCE

4.

Analysis of Internet information on the controversial X-Stop device

BACKGROUND CONTEXT

The Internet is frequently used by patients to aid in medical decision making. Multiple studies display the Internet's ineffectiveness in presenting high-quality information regarding surgical procedures and devices. With recent reports of unacceptably high complication rates and poor outcomes with the X-Stop device, it is important that online information is comprehensive and accurate. This study is the first to examine Internet information on the controversial X-Stop.

PURPOSE

To determine how accurately public information over the Internet portrays the existing primary literature on the X-Stop, how extensively the X-Stop is characterized online, and how patient decision making could foreseeably be affected.

STUDY DESIGN

This cross-sectional study analyzed publicly available Internet information, including videos on the web site YouTube regarding the X-Stop device.

PATIENT SAMPLE

No patients were involved in this study.

OUTCOME MEASURES

No specific outcome measures were used.

METHODS

Search engines Google, Yahoo, and Bing were used to identify 105 web sites providing information on the X-Stop. Videos on the web site YouTube were included. Web sites were categorized based on the authorship. Each site was analyzed for the provision of appropriate patient inclusion and exclusion criteria, surgical and nonsurgical treatment alternatives, purported benefits, common complications, peer-reviewed literature citations, and descriptions/diagrams of the procedure. Data were evaluated for each authorship subgroup and the entire group of sites.

RESULTS

Forty-three percent of sites were authored by a private medical group, 4% by an academic medical group, 16% by an insurance company, 9% by a biomedical industry, 10% by news sources, and 19% by other. Thirty-one percent of web sites and 11% of sites authored by private medical groups contained references to peer-reviewed literature. Fifty-six percent of web sites reported patient inclusion criteria, whereas 33% reported exclusion criteria. Benefits and complications were reported within 91% and 23% of sites, respectively. Surgical and nonsurgical treatment options were mentioned within 59% and 61% of web sites, respectively.

CONCLUSIONS

Our study demonstrates the Internet's ineffectiveness in reporting quality information on the X-Stop. Information was often incomplete and potentially misleading. Significant controversy exists within primary literature regarding the safety and efficacy of the X-Stop. Yet, publicly available Internet information largely provided misinformation and did not reflect any such controversy. This raises the concern that such information lends itself more toward patient recruitment than patient education. Medical professionals need to know how this may affect their patients' decision making.