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

Abstract

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 nextgeneration 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. Summary 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.

Axial loading during MRI reveals insufficient effect of percutaneous interspinous implants (Aperius™ PerCLID™) on spinal canal area

“…Likely also postoperatively, alMRI provides a more realistic image of the spine morphology during spinal loading, compared to conventional MRI. Hence, the insufficient radiological effects of the IPD in the current study provide a reasonable patho-anatomical explanation to reported clinical treatment failure and high reoperation rates [8][9][10][11].…”

“…Contrarily, the ODS group displayed a DSCSA increase in changing from an absolute stenosis preoperatively to close to what is considered normal DSCSA postoperatively ( Table 2). The failure of the IPD to show radiological improvement postoperatively in alMRI might, at least to some extent, explain the general lack of long-term functionality and high reported reoperation rates among LSS patients treated with IPD [8][9][10][11]23].…”

“…The reason why postoperative clinical outcome regarding IPD implants is reported poor in spite of improvement in radiological IPD studies [8][9][10][11][12][13][14]23], could be explained by the fact that previous radiological studies have been performed with the patient in supine relaxed position. As clinical symptoms of LSS are typically induced or exacerbated by walking, standing or hip extension and tend to decrease during forward flexion, squatting or lying supine, the conventional supine MRI may underestimate the severity of the spinal canal stenosis [24].…”

“…It therefore seems reasonable to investigate the spine in a position in which the IPD is intended to affect the spine the most. In spite of the fact that clinical improvement is the most important treatment outcome, a lack of significant improvement in radiological measures indicates insufficient treatment effect and provides a likely patho-anatomical explanation to why IPDs implants lack long-term functionality [9][10][11]23]. Even though the current data are not directly applicable for all IPDs, this study shows insufficient treatment effect already after 3 months postoperatively, and likely previous studies have failed to show this insufficient radiological effect by using MRI without spinal loading.…”

“…Postoperatively, IPDs have shown good short-time clinical effects, but the long-term results have been less clear and a high reoperation rate compared to ODS has been reported [9][10][11]. In contradiction to the lack of long-term improvement in subjective symptoms and high reoperation rates, some studies have shown beneficial radiological effects [12][13][14].…”