Neurosurgical Management of Interspinous Device Complications: A Case Series

Abstract

Background: Best practice guidelines for treating lumbar stenosis include a multidisciplinary approach, ranging from conservative management with physical therapy, medication, and epidural steroid injections to surgical decompression with or without instrumentation. Marketed as an outpatient alternative to a traditional lumbar decompression, interspinous process devices (IPDs) have gained popularity as a minimally invasive stabilization procedure. IPDs have been embraced by non-surgical providers, including physiatrists and anesthesia interventional pain specialists. In the interest of patient safety, it is imperative to formally profile its safety and identify its role in the treatment paradigm for lumbar stenosis.

Case description: We carried out a retrospective review at our institution of neurosurgical consultations for patients with hardware complications following the interspinous device placement procedure. Eight cases within a 3-year period were identified, and patient characteristics and management are illustrated. The series describes the migration of hardware, spinous process fracture, and worsening post-procedural back pain.

Conclusions: IPD placement carries procedural risk and requires a careful pre-operative evaluation of patient imaging and surgical candidacy. We recommend neurosurgical consultation and supervision for higher-risk IPD cases.

Keywords: complications; decompressive laminectomy; interspinous device; lumbar stenosis; minimally invasive (MIS).

Figure 1

Illustration of combined interspinous process device (IPD) retrieval and MIS lumbar decompression. (A) Migrated interspinous process device in situ. (B) Retrieval of migrated IPD. (C) Tubular MIS laminectomy. (D) Completed laminectomy.

Figure 2

Pre-operative sagittal (A) and axial (B) T2 MRI showing L4/5 severe central canal stenosis. Following interspinous spacer placement, sagittal (C) and axial (D) CT scan showing spacer migration into central canal.

Figure 3

Pre-operative sagittal (A) and axial (B) T2 MRI showing grade 1 spondylolisthesis and L4/5 severe central canal stenosis. Following interspinous spacer placement, sagittal (C) and axial (D) CT imaging showing L4 spinous process fracture.

Figure 4

Laminectomy, but not interspinous process device (IPD) implantation, reduces lumbar stenosis. There is no significant radiographic evidence of canal stenosis reduction between implantation and neurosurgical consultation. Canal stenosis only improves in a statistically significant manner after laminectomy. Black datapoints represent patients seen for symptom nonresolution; red datapoints represent patients seen for hardware complications; blue data represent population mean; error bars ±SEM. **p < 0.05 (0.02, post-op compared to either pre-implantation or consultation stenosis). Delta (Δ) denotes patient whose IPD was explanted by interventional pain team.

Figure 5

Interspinous process device (IPD) implantation results in a measurable reduction in lumbar lordosis. Pre- (A) and post- (B) placement X-rays with ventral migration of device into L5/S1 interspace, with evident reduction in lumbar lordosis. (C) IPD implantation tends to reduce lumbar lordosis (pre-implantation mean 56.92 degrees, consultation 52.51 degrees, p = 0.60), but this difference fails to reach statistical significance. (D) This reduction reaches significance when normalizing for pre-implantation lordosis (consultation 95.9% of baseline, difference 4.1%, p = 0.0075). (C,D) Red denotes hardware complications; black denotes nonresolution of symptoms; blue denotes series mean. Error bars mean ± SEM ***p < 0.01.