Posterior vertebral arch cement augmentation (spinoplasty) to prevent fracture of spinous processes after interspinous spacer implant

Abstract

Background and purpose: Interspinous spacers are implanted to treat symptomatic lumbar stenosis. Posterior vertebral element fractures can occur during or after interspinous spacer implants, especially in patients with osteopenia. The purpose of our study was to assess the biomechanical rationale, safety, feasibility, and effectiveness of posterior vertebral arch cement augmentation (spinoplasty) in preventing delayed spinous process fractures after interspinous spacer implants in patients with risk factors for fragility fractures.

Materials and methods: We performed a nonrandomized historically controlled clinical trial. From June 2007 to March 2010, we implanted interspinous spacers in 35 eligible patients with fragility-fracture risk factors. In 19/35 patients treated after April 2009, after we assessed the theoretic biomechanical effects of cement augmentation of the spinous process and laminae by FEM, a percutaneous spinoplasty was also performed. Clinical and radiologic follow-up ranged between 12 and 36 months after the intervention.

Results: No intraprocedural spinous process fractures were observed in either group, and no patients in the 24-hour postoperative period had complications that were procedure-related. Symptomatic delayed spinous process fractures were diagnosed in 4/16 patients who did not undergo spinoplasty (25.0%), while no fractures were diagnosed in the 19 treated patients (P = .035).

Conclusions: Spinoplasty is feasible and safe. It has a biomechanical rationale, as demonstrated by an FEM. In our preliminary experience, it seems effective in preventing delayed fractures of the posterior arch post-interspinous spacer placement in patients at risk for fragility fractures. These patients have a significant risk of developing a symptomatic delayed spinous process fracture if not treated with spinoplasty.

Fig 1.

A and B, Reformatted sagittal CT images of the lumbar spine show central canal stenosis and spondylolisthesis (A), partially corrected after interspinous spacer implant (B). C and D, In a different patient, postimplantation CT (C) and follow-up CT (D), prompted by neurogenic claudication recurrence, show support failure of the spinous processes and subsidence of the implant, with recurrence of central canal stenosis.

Fig 2.

A and B, Intraprocedural fluoroscopic images show needle placement in the spinous processes for spinoplasty. The fluoroscopic ventral limit to avoid central canal violation is the posterior margin of the inferior articular process (black arrows on B). C–E, Postspinoplasty fluoroscopic (C and D) and CT (E) images show PMMA distribution in spinous processes and laminae.

Fig 3.

Intraprocedural fluoroscopic image (A) of the percutaneous insertion of the interspinous spacer, following spinoplasty. Postimplantation control images (B and C) show the end result of spinoplasty and interspinous spacer implant.

Fig 4.

A and B, Radiologic follow-up 3 months postimplantation with plain films in 2 views of the lumbar spine shows the device in place and the absence of significant subsidence or fractures of the spinous processes or laminae. Minimal cortical bone remodeling at the bone-metal interface is noted.