The Use of Tubular Retractors for Translaminar Discectomy for Cranially and Caudally Extruded Discs

Abstract

Background: The conventional interlaminar approach is adequate for access to most disc herniations in lumbar spine surgery. The access to cranially and caudally migrated disc fragments, by conventional interlaminar fenestration, requires an extension of the fenestration with the potential destruction of the facet joint complex and consequent postsurgical instability. To describe the technique and results of the translaminar technique of targeted discectomy using tubular retractors for the surgical treatment of cranially and caudally extruded discs.

Materials and methods: The study period extended from January 2008 to December 2014. All patients with lumbar herniated discs who failed conservative management were selected for surgery and underwent routine erect radiographs and magnetic resonance imaging (MRI) of the lumbar spine. The patients with cranially or caudally migrated discs were included in this study. The technique involves approaching migrated disc through an oval window (sculpted through an 18 mm tubular retractor using a burr) in the lamina precisely over the location of the migrated disc as predicted by the preoperative MRI (inferior lamina for inferior migration and superior lamina for superior migration). The perioperative parameters studied were operative time, blood loss, complications, Oswestry Disability Index (ODI), and visual analog scale (VAS) for leg pain before surgery and at last followup. In the study, 4 patients underwent a postoperative computed tomography-scan with a three-dimensional reconstruction to visualize the oval window and to rule out any pars fracture. All technical difficulties and complications were analyzed.

Results: 17 patients in the age group of 41-58 years underwent the translaminar technique of targeted discectomy. The migration of disc was cranial in 12 patients and caudal in 5 patients. Fourteen of the affected discs were at the L4-L5 level and three were at the L5-S1 level. The mean VAS (leg pain) scale improved from 8 to 1 and the mean ODI changed from 59.8 to 23.6. There were no intraoperative or postoperative complications encountered in this study. Furthermore, no patient in the present study required a conventional laminotomy or medial facetectomy. There was no evidence of iatrogenic pars injury or instability at the last followup. There were no recurrences till the last followup.

Conclusions: The targeted translaminar approach preserves structures important for segmental spinal stability thus causing minimal anatomical disruption. This approach allows access to the extruded disc fragment and intervertebral disc space comparable to classical approaches.

Keywords: Laminotomy; Magnetic resonance imaging; intervertebral disc; lumbar vertebrae; migrated discs; minimally invasive surgery; nucleolysis; translaminar discectomy.

Figure 1

Diagramatic representation of saw bones showing (a) Coronal illustration of a left sided L4 and a right sided L5 laminotomy hole. (b) Sagittal illustration of the laminotomy holes

Figure 2

(a) Preoperative T2-weighted sagittal magnetic resonance imaging showing the superiorly migrated L4 L5 disc (sacralization of L5). (b) Preoperative T2-weighted axial magnetic resonance imaging showing the migrated disc at left L4 pedicle level. (c) Postoperative sagittal computed tomography scan showing laminotomy of the L4 lamina (sacralization L5). (d) Postoperative three-dimensional reconstruction computed tomography scan showing the laminotomy hole in L4 (sacralization L5)

Figure 3

(a) Preoperative T2-weighted sagittal magnetic resonance imaging showing the inferiorly migrated L4 L5 disc. (b) Preoperative T2-weighted axial magnetic resonance imaging showing the migrated L4 L5 disc at left L5 pedicle level. (c) Postoperative three-dimensional reconstruction computed tomography scan showing the laminotomy hole in L5 on the left side