Anterior Lumbar Discectomy and Fusion in Acute Cauda Equina Syndrome Kimberly-Anne Tan1, Yma Markmann1, Mathew D Sewell1, Andrew J Clarke1, Oliver M Stokes1, Daniel Chan1 1Exeter Spine Unit, Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter NHS Foundation Trust, Exeter, United Kingdom

Introduction Background: Revision posterior decompression, regardless of cauda equina syndrome (CES), has been reported to be associated with significantly higher rates[1] of: dural tears, hematomas & iatrogenic nerve root damage. Purpose: To report on the safety and feasibility of anterior lumbar discectomy & fusion (ALDF) in treating CES caused by recurrent disc herniations that were previously treated by a posterior discectomy. Study Design: Case report on 3 patients who underwent ALDF for incomplete CES due to recurrent disc prolapse, which had previously been treated via posterior lumbar discectomy. [1] Stolke D, Sollmann WP, Seifert V. Intra- and postoperative complications in lumbar disc surgery. Spine (Phila Pa 1976). 1989;14(1):56-9.

Methods Pre-operative MRI Sagittal (A) and Axial (B) of Case 2 B A All three patients were operated upon within 12 hours of presentation. An anterior left-sided retroperitoneal lumbar spine approach, together with a locking, constrained cage packed with allograft bone was used in all 3 cases. Case 1 (53 y.o. male) Case 2 (39 y.o. female) Case 3 (30 y.o. female) Lesion L5/S1 L4/5 No. of previous disc herniations at this level 2 1 Presenting symptoms pre-Anterior Lumbar Discectomy & Fusion (ALDF) Bilateral radicular leg pain, acute onset urinary incontinence Acute onset right leg paraesthesia, diminished right perineal sensation, difficulty initiating urination, unable to feel herself micturating 3-month history of progressive right leg pain and incomplete urinary voiding, decreased perineal sensation bilaterally Intra-operative details Disc was excised under direct vision. PLL defect was visualized using an operating microscope, and sequestered fragments were retrieved without difficulty through the defect. The dural tube was found to be mobile and intact. Large posterior fragment was found to be contiguous with the disc, and with the aid of a microscope, the PLL was taken down to expose the dura. Loose disc fragments were identified through the posterior annular defect centrally, extending distally just beyond the superior L5 endplate, as well as into the axilla of the right L5 nerve root. With the aid of a microscope, these were all retrieved without difficulty, and a posterior lip osteophyte was removed. Pre-operative MRI Sagittal (A) and Axial (B) of Case 2 A B Range of follow-up: 6 weeks – 16 months

Results A B C Complete retrieval of herniated disc material was achieved without difficulty in all cases. No peri-operative infection or neurological injury occurred. All three patients made neurological recovery with regained continence and resolution of leg pain. 6 week postoperative MRI (A&B) & 8-month postoperative weight-bearing lateral radiograph (C) of Case 1 When herniated material was in contiguity with the intervertebral disc, the anterior approach provided an added advantage as the PLL, annular tissue and/or epidural scar tissue (when present) acted as a containing sac from which nuclear material was easily extracted. Thereafter, with compression relieved, any remaining loose material external to the herniation sac was more comfortably retrieved. In our experience, where there has been previous posterior lumbar spine surgery, scar tissue anterior to the dural tube has not required dissection to achieve revision decompression via the anterior approach.

Discussion Conclusion ALDF should be considered as an alternative treatment for recurrent disc herniation following previous posterior decompressive surgery, as a repeat posterior approach infers a higher risk of dural tears especially during release of epidural fibrosis. The anterior approach allows the surgeon to circumvent navigating disrupted anatomy and epidural scar tissue. This is especially pertinent in the face of CES caused by a large disc herniation as the significant canal stenosis permits very little working space. Addition of a fusion to a revision discectomy is acceptable in the face of increasing segmental instability, and chronic back pain especially if coexistent with CES[2-5] ALDF has been shown to have good long-term outcomes[2,6-8] and fusion rates[2-6] The authors do not recommend ALDF in cases where sequestered discs have migrated along the length of the vertebral canal. Conclusion Anterior lumbar discectomy and fusion (ALDF) provides technical advantages over revision posterior surgery that make it feasible and safe for complete removal of canal-filling discs associated with CES. This suggests that ALDF may be more widely indicated in cases of recurrent disc herniation following previous posterior discectomy, regardless of CES. [2] Choi JY, Choi YW, Sung KH. Anterior lumbar interbody fusion in patients with a previous discectomy: minimum 2-year follow-up. Journal of spinal disorders & techniques. 2005;18(4):347-52. [3] Stambough JL. An Algorithmic Approach to Recurrent Lumbar Disk Herniation: Evaluation and Management. Seminars in Spine Surgery. 2008;20(1):2- 13. [4] Li ZH, Tang JG, Hou SX, et al. Four-year follow-up results of transforaminal lumbar interbody fusion as revision surgery for recurrent lumbar disc herniation after conventional discectomy. Journal of Clinical Neuroscience. 2015;22(2):331-7. [5] Greenleaf RM, Harris MB, Bono CM. The Role of Fusion for Recurrent Disk Herniations. Seminars in Spine Surgery. 2011;23(4):242-8. [6] Inoue S, Watanabe T, Hirose A, et al. Anterior discectomy and interbody fusion for lumbar disc herniation. A review of 350 cases. Clinical orthopaedics and related research. 1984;(183):22-31. [7] Vishteh AG, Dickman CA. Anterior lumbar microdiscectomy and interbody fusion for the treatment of recurrent disc herniation. Neurosurgery. 2001;48(2):334-7; discussion 8. [8] Miyamoto K. [Long-term follow-up results of anterior discectomy and interbody fusion for lumbar disc herniation]. Nihon Seikeigeka Gakkai zasshi. 1991;65(12):1179-90.