The Endoscopic Lateral Approach for the Lumber Spine Hidden Zone in Sciatica Patients: Two Cases

Case Report 

The Endoscopic Lateral Approach for the Lumber Spine Hidden Zone in Sciatica Patients: Two Cases

Corresponding author Dr. Hiraku Kikuchi, MD, Department of Orthopaedic Surgery, Kindai University Sakai Hospital, 590-0132, 2-7-1 Harayama-dai, Sakai-city, Osaka, Japan; Tel: 072-299-1120; Fax: 072-299-6066; Email:hiraku@sakai.med.kindai.ac.jp

Abstract

We performed micro-endoscopic discectomy (MED) using the lateral approach on patients with sciatica and achieved good results with high patient satisfaction. Case 1: A 34-year-old man, who was a restaurant manager, had been experiencing back pain for 4 years. Only a nerve root block at L5 was effective in improving his symptoms. Surgery, using an intra-spinal approach at L4/5 and a lateral (extra-foraminal) approach at L5/S1, was employed for the treatment of extra-foraminal disc herniation (EFDH, often called hidden zone herniation). The patient returned to his original work without any complaints. Case 2: A 77-year-old housewife who developed recurrent right sciatic pain. The nerve root at L5 had been impinged by the costotransverse ligament and herniation from the ventral and dorsal sides. Her pain started to lessen on the next postoperative day. We believe that this approach is suitable for patients with sciatica due to lesions located in the hidden zone, thus preventing definitive diagnosis.Keywords: Micro-endoscopic discectomy; Lateral (extra-foraminal) Approach; Hidden Zone; Nerve Root block

AbbreviationsCT: Computed Tomography;

CTM: Computed Tomographic Myelography;

MRI: Magnetic Resonance Imaging;

PLIF: Posterior lumbar Interbody Fusion;

MED: micro-Endoscopic Discectomy;

JOA score: Japanese Orthopaedic Association Scale Score

With the advent of computed tomography (CT) and magnetic resonance imaging (MRI), there has been considerable improvement in the diagnosis of sciatica. Though sciatica generally refers to radicular leg pain, sciatica after lumbar spinal surgery may result from lesions located in the hidden zone of the lumbar spine, which often poses a challenge for diagnosis and treatment. We performed micro-endoscopic discectomy (MED, introduced by Foley et al. in 1997 [1], and others [2, 3]) using the lateral approach on two patients with sciatica and achieved good results.

Cases

Case 1:A 34-year-old man, who was a restaurant manager, had been experiencing intermittent back pain for approximately 4 years.  The patient was referred to our hospital because he developed left sciatic nerve pain, which is due to radiculopathy. This condition was rather difficult for him to keep working (Table1).

Table 1. Clinical findings on admission for case 1.
MRI showed degeneration of the intervertebral disc at the L4/5 level but did not reveal a hernia; a CT-myelogram (CTM) showed no abnormalities (Figure 1).
Figure 1. Magnetic resonance images showing that there was no disc herniation at the L4/5 vertebrae.
(A) : axial view (yellow arrow: extra-foraminal area)
(B): transverse view
(C) : frontal viewOnly a nerve root block at L5 was effective in improving the symptoms (Figure 2). Thus, surgery, using an intra-foraminal approach at L4/5 and an extra-foraminal approach at L5/S1, was employed for EFDH. There were no remarkable findings within the spinal canal at L4/5. Adhesions of the nerve root and residual hernia were noted in the intervertebral foramen at L5 (Figure 3). The operative time was 144 minutes. The amount of blood loss was 154 mL. The detail of the operation was follows: At first, an operator inserted endoscopy (tubular retractor) at left side of L4/5 intervertebral level under general anesthesia, and observed the spinal canal. The observed

Figure 2. A nerve root block was applied, and the symptoms temporarily improved after a root block at the L5 vertebra (under pedicle projection and L4 foraminal zone). Yellow arrow: Left L4 root intra hidden zone was enhanced. Red square area is ipsilateral L4 hidden zone area.finding was that there was no disc herniation, L5 nerve root run into the hole of the vertebral arch without any sign of stress. Therefore, we convinced that ball probe easily can be inserted into the whole lamina. Further observation around the exit of the vertebral arch revealed that L5 nerve root was coalesced with scar tissue around the nerve roots and had no degrees of freedom. Therefore, whole scar tissue around L5 nerve root was softly removed by peeling off the adhesion to get the nerve roots free.

Figure 3. An intraoperative image showing adhesions of the nerve root at the L5 vertebra and the surrounding tissue in the  intervertebral foramen. White arrow (R to L) indicated herniation surrounding adhesion area. Yellow arrow (up to down) showed epidural tube.

The patient was discharged 15 days after operation as she wanted to stay in hospital till the suture removal. The post-operative Japanese Orthopaedic Association (JOA[4]) score was 29. The patient returned to his original work without any complaints.

Case 2:

The patient was a 77-year-old housewife. She had previously undergone laminectomy and posterior lumbar interbody fusion (L3/4/5) at another hospital. Her symptoms resolved following the operation. However, 4 years later, she developed right sciatica (Table 2). She received a nerve block at a local hospital, where she was diagnosed with lumbar nerve root canal stenosis at L5, and was referred to our hospital (Figure 4). The spine was approached through the lateral intervertebral foramen at L5/S1. The nerve root at L5 was found to be impinged by the costotransverse ligament and herniation from the ventral and dorsal sides (Figure 5). The operative time was 221 minutes and the amount of blood loss was 370 mL. The pain started to lessen the next day. The patient was discharged 9 days after surgery. The post-operative JOA score was 22.

Table 2. Clinical findings on admission for case 2.

Figure 4. (A): Pre-operative AP view. (B): A nerve root block was performed at the right L5 vertebra, and the pain was temporarily relieved.

Figure 5. Intraoperative endoscopic view: (A), dissection of the costotransverse ligament; (B), lifting of the nerve root at L5 (white arrow) and removal of the spinous process (yellow arrow); (C), removal of the intervertebral disc (blue arrow).
Discussion
The causes of sciatica include lumbar disc hernia, lumbar spondylolisthesis, and degenerative diseases such as osteoarthritis of the spine and lumbar spinal canal stenosis, tumor, and piriformis muscle syndrome [5, 6]. The number of patients diagnosed has become increasingly accurate with the advent of myelography, CTM, and MRI in particular [7,8]. However, diagnosis is still difficult in cases of disc herniation in the intervertebral foramen, as in Case 1, and that prolapsed to the hidden zone (which is a terminology introduced by

Macnab [9] indicating difficult surgical exposure, and has been used elsewhere since then [10]. The incidence of the  condition with respect to the total cases of lumbar disc hernia was reported to be 7–12% [11]. It is difficult to make a definite diagnosis in cases that have previously been treated with instrumentations. Case 2 is such a case, where CT and MRI figures cannot show the hidden zone. Therefore, the decision to perform the surgery is made only after confirming a temporary improvement in symptoms after nerve block. The posterior approach is used for the operation. Conventionally, a mid-line approach that accesses the spine by detaching the back muscles from the spinous processes and Wiltse’s approach that accesses the spine through the fascia between the longissimus and multifidus muscles have been employed [12, 13]. However,  these surgical techniques are invasive because they require a large skin incision and lumbar fusion in order to observe the nerve root and hernia through resection of the intervertebral joint [14,15]. MED with a lateral approach provides a good operative view by inserting a tubular retractor, such as in the procedure for nerve root block [5, 6, 13]. Compared with the conventional method in which the lesion is viewed only from  straight above, it has an advantage in that it uses an oblique viewing endoscope with an inclined angle of 20° that allows us observation of the nerve root through the intervertebral foramen from an oblique perspective. That is, this technique allows close observation of the nerve root. In addition, there isno need to perform lumbar fusion because the intervertebral foramen is dilated to release the nerve root, but  ot resected [16]. This approach is minimally invasive and does not require substantial rehabilitation after operation. We believe that this approach is suitable for patients with sciatica due to lesions located in the hidden zone, thus preventing definitive diagnosis.

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