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INTRODUCTION
Discectomiesinlumbosacral disc herniation was first described byMixter and Barr in 1934 as a
combination of laminotomy,disc removal, and neural decompression.AfterLove (1939) andCasper (1977),
spinal surgery was considered minimally invasive whena new procedure which reduced tissue injury to the
minimum was discovered. In 1997, Foley proposed a new method usingdilators with increasing diameters to
approach via paraspinal muscles with support of endoscope and special systems. This method made the
posterior approach in discectomies genuinely ‘minimally invasive’.
In Vietnam, spinal surgery, especially minimally invasive spinal surgery, has only been paid attention to
develop in recent years. According to VISTA network from the National Agency for Science and
Technology Information, to the end of 2012, there have been 137 articles about spinal issues; among these,
40 articles are about spinal surgery and one is related to minimally invasive surgery using dilators. Of
493,413 PhD theses in the National Library, 29 theses are related to treatment of spinal conditions; however,
there are no theses mentioning minimally invasive surgery using dilators.
This is a new approach in Vietnam, and the data about its safety and efficiency are limited. Hence, we
conduct a study on “Application of tubular retractordiscectomy for single-level lumbosacral disc
herniation in Viet Duc University Hospital” with two aims:
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1. To describe the clinical and paraclinical characteristics of single-level lumbosacral disc
herniation,and
2. To evaluate the surgical outcome, indication and surgical protocol of the surgery of lumbosacral
disc herniation using dilators.
Contribution:
- A study with adequacy of diagnostic criteria and indication for surgery using dilators.
- Formulate the diagnostic approach and treatment indication of single-level lumbosacral disc
herniation.
Content: 128 pages in 4 chapters:
Introduction 3 pages
Chapter 1: Overview 33 pages
Chapter 2: Method 25 pages
Chapter 3: Results 26 pages

3,173 patients (age 14-91) with total intervened discs of 5,909 It can been seen that surgical centers
specialized in spinal surgery have been implementing minimally invasive techniques, but studies on surgery
using dilators are limited.
1.2. ANATOMY RELATED TO MINIMALLY INVASIVE SURGERY
From the inferior border of the pedicle, the vertebrae can be divided into six components – three
superior components including 2 superior articular processes, 2 transverse processes, and 2 pedicles; and
three inferior components including 2 laminae, 2 inferior articular processes, and 1 spinal process. The only
components that lie at the same level of the inferior border are the junctions between the lamina and the
pedicle.
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From inferior to superior, there are three floors as described: floor 1 (disc), floor 2 (intervertebral
foramen), and floor 3 (pedicle).
Depending on the position of the migrated disc, we will direct the dilators to the area under the support
of C-arm.
Some anatomic abnormalities of the lumbosacral spine are congenital bone deformities and lumbosacral
root abnormalities.
1.3.CLINICAL AND PARACLINICAL CHARACTERISTICS OF LUMBOSACRAL DISC
HERNIATION:
1.3.1. Clinical signs and symptoms:
Two major syndromes: Lumbar syndrome (low back pain, paraspinal localized pain, limited range of
motion of the lumbar spine) and Nerve-root syndrome (pain radiating to the area supplied by the nerve,root
stimulating signs, Lasègue sign, sensory disorder, motor disorder, deep tendon reflex disorder).
1.3.2. Imaging:
Plain spine X-raycan evaluate spine instability and the condition of the posterior arch.Lumbosacral CT
scancan provide better assessment of the bony structure and detect some abnormalities.Lumbosacral MRIcan
detect different types of disc herniation:disc protrusion (protrusion of the nucleus pulposus outside of the
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border of the adjacent vertebrae); disc extrusion (extrusion of the nucleus pulposus outside of the fibrous
ring); anddisc migration (the nucleus pulposus is sequestrated and separated from the disc).
1.4.SURGICAL TREATMENT OF LUMBOSACRAL DISC HERNIATION

Disability Index.
* Nerve-root compression syndrome:sensory disorder, Lasègue sign, deep tendon reflex disorder.
* Muscle strength and sensory assessment: ASIA (2006).
+ Imaging:
Plain X-ray andbendingX-ray,lumbosacral MRI.
Treatment indication:
+ Surgical indication: disc hernation with cauda equina syndrome(emergency); disc herniation with
paralysis (due to compression).
+ Surgical indication with dilators:criteria are (1) single-levelherination; (2) herniation without
instability; (3) herniation without spinal stenosis; và (4) herniation with pain radiation to unilateral leg,
consistent wih the side of compression.
+ Exclusive criteria:Absolute contraindication- (1) Lumbar spine instability; (2) Spinal stenosis,
multiple-level disc herniation (≥3 level); and (3) Systemic diseases that are contraindicated to surgery.
Relative contraindication–previous surgery at the side of compression (recurrent herniation); coagulopathy;
>2-level herniation; and surgical center out of capabilities.
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Minimally invasive discectomy with METRx and Quadrant:
Technical requirements:IntraoperativeC–arms (SIEMENS Pb r8 N40 fo90), METRx and Quadrant
system (Medtronic Inc), specialized surgical instruments.
Discectomy with dilators.
Early rehabilitation (48 hour postoperative). Wear lumbosacral back brace in 2 weeks.
Postoperative information:
Using the study medical report, after 6 and 12 months.
• Clinical:NRS, ODI, general outcome
• Imaging:MRI, bending X-ray.
• Time to back-to-work
• Ouctcome assessment based onmodified Macnab criteria.
2.4.DIAGNOSTIC AND TREATMENT APPROACH OF LUMBOSACRAL DISC HERNIATION
2.4.1. Preoperative assessment
Clinical: History taking and physical examination.

and herniation type
Degenerative
grade
Herniation type Total
Protrusion Extrusion Migration
II 3
(2 %)
18
(11,9 %)
1
(0,7 %)
22
(14,6 %)
III 17 84 17 118
13
(11,3 %) (55,6 %) (11,3 %) (78,1 %)
IV 1
(0,7 %)
6
(4 %)
4
(2,6 %)
11
(7,3 %)
Total 21
(13,9 %)
108
(71,5 %)
22
(14,6 %)

(4,6 %)
22
(14,6 %)
Total 59 78 14 151
14
(39,1 %) (51,7 %) (9,3 %) (100 %)
Table 3: Relationship between herniation type and
preoperative leg NRS
Leg NRS Herniation type Total
Protrusion Extrusion Migration
<5 16
(10,6 %)
71
(47 %)
10
(6,6 %)
97
(64,2 %)
>5 5
(3,3 %)
37
(24,5 %)
12
(7,9 %)
54
(35,8 %)
Total 21
(13,9 %)
108
(71,5 %)

(14,6 %)
151
(100 %)
Table 5: Relationship between legNRSanddegenerative grade
Leg NRS Degenerative grade Total
II III IV
<5 12
(7,9 %)
81
(53,6 %)
4
(2,6 %)
97
(64,2 %)
>5 10
(6,6 %)
37
(24,5 %)
7
(4,6 %)
54
(35,8 %)
Total 22
(14,6 %)
118
(78,1 %)
11
(7,3 %)
151
(100 %)

Table 7: Relationship between outcomeand timing of leg pain
Timing
Outcome
<3 months >3 months Total
Excellent 20 3 23
Good 94 13 107
Medium 4 12 16
Bad 1 4 5
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Total 119 32 151
Table 8: Relationship between outcome and HOS
HOS
Outcome
Central Lateral recess Foramen Extra-
foramen
Total
Excellent 2 11 10 0 23
Good 63 22 20 0 105
Medium 13 5 0 0 18
Bad 3 1 1 0 5
Total 81 39 31 0 151
Table 8: Relationship between outcome and herniation floor
Floor
Outcome
I II III Total
Excellent 2 9 12 23
Good 70 4 35 109
Medium 12 1 1 14
Bad 4 0 1 5
Total 88 14 39 151

(68,9 %)
4
(2,6 %)
0
(0 %)
Migration
10
(6,6 %)
12
(7,9 %)
0
(0 %)
14
(9,3 %)
7
(4,6 %)
1
(0,7 %)
Table 11: Age-weighted improvement using ODI
Age ≤ 59 > 59
p < 0.05Preop ODI 54 ± 12,4 60 ± 19,8
Postop ODI 22 ± 5,1 24 ± 12,7
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Chart 1: Changes of back pain severity with time
Table 12: Improvement of back NRS and herniation type
Back NRS Herniation type
Protrusion Extrusion Migration
Preop <5 14
(9,3 %)
69

(46,4 %)
7
(4,6 %)
>5 9
(6 %)
48
(31,8 %)
4
(2,6 %)
Postop
<5 22
(14,6 %)
118
(78,1 %)
11
(7,3 %)
>5 0
(0 %)
0
(0 %)
0
(0 %)
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Chart2:Changes of leg pain severity with time
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Table 12: Improvement of leg NRS and herniation type
Back NRS Herniation type
Protrusion
Extrusion
Migration

Table 15: Complications
N %
Tearing of spinal cord membrane 3 1.9
Nerve root injury 2 1.3
Cauda equina syndrome 0 0
Incision infection 0 0
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Cerebrospinal fluid leakage 0 0
No complications 146 96.8
Total 151 100
Chapter 4
DISCUSSION
4.1. GENERAL CHARACTERISTICS
4.2. CLINICAL AND PARACLINICAL CHARACTERISTICS
4.2.1. Clinical characteristics
Pain (usingNRS)
Back and leg mean NRS are 4,3 ± 1,5 and 4 ± 1,2, respectively, and have no significant differences.
Back and leg mode NRS are 6 and 5, respectively. 43% patients have a timing of onset of >12 months;
timing of <1 month only accounts for 9,3%.
Reduced function of the lumbar spine (using ODI)
Mean ODI is 52,9 ± 12,8 (%) (min 22%, max 72%).
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93 of 151 (61,6 %) patients have moderately and severely reduced function. 2 patients’ functionis
completely reduced.
Preoperative leg pain:
Every patient has leg pain before surgery. 65 patients (43%) developed leg pain in a period of>12
months, only 11patients (9,3%) developed leg pain in a period of<1 month.
4.2.2. Imaging
Degenerative grade and age group:
Herniation type