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EXPERT’S OPINION •SPINE - LUMBAR
Lumbar foraminal stenosis, the hidden stenosis including at L5/S1
Sumihisa Orita
1
•Kazuhide Inage
1
•Yawara Eguchi
2
•Go Kubota
3
•
Yasuchika Aoki
3
•Junichi Nakamura
1
•Yusuke Matsuura
1
•Takeo Furuya
1
•
Masao Koda
1
•Seiji Ohtori
1
Received: 31 May 2016 / Accepted: 10 June 2016 / Published online: 18 June 2016
Springer-Verlag France 2016
Abstract In patients with lower back and leg pain, lumbar
foraminal stenosis (LFS) is one of the most important
pathologies, especially for predominant radicular symp-
toms. LFS pathology can develop as a result of progressing
spinal degeneration and is characterized by exacerbation
with foraminal narrowing caused by lumbar extension
(Kemp’s sign). However, there is a lack of critical clinical
findings for LFS pathology. Therefore, patients with robust
and persistent leg pain, which is exacerbated by lumbar
extension, should be suspected of LFS. Radiological
diagnosis is performed using multiple radiological modal-
ities, such as magnetic resonance imaging, including plain
examination and novel protocols such as diffusion tensor
imaging, as well as dynamic X-ray, and computed
tomography. Electrophysiological testing can also aid
diagnosis. Treatment options include both conservative and
surgical approaches. Conservative treatment includes
medication, rehabilitation, and spinal nerve block. Surgery
should be considered when the pathology is refractory to
conservative treatment and requires direct decompression
of the exiting nerve root, including the dorsal root ganglia.
In cases with decreased intervertebral height and/or insta-
bility, fusion surgery should also be considered. Recent
advancements in minimally invasive lumbar lateral
interbody fusion procedures enable effective and less
invasive foraminal enlargement compared with traditional
fusion surgeries such as transforaminal lumbar interbody
fusion. The lumbosacral junction can cause L5 radicu-
lopathy with greater incidence than other lumbar levels as a
result of anatomical and epidemiological factors, which
should be better addressed when treating clinical lower
back pain.
Keywords Foramen Lumbar spine Radiculopathy
Fusion Diffusion tensor imaging (DTI) Oblique lateral
interbody fusion (OLIF)
What is ‘‘lumbar foraminal stenosis’’? Conceptual
and epidemiological facts
The lumbar intervertebral foramen is a space that contains
the spinal nerve and dorsal root ganglia (DRG), which are
composed of sensory neurons. Lee et al. subdivided the
lateral intervertebral region into the lateral recess (en-
trance) zone, foraminal zone (vertical interpedicular
[foramen]) zone, and extraforaminal zone [1,2]. The
foraminal zone lies beneath the lamina and facet joints and
is also appropriately referred to as the ‘‘hidden zone’’ [3]
(Fig. 1). The pathology of lumbar foraminal stenosis (LFS)
was first reported in 1927 [4,5] as one of possible origins
of sciatica caused by a transitional sacrum. After the sys-
tematic integration of the concept of lumbar spinal stenosis
[6], the concept of LFS was defined as one of the lateral
spinal stenoses [7]. The prevalence of LFS has been
reported to be 8–11 % [8,9], and a previous cadaveric
study identified LFS in 21 of the 100 lumbar foramina
examined [10]. Clinical LFS is often unrecognized and
accounts for approximately 60 % of failed back surgery
&Sumihisa Orita
sorita@chiba-u.jp
1
Department of Orthopaedic Surgery, Graduate School of
Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku,
Chiba 260-8670, Japan
2
Department of Orthopaedic Surgery, National Hospital
Organization, Shimoshizu Hospital, Yotsukaido, Japan
3
Department of Orthopaedic Surgery, Eastern Chiba Medical
Center, Togane, Japan
123
Eur J Orthop Surg Traumatol (2016) 26:685–693
DOI 10.1007/s00590-016-1806-7
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