Upsala Journal of Medical Sciences. 2012; 117: 426–429

ORIGINAL ARTICLE

Improvement of hip abductor muscle weakness after lumbar
decompressive surgery

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TATSURO SASAJI, KIYOSHI HORAGUCHI, NOBORU YAMADA & KAZUO IWAI
Department of Orthopedic Surgery, Fukushima Rosai Hospital, 3-Numajiri, Tsuzura-machi, Uchigo, Iwaki 973-8403,
Japan

Abstract
Introduction. Degenerative lumbar spinal disorder is common in Japan, and the L5 nerve root is commonly involved in thisdisorder. The symptoms of L5 radiculopathy are irradiating lateral leg pain, and numbness and weakness of tibialis anterior andthe hip abductor muscle. There has been only one report on the results of surgery for hip abductor muscle weakness caused bydegenerative lumbar spinal disorder.
Patients and methods. In this study, we analyzed the strength of the hip abductor muscle before and after decompressive surgery
in 26 cases and the relationship between the lumbar disc herniation (LDH) and lumbar spinal canal stenosis (LSCS) groups.
Results. Of the total 26 cases, muscle strength improved in 23 cases (88%), with complete recovery in 17 cases (65%). In theLDH group, the improvement rate was 92%. In the LSCS group, the improvement rate was 68%. Although the improvement
rate for the LDH group was higher than that for the LSCS group, the difference was not signiﬁcant (P = 0.054).
Discussion. Decompressive surgery may be an effective method to improve hip abductor muscle weakness in degenerative
lumbar spinal disorder.

Key words: Decompressive surgery, degenerative lumbar spinal disorder, hip abductor muscle, L5 radiculopathy,
muscle weakness

Introduction

Patients and methods

Japan is an aging society, and the incidence of degenerative lumbar spinal disorder is increasing. The
major neurological symptoms of lumbar spinal disorder are radicular pain and numbness and sometimes
muscle weakness in the leg. Improvement of leg
muscle strength is critical because it interferes withdaily life. L5 radiculopathy causes muscle weakness
not only in tibialis anterior (TA), but also in the hip
abductor muscle (1). Surgical results for drop foothave been reported (2-5). However, there was only
one report of surgical results on hip abductor muscle
weakness (4). In this study, we report surgical resultson hip abductor muscle weakness from degenerative
lumbar spinal disorder.

All patients were informed that the data from theircases would be used for this study.
Subjects
This study included 26 consecutive patients(10 females and 16 males, aged 24–82 years, meanage 66 years) who were referred to our institute forsurgical treatment between 2010 and 2011 andunderwent follow-up examinations for a minimumof 1 year. The mean follow-up period was 14 months(range 12–22 months). The diagnosis of degenerative
lumbar spinal disorder was based on clinical symptoms, neurological examinations, and magnetic

Correspondence: Tatsuro Sasaji, Department of Orthopedic Surgery, Fukushima Rosai Hospital, 3-Numajiri, Tsuzura-machi, Uchigo, Iwaki 973-8403, Japan.
Fax: +81-246-26-1322. E-mail: taturosasaji@hotmail.com(Received 24 April 2012; accepted 25 June 2012)ISSN 0300-9734 print/ISSN 2000-1967 online  2012 Informa Healthcare
DOI: 10.3109/03009734.2012.708678

Improvement of hip abductor muscle weakness
Surgical procedures

Table I. Improvement of hip abductor muscle strength.
LDH (n = 11)

LSCS (n = 15)Age, years

56 ± 1872 ± 7

Mean preoperative muscle
strength, arbitrary units, 0–5

2.7

2.6

Mean postoperative muscle
strength, arbitrary units, 0–5

4.8

4.3

Improvement rate (%)

92

68

The mean age between groups at the time of surgery was signiﬁcantly different (P = 0.02). The improvement rates between LDH
and LSCS groups were not signiﬁcantly different (P = 0.054).
LDH = lumbar disc herniation; LSCS = lumbar spinal canalstenosis.

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427

resonance imaging of the lumbar spine. All patients
had typical neurological symptoms of L5 radiculopathy including irradiating lateral leg pain andnumbness, and weakness of hip abductor muscle.
The degenerative lumbar spinal disorders included
lumbar disc herniation (LDH) and lumbar spinal
canal stenosis (LSCS). The LSCS cases included
central canal stenosis and foraminal stenosis. In
LDH and central canal stenosis, the L4–5 segment
was involved. In foraminal stenosis, the L5–S segment
was involved. The exclusion criteria for this study
included prior lumbar spinal surgery and osteoarthritis of the hip. The LDH group included 6males and 5 females with a mean ± SD age at thetime of surgery of 56 ± 18 years (range 24–77 years).
The LSCS group included 10 males and 5 femaleswith a mean ± SD age at the time of surgery of 72 ±7 years (range 60–83 years) (Table I). The mean
age was signiﬁcantly higher in the LSCS groupthan in the LDH group (P = 0.02, Student’s t test).
This study did not include unstable spinal cases,and thus decompressive surgery was performed
without fusion.

All surgeries were performed by a single spinal surgeon. For LDH, a simple open discectomy was performed. For central canal stenosis, wide fenestration
was performed (Figure 1) (6). For foraminal stenosis,
wide fenestration and lateral fenestration were performed (Figure 1).
Clinical evaluation
We evaluated the strength of the hip abductor muscle
before surgery and at the ﬁnal follow-up examination
using a manual muscle test. Muscle strength wasgraded on a 0 (paralysis) to 5 (normal strength)(arbitrary units) scale (Table II) (7).
Calculation of percentage of improvement rate
The relationship between the LDH and LSCS groups
and the improvement rates in hip abductor muscle
weakness after surgery were analyzed. Surgical results
were measured by postoperative muscle strength.
The percentage of improvement rate was calculated as follows: (postoperative muscle strength
preoperative muscle strength)/(5 – preoperativemuscle strength) 100.
Statistical analysis
For statistical purposes, the improvement rate data
were compared using the Student’s t-test. A probability value of less than 0.05 was considered signiﬁcant. Statistical analyses were performed using
GraphPad Prism (GraphPad Software, Inc., SanDiego, CA, USA).
Results
There were 11 LDH cases and 15 LSCS cases.
Six patients had preoperative muscle strength of 4,

Figure 1. Schemata of surgeries. These schemata show decompression of the right side. The shaded area is the decompressed area. The wide
fenestration decompressed the dura and nerve root in the entry zone (left). The wide fenestration and lateral fenestration decompressed thedura and nerve root in the entry, mid, and exit zones (right).

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T. Sasaji et al.

Table II. Muscle strength (7).

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Grade, arbitrary units

Characteristic68%. Although the improvement rate was higher inthe LDH group, this increase was not signiﬁcant(P = 0.054) (Table I).

5

Active movement against full resistance4

Active movement against gravity andsome resistance

Discussion

3

Active movement against gravity

2

Active movement with gravity eliminated1

Trace movement or barely detectable
contraction0

No muscular contraction identiﬁed

The L5 nerve root is commonly involved indegenerative lumbar spinal disorder (1). TheL5 nerve root innervates extensor hallucis longus,
tibialis anterior, and the hip abductor muscle (1).
There has been only one report on surgical outcomesfor hip abductor muscle weakness (4). According
to Lee et al., in case of unilateral hip abductor
muscle weakness caused by L5 radiculopathy, thepelvis of the affected side inclined upward and thepelvis of the unaffected side inclined downward (8).
If postoperative improvement of hip abductor
muscle strength is inadequate, the gait disturbancewould be expected to continue. Therefore, we
concluded that it was necessary to investigate theimprovement rate in hip abductor muscle strength
after surgery.
In the study by Girardi et al., 94% of patients experienced full recovery of abductor strength, but thestrength of hip abductor muscle was not reported (4).
In this study, the full recovery rate was 65%. We could
not compare the full recovery rate.
In this study, the improvement rate in hip abductor
muscle strength did not differ signiﬁcantly between theLDH and LSCS groups despite the higher mean age inthe LSCS group. We assumed that hip abductor muscle weakness caused by either LSCS or LDH would beindicative of the need for decompressive surgery. However, the number of cases in this study was small.
Therefore, further studies with a larger number ofpatients would be necessary to address this question.

six patients had preoperative muscle strength of 3, andfourteen patients had preoperative muscle strengthof 2. At the ﬁnal follow-up examination, seventeen
patients had postoperative muscle strength of 5, sevenpatients had muscle strength of 4, one patient had amuscle strength of 3, and one patient had a muscle
strength of 2 (Figure 2). Of the 26 patients, 23 patients
showed postoperative improvement and 3 patients
showed no change. The mean improvement rate
was 78%, and full recovery was achieved in 17 cases(65%). All of the unchanged cases were LSCS
and males with a mean age of 78 years (range 71–83 years).
In the LDH group, the mean preoperative muscle
strength was 2.7 (range 2–4), and the mean postoperative muscle strength was 4.8 (range 4–5). The
improvement rate was 92%. In the LSCS group, themean preoperative muscle strength was 2.6 (range2–4), and the mean postoperative muscle strength
was 4.3 (range 2–5). The improvement rate was
Muscle strength5

Declaration of interest: The authors report noconﬂicts of interest. The authors alone are responsible
for the content and writing of the paper.

43References
210
Preop

PostopFigure 2. Changes in muscle strength. Twenty-three cases improved
postoperatively including seventeen cases with a complete recovery.
Muscle strength improved from 2 to 5 in eight cases, from 3 to 5 inﬁve cases, from 4 to 5 in four cases, from 2 to 4 in four cases, from3 to 4 in one case, and from 2 to 3 in one case. Preop = preoperative.
Postop = postoperative.

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