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The influence of hand grip strength on surgical outcomes after surgery for degenerative lumbar spinal stenosis: a preliminary result
Accepted Manuscript Title: The influence of hand grip strength on surgical outcomes after surgery for degenerative lumbar spinal stenosis: a preliminary result Author: Feng Shen, Ho-Joong Kim, Na-Kyoung Lee, Heoung-Jae Chun, BongSoon Chang, Choon-Ki Lee, Jin S. Yeom PII: DOI: Reference:
S1529-9430(18)30163-3 https://doi.org/10.1016/j.spinee.2018.04.009 SPINEE 57650
To appear in:
The Spine Journal
Received date: Revised date: Accepted date:
21-1-2018 23-3-2018 9-4-2018
Please cite this article as: Feng Shen, Ho-Joong Kim, Na-Kyoung Lee, Heoung-Jae Chun, BongSoon Chang, Choon-Ki Lee, Jin S. Yeom, The influence of hand grip strength on surgical outcomes after surgery for degenerative lumbar spinal stenosis: a preliminary result, The Spine Journal (2018), https://doi.org/10.1016/j.spinee.2018.04.009. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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The influence of hand grip strength on surgical outcomes after surgery for degenerative
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lumbar spinal stenosis: a preliminary result
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Feng Shen, MDa, Ho-Joong Kim, MDa,*, Na-Kyoung Lee, MDa, Heoung-Jae Chun, PhDc, Bong-Soon Chang, MDb, Choon-Ki Lee, MDb, Jin S. Yeom, MDa
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a
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Medicine and Seoul National University Bundang Hospital, 166 Gumiro, Bundang-gu,
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Sungnam 463-707, Republic of Korea
Spine Center and Department of Orthopedic Surgery, Seoul National University College of
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b
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Seoul National University Hospital, 101 Daehangno, Jongno-gu, Seoul 110-744, Republic of
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Korea
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c
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Republic of Korea
Department of Orthopaedic Surgery, Seoul National University College of Medicine and
Department of Mechanical Engineering, Yonsei University, Seodaemun-gu, Seoul, 03722,
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Acknowledgement:
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This research was supported by Basic Science Research Program through the National
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Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and
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Technology (2016R1A2B3012850).
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Address correspondence and reprint requests to:
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Ho-Joong Kim, MD
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Spine Center and Department of Orthopaedic Surgery,
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Seoul National University College of Medicine and Seoul National University Bundang
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Hospital, 166 Gumiro, Bundang-gu, Sungnam 463-707, Republic of Korea
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Tel: +82317877202
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E-mail: [email protected]
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Abstract
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Background Context: Although a number of prognostic factors have been demonstrated to
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be associated with surgical outcome of degenerative lumbar spinal stenosis (DLSS), no study
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has investigated the relation between hand grip strength (HGS) and treatment outcome of
9
DLSS.
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Purpose: The purpose of this study was to examine the influence of HGS on surgical
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outcomes after surgery for patients with DLSS.
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Study design: An observational study
13
Patient Sample: Patients who underwent spine surgery for DLSS.
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Outcome Measures: Oswestry Disability Index (ODI), EuroQOL (EQ-5D), and visual
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analog scale (VAS) for back/ leg pain.
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Methods: A total of 172 consecutive patients who underwent spine surgery for DLSS were
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included in this study. Patients were assigned to either a high HGS ( 26 kg for men and
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kg for women, n=124) or low HGS group (< 26 kg for men and < 18 kg for women, n=48)
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based on their preoperative HGS performance. ODI, EQ-5D, VAS for back and leg pain were
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assessed and compared between two groups preoperatively, 3 and 6 months after surgery. The
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primary outcome measure was baseline-adjusted ODI scores 6 months after surgery. The
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secondary outcome measures, including the overall ODI score, EQ-5D score, VAS score for
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back and leg pain, were assessed at each time point during the 6 months follow-up period.
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Results: As primary outcome, baseline-adjusted ODI scores was significant lower in high
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HGS group than it in low HGS group 6 months after surgery. In the secondary outcome
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measurements, the ODI, EQ-5D, VAS score for back and leg pain improved significantly
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with time after surgery in both groups. The effects of HGS group on the overall changes in
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the ODI and EQ-5D during the 6months period were significantly different between the two
9
groups, however, they were not significantly different on VAS for back and leg pain. The
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pattern of change in the ODI during the follow-up period was significantly different betwee
11
n the two groups.
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Conclusions: Patients with preoperative high HGS display better surgical outcome in terms
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of disability and health status 6 months after spine surgery. Preoperative HGS can act as a
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predictor of surgical outcome in spine surgery in patients with DLSS.
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Keywords: hand grip strength; degenerative change; lumbar spinal stenosis; spine surgery;
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surgical outcomes; predictor
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Introduction
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Previous study has suggested that performance-based functional assessment could provide
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important prognostic information concerning acute or chronic diseases [1]. As a performance-
8
based functional assessment method, muscle strength is associated with physical functionality
9
and nutritional status [2]. Hand grip strength (HGS), a measure of voluntary muscle function,
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has often been used as an indicator of muscle strength. Regarding it as simple, quick, low-
11
cost, and easy-to-determine, a growing number of studies have demonstrated the high
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predictive value of HGS for nutritional status and sarcopenia [3,4]. Furthermore, multiple
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studies have shown a close correlation between surgical outcomes and HGS [5,6].
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Degenerative lumbar spinal stenosis (DLSS) is a common condition in the elderly
15
population and leads to decreased physical function and impaired quality of life [7,8]. DLSS
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limits physical activity and exercise in the elderly population due to back pain, leg pain, and
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neurogenic claudication. Furthermore, this disorder is significantly associated with
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sarcopenia, which is more prevalent in patients with DLSS [9]. Both surgical and non-
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surgical approaches are used as treatment strategies for DLSS patients. Decompressive
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surgery with or without fusion is a well-established procedure for surgical intervention.
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Although many of patients experience improvements after surgery, about one-third of patients 5
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are not satisfied with their surgical outcomes [10–12]. A number of prognostic factors have
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been demonstrated to be associated with the surgical outcomes of degenerative lumbar spinal
3
stenosis [13,14].
4
However, the prognostic value of HGS for the surgical outcomes of DLSS still
5
remains unknown. We hypothesized that HGS would be a prognostic indicator for surgical
6
outcomes after spine surgery for LSS. Therefore, the purpose of this study was to investigate
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the influence of HGS on treatment outcomes after surgery for DLSS.
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Material and Method
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Study design and patients
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This was an observational study which was approved by the institutional review board of our
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hospital. A total of 190 consecutive patients who were scheduled to undergo surgery for
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DLSS between October 2016 and June 2017 were included in the study. The inclusion criteria
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were as follow: (1) patients aged 40–80 years and (2) patients who underwent surgery for
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clinical symptoms of DLSS confirmed by magnetic resonance imaging. The exclusion criteria
15
included: (1) patients with comorbidities such as severe infection or cancer that would cause
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disability, (2) patients with a history of major psychiatric disorders, (3) patients who
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underwent previous lumbar spine surgery, and (4) patients with concomitant cervical
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myeloradiculopathy or a history of trauma in the upper extremity that would worsen the
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strength status of the hands. According to these criteria, of the 190 initially included patients,
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172 were finally enrolled in the study (Figure 1).
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Measurement of HGS and group allocation 6
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HGS is one of the routine preoperative exams for patients who are scheduled to undergo
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surgery in our department. HGS was measured for the right and left hands using a hand
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dynamometer (GRIP-D5101, Takei, Niigata, Japan). The patients were asked to sit in a
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comfortable position with their elbows extended to the side and to squeeze the dynamometer
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with maximum strength. After a short break, the measurement was repeated twice for both
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hands [15]. Regardless of right or left hand, dominant hand or not, the best performance of
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these efforts was recorded and entered into the analysis. HGS has been considered as a
8
diagnostic assessment for sarcopenia, and HGS values of < 26 kg for men and < 18 kg for
9
women were used to define sarcopenia according to the guidelines set by the Asian Working
10
Group for Sarcopenia [16]. Therefore, the patients were divided into two groups, high HSG
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(≥ 26 kg for men and 18 kg for women) and low HGS (< 26 kg for men and < 18 kg for
12
women), based on the cut-off values suggested in a previous study [16].
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Surgical procedures
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One experienced orthopedic spine surgeon performed all surgical procedures. Decompressive
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surgery with or without fusion was performed for all patients. Simple decompression was the
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preferred method and was recommended for patients who did not have spondylolisthesis and
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patients who had low-grade, static spondylolisthesis. The surgeon used a unilateral approach-
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bilateral decompression technique for decompression cases. Additional fusion was performed
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if there was associated instability or a need for resection of > 50% of the facet joints due to
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foraminal decompression, foraminal stenosis, degenerative spondylolisthesis of > grade 2,
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scoliosis, or kyphosis. In fusion surgery, the surgeon routinely performed posterior interbody
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fusion technique (posterior lumbar interbody fusion or transforaminal lumbar interbody 7
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fusion) using the posterior approach.
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Surgical outcome assessment
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Patient-reported outcome (PRO) measures, including Oswestry Disability Index (ODI) [17],
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EuroQOL (EQ-5D) [18], and visual analog scale (VAS) for back and leg pain, were used to
5
assess surgical outcomes. The ODI is a self-reported questionnaire used to evaluate back-
6
specific function associated with quality of life. The questionnaire contains 10 items, each
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scored 0–5 points. The total score ranges from 0 to 50 [17]. The EQ-5D measures health-
8
related quality of life for five aspects of health, including mobility, self-care, usual activities,
9
pain/discomfort, and anxiety/decompression. EQ-5D was considered as a continuous
10
outcome and was scored as either 0 or 1, representing death and full health, respectively [18].
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The VAS was used to evaluate patients’ degree of pain in the back and legs using a 10-cm line
12
with “no pain” and “most severe pain” on each end. A mark was placed on the line by the
13
patient and the distance from the mark to zero was recorded as the VAS score. These data
14
were collected preoperatively and reassessed at 3 and 6 months after surgery. The primary
15
outcome measure was baseline-adjusted ODI score at 6 months after surgery. The secondary
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outcome measures, including the overall ODI score, EQ-5D score, and VAS score for back
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and leg pain, were assessed for superiority between the both groups during all follow-up
18
assessment.
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Statistical analysis
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All statistical analyses were performed using the Statistical Package for the Social Sciences
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(version 20.0, SPSS, Inc., Chicago, IL), except the post hoc power analysis. A p-value of <
22
0.05 was considered statistically significant. Continuous variables were expressed as means ± 8
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standard deviations. The preoperative ODI, EQ-5D, VAS for back and leg pain, and
2
demographic data were compared between the two groups using independent t-tests. One-
3
way analysis of covariance was conducted to compare the baseline-adjusted ODI scores at 6
4
months after surgery between the two groups. In addition, the change in ODI scores between
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baseline and 6 months after surgery, which was defined as the treatment effect of surgery, was
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calculated and compared between the two groups using independent t-tests. Furthermore, to
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examine the secondary outcome measures, the main effects of HGS group, post-operative
8
time, and the interaction between post-operative time and HGS group on the surgical
9
outcome measures during the follow-up period were analyzed using mixed models for
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repeated measures. In the mixed models, fixed variables included HGS group and post-
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operative time with a random factor as the subject. Given the mean difference in ODI score at
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6 months between the two groups, a post hoc power analysis was performed with an alpha
13
value of 0.05 using G*power 3.1 (Faul, Erdfelder, Lang, & Buchner, 2007).
14 15
Results
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Demographic data analysis
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Of the 172 patients enrolled in the study, 124 were placed in the high HGS group and 48 were
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placed in the low HGS group. At the final 6-month follow-up, complete surgical outcome
19
data were available for 88 and 36 patients in the high and low HGS groups, respectively. The
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proportion of patients lost to follow-up was similar between the groups (Figure 1).
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Demographic data analysis showed that there were significant differences in age (p = 0.008),
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gender (p = 0.011), and body mass index (BMI) (p = 0.014) between the two groups. The 9
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preoperative ODI in the high HGS group was significantly lower than that in the low HGS
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group (p < 0.001) and the preoperative EQ5D in the high HGS group was significantly higher
3
than that in the low HGS group (p = 0.001). There were no postoperative complications in
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any patients during the follow-up period (Table 1).
5
Surgical outcome analysis
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Three months after surgery, there were no significant differences between the groups for ODI
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score, EQ-5D score, and VAS scores for back and leg pain (p = 0.184, 0.069, 0.722, and
8
0.629, respectively). Six months after surgery, the mean ODI score was significantly lower in
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the high HGS group (p = 0.012) and the mean EQ5D was significantly higher in the high
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HGS group (p = 0.039). VAS scores for back and leg pain at 6 months after surgery did not
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significantly differ between the two groups (p = 0.681 and 0.483, respectively) (Table 2).
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There was a significant difference between the groups in terms of the primary
13
outcome measure, baseline-adjusted ODI scores at 6 months after surgery, when controlling
14
for age, gender, and BMI (F [1,116] = 5.498, p = 0.021). The post hot power analysis
15
confirmed the difference in mean and standard deviation in the ODI score at 6 months with
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an alpha value of 0.05 and a statistical power of 77.1%.The surgical treatment effects in the
17
high HGS group and low HGS group (standard deviation) were 6.1 (7.7) and 5.1 (8.9),
18
respectively, and there was no difference between the two groups (p = 0.554).
19
In terms of secondary outcome measurements, the main effects in HGS group on the
20
overall changes in the ODI and EQ-5D during the 6-month period were significantly different
21
between the two groups (p < 0.001 and p < 0.001, respectively), while they were not 10
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significantly different for the overall changes in VAS for back and leg pain between the two
2
groups (p = 0.724 and 0.253, respectively). The effects of post-operative time on the overall
3
`changes in ODI, EQ-5D, and VAS for back and leg pain were significant in both groups (p <
4
0.001 for all four variables), suggesting that all four surgical outcomes improved significantly
5
with time after surgery in both groups. Moreover, the effect of interactions between HGS
6
group and follow-up assessment time on ODI was significant (p = 0.039), meaning that the
7
patterns of changes in ODI during the follow-up period were significantly different between
8
the two groups (Figure 2). The effects of the interaction between HGS group and follow-up
9
assessment time on EQ-5D scores and VAS for back and leg pain were not significant (p =
10
0.575, 0.733, and 0.927, respectively) (Figures 3, 4, 5).
11 12
Discussion
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In this observational study, we found that preoperative HGS was significantly related to
14
postoperative functional outcomes and health status in terms of ODI and EQ5D 6months after
15
surgery. Therefore, this study demonstrated that HGS is a simple and useful tool for assessing
16
preoperative functional status and predicting surgical outcomes in patients with DLSS.
17
The surgical outcomes in our study including ODI, EQ5D, and VAS for back and leg
18
pain improved significantly in the two groups over 6 months following surgery. This result
19
suggests that the surgical procedure is an effective treatment in patients with DLSS regardless
20
of their functional and disability status. We also found that there were differences in surgical
21
outcomes between the two groups: high preoperative HGS was associated with better surgical
22
functional outcomes over a 6-month follow-up period. At 3 months after surgery, the ODI and 11
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EQ-5D scores showed significant improvements in both groups, however, at the final 6-
2
month follow-up, the ODI and EQ-5D scores remained the same level in the high HGS group
3
but worsened in the low HGS group. Although both groups exhibited significant
4
improvements from baseline, there were significant differences of ODI and EQ-5D scores
5
between the two groups at the final follow-up assessment. Thus, the surgical outcomes for
6
disability and health-related quality of life in the high HGS group were superior to those in
7
the low HGS group. This result is similar to those of previous studies evaluating the
8
correlation between HGS and surgical outcomes in hip fracture and esophageal cancer
9
surgery, in which high HGS also indicated better surgical outcomes [5,6].
10
Based on the present results, HGS is of high predictive value for spinal surgery
11
outcomes in terms of functional and health status in patients with DLSS. The significant
12
differences of preoperative ODI and EQ5D scores between the two are explained by the fact
13
that HGS represents physical disability and health-related quality of life in these patients.
14
Thus, HGS can be used to assess patients’ preoperative functional status, which can be a
15
valuable predictor of a favorable surgical outcome. From the results of the demographic
16
analysis, we found that age, gender ratio, and BMI were significantly different between the
17
high and low HGS groups. This can be explained by previous studies that HGS is influenced
18
by muscular and extramuscular factors such as age, gender, genetic features, comorbidities,
19
physical activity, and environmental factors [19–21]. The ODI score at 6 months after surgery,
20
which was a primary outcome of our study, was significantly different between the two
21
groups, even after adjustment for age, gender, and BMI. This means that the effect of HGS on
22
ODI score is considerable, implying independent association between HGS and surgical
23
functional outcomes in terms of ODI. Furthermore, the significant main effects of HGS group 12
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on ODI and EQ-5D scores during the 6-month follow-up period indicate that HGS has
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considerable influence on patients’ functional and health status after spinal surgery. Therefore,
3
HGS can be used to predict surgical functional outcomes. Moreover, HGS is an objective and
4
reproducible parameter that is simple and less time and money-consuming. Therefore, HGS is
5
a simple and reliable tool for assessing preoperative functional status and predicting spinal
6
surgery outcomes in patients with DLSS.
7
However, our study revealed different results when considering the surgical
8
outcomes in terms of VAS for back and leg pain. There were no significant differences
9
between two groups in VAS for back and leg pain at any assessment time point following
10
surgery. This means that surgical outcomes for back and leg pain symptoms in the high HGS
11
group were equal to those in the low HGS group. This result suggests that HSG is not related
12
to subjective feelings of pain, even though it is a useful marker for assessing a patient’s
13
physiologic and functional status. The fact that preoperative VAS scores for back and leg pain
14
were not different between the groups is in line with this result.
15
HGS has been well established to shave high predictive value for outcomes of
16
orthopedic and thoracic surgery [5,6], and is highly correlated with postoperative
17
complications, length of hospital stay, and readmission rate [22,23]. However, the biological
18
mechanism through which HGS influences health status is not completely known. Previous
19
studies have demonstrated that grip strength is correlated with the strength of other muscle
20
groups19 and can be used as an indicator of neuromuscular status and functional reserve [24].
21
According to the results of our study, ODI score and EQ5D score were significantly different
22
between the two groups preoperatively, indicating significantly higher levels of functional 13
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and health status in the high HGS compared to the low HGS group, in agreement with the
2
results of previous studies. In addition, HGS was a strong marker of nutritional status and
3
sarcopenia [3,4]. Therefore, patients with low HGS may present with poor nutritional status
4
and reduced muscle mass and strength associated with loss of physical functionality, which
5
can lead to poor recovery from illness or surgery. This may explain why the high HGS group
6
was superior to the low HGS group in terms of surgical functional outcomes.
7
There are several limitations to this study that should be discussed. First, this study
8
was of relatively small sample size in the low HGS group and a short follow-up period of 6
9
months. To better establish the predictive value of HGS for DLSS, further studies with larger
10
sample sizes and longer follow-up periods are needed. Based on the present results, we plan
11
consecutive long-term follow-up study. Second, the cut off value of HGS used to divide
12
patients into groups was based on a previous study of sarcopenia. Therefore, this value does
13
not likely represent favorable surgical outcomes. Third, even though post-hoc power for the
14
primary outcome measure was 77.1%, this study was of relatively high loss to follow up rate
15
at 6 months in both groups. The relatively incomplete study data may put a bias on the result
16
of the study potentially. Finally, although all surgeries were performed by one orthopedic
17
spinal surgeon, the difference in surgical techniques and procedures for decompressive and
18
fusion surgery may have introduced performance bias.
19
In conclusion, despite the small effect on back and leg pain, HGS can influence
20
surgical outcomes in terms of disability and health status in patients with DLSS 6 months
21
after surgery. This 6-month study of results following spinal surgery showed that preoperative
22
HGS can act as a predictor of surgical outcomes in patients with DLSS. 14
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Figure captions
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Fig. 1. Flow diagram of enrollment, allocation and follow-up of the study participants.
9 10
Fig. 2. Overall change of ODI at follow-up assessments (3 and 6 months after surgery).
11
*Significant difference between both HGS groups. The effect of HGS group, post-operative
12
time, and the interaction between post-operative time and HGS group on the Overall change
13
of ODI (p < 0.001, p < 0.001, and p = 0.039, respectively).
14 15
Fig. 3. Overall change of EQ-5D at follow-up assessments (3 and 6 months after surgery).
16
*Significant difference between both HGS groups. The effect of HGS group, post-operative
17
time, and the interaction between post-operative time and HGS group on the Overall change
18
of EQ-5D (p < 0.001, p < 0.001, and p = 0.575, respectively).
19
18
Page 18 of 26
1
Fig. 4. Overall change of VAS for back pain at follow-up assessments (3 and 6 months after
2
surgery). The effect of HGS group, post-operative time, and the interaction between post-
3
operative time and HGS group on the Overall change of VAS for back pain (p = 0.724, p < 0.001,
4
and p = 0.733, respectively).
5 6
Fig. 5. Overall change of VAS for leg pain at follow-up assessments (3 and 6 months after
7
surgery). The effect of HGS group, post-operative time, and the interaction between post-
8
operative time and HGS group on the Overall change of VAS for leg pain (p = 0.253, p < 0.001,
9
and p = 0.927, respectively).
10 11
19
Page 19 of 26
1 2
Table 1. Descriptive statistics of the patients in the study. Values are mean and standard deviation. High HGS group (n = 124) Low HGS group (n = 48) Age (yrs)
p-value
68.1±9.2
72.3±6.6
0.008
Female, n (%)
61 (49.2%)
34 (70.8%)
0.011
BMI (kg/m2)
25.89±3.57
24.40±3.40
0.014
19.8±7.7
24.7±7.9
<0.001
0.391±0.259
0.237±0.287
0.001
VAS for back pain
5.6±2.4
5.9±2.6
0.501
VAS for leg pain
6.4±2.3
6.7±2.3
0.497
ODI EQ5D
Surgical treatment
0.233
Fusion (n)
65
30
Decompression (n)
59
18
3
HGS: hand grip strength; BMI: body mass indext; ODI: Oswestry Disability Index, Cut-
4
off value of hand grip strength: <26 kg for men and <18 kg for women; VAS: visual
5
analogue scale
6
20
Page 20 of 26
1
Table 2. Comparison of surgical outcomes between High HGS and Low HGS
2
groups at 3 months and 6 months. Values are mean and standard deviation.
3 Postoperative follow-up
High HGS group (n = 1 Low HGS group (n = 17) 42) p-value ODI
14.6±7.9
16.6±8.9
0.184
EQ-5D
0.599±0.208
0.517±0.304
0.069
VAS for back pain
4.2±2.6
4.0±2.5
0.722
VAS for leg pain
3.4±2.7
3.7±2.8
0.629
ODI
14.7±8.2
19.1±10.0
0.012
EQ5D)
0.578±0.272
0.459±0.317
0.039
VAS for back pain
4.6±2.8
4.8±3.4
0.681
VAS for leg pain
4.5±3.2
4.9±3.5
0.483
3 months
6 months
4 5 6 7
HGS: hand grip strength; ODI: Oswestry Disability Index; VAS: visual analogue scale
8 9 10
21
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S1529-9430(18)30163-3 https://doi.org/10.1016/j.spinee.2018.04.009 SPINEE 57650
To appear in:
The Spine Journal
Received date: Revised date: Accepted date:
21-1-2018 23-3-2018 9-4-2018
Please cite this article as: Feng Shen, Ho-Joong Kim, Na-Kyoung Lee, Heoung-Jae Chun, BongSoon Chang, Choon-Ki Lee, Jin S. Yeom, The influence of hand grip strength on surgical outcomes after surgery for degenerative lumbar spinal stenosis: a preliminary result, The Spine Journal (2018), https://doi.org/10.1016/j.spinee.2018.04.009. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
1
The influence of hand grip strength on surgical outcomes after surgery for degenerative
2
lumbar spinal stenosis: a preliminary result
3 4 5
Feng Shen, MDa, Ho-Joong Kim, MDa,*, Na-Kyoung Lee, MDa, Heoung-Jae Chun, PhDc, Bong-Soon Chang, MDb, Choon-Ki Lee, MDb, Jin S. Yeom, MDa
6 7
a
8
Medicine and Seoul National University Bundang Hospital, 166 Gumiro, Bundang-gu,
9
Sungnam 463-707, Republic of Korea
Spine Center and Department of Orthopedic Surgery, Seoul National University College of
10
b
11
Seoul National University Hospital, 101 Daehangno, Jongno-gu, Seoul 110-744, Republic of
12
Korea
13
c
14
Republic of Korea
Department of Orthopaedic Surgery, Seoul National University College of Medicine and
Department of Mechanical Engineering, Yonsei University, Seodaemun-gu, Seoul, 03722,
15 16
Acknowledgement:
17
This research was supported by Basic Science Research Program through the National
18
Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and
19
Technology (2016R1A2B3012850).
20 21 1
Page 1 of 26
1 2
Address correspondence and reprint requests to:
3
Ho-Joong Kim, MD
4
Spine Center and Department of Orthopaedic Surgery,
5
Seoul National University College of Medicine and Seoul National University Bundang
6
Hospital, 166 Gumiro, Bundang-gu, Sungnam 463-707, Republic of Korea
7
Tel: +82317877202
8
E-mail: [email protected]
9 10 11 12 13 14 15 16 17 18 19 2
Page 2 of 26
1 2 3 4 5
Abstract
6
Background Context: Although a number of prognostic factors have been demonstrated to
7
be associated with surgical outcome of degenerative lumbar spinal stenosis (DLSS), no study
8
has investigated the relation between hand grip strength (HGS) and treatment outcome of
9
DLSS.
10
Purpose: The purpose of this study was to examine the influence of HGS on surgical
11
outcomes after surgery for patients with DLSS.
12
Study design: An observational study
13
Patient Sample: Patients who underwent spine surgery for DLSS.
14
Outcome Measures: Oswestry Disability Index (ODI), EuroQOL (EQ-5D), and visual
15
analog scale (VAS) for back/ leg pain.
16
Methods: A total of 172 consecutive patients who underwent spine surgery for DLSS were
17
included in this study. Patients were assigned to either a high HGS ( 26 kg for men and
18
kg for women, n=124) or low HGS group (< 26 kg for men and < 18 kg for women, n=48)
19
based on their preoperative HGS performance. ODI, EQ-5D, VAS for back and leg pain were
20
assessed and compared between two groups preoperatively, 3 and 6 months after surgery. The
18
3
Page 3 of 26
1
primary outcome measure was baseline-adjusted ODI scores 6 months after surgery. The
2
secondary outcome measures, including the overall ODI score, EQ-5D score, VAS score for
3
back and leg pain, were assessed at each time point during the 6 months follow-up period.
4
Results: As primary outcome, baseline-adjusted ODI scores was significant lower in high
5
HGS group than it in low HGS group 6 months after surgery. In the secondary outcome
6
measurements, the ODI, EQ-5D, VAS score for back and leg pain improved significantly
7
with time after surgery in both groups. The effects of HGS group on the overall changes in
8
the ODI and EQ-5D during the 6months period were significantly different between the two
9
groups, however, they were not significantly different on VAS for back and leg pain. The
10
pattern of change in the ODI during the follow-up period was significantly different betwee
11
n the two groups.
12
Conclusions: Patients with preoperative high HGS display better surgical outcome in terms
13
of disability and health status 6 months after spine surgery. Preoperative HGS can act as a
14
predictor of surgical outcome in spine surgery in patients with DLSS.
15
Keywords: hand grip strength; degenerative change; lumbar spinal stenosis; spine surgery;
16
surgical outcomes; predictor
17 18 19 20
4
Page 4 of 26
1 2 3 4 5
Introduction
6
Previous study has suggested that performance-based functional assessment could provide
7
important prognostic information concerning acute or chronic diseases [1]. As a performance-
8
based functional assessment method, muscle strength is associated with physical functionality
9
and nutritional status [2]. Hand grip strength (HGS), a measure of voluntary muscle function,
10
has often been used as an indicator of muscle strength. Regarding it as simple, quick, low-
11
cost, and easy-to-determine, a growing number of studies have demonstrated the high
12
predictive value of HGS for nutritional status and sarcopenia [3,4]. Furthermore, multiple
13
studies have shown a close correlation between surgical outcomes and HGS [5,6].
14
Degenerative lumbar spinal stenosis (DLSS) is a common condition in the elderly
15
population and leads to decreased physical function and impaired quality of life [7,8]. DLSS
16
limits physical activity and exercise in the elderly population due to back pain, leg pain, and
17
neurogenic claudication. Furthermore, this disorder is significantly associated with
18
sarcopenia, which is more prevalent in patients with DLSS [9]. Both surgical and non-
19
surgical approaches are used as treatment strategies for DLSS patients. Decompressive
20
surgery with or without fusion is a well-established procedure for surgical intervention.
21
Although many of patients experience improvements after surgery, about one-third of patients 5
Page 5 of 26
1
are not satisfied with their surgical outcomes [10–12]. A number of prognostic factors have
2
been demonstrated to be associated with the surgical outcomes of degenerative lumbar spinal
3
stenosis [13,14].
4
However, the prognostic value of HGS for the surgical outcomes of DLSS still
5
remains unknown. We hypothesized that HGS would be a prognostic indicator for surgical
6
outcomes after spine surgery for LSS. Therefore, the purpose of this study was to investigate
7
the influence of HGS on treatment outcomes after surgery for DLSS.
8
Material and Method
9
Study design and patients
10
This was an observational study which was approved by the institutional review board of our
11
hospital. A total of 190 consecutive patients who were scheduled to undergo surgery for
12
DLSS between October 2016 and June 2017 were included in the study. The inclusion criteria
13
were as follow: (1) patients aged 40–80 years and (2) patients who underwent surgery for
14
clinical symptoms of DLSS confirmed by magnetic resonance imaging. The exclusion criteria
15
included: (1) patients with comorbidities such as severe infection or cancer that would cause
16
disability, (2) patients with a history of major psychiatric disorders, (3) patients who
17
underwent previous lumbar spine surgery, and (4) patients with concomitant cervical
18
myeloradiculopathy or a history of trauma in the upper extremity that would worsen the
19
strength status of the hands. According to these criteria, of the 190 initially included patients,
20
172 were finally enrolled in the study (Figure 1).
21
Measurement of HGS and group allocation 6
Page 6 of 26
1
HGS is one of the routine preoperative exams for patients who are scheduled to undergo
2
surgery in our department. HGS was measured for the right and left hands using a hand
3
dynamometer (GRIP-D5101, Takei, Niigata, Japan). The patients were asked to sit in a
4
comfortable position with their elbows extended to the side and to squeeze the dynamometer
5
with maximum strength. After a short break, the measurement was repeated twice for both
6
hands [15]. Regardless of right or left hand, dominant hand or not, the best performance of
7
these efforts was recorded and entered into the analysis. HGS has been considered as a
8
diagnostic assessment for sarcopenia, and HGS values of < 26 kg for men and < 18 kg for
9
women were used to define sarcopenia according to the guidelines set by the Asian Working
10
Group for Sarcopenia [16]. Therefore, the patients were divided into two groups, high HSG
11
(≥ 26 kg for men and 18 kg for women) and low HGS (< 26 kg for men and < 18 kg for
12
women), based on the cut-off values suggested in a previous study [16].
13
Surgical procedures
14
One experienced orthopedic spine surgeon performed all surgical procedures. Decompressive
15
surgery with or without fusion was performed for all patients. Simple decompression was the
16
preferred method and was recommended for patients who did not have spondylolisthesis and
17
patients who had low-grade, static spondylolisthesis. The surgeon used a unilateral approach-
18
bilateral decompression technique for decompression cases. Additional fusion was performed
19
if there was associated instability or a need for resection of > 50% of the facet joints due to
20
foraminal decompression, foraminal stenosis, degenerative spondylolisthesis of > grade 2,
21
scoliosis, or kyphosis. In fusion surgery, the surgeon routinely performed posterior interbody
22
fusion technique (posterior lumbar interbody fusion or transforaminal lumbar interbody 7
Page 7 of 26
1
fusion) using the posterior approach.
2
Surgical outcome assessment
3
Patient-reported outcome (PRO) measures, including Oswestry Disability Index (ODI) [17],
4
EuroQOL (EQ-5D) [18], and visual analog scale (VAS) for back and leg pain, were used to
5
assess surgical outcomes. The ODI is a self-reported questionnaire used to evaluate back-
6
specific function associated with quality of life. The questionnaire contains 10 items, each
7
scored 0–5 points. The total score ranges from 0 to 50 [17]. The EQ-5D measures health-
8
related quality of life for five aspects of health, including mobility, self-care, usual activities,
9
pain/discomfort, and anxiety/decompression. EQ-5D was considered as a continuous
10
outcome and was scored as either 0 or 1, representing death and full health, respectively [18].
11
The VAS was used to evaluate patients’ degree of pain in the back and legs using a 10-cm line
12
with “no pain” and “most severe pain” on each end. A mark was placed on the line by the
13
patient and the distance from the mark to zero was recorded as the VAS score. These data
14
were collected preoperatively and reassessed at 3 and 6 months after surgery. The primary
15
outcome measure was baseline-adjusted ODI score at 6 months after surgery. The secondary
16
outcome measures, including the overall ODI score, EQ-5D score, and VAS score for back
17
and leg pain, were assessed for superiority between the both groups during all follow-up
18
assessment.
19
Statistical analysis
20
All statistical analyses were performed using the Statistical Package for the Social Sciences
21
(version 20.0, SPSS, Inc., Chicago, IL), except the post hoc power analysis. A p-value of <
22
0.05 was considered statistically significant. Continuous variables were expressed as means ± 8
Page 8 of 26
1
standard deviations. The preoperative ODI, EQ-5D, VAS for back and leg pain, and
2
demographic data were compared between the two groups using independent t-tests. One-
3
way analysis of covariance was conducted to compare the baseline-adjusted ODI scores at 6
4
months after surgery between the two groups. In addition, the change in ODI scores between
5
baseline and 6 months after surgery, which was defined as the treatment effect of surgery, was
6
calculated and compared between the two groups using independent t-tests. Furthermore, to
7
examine the secondary outcome measures, the main effects of HGS group, post-operative
8
time, and the interaction between post-operative time and HGS group on the surgical
9
outcome measures during the follow-up period were analyzed using mixed models for
10
repeated measures. In the mixed models, fixed variables included HGS group and post-
11
operative time with a random factor as the subject. Given the mean difference in ODI score at
12
6 months between the two groups, a post hoc power analysis was performed with an alpha
13
value of 0.05 using G*power 3.1 (Faul, Erdfelder, Lang, & Buchner, 2007).
14 15
Results
16
Demographic data analysis
17
Of the 172 patients enrolled in the study, 124 were placed in the high HGS group and 48 were
18
placed in the low HGS group. At the final 6-month follow-up, complete surgical outcome
19
data were available for 88 and 36 patients in the high and low HGS groups, respectively. The
20
proportion of patients lost to follow-up was similar between the groups (Figure 1).
21
Demographic data analysis showed that there were significant differences in age (p = 0.008),
22
gender (p = 0.011), and body mass index (BMI) (p = 0.014) between the two groups. The 9
Page 9 of 26
1
preoperative ODI in the high HGS group was significantly lower than that in the low HGS
2
group (p < 0.001) and the preoperative EQ5D in the high HGS group was significantly higher
3
than that in the low HGS group (p = 0.001). There were no postoperative complications in
4
any patients during the follow-up period (Table 1).
5
Surgical outcome analysis
6
Three months after surgery, there were no significant differences between the groups for ODI
7
score, EQ-5D score, and VAS scores for back and leg pain (p = 0.184, 0.069, 0.722, and
8
0.629, respectively). Six months after surgery, the mean ODI score was significantly lower in
9
the high HGS group (p = 0.012) and the mean EQ5D was significantly higher in the high
10
HGS group (p = 0.039). VAS scores for back and leg pain at 6 months after surgery did not
11
significantly differ between the two groups (p = 0.681 and 0.483, respectively) (Table 2).
12
There was a significant difference between the groups in terms of the primary
13
outcome measure, baseline-adjusted ODI scores at 6 months after surgery, when controlling
14
for age, gender, and BMI (F [1,116] = 5.498, p = 0.021). The post hot power analysis
15
confirmed the difference in mean and standard deviation in the ODI score at 6 months with
16
an alpha value of 0.05 and a statistical power of 77.1%.The surgical treatment effects in the
17
high HGS group and low HGS group (standard deviation) were 6.1 (7.7) and 5.1 (8.9),
18
respectively, and there was no difference between the two groups (p = 0.554).
19
In terms of secondary outcome measurements, the main effects in HGS group on the
20
overall changes in the ODI and EQ-5D during the 6-month period were significantly different
21
between the two groups (p < 0.001 and p < 0.001, respectively), while they were not 10
Page 10 of 26
1
significantly different for the overall changes in VAS for back and leg pain between the two
2
groups (p = 0.724 and 0.253, respectively). The effects of post-operative time on the overall
3
`changes in ODI, EQ-5D, and VAS for back and leg pain were significant in both groups (p <
4
0.001 for all four variables), suggesting that all four surgical outcomes improved significantly
5
with time after surgery in both groups. Moreover, the effect of interactions between HGS
6
group and follow-up assessment time on ODI was significant (p = 0.039), meaning that the
7
patterns of changes in ODI during the follow-up period were significantly different between
8
the two groups (Figure 2). The effects of the interaction between HGS group and follow-up
9
assessment time on EQ-5D scores and VAS for back and leg pain were not significant (p =
10
0.575, 0.733, and 0.927, respectively) (Figures 3, 4, 5).
11 12
Discussion
13
In this observational study, we found that preoperative HGS was significantly related to
14
postoperative functional outcomes and health status in terms of ODI and EQ5D 6months after
15
surgery. Therefore, this study demonstrated that HGS is a simple and useful tool for assessing
16
preoperative functional status and predicting surgical outcomes in patients with DLSS.
17
The surgical outcomes in our study including ODI, EQ5D, and VAS for back and leg
18
pain improved significantly in the two groups over 6 months following surgery. This result
19
suggests that the surgical procedure is an effective treatment in patients with DLSS regardless
20
of their functional and disability status. We also found that there were differences in surgical
21
outcomes between the two groups: high preoperative HGS was associated with better surgical
22
functional outcomes over a 6-month follow-up period. At 3 months after surgery, the ODI and 11
Page 11 of 26
1
EQ-5D scores showed significant improvements in both groups, however, at the final 6-
2
month follow-up, the ODI and EQ-5D scores remained the same level in the high HGS group
3
but worsened in the low HGS group. Although both groups exhibited significant
4
improvements from baseline, there were significant differences of ODI and EQ-5D scores
5
between the two groups at the final follow-up assessment. Thus, the surgical outcomes for
6
disability and health-related quality of life in the high HGS group were superior to those in
7
the low HGS group. This result is similar to those of previous studies evaluating the
8
correlation between HGS and surgical outcomes in hip fracture and esophageal cancer
9
surgery, in which high HGS also indicated better surgical outcomes [5,6].
10
Based on the present results, HGS is of high predictive value for spinal surgery
11
outcomes in terms of functional and health status in patients with DLSS. The significant
12
differences of preoperative ODI and EQ5D scores between the two are explained by the fact
13
that HGS represents physical disability and health-related quality of life in these patients.
14
Thus, HGS can be used to assess patients’ preoperative functional status, which can be a
15
valuable predictor of a favorable surgical outcome. From the results of the demographic
16
analysis, we found that age, gender ratio, and BMI were significantly different between the
17
high and low HGS groups. This can be explained by previous studies that HGS is influenced
18
by muscular and extramuscular factors such as age, gender, genetic features, comorbidities,
19
physical activity, and environmental factors [19–21]. The ODI score at 6 months after surgery,
20
which was a primary outcome of our study, was significantly different between the two
21
groups, even after adjustment for age, gender, and BMI. This means that the effect of HGS on
22
ODI score is considerable, implying independent association between HGS and surgical
23
functional outcomes in terms of ODI. Furthermore, the significant main effects of HGS group 12
Page 12 of 26
1
on ODI and EQ-5D scores during the 6-month follow-up period indicate that HGS has
2
considerable influence on patients’ functional and health status after spinal surgery. Therefore,
3
HGS can be used to predict surgical functional outcomes. Moreover, HGS is an objective and
4
reproducible parameter that is simple and less time and money-consuming. Therefore, HGS is
5
a simple and reliable tool for assessing preoperative functional status and predicting spinal
6
surgery outcomes in patients with DLSS.
7
However, our study revealed different results when considering the surgical
8
outcomes in terms of VAS for back and leg pain. There were no significant differences
9
between two groups in VAS for back and leg pain at any assessment time point following
10
surgery. This means that surgical outcomes for back and leg pain symptoms in the high HGS
11
group were equal to those in the low HGS group. This result suggests that HSG is not related
12
to subjective feelings of pain, even though it is a useful marker for assessing a patient’s
13
physiologic and functional status. The fact that preoperative VAS scores for back and leg pain
14
were not different between the groups is in line with this result.
15
HGS has been well established to shave high predictive value for outcomes of
16
orthopedic and thoracic surgery [5,6], and is highly correlated with postoperative
17
complications, length of hospital stay, and readmission rate [22,23]. However, the biological
18
mechanism through which HGS influences health status is not completely known. Previous
19
studies have demonstrated that grip strength is correlated with the strength of other muscle
20
groups19 and can be used as an indicator of neuromuscular status and functional reserve [24].
21
According to the results of our study, ODI score and EQ5D score were significantly different
22
between the two groups preoperatively, indicating significantly higher levels of functional 13
Page 13 of 26
1
and health status in the high HGS compared to the low HGS group, in agreement with the
2
results of previous studies. In addition, HGS was a strong marker of nutritional status and
3
sarcopenia [3,4]. Therefore, patients with low HGS may present with poor nutritional status
4
and reduced muscle mass and strength associated with loss of physical functionality, which
5
can lead to poor recovery from illness or surgery. This may explain why the high HGS group
6
was superior to the low HGS group in terms of surgical functional outcomes.
7
There are several limitations to this study that should be discussed. First, this study
8
was of relatively small sample size in the low HGS group and a short follow-up period of 6
9
months. To better establish the predictive value of HGS for DLSS, further studies with larger
10
sample sizes and longer follow-up periods are needed. Based on the present results, we plan
11
consecutive long-term follow-up study. Second, the cut off value of HGS used to divide
12
patients into groups was based on a previous study of sarcopenia. Therefore, this value does
13
not likely represent favorable surgical outcomes. Third, even though post-hoc power for the
14
primary outcome measure was 77.1%, this study was of relatively high loss to follow up rate
15
at 6 months in both groups. The relatively incomplete study data may put a bias on the result
16
of the study potentially. Finally, although all surgeries were performed by one orthopedic
17
spinal surgeon, the difference in surgical techniques and procedures for decompressive and
18
fusion surgery may have introduced performance bias.
19
In conclusion, despite the small effect on back and leg pain, HGS can influence
20
surgical outcomes in terms of disability and health status in patients with DLSS 6 months
21
after surgery. This 6-month study of results following spinal surgery showed that preoperative
22
HGS can act as a predictor of surgical outcomes in patients with DLSS. 14
Page 14 of 26
1 2 3 4 5 6 7
References
8
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based functional assessment in older hospitalized patients: feasibility and clinical
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correlates. J Gerontol A Biol Sci Med Sci 2008;63:1393–8. [2]
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Volpato S, Cavalieri M, Guerra G, Sioulis F, Ranzini M, Maraldi C, et al. Performance-
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[3]
Norman K, Stobäus N, Gonzalez MC, Schulzke JD, Pirlich M. Hand grip strength: outcome predictor and marker of nutritional status. Clin Nutr 2011;30:135–42.
[4] Cruz-Jentoft AJ, Baeyens JP, Bauer JM, Boirie Y, Cederholm T, Landi F, et al.
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[5] Savino E, Martini E, Lauretani F, Pioli G, Zagatti AM, Frondini C, et al. Hand grip
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[6] Chen CH, Ho-Chang , Huang YZ, Hung TT. Hand grip strength is a simple and
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[7]
Kim HJ, Lee KW, Cho HG, Kang KT, Chang BS, Lee CK, et al. Indirect effects of
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mellitus and lumbar spinal stenosis. Spine J 2015;15:25–33.
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[8]
Kim HJ, Lee HM, Kim HS, Park JO, Moon ES, Park H, et al. Bone metabolism in
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[24] Lauretani F, Russo CR, Bandinelli S, Bartali B, Cavazzini C, Di Iorio A, et al. Age-
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diagnosis of sarcopenia. J Appl Physiol (1985) 2003;95:1851–60.
4 5 6 7
Figure captions
8
Fig. 1. Flow diagram of enrollment, allocation and follow-up of the study participants.
9 10
Fig. 2. Overall change of ODI at follow-up assessments (3 and 6 months after surgery).
11
*Significant difference between both HGS groups. The effect of HGS group, post-operative
12
time, and the interaction between post-operative time and HGS group on the Overall change
13
of ODI (p < 0.001, p < 0.001, and p = 0.039, respectively).
14 15
Fig. 3. Overall change of EQ-5D at follow-up assessments (3 and 6 months after surgery).
16
*Significant difference between both HGS groups. The effect of HGS group, post-operative
17
time, and the interaction between post-operative time and HGS group on the Overall change
18
of EQ-5D (p < 0.001, p < 0.001, and p = 0.575, respectively).
19
18
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Fig. 4. Overall change of VAS for back pain at follow-up assessments (3 and 6 months after
2
surgery). The effect of HGS group, post-operative time, and the interaction between post-
3
operative time and HGS group on the Overall change of VAS for back pain (p = 0.724, p < 0.001,
4
and p = 0.733, respectively).
5 6
Fig. 5. Overall change of VAS for leg pain at follow-up assessments (3 and 6 months after
7
surgery). The effect of HGS group, post-operative time, and the interaction between post-
8
operative time and HGS group on the Overall change of VAS for leg pain (p = 0.253, p < 0.001,
9
and p = 0.927, respectively).
10 11
19
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1 2
Table 1. Descriptive statistics of the patients in the study. Values are mean and standard deviation. High HGS group (n = 124) Low HGS group (n = 48) Age (yrs)
p-value
68.1±9.2
72.3±6.6
0.008
Female, n (%)
61 (49.2%)
34 (70.8%)
0.011
BMI (kg/m2)
25.89±3.57
24.40±3.40
0.014
19.8±7.7
24.7±7.9
<0.001
0.391±0.259
0.237±0.287
0.001
VAS for back pain
5.6±2.4
5.9±2.6
0.501
VAS for leg pain
6.4±2.3
6.7±2.3
0.497
ODI EQ5D
Surgical treatment
0.233
Fusion (n)
65
30
Decompression (n)
59
18
3
HGS: hand grip strength; BMI: body mass indext; ODI: Oswestry Disability Index, Cut-
4
off value of hand grip strength: <26 kg for men and <18 kg for women; VAS: visual
5
analogue scale
6
20
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1
Table 2. Comparison of surgical outcomes between High HGS and Low HGS
2
groups at 3 months and 6 months. Values are mean and standard deviation.
3 Postoperative follow-up
High HGS group (n = 1 Low HGS group (n = 17) 42) p-value ODI
14.6±7.9
16.6±8.9
0.184
EQ-5D
0.599±0.208
0.517±0.304
0.069
VAS for back pain
4.2±2.6
4.0±2.5
0.722
VAS for leg pain
3.4±2.7
3.7±2.8
0.629
ODI
14.7±8.2
19.1±10.0
0.012
EQ5D)
0.578±0.272
0.459±0.317
0.039
VAS for back pain
4.6±2.8
4.8±3.4
0.681
VAS for leg pain
4.5±3.2
4.9±3.5
0.483
3 months
6 months
4 5 6 7
HGS: hand grip strength; ODI: Oswestry Disability Index; VAS: visual analogue scale
8 9 10
21
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