Postural stability,fall risk and sensory integration of balance in discogenic low back pain

Abstract

BACKGROUND:

Even though studies have reported impaired postural stability (PS) and risk of fall in non-specific low back pain (LBP), evidence is relatively scarce in terms of discogenic LBP or in persons with degenerative disc disorders of the lumbar spine.

OBJECTIVE:

To determine the differences in terms of PS, fall risk and sensory integration of balance in persons with discogenic LBP as compared to healthy controls.

METHODS:

A cross sectional comparative study was conducted on 60 participants, out of which 30 had discogenic LBP and 30 were healthy controls. The variables of interest included PS, fall risk score (FRS) and clinical test of sensory integration of balance (CTSIB), and the data was collected using Biodex Balance System^TM SD, with higher scores signifying poorer outcomes.

RESULTS:

Persons with discogenic LBP scored significantly (p < 0.05) higher in terms of overall PS index [Mean difference = 2.33 (95% CI 1.38, 3.28)], anteroposterior PS index [Mean difference = 1.87 (95% CI 0.84, 2.90)] and mediolateral PS index [Mean difference = 0.82 (95% CI 0.43, 1.21)], FRS [Mean difference = 2.92 (95% CI 2.36, 4.8)] and CTSIB [Mean difference = 1.67 (95% CI 1.28, 2.06)] as compared to healthy controls. Both healthy controls and persons with discogenic LBP revealed higher anteroposterior postural stability index as compared to mediolateral postural stability index (p < 0.001).

CONCLUSIONS:

Persons with discogenic low back pain exhibit greater risk of fall and poorer postural stability and sensory integration of balance as compared to healthy controls. It is suggested that fall risk, postural stability and sensory integration of balance should be considered as outcome measures in clinical management of such patients.

Keywords

Balance disc prolapse fall risk low back pain postural control postural stability

1 Introduction

Low back pain is a major cause of global disability [1] with lifelong incidence of 58–84% [2], and lumbar radiculopathy or sciatica is one of the most common variants of low back pain, with a prevalence of 1.2–43% [3]. Sources of lumbar radiculopathy or sciatica include lumbar spinal canal stenosis, foraminal stenosis and intervertebral disc herniation [3]. Lumbar disc herniation is the most common cause of lumbar surgery in employment age persons, and individuals with factors such as diabetes, hyperlipidemia, smoking, obesity, positive family history for disc disease, being involved in physically challenging jobs and significant time spent in driving are at a greater risk of developing lumbar disc herniation [4]. The prevalence of disc related sciatica is observed to be as high as 2.2% [5], and lumbar disc disorders and discogenic low back pain can also lead to impairments in postural stability [6]. Visual compensation mechanisms have been observed for underlying sensory motor impairments in persons with lumbar disc herniation [6] and persons with discogenic low back pain have demonstrated an increase in medio-lateral sway on the involved leg especially during narrow base of support conditions [6]. Similar findings have also been reported in individuals with nonspecific low back pain with impaired postural control and increased oscillation of center of pressure as compared to healthy controls, which are further amplified by visual deprivation and unstable surface conditions [7]. Research has also shown older men and women with low back pain to have increased risk of fall [8 –10], and no gender based differences have been observed in terms of static and dynamic postural control in persons with nonspecific low back pain [11]. On the other hand, kinesiophobia and greater pain intensity during movement is found to be related with dynamic balance dysfunction in females with nonspecific low back pain [11]. Movement is an integral constituent of spinal control and postural recovery [12, 13], but individuals with low back pain are less likely to use anticipatory movement of the lumbar spine, which is associated with greater trunk displacement [12]. Research has shown intensity of pain to be related to the extent of postural sway [14] and thus relieving pain reduces postural sway in persons with non-specific low back pain [15]. Even though studies have looked into the effects of non-specific low back pain on postural stability and fall risk, the data is relatively scarce in terms of discogenic low back pain or in persons with degenerative disc disorders of the lumbar spine. Furthermore, literature is also deficient in terms of sensory integration of balance in persons with discogenic low back pain. Thus, the purpose of the current study is to determine the differences in terms of postural stability, fall risk and sensory integration of balance in persons with discogenic low back pain as compared to healthy controls.

2 Methods

2.1 Participants

A cross sectional comparative study was conducted at Foundation University Institute of Rehabilitation Sciences on 60 participants, out of which 30 participants had discogenic low back pain and 30 participants were age, weight, height, body mass index (BMI) and gender matched healthy controls. Participants in the discogenic low back pain group included persons with low back pain intensity of 8 or less on numeric pain rating scale, positive centralization phenomenon, bony vibration test, single leg raise, unilateral radiating pain in the leg with numbness or paresthesia, low signal intensity of the lumbar intervertebral disc on T2 weighted imaging, high intensity zone on the posterior aspect of the disc, and vertebral end plate modic changes. Participants were included in the study based on detailed objective examination and Magnetic Resonance Imaging scan findings. Ethical approval was acquired from Foundation University Ethical Review Committee, and informed consent was taken from participants before inclusion in the study.

2.2 Variables of interest

The variables of interest included postural stability (medio-lateral, antero-posterior and overall stability index), fall risk score (FRS) and clinical test of sensory integration of balance (CTSIB). A greater score in all of the mentioned outcome variables indicates a poorer score.

2.3 Test procedure and protocol

Data was collected for postural stability, fall risk score (FRS) and clinical test of sensory integration of balance (CTSIB) using Biodex Balance System^TM SD (Biodex Medical Systems, Inc., New York USA). Tests were performed indoors and the Biodex Balance System^TM SD was started keeping the platform in static position and then depending on the test patient was informed regarding the perturbations in the platform in a dynamic test before starting each test to ensure patient safety. The support handles were adjusted according to participant’s height and as per patient’s comfort and safety. The participants were instructed not to grab the support handles during the test. The visual display unit height was set up so that the patient’s eye level is at the level of the top border of the screen to guarantee appropriate posture and data collection. The participant was instructed to stand in a natural comfortable stance on the platform in a static position before the initiation of each test. The visual display unit displayed the participant’s center of gravity (COG) as a black dot, and the participant was instructed to place his/her feet on the platform and position himself/herself in such a way that the black dot was at or close to the center (Fig. 1). The participant’s foot placement on the platform grid was noted and entered into the system as shown in Fig. 1. For every test 3 trials were carried out and an average of 3 trials was considered. Platform stability level was kept stationary for CTSIB and dynamic, ranging from level 3–6 for fall risk score and postural stability assessment in accordance with the protocol advised by Karimi N et al for bilateral stance with an ICC_(3,1) of 0.95, 0.90 and 0.88 for overall, anteroposterior and mediolateral stability index respectively for persons with low back pain, and an ICC_(3,1) of 0.97, 0.93 and 0.91 for overall, anteroposterior and mediolateral stability index respectively for persons without low back pain [16]

Fig. 1

(a) Grid marked on the platform for identifying the foot position. (b) Participant’s center of gravity (COG) appearing on the VDU as a black dot and the participant’s foot placement according to the platform grid is noted and entered into the system.

2.4 Statistical analysis

Statistical analysis was carried out using Statistical Package of Social Sciences (IBM SPSS v 21.0). Kolmogorov Smirnov and Shapiro Wilk tests were used to determine normality of data. Between groups comparison was carried out using independent T-test, and within group comparison was carried out using paired t-test for continuous variables. Chi-square test was used for the comparison of gender between the two groups. Confidence interval was kept at 95% and a p-value of less than 0.05 was considered significant. In terms of sample size justification, with a sample size of 60 a power of 99.79%, 100% and 99.79% was calculated for the main variables of interest namely postural stability (overall stability index), FRS and CTSIB (composite score) respectively, which was calculated using OpenEpi [17].

3 Results

3.1 Participants

The current study consisted of 30 persons with discogenic low back pain and 30 healthy controls with no significant differences (p > 0.05) in terms of age, weight, height, body mass index and gender (Table 1).

Table 1
Individual characteristics of participants

Variable Group Mean±S.D P-value

Age (years) HC 42.27±3.78 0.642

LBP 43.00±7.69

Height (cm) HC 157.80±10.38 0.136

LBP 153.67±10.75

Weight (Kg) HC 78.13±12.75 0.961

LBP 78.30±13.67

Body Mass Index HC 31.41±4.48 0.172

LBP 33.17±5.34

Gender Male Female

HC 9 21 0.50

LBP 10 20

Variable	Group	Mean±S.D	P-value
Age (years)	HC	42.27±3.78	0.642
	LBP	43.00±7.69
Height (cm)	HC	157.80±10.38	0.136
	LBP	153.67±10.75
Weight (Kg)	HC	78.13±12.75	0.961
	LBP	78.30±13.67
Body Mass Index	HC	31.41±4.48	0.172
	LBP	33.17±5.34
Gender	Male	Female
	HC	9	21	0.50
	LBP	10	20

3.2 Postural stability

Healthy controls spent significantly greater percentage time in Zone A as compared to persons with discogenic low back pain, however, persons with discogenic low back pain spent significantly greater (p < 0.05) percentage time in Zone B, C and D (Table 2 & Fig. 2). Moreover, persons with discogenic low back pain spent greater percentage time in quadrant I, II and III, however the differences were not significant (p > 0.05), whereas healthy controls spent significantly greater (p < 0.05) time in quadrant IV (Table 2). Both healthy controls and persons with discogenic low back pain revealed higher anteroposterior postural stability index as compared to mediolateral postural stability index (p < 0.001), however persons with discogenic low back pain scored significantly (p < 0.05) higher in terms of overall, anteroposterior and mediolateral index as compared to healthy controls (Table 2).

Table 2
Overview of mean values and standard deviations for postural stability parameters

Variable Group Mean±S.D 95% Confidence Interval Mean difference Mean difference 95% Confidence Interval P-value

Lower Upper Lower Upper

Postural Stability Overall Stability Index HC 2.31±0.49 1.350749 3.262651 2.33 1.383223 3.276777 < 0.001

LBP 4.64±2.60 –0.44357 9.719574

Anterior/ Posterior Index HC 1.98±0.53 0.942356 3.017644 1.87 0.839691 2.900309 0.001

LBP 3.85±2.83 –1.68491 9.394307

Medial/Lateral Index HC 0.82±0.52 –0.19539 1.84199 0.82 0.426159 1.213841 < 0.001

LBP 1.64±0.97 –0.25922 3.547219

% Time in Zone A HC 98.03±4.55 89.1218 106.9382 –44.43 –54.3622 –34.4978 < 0.001

LBP 53.60±27.38 –0.06284 107.2628

% Time in Zone B HC 1.97±4.55 –6.9382 10.8782 25.9 16.38765 35.41235 < 0.001

LBP 27.87±26.19 –23.4644 79.20436

% Time in Zone C HC 0.00±0.00 0 0 13.67 7.146478 20.19352 < 0.001

LBP 13.67±18.23 –22.0628 49.40276

% Time in Zone D HC 0.00±0.00 0 0 5.2 0.297518 10.10248 0.047

LBP 5.20±13.70 –21.6559 32.05592

% Time in Quadrant I HC 7.20±17.41 –26.9177 41.31772 11.07 –0.86569 23.00569 0.075

LBP 18.27±28.45 –37.4979 74.03788

% Time in Quadrant II HC 11.77±28.31 –43.7078 67.2478 14.43 –1.35825 30.21825 0.078

LBP 26.20±33.84 –40.1166 92.5166

% Time in Quadrant III HC 22.20±28.71 –34.0638 78.46376 4.3 –9.20142 17.80142 0.535

LBP 26.50±24.48 –21.4788 74.47884

% Time in Quadrant IV HC 58.83±35.98 –11.6967 129.3567 –29.8 –46.3548 –13.2452 0.001

LBP 29.03±29.08 –27.9746 86.03464

Variable		Group	Mean±S.D	95% Confidence Interval	Mean difference	Mean difference 95% Confidence Interval	P-value
Postural Stability	Overall Stability Index	HC	2.31±0.49	1.350749	3.262651	2.33	1.383223	3.276777	< 0.001
		LBP	4.64±2.60	–0.44357	9.719574
	Anterior/ Posterior Index	HC	1.98±0.53	0.942356	3.017644	1.87	0.839691	2.900309	0.001
		LBP	3.85±2.83	–1.68491	9.394307
	Medial/Lateral Index	HC	0.82±0.52	–0.19539	1.84199	0.82	0.426159	1.213841	< 0.001
		LBP	1.64±0.97	–0.25922	3.547219
	% Time in Zone A	HC	98.03±4.55	89.1218	106.9382	–44.43	–54.3622	–34.4978	< 0.001
		LBP	53.60±27.38	–0.06284	107.2628
	% Time in Zone B	HC	1.97±4.55	–6.9382	10.8782	25.9	16.38765	35.41235	< 0.001
		LBP	27.87±26.19	–23.4644	79.20436
	% Time in Zone C	HC	0.00±0.00	0	0	13.67	7.146478	20.19352	< 0.001
		LBP	13.67±18.23	–22.0628	49.40276
	% Time in Zone D	HC	0.00±0.00	0	0	5.2	0.297518	10.10248	0.047
		LBP	5.20±13.70	–21.6559	32.05592
	% Time in Quadrant I	HC	7.20±17.41	–26.9177	41.31772	11.07	–0.86569	23.00569	0.075
		LBP	18.27±28.45	–37.4979	74.03788
	% Time in Quadrant II	HC	11.77±28.31	–43.7078	67.2478	14.43	–1.35825	30.21825	0.078
		LBP	26.20±33.84	–40.1166	92.5166
	% Time in Quadrant III	HC	22.20±28.71	–34.0638	78.46376	4.3	–9.20142	17.80142	0.535
		LBP	26.50±24.48	–21.4788	74.47884
	% Time in Quadrant IV	HC	58.83±35.98	–11.6967	129.3567	–29.8	–46.3548	–13.2452	0.001
		LBP	29.03±29.08	–27.9746	86.03464

Fig. 2

Example of test report figure from Biodex Balance System SD divided into zones A, B, C and D and, quadrants I, II, III and IV.

3.3 Fall risk score

Persons with discogenic low back pain secured significantly (p < 0.05) higher in terms of fall risk score as compared to healthy controls (Table 3).

Table 3
Overview of mean values and standard deviations for fall risk score (FRS), clinical test of sensory integration of balance (CTSIB) and Romberg quotient

Variable Group Mean±S.D 95% Confidence Interval Mean Mean difference 95% Confidence Interval P-value

Lower Upper Lower Upper

FRS HC 1.98±1.03 –0.03864 4.005236 2.92 2.356805445 3.483194555 < 0.001

LBP 4.90±1.19 2.560426 7.239574

CTSIB Eyes Open Firm Surface HC 0.80±0.74 –0.65213 2.244126 1.74 1.280325327 2.199674673 < 0.001

LBP 2.54±1.05 0.48931 4.58869

Eyes Closed Firm Surface HC 0.85±0.21 0.44095 1.26705 1.57 1.228824854 1.911175146 < 0.001

LBP 2.42±0.93 0.607485 4.235915

Eyes Open Foam Surface HC 0.92±0.32 0.291604 1.548396 1.97 1.473522547 2.466477453 < 0.001

LBP 2.89±1.35 0.236628 5.533372

Eyes Closed Foam Surface HC 2.36±0.54 1.306404 3.421596 1.2 0.758281918 1.641718082 < 0.001

LBP 3.56±1.11 1.382788 5.742612

Composite Score HC 1.28±0.45 0.405782 2.158218 1.67 1.277591879 2.062408121 < 0.001

LBP 2.95±1.00 0.997042 4.903558

Romberg quotient Firm Surface HC 1.43±0.51 0.426036 2.440564 –0.38 –0.618712659 –0.141287341 0.002

LBP 1.05±0.43 0.207778 1.883422

Foam Surface HC 2.74±0.80 1.161932 4.310868 –1.3 –1.657845404 –0.942154596 < 0.001

LBP 1.44±0.60 0.261224 2.613576

Variable		Group	Mean±S.D	95% Confidence Interval	Mean	Mean difference 95% Confidence Interval	P-value
FRS		HC	1.98±1.03	–0.03864	4.005236	2.92	2.356805445	3.483194555	< 0.001
		LBP	4.90±1.19	2.560426	7.239574
CTSIB	Eyes Open Firm Surface	HC	0.80±0.74	–0.65213	2.244126	1.74	1.280325327	2.199674673	< 0.001
		LBP	2.54±1.05	0.48931	4.58869
	Eyes Closed Firm Surface	HC	0.85±0.21	0.44095	1.26705	1.57	1.228824854	1.911175146	< 0.001
		LBP	2.42±0.93	0.607485	4.235915
	Eyes Open Foam Surface	HC	0.92±0.32	0.291604	1.548396	1.97	1.473522547	2.466477453	< 0.001
		LBP	2.89±1.35	0.236628	5.533372
	Eyes Closed Foam Surface	HC	2.36±0.54	1.306404	3.421596	1.2	0.758281918	1.641718082	< 0.001
		LBP	3.56±1.11	1.382788	5.742612
	Composite Score	HC	1.28±0.45	0.405782	2.158218	1.67	1.277591879	2.062408121	< 0.001
		LBP	2.95±1.00	0.997042	4.903558
Romberg quotient	Firm Surface	HC	1.43±0.51	0.426036	2.440564	–0.38	–0.618712659	–0.141287341	0.002
		LBP	1.05±0.43	0.207778	1.883422
	Foam Surface	HC	2.74±0.80	1.161932	4.310868	–1.3	–1.657845404	–0.942154596	< 0.001
		LBP	1.44±0.60	0.261224	2.613576

3.4 Clinical test of sensory integration of balance (CTSIB) and Romberg quotient

Persons with discogenic low back pain secured significantly (p < 0.05) higher in terms of CTSIB composite score as well as specific scores during all 4 conditions as compared to healthy controls (Table 3). Furthermore, healthy controls exhibited a significantly higher (p < 0.05) Romberg quotient as compared to persons with discogenic low back pain in both conditions including firm surface and foam surface (Table 3).

3.5 Reference values

Unadjusted reference values have been provided in Table 1, expressed in terms of Mean±S.D and 95% confidence interval, for postural stability, fall risk score, CTSIB and Romberg quotient (Tables 2 & 3).

4 Discussion

The purpose of the current study was to determine the differences in terms of postural stability, fall risk and sensory integration of balance in persons with discogenic low back pain as compared to healthy controls. The findings of the current study have shown poorer postural stability in persons with discogenic low back pain as compared to healthy controls in overall as well as anteroposterior and mediolateral stability index. The findings of the current study are in accordance with the findings of Svoboda Z et al, which was also conducted on persons with lumbar disc herniation and found them to have increased mediolateral sway in narrow base of support setting [6], however in the current study, an increased postural sway was observed in both anteroposterior and mediolateral direction in persons with discogenic low back pain. Even though, there is scarcity of published literature regarding the effects of discogenic low back pain on postural stability, studies have demonstrated poorer stability in persons with chronic and non-specific low back pain.

A study, conducted by Karimi N et al used the same Biodex Balance System^TM SD in their study and observed a poorer overall and mediolateral stability index in persons with low back pain as compared to healthy controls, with eyes open as well as eyes closed [16]. These findings were in accordance with the findings of the current study, not only in terms of postural stability, but also in terms of sensory integration of balance in which the findings of the current study have shown poorer CTSIB composite score, as well as CTSIB scores in all tasks including eyes open firm surface, eyes closed firm surface, eyes open foam surface and eyes closed foam surface in persons with discogenic low back pain as compared to healthy controls. However, in Karimi N et al’s study the type of low back pain was not specified and no significant differences were observed in the anteroposterior stability index in persons with and without low back pain, unlike the current study [16]. Moreover, a study conducted by Caffaro RR et al has also shown poorer postural control in persons with chronic non-specific low back pain and with increased oscillation of center of pressure, which is observed to be magnified by visual deprivation and unstable surface conditions [7]. Furthermore, it is imperative to point out that previous studies haven’t shown significant gender based differences in terms of postural control in persons with non-specific low back pain [11], however gender based differences have not been described in the findings of the current study as they were not the aim of the current study.

The findings of the current study have also shown a greater fall risk in persons with discogenic low back pain which is in accordance with the findings of Rosa N et al showing greater risk of fall in the elderly population with low back pain as compared to persons without low back pain in Brazil [10]. Furthermore, studies conducted in United States have also shown an increased risk of fall in community dwelling older adults with a recent history of low back pain, regardless of gender [8, 9].

Thus, in light of the findings of the current study it is safe to say, that persons with discogenic low back pain have greater fall risk and poorer postural stability and sensory integration of balance in comparison to their healthy counterparts.

5 Conclusion

Persons with discogenic low back pain exhibit greater risk of fall and poorer postural stability and sensory integration of balance as compared to healthy controls.

6 Recommendations

It is suggested that future studies should look at postural stability and fall risk with eyes open as well as eyes closed. Moreover, future studies should also determine gender based differences in terms of fall risk, postural stability and CTSIB in persons with and without discogenic low back pain. Clinical trials should also include postural stability, fall risk and sensory integration of balance as outcome measures in persons with discogenic low back pain.

Conflict of interest

The author has no conflict of interest to report.

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