We studied 8 patients with spinal cord stimulation (SCS) devices which had been previously implanted to treat neuropathic chronic pain secondary to Failed Back Surgery Syndrome. The aim of our study was to investigate the effects of SCS on posture and gait by means of clinical scales (Short Form Health Survey-36, Visual Analogue Scale for pain, and Hamilton Depression Rating Scale) and instrumented evaluation with 3D Gait Analysis using a stereophotogrammetric system. The latter was performed with the SCS device turned both OFF and ON. We recorded gait and posture using the Davis protocol and also trunk movement during flexion-extension on the sagittal plane, lateral bending on the frontal plane, and rotation on the transversal plane. During and 30 minutes after the stimulation, not only the clinical scales but also spatial-temporal gait parameters and trunk movements improved significantly. Improvement was not shown under stimulation-OFF conditions. Our preliminary data suggest that SCS has the potential to improve posture and gait and to provide a window of pain-free opportunity to optimize rehabilitation interventions.
Chronic pain of moderate to severe intensity occurs in 19% of adult Europeans, seriously affecting the quality of their social and working lives [
Beneficial effects of SCS on balance and risk of fall have been reported in a study on 11 subjects [
A biomechanical study in 2005 [
The aim of our study was therefore to verify by means of 3D Gait Analysis whether SCS is able to improve posture and gait in FBSS patients.
We studied 8 patients with SCS devices which had been implanted to treat neuropathic chronic pain secondary to FBSS. The patients were 4 males and 4 females, mean age
The year of implant of the SCS device ranged from 2010 to 2014. Four different models of SCS device had been implanted in our 8 experimental patients. The patients’ characteristics, the SCS devices and their year of implant, and the scores of the clinical scales used in the study are described in Table
The general picture at T0: patients’ clinical features, model of SCS device, year of implant of the device, clinical scales (Visual Analogue Scales (VAS), Hamilton Depression Rating Scale (HAM-D), and Short Form Health Survey-36 (SF-36)), and functional scores (Medical Research Council, Timed Up and Go). HAM-D scores of 0–7 are considered to be normal; scores of 8–17 indicate a mild depression, scores of 18–24 a moderate depression, and scores > 25 a severe depression.
Age |
Pain localization | Type of pain | SCS device | Year of implant | VAS |
HAM-D | SF-36 |
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79 | Lower back and left lower limb | hypoesthesia | SYNERGY VERSITREL |
2013 | 80 | 18 | 20 |
52 | Lower back and left lower limb | disesthesia | VECTRIS SURESCAN |
2014 | 90 | 21 | 5 |
73 | Lower back and left lower limb | disesthesia | VECTRIS SURESCAN |
First in 2005 |
80 | 13 | 7 |
51 | Lower back and left lower limb | disesthesia | SINERGY VERSITREL |
First in 2005 |
100 | 25 | 10 |
75 | Lower back and right lower limb | hypoesthesia | PRIME ADVANCED |
2014 | 80 | 24 | 18 |
61 | Lower back and right lower limb | disesthesia | PRIME ADVANCED |
First in 2012 |
100 | 43 | 0 |
55 | Lower back and left lower limb | hypoesthesia | ITREL 4 MEDTRONIC | 2010 | 90 | 29 | 10 |
76 | Lower back and left lower limb | hypoesthesia | ITREL 4 MEDTRONIC | 2013 | 80 | 15 | 30 |
We studied those patients in the Movement Analysis Research Laboratory of the same hospital. The study has been performed in accordance with the Declaration of Helsinki. All subjects provided informed consent to the study approved by the Ethics Committee of the Santa Corona Hospital.
Subjects were evaluated with both clinical scales and an instrumented-quantitative evaluation in order to evaluate the effects of SCS in terms of perceived physical functioning, pain, health status, and movement.
Before (T0) and after (T1) the stimulation, all of the subjects were asked to fill the Short Form Health Survey-36 (SF-36) (Ware and Sherbourne, 1992 [
The SF-36 is a 36-item, patient-reported survey of patient’s health. SF-36 includes one multi-item scale measuring each of 8 health concepts: (1) physical functioning; (2) role limitations because of physical health problems; (3) bodily pain; (4) social functioning; (5) general mental health (psychological distress and psychological well-being); (6) role limitations because of emotional problems; (7) vitality (energy/fatigue); and (8) general health perceptions. The 8 scaled scores are the weighted sums of the questions in their section. Each scale is directly transformed into a 0–100 scale on the assumption that each question carries equal weight. Lower scores evidence more disability.
The Visual Analogue Scale (VAS) consists of a 10 cm straight line with the endpoints defining extreme limits such as “no pain at all” and “pain as bad as it could be.” The patient is asked to mark his pain level on the line between the two endpoints. The distance between “no pain at all” and the mark then defines the subject’s pain.
The HAM-D is a multi-item questionnaire used to provide an indication of depression and as a guide to evaluate recovery. The questionnaire is designed for adults and is used to rate the severity of their depression by probing mood, feelings of guilt, suicide ideation, insomnia, agitation or retardation, anxiety, weight loss, and somatic symptoms. Each item on the questionnaire is scored on a 3- or 5-point scale, depending on the item. A score of 0–7 is considered to be normal; scores of 8–17 indicate a mild depression, scores of 18–24 a moderate depression, and scores > 25 a severe depression.
Instrumented evaluation was performed in a morning section under two different conditions: with the SCS device turned off (OFF) and on (ON).
All subjects were asked to switch off the device 12 hours before the evaluation. In the morning, they were first evaluated with the SCS device turned off (OFF). Then, the device was switched on (ON) and, after 30 minutes of SCS, they were evaluated again. This lapse of time was chosen for the patients to fully perceive the effects of the stimulation (paresthesia).
Instrumented movement analysis was performed with a stereophotogrammetric system (SMART DX, BTS Bioengineering, Milan, Italy). The system is composed of eight infrared cameras (SMART DX 5000, BTS Bioengineering) and four force platforms (P6000, BTS Bioengineering).
We recorded the position of 22 reflective markers positioned on the patient body according to the Davis protocol [
After measuring anthropometric parameters (weight, height, hip height, hip width, knee and ankle width, and leg length) subjects were first asked to stand still on a force platform for 5 seconds; then, they were asked to walk, at their preferred speed on a 9-meter walkway at least five times to obtain a minimum of three trials complete of kinematic and kinetic data.
Trunk kinematics were assessed under three different movement conditions: flexion-extension on the sagittal plane, lateral bending on the frontal plane, and rotation on the transversal plane.
In the flexion-extension task, subjects were asked to bend forward as much as possible from an upright position with the arms loose towards the floor and the knee extended and then to lean backwards to the maximal extension.
In the lateral bending task, subjects were asked to bend the trunk sideways in the frontal plane with the arms adducted and knee extended.
In the third task, rotation in the transversal plane to the maximal excursion was required.
Each trial consisted of three complete movements (flexion-extension, left and right bending, and left and right rotation). Subjects performed this evaluation test with their feet placed on a force platform in order to register Center of Pressure (CoP) data during movement. We record also the position of nine markers placed on the spinal processes (C7, T2, T8, T10, and L5) and bilaterally on the acromion and the superior iliac posterior spine (Figure
Reference points for the markers placed for the trunk motion task. SIPS, superior iliac posterior spine; ACR, acromion.
Gait and kinematics data were analyzed by SMART Tracker and SMART Analyzer (BTS Bioengineering, Milano) and MATLAB (MathWorks, Natick, MA, US).
Student’s
Comparison at T0 and T1 of all self-reported scales of health status showed an improvement in performance and a reduction of negative symptoms in all subjects (Table
Panel (A) shows delta value ± standard error (SE) and
Clinical scales | Gait parameters | 3D trunk banding speed index | ||||||||
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Physical functioning |
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Stance phase | R |
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R | Outward |
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Physical health |
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L |
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Return |
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Limitation | ||||||||||
Emotional problem |
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Swing phase | R |
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L | Outward |
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Energy/fatigue |
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L |
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Return |
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Emotional well-being Being |
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Social functioning |
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Forward |
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Stride | R |
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Backward |
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General health |
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L |
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Spatial-temporal parameters showed a general improvement. In particular, we recorded a significant improvement in velocity (
As for ground reaction forces (GRF), we considered both the vertical and anterior-posterior components.
We considered the maximum peak of the GRF vertical component. Comparison between OFF and ON showed inconsistent increases in vertical force peaks; therefore no statistical significance was evident. Different strategies were observed: in 3 subjects (numbers 3, 4, and 6) the pattern was normal during OFF and did not change during ON; in 1 subject (number 2), both limbs showed an increase of both first and second peaks during ON; in 2 subjects (numbers 5 and 7) an improvement on the affected side was present during ON. During ON, no differences on the affected side were observed in 1 subject (number 1), and in another subject (number 8), only a small increase in the vertical force peak was evident.
Mean values in both left and right limb for this component under OFF and ON conditions were calculated: +
Changes in GRF peak values on both sides under ON and OFF conditions.
Subjects performed in the coronal plane three lateral bending movements to the right and three to the left during the OFF and the ON phases. Amplitude and pattern of motion were observed. During ON, we observed in all of the patients a modification of the trunk strategy, resulting in a smoother task execution. In 4 patients, the smooth execution was also due to an additional movement of the trunk on the sagittal plane.
As shown in Figure
Improvements in cervical and dorsal spine ROM in lateral bending on both sides during ON.
In 4 subjects (numbers 2, 4, 6, and 8), an increased ROM in the coronal plane corresponded to an increase in the vertical axis but also to a higher forward shift of the trunk. In 2 subjects (numbers 5 and 7), an increased ROM in both vertical and coronal components and a reduction of the forward bending were evident. One subject (number 3) showed an increased ROM only in the coronal plane and in another subject (number 1), no difference in ROM was evident between OFF and ON.
Three subjects (numbers 2, 4, and 8) had the same pattern as in the contralateral bending. In three subjects (numbers 2, 5, and 7), an increase in the vertical and lateral ROM and a decrease in forward bending were evident. One subject (number 3) showed an increase in lateral and forward bending components but a decrease in the vertical one. One subject (number 6) showed a reduction in the vertical one.
Other indexes, such as path length, duration, distance, smoothness index jerk (not shown in the paper), and speed, were also analyzed. However, speed was the best index to demonstrate the improvement of performance during the ON phase (Table
Patients chronically exposed to pain adopt compensatory strategies in order to avoid painful movements. This compensation can result in abnormalities of gait and posture. We felt therefore that investigating quantitative changes in gait and posture in FBSS patients after SCS would provide some initial evidence on the functional effectiveness of the treatment. The relationship between functioning of the spine and pain has been extensively addressed; however, we are aware that research on its correlation is still generally equivocal and considerations about the relationship between pain and functioning were beyond the scopes of our preliminary study.
Gait Analysis, the gold standard for quantification of the cinematics of human movement, was used in this study for that purpose.
Kinematics of gait and of the spine showed improvement during ON but not under the stimulation-OFF condition. During ON, improved kinetics of the lower limbs are evident: data indicate lower loading at joints level in the unaffected limb. At spinal level, compensatory strategies appear reduced but not eliminated, suggesting that neuromodulation itself may not be able to influence all of the factors involved in pain-related disuse (i.e., muscle contractures and reduced muscle strength and volume).
In our study, patients were evaluated in the morning under two different conditions: (1) stimulation OFF for the previous 12 hours, (2) 30 minutes after the stimulator had been ON. The latter condition served to investigate not only the effects on pain relief, but also the direct impact on gait and posture.
Our preliminary data indicate that stimulation positively affects patient’s walking and reduces compensatory patterns, as shown by kinematic parameters. This provides some initial evidence that SCS may be useful in providing a window of pain-free opportunity to intensify rehabilitation interventions and to maximize function. This could widen the range of effective interventions of rehabilitation professionals and boost further research in the rehabilitation of complex chronic pain patients.
Data from the trunk during ON showed an increase in range of motion and smoothness of the trunk motion during the tasks. A reduced compensatory strategy of the trunk was also evident. Our results provide quantification of the compensations occurring in posture and gait in patients with chronic pain and a deeper insight into the components of gait or trunk control that improve after implant of an SCS device. A better understanding of these mechanisms can help generate tailored and more effective rehabilitation programs. For instance, reduction of ground reaction forces on the unaffected lower limb improves the symmetry of loading, thus alleviating joint overload. From the 3D analysis of the trunk motion, a smoother movement was evident. Meanwhile, the compensation strategies partially persisted, meaning that pain could not entirely account for the modifications observed in movement patterns. These observations have to be taken into account for ad hoc rehabilitation programs.
Our preliminary study yields some evident limitations: firstly, the study is performed in 8 patients only, 4 of whom complained of hypoaesthesia and 4 of disaesthesia; secondly, there is a lack of appropriate sham or concealed observation; thirdly, our results refer exclusively to the immediate effects of neuromodulation; and also, different models of SCS device had been previously implanted in our 8 subjects at different times, from 2010 to 2014, which, together with different positioning of the electrodes, depending on the type of pain, may have influenced results. However, modalities of neuromodulation delivery were consistent across the types of devices used and, technically, the devices differed only in recharging capacity and compatibility with MRI investigations. Therefore, any generalization about the clinical utility of SCS in FBBS from our data is premature and needs support from larger and also long-term studies.
A multilevel kinetic and cinematic 3D analysis in a small sample of patients with failed back syndrome with SCS implant has provided additional quantitative information regarding posture and gait modifications secondary to spinal cord stimulation.
Failed Back Surgery Syndrome
Spinal cord stimulation
Three-dimension
Center of Pressure
Posterior superior iliac spine
Ground reaction forces
Range of motion
Visual Analogue Scale
Short Form Health Survey-36
Hamilton Depression Rating Scale.
This study has been performed in accordance with the Declaration of Helsinki.
All subjects provided informed consent to the study approved by the Ethics Committee of the Santa Corona Hospital.
The authors declare that they have no conflicts of interest.
L. Brugliera conceived the study, selected patients, and performed clinical evaluations and laboratory testing, A. De Luca performed cinematic analysis, S. Corna contributed to data analysis and supervised the final editing of the manuscript, M. Bertolotto selected patients and performed clinical evaluations and laboratory testing, G. A. Checchia contributed to the editing of the manuscript, M. Cioni supervised the final draft of the manuscript, P. Capodaglio contributed to data analysis and supervised the final editing of the manuscript, and C. Lentino conceived the study and supervised the final editing of the manuscript.