An open-label pilot study of pulsed electromagnetic field therapy in the treatment of failed back surgery syndrome pain

Figures & data

Table 1 Inclusion and exclusion criteria

Inclusion criteria

Exclusion criteria

• Age ≥18 years • History of one or two anatomically successful lumbar spine surgeries for the treatment of low back pain • Pain in the low back and/or radiating to leg(s) at 3–36 months following surgery • Stable analgesic dosing regimen for ≥30 days • Mean pain intensity of 4 or greater (NPRS) in the subject’s low back or leg(s) during the study run-in phase • Willingness and ability to give written informed consent and to comply with all parts of the study protocol • Ability to read, understand, and follow study instructions • Ability to maintain a pain and symptom diary on a daily basis • For female subjects, be postmenopausal, surgically sterile, abstinent, or agree to practice an effective method of birth control for the duration of the study if sexually active

• More than two lumbar spine surgeries • Received any investigational drug or device within 30 days prior to study screening visit or is enrolled in another clinical trial • History of any uncontrolled medical illness or ongoing painful condition that, in the investigator’s judgment, places the subject at unacceptable risk • History of an ongoing painful condition that, in the investigator’s judgment, might have a confounding influence on safety and effectiveness analyses • Anticipated need for surgery of any type during the next 3 months • Serious psychosocial comorbidities • History of drug or alcohol abuse within 1 year prior to screening • History of malignancy within the past 5 years other than successfully treated non-metastatic basal cell or squamous cell carcinomas of the skin and/or localized carcinoma in situ of the cervix • Implanted pacemaker, defibrillator, neurostimulator, spinal cord stimulator, bone stimulator, cochlear implant, or other implanted device with an implanted metal lead(s) • Existing or planned pregnancy • Previous treatment with the study device • In current litigation regarding back pain, or receiving Workers’ Compensation

Abbreviation: NPRS, numerical pain rating scale.

Figure 1 Flow chart of study participants.

Abbreviations: NPRS, numerical pain rating scale; PEMF, pulsed electromagnetic field.

Table 2 Subject baseline characteristics

Population	N	% female	Age (years)	BMI	Months since surgery	Number of surgeries	Baseline scores
							Back PI	Leg PI	ODI
Intent-to-treat	34	67.6	55.0±11.1	31.1±5.6	16.3±9.6	1.3±0.5	6.0±1.6	5.3±2.3	42.4±12.7
Per-protocol	30	66.7	54.7±10.8	31.2±6.0	16.9±9.7	1.3±0.4	6.0±1.6	5.3±2.5	43.1±12.7
Discectomy	10	70	57.3±10.1	32.7±6.5	14.6±10.2	1.3±0.5	5.3±1.8	5.3±2.1	41.4±12.0
Decompression	14	50	54.5±9.2	31.1±6.1	21.2±8.4	1.2±0.4	6.2±1.2	5.3±2.3	41.6±12.1
Fusion	6	100	50.7±13.7	29.0±3.7	10.7±6.3	1.3±0.5	6.9±1.7	5.5±3.3	49.7±12.8

Notes: Data reported as a percentage (% female) or mean ± standard deviation. Baseline PI scores are mean scores reported for the 5 consecutive days beginning the day of the screening visit. The discectomy subpopulation includes two subjects with both discectomy and decompression.

Abbreviations: BMI, body mass index; N, number; ODI, Oswestry Disability Index; PI, pain intensity.

Figure 2 Mean weekly numerical pain rating scores for responders.

Notes: (A) Back pain. (B) Leg pain. Mean scores for all data reported are shown. Week 1: Days 0–7; Week 2: Days 8–14; Week 3: Days 15–21; Week 4: Days 22–28; Week 5: Days 29–35; Week 6: Days 36–42; Week 7: Days 43–45.
Abbreviation: NPRS, numerical pain rating scale score.

Table 3 Responder analysis for complete per-protocol population and procedure-based subpopulations

Population	N (%)	%Δ PI back	%Δ PI leg	%Δ ODI	PGIC: improved or much improved	% using less analgesia
Per-protocol
Responders	10 (33%)	44%±28%	55%±27%	13.1%±11.1%	67%	50%
Nonresponders	20 (67%)	5%±14%	−1%±26%	3.1%±8.7%	0%	12%
Discectomy
Responders	6 (60%)	44%±29%	54%±30%	16.5%±12.5%	100%	33%
Nonresponders	4 (40%)	2%±22%	−5%±33%	−3.0%±4.1%	0%	25%
Decompression
Responders	3 (21%)	48%±28%	64%±20%	6.0%±4.9%	50%	50%
Nonresponders	11 (79%)	6%±12%	−1%±17%	6.2%±8.7%	0%	10%
Fusion
Responders	1 (17%)	30%	38%	14%	0%	100%
Nonresponders	5 (83%)	4%±8%	−1%±33%	1.2%±8.1%	0%	0%

Notes: Responders were defined as subjects who reported reduction in pain scores of 30% or greater (final reported score versus baseline). Data is reported as mean ± standard deviation (%Δ PI back, %Δ PI leg, % Δ ODI) or as percent. PI, PGIC, and analgesia data are reported as change between end of treatment score (Day 45) and baseline score, except for change in PI, which includes one subject who reported a final PI score at day 37. Change in PGIC and analgesic scores represents only subjects who reported final PGIC and analgesic consumption scores at the end of the defined treatment period (Day 45) and excludes six per protocol subjects (two discectomy responders, one decompression responder, one decompression non-responder, two fusion non-responders) who reported final PGIC and analgesic consumption at 5 weeks and one per protocol subject (one discectomy responder) who reported final PGIC and analgesic consumption at 4 weeks. ODI data reported as change between Day 46 follow-up scores and baseline. For percent change in PI and ODI, improvement is denoted by a positive value.

Abbreviations: %Δ, percent change; Δ, change; N, number; ODI, Oswestry Disability Index; PGIC, Patient Global Impression of Change; PI, pain intensity.

Table 4 Percentage of subjects with clinically meaningful outcomes (end of treatment versus baseline)

Population	N	Δ PI ≥30%	Δ ODI ≥6%	PGIC: improved or much improved	Less analgesics
Per-protocol	30	33%	50%	17%	22%
Discectomy	10	60%	40%	43%	29%
Decompression	14	21%	57%	8%	17%
Fusion	6	17%	50%	0%	25%

Notes: PI, PGIC, and analgesic data are reported as change between end of treatment score (Day 45) and baseline score, except for change in PI, which includes one subject who reported a final PI score at day 37. ODI data are reported as change between Day 46 follow-up score and baseline score. Change in PGIC and analgesic scores represents only subjects who reported final PGIC and analgesic consumption scores at the end of the defined treatment period (Day 45) and excludes six per protocol subjects (two discectomy responders, one decompression responder, one decompression non-responder, two fusion non-responders) who reported final PGIC and analgesic consumption at 5 weeks and one per protocol subject (one discectomy responder) who reported final PGIC and analgesic consumption at 4 weeks.

Abbreviations: Δ, change; N, number; ODI, Oswestry Disability Index; PGIC, Patient Global Impression of Change; PI, pain intensity.

Table 5 Treatment-emergent adverse events

Frequency	Adverse event
Two events of	Epistaxis
	Increased leg pain
	Increased back pain
One event of	Headache
	Left arm ache
	Tingling of skin across upper abdomen
	Increased hypertension
	Chest pain

Figure 3 Cost-avoidance survey results for per-protocol survey respondents (28/30).

Notes: Green stippled bars indicate the percentage of subjects who did not think they would need the specified intervention for low back pain in the 6 months following the survey. Violet bars indicate the percentage of subjects who felt it was possible to avoid the specified intervention for back pain after the trial (only subjects who were discussing the possibility of the specified intervention with their doctor prior to the trial provided a response). The number of survey respondents who, prior to the trial, were discussing with their doctor: any invasive option (14 subjects), a stimulator or pump implant (five subjects), additional surgery (six subjects), or injections/ablation (eight subjects).
Abbreviation: PT, physical therapy.