The effect of prior lumbar surgeries on the flexion relaxation phenomenon and its responsiveness to rehabilitative treatment

The Spine Journal 14 (2014) 892–902

Clinical Study

The effect of prior lumbar surgeries on the flexion relaxation phenomenon and its responsiveness to rehabilitative treatment Randy Neblett, MA, LPC, BCBa, Tom G. Mayer, MDb,*, Emily Brede, RN, PhDa, Robert J. Gatchel, PhD, ABPPc a PRIDE Research Foundation, 5701 Maple Ave. #100, Dallas, TX 75235, USA Department of Orthopedic Surgery, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75235, USA c Department of Psychology, College of Science, The University of Texas at Arlington, 313 Life Science Building, Arlington, TX 76019, USA b

Received 26 October 2011; revised 12 June 2013; accepted 13 July 2013

Abstract

BACKGROUND CONTEXT: Abnormal pretreatment flexion-relaxation in chronic disabling occupational lumbar spinal disorder patients has been shown to improve with functional restoration rehabilitation. Little is known about the effects of prior lumbar surgeries on flexion-relaxation and its responsiveness to treatment. PURPOSE: To quantify the effect of prior lumbar surgeries on the flexion-relaxation phenomenon and its responsiveness to rehabilitative treatment. STUDY DESIGN/SETTING: A prospective cohort study of chronic disabling occupational lumbar spinal disorder patients, including those with and without prior lumbar spinal surgeries. PATIENT SAMPLE: A sample of 126 chronic disabling occupational lumbar spinal disorder patients with prior work-related injuries entered an interdisciplinary functional restoration program and agreed to enroll in this study. Fifty-seven patients had undergone surgical decompression or discectomy (n532) or lumbar fusion (n525), and the rest had no history of prior injury-related spine surgery (n569). At post-treatment, 116 patients were reevaluated, including those with prior decompressions or discectomies (n530), lumbar fusions (n521), and no surgery (n565). A comparison group of 30 pain-free control subjects was tested with an identical assessment protocol, and compared with post-rehabilitation outcomes. OUTCOME MEASURES: Mean surface electromyography (SEMG) at maximum voluntary flexion; subject achievement of flexion-relaxation (SEMG#3.5 mV); gross lumbar, true lumbar, and pelvic flexion ROM; and a pain visual analog scale self-report during forward bending task. Identical measures were obtained at pretreatment and post-treatment. METHODS: Patients entered an interdisciplinary functional restoration program, including a quantitatively directed, medically supervised exercise process and a multimodal psychosocial disability management component. The functional restoration program was accompanied by a SEMGassisted stretching training program, designed to teach relaxation of the lumbar musculature during end-range flexion, thereby improving or normalizing flexion-relaxation and increasing lumbar flexion ROM. At 1 year after discharge from the program, a structured interview was used to obtain socioeconomic outcomes. RESULTS: At pre-rehabilitation, the no surgery group patients demonstrated significantly better performance than both surgery groups on absolute SEMG at maximum voluntary flexion and on true lumbar flexion ROM. Both surgery groups were less likely to achieve flexion-relaxation than

FDA device/drug status: Not applicable. Author disclosures: RN: Nothing to disclose. TGM: Nothing to disclose. EB: Nothing to disclose. RJG: Grant: National Institutes of Health (I, Paid directly to institution/employer); Royalties: Guilford Press (B), APA Press (B), Springer (B); Consulting: PRIDE (B); Scientific Advisory Board/Other Office: Pallidian Health Care (B); Endowments: Nancy P. and John G. Penson Endowed Professorship in Clinical Health Psychology (F). The disclosure key can be found on the Table of Contents and at www. TheSpineJournalOnline.com. 1529-9430/$ - see front matter Ó 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.spinee.2013.07.442

This research study was presented at the Annual Meeting of the North American Spine Society, November 1–5, 2011 in Chicago, Illinois, and the abstract was included in the transactions of the meeting published in The Spine Journal. * Corresponding author. PRIDE Research Foundation, 5701 Maple Ave., Suite 100, Dallas, TX 75235, USA. Tel.: (214) 351-6600; fax: (214) 351-6453. E-mail address: [email protected] (T.G. Mayer)

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the no surgery patients. The fusion patients had reduced gross lumbar flexion ROM and greater pain during bending compared with the no surgery patients, and reduced true lumbar flexion ROM compared with the discectomy patients. At post-rehabilitation, all groups improved substantially on all measures. When post-rehabilitation measures were compared with the pain-free control group, with gross and true lumbar ROM corrected by 8
per spinal segment fused, there were no differences between any of the patient groups and the pain-free control subjects on spinal ROM and only small differences in SEMG. The three groups had comparable socioeconomic outcomes at 1 year posttreatment in work retention, health-care utilization, new injury, and new surgery. CONCLUSIONS: Despite the fact that the patients with prior surgery demonstrated greater pretreatment SEMG and ROM deficits, functional restoration treatment, combined with SEMGassisted stretching training, was successful in improving all these measures by post-treatment. After treatment, both groups demonstrated ROM within anticipated limits, and the majority of patients in all three groups successfully achieved flexion-relaxation. In a chronic disabling occupational lumbar spinal disorder cohort, surgery patients were nearly equal to nonoperated patients in responding to interdisciplinary functional restoration rehabilitation on measures investigated in this study, achieving close to normal performance measures associated with pain-free controls. The responsiveness and final scores shown in this study suggests that flexion-relaxation may be a useful, objective diagnostic tool to measure changes in physical capacity for chronic disabling occupational lumbar spinal disorder patients. Ó 2014 Elsevier Inc. All rights reserved. Keywords:

Chronic disabling occupational lumbar spinal disorder; Flexion-relaxation phenomenon; Surface electromyography; Lumbar surgery; Functional restoration; Interdisciplinary rehabilitation; Decompression; Discectomy; Fusion

Introduction Lumbar flexion-relaxation is a well-known muscular pattern in which lumbar muscles relax completely at maximum voluntary flexion. This flexion-relaxation pattern can be reliably measured in most normal subjects, but is absent in most chronic low back pain (CLBP) subjects [1–12]. Lumbar surface electromyographic measures, in both static and dynamic postures and movements, have been found to be reliable in normal subjects and CLBP subjects, both within and between sessions, and no differences in reliability have been found between nonsurgical CLBP subjects and control subjects [1,9,11–14]. As found in a recent meta-analysis, measures of flexion-relaxation have produced a large effect size (d51.71) in distinguishing between CLBP patients and control subjects [15]. Flexion-relaxation deficits in low back pain subjects have been associated with self-reported disability [10], pain [16–18], and fear of pain and reinjury [19]. As a treatment outcome measure with CLBP subjects, positive treatment changes in flexion-relaxation have been associated with clinical improvement in self-efficacy beliefs, fear avoidance beliefs [20], perceived disability, pain intensity, and ROM [21]. Because it is influenced by both physical and psychological factors, is very good at distinguishing between CLBP and pain-free control subjects, and has been shown to be responsive to treatment, surface EMG (SEMG) measures of flexion-relaxation are a potentially appealing objective measure of CLBP [15]. Different SEMG assessment methods have been used for evaluating flexion-relaxation. Historically, the most common method has been to look at absolute SEMG values at maximum voluntary flexion [2,6,13,22–26]. Many

researchers prefer to use a flexion-relaxation ratio in an attempt to correct for the SEMG impedance created by fatty tissue between the muscle and skin. The most popular flexion-relaxation ratio in the recent scientific literature is to divide the maximum SEMG produced while flexing by the SEMG produced at maximum voluntary flexion [11,15,27]. Previous research by our group has demonstrated that a cutoff score of SEMG # 3.5 mV at maximum voluntary flexion, to determine whether subjects have successfully achieved flexion-relaxation, can be used to distinguish a cohort of chronic disabling occupational lumbar spinal disorder patients with CLBP (also used in this trial) from pain-free control subjects. It has also been demonstrated that abnormal pretreatment flexion-relaxation patterns are responsive to rehabilitation treatment. The majority of chronic disabling occupational lumbar spinal disorder patients entering a functional restoration program fail to demonstrate a normal flexion-relaxation pattern, but completion of the functional restoration treatment program can result in significant improvement in flexion-relaxation at post-treatment [12,21]. More recently, it has been demonstrated that the addition of a SEMG-assisted stretching biofeedback protocol [28,29], designed to teach patients lumbar muscle relaxation during standing trunk end-range flexion, can result in more patients successfully achieving flexion-relaxation post-treatment. Surface EMG-assisted stretching within the functional restoration program can result in normalization of flexion-relaxation in most patients post-treatment, so that their performance is comparable with a pain-free control group [30]. Those patients who continued to demonstrate abnormal flexion-relaxation

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Methods and materials Subjects Context There is evidence to suggest that ability to achieve flexion-relaxation can improve function in patients with chronic low back pain. The authors assessed whether flexion-relaxation can be achieved in chronic low back pain patients who had previous lumbar surgery. Contribution In this cohort study, the investigators found that patients with prior surgery and chronic low back pain had less flexion, more pain, and EMG-detected deficits than nonsurgical patients and normal controls. With structured rehabilitation, however, the prior surgery groups, including those with fusions, were able to improve to levels similar to the nonsurgical and control groups. Implications If the findings can be verified at other centers to confirm generalizability, they suggest that this type of rehabilitation and the improvement in flexion-relaxation might be useful in this difficult population. —The Editors post-treatment, in conjunction with abnormal lumbar flexion ROM measures, reported greater levels of pain and disability [21]. Few previous studies have explored the relationship of prior lumbar surgery to flexion-relaxation. Ambroz et al. [1] and Ahern et al. [14] found no differences between postoperative surgical and nonsurgical patients in dynamic lumbar SEMG measures, including measures of flexion-relaxation, although absolute means at maximum voluntary flexion were not reported. Wallbom et al. [31] measured flexion-relaxation and ROM before and after lumbar discectomy in a group of 17 patients. Despite self-reported improvements in pain, perceived function, and general health, lumbar flexion-relaxation and ROM did not improve 30 days postoperatively [31]. The purpose of the present study was to quantify the effects of prior lumbar surgeries on flexion-relaxation patterns, and the responsiveness of flexion-relaxation to postoperative rehabilitation. We compared chronic disabling occupational lumbar spinal disorder patients with prior spine surgery to those who had received only nonoperative care interventions before the functional restoration treatment program. We studied SEMG, ROM, visual analog scale (VAS) pain self-report, and 1-year treatment outcome measures. As part of the post-rehabilitation comparisons, we noted how close the groups of postoperative and nonsurgical patients came to achieving the ‘‘normal’’ scores produced by a group of pain-free controls without a history of CLBP.

A total of 126 chronic disabling occupational lumbar spinal disorder patients with prior work-related injuries, who entered an interdisciplinary functional restoration treatment program, agreed to enroll in this study, and provided informed consent to participate in functional restoration and to allow their data to be used for research purposes. All subjects had demonstrated a minimum of 4 months of disability since their injuries, and an interdisciplinary evaluation demonstrated significant physical/functional deficits and problems in psychosocial coping. Patient data were collected from November of 2002 to November 2003 and again from March 2005 to March 2006. Patients were included in the study if their compensation claim included a lumbar injury. All chronic disabling occupational lumbar spinal disorder patients participating in the functional restoration program received both SEMG and ROM evaluations; however, outside the study periods, these measures were collected on separate occasions. For the purposes of the present study, in addition to the standard functional restoration evaluation battery [32–34], patients underwent a standardized simultaneous SEMG and inclinometric flexion ROM assessment [12,21,29]. Chronic disabling occupational lumbar spinal disorder patients whose SEMG and ROM evaluations were conducted at separate sessions were not included in the study. Fifty-seven patients who received simultaneous SEMG/ ROM assessments had a history of pre-rehabilitation lumbar surgery. The cohort was broken into three groups based on surgical history: No surgery (n569), decompression or discectomy (n532), and lumbar fusion (n525). At post-treatment, 116 of the original 126 subjects who completed the functional restoration program (no surgery, n565; decompression or discectomy, n530; fusion, n521) participated in an identical SEMG and inclinometric ROM assessment. No significant demographic differences were found between patients with and without a posttreatment assessment. In addition, a group of 30 asymptomatic control subjects was recruited from among the clinic staff and research foundation staff. Email invitations were sent to potential participants, and those who responded to the invitation were evaluated for eligibility. Participants were included in the pain-free control group if they had no history of low back pain over the prior year, no previous low back surgery, and no spinal abnormalities on SEMG assessment. All control subjects provided informed consent to participate in the study, and were evaluated with the same simultaneous SEMG and ROM assessment as the treatment subjects to illustrate ‘‘normal performance’’ on the objective SEMG and ROM measures. Figures 1 and 2 illustrate participant flow through the study. Both the clinical and control samples used in this study have been defined and described

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Fig. 1. Treatment subjects flow chart.

elsewhere (Mayer et al. [21]; Neblett et al. [30]; Neblett et al. [35]). Assessment procedure Surface EMG electrode skin preparation and placement methodology is well-documented in the literature [36]. Silver–silver chloride electrodes from Noromed (1 cm in diameter and spaced 2 cm apart) were placed vertically on the left and right erector spinae muscles at L3, approximately 2 cm from the midline. A root mean square rectified SEMG signal was monitored and displayed in real time to the experimenter, while being recorded by a SEMG biofeedback system (Procomp Plus, Thought Technology, Montreal, Canada). A frequency response of 20 to 500 Hz and an average factor of .5 seconds for signal smoothing, was used during recording. Microvolt levels from the left and right side

electrodes were averaged to obtain a single mean SEMG mV number. All subjects were given standardized instructions, which have been fully documented elsewhere [12,21,30]. Two SEMG readings (maximum SEMG during the flexion movement and approximately 2 seconds of mean SEMG during maximum voluntary flexion), were utilized in the analysis. From these two readings, three measures of flexionrelaxation were determined: The mean absolute root mean square SEMG during maximum voluntary flexion; a ratio of maximum SEMG during flexion to the mean SEMG during maximum voluntary flexion; and a determination of whether the subject had successfully achieved flexionrelaxation with a cut-off score of #3.5 mV. During flexion trials, a physical therapist held inclinometers at T12 and the sacrum and recorded degrees of movement using a standard, two-inclinometer technique, in which pelvic motion

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Fig. 2. Pain-free control subjects flow chart.

(measured from the sacrum) was subtracted from the gross motion (measured from T12) to determine true lumbar motion [37,38]. For those patients with prior lumbar fusion surgeries, a correction of 8
per fused segment, as has been recommended and used in previous studies by our group, was added to both true lumbar and gross motion for comparison to the pain-free control subjects [12,21,30]. Pain was assessed during the forward bending task using a 15-cm VAS, with the anchors ‘‘no pain’’ to ‘‘worst possible pain,’’ converted to a ‘‘0’’ to ‘‘10’’ pain rating. Treatment procedure All patient groups participated in an identical, interdisciplinary, medically directed, functional restoration treatment program, consisting of quantitatively directed progressive exercise supervised by physical and occupational therapists, and guided by serial testing of ROM, strength, and functional capacity [33,39–41]. In addition, the multimodal disability management program promoted pain coping skills, stress management, and occupational reintegration through individual and group education, supportive counseling, and standard biofeedback training. All patients also participated in an SEMG-assisted stretching biofeedback training protocol to teach them how to relax the erector spinae muscles during end-range trunk flexion [28,30]. The number of SEMG-assisted stretching treatment sessions for each patient was determined by how quickly and effectively the patient learned the muscular relaxation skills and achieved a normal flexion-relaxation pattern [29]. At 1 year after discharge from the functional restoration program, patients were contacted for a follow-up interview, either by phone or in person. Using a structured interview format,

socioeconomic outcomes were assessed. These outcomes included work return (if the patient returned to work at any time during the post-discharge year), work retention (if the patient was still working at the time of the interview), health-care utilization (seeking treatment from a new provider or in excess of normal follow-up visits), and new injury or new surgery (during the post-discharge year). Statistical analysis Comparisons between the patient groups were made using univariate ANOVA procedures for continuous variables (such as EMG and ROM measures) and chi-square tests for categorical variables (the yes/no determination of flexionrelaxation). Pairwise comparisons for significant omnibus tests were conducted using the Bonferroni correction for multiple comparisons. The omega squared statistic was used as the measure of effect size for the ANOVAs (small effect, 0.1; medium effect, 0.6; large effect, 0.15), and Cohen’s w was used to measure the effect size of the chisquare tests (small effect, 0.1; medium effect, 0.3; large effect, 0.5) [42,43]. To evaluate pre-to-post changes, a repeated-measures ANOVA procedure was used, with planned contrasts to compare change in each surgery group with change in the no surgery group [43]. A linear regression analysis was used to evaluate the relationship of surgery group to post-rehabilitation measures after adjustment for age, gender, length of disability, and prerehabilitation score on the measure. Surgery groups were dummy coded with the no surgery group as the reference group. Sample size was adequate to detect medium effects, with power b50.80 and a significance level of a50.05. Missing data were treated with listwise deletion.

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Table 1 Demographic characteristics of the lumbar surgery and no surgery groups Lumbar surgery (N557 [45.2%]) Variable Age, mean (SD) Gender (% male) Race (%) Caucasian African American Hispanic Other Length of disability (mo), mean (SD) Surgical levels, n (%) Single Multiple No. of SEMG-assisted stretching sessions Mean (SD) Range

No surgery (N569; 54.8%)

Discectomy or decompression (N532)

Fusion (N525)

p Value

Effect size

46.6 (8.7) 58

44.3 (9.8) 78

49.1 (6.9) 60

.13 .14 .12

u250.02 w50.18 w50.33

62 24 14 0 20.7 (29.1) N/A

59 31 3 7 25 (21.9)

64 20 12 4 39.4 (31.2)

.11 .71

u250.02 w50.11

26 (81) 6 (19)

18 (72) 7 (28) .01

u250.13

2.1 (1.1) 1–4

3.0 (0.6) 2–4

4.0 (1.47)* 2–6

N/A, not applicable; SD, standard deviation; SEMG, surface electromyography. * Different from no surgery group.

Results Demographics for the three patient groups are presented in Table 1. No differences were found among these groups in average age, gender, race, pretreatment length of disability, or extent of surgery before entering treatment. In addition, the effect sizes of the demographics were calculated to ensure that nonsignificant results were not owing to sample size limitations. All of the effect sizes were very small (!0.01) or small (!0.10), except for race. However, the differences in race are representative of the general population in the geographical area where the study was conducted. Therefore, no further adjustments for demographic variables were made. As shown in Table 2, at pretreatment, the no surgery group showed better (lower) absolute SEMG at maximum voluntary flexion relative to the discectomy/decompression group (p5.04) and the fusion group (p5.03). In the comparison of subjects who achieved flexion-relaxation, with a cutoff score of maximum voluntary flexion SEMG #3.5 mV,

significantly fewer subjects in the discectomy/decompression group successfully achieved flexion-relaxation than did subjects in the no surgery group (p!.01). The no surgery group demonstrated a greater (better) SEMG flexionrelaxation ratio compared with the discectomy/decompression group (p5.04). The subjects in the fusion group had lesser gross ROM (p!.01) and lesser true lumbar ROM (p!.01), compared with the no surgery group, and lesser true lumbar ROM than the discectomy/decompression group (p5.03). Pretreatment self-reported pain while bending during the SEMG/ROM testing, using a VAS, was higher in the fusion group than in the no surgery group (p5.03). Table 3 presents a comparison of post-treatment SEMG and ROM among the three patient groups and the pain-free control group tested with an identical protocol. In this comparison, gross ROM and true lumbar ROM were corrected for fused spinal segments by adding 8
per level fused, as suggested in previous studies [12,21,30]. As can be seen, SEMG and ROM measures were similar between the

Table 2 Pre-rehabilitation comparisons between spine surgery and no surgery groups (N5126) Lumbar surgery (N557 [45.2%]) Measure

No surgery (N569 [54.8%])

Discectomy or decompression (N532)

Mean EMG* (mV), mean (SD) Flexion-relaxation achieved (n, %), EMG #3.5 Flexion-relaxation ratio, mean (SD) Gross ROM (
), mean (SD) True ROM (
), mean (SD) Pelvic ROM (
), mean (SD) Pain VAS during test, mean (SD)

8.7 31 7.7 79.7 44.0 35.7 6.3

13.6 5 3.8 68 36.8 31.2 7.3

EMG, electromyogram; SD, standard deviation. * At maximum voluntary flexion. y Different from no surgery group. z Different from discectomy/decompression group.

(8.3) (44.9) (8.5) (24.1) (12.5) (17.2) (2.4)

(10.5)y (15.6)y (4.7)y (23) (14.4)y (14.4) (2.4)

Fusion (N525) 14.2 6 4.3 60 27.5 32.5 7.6

(9.2)y (24) (6.2) (28.1)y (12.3)y,z (21) (1.3)y

p Value

Effect size

.01 .01 .02 !.01 !.01 .43 .01

u250.06 w50.28 u250.05 u250.08 u250.19 u250.06

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Table 3 Post-rehabilitation comparisons among spine surgery and no surgery groups and a pain-free comparison group Lumbar surgery (N551 [44%]) No surgery (N565 [56%])

Measure SEMG* (mV), mean (SD) Flexion-relaxation achieved, n (%), EMG #3.5* Flexion-relaxation ratio, mean (SD) Gross ROM (
), mean (SD) True ROM (
), mean (SD) Pelvic ROM (
), mean (SD) Pain VAS during test, mean (SD)

2.3 (2.6) 61 (93.8) 15.9 111.1 53.5 57.9 4.4

(10.9) (14.3) (8.6) (13.7) (2.5)

Discectomy or decompression (N530) y

4.0 (4.4) 24 (80)y,z 12.7 104.7 50.3 54.4 5.1

(9.4) (17.0) (10.6) (16.7) (2.5)

Fusion (N521) 3.6 (3.2) 17 (81)y 10.5 110.7 53.8 56.9 5.6

(6.8) (15.6) (9.2) (13) (2.1)

Pain-free controls (N530) 2.0 (0.6) 30 (100) 15.1 110.0 53.9 56.0 N/A

(7.7) (11.7) (8.2) (10.0)

p Value

Effect size

.02 .02

u250.05 w50.28

.12 .25 .34 .70 .12

EMG, electromyogram; N/A, not applicable; SD, standard deviation; SEMG, surface EMG; VAS, visual analog scale. Note: In the above table, gross ROM and true ROM are corrected in the surgery groups by 8
per level fused to allow comparison to pain-free control subjects. * At maximum voluntary flexion. y Different from pain-free control group. z Different from no surgery group.

no surgery and pain-free control group. Compared with the no surgery group, the discectomy/decompression group had marginally higher maximum voluntary flexion SEMG (p5.05). Fewer subjects in the discectomy/decompression group achieved flexion-relaxation than in the no surgery or control groups (p5.04 and .01, respectively), whereas fewer subjects in the fusion group successfully attained flexion-relaxation than in the pain-free control group (p5.01). There were no post-treatment differences among the patient groups and the pain-free control group in the SEMG flexion-relaxation ratio and in ROM measures. To better view these results, Figs. 3–6 illustrate the preto-post changes among patient groups on maximum voluntary flexion SEMG, achievement of flexion-relaxation, and ROM measures. The pain-free control group is also presented for comparison to the patient groups. To permit comparison on ROM for patients with fused lower lumbar segments, a ‘‘correction,’’ adding ‘‘normal’’ segmental flexion for the fused level is necessary for both gross and true lumbar ROM. Because mobility is greater in the lower half of the lumbar spine, and the vast majority of spine fusions

for degenerative conditions occur in that zone, a correction of 8
per segment is utilized to ‘‘normalize’’ the uncorrected motion, to more fairly demonstrate the comparison between fusion and other operated or unoperated groups. Figures 3 and 4 (gross ROM and true lumbar ROM) include the corrected and uncorrected (by 8
per spinal level fused) ROM levels for the lumbar fusion group. The three patient groups significantly improved on all SEMG, ROM, and pain VAS measures (p!.01) in response to treatment. Planned contrasts showed that the fusion group demonstrated greater change in maximum voluntary flexion SEMG than the no surgery group (p5.03). Although both surgical groups showed greater absolute improvements than the unoperated group on SEMG and ROM measures, this SEMG comparison between fusion and unoperated group was the only change considered statistically significant (p!.05). Table 4 shows the 1-year socioeconomic outcomes of the three surgery groups. Although there were initial differences in return to work at the 1 year follow-up, with fusion patients less likely to return to work compared with

Fig. 3. Maximum voluntary flexion surface electromyography (mV). Dashed line indicates normal value.

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Fig. 4. Flexion-relaxation achieved. Maximum voluntary flexion surface electromyography#3.5 mV.

unoperated patients; the percentages of patients who retained work were not different among surgery groups. Similarly, there were no differences among the groups in excessive health-care utilization (in excess of normal follow-up), number of visits to new providers, new injuries, or new surgeries. Table 5 contains the adjusted and unadjusted results of the linear regression analysis of the post-rehabilitation measures. The unadjusted regression analysis found that the discectomy/decompression group had higher (poorer) post-rehabilitation SEMG levels compared with the no surgery group. This difference persisted after adjustment for covariates (age, gender, length of disability, and prerehabilitation SEMG levels). The unadjusted analysis showed that the fusion patients had lower (poorer) post-rehabilitation flexion-relaxation ratios, although this difference was no longer significant after adjustment for covariates. Finally, there were no differences among groups in post-rehabilitation ROM measures or pain during bending in either the adjusted or unadjusted regression analysis.

Discussion In general, patients with prior lumbar surgeries entering a functional restoration treatment program at pretreatment demonstrated more limited flexion ROM, more abnormal lumbar SEMG, and reported higher pain while bending than nonsurgical patients. The discectomy/decompression patients had a lower SEMG flexion-relaxation ratio and were less likely to achieve flexion-relaxation (as determined by a SEMG cutoff score of #3.5 mV). Both surgery groups demonstrated higher absolute SEMG levels during maximum voluntary flexion compared with the no surgery group. The fusion patients had reduced gross lumbar flexion and greater pain during bending compared with the no surgery patients, and reduced true lumbar flexion compared with the discectomy/decompression patients. At post-rehabilitation, there were still small but significant differences among the surgery and no surgery groups on maximum voluntary flexion SEMG and on the ability to achieve flexion-relaxation. However, there were no post-treatment

Fig. 5. Gross ROM (
). Dashed line indicates normal value.

900

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Fig. 6. True lumbar ROM (
). Dashed line indicates normal value.

found conflicting results regarding the efficacy of surgery (both fusion and discectomy, particularly in occupational injury claims) in comparison to nonoperative treatment [45–48]. A 2006 study of Washington State Worker’s Compensation patients found that 64% of patients receiving lumbar fusions remained disabled 2 years after surgery [49]. However, in the present study, after treatment with functional restoration, the majority of patients in both the surgical and nonsurgical groups demonstrated substantial recovery. Upon completing the treatment program, the surgical groups performed almost as well, or just as well as the no surgery group on the clinical measures studied herein. Other evidence of the success of the treatment program can be seen in the comparison of the surgical and nonsurgical patients with pain-free control subjects. At the end of treatment, both the surgical and nonsurgical groups were indistinguishable from pain-free control subjects on measures of ROM. Although there were significant differences in absolute SEMG levels and ability to achieve flexionrelaxation, these differences were relatively small. As determined with a maximum voluntary flexion SEMG, the no-surgery group reached normal levels (M52.3 mV), and the discectomy/decompression group and fusion groups

differences in ROM, pain, or flexion-relaxation ratios. All groups came extremely close to achieving levels of SEMG and ROM measures characteristic of pain-free controls, after rising from significant deficits before treatment. Furthermore, the fusion group demonstrated significantly greater improvement in SEMG measures than did the no surgery group (61% vs. 41% decrease [ie, improvement] from pre-to-post treatment). Therefore, the responsiveness of these objective measures of flexion-relaxation offer great promise in documenting progress for chronic disabling occupational lumbar spinal disorder patients attending a functional restoration program. In evaluating socioeconomic outcomes approximately 1 year after completing the treatment program, fusion patients were less likely to return to work compared with unoperated patients (72.7% vs. 96.7%, respectively). However, there were no significant differences among the three groups in the percentage of patients who retained work, in excessive health-care utilization (in excess of normal follow-up), number of visits to new providers, new injuries, or new surgeries. There has recently been a great deal of criticism of the increased use of spinal surgery for chronic disabling occupational lumbar spinal disorder patients [44]. Many studies have

Table 4 Comparison of 1-year socioeconomic outcomes among spine surgery and no surgery groups (N5108) Lumbar surgery (N547) Measure

No surgery (N560)

Discectomy or decompression (N526)

Fusion (N522)

p Value

Effect size

Work return, n (%) Work retention, n (%) Excessive health-care utilization, n (%) Visits to new health-care providers, mean (SD) New injuries, n (%) New surgeries, n (%)

58 45 10 1.0 1 0

23 21 7 2.4 0 0

16 14 6 2.0 0 1

.006 .275 .387 .398 .669 .167

w5.306

SD, standard deviation. * Different from no surgery group.

(96.7) (81.8) (18.2) (2.6) (1.9)

(88.5) (84) (31.8) (6.5)

(72.7)* (66.7) (27.3) (6.4) (4.5)

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Table 5 Unadjusted and adjusted regression coefficients for prediction of post-rehabilitation measures Unadjusted analysis Measure SEMG (mV) Discectomy/decompression Fusion Model Flexion-relaxation ratio Discectomy/decompression Fusion Model Gross flexion (
) Discectomy/decompression Fusion Model Pelvic flexion (
) Discectomy/decompression Fusion Model True lumbar flexion (
) Discectomy/decompression Fusion Model Pain during test (VAS) Discectomy/decompression Fusion Model

B

SE 1.7 1.3

0.7 0.8

Adjusted analysis t

F

2.2 2.5

3.4 3.8

3.2 3.6

4.3 4.9

2.0 2.3

5.9 1.9

0.7 1.2

0.5 0.6

2.1 0.7

3.6 3.9

3.2 3.6

4.4 1.3

2.2 2.3

0.2 0.3 .04

0.6 0.7

6.4**

.10

2.6

.04

1.9

.03

0.3

.01

2.8

.05

0.2

.003

1.6 0.5

0.6 0.2

2.0 0.5

.02

1.3 1.9

R2

1.8 1.9

.01

1.6 0.2

2.1

2.4 2.6

F 3.5** 1.5

.03

1.1 0.3

1.4

0.6 0.7

t

.05

1.9 0.1

0.60 3.2 0.3

SE

.06

1.4 2.1*

1.9 3.5 1.0

B 2.2 1.0

2.6 6.4 0.4

R

2.4* 1.6 3.3*

3.2 5.4

2

0.4 0.5

Note: The no pre-rehabilitation surgery group is the reference group. Negative coefficients indicate that the surgery patients had lower scores than the reference group. A correction of 8
per spinal level fused was applied to gross and true lumbar ROM. Adjusted analysis includes the following covariates: Age, gender, length of disability, and pre-rehabilitation measure. F and R2 statistics for the adjusted analysis represent the change statistics associated with the addition of surgery groups to the regression model. *p!.05; **p!.01.

came very close to normal (M54.0 mV and 3.6 mV, respectively) at post-treatment. The present study has similar limitations to any other cohort study. Because the surgery groups were determined based on prior history and not randomly assigned, the potential for selection bias exists. In addition, only patients being treated for work-related lumbar spine injuries in an intensive, interdisciplinary rehabilitation setting were included in the study. Therefore, the results may not generalize to patients with non–work-related injuries or to those being treated in less intensive treatment programs. In conclusion, chronic disabling occupational lumbar spinal disorder patients with lumbar surgeries related to their workers’ compensation claims can present greater treatment challenges than nonsurgery patients. Despite the fact that surgery patients in the present study demonstrated larger pretreatment SEMG and ROM deficits, and that fusion patients reported greater pain while bending than no surgery patients, both surgery and no surgery groups demonstrated substantial and statistically similar improvement on each outcome measure. After treatment, both surgical groups and the no surgery group achieved ROM comparable with a pain-free control group after correction for fused spinal segments, and the majority of patients in all three treatment groups successfully achieved flexion-relaxation.

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