Abstract
Purpose
The influence of individual factors on patient-reported outcomes is important in the interpretation of disability and treatment effectiveness. The purpose of this study was to assess how physical impairments, psychosocial factors, and life style habits were associated with neck disability based on the Neck Disability Index (NDI), in patients with cervical radiculopathy scheduled for surgery.
Methods
This cross-sectional study included 201 patients (105 men, 96 women; mean age 50 years). Data included self-reported measures and a clinical examination. Multiple linear regressions were performed to identify significant influencing factors.
Results
Pain, physical impairments in the cervical active range of motion, low self-efficacy, depression, and sickness-related absences explained 73 % of the variance in NDI scores (p < 0.001).
Conclusion
Assessments of physical impairments and psychosocial factors in patients with cervical radiculopathy could improve the description of neck disability and the interpretation of treatment outcomes in longitudinal studies.
Keywords: Cervical spine, Radiculopathy, Neck Disability Index, Individual factors, Multiple regression analysis
Introduction
The effects of surgery on patients with cervical radiculopathy caused by disc disease vary from good to fair depending on the outcome measures used [1–5]. Recently, patient-reported outcome measures that integrate the patient’s perspective on disability and functioning have increasingly become the standard for evaluating treatment effectiveness in spine surgery [6].
The Neck Disability Index (NDI) is recommended for patients with cervical radiculopathy [7], and studies have shown that patients reported residual neck disability after surgery [2, 4]. Other predictor studies have reported that preoperative patient-reported neck disability scores on the NDI were important for the outcome of surgery in patients with cervical radiculopathy [8–10]. However, patient-reported outcomes integrating several domains are complex to interpret, and few proposals have been offered on how to implement those results into clinical practice [8, 9].
A better understanding of how individual factors influence patient-reported disability outcomes is needed as this influence may be critical in the interpretation of disability scores and evaluation of treatment effectiveness. No study has addressed this issue in patients with cervical radiculopathy scheduled for surgery.
The aim of the present study was to assess how physical impairments, psychosocial factors, and life style habits might be associated with patient-reported neck disability in patients with cervical radiculopathy scheduled for surgery.
Materials and methods
Design and participants
This study was a cross-sectional analysis of baseline data from patients with cervical radiculopathy scheduled for surgery. Patients were recruited at four Hospitals in Sweden, between 2009 and 2012, to participate in a prospective, randomized clinical trial designed to compare two postoperative rehabilitation interventions. Inclusion criteria were age 18–70 years, cervical radiculopathy symptoms for a minimum of 2 months, and concordant nerve root compression visualized on magnetic resonance imaging (MRI). Exclusion criteria were previous cervical surgery, a previous fracture or luxation of the cervical spine, myelopathy, malignancy or spinal tumor, systemic disease, diagnosis of fibromyalgia or generalized myofascial pain, persistent or recurrent severe back pain, diagnosed psychiatric disorders, alcohol or drug addiction, and lack of familiarity with the Swedish language. The study was approved by the regional ethical review board (Dnr-M126-08). After providing informed consent, a total of 201 patients were included (Table 1). Data were collected from a questionnaire that included patient-reported measures and a clinical examination performed on the day before surgery by four trained physiotherapists, one at each of the four hospitals.
Table 1.
Descriptive data for patients with cervical radiculopathy scheduled for surgery (n = 166–201)
| n | Scores | Ranges | |
|---|---|---|---|
| Demographic variables | 201 | ||
| Male sex, n (%) | 105 (52) | ||
| Age (years) (mean, SD) | 50 (8.4) | 22–70 | |
| Height (cm) (mean, SD) | 174 (8.9) | 152–195 | |
| Weight (kg) (mean, SD) | 81 (15.0) | 50–125 | |
| Body mass index (kg/m2) (mean, SD) | 27 (3.9) | 19–38 | |
| Right hand dominant, n (%) | 188 (95) | ||
| Unilateral symptoms, n (%) | 176 (92) | ||
| Dependent variable | |||
| Neck Disability Indexa (NDI, 0–100 %) (mean, SD) | 189 | 43 (15.3) | 4–84 |
| Independent variables | |||
| Physical impairments | |||
| Pain and symptoms | |||
| Mean intensity of neck pain past week (mm) VAS (mean, SD) | 195 | 55 (21.8) | 0–100 |
| Mean intensity of arm pain past week (mm) VAS (mean, SD) | 191 | 50 (24.7) | 0–99 |
| Mean intensity of headache past week, (mm) VAS (mean, SD) | 193 | 27 (25.5) | 0–100 |
| Duration of neck pain (months) (mean, SD) | 173 | 32 (44.6) | 0–288 |
| Duration of arm pain (months) (mean, SD) | 166 | 27 (40.0) | 0–288 |
| Daily neck pain, n (%) | 194 | 177 (91) | |
| Daily arm pain, n (%) | 192 | 160 (83) | |
| Daily headache, n (%) | 190 | 64 (34) | |
| Daily hand numbness, n (%) | 192 | 156 (81) | |
| Daily hand weakness, n (%) | 186 | 118 (63) | |
| Daily neck stiffness, n (%) | 191 | 157 (82) | |
| Daily dizziness/unsteadiness, n (%) | 193 | 40 (21) | |
| Clinical examination | |||
| Cervical range of motion in the sagittal plane, (°) (mean, SD) | 198 | 83 (26.7) | 17–160 |
| Cervical range of motion in the transversal plane, (°) (mean, SD) | 198 | 100 (25.5) | 7–175 |
| Cervical range of motion in the frontal plane, (°) (mean, SD) | 198 | 55 (17.8) | 14–120 |
| Imbalance in hand-strength, % (mean, SD) | 196 | 26 (23.1) | 0–100 |
| Ventral neck muscle endurance in men, (s) (median, IQR) | 100 | 45 (75) | 0–300 |
| Ventral neck muscle endurance in women, (s) (median, IQR) | 92 | 22 (27) | 0–135 |
| Dorsal neck muscle endurance in men, (s) (median, IQR) | 99 | 71 (135) | 0–757 |
| Dorsal neck muscle endurance in women, (s) (median, IQR) | 92 | 29 (54) | 0–390 |
| Impairment in sensibility, n (%) | 191 | 165 (85) | |
| Impairment in motor function, n (%) | 191 | 150 (78) | |
| Asymmetry in reflexes, n (%) | 191 | 103 (57) | |
| Psychosocial factors | |||
| Attitudes and beliefs | |||
| Self-Efficacy Scalea (scale 0–200) (median, IQR) | 188 | 128 (56) | 22–200 |
| Pain catastrophizing (scale 0–36) (median, IQR) | 191 | 13 (12) | 0–33 |
| Control over pain (scale 0–6) (median, IQR) | 191 | 3 (1) | 0–6 |
| Ability to decrease pain (scale 0–6) (median, IQR) | 191 | 2 (2) | 0–6 |
| High recovery expectations, n (%) | 195 | 187 (96) | |
| Low satisfaction with symptoms, n (%) | 195 | 186 (95) | |
| Emotional responses | |||
| Depressiona (Modified Zung Scale 0–69) (median, IQR) | 194 | 25 (12) | 4–57 |
| Somatic anxietya (Modified Somatic Perception Questionnaire 0–39) (median, IQR) | 195 | 7 (7) | 0–23 |
| Social factors | |||
| Sickness-related absences (partial or full) due to arm/neck symptoms, n (%) | 181 | 100 (55.2) | |
| Perceived support from relatives, n (%) | 191 | 167 (87) | |
| Life style habits | |||
| Smoking yes, n (%) | 194 | 49 (25) | |
| Physically active, n (%) | 195 | 96 (49) | |
VAS visual analog scale, IQR interquartile range
aTransformation score: when no more than one item in the NDI or SES, and two items in the Modified Zung Scale or the Modified Somatic Perception Questionnaire were missing, it was replaced by the average score of all other items on the questionnaire for that patient
Neck disability outcome
The primary outcome was patient-reported neck disability evaluated with the NDI [11]. Ten items were measured including pain intensity, personal care, lifting, sleeping, driving, recreation, headaches, concentration, reading, and work. Items were scored 0–5, and scores were summed to a total score, expressed as a percentage. Higher scores represented a higher degree of neck disability (Table 1).
Physical impairments
Pain and symptoms
Pain intensity was measured with a visual analog scale (VAS) ranging from 0 (no pain) to 100 mm (unbearable pain) [12]. Average neck pain, arm pain, and headache were based on the patient rating of their maximal and minimal pain intensity during the past week (Table 1). Duration of neck and arm pain was reported in months (Table 1). The symptom frequencies for neck pain, arm pain, headache, hand numbness, hand weakness, neck stiffness, and dizziness/unsteadiness were assessed on a 5-point scale from 1 (never) to 5 (constant symptoms). Scores were dichotomized into occasional (1–2) or daily symptoms (3–5) (Table 1).
Clinical examination
The neurologic examination included a bilateral assessment of sensibility with a pin prick and a light touch in dermatomes C4−C8; motor function was assessed with manual muscle testing of the C4−C8 myotomes; and reflexes for C5, C6, and C7 were tested with a standard reflex hammer [13]. Any abnormal response or asymmetry in at least one of the tested dermatomes, myotomes, or reflexes was classified as an impairment or asymmetry in sensibility, motor function, or reflexes (Table 1). Bilateral hand grip strength was measured in kilogram with a Jamar isometric hydraulic hand dynamometer (Sammons Preston, Inc., Bolingbrook) [2]. The percentage difference (imbalance) in hand grip strength between sides was estimated (Table 1).
The cervical active range of motion (AROM) was measured in the sagittal, transversal, and frontal planes of movement with a cervical range of motion (CROM) device (Performance Attainment Associated, Roseville, MN) [2] (Table 1).
Neck muscle endurance (NME) was evaluated in the supine position for the cervical anterior muscles and in the prone position for the cervical posterior muscles with a 2 kg weight for women and a 4 kg for men [3, 14]. Patients loaded their neck in the standardized positions and time was reported in seconds (Table 1).
Psychosocial factors
Patient attitudes and beliefs
Three subscales of the Swedish version of the Coping Strategy Questionnaire [15] were used to assess the patient’s current use of coping strategies. The pain catastrophizing subscale (CAT-CSQ; scores 0–36) [16] evaluated the use of negative thinking as a reaction to pain; higher scores represented higher levels of pain catastrophizing. The two other subscales (scores 0–6) evaluated the patient’s belief in their control over pain and their ability to decrease pain; higher scores represented more perceived control over pain and ability to decrease pain (Table 1).
Self-efficacy was measured with the Self-Efficacy Scale (SES; total score 0–200) [17] which comprised a patient’s self-rating of how confident they felt about performing 20 daily activities, despite their pain (scale: 0 = not at all confident; 10 = very confident). Lower scores represented low confidence in performing activities (Table 1).
Recovery expectation [18] was measured on a 4-point scale (1 = expected to be completely restored to 4 = no expectations of recovery or relief); these answers were dichotomized into high (1–2) and low (3–4) recovery expectations (Table 1).
Symptom satisfaction [19] was assessed with the question: “How would you feel about having your current symptoms for the rest of your life?”, on a 7-point scale (1 = delighted to 7 = terribly unhappy); these answers were dichotomized into high (1–3) and low (4–7) symptom satisfaction (Table 1).
Emotional responses
Depression was evaluated with the Modified Self-rating Depression Scale (Zung) [20], which included 23 items and scores of 0–69; higher scores were indicative of depressed moods (Table 1).
Somatic anxiety was evaluated with the Modified Somatic Perception Questionnaire (MSPQ) [21], which included 22 items and scores of 0–39; higher scores were indicative of a higher level of somatic anxiety (Table 1).
Social factors
Perceived support from relatives and sickness-related absences (full or partial) due to arm/neck symptoms were assessed on a yes/no scale (Table 1).
Life style habits
Smoking was recorded as yes/no. Patients were also asked to report their daily physical activity and weekly habits of exercise, sports, and open-air activities during the preceding 12 months. Answers to these questions were combined and interpreted on the basis of a 4-point scale (1 = inactivity to 4 = high activity) [14]. Then, scores were dichotomized into physically active (3–4), or physically inactive (1–2) (Table 1).
Statistical methods
Descriptive data for the study population were presented as means and standard deviations, medians and interquartile ranges, or proportions (Table 1). When no more than one item was missing in the NDI or SES, and two items in the Zung or MSPQ, the values were substituted with transformed scores; otherwise participants were excluded from the analysis (Table 1). The study of the associations of the independent variables with Durbin–Watson values, variance inflation factors, and tolerances suggested no multicollinearity and that the assumptions of independent errors were met [22]. Variables were arbitrarily grouped and exploratory stepwise linear regressions were conducted to assess associations between NDI scores and variables relating to pain and symptoms, clinical examination, patient’s attitudes and beliefs, emotional responses, social factors, and lifestyle habits, after controlling for the influences of sex and age [23]. The adjusted coefficient of determination (adj. R2) was used to compare models. Significant factors (p < 0.05) were presented with B coefficients, standard errors, and p values (Table 2). The final model included all the factors identified in the first step and was based on 156 participants. Beta coefficients were presented to compare the influence between factors (Table 3). Analyses were performed with the IBM SPSS statistics 20 program.
Table 2.
Factors associated with the Neck Disability Index score in patients with cervical radiculopathy scheduled for surgical intervention
| B | Std error | p value | Adj. R 2 | |
|---|---|---|---|---|
| Pain and symptoms a (n = 184) | 0.56 | |||
| Constant | 22.30 | 5.72 | ||
| Daily dizziness/unsteadiness | 8.13 | 1.93 | <0.001 | |
| Daily neck pain | 6.60 | 2.95 | 0.03 | |
| Mean intensity neck pain (past week) | 0.25 | 0.04 | <0.001 | |
| Mean intensity headache (past week) | 0.22 | 0.03 | <0.001 | |
| Clinical examination a (n = 179) | 0.15 | |||
| Constant | 78.64 | 8.54 | ||
| Cervical range of motion in the transverse plane | −0.12 | 0.04 | 0.004 | |
| Neck muscle endurance in flexion | −0.09 | 0.02 | <0.001 | |
| Attitudes and beliefs a (n = 177) | 0.54 | |||
| Constant | 68.23 | 7.84 | ||
| Low satisfaction with symptoms | 13.01 | 3.91 | 0.001 | |
| Pain Catastrophizing (CSQ-CAT) | 0.25 | 0.11 | 0.02 | |
| Self-Efficacy Scale | −0.23 | 0.02 | <0.001 | |
| Emotional responses a (n = 186) | 0.37 | |||
| Constant | 27.39 | 6.66 | ||
| Depression (Modified Zung Scale) | 0.71 | 0.12 | <0.001 | |
| Somatic anxiety (Modified Somatic Perception Questionnaire) | 0.63 | 0.22 | 0.006 | |
| Social factors a (n = 173) | 0.14 | |||
| Constant | 53.84 | (7.16) | ||
| Sickness-related absences due to arm/neck symptoms | 9.84 | 2.10 | <0.001 | |
Significant variables (p < 0.05) after controlling for the influence of age and sex are presented with B coefficients (B), standard errors (SE) and p values. The models showed p < 0.001: results are presented with the adjusted R 2 (adj. R 2)
aResidual scatter-plots and normal probability plots did not reveal evidence of violated assumptions
Table 3.
Final model of factors associated with the Neck Disability Index score (R 2 = 0.73; p < 0.001) in patients with cervical radiculopathy scheduled for surgery (n = 156)
| B | SE | β | p values | |
|---|---|---|---|---|
| Constant | 44.43 | 8.07 | ||
| Demographic variables | ||||
| Age | – | – | ns | |
| Sex | – | – | ns | |
| Pain and symptoms | ||||
| Daily neck pain | 6.93 | 2.51 | 0.14 | 0.007 |
| Daily dizziness/unsteadiness | 6.50 | 1.90 | 0.17 | 0.001 |
| Mean intensity neck pain (past week) | 0.14 | 0.04 | 0.20 | 0.001 |
| Mean intensity headache (past week) | 0.13 | 0.03 | 0.22 | <0.001 |
| Clinical examination | ||||
| Cervical range of motion in the transverse plane (°) | −0.06 | 0.03 | −0.10 | 0.03 |
| Neck muscle endurance in flexion | – | – | – | ns |
| Attitudes and beliefs | ||||
| Self-Efficacy Scale | −0.13 | 0.02 | −0.34 | <0.001 |
| Pain Catastrophizing (CSQ-CAT) | – | – | – | ns |
| Low satisfaction with symptoms | – | – | – | ns |
| Emotional responses | ||||
| Depression (Modified Zung Scale) | 0.27 | 0.10 | 0.18 | 0.01 |
| Somatic anxiety (Modified Somatic Perceived Questionnaire) | – | – | – | ns |
| Social factors | ||||
| Sickness-related absences due to arm/neck symptoms | 3.71 | 1.40 | 0.13 | 0.009 |
Significant factors (p < 0.05) are presented with B coefficients (B), standard errors (SE), Beta coefficients (β) and p values
Residual scatter-plots and normal probability plots did not reveal evidence of violated assumptions
Results
Physical impairments associated with higher NDI scores included daily neck pain, daily dizziness/unsteadiness, high intensity of neck pain, and headache scored on the VAS (p < 0.001, R2 = 0.56); reduced cervical AROM in the transversal plane, and NME in flexion (p < 0.001, R² = 0.15) (Table 2). Psychosocial factors associated with higher NDI scores included low score on the SES, low symptom satisfaction, high pain catastrophizing (p < 0.001, R2 = 0.54); depressed moods and somatic anxiety as scored on the Zung and the MSPQ (p < 0.001, R2 = 0.37); and sickness-related absences due to arm/neck symptoms (p < 0.001, R2 = 0.14) (Table 2). Life style habits were not associated with NDI scores. The final model included both physical impairments and psychosocial factors and explained 73 % (p < 0.001) of the variation in NDI scores. Score on the SES emerged as the strongest factor (Table 3).
Discussion
This study showed that some physical impairments and psychosocial factors including pain, impairments in the cervical AROM, low self-efficacy, depression, and sickness-related absences were associated with NDI scores in individuals with cervical radiculopathy scheduled for surgery, but not sex or age. Our model explained 73 % of the variance in NDI scores; this may be regarded as a strong model. The results may be related to the number and spread of the variables included in the analysis, as well as the explorative approach. In comparison, another model for patients with chronic neck pain explained only 37 % of the variance in NDI scores [23].
The independent variables included in the analysis were selected based on the results of previous studies in patients with cervical radiculopathy [3, 8, 9] and chronic neck pain [23, 24]. Our results highlighted the importance of the factors identified for explaining neck disability in patients with cervical radiculopathy; moreover, they highlighted the quality of the NDI for integrating a broad patient perspective. Thus, the quantification of physical impairments and psychosocial factors associated with NDI scores improved the description of neck disability in patients with cervical radiculopathy.
We showed that depressed moods scored with the Zung were significantly associated with NDI scores of patients with cervical radiculopathy. Psychological distress was previously reported to remain unchanged after surgery [2], and it was considered a predictor of poor outcome [8]. Moreover, psychological distress was suggested to have a confounding effect on the interpretation of NDI scores in individuals with neck pain; this gave rise to questions regarding the validity and sensitivity of the NDI for evaluating treatment effectiveness [25]. It was suggested that treatment effectiveness might be evaluated more objectively by basing it solely on changes in NDI items that related to activity limitations and participation restrictions [25]. Similarly, our results suggested that depressed moods may have a confounding effect on NDI scores in patients with cervical radiculopathy. Therefore, we recommend that patients with cervical radiculopathy should be assessed for depression to improve interpretations of disability and treatment effectiveness in longitudinal studies.
In the present study, score on the SES emerged as the strongest factor associated with NDI scores; this was similar to results from patients with chronic neck pain [24]. However, the validity and reliability of the SES have not been assessed for patients with cervical radiculopathy; therefore, our results should be interpreted with caution. Pain and physical impairments in cervical AROM were associated with NDI scores; this was consistent with results from other studies [23]. NME in flexion correlated with score on the SES; therefore, it did not remain in the final model. Future studies should consider the possibility of designing rehabilitation approaches that effectively address physical impairments in cervical AROM and low self-efficacy. Furthermore, future studies should investigate the clinical implications of goal-oriented rehabilitation interventions for reducing neck disability and improving outcomes in patients with cervical radiculopathy.
In the present study, sex, age, and levels of pain and disability for the sample were comparable to those in other longitudinal studies on patients with cervical radiculopathy scheduled for surgery [2, 9]. However, a selection bias cannot be excluded due to the specific study criteria. A major strength of this study was the broad perspective of independent variables included in the regression analysis. Furthermore, an explorative approach was used to identify the most relevant model. On the other hand, the study had some limitations. We could not include factors related to radiological findings in the analysis [9], because they were not available. Also, the cross-sectional design did not allow consideration of cause-and-effect relationships between variables. The final model included 14 variables with a sample size of 156 subjects and might be questioned. However, examination of the residuals suggested that the model had not been overfit and was considered stable.
Conclusion
This study showed that some physical impairments and psychosocial factors including pain, impairments in the CROM, low self-efficacy, depression, and sickness-related absences were independently associated with neck disability in patients with cervical radiculopathy scheduled for surgery. These factors explained 73 % of the variance in NDI scores. The description of neck disability and interpretations of treatment effectiveness in longitudinal studies on cervical radiculopathy would improve with a broader assessment of patients that includes both measures of physical impairments and psychosocial factors. Future studies should consider designing rehabilitation strategies that effectively address physical impairments and psychosocial factors associated with neck disability, and investigate the clinical implications of those strategies on outcomes for patient with cervical radiculopathy.
Acknowledgments
The authors acknowledge financial support from The Swedish Research Council, The Swedish Society of Medicine, and the Medical Research Council of Southeast Sweden, and thank Henrik Magnusson and Karl Wahlin at the University of Linköping in Sweden for their help with the statistics.
Conflict of interest
None.
References
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