PREDICTIVE FACTORS FOR 1-YEAR OUTCOME OF LOW-BACK AND NECK PAIN IN PATIENTS TREATED IN PRIMARY CARE: COMPARISON BETWEEN THE TREATMENT STRATEGIES CHIROPRACTIC AND PHYSIOTHERAPY
 
   

Predictive Factors for 1-year Outcome of Low-back and Neck Pain
in Patients Treated in Primary Care: Comparison Between
the Treatment Strategies Chiropractic and Physiotherapy

This section is compiled by Frank M. Painter, D.C.
Send all comments or additions to:
   Frankp@chiro.org
 
   

FROM:   Pain. 1998 (Aug);   77 (2):   201–207 ~ FULL TEXT

Elisabeth I. Skargrena,, Birgitta E. O¨ berg

Department of Neuroscience and Locomotion,
Physiotherapy, Faculty of Health Sciences,
Linköping University, Sweden.



The inability to predict outcome in patients with low back/neck pain leads to inappropriate or unnecessary treatment. The aims of the study were to identify prognostic factors for disability at 1-year follow-up in patients with back pain visiting primary care, and to compare the effect of these in two treatment strategies--chiropractic and physiotherapy. Data were taken from a randomised trial on patients with back/neck pain visiting the general practitioner, in which patients were allocated to chiropractic and physiotherapy as primary management. Three hundred and twenty-three patients, aged 18-60 years, who had no contraindications to manipulation and who had not been treated within the previous month were included in the study. Multiple regression analysis was used to identify prognostic factors. Dependent variables were mean Oswestry score and mean change in Oswestry score at 12-month follow-up. The multiple regression analysis revealed five significant (P < 0.001-0.01) prognostic factors; duration of current episode, Oswestry score at entry, expectations of treatment, number of localisations, and well-being. Besides, the regression coefficients for the significant factors were compared between the two treatment strategies.

No significant difference in effect or regression coefficients for the prognostic factors were seen between the two treatment strategies. Twelve per cent of the patients had poor prognostic factors (duration > or = 1 month, more than one localisation, low expectations of treatment and low well-being) at entry. These patients had a mean Oswestry score above 20% at 1-year follow-up. Clinical decision models for the management of patients with back pain visiting primary care that consider prognostic factors need to be implemented and prospectively evaluated.

KEYWORDS:   Chiropractic; Low back pain; Neck pain; Oswestry score; Physiotherapy; Predictors



From the FULL TEXT Article:

Introduction

Back pain is a common problem in primary care and a major cause of disability and loss of work. Physicians have difficulty in choosing treatment forms and predicting which of the patients will get better and which will go on to suffer chronic back pain. One reason for the difficulties is the fact that in most cases we cannot establish an organic cause (Waddell, 1987; Frymoyer, 1988), so, mostly, back pain is ‘an illness looking for a disease’. Another reason is shown by a number of systematic reviews of the quality of studies concerning interventions for low back pain (Koes et al., 1996; Tulder van et al., 1997) and neck pain (Hurwitz et al., 1996; Kjellman et al., unpublished data). These showed that the effectiveness of many interventions available for treating back pain has not yet been demonstrated beyond doubt. The quality of design, execution and reporting need to be improved to establish evidence concerning effectiveness. One important aspect of design is the study population. A homogeneous study population enhance the possibility of seeing similarities or differences better when comparing treatments. A heterogeneous population can be regarded as consisting of several more homogenous subgroups of patients, where the effect varies among the subgroups. A systematic review of randomised studies of spinal manipulation for low back pain showed that 29 out of 36 studies did not fulfil the criteria for homogeneity (0–1 points out of two possible) (Koes et al., 1996). A similar systematic review of chiropractic spinal manipulation showed that one out of eight studies fulfilled the criteria for homogeneity (Assendelft et al., 1996).

In a recently presented randomised study we compared chiropractic and physiotherapy treatment in the management of patients with low back and neck pain (Skargren et al., 1997) Inclusion criteria were all patients between 18–60 years of age who visited a general practitioner in primary care for low back or neck pain. The comparison between the two groups showed similar results in effectiveness and costs after treatment and at 6- and 12- month follow-up. Our study population was heterogeneous in cause, length of duration, etc. Therefore, subgroup analysis was performed in more homogenous subgroups (Skargren et al., 1998). The subgroupings were chosen according to previous studies (Postacchini et al., 1988; Meade et al., 1990) ‘similar problems during the previous 5 years’, ‘duration of current episode’ (£1 week, 1–4 weeks, ³1 month) and level of ‘Oswestry disability score at entry’ (,40%, ³40%). Our subgroup analyses showed that patients with acute problems (duration of current episode ,1 week) benefited more from chiropractic than physiotherapy, whereas patients with pain that had lasted for ³1 month gained more from physiotherapy (Skargren et al., 1998). The study generated several questions about the choice of study population in research and what prognostic factors that are essential for the choice of treatment and the prediction of outcome in clinical praxis. The latter is essential knowledge also as a base for decisions of the future structure and organisation of the management of patients with back pain. Leboeuf-Yde et al. (1997) have also pointed out the importance of subgrouping patients with back pain to support the choice of treatment and scientific evidence of treatment. To be able to form more homogenous subgroups we have to know which are the potential factors for the course of back pain. A number of studies on prognostic factors for the course of low back pain have been conducted in primary care (Pedersen, 1981; Roland and Morris, 1983; Chavannes et al., 1986; Singer et al., 1987; Lanier and Stockton, 1988; Von Korff et al., 1993; Coste et al., 1994; Burton et al., 1995; Klenerman et al., 1995; Cherkin et al., 1996; Hoogen van den et al., 1997), but the results vary considerably.

The aims of this study were to identify prognostic factors for disability at 1-year follow-up of patients with back pain visiting primary care, and to compare the effect of these in two treatment strategies – chiropractic and physiotherapy.



Methods

      Study design

The data for the study to be described were taken from a prospective clinical trial in which patients who visited a general practitioner for low back and/or neck pain were randomised to chiropractic or physiotherapy. Patients were included from 10 primary care centres of different size in a medium-sized Swedish county. Patients was followed by questionnaires. Ninety-eight percent completed the 12-month follow-up.

      Study sample

The study comprised patients between 18 and 60 years of age who attended a general practitioner for low back or neck problems. The main criteria for eligibility were that the patients had not received active treatment for their problems within the previous month and had no contraindication to manipulation. Other criteria for eligibility were that they had no other disease, were able to read and write in Swedish and, finally, had problems relevant to chiropractic and physiotherapy treatment. In total 323 patients participated in the trial; 179 in the chiropractic group and 144 in the physiotherapy group. A more careful description of reasons for exclusion and withdrawal has been presented previously (Skargren et al., 1997).

      Independent variables

Baseline data were collected by questionnaire after randomisation. Sociodemographic variables were; age, sex, life style factors such as smoking, and exercise habits, job satisfaction, similar problems the previous 5 years (no/yes), duration of current episode (£1 week, 1–4 weeks, 1–3 months, ³3 months), and expectations of treatment on a four-point scale (completely restored, quite improved, partial relief, no expectations of being restored, or getting relief).

Variables describing the severity of problems were different aspects of perceived pain, function and general health.

Measures for pain were: pain intensity on a visual analogue scale (VAS in mm) (Scott and Huskinsson, 1976), pain frequency on a five-point scale and a pain drawing (Ransford et al., 1976); from the latter the number of localisation’s (neck, thoracic, lumbar) were estimated. Measures for function were; sick-leave and the Oswestry low back pain disability questionnaire. The result of the Oswestry score is expressed on a scale ranging from 0% (no pain or difficulties) to 100% (highest score for pain or difficulty on all items) (Fairebank et al., 1980). General health was followed with a six-point scale concerning well-being, and on a VAS (in mm) with the endpoints: 0, best imaginable, and 100, worst imaginable general health.

Localisation of the cause of treatment and degree of pain radiation was reported by the general practitioner.

      Interventions

Each patient’s treatment was at the discretion of the individual chiropractor or physiotherapist. The mean number of treatment sessions (±SD) during the treatment period was lower in the chiropractic group 4.9 (2.0) than in the physiotherapy group 6.4 (5.4); the difference (95% CI) was -1.53 (-2.38; -0.68). The mean time for the treatment period was somewhat longer, but not statistically significant, in the physiotherapy group (mean ± SD 4.7 ± 4.7) than in the chiropractic group (mean ± SD 4.1 ± 3.3). The majority of the chiropractic patients received spinal manipulation. The number of treatments and treatment forms varied more between the individual patients in the physiotherapy group (Skargren et al., 1997). None of the physiotherapists was a specialist in manipulation.

      Analysis

To detect any significant differences between groups, chisquare tests were used in comparing proportions of patients and the Mann–Whitney U-test and t-test for groups, in comparing means of pain intensity, general health and Oswestry score. The Mann–Whitney U-test and t-test for groups gave similar results, thus the t-test values are presented. Significance level was P , 0.05 (two-sided). Linear multiple regression was used to identify prognostic factors of importance. Two dependent variables were used in the multiple regression analysis, one representing the end level in Oswestry score at 12-month follow-up and the other, the change in Oswestry score between entry and 12-month follow-up. Before the multiple regression, all background variables and severity of problem variables at entry as well as the two dependent variables, were entered in a bivariate correlation analysis (Pearson’s product correlation coefficient) in order to find the independent variables that significantly correlated with the dependent variables (Tabachnick and Fidell, 1996). The threshold level P £ 0.10 was used. Pain radiation, exercise habits and job satisfaction did not correlate significantly with any of the dependent variables, so they were excluded.

The multiple regression analysis was performed in two steps with both of the dependent variables. Firstly, a stepwise multiple regression was performed in order to find the most important prognostic factors, the variables with a significant regression coefficient. Two stepwise multiple regression models were performed, the first including the variable sick-leave. As sick-leave did not emerge as a factor and excluded 15% of the population (those not at work), we did a second multiple regression model without sick-leave. The decision to exclude sick-leave was also based on the fact that Oswestry score, which is a broad measure of disability, strongly significantly correlated (r = 0.45) with sick-leave (Tabachnick and Fidell, 1996).

Secondly, a separate multiple regression analysis with the variables received in the stepwise multiple regression was performed of chiropractic and physiotherapy. The regression coefficients (B values) were compared using a covariance analysis (Hassard, 1991).



Results

     

Description of the study population Background data and other characteristics of the two groups confirming the study population did not differ significantly initially, except for a slight difference in pain intensity and general health (both measured with VAS). The patients in the physiotherapy group estimated their pain intensity and general health slightly to be worse than the patients in the chiropractic group before treatment (Table 1).

      Prognostic factors and comparison of regression coefficients

In total 14 variables were included in the stepwise multiple regression analysis. The analysis showed that five of the factors, i.e. duration of current episode, Oswestry score at entry, number of localisations, expectations of treatment and well-being, were significantly associated with Oswestry score at the 12-month follow-up (Table 2). The remaining nine factors: age, sex, smoking, similar problem previously, neck or low back problems, pain intensity and frequency, and general health (VAS) did not contribute significantly to the prediction of outcome.

Separate multiple regression analysis of chiropractic and physiotherapy showed no significant difference between regression coefficients for the five significant prognostic factors derived in the stepwise analysis (Table 3). The same significant prognostic factors appeared when the dependent variable change in Oswestry score from entry to 12-month follow-up was used in the stepwise multiple regression. The regression coefficients and significance levels received were the same as when level of Oswestry at 12-month follow-up was used, with one exception. The regression coefficient B (SE B) value for the Oswestry score at entry was higher, -0.72 (0.05) compared to 0.28 (0.05). The adjusted R square for the model was 0.62. This was the case for the multiple regression analysis with the five significant prognostic factors as well. The regression coefficients B (SE B) for Oswestry score at entry were -0.71 (0.06) in the chiropractic group and -0.70 (0.07) in the physiotherapy group. The adjusted R square was 0.66 for chiropractic and 0.54 for physiotherapy.

      Amount of patients with a poor prognosis

When the three prognostic factors, i.e. duration of current episode, expectations of treatment, and number of localisations, were applied in the study population, 14% of the patients had poor prognosis (duration ³ 1 month, more than one localisation, and less positive expectations of treatment, while 13% had good prognosis (duration £ 1 week, one localisation, and expected to be completely restored). Those with poor prognosis estimated mean (SD) Oswestry score significantly higher at 12-month follow-up 23 (14)% than those with a good prognosis 7 (12)% the remainder, who had a mixture of good and poor prognostic factors scored 16 (14)%. The proportion of patients and mean Oswestry score at 12-month follow-up was similar concerning the chiropractic and the physiotherapy groups in the prognostic groups.

If the prognostic factor ‘well-being’ (very good/less good) was added, 12% of the patients had poor prognosis and 4% good. Corresponding mean (SD) for Oswestry score at the 12-month follow-up were 26 (14)% and 4 (8)%.



Discussion

Five prognostic factors for disability at the 1-year followup emerged from this study; duration of current episode, Oswestry score, number of localisations, expectations of treatment and well-being at entry. The same prognostic variables emerged for level of disability and change of disability at the 12-month follow-up. The result partly confirmed what previous studies in the area have shown, but also highlighted that the number of localisations, patients’ expectations of treatment and well-being were important factors that need to be considered in clinical praxis and in the prediction of outcome.

Our study population represents a substantial part of the patients visiting general practitioners for back pain, which was judged by the physician as needing physical treatment. The fact that the data were taken from a randomised study in which part of the patients were seen ineligible (Skargren et al., 1997) might be a limitation. However, our study population did not differ from those in most of the previous studies on prognostic factors for outcome in patients with back pain visiting primary care, according to such background data as age, proportion of patients with previous back problems and degree of patients at work (Roland and Morris, 1983; Lanier and Stockton, 1988; Von Korff et al., 1993; Coste et al., 1994; Burton et al., 1995; Cherkin et al., 1996). In some previous studies the proportion of patients with acute low back problems was similar to ours (Singer et al., 1987; Von Korff et al., 1993), in others the proportion of patients with acute low back problems was slightly higher than in our study (Pedersen, 1981; Cherkin et al., 1996; Hoogen van den et al., 1997). Two of the previous studies only included patients with acute low back pain (Coste et al., 1994; Klenerman et al., 1995).

The separate multiple regression analysis of chiropractic and physiotherapy showed that the five prognostic factors had similar effects in the two treatment strategies. The comparison of regression coefficients between the two treatment strategies did not show any significant difference, but a slight tendency to difference in the factor ‘duration of current episode’ strengthened the previous subgroup analysis. The subgroup analysis showed that patients with acute (£1 week) problems benefited more from chiropractic or manipulation whereas patients with more chronic problems (³1 month) benefited more from physiotherapy in the change in Oswestry score (Skargren et al., 1998).

Disability at entry (also called activity discomfort in some previous studies) and duration of current episode have appeared beside other factors in several previous studies of patients with back pain in primary care (Pedersen, 1981; Roland and Morris, 1983; Singer et al., 1987; Von Korff et al., 1993; Coste et al., 1994; Burton et al., 1995; Klenerman et al., 1995; Hoogen van den et al., 1997), suggesting that they are important factors in this population and need to be considered in clinical praxis. Previous problems with back pain have been shown to be a prognostic factor for outcome in disability in a number of previous studies in the area (Pedersen, 1981; Singer et al., 1987; Deyo and Diehl, 1988; Coste et al., 1994; Burton et al., 1995), but this did not emerge in this study. However, the variable ‘previous problems’ emerged only for patients with acute problems (Burton et al., 1995) or was more specified in those studies than in ours e.g. number of previous episodes (Singer et al., 1987; Deyo and Diehl, 1988) previous chronic episodes (Coste et al., 1994), duration of previous period more than 3 weeks (Pedersen, 1981). Different findings suggest that more specified questions of the frequency and length of previous problems combined with definitions of subgroups might be more important for outcome than simply if the patients have had previous problems or not.

The number of localisations (pain from more than one region) has not been shown previously to be a prognostic factor for disability in back pain patients visiting primary care. This might be explained by the fact that the variable has not been inserted in multivariate analysis previously. However, some related studies have been presented, suggesting that it is important if the pain is localised to more than one region. Murphy and Cornish, 1984 showed that acute low back pain patients who became chronic reported pain over a wider area of the body according to a pain drawing, and Buskila et al., 1997 showed that the development of fibromyalgia syndrome was more frequent following cervical spine injury than following lower extremity injury. Another recent study showed that the number of pain sites was a prognostic factor for worse long-term outcome for work disability in patients with musculoskeletal soft tissue injury (Crook and Moldovsky, 1996). Finally, Leboeuf-Yde et al., 1997 showed a difference in association between potential risk indicators (age, sex, marital status, attitude to a healthy life style, self-reported physical activity at work, and smoking) between subgroups of patients with low back pain with and without pain in the neck or upper extremity.

Expectations of treatment have not previously been shown to be a prognostic factor for level or change in disability due to back pain. Like the number of localisations this variable has not previously been used in multivariate analysis of back pain patients in primary care. However, other closely related factors such as attitudes towards and beliefs about pain in chronic back pain patients (Strong et al., 1990), fear-avoidance beliefs (Waddell et al., 1993) and fear-avoidance behaviour (Klenerman et al., 1995) have been shown to be prognostic factors for outcome in disability. According to the literature, expectation is regarded as part of satisfaction and fear-avoidance behaviour (Linder- Pelz, 1982; Klenerman et al., 1995; Thompson and Sun˜ol, 1995). A couple of papers presented recently have show an increasing interest in the importance of patients’ expectations on outcome in back pain (Deyo et al., 1994; Borkan and Cherkin, 1996).

The last factor that emerged in the stepwise analysis was well-being. The factor might be regarded as closely related to psychosocial factors like anxiety, depression, coping strategy and always feeling sick (part of SIP), which have previously been shown to be factors of importance for disability (Deyo and Diehl, 1988; Lanier and Stockton, 1988; Burton et al., 1995).

The variables age, sex, smoking, exercise habits, similar problems in the previous 5 years, pain radiation, pain intensity and pain frequency and general health (VAS) did not emerge as significant prognostic factors. This does not mean that they are of no importance for the prognosis of low back pain, but merely that other factors were more important in this study population. Pain radiation, for instance, has been shown to be a prognostic factor in a number of previous studies of back pain patients in primary care (Pedersen, 1981; Chavannes et al., 1986; Lanier and Stockton, 1988; Cherkin et al., 1996), but not in this study. This might partly be explained by the low proportion of patients in the study population who had pain radiating distally.

Two of the five prognostic factors received in this study have been found in previous studies. The prognostic factors received in patients with back pain in primary care vary considerably between different studies. Restrictions of study population (acute, subacute or a mixture of problems, high number of drop outs (Burton et al., 1995; Klenerman et al., 1995; Hoogen van den et al., 1997), small sample (Pedersen, 1981; Lanier and Stockton, 1988; Coste et al., 1994), long time to data collection (Von Korff et al., 1993; Klenerman et al., 1995), and the length of follow-up period (Klenerman et al., 1995; Cherkin et al., 1996) are factors in the study design and performance that influence what factors will emerge. Other factors of importance for which prognostic factors will emerge are what independent variables were inserted in the multivariate analysis and the choice of dependent variable. Many of the differences in received prognostic factors between studies within the area can be explained by the differences in preconsumption.

Even though the identified factors do not explain the whole outcome, 12% of the patients in our study were identified as having four of the poor prognostic factors before treatment, e.g. duration of current episode ³1 month, more than one localisation of pain, low well-being and did not expect that they would be completely restored by the treatment. The mean Oswestry score never reached below 20% for these patients, which means that they still had moderate disability according to the definition by Fairebank et al., 1980. It might be that if we use subgroupings according to prognostic factors, a proportion of patients do not reach a clinically acceptable level of disability. These patients with poor prognosis can easily be identified in clinical praxis. It is important to identify these patients early, and it might be important to consider a supplementary treatment model not included in this study. Previous studies have shown that cognitive-behavioural models added to traditional physiotherapy are more effective than solely traditional treatment in patients with back pain (Fordyce et al., 1986; Nicholas et al., 1992; Linton, 1994; Turner, 1996). Others have shown that multimodal approaches are effective in chronic back pain (Pfingsten et al., 1997).



Conclusion

The factors ‘duration of current episode’ and ‘Oswestry score at entry’ that emerged strengthen previous results and the factors ‘number of localisations, expectations of treatment’ and ‘well-being’ add new factors. Clinical decision models for managing patients with back pain visiting primary care that consider prognostic factors need to be implemented and prospectively evaluated.


Acknowledgments:

This research was supported by the County Council of O¨ stergo¨tland and Va°rdalstiftelsen. The authors thank Per Carlsson, Mikkel Gade and Annika Rosenbaum, Hans Tropp and UllaMaija O¨ dman for offering their expert knowledge in the planning and implementation of the study and John Carstensen for statistical advice.



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