Optimizing physical and psychosocial assessment in patients with non-specific chronic low back pain

NS-LBP is defined as pain and discomfort, localized below the costal margin and above the inferior gluteal folds, with or without referred leg pain, that is not attributable to a recognizable, known specific pathology. NS-CLBP involves NS-LBP persisting for at least 12 weeks. In the civilian as well as in the military population NS-CLBP is a common problem with an important impact on the patient’s functioning and on the society. Previous research demonstrated that NS-CLBP is not only caused by physical factors, but the psychosocial factors also play an important role in the onset and perpetuation of NS-CLBP. It is commonly accepted that these patients should be assessed biopsychosocialy. The planetary model is therefore an adequate coat rack in the management of NS-CLBP. To ensure a good outcome, it is primordial to tailor the therapy in function of the patient’s needs. This is only possible after a detailed physical and psychosocial assessment of the patient. Different tools and concepts were proposed to sustain this assessment, but some pitfalls exist. The aim of this doctoral dissertation was to optimize some aspects of the assessment of patients with NS-CLBP, to objectify the patient’s complaints and the associated influencing factors. The project was subdivided in three parts. In the first part trunk muscle recruitment patterns were investigated with sEMG. Literature often described altered trunk recruitment patterns in patients with NS-CLBP. Trunk muscle recruitment patterns were analyzed in terms of ratios of deep stabilizing muscle groups to global torque producing muscles. In Chapter 1 de influence of velocity of isokinetic movement on trunk muscle recruitment patterns was investigated. Fifty-three healthy subjects (26 men and 27 women) performed flexion-extension movements on a Cybex isokinetic dynamometer at different velocities (30°/s, 60°/s, 90°/s, 120°/s). The activity of two deep stabilizing muscle groups (m. obliquus internus abdominis (IO) and the lumbar m. multifidus (LMF)) and two superficial torque producing muscles (m. obliquus externus abdominis (EO) and the m. iliocostalis lumborum pars thoracis (ICLT)) were recorded simultaneously. The relative muscle activity as well the ratios LMF/ICLT and IO/EO were analyzed. Results demonstrated that the relative muscle activity of the different back muscles decreased with increasing velocity, but the LMF was less influenced by velocity than the ICLT, resulting in an increased ratio LMF/ICLT at high velocity. This study did not demonstrate an influence of velocity on the abdominal muscle groups. In Chapter 2 the same ratios were analyzed during 6 sensorimotor control exercises. Sixty-three healthy men and 36 patients with NS-CLBP participated in this study. All patients demonstrated a flexion-related MCI. Based on the trunk muscle recruitment patterns during the 6 exercises a statistical model was developed to discriminate between patients and healthy subjects. This part of the project led to the adjustment of several physical tests of the clinical pathway for NS-CLB at the MHQA. Chapter 1 underlined the importance of the use of different velocities in isokinetic evaluation and treatment of these patients. Chapter 2 provided evidence that trunk muscle recruitment patterns can be measured objectively in patients with flexion-related MCI. This is not only relevant in the clinical practice, but also in research as on objective variable in for example studies investigating the influence of therapy. The second part of the project focused on the improvement of psychosocial evaluation in patients with NS-CLBP. The aim was to optimize the use of self-report questionnaires. Therefore cross-cultural adaptation to Dutch and French was performed for the following questionnaires (Chapter 3): TSK, PHQ-15, QBPDI, OMPQ and the MPIpart1. Based on these and other questionnaires (PCS, DRAM, HADS, SF-36) a battery of self-report questionnaires was developed and long-term test-retest reliability was investigated. Test-retest reliability was analyzed on 48 French-speaking and 43 Dutch-speaking patients with NS-CLBP. Results indicated that scores on most of the questionnaires remained stable over time (> 1 month), except for the SF-36. In Chapter 4, the clinical interpretation of the scores on the questionnaires was facilitated by determining cut-off scores for screening questionnaires (TSK, PHQ-15, OMPQ) on198 patients with NS-CLBP, as well as determining MCIC for evaluative questionnaires (TSK, QBPDI, OMPQ, MPIpart1, SF-36) on 70 patients with NS-CLBP. This part of the study allowed the use of these questionnaires in a French and Dutch-speaking population. Although some waiting time exists between the moment the questionnaire is filled in and the start of the therapy, the clinician may be confident that the scores of the questionnaire are stable over a long period of time (> 1 month), if the patient’s status remains stable. The cut-off scores and the MCIC led to an easy interpretation of the scores and the change in scores. These results are also important in further research. Results of the questionnaires could for example be used as outcome variable in the evaluation of different therapies. The third part of this doctoral project underlined the link between psychosocial and physical evaluation, in the line of existing literature. Chapter 5 gave on example of this. Research was done on the influence of psychosocial factors on performance during two endurance tests for the abdominal and back muscles. Three hundred thirty two patients with NS-CLBP filled in a series of questionnaires. Then they effectuated the Biering-Sorensen back muscle endurance tests (B-S test) and an abdominal endurance test. Simultaneously the muscle activity of the LMF and the ICLT during the B-S test and the IO and the EO during the abdominal endurance test were recorded by sEMG. The time to exhaustion was also recorded. Based on the intrinsic muscle fatigue (normalized slope) the predicted time to exhaustion was calculated for both tests separately. By comparing the real time to exhaustion by the predicted time patients were divided in a performance and an underperformance group. Questionnaire results were compared for both groups. Regression analyses were performed to examine the predictive value of the questionnaires on the time to exhaustion. Results demonstrated that for the B-S test scores on the physical subscales of the SF-36 were lower in the underperformance groups. A higher BMI and low scores on the SF-36PF were significant predictors of low performance on the B-S test (R²=0.10). Concerning the abdominal endurance test, the group patients with low performance had significantly higher scores on the DRAMMZDI and the PCS, and lower scores on the SF-36. A higher BMI and lower scores on the SF-36MCS were significant predictors of lower scores on this test (R³=0.04). The results demonstrated that both tests were influenced differently. The B-S test seemed more influenced by physical factors and the abdominal endurance test were influenced by mental components. Why this difference exists is not clear, but this demonstrates again that in the interpretations of physical tests, psychosocial influences should be considered. Psychosocial influences are not equal for each physical test; therefore a complete psychosocial evaluation is needed. The overall aim of this doctoral dissertation was to contribute to the assessment of NS-CLBP, by improving the use of some instruments and tools. The results of these studies are not only interesting for the clinical practice, but are also useful in further research