Letters [1]

SPINE Volume 31, Number 20, pp 2405–2407 ©2006, Lippincott Williams & Wilkins, Inc. Letters To the Editor: Re: Goldby LJ, Moore AP, Doust J, et al. A randomized control trial investigating the efficiency of musculoskeletal physiotherapy on chronic back pain disorder. Spine 2006;31:1083–93. Dr Goldby and her coauthors deserve appreciation for their efforts in comparing different physiotherapy approaches in a 3-arm randomized controlled trial. However, their conclusion that “the spinal stabilization program is more effective than manually applied therapy or an education booklet in treating chronic low back pain disorder over time” (p. 1083) needs reconsideration. The key problems in the trial are treatment dropouts and loss to follow-up. Only 66% of randomized subjects completed treatment. Additionally, only 62% of randomized subjects were followed up at 3 months, while 54% were followed up at both 6 and 12 months and 28% at 24 months. Inspection of Figures 3 and 4 confirms that the postrandomization exclusions (34% of those randomized) corrupted the randomization process. This is demonstrated by observing the markedly different baseline scores obtained by the three groups on the pain and disability outcomes. Also, the losses to follow-up were quite different in the three groups. For example, at 1 year, approximately 39% of those randomized to the education group were followed up versus 57% of the spinal stabilization group. These problems mean that it is not possible to confidently attribute the observed between-group differences to treatment. Accordingly, the relative effectiveness of these three treatments remains uncertain. Leonardo Oliveira Pena Costa, MSc Chris G. Maher, PhD Jane Latimer, PhD Back Pain Research Group University of Sydney Sydney, Australia To the Editor: Re: Goldby LJ, Moore AP, Doust J, Trew ME. A randomised controlled trial investigating the efficiency of musculoskeletal physiotherapy on chronic low back disorder. Spine 2006;31:1083–93. We congratulate Goldby and colleagues on their trial of spinal stabilization exercise, manual therapy, and ed- ucation for chronic low back pain. Their results suggest that patients had better outcomes with the exercise group. This paper deserves both careful consideration and critical comment on issues that the review process appears not to have addressed. Better adherence to the Consolidating Standards of Reporting Trials (CONSORT) statement1 would have been beneficial. Issues of concern include: 1) the education booklet group had less severe clinical characteristics (pp. 1087– 8), yet these imbalances are not adjusted for in the analyses2; 2) analysis focuses on within-group differences and the between-group results are hidden among more impressive within-group changes; 3) a newly developed dysfunction score is used without detail of its composition or sensitivity to change; 4) there are multiple analyses, without mention of, or adjustment for, the dangers associated with these3,4; and 5) the sample size is based on seeing a 30% difference between groups (p. 1085) on the Oswestry Disability Index, yet the difference between the stability and manual therapy group was about 14% in favor of the stability group, a difference slightly above the suggested minimally important clinical change of 10%5 but substantially lower than the difference that the trial was powered to detect. Data analysis was based on a per-protocol approach rather than the widely accepted intention-to-treat approach, which enhances internal validity; thus, the analysis had reduced sample numbers: about 30% loss to follow-up at 3 months and 40% at 6 and 12 months (p. 1085). Six different subgroups of patients are analyzed, yet subgroup analyses should be predefined and carefully justified, and trials should be powered to detect subgroups reliably.6 So what does this trial really show? Had the focus been on the primary outcome and on between-group effects, the authors may have been less enthusiastic about the effectiveness of spinal stability exercise. It is crucial that the results of this trial are interpreted correctly. This trial does not provide satisfactory evidence that spinal stabilization exercise is more effective than the interventions with which it was compared. Nadine E. Foster, DPhil, BSc(Hons), MCSP Kika Konstantinou, PhD, MMACP, MCSP, MSc Martyn Lewis, PhD, BSc(Hons) Primary Care Musculoskeletal Research Centre Keele University Keele, UK 2405 2406 Spine • Volume 31 • Number 20 • 2006 Melinda Cairns, PhD, MMACP, MCSP, MSc School of Paramedic Sciences Physiotherapy and Radiography Faculty of Health and Human Sciences University of Hertfordshire Hertfordshire, UK References 1. Moher D, Schulz KF, Altman D. The CONSORT Statement: revised recommendations for improving the quality of reports of parallel-group randomised trials. JAMA 2001;285:1987–91. 2. Vickers AJ, Altman DG. Analysing controlled trials with baseline and follow up measurements. BMJ 2001;323:1123– 4. 3. Prentice R. On the role and analysis of secondary outcomes in clinical trials. Control Clin Trials 1997;18:561–7. 4. Davis CE. Secondary endpoints can be validly analyzed, even if the primary endpoint does not provide clear statistical significance. Control Clin Trials 1997;18:557– 60; discussion 561–7. 5. Ostelo RWJG, de Vet HCW. Clinically important outcomes in low back pain. Best Pract Research Clin Rheum 2005;19:593– 607. 6. Rothwell PM. Subgroup analysis in randomised controlled trials: importance, indications and interpretation. Lancet 2005;365:176 – 86. was made. Moreover it is not clear why only women with a history of back pain were asked to fill out more detailed questionnaires about pain and disability and the others were not. The authors were very positive about the reliability of the used pain provocation tests but presented a rather selective sample of references. More critical references about those tests2 were not included. It seems incautious to make statements about a different clinical course of PPGP and lumbar pain and present a direction about the evaluation on generic and specific levels in combination with pathoanatomic subgrouping based on this study. Caroline H. G. Bastiaenen, PhD Janneke M. Bastiaanssen, MSc Rob A. de Bie, PhD Department of Epidemiology Maastricht University Maastricht, The Netherlands References To the Editor: Re: Gutke A, Östgaard HC, Öberg B. Pelvic girdle pain and lumbar pain in pregnancy: a cohort study of the consequences in terms of health and functioning. Spine 2006;31:E149 –55. In the March 2006 issue, Gutke et al reported the findings of their cohort study on pelvic girdle pain and lumbar pain in pregnancy. We support the authors’ assertion that the prevalence of pregnancy-related pelvic girdle pain and the consequences in terms of health and functioning are important issues to investigate in a cohort study. However, while reading the article, some essential doubts arose concerning the design and the underlying assumptions of this study. In the first paragraph, the authors wrote: “PPGP occurs during pregnancy or within the first 3 weeks after delivery.” Cohort studies investigating study questions like those mentioned should preferably include pregnant women during early pregnancy and follow them for a longer period than by the period defined by the authors themselves within which new cases could arise. The authors indeed included women during early pregnancy, but the study turned out to be only cross-sectional (only one measurement at early pregnancy) and not a cohort study. Subsequently, figures about prevalence and consequences of the disorder are incomplete and only have limited value. Secondly, the authors wrote, “PPGP and lumbar pain have different etiologies and require different treatment strategies” and based their study design on these assumptions. Although the reported references (not very recent) provide the same statements, the etiology about pregnancy-related pain in the lumbopelvic region is not clear at all.1 It seems quite probable that the assumption that both groups are different substantially biased the results since in the design of the study a distinction between lumbar pain, pelvic girdle pain, and a combination group 1. Bastiaanssen JM, de Bie RA, Bastiaenen CHG, et al. A historical perspective on pregnancy-related low back and/or pelvic girdle pain. Eur J Obstet Gynecol Reprod Biol 2005;120:3–14. 2. van der Wurff P, Hagmeijer RH, Meyne W. Clinical tests of the sacroiliac joint: a systemic methodological review. Part 1: Reliability. Man Ther 2000; 5:30 – 6. In Response: Re: Gutke A, Östgaard HC, Öberg B. Pelvic girdle pain and lumbar pain in pregnancy: a cohort study of the consequences in terms of health and functioning. Spine 2006;31:E149 –55. We thank Bastiaenen et al for their comments that may help us to clarify some points in our publication. We agree on comments concerning the design if we strictly consider the actual publication in epidemiologically terms. The study design includes baseline in pregnancy, follow-up at 3 months postpartum, and inclusion of the women classified with pregnancy-related pelvic girdle pain (PPGP) into a randomized controlled trial with a 2-year follow-up. The whole study design was not described in the publication, which might have been of interest. The definition used, “PPGP occurs during pregnancy or within the first 3 weeks after delivery,” is not as stated by Bastiaenen et al, “the period defined by the authors themselves within which new cases could arise” but applied from research in the field.1 We agree that in the sentence about different etiologies of PPGP and lumbar pain, “etiology” is too strong and “clinical presentation” should have been used until the problem is better understood. We used a large time span (1988 –2004) of references supporting the need for subgrouping into PPGP and lumbar pain. We wanted to show that it has been repeated recommendations throughout the years that PPGP should be differentiated from lumbar pain. This is also the consensus of an international Letters to the Editor • Gutke et al 2407 group of experts in the field within the European commission research (www.backpaineurope.org). The patients with lumbar pain are mostly excluded in studies of lumbopelvic pain in pregnancy. We found it important to keep the whole pregnant cohort within the study in order to evaluate the lumbar pain group as well as the PPGP group for possible similarities and differences in outcomes. The assumption that PPGP and lumbar pain are different is a hypothesis of the study. The aim of the study was to describe the consequences in the different subgroups not to prove the etiology of PPGP; therefore, the comment on bias seem inappropriate. The recommendations for research in primary care to identify subgroups of low back pain in order to develop specific treatment strategies are in line with our study design.2 Bastiaenen et al are critical of our choice of references supporting the pain provocation tests used in our study. They refer to a review by van der Wurff et al who developed a scoring system where the authors themselves had the highest score of all studies. This highest scored study was in Dutch. van der Wurff et al recommended further research in this area with an emphasis on multiple test scores and pain provocation test of the sacroiliac joints. We have used a multiple test score. Further conclusion was that the Gaenslen’s and the thigh thrust tests seem to be reliable. Both tests were used in our study and either or both of the tests were positive in all women with PPGP except in one with combined PPGP and lumbar pain. There is still a need for further studies to understand and develop valid and reliable classification of these groups. Bastiaenen et al questioned that only women with a history of back pain were asked to fill out a more detailed View publication stats questionnaire. The questions regarding previous lumbopelvic pain and its consequences (sick leave due to back pain, whether the previous back pain was pregnancy-related, etc.) can only be answered by those who have had any experience of lumbopelvic pain. In the final statement in our publication, “This study shows that it is useful to evaluate on both specific and generic levels in combination with pathoanatomic subgrouping for the understanding of the different clinical course of PPGP and LP” the use of clinical “course” aimed at the clinical experience from this patient groups as well as the published result that most women with PPGP recover postpartum3 while women with non– pregnancy-related low back pain experience a recurrent course.4 We find it interesting that, when using existing clinical testing, there was a difference in self-reported function and health among those subgroups. Annelie Gutke, RPT Hans Christian Östgaard, MD, PhD Birgitta Öberg, PhD Department of Health and Society Linköping Universitet Linköping, Sweden References 1. Mens JM, et al. Understanding peripartum pelvic pain: implications of a patient survey. Spine 1996;21:1363–9; discussion 1369 –70. 2. Borkan JM, et al. A report from the Second International Forum for Primary Care Research on Low Back Pain: reexamining priorities. Spine 1998;23: 1992– 6. 3. Albert H, Godskesen M, Westergaard J. Prognosis in four syndromes of pregnancy-related pelvic pain. Acta Obstet Gynecol Scand 2001;80:505–10. 4. Von Korff M, Saunders K. The course of back pain in primary care. Spine 1996;21:2833–7; discussion 2838 –9.