Correction of leg-length discrepancy among meat cutters with low back pain: a randomized controlled trial

Abstract

Background: The etiology of non-specific low back pain (LBP) is complex and not well understood. LBP is common and causes a remarkable health burden worldwide. Leg-length discrepancy (LLD) is potentially a risk factor for development of LBP, although this relationship has been questioned. Yet only one randomized controlled study (RCT) has been performed. The objective of our study was to evaluate the effect of insoles with leg-length discrepancy (LLD) correction compared to insoles without LLD correction among meat cutters in a RCT-design.

Methods: The study population consisted 387 meat cutters who were over 35 years old and had been working 10 years or more. The LLD measurement was done by a laser ultrasound technique. All workers with an LLD of at least 5 mm and an LBP intensity of at least 2 on a 10-cm Visual Analog Scale were eligible. The LLD of all the participants in the intervention group was corrected 70%, which means that if the LLD was for example 10 mm the correction was 7 mm. The insoles were used at work for eight hours per day. The control group had insoles without LLD correction. The primary outcome was between-group difference in LBP intensity. Secondary outcomes included sciatic pain intensity, disability (Roland Morris), RAND-36, the Oswestry Disability Index, physician visits and days on sick leave over the first year. We used a repeated measures regression analysis with adjustments for age, gender and BMI. The hurdle model was used for days on sick leave.

Results: In all, 169 workers were invited and 114 (67%) responded. Of them, 42 were eligible and were randomized to the intervention (n = 20) or control group (n = 22). The workers in the intervention group had a higher improvement in LBP intensity (- 2.6; 95% confidence intervals - 3.7 - - 1.4), intensity of sciatic pain (- 2.3; - 3.4 - - 1.07) and RAND-36 physical functioning (9.6; 1.6-17.6) and a lesser likelihood of sick leaves (OR -3.7; - 7.2 - -0.2).

Conclusions: Correction of LLD with insoles was an effective intervention among workers with LBP and a standing job.

Trial registration: ISRCTN11898558 . Registration date 11. Feb 2011. BioMed Central Ltd.

Keywords: Insoles; Leg-length discrepancy; Low back pain; Randomized controlled trial.

Conflict of interest statement

Ethics approval and consent to participate

The study was approved by the Ethics Committee of the Central Hospital of Southern Ostrobothnia (11/2006), and followed the principles of the Declaration of Helsinki. All participants took part on a voluntary basis and signed their informed consent.

Consent for publication

Not Applicable.

Competing interests

The authors declare that they have no competing interests.

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Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1

Flow chart of the study

Fig. 2

Mean intensity of LBP during past week and its 95% confidence intervals (CI) at each time point and in both intervention groups

Fig. 3

Probability of sickness absence due to LBP during the past year and its 95% confidence intervals (CI) at each time point and in both intervention groups

Fig. 4

Mean number of days on sick leave due to LBP during the past year and its 95% confidence intervals (CI) at each time point and in both intervention groups