The influence of pregnancy and pelvic girdle pain on weight-bearing activities - A biomechanical and clinical study

Abstract

Background: During pregnancy, women experience physiological and anatomical changes that may influence their physical function. In addition, a large number of pregnant women develop pelvic girdle pain (PGP). PGP is regarded a musculoskeletal disorder and commonly affects everyday activities, work ability and quality of life. Pregnant women with PGP often report pain and limited ability to perform weight-bearing activities, particularly walking. However, few studies have assessed gait characteristics in this population. It is previously shown that self-reported disability as well as altered gait biomechanics may be present also in healthy pregnant women. Since weight-gain during pregnancy likely influences movement, it seems pertinent to investigate the influence of PGP and pregnancy on gait prior to the 3rd trimester. Still, few have studied gait biomechanics in the 2nd trimester and the results differ. Hence, there is a need to explore spatiotemporal and kinematic gait characteristics in pregnant women with and without PGP in the 2nd trimester and in asymptomatic non-pregnant women. Despite the importance of weight-bearing activities, few functional tests have previously been available in the clinical examination of pregnant women with PGP. The Stork test is a single leg stance (SLS) test proposed to examine loading strategies also in PGP patients. Clinicians observe and describe specific movement patterns and often assume that these patterns are related to PGP. However, there is a need to explore whether movement patterns can be identified and, how these patterns relate to PGP and pregnancy. Recently, the Timed Up and Go (TUG) test was proposed as a physical performancebased test in pregnant women with PGP. TUG is a standardized, timed functional mobility test and includes stand up, turn around, walk and sit down. Hence, it involves activities problematic for pregnant women with PGP and, may assist in determining the extent of physical disability and complement patient-reported instruments. However, further research is needed to investigate if TUG time differs between pregnant women with and without PGP and in non-pregnant women, as well as what factors potentially influence TUG time in the 2nd trimester. Aims: The overall aim of this thesis was to explore the influence of PGP and pregnancy on weight-bearing activities in the 2nd trimester of pregnancy, by comparing pregnant women with PGP and asymptomatic non-pregnant women versus asymptomatic pregnant women. Specifically, we aimed to explore between-group differences in spatiotemporal characteristics and trunk, pelvic and hip kinematics during gait and the Stork test, measured by 3 dimensional (3D) kinematic analyses. We also aimed to compare TUG time in these three groups of women, and to identify potential factors associated with longer TUG time. Methods: This cross-sectional study included 25 pregnant women with PGP, 24 asymptomatic pregnant (all 49 before gestation week 27) and 25 asymptomatic non-pregnant women. All underwent clinical examination including the TUG test, as well as 3D movement analysis of the Stork test and gait at self-selected speed. In paper I, one-way analysis of variance was used to explore between-group differences in TUG, and multiple linear regression analyses to explore associations between TUG and potential explanatory variables in the total study sample and in pregnant women with PGP. In paper II and III, linear mixed models were used to investigate between-group differences in spatiotemporal gait characteristics, as well as trunk, pelvic and hip kinematics during gait and the Stork test. In addition, bivariate analyses were used in paper II to investigate the relationship between gait speed and fear of movement, self-reported disability and pain intensity in the pregnant women with PGP. Results: During gait at self-selected speed, pregnant women with PGP demonstrated significant slower gait speed (18 %) and up to 10 % difference in spatiotemporal variables, as well as small pelvic and hip kinematic differences compared to asymptomatic pregnant women. In the PGP group, gait speed was negatively associated with fear of movement and self-reported disability, while it was not significantly associated with pain intensity. Asymptomatic pregnant women walked with longer cycle time, stance time and double limb support and less thorax rotation as compared to non-pregnant women. In the Stork test, we generally found few and only small significant between-group differences in spatiotemporal and kinematic variables. Importantly, the variation in kinematic variables was large across participants in all three groups during this test. TUG time varied among pregnant women with PGP, and this group used significantly longer time than asymptomatic pregnant and non-pregnant women. In the total study sample, longer TUG time was significantly associated with group, higher BMI and sick leave. In pregnant women with PGP only pain intensity remained significantly associated with longer TUG time in the multivariable analysis. Conclusion: This thesis provides novel information on weight-bearing activities in the 2nd trimester of pregnancy. We found that PGP influenced TUG time, as well as gait characteristics in the 2nd trimester. Pregnant women with pelvic girdle pain walked slower and with a more rigid movement pattern compared to asymptomatic pregnant women. Pregnancy also influenced a few gait variables, demonstrated by significant differences between asymptomatic pregnant and non-pregnant women. Our findings provide a basis for the clinical evaluation of gait and support TUG time as a suitable measure of activity-limitations in pregnant women with PGP in the 2nd trimester. The associations between TUG time and pain intensity, and between gait speed and both fear of movement and disability, indicate that biopsychosocial aspects relate to weight-bearing activities in women with PGP in the 2nd trimester. Neither PGP nor pregnancy appeared to influence trunk, pelvic and hip movements during the Stork test, and clinically observed movement patterns were not identified in our study. Hence, visually observing trunk, pelvic and hip movement patterns during this test may have limited clinical importance when examining pregnant women in the 2nd trimester, and clinicians using the test should pay attention to individual movement responses rather than focusing on specific patterns.