Association of Biomechanical Changes and Weight Gain Throughout Pregnancy
Condition: Low Back Pain; Pregnancy
MeSH terms: Back Pain; Low Back Pain; Weight Gain
Study type: Observational

Summary: 
      Low back and posterior pelvic pain are common in pregnant females. Previous studies have
      demonstrated disability and it is estimated that all women experience some degree of
      musculoskeletal discomfort during pregnancy. Borg-Stein et. al. found 25% of pregnant females
      have temporarily disabling symptoms.

      There is demonstrated controversy over the mechanism of low back pain in pregnancy. The
      biomechanical theory implies that the enlarging uterus causes the maternal center of gravity
      to move anteriorly causing stress on the low back. Jensen et. al. demonstrated that weight
      gain correlated with biomechanical changes. The changes were measured by weight gain in
      segmental regions of the body and in principal moments of inertia from the sit to stand
      movement. Literature does not demonstrate a specific correlation between weight gain and the
      biomechanical changes of sway rate, lumbosacral angle and center of gravity. These three
      measurements may have a correlating effect on the underlying cause of low back pain in
      pregnant women.

      This study aims to determine the correlation between weight gain of pregnant females and the
      biomechanical changes of sway rate, lumbosacral angle and center of gravity. The change in
      weight over the last two trimesters will be correlated with the sway rate, lumbosacral angle
      and center of gravity. The degree of symptomatic low back pain as measured by the Oswestry
      Low Back Pain Scale will also be correlated with the sway rate, lumbosacral angle and center
      of gravity.
    

Detailed description: 
      The principal investigator will recruit subjects at the yoga studio and one of the
      investigators and the research assistant will recruit subjects at the NSU clinic. Potential
      subjects will go through a short verbal pre-screening to ensure they fit the inclusion and
      exclusion criteria. Subjects that fit this criteria will read and sign the consent form. The
      PI and research assistant will answer any questions about the study prior to the subject
      giving consent.

      Then the subject's initial weight will be measured on the postural scale and documented.
      Change in weight is the dependent variable in this study. The following independent variables
      will be measured: lumbosacral angle, sway rate and shift of weight posteriorly. The
      lumbosacral angle will be measured by a digital inclinometer. The lumbosacral angle is
      measured between the plane of the superior surface of S1 to the horizontal plane. Saur et.
      al., demonstrated that the inclinometer technique for lumbosacral angle has established
      validity and reliability in comparison to radiographic x-rays. Comparison of radiographic and
      inclinometer technique is clinically suitable for measuring lumbar position. Keeley et. al.
      reported high correlation coefficients for interrater reliability with the inclinometer
      technique on patients with chronic low back pain.

      The additional measurements of sway rate and center of gravity will be measured by the
      postural analyzer. The quadruple scale that will be used in this study is based on four
      digital force plates with computer communication operated by software enabling test analysis.
      The quadruple scale will provide numeric and graphic data on total weight, weight
      distribution (kg. or lb.), percentage weight difference, sway rate and an estimate of the
      location and deviation of the subject's center of mass. All data will be recorded and saved.

      Following those measurements, the subject will be asked to complete the Oswestry Low Back
      Pain Scale. The Oswestry Low Back Pain Scale is a suitable questionnaire for an
      English-speaking population and to enquire about areas of functioning specifically relevant
      to low back pain sufferers, such as lifting, walking, sitting, standing, sleeping and
      socializing. Fisher et. al. demonstrated that the Oswestry Low Back Pain Scale is an
      acceptable instrument for back pain patients with evidence of criterion-related validity,
      factorial validity and moderately high internal consistency. It has good face validity for
      the patients. According to Fisher et. al., the Oswestry Scale can be recommended as a
      relevant measure of disability with evidence of validity, reliability and sensitivity to
      change for both clinical and research purposes.

      The total amount of time needed to complete the measurements and the Oswestry Low Back Pain
      Scale should take 15 minutes. Biweekly, willing participants will be recruited and previous
      participants will be continually measured for weight, lumbosacral angle, sway rate and
      deviation of the subject's center of mass.
    

Intervention name(s): Postural Analysis
Intervention type(s): Other
Intervention description(s): Measure the subject's weight, sway rate and shift of center of gravity on a postural scale for 15 seconds. Measure lumbosacral angle with an inclinometer.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Pregnant females in their second or third trimester.
      
Keywords: Low Back Pain; Pregnancy; Biomechanics