Study of Changes in the Feet With Pregnancy
Condition: Pregnancy
Study type: Interventional

Summary: 
      This research is being conducted to determine whether use of an arch-supporting insole during
      pregnancy prevents alterations in foot structure and lower limb rotational movements. The
      investigators hypothesize that the arch collapse during pregnancy will be significantly
      reduced in women randomized to use the supportive insole compared with women randomized to
      the control group.
    

Detailed description: 
      Musculoskeletal impairments are a significant cause of functional limitations and disability
      in women. Women are at higher risk for osteoarthritis in comparison with men [1] and
      functional limitations due to arthritis are also more common in women. [2, 3] In addition,
      women are disproportionately affected (risk compared with men) by knee osteoarthritis
      (1.8x),[4] greater trochanteric pain syndrome (3.3x),[5] incident hip osteoarthritis[6] and
      chronic joint pain (1.3x),[7] including foot pain[8] knee pain[9] hip pain[9-12] and low back
      pain (1.2x).[7, 13] Preventing even a portion of these could avoid functional limitations and
      disability, enhance quality of life and result in considerable savings.[2] However, the
      etiology for the increased risk for these musculoskeletal diseases and impairments has not
      been elucidated.[1] Acute Changes in Foot Structure Are Reported with Pregnancy The
      disproportionate risk for these musculoskeletal problems may, in part, relate to biochemical
      and biomechanical changes that occur in a woman's body during pregnancy. For example, hallux
      valgus deformity, lateral deviation of the great toe often in conjunction with a bunion
      deformity, occurs in women at nine times the rate of men.[14] Both of these have been linked
      to reduction in arch height.[15] Body mass increases by an average of 9-13 kg during
      pregnancy.[16] There is also a seven to ten-fold increase in the relaxin level during
      pregnancy,[17-19] a peptide hormone produced by the corpus luteum which increases the
      flexibility and remodeling of collagen in central and peripheral joints in pregnant
      women.[17, 18, 20-26] Bearing increased weight on joints with increased laxity during
      pregnancy could potentially lead to permanent changes in the feet.[19, 26-28] Increases in
      foot length, width, and volume have been reported during pregnancy.[29, 30, 31] In addition
      to the anatomic changes in the foot, there are also changes in gait pattern during
      pregnancy.[32-35] Nyska found that the center of pressure on the foot during pregnancy shifts
      posteriorly to compensate for the increased anterior abdominal mass.[36] The combination of
      ligamentous laxity in the arch, increased body mass with pregnancy and the shift in the
      center of pressure towards the posterior part of the foot may potentially contribute to
      stretching of the ligaments supporting the arch, leading to loss of arch height.

      More important than the foot changes that have been reported during pregnancy is the issue
      that these changes persist following completion of pregnancy. In a self-report study, we
      found a dose-response relationship between the number of pregnancies and the frequency of a
      report of a permanent change in foot size in women age 18-45.[37] We then conducted a
      longitudinal study to determine whether arch height loss both occurs and persists postpartum.
      Sixty women in their first trimester of pregnancy were enrolled and arch height and function
      were measured at baseline and approximately 19 weeks postpartum. There was a significant
      decrease in arch height and arch rigidity index at follow-up, with concomitant increases in
      foot length and arch drop. This study revealed that, not only was pregnancy associated with a
      permanent loss of arch height, but also the first pregnancy appeared to be the most
      significant with a reduction in arch rigidity (p<0.0001) and increases in foot length
      (p<0.0001), arch drop (p=0.0019) and center of pressure excursion during gait (p=0.0019).
      These changes in the feet could contribute to the increased risk for subsequent
      musculoskeletal disorders.

      Arch Height Loss Leads to Adverse Biomechanical Changes at Other Joints Consideration of the
      effect of foot structure on forces and torques at other joints in the lower limb and spine as
      well as the need for energy generation and absorption by associated soft-tissue structures
      illustrates the importance of these potential changes. With each step, a series of events
      occurs that elicits biomechanical effects and compensations throughout the lower limb kinetic
      chain, in which movement at each joint influences movement at other joints in the chain.[38]
      Disruption of the complex interactions between skeletal, musculotendinous and ligamentous
      structures through loss of arch height may predispose to painful musculoskeletal
      conditions.[39-43] As the initial link in body loading during stance and movement, the feet
      are "where the rubber hits the road." The arch dynamically deforms to distribute the force,
      thereby absorbing the rapid impulse of loading. Changes in foot biomechanics that occur with
      changes in the foot structure alter the normal control of forces propagating from the foot to
      more proximal lower limb joints and the spine,[44] and contribute to pain in the feet, knees,
      hips,[41-43] and low back.

      Possibly the most common cause of such changes in biomechanics is the loss of arch height.
      Excessive pronation strains the supporting structures of the foot and tendons that cross the
      ankle, leads to impaired balance,[45] can strain passive stabilizers such as the Achilles
      tendon, iliotibial band,[46] and anterior cruciate ligament,[47] and can contribute to
      permanent impairments in the soft tissue structures in the lower limbs.[47, 48] Thus,
      excessive pronation has been implicated in numerous musculoskeletal complaints, through
      pathologically re-distributing the ground reaction force over the foot,[49] changing patellar
      tracking in the femoral trochlea,[50] changing the angle of pull of muscular stabilizers in
      the lower limbs, and inducing a functional leg length inequality that alters hip and spine
      loading.[1] Therefore, there is a need to address this gap in knowledge to inform preventive
      interventions if there are musculoskeletal sequellae.

      Biomechanical Changes Contribute to Musculoskeletal Disease Risk As mentioned previously, the
      permanent loss of arch height that occurs in about 40% of women with pregnancy leads to
      excessive pronation of the foot. This foot posture causes increased rotation of the tibia[51]
      and is communicated across the knee. These torques, in turn, may increase compressive and
      shear stress on the medial tibiofemoral and lateral patellofemoral compartments of the knee.
      This is important in light of previous work demonstrating that elevated contact stress is
      predictive of development of incident symptomatic knee osteoarthritis,[52] and the relative
      risk for knee replacement surgery increases with the number of pregnancies carried.[53]
      Closing Knowledge Gaps May Attenuate Musculoskeletal Disease Risk in Women In consideration
      of the evidence to date that pregnancy leads to a drop in the arch and that loss of the arch
      may contribute to musculoskeletal disease and disablement, there is a compelling rationale to
      characterize whether use of arch supports during pregnancy can prevent these adverse changes
      in foot structure during pregnancy. The proposed study will randomize women to either an
      arch-supportive insole or a control group(that does not wear insoles) and will measure static
      and dynamic arch structure in the early part of the first trimester and then again 8 weeks
      postpartum. Successful completion will inform the extent to which loss of arch height with
      pregnancy can be ameliorated using a conservative physical medicine intervention. This line
      of research holds great potential to inform preventive interventions to reduce the
      disproportionate risk for musculoskeletal disease and disability borne by women.
    

Intervention name(s): Insole
Intervention type(s): Device
Intervention description(s): Custom-molded arch-supporting insole
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: pregnancy, arch height, collapsed arch