DOES THE HIP FLEXION ANGLE CHANGE WHEN THE POSITION OF THE PELVIS AND THE LUMBAR VERTEBRA IS CHANGED IN STAGES? COMPARISON OF YOUNGER AND MIDDLE AGE GROUPS

Introduction

In the previous study regarding the relationship among maximum hip flexion, the pelvis, and the lumbar vertebrae on the sagittal plane, we have found in X-rays that the lumbo lordotic angle (LLA) and the sacral slope angle (SSA) have a large impact on hip flexion angle. We examined hip flexion angles to the various height of the objects (half round plastic tube) placed under the subject's lower back and compared the passive hip flexion angles in the supine position between younger and middle age groups.

Participants

The participants were 14 healthy volunteers: 7 females with an average age of 17 years (Group 1: G-1), 7 females with an average age of 45 years (Group 2: G-2). The average BMI (Body Mass Index) of volunteers was less than 25, and their Tomas Tests were negative.

Methods

The hip flexion angle was measured in six stages as half round plastic tube placed under the subject's lower back gradually increased in height by 5mm. StageZero is the Regular Position with nothing placed under the subject's lower back: RP (specified Japanese Orthopedics Association and Rehabilitation Medical Association). The next five stages (from Stage One) were performed in the Limited Position (LP) of the posterior pelvic tilt and lumbar movement by placing the tube under the subject's lower back. The height of tube is 2.2 cm. Stage One started at 2.2cm. Each Stage from Stage One has a difference in the height of 5mm.

Stage Zero: 0cm, Stage 1: 2.2cm, Stage 2: 2.7cm, Stage 3: 3.2cm, Stage 4: 3.7cm, Stage 5: 4.2cm,

Analysis

We compared the hip flexion angle of six stages of the two groups. A two-way repeated measurement ANOVA was used to compare the differences in hip flexion angle of G1 and G2. Statistical significant was established at p < 0.05. Further, we took X-rays of a healthy female and examined the LLA, SSA, and Lumbo Sacral Angle (LSA) during hip maximum flexion.

Results & Discussion

In RP (Stage Zero), the LLA and the SSA had a large impact on hip flexion angle observed in X-rays. In Stages1-6, there was a slight movement in the LLA and the SSA. The higher the tubes’ height, the smaller the hip flexion angle. When the height was low, the posterior pelvic tilt became large, resulting in a larger hip flexion angle. The fulcrum rotational point of the hip flexion would move to the lumbar side. We need to determine and tailor the height of object to each individual lumbar lordosis.