Subjects
The quasi-experimental study design with repeated measurements was used to investigate
the lumbar lordosis changes during PLKF in two groups: subjects with chronic non-specific
LBP (N?=?40, average age: 40.84 [SD?=?17.59] years old, average height: 165.0 [SD?=?9.0]
cm, average weight: 70.31 [SD?=?16.06] kg, body mass index (BMI): 25.55 [SD?=?3.99]
kg/m2) and subjects with no history of LBP (N?=?40, average age: 23.57 [SD?=?10.61] years
old, average height: 162.0 [SD?=?7.0] cm, average weight: 55.62 [SD?=?6.55] kg, BMI:
21.05 [SD?=?2.26] kg/m2).
Power analysis was used to determine the sample size for test. Type I error (?) was
set at 0.05 and power of the test was 0.80. Considering this, the calculated sample
size showed that sample size in this study was appropriate to test the hypothesis
and the results derived from the study are meaningful.
The subject population in this study was a sample of convenience. The LBP patients
were referred by orthopedic specialist and physiotherapy clinics. The patients were
included if they had a history of non-specific LBP for more than six weeks duration
before the study date. They were also included if had intermittent (on and off) LBP
with at least three previous episodes each lasting more than one week, during the
year before the study 16].
The control group was evaluated and found to have no complaint of any pain or dysfunction
in their low back, pelvis, thoracic and lower extremities. The healthy subjects were
recruited from the university students.
The exclusion criteria in both groups were pregnancy, history of dyspnea, history
of hip pain, dislocation or fracture, history of lumbar spine surgeries, history of
anterior knee ligament injury or rupture, history of anterior knee pain, inability
to perform active PLKF without pain, history of lower extremity injury in the past
3Â months, shortness of hip flexors, positive neurological symptoms and cardiopulmonary
disorders. Each eligible subject was enrolled after signing an informed consent form
approved by the human subjects committee at the University of Social Welfare and Rehabilitation
Sciences. Ethical approval for this study was granted from the internal ethics committee
at the University of Social Welfare and Rehabilitation Sciences (Date: 2013.03.09).
Procedures
The subject was on the examining table in the prone position. The lumbar lordosis
was measured first in prone position. Then the subject was asked to perform knee flexion
(PLKF) and then the lumbar lordosis was measured after PLKF test in both subjects
with and without LBP. The dominant leg was chosen for investigation.
Measuring lumbar lordosis
A standard flexible ruler was used to measure the degree of lumbar lordosis in prone
position before and after active knee flexion (Figure 1). For this purpose, the subject’s position was prone lying on a treatment table with
the arms along the sides and head face was down. The base of sacrum and spinous process
of L1 was located by palpation and marked with removable stickers.
Figure 1. Measurement of lumbar lordosis with flexible ruler in prone position and active PLKF.
A standard flexible ruler was fitted on subject’s lumbar curve, over the lumbar spinous
processes of L1 – S1. The curve of the flexible ruler, resembling the size of subject’s
lumbar curvature, was graphed on a paper, noting where the two reference points for
L1 and S1 were located. The method explained by others was used to quantify the degree
of lumbar lordosis 16]-20].
Two points on the curve, representing L1 and S1, were connected by a line (L). A perpendicular
line (H), representing the height of the lumbar curve, bisected line L. The length
of each line was calculated in millimeters, and the values were used in the following
formula to calculate the degree of lumbar lordosis.
A very high correlation (r?=?0.92) has been found between degrees of lumbar lordosis
measured by a flexible ruler and from lumbar X-rays 21]-23]. The reliability of flexible curve for measurement of lumbar lordosis has been previously
established 24].
Data analysis
Statistical analysis was performed using SPSS version 16.0.
A paired t-test was used to demonstrate changes in lumbar lordosis before and after PLKF test
in both subjects with and without LBP.
An independent t-test was used to compare changes in lumbar lordosis during PLKF between subjects
with and without LBP and also to compare demographic data between subjects with and
without LBP. Statistical significance was attributed to P value less than 0.05.
Ethical approval
This research was reviewed and was approved by the Human Subject Committee at University
of Social Welfare and Rehabilitation Sciences.