Answer
to Question 1.
Research At the Oxford Orthopaedic
Engineering Centre published in Spine in 1983 (1) selected a group without back
pain or history of back pain to evaluate the mobility of the normal spine.
It was by examining these x-rays of the standing and flexed positions
that the limitation on the flexion of the lowest two discs became obvious.
At the University of Babol
in Iran about 100 individuals were also chosen who were free of low back pain.
The standing shape, including the angle of wedging of all the lumbar
discs, was evaluated by x-ray and published in 2003 (2). The mobility was
not evaluated in the same research but applying the mobilities
from various publications, such as Adams and Hutton in Spine 1984 (3) or (1)
above, the same limitation is found for the lowest two discs, and only for the
lowest two discs.
A similar evaluation of the mobility of
the normal spine was done by Jonk and Van Niekerk in South Africa (4). This was particularly valuable
because the subjects chosen were black people who were not using cars and
although they were workers at the hospital their lifestyle was probably far
less "western" than any other subjects. Sadly, the x-rays had
already been destroyed by the time that I asked to look at them in the late
1980s but Professor Van Niekerk obtained for me some
new x-rays of tribal living Africans. These confirmed the wedge shape of the
lowest two discs in the standing position. Combining these shapes with
the published mobilities confirmed the limitation on
the flexion of L4-5 and L5-S. The angles were similar to those of the
British group though the wedging of the lowest two discs was slightly greater.
(I see this as probably a lifestyle difference, not a racial one)
(1) Pearcy MJ, Portek I, Shepherd J Three dimensional X-ray analysis of
normal movement in the lumbar spine. Spine 9: 294-297, 1984
(2) N. Kamali EVALUATION
OF TOTAL AND SEGMENTAL LUMBAR LORDOSIS USING RADIOGRAPHIC.... Babol University of Medical Sciences. Quarterly Journal Summer 2003
, Volum 5 , Number 3
(3) Adams MA, Hutton WC The effect
of posture on the lumbar spine. J Bone Joint Surg
(Br) 67B: 625-629, 1985
(4) Jonck LM,
van Niekerk JM A roentgenological study of the motion
of the lumbar spine of the Bantu. South African J Lab Clin
Med 2: 67-71, 1961