[A study on senile postural deformity].

One hundred and twenty-eight aged people were divided into four groups to elucidate the mechanism of senile spinal deformity: extended type, S-shaped type, flexed type and hand-on-the-lap type. Except for S-shaped type, the major cause of anterior stooping of the spine was lumbar disc degeneration. The paraspinal muscles prevent anterior stooping. In case the muscles cannot compensate the anterior stooping, the spine can be taken back straight by posterior pelvic tilting. Posterior pelvic tilting is obtained by extension of the hip joint and flexion of the knee joint. Knee flexion up to 25 or 30 degrees serves to correct this pelvic tilting, but can cause patellofemoral osteoarthritic changes. When the knee of an aged person exceeds this angle, the individual will assume hand-on-the-lap posture. In aged people spinal deformity is thus compensated by the lower extremity. The spine and lower extremity should be regarded as a single musculoskeletal unit.