The influence of the length of lower-limb prosthesis on spinal kinematics.

OBJECTIVE

To examine the immediate effects of a change in prosthetic length on the kinematics of the lumbar spine in lower-limb amputees.

DESIGN

An experimental study with repeated measurements of lumbar spine movements under conditions of different prosthetic lengths.

SETTING

A free-standing rehabilitation center in the United Kingdom.

PARTICIPANTS

Twenty unilateral below-knee amputees.

INTERVENTION: Patients performed anatomic movements of the lumbar spine in standing and a sit-to-stand activity. Changes in prosthetic length were produced by placing a wooden block under the prosthetic and sound legs.

MAIN OUTCOME MEASURES: The positions of the pelvis and the lumbar spine in standing and the movement patterns of the lumbar spine were recorded by an electromagnetic tracking device.

RESULTS

A change in prosthetic length produced lateral tilt of the pelvis and lateral bending of the spine in standing. The mean maximum magnitudes of lateral bending and axial rotation toward the sound and prosthetic sides were different. Subjects exhibited lateral bending and axial rotation when they performed the flexion movement. There were also changes in the direction of coupling between lateral bending and axial rotation in some subjects.

CONCLUSION

A change in prosthetic length or leg-length inequality altered the kinematics of the lumbar spine.