Passive Control of Intervertebral Motion in Unilateral Transtibial Amputees
Start date: 31 October 2016
Introduction Lower limb amputees have higher than normal low back pain prevalence  and unsymmetrical stiffness and compression loading in their lumbar spines . However, this has never been explored at an intersegmental level from the standpoint of spine control.
Purpose/Aim This research sought to probe the intersegmental kinematics of the amputee lumbar spine in transtibial amputees in the coronal plane focusing especially on the interactions between levels. The study excluded the effects of loading and muscle control, focussing only on control by the passive holding elements by using a recumbent imaging protocol to measure the restraint from non-contractile tissues under zero axial loading.
Materials and Methods Twelve male unilateral transtibial amputees and 12 matched healthy controls received quantitative fluoroscopy (QF) examinations using an established passive recumbent protocol . This measured the passive left and right intervertebral ranges of motion (IV-RoM) and attainment rates from L2-S1. All amputees also had separate QF studies of their limb-prosthesis interfaces, measuring the extent of tibia-socket telescoping using standardised, simulated gait. Left-right differences in IV-RoM and attainment rates were calculated (Man-Whitney test, p<0.05) as well as correlations (Spearman rank correlation) between levels and directions in terms of these variables. The proportion of levels/directions with significant correlations in amputees and controls were compared (Fisher exact test) as expressions of passive system control. Significant correlations (p<0.05) between limb-prosthesis telescoping range and intervertebral IV-RoMs and attainment rates were also determined. Results There were no significant differences in passive IV-RoM or symmetry between amputees and controls, although both tended to have higher variances in amputees. In both groups there were substantial positive correlations in IV-RoM between opposing bending directions for most levels (Rho=0.699 to 0.902), but no significant differences between them. The same was found for attainment rate, except that a higher proportion of amputees (p<0.05) had significant correlations, both positive at the same level (Rho=0.778 to 0.962), and both negative (Rho=0.-0.545 to -0.811) and positive (Rho=0.510 to 0.748) between levels and directions. There were moderate and significant inverse relationships between seven intervertebral motion parameters and the range of limb-socket telescoping in amputees (Rho= -0.587 to -0.699) (p<0.05).
Implications While spinal movement symmetry is disrupted in amputees  this appears to apply to the active, weight bearing situation and not to the passive, unloaded one. However, the number of apparent intersegmental kinematic interactions related to lower limb amputation suggests that structural adaptations occur in amputees that may be compensatory and a passive form of spine control. Conclusion(s) The passive spinal holding elements (discs, ligaments and resting muscle) exert a greater amount of control of intervertebral restraint in transtibial amputees, as evidenced by a larger number of interactions between and within intervertebral levels. The nature of the apparent structural adaptation to these tissues deserves further investigation in order to deepen our understanding of the non-contractile mechanisms in spine control and their relationships to lifestyle and movement patterns.
Keywords Transtibial amputation, quantitative fluoroscopy, lumbar spine, kinematics, spine control Reference(s) 1. Ehde, D.M., et al., Back Pain as a Secondary Disability in Persons With Lower Limb Amputations. Archives of Physical Medicine and Rehabilitation, 2001. 82: p. 731-734.
2. Hendershot, B.D. and E.J. Wolf, Mediolateral Joint Powers at the Low Back Among Persons With Unilateral Transfemoral Amputation. Archives of Physical Medicine and Rehabilitation, 2015. 96: p. 154-157.
3. Breen, A.C., et al., Measurement of inter-vertebral motion using quantitative fluoroscopy: Report of an international forum and proposal for use in the assessment of degenerative disc disease in the lumbar spine. Advances in Orthopaedics, 2012: p. 1-10.