Walking speed differentially alters spinal loads in persons with traumatic lower limb amputation

Abstract

Persons with lower limb amputation (LLA) perceive altered motions of the trunk/pelvis during activities of daily living as contributing factors for low back pain. When walking (at a singular speed), larger trunk motions among persons with vs. without LLA are associated with larger spinal loads; however, modulating walking speed is necessary in daily life and thus understanding the influences of walking speed on spinal loads in persons with LLA is of particular interest here. Three-dimensional trunk-pelvic kinematics, collected during level-ground walking at self-selected (SSW) and two controlled speeds (∼1.0 and ∼1.4 m/s), were obtained for seventy-eight participants: 26 with transfemoral and 26 with transtibial amputation, and 26 uninjured controls (CTR). Using a kinematics-driven, non-linear finite element model of the lower back, the resultant compressive and mediolateral/anteroposterior shear loads at the L5/S1 spinal level were estimated. Peak values were extracted and compiled. Despite walking slower at SSW speeds (∼0.21 m/s), spinal loads were 8-14% larger among persons with transfemoral amputation vs. CTR. Across all participants, peak compressive, mediolateral, and anteroposterior shear loads increased with increasing walking speed. At the fastest (vs. slowest) controlled speed, these increases were respectively 24-84% and 29-77% larger among persons with LLA relative to CTR. Over time, repeated exposures to these increased spinal loads, particularly at faster walking speeds, may contribute to the elevated risk for low back pain among persons with LLA. Future work should more completely characterize relative risk in daily life between persons with vs. without LLA by analyzing additional activities and tissue-level responses.

Trunk muscle forces and spinal loads in persons with unilateral transfemoral amputation during sit-to-stand and stand-to-sit activities

“…A detailed description of the modeling procedures can be found in our earlier studies (Hendershot et al, 2018;Shojaei et al, 2015;Shojaei et al, 2016a). Briefly, a non-linear finite element model of the spine was used to estimate trunk muscle forces required to complete the activity and the resultant spinal loads using an optimization-based iterative procedure (Bazrgari et al, 2007;Shojaei et al, 2015).…”

“…The associated internal responses from trunk muscles along with the resultant spinal loads have further been shown to be substantially larger among persons with LLA (Hendershot et al, 2018;Shojaei et al, 2016a). For instance, spinal loads at the L5-S1 spinal level during walking at a self-selected pace were reported to be 8-14% larger in persons with LLA, despite having a slower selfselected pace compared to uninjured individuals (Hendershot et al, 2018). Such differences in trunk muscle forces and spinal loads were more exaggerated when using controlled walking paces (Shojaei et al, 2016a).…”

“…Alterations and asymmetries in trunk motions/postures during activities of daily living have been reported in persons with unilateral lower limb amputation (LLA) (Cappozzo and Gazzani, 1982;Hendershot and Wolf, 2014;Rueda et al, 2013;Sagawa et al, 2011;Yoder et al, 2015). Such changes in the way an activity is performed adversely affect the mechanical demand of the activity on the lower back Wolf, 2014, 2015;Shojaei et al, 2016b), are associated with changes in the synergy between the active and passive responses of lower back tissues to equilibrium and stability requirements of the spine (Hendershot et al, 2013;Hendershot and Nussbaum, 2014), and likely result in larger spinal loads (Hendershot et al, 2018;Shojaei et al, 2016a). Importantly, given the repetitive nature of most activities of daily living, even a moderate increase in spinal loads across activities of daily living can pose a risk for development of low back pain (LBP) due to cumulative changes and fatigue failure of spinal tissues (Adams et al, 2006;Coenen et al, 2014;Kumar, 1990).…”

“…Walking has been shown to be mechanically more demanding on the lower back of persons with versus without LLA (Hendershot and Wolf, 2014). The associated internal responses from trunk muscles along with the resultant spinal loads have further been shown to be substantially larger among persons with LLA (Hendershot et al, 2018;Shojaei et al, 2016a). For instance, spinal loads at the L5-S1 spinal level during walking at a self-selected pace were reported to be 8-14% larger in persons with LLA, despite having a slower selfselected pace compared to uninjured individuals (Hendershot et al, 2018).…”

“…Specifically, the sum of forces in muscles attached to the lumbar (i.e., local muscles) /thoracic (i.e., global muscles) spine, and the resultant compression and medio-lateral and antero-posterior shear forces at the L5-S1 spinal level during walking at 1.35 m/s were respectively 23%, 64%, 39%, 60%, and 43% larger among persons with LLA. Furthermore, increasing walking pace is associated with larger increases in spinal loads in persons with versus without LLA (Hendershot et al, 2018). While there are activities of daily living other than walking that are also repetitive and/or demanding (e.g., sit-to-stand), there is limited information related to the differences in trunk muscle forces and spinal loads between persons with and without LLA when performing such activities.…”