The pattern of tibial nerve excursion with active ankle dorsiflexion is different in older people with diabetes mellitus

Abstract

Background The peripheral nervous system has an inherent capability to tolerate the gliding (excursion), stretching (increased strain), and compression associated with limb motions necessary for functional activities. The biomechanical properties during joint movements are well studied but the influence of other factors such as limb pre-positioning, age and the effects of diabetes mellitus are not well established for the lower extremity. The purposes of this pilot study were to compare the impact of two different hip positions on lower extremity nerve biomechanics during an active ankle dorsiflexion motion in healthy individuals and to determine whether nerve biomechanics are altered in older individuals with diabetes mellitus. Methods Ultrasound imaging was used to quantify longitudinal motion of the tibial nerve and transverse plane motion of the tibial and common fibular nerves in the popliteal fossa during active ankle movements. Findings In healthy individuals, ankle dorsiflexion created mean tibial nerve movement of 2.18 millimeters distally, 1.36 millimeters medially and 3.98 millimeters superficially. When the hip was in a flexed position there was a mean three-fold reduction in distal movement. In people with diabetes mellitus there was significantly less distal movement of the tibial nerve in the neutral hip position and less superficial movement of the nerve in both hip positions compared to healthy individuals. Interpretation We have documented reductions in tibial nerve excursion due to limb pre-positioning thought to pre-load the nervous system using a non-invasive methodology. Thus, lower limb pre-positioning impacts nerve biomechanics during ankle motions common in functional activities. Additionally, our findings indicate that nerve biomechanics have the potential to be altered in older individuals with diabetes mellitus compared to younger healthy individuals.

Non-invasive assessment of sciatic nerve stiffness during human ankle motion using ultrasound shear wave elastography

“…The mechanical properties of peripheral nerves have been extensively examined in animal models Millesi et al, 1995), human cadaver studies (Boyd et al, 2013;Coppieters et al, 2006) and human in vivo studies (Boyd et al, 2012;Ellis et al, 2012). The majority of in vivo studies used ultrasound imaging to quantify nerve excursion and morphology (e.g., cross sectional area) (Beekman and Visser, 2004;Dilley et al, 2001;Silva et al, 2014).…”

Sciatic nerve excursion during a modified passive straight leg raise test in asymptomatic participants and participants with spinally referred leg pain

“…The depth of the sciatic nerve in the posterior thigh varied between 3 and 6 mm, and the quality of the nerve image also tended to reduce with increasing age. In addition, substantially larger longitudinal excursion was evoked by the knee movements performed in the present study, compared to Boyd et al (2012) where the ankle was moved. Thus larger amounts of longitudinal nerve excursion with accompanying greater transverse plane motion, and distortion in some cases made it more technically challenging to capture a clear image.…”

“…Whilst Boyd et al (2012) has found the centroid method to be reliable, this may be because the tibial nerve is more superficial at both the posterior knee and medial ankle, which results in a better resolution of images. The depth of the sciatic nerve in the posterior thigh varied between 3 and 6 mm, and the quality of the nerve image also tended to reduce with increasing age.…”

Provocative mechanical tests of the peripheral nervous system affect the joint torque‐angle during passive knee motion

“…Flexing the hip produces a threefold reduction in the amount of longitudinal tibial nerve movement during ankle dorsiflexion (Boyd et al., ). This finding supports the premise that positioning the body limb in a manner that increases the preloading on the nervous system diminishes the nerve excursion capacity during limb movement.…”