Table 1.

Experimental studies on the deformation as aetiological factor for DTI in transtibial prosthetic users

Author and year	Objective	Loading scenario	Study Population	Quantitative Results	Qualitative results
Portnoy et al. 2007 [29]	Test of feasibility of real-time FEa monitor to estimate internal tissue load	Dynamic load: Treadmill walking	- 5 unilateral TTAbs - 1 female, 4 male - Mean age 47.2 yrs. - Mean weight 68 kg	Max. principal compression stresses: - Fibular axis: 16.38 kPa (3.5 - 31 kPa) - Gastrocnemius axis: 8.19 kPa (1.75 - 13 kPa)	- Maximum compressive stress between midstance and push-off - High inter-patient variability in stress magnitude
Portnoy et al. 2008 [34]	Estimation of internal tissue load during static load bearing	Static load: Weight bearing	- 1 unilateral TTA - Female - Age 29 - Weight 50 kg - Traumatic cause	- Compressive stress 240 kPa - Tensile stress 263 kPa - Shear stress 23 kPa - Compressive strain 85% - Tensile strain 129% - Shear strain 106% - SEDc 104 kJ/m3 - Von Mises stress 215 kPa	- Compression slightly above physiological levels in comparison to gluteal tolerance - High tensile and shear strains which may be risk for tissue viability - Stress and strain concentrations in flap under tibial end
Portnoy et al. 2010 [31]	Determination of subject-specific dynamic stresses in soft tissues	Dynamic load: Walking on complex terrain	- 18 unilateral TTAs - 1 female, 17 male - Mean age 43 yrs. - Mean weight 79 kg - 11 traumatic, 7 vascular	Average peak von Mises stress: - Plane: 100 kPa - Grass: 80 kPa - Upstairs: 95.1 kPa - Up slope: 83 kPa - Downstairs: 115.4 kPa - Down slope: 141.9 kPa	- High inter-terrain and inter-subject variability - Higher stresses in vascular compared to traumatic patients - No immediate risk of DTI for 10 out of 18 subjects - Elevated peak stress when descending stairs or slope compared to plane gait
Portnoy et al. 2011 [33]	Evaluation of risk of DTI development for during sitting with a donned prosthesis	Static loading: Sitting with 30° and 90° knee flexion	- 1 unilateral TTA - Male - Age 55 - Weight 73 kg Traumatic cause	At tibial end (90° flexion): - Principal stress: Compression 102.9 kPa Tension 66.6 kPa - Shear stress 67.2 kPa - Von Mises stress 129 kPa Volume of damaged area (after 75 min): - 30°: 13.5mm3 - 90°: 600mm3	- Residuum at risk of DTI during sitting with 90° flexion - Risk of DTI posture dependent - Injury rate higher with increased knee flexion - Damage volume may be dependent on muscle thickness

^aFinite element; ^bTranstibial amputee; ^cStrain Energy Density