Total ankle replacement along with subtalar joint arthrodesis: In-vitro and in-silico biomechanical investigations.

Total ankle replacement (TAR) and subtalar joint (STJ) fusion, are popular treatments for ankle osteoarthritis (OA). Short endurance limits the former, and movement disability comes with the latter. It is hypothesized here that fusion of the STJ can improve the longevity of the TAR prosthesis. In this study, a fresh human cadaver's ankle joint underwent TAR surgery, and strain patterns in the vicinity of prosthesis were recorded after the application of axial compressive load on tibia, resembling stance phase of the gait. Then, STJ of the same sample fused (FTAR), and a similar test procedure was pursued. The obtained strains in the FTAR were smaller than those of the TAR (p < .01). Finite element models of the tested samples were also made, and validated by experimental strains. The validated FE models were then employed to find stress distribution on the tibial plateau and prosthesis compartments. FTAR demonstrated more regular stress profiles in bone-prosthesis interface. Also, maximum von Mises stress in the talar component of the FTAR is approximately half of that in the TAR (8 and 15 MPa, respectively). Based on the results of this study, having a more symmetric load distribution on the prosthesis after STJ fusion, longevity of the TAR may likely increase.

The effect of a knee ankle foot orthosis incorporating an active knee mechanism on gait of a person with poliomyelitis.

BACKGROUND: The aim of this case study was to identify the effect of a powered stance control knee ankle foot orthosis on the kinematics and temporospatial parameters of walking by a person with poliomyelitis when compared to a knee ankle foot orthosis. CASE DESCRIPTION AND METHODS: A knee ankle foot orthosis was initially manufactured by incorporating drop lock knee joints and custom molded ankle foot orthoses and fitted to a person with poliomyelitis. The orthosis was then adapted by adding electrically activated powered knee joints to provide knee extension torque during stance and also flexion torque in swing phase. Lower limb kinematic and kinetic data plus data for temporospatial parameters were acquired from three test walks using each orthosis. FINDINGS AND OUTCOMES: Walking speed, step length, and vertical and horizontal displacement of the pelvis decreased when walking with the powered stance control knee ankle foot orthosis compared to the knee ankle foot orthosis. When using the powered stance control knee ankle foot orthosis, the knee flexion achieved during swing and also the overall pattern of walking more closely matched that of normal human walking. The reduced walking speed may have caused the smaller compensatory motions detected when the powered stance control knee ankle foot orthosis was used. CONCLUSION: The new powered SCKAFO facilitated controlled knee flexion and extension during ambulation for a volunteer poliomyelitis person.

The effect of an isocentric reciprocating gait orthosis incorporating an active knee mechanism on the gait of a spinal cord injury patient: a single case study.

OBJECTIVE: The aim of this study was to identify the effect of induced knee flexion during gait on the kinematics and temporal-spatial parameters during walking by a patient with spinal cord injury (SCI) through the application of an isocentric reciprocating gait orthosis (IRGO) with a powered knee mechanism. METHODS: Two orthoses were considered and evaluated for an ISCI subject with a T8 level of injury. An IRGO was initially manufactured by incorporating drop lock knee joints and was fabricated with custom molded AFOs to block ankle motion. This orthosis was also adapted with electrically-activated knee joints to provide active knee extension and flexion when disengaged. RESULTS: Walking speed, stride length and cadence were increased 37.5%, 11% and 26%, respectively with the new orthosis as compared to using the IRGO. The vertical and horizontal compensatory motions reduced compared to mechanical IRGO. At end of stance phase, knee joint flexion was 37.5° for the AKIRGO compared to 7° of movement when walking with the IRGO. The overall pattern of walking produced was comparable to that of normal human walking. CONCLUSION: Knee flexion during swing phase resulted in an improved gait performance and also reduction in compensatory motions when compared to a mechanical IRGO.

Evaluation of a novel powered gait orthosis for walking by a spinal cord injury patient.

BACKGROUND: The aim of this case study was to analyze the effect on gait parameters of a new design of powered gait orthosis which applied synchronized motions to both the hip and knee joints when utilized for walking by a spinal cord injury (SCI) patient. CASE DESCRIPTION AND METHODS: Two orthoses were evaluated while worn by an incomplete SCI subject. Gait evaluation was performed when walking with an isocentric reciprocating gait orthosis (IRGO) and compared to that demonstrated by a newly developed powered version. This new orthosis was based on the IRGO superstructure but incorporated powered hip and knee joints using electrically motorized actuators. FINDINGS AND OUTCOMES: These gait parameters were improved when compared to standard IRGO and initial testing with the orthosis with only the hip or the knee joints activated in isolation. Maximum hip flexion and extension angles, as well as the maximum knee flexion and extension angles all increased when walking with the powered RGO compared to the IRGO. CONCLUSIONS: Gait evaluation of this newly developed orthosis showed improvement in measured parameters when compared to walking with an IRGO. Clinical relevance This case study gave the authors confidence to extend the research to a more extensive study with a group of SCI patients.

Design and simulation of a new powered gait orthosis for paraplegic patients.

BACKGROUND AND AIM: This article describes the development and testing of a new powered gait orthosis to potentially assist spinal cord injury patients to walk by producing synchronized hip and knee joint movements. TECHNIQUE: The first evaluation of the orthosis was performed without users, and was followed by evaluation of the orthosis performance using three healthy subjects to test the structure under weight-bearing conditions. The orthosis was primarily evaluated to ascertain its ability to generate appropriate hip and knee motion during walking. The walking experiments replicated the flexion and extension of both the hip and knee produced by the actuators which had previously been demonstrated during the initial computer simulations. DISCUSSION: The results suggest that this new orthosis could be used to assist paraplegic subjects who have adequate ranges of motion and also with weakness or reduced tone to ambulate, and may also be suitable for other subjects with impaired lower limb function (e.g. stroke, poliomyelitis, myelomeningocele and traumatic brain injury provided they do not have increased tone or movement disorders.

Evaluation of a novel powered hip orthosis for walking by a spinal cord injury patient: a single case study.

BACKGROUND: The aim of this case study was to identify the effect of a powered hip orthosis on the kinematics and temporal-spatial parameters of walking by a patient with spinal cord injury (SCI). CASE DESCRIPTION AND METHODS: Two orthoses were evaluated while worn by an incomplete SCI subject with a T-8level of injury. Gait evaluation was performed when walking with an Isocentric Reciprocating Gait Orthosis (IRGO) and compared to that demonstrated by a newly powered version of the orthosis; based on the IRGO superstructure but incorporating powered hip joints using an electrically motorized actuator that produced active hip joint extension and flexion. FINDINGS AND OUTCOMES: The powered hip orthosis, when compared to the IRGO, increased the speed of walking, the step length and also the cadence demonstrated by this subject. Vertical and horizontal compensatory motions with new orthosis decreased. Hip angles when walking with this orthosis were comparative to those demonstrated by normal walking patterns. CONCLUSIONS: The hip actuator produced positive effects on the kinematics and temporal-spatial parameters of gait during level-ground walking trials, resulting in an alternative approach to walking by SCI patients.