Biomedical subjects

Darren Stefanyshyn

Publications and source records attributed to Darren Stefanyshyn.

5 recordsLinked to original sources

PubMed2004

Increased shoe bending stiffness increases sprint performance.

The purposes of this investigation were to determine if increasing the bending stiffness of sprint shoes increases sprinting performance and to determine whether simple anthropometric factors can be used to predict shoe bending stiffness for optimal performance. Thirty-four athletes were tested using four different shoe conditions--a standard condition consisting of their currently used footwear and three conditions where the bending stiffness was increased systematically. The sprinters performed maximal effort 40 m sprints and their sprint times were recorded from 20 to 40 m. On average, increasing the shoe bending stiffness increased sprint performance. The stiffness each athlete required for his or her maximal performance was subject specific but was not related to subject mass, height, shoe size or skill level. It is speculated that individual differences in the force-length and force-velocity relationships of the calf muscles may influence the appropriate shoe stiffness for each athlete to obtain their maximal performance.

Anthropometry↗

PubMed2003

Kinematic changes after fusion and total replacement of the ankle: part 1: Range of motion.

BACKGROUND: The purpose of this study was to determine how closely the present designs of ankle prostheses mimic the unique requirements of the foot and ankle. The three-dimensional range of motion (ROM) of the ankle joint complex, before and after ankle arthrodesis and after implantation of three currently used total ankle prostheses, was investigated. METHODS: The three-dimensional ROM was determined in six fresh-frozen cadaver leg specimens using a 6-df device with an axial load of 200 N and a four-camera high-speed video system. A moment of 100 Nm was applied to the footplate to determine the ROM in the sagittal (dorsiflexion and plantarflexion) and frontal (inversion and eversion) planes. The same moment was applied to the tibia to determine the ROM for the internal and external tibial rotation. The measurements were performed for the normal ankle, the fused ankle, and the AGILITY, HINTEGRA, and S.T.A.R. prostheses. RESULTS: Compared to the normal condition, the ROM for dorsiflexion and plantarflexion was changed for all surgical interventions. The changes were highest for the ankle arthrodesis. The changes due to the prostheses were significantly less than the changes due to ankle arthrodesis. Compared to the normal condition, the total ROM for inversion/eversion was slightly decreased by the fused ankle and not changed by the three-component prostheses (HINTEGRA, S.T.A.R.). However, the ROM for inversion/eversion was significantly higher for the two-component prosthesis, AGILITY. The ROM for internal and external tibial rotation was not altered by the AGILITY and HINTEGRA ankle, but it was significantly reduced by the ankle arthrodesis. S.T.A.R. showed a significant shift of the total ROM toward internal tibial rotation. CONCLUSIONS: The three tested ankle joint prostheses changed the ROM of the ankle joint complex less than ankle fusion did. Total ankle prostheses were shown to replicate normal joint ROM closely. However, ankle arthrodesis was found to reduce the ROM substantially in all three planes: the sagittal, frontal, and horizontal planes. CLINICAL IMPLICATIONS: With respect to the ROM, total ankle replacement changes the natural ankle joint condition less than ankle arthrodesis, which reduces the ROM in all three planes and might increase stress in adjacent structures. The prosthesis that replicated the normal ankle joint ROM best was the one with the most anatomical design.

Aged↗

PubMed2003

Kinematic changes after fusion and total replacement of the ankle: part 2: Movement transfer.

INTRODUCTION: The purpose of this in vitro study was to determine the biomechanical characteristics of the ankle based on the movement transfer between foot and leg before and after ankle arthrodesis, and after implantation of three currently used total ankle prostheses. METHODS: A 6-df device with an axial load of 200 N and a four-camera high-speed video system were used for the measurement of the range of motion in six fresh-frozen cadaveric leg specimens. While the foot was moved through the range of dorsiflexion/plantarflexion, the resulting foot eversion/inversion and tibial rotation were recorded. Analogously, the resulting foot eversion/inversion from tibial rotation and, vice versa, the resulting tibial rotation from foot eversion/inversion were determined. The same measurements were performed for the normal ankle, the fused ankle, and after total ankle replacement by the AGILITY, HINTEGRA, and S.T.A.R. prostheses. RESULTS: While in dorsiflexion/plantarflexion of the foot, ankle joint fusion increased the movement transfer to tibial rotation by a 2.4 factor and to eversion/inversion by a 18.5 factor, whereas, this movement transfer did not change for all prostheses conditions. The movement transfer between foot eversion and tibial rotation was found to decrease for all ankle prostheses, but more in the AGILITY and S.T.A.R. prosthesis than in the HINTEGRA. CONCLUSIONS: The three tested ankle joint prostheses changed the movement transferred within the ankle joint complex less than ankle fusion did, especially for dorsiflexion/plantarflexion movement of the foot. The closer the design was to the normal anatomy of the ankle, the closer the transfer of movement was shown to be replicated with respect to normal joint. It is suggested that success of total ankle arthroplasty depends on how successfully designs can mimic the movement transfer of the normal ankle, while dissipating the rotational forces and maintaining the stability of the joint.

Aged↗

PubMed2003

Kinematic changes after fusion and total replacement of the ankle: part 3: Talar movement.

INTRODUCTION: The purpose of this study was to determine talar movement (e.g., talar rotation and talar shift during (dorsiflexion/plantarflexion) with respect to the tibia in the normal ankle, in the fused ankle, and in the replaced ankle by currently used prosthetic designs. METHODS: A 6-df device with an axial load of 200 N and a four-camera high-speed video system were used for the measurement of the range of motion in six fresh-frozen cadaveri leg specimens. While moving the foot through the whole range of motion for plantarflexion/dorsiflexion, segmental motion of the marked bones of the foot and shank were measured dynamically. Rotation and medial-lateral shift of the talus were then calculated with regard to flexion position of the foot. RESULTS: In the normal ankle, plantarflexion movement was coupled with talar inversion of 3.5 degrees, and dorsiflexion movement with talar eversion of 1.0 degree, in totally accounting for 4.5 degrees of talar rotation. While both the HINTEGRA and the S.T.A.R. prostheses did not show changes to the normal condition during the dorsiflexion/plantarflexion cycle (p < .05), talar rotation had a 60% decrease (p < .05) for the AGILITY prosthesis. In the normal ankle joint, a lateral talar shift of 1.4 mm was found to occur during dorsiflexion, and a lateral talar shift of 5.2 mm during plantarflexion. In both, the HINTEGRA and S.T.A.R. ankles, talar shift was converted into medial direction during dorsiflexion of the foot (difference to normal: p < .05), whereas talar shift in the lateral direction was found to occur during plantarflexion of the foot which was comparable to the normal ankle. The AGILITY ankle evidenced an 80% decrease of talar shift (p < .05) during the whole dorsiflexion/plantarflexion cycle. DISCUSSION: The two-component ankle (AGILITY) obviously tends to restrict tremendously talar motion within the ankle mortise, whereas the three-component ankles (HINTEGRA, S.T.A.R.) seem to allow talar range of motion comparable to that in the normal ankle. It is suggested that such a restriction of talar motion results in an increase of stress forces within and around the prosthesis, leading to polyethylene wear and potential loosening at the bone-implant interfaces. Therefore, a successful prosthetic design for the ankle should consist of three components that are shaped as anatomically as possible to provide a normal range of motion and to allow the full transmission of movement transfer between foot and shank and unconstrained movement of the talus within the ankle mortise.

Aged↗

PubMed2003

Effect of shoe inserts on kinematics, center of pressure, and leg joint moments during running.

PURPOSE: The purposes of this project were to assess the effect of four different shoe inserts on the path of the center of pressure (COP), to quantify the effect of these inserts on selected knee joint moments during running, and to assess the potential of COP data to predict the effects of inserts/orthotics on knee joint moments. METHODS: Kinematics for the lower extremities, resultant ankle and knee joint moments, and the path of the COP were collected from the right foot of 15 male subjects while running heel-toe with five different shoe inserts (full or half with 4.5-mm postings). RESULTS: Individual movement changes with respect to the neutral insert condition were typically small and not systematic. Significant changes for the path of the COP were registered only for the full lateral insert condition with an average shift toward the lateral side. The mediolateral shift of the COP was not consistent for the full medial and the two half-shoe inserts. The subject-specific reactions to the inserts' intervention in the corresponding knee joint moments were typically not consistent. Compared with the neutral insert condition, subjects showed increases or decreases of the knee joint moments. The correlation between the individual COP shifts and the resultant knee joint moment was generally small. CONCLUSION: The results of this study showed that subject-specific reactions to the tested inserts were often not as expected. Additionally, reactions were not consistent between the subjects. This result suggests that the prescription of inserts and/or orthotics is a difficult task and that methods must be developed to test and assess these effects. Such methods, however, are not currently available.

Adult↗