| 1. |
- Arndt, A, et al.
(författare)
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Ankle and subtalar kinematics measured with intracortical pins during the stance phase of walking
- 2004
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Ingår i: Foot & ankle international. - : SAGE Publications. - 1071-1007 .- 1944-7876. ; 25:5, s. 357-364
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Tidskriftsartikel (refereegranskat)abstract
- The absence of external landmarks on the talus has rendered the description of ankle and subtalar joint kinematics difficult. Abnormal motion at these joints has, however, been implied in the etiology of an array of lower extremity overuse injuries. Methods: Intracortical pins were inserted under local anesthesia in the tibia, talus, and calcaneus with external marker clusters traced by a video motion analysis system. Kinematic data were collected during walking trials on a flat surface for three subjects. Gait pattern was monitored by comparison of ground reaction force curves during stance phase with and without the pins inserted. Results: Results were presented in terms of helical axis orientation for both joints and the component rotations about these axes. Large intersubject differences were seen in both ankle and subtalar joint helical axis orientation. Maximum rotations over the complete stance phase for the ankle and subtalar joints respectively were: eversion/inversion, 6.3° and 8.3°; dorsiflexion/plantarflexion, 18.7° and 3.7°; and abduction/adduction, 5.0° and 6.1°. Conclusions: The majority of ankle eversion/inversion occurred at the subtalar joint; however, the ankle component cannot be ignored. Abduction/adduction range of motion at the subtalar joint was surprisingly high, indicating that this component motion during walking is not purely attributable to the ankle joint. Future research should include greater subject numbers in order to present more universally applicable results. Clinical Relevance: The in vivo kinematics of the talus during weightbearing activity are poorly understood. The description of this motion may assist in the structuring of clinical rehabilitation and in the design and insertion of ankle joint prostheses.
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| 2. |
- Milgrom, C, et al.
(författare)
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Metatarsal strains are sufficient to cause fatigue fracture during cyclic overloading
- 2002
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Ingår i: Foot & ankle international. - : SAGE Publications. - 1071-1007 .- 1944-7876. ; 23:3, s. 230-235
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Tidskriftsartikel (refereegranskat)abstract
- Human in vivo tibial strains during vigorous walking have not been found to exceed 1200 microstrains. These values are below those found in ex vivo studies (>3000 microstrains) to cause cortical bone fatigue failure, suggesting that an intermediate bone remodeling response may be associated with tibial stress fractures. Metatarsal stress fractures, however, often develop before there is time for such a response to occur. Simultaneous in vivo axial strains were measured at the mid diaphysis of the second metatarsal and the tibia in two subjects. Peak axial metatarsal compression strains and strain rates were significantly higher than those of the tibia during treadmill walking and jogging both barefoot and with running shoes and during simple calisthenics. During barefoot treadmill walking metatarsal compression strains were greater than 2500 microstrains. During one- and two-leg vertical jumps and broad jumping, both metatarsal compression and tension strains were >3000 microstrains. Compression and tension strains in the metatarsus unlike those of the tibia may be sufficiently high even during moderate exertional activities to cause fatigue failure of bone secondary to the number of loading cycles without an intermediate bone remodeling response.
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| 3. |
- Stacoff, A, et al.
(författare)
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Movement coupling at the ankle during the stance phase of running
- 2000
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Ingår i: Foot & ankle international. - : SAGE Publications. - 1071-1007 .- 1944-7876. ; 21:3, s. 232-239
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to quantify movement coupling at the ankle during the stance phase of running using bone-mounted markers. Intracortical bone pins with reflective marker triads were inserted under standard local anaesthesia into the calcaneus and the tibia of five healthy male subjects. The three-dimensional rotations were determined using a joint coordinate system approach. Movement coupling was observed in all test subjects and occurred in phases with considerable individual differences. Between the shoe and the calcaneus coupling increased after midstance which suggested that the test shoes provided more coupling for inversion than for eversion. Movement coupling between calcaneus and tibia was higher in the first phase (from heel strike to midstance) compared with the second phase (from midstance to take-off). This finding is in contrast to previous in-vitro studies but may be explained by the higher vertical loads of the present in-vivo study. Thus, movement coupling measured at the bone level changed throughout the stance phase of running and was found to be far more complex than a simple mitered joint or universal joint model.
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| 4. |
- Westblad, P, et al.
(författare)
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Differences in ankle-joint complex motion during the stance phase of walking as measured by superficial and bone-anchored markers
- 2002
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Ingår i: Foot & ankle international. - : SAGE Publications. - 1071-1007 .- 1944-7876. ; 23:9, s. 856-863
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Tidskriftsartikel (refereegranskat)abstract
- Bones of the ankle-joint complex are difficult to represent with superficial markers and an invasive approach is required to quantify skin movement artifact. Three-dimensional coordinates during gait were first calculated from sets of three superficial markers located on both the lower leg and heel. Intracortical pins equipped with external marker arrays were subsequently inserted in the tibia, talus and calcaneus for further trials. Tibiocalcaneal and talocalcaneal joint helical axis component rotations were calculated. Intersubject motion patterns were comparable. Root mean square (RMS) differences were chosen to describe discrepancies between temporal intracortical pin and superficial marker curves. Results for the tibiocalcaneal rotations inversion / eversion, plantarflexion / dorsiflexion and abduction / adduction were 2.5°, 1.7° and 2.8° respectively. Inversion / eversion about the talocalcaneal joint showed an RMS difference of 2.1°. A systematic over- or underestimation of superficial relative to bone-anchored markers could not be determined.
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| 5. |
- Alonso-Vazquez, A, et al.
(författare)
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The effect of bone quality on the stability of ankle arthrodesis. A finite element study
- 2004
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Ingår i: Foot & Ankle International. - 1944-7876. ; 25:11, s. 840-850
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Tidskriftsartikel (refereegranskat)abstract
- Background: Despite uniform operating techniques, lack of fusion still occurs after ankle arthrodesis. Differences in the biological healing potential may be a factor but the mechanical performance of the arthrodesis construct because of varying bone quality also may be important. Internal compression techniques are preferred because of higher union rates, shorter fusion times, and fewer complications. A three-screw configuration has been shown to be more stable than a two-screw configuration, but it is not obvious when it should be used. Methods: Three-dimensional finite element models of intact and flat-cut ankle arthrodeses were built, using two and three screws in different configurations. Poor bone quality was simulated by decreasing Young's modulus of the bone. The constructs were loaded in torsion and dorsiflexion, and micromotions at the fusion site were measured. Results: Bone quality had a marked effect on the stability at the arthrodesis site. Inserting two screws at 30 degrees relative to the longitudinal axis of the tibia in an intact arthrodesis seemed the best option, especially as bone quality worsened. The addition of a third screw increased the stability at the arthrodesis site. Conclusions: Overall, intact joint surfaces and three-screw fixation, with the lateral and medial screws inserted produced the most stable arthrodesis constructs when bone quality was poor. Clinical Relevance. Ankle arthrodeses are technically demanding because of the shape and small size of the talus. Preoperative planning is an absolute necessity to determine placement and number of screws. This study shows that poor bone quality decreases the stability of the arthrodesis constructs, suggesting that an attempt should be made to create the most stable three-screw configuration. Finite element models can be used as an effective preoperative tool for planning screw number and placement.
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