Biomedical subjects

G F Kogler

Publications and source records attributed to G F Kogler.

6 recordsLinked to original sources

PubMed2001

The effect of heel elevation on strain within the plantar aponeurosis: in vitro study.

Mild, temporary reduction of symptoms from plantar fasciitis have been reported with the use of high heeled shoes (i.e. cowboy boots, ladies pumps). However, little is known on how heel elevation may contribute to a decrease in the pain and inflammation. The aim of this study was to quantify strain in the plantar aponeurosis in cadaveric feet with the use of various heel elevation configurations. An in vitro method that simulated "static" stance was used to determine the loading characteristics of the plantar aponeurosis (n = 12). Heel elevation was evaluated with blocks placed beneath the heel and with a contoured platform that simulated the arch profile of a shoe at three different heel heights (2.0, 4.0, 6.0 cm) with a level plane serving as the control. Strain in the plantar aponeurosis decreased with elevations of the heel that simulated the arch profile of a shoe at load levels (337, 450 N) (P < 0.05). Elevations of the heel with blocks did not significantly affect strain in the plantar aponeurosis (P < 0.05). Contrasting results of some specimen limbs compared with the overall means suggests that the influence of heel elevation on loading of the plantar aponeurosis may be dependent on individual variation and foot structure differences. Therefore, clinicians should be cautious in recommending heel elevation as a treatment for plantar fasciitis since some subjects may not achieve the desired decrease in plantar aponeurosis strain.

Adult↗

PubMed1999

The influence of medial and lateral placement of orthotic wedges on loading of the plantar aponeurosis.

BACKGROUND: Repetitive trauma and overuse of the plantar aponeurosis are believed to be causal factors of plantar fasciitis. Therefore, it is important to know how an orthosis influences loading of the plantar aponeurosis. The aim of this study was to quantify strain in the plantar aponeurosis in cadaveric feet with the use of various combinations of orthotic wedges. METHODS: An in vitro test that simulated static stance was used to determine the loading characteristics of the plantar aponeurosis. A differential variable reluctance transducer was operatively implanted into the plantar aponeurosis of nine fresh-frozen cadaveric lower limbs. Each specimen was mounted in an electromechanical testing machine that applied an axial load of as much as 900 newtons to the tibia. Eight different combinations of test conditions, in which wedges (each with a 6-degree incline) were or were not positioned under the medial and lateral aspects of the forefoot and hindfoot, were evaluated, with the plantigrade foot used as a neutral control. RESULTS: Each of the test conditions that involved a wedge under the forefoot resulted in strain that was significantly different from that in the neutral control. A wedge under the lateral aspect of the forefoot decreased strain in the plantar aponeurosis, and a wedge under the medial aspect increased strain (p < 0.05). The test conditions that involved a wedge under the hindfoot but not under the forefoot resulted in strains that were not significantly different from those in the neutral control (p > 0.05). CONCLUSIONS: A wedge under the lateral aspect of the forefoot transmits loads through the lateral support structures of the foot, locking the calcaneocuboid joint and decreasing strain in the plantar aponeurosis. A wedge under the medial aspect of the forefoot transmits loads through the medial support structures of the foot, which produces a truss-like action that increases strain in the plantar aponeurosis.

Cadaver↗

PubMed1999

Static structural testing of trans-tibial composite sockets.

The purpose of this investigation was to quantify the structural strength of various trans-tibial composite sockets. To conduct the study, loading parameters and methods were developed that emulate the International Standards Organisation (ISO) standards for structural testing of lower limb prostheses since specific guidelines for the testing of the trans-tibial socket portion of a prosthesis have not yet been established. The experimental set-up simulated the instant of maximum loading during the late stance phase of gait. Ten trans-tibial sockets were evaluated. Five different reinforcement materials and two resin types were used to construct the sockets. A standard four hole distal attachment plate was used to connect the socket and pylon. Each sample was loaded to failure in a servo-hydraulic materials test machine at 100 N/s. None of the composites in the study met the ISO 10328 standards for level A100, loading condition II (4025 N), as required for other prosthetic componentry. All failures occurred at the site of the pyramid attachment plate. Ultimate strength and failure type were material dependent. Load point deflection was significantly different for the resin variable (p<0.05). Statistical differences according to reinforcement material were noted in composite weight and strength-to-weight ratio (p<0.05). The fibre volume fraction was also estimated and recorded. Reinforcement material type was the primary determinant of performance for the tested samples. Carbon reinforcements performed better than fibreglass reinforcements of similar weave type. The greatest ultimate strength and strength-to-weight ratio was observed with the unidirectional carbon reinforcement.

Acrylic Resins↗

PubMed1996

Biomechanics of longitudinal arch support mechanisms in foot orthoses and their effect on plantar aponeurosis strain.

OBJECTIVE: The purpose of this investigation was to quantify the longitudinal arch support properties of several types of foot orthosis. DESIGN: An in vitro method that simulated 'static stance' was used to determine arch support capabilities, with plantar aponeurosis strain implemented as the performance measure. BACKGROUND: A longitudinal arch support mechanism of an orthosis resists depression of the foot's arches by transferring a portion of the load to the medial structures of the foot. Since the plantar aponeurosis is in tension when the foot is loaded, a quantifiable decrease in strain should occur with an adequate orthotic arch control mechanism. METHODS: A differential variable reluctance transducer was surgically implanted in the plantar aponeurosis of cadaveric donor limb feet (n = 7). Each specimen was mounted in an electromechanical test machine which applied a load of up to 900 N axially to the tibia. The test schedule was divided into seven test conditions: specimen barefoot; specimen with shoe and specimen with shoe and five different orthoses. RESULTS: The University of California Biomechanics Laboratory Shoe Insert and two other foot orthoses significantly decreased the strain in the plantar aponeurosis compared to the barefoot control and were considered effective arch supports (P < 0.05). The functional foot orthosis, stock orthosis, and test shoe did not effectively reduce plantar aponeurosis strain. Significant variations of time required to achieve the specified load levels were recorded among the test conditions, indicating the relative cushioning properties of the shoe/orthosis systems. CONCLUSIONS: The patterns of plantar aponeurosis strain observed in cadaveric tests suggest that certain types of orthoses are more effective than others in the support of the foot's longitudinal arches. It is suggested that to support the longitudinal arches of the foot effectively the medial surface contours of the orthosis must stabilize the apical bony structure of the foot's arch. RELEVANCE: Reducing tension in the plantar aponeurosis is an important treatment objective for orthotic management of plantar fasciitis. Therefore it is of great clinical interest to know whether the longitudinal arch support mechanism of specific foot orthoses have benefits with respect to the loading of the plantar aponeurosis.

Journal Article↗

PubMed1995

In vitro method for quantifying the effectiveness of the longitudinal arch support mechanism of a foot orthosis.

The purpose of this investigation was to develop a technique to quantify the effectiveness of the longitudinal arch support mechanism of a foot orthosis. The experimental model was based on the following principle of foot biomechanics: as the foot is subjected to a load, a proportion of the load is experienced as tension by the plantar aponeurosis. A differential variable reluctance transducer was implanted into the plantar aponeuroses of cadaveric lower limb feet through which the strain was calculated in three conditions, specimen barefoot, specimen with shoe, and specimen with shoe and orthosis. Each donor limb was mounted in an electromechanical test machine that applied a load of 900 N to the tibia. Time, load, and strain data were collected and analysed at four load levels (225, 450, 675, 900 N). In addition the measurements and test design were evaluated for reliability. Strain in the plantar aponeurosis decreased significantly in the specimen with shoe and orthosis compared to the specimen with shoe only. There was a significant increase in the time to load data in the specimen with shoe and orthosis condition in contrast to the barefoot measurements. There were no significant differences in strain between the barefoot tests and those of the shoe, indicating that the shoe tested provided minimal support to the foot's longitudinal arch. RELEVANCE: One of the most common foot pathologies that patients seek medical attention for is plantar fasciitis. The primary cause of this condition is excessive tension in the plantar aponeurosis. A foot orthosis is often prescribed for treatment, relying on its longitudinal arch support mechanism to relieve the strain in the plantar aponeurosis. Quantifying the amount of strain experienced by the plantar aponeurosis is needed to identify how effective foot orthoses are in providing support to the foot's longitudinal arches. Such information is of importance to the medical practitioner who is involved with orthotic clinical recommendations. The described method will also be useful to bioengineers concerned with the arch support component of running shoes.

Journal Article↗

PubMed1992

Posterior tibial tendon dysfunction.

Posterior tibial tendon dysfunction, a common entity, frequently is unrecognized and inappropriately managed. Acutely, pain and swelling are present over the medial ankle and longitudinal arch. Long-standing inflammation can lead to tendon rupture, resulting in a progressive planovalgus or "flat foot" deformity. Plain radiographs illustrate the changes in bony anatomy associated with chronic posterior tibial deficiency, while magnetic resonance imaging scans can identify the three stages of posterior tibial tendon pathology. Most cases are amenable to conservative therapy, including rest and administration of nonsteroidal antiflammatory agents. Often a short period of immobilization in a cast or the use of an orthosis is beneficial. In cases with persistent tenosynovitis, complete tendon rupture, or progressive deformity, surgical intervention is indicated.

Biomechanical Phenomena↗