Graham Arnold

Repeatability of the Pedar-X in-shoe pressure measuring system.

BACKGROUND The Pedar-X is one of the newer versions of in-shoe pressure measuring devices and the current study aimed to assess the repeatability of this device. METHODS Twenty-seven healthy male volunteers were recruited and requested to walk on a 26-feet walkway wearing appropriate sized standardised off-the-shelf neutral running shoes (Donnay International). The Pedar-X insole was sandwiched between the foot and the shoe. Data were collected on two occasions, one week apart. Clinically relevant parameters studied were contact area, contact time in percentage roll over process, maximum force, pressure-time integral, force-time integral, peak pressure, mean force and mean area. RESULTS Repeatability was analysed using the coefficient of variation. Of the 160 parameters considered, 93.1% revealed a coefficient of variation value of less than 25. Heel and the metatarsal head areas were the most repeatable. CONCLUSION The Pedar-X in-shoe pressure measuring system is repeatable and as such can be used as a valuable tool in the assessment of in-shoe plantar pressure distribution.

Foot pressure differences in men and women

BACKGROUND Women and men are anatomically and physiologically different in a number of ways. Anthropometric studies have shown considerable differences in the foot bones of both genders. These differences could potentially mean different foot pressures in men and women. OBJECTIVE The aim of our study was to investigate any potential foot pressure differences between males and females using the Pedar-M (Novel gmbh, Germany) in-shoe foot pressure measurement system. METHODS Twenty-eight subjects (16 females and 12 males) were recruited. Peak pressure, contact area, contact time, pressure-time integral, force-time integral, instant of peak pressure, maximum force and mean force were recorded and subsequently analysed. RESULTS In males, contact area was significantly larger in all regions of the foot compared with females. There were no significant between gender differences in peak pressure, contact time, pressure-time integral and instant of peak pressure. Force-time integral was significantly greater in males than females under the 1st, 3rd, and 4th metatarsal heads. Maximum force was also significantly higher in males under the heel, 1st and 3rd metatarsal heads. Mean force was greater in males under the 3rd metatarsal head. CONCLUSION There were no peak pressure differences; however the contact area of the male foot was larger than that in females.

Do you get value for money when you buy an expensive pair of running shoes

Objective: This investigation aims to determine if more expensive running shoes provide better cushioning of plantar pressure and are more comfortable than low-cost alternatives from the same brand. Methods: Three pairs of running shoes were purchased from three different manufacturers at three different price ranges: low (£40–45), medium (£60–65) and high (£70–75). Plantar pressure was recorded with the Pedar® in-shoe pressure measurement system. Comfort was assessed with a 100 mm visual analogue scale. A follow-on study was conducted to ascertain if shoe cushioning and comfort were comparable to walking while running on a treadmill. Forty-three and 9 male subjects participated in the main and follow-on studies, respectively. The main outcome measure was the evaluation of plantar pressure and comfort. Results: Plantar pressure measurements were recorded from under the heel, across the forefoot and under the great toe. Differences in plantar pressure were recorded between models and between brands in relation to cost. Shoe performance was comparable between walking and running trials on a treadmill. No significant difference was observed between shoes and test occasions in terms of comfort. Conclusions: Low- and medium-cost running shoes in each of the three brands tested provided the same (if not better) cushioning of plantar pressure as high-cost running shoes. Cushioning was comparable when walking and running on a treadmill. Comfort is a subjective sensation based on individual preferences and was not related to either the distribution of plantar pressure or cost.

Shoes influence lower limb muscle activity and may predispose the wearer to lateral ankle ligament injury

Lateral ankle ligaments are injured by hyperinversion of the foot. Foot position is controlled by the lower limb muscles. Awareness of foot position is impaired by wearing shoes. We aimed to determine the influence of wearing shoes upon muscle activity. Sixty‐two healthy subjects underwent the same measurements, barefoot and with standardized shoes in a random order. Electromyography (EMG) was recorded from the peroneus longus muscle in response to sudden and unanticipated inversion of the ipsilateral foot. Following foot inversion, the EMG signal showed an initial peak muscle contraction followed by a sustained smaller contraction. Both changes were significantly greater in shoes compared to the barefoot condition for all tested degrees of inversion. Muscle contraction following sudden inversion of the foot was significantly greater when wearing shoes. This greater muscular contraction may be an intrinsic mechanism to oppose the increased moment created by the inverted foot/shoe condition, and hence, may counter balance the increased tendency to injure the lateral ankle ligaments created by wearing shoes.

Harmful cleats of football boots: A biomechanical evaluation

BACKGROUND Football players wear boots of varying cleat designs with some preferring the bladed cleats while others opting for the conventional studded cleats. The current study compares biomechanically the boots with differing cleat designs and their effect on feet, if any. METHODS Twenty-nine healthy male volunteers were recruited from amateur football teams. They were asked to perform three trials each of two activities: a straight run and a run cutting at a 60° angle wearing bladed and studded Adidas®-F series boots on artificial turf. Plantar pressure values were recorded using the Pedar®-X in-shoe pressure measuring device. Peak pressure and pressure-time integral were analysed over 11 clinically relevant areas under the foot. RESULTS While the in-shoe pressure and pressure-time integral were higher under the medial half of the foot with studded boots, they were higher under the lateral half of the foot with the bladed design. CONCLUSIONS The studded boots can be considered safer as the pressure distribution across the foot and the pattern of centre of pressure progression mimicked the normal motif, whereas the bladed boots could potentially be deemed relatively more harmful due to the unnatural increased loading under the lateral half of the foot, predisposing the foot to injuries.

Development of force measurement system for clinical use in minimal access surgery

BackgroundAnalysis of force in minimal access surgery (MAS) is important for instrument design, surgical simulators, and in the understanding of tissue trauma incurred during surgery. The aim of this study is to develop a force measuring system for use with different instruments in clinical practice.MethodsStrain gauges were connected to both arms of a standard -5 mm interchangeable forceps handle. A rotational sensor was used to indicate the relative position of the handle arms, and consequently the jaws’ position. A generic force-direction assembly was manufactured to determine the force direction at the port site. Interface electronics included signal conditioning and patient isolation circuits. Dedicated software was used for data acquisition, display, and analysis. To test their performance after sterilization, repeated force measures were obtained with the instruments after 10 cycles of autoclaving. Graduated weights were used to calibrate the strain gauges and a spring balance was employed to calibrate the force applied at the instrument tip. Calibration tests were also carried out to determine the effect of mounting the force direction assembly onto the access port.ResultsGripping, dissecting, pushing, and pulling forces, along with the vector sum of forces acting at the port site, were synchronously displayed with the operative video record. Repeated autoclaving caused no deterioration in force sensing or signal transmission. The accuracy of the strain gauge readings was ±0.05 V for the jaw force and ±0.1 V for the force at the access port. The additional force created by the force direction assembly force was 7% of the port force alone.ConclusionForce measurement system has been developed for clinical use. The system measures the gripping, dissecting, pulling and pushing forces as well as the force vector at port site. It also determines the position of instrument’s jaws.

A method to calculate the centre of the ankle joint: a comparison with the Vicon Plug-in-Gait model.

BACKGROUND In gait analysis, calculation of the ankle joint centre is a difficult task. The conventional way to calculate the ankle joint centre is using the Vicon Plug-in-Gait model. The present study proposes a new model, which calculates the joint centre from two markers positioned over the medial and lateral malleoli (i.e. Two-marker-model). METHODS In order to compare the proposed model with Plug-in-Gait model, gait data from healthy and patient subjects were captured using a motion capture system. The ankle joint centres were calculated by the two models. A test-retest experiment was carried out to check reliability and repeatability for Two-marker-model. FINDINGS Two ankle joint centres produced by two models were significantly different. The distances between two ankle joint centres were approximately 16.8 (mm), and the differences in the posterior-anterior, medial-lateral and inferior-superior directions were approximately 6.3, 7.7 and 8.2 (mm). Further error analysis highlighted that the probability of producing errors in Two-marker-model is lower than that in Plug-in-Gait model due to the Two-marker-models simple and reliable marker positioning. The reliability and repeatability coefficients for the new model were greater than 0.9. INTERPRETATION In principle, the Plug-in-Gait model is more likely to produce errors than the Two-marker-model, because the former employs multiple markers from the pelvis to calf to define the ankle joint centre with marker positions being very user-dependent. The results suggest that the Two-marker-model can be considered an alternative to Plug-in-Gait model for calculating ankle joint centre.

The effect of varying footwear configurations on the peroneus longus muscle function following inversion

BACKGROUND The ankle is one of the most commonly injured joints with inversion injury affecting its lateral ligament complex being the commonest of all. Shoes are one of the known risk factors for such an injury. OBJECTIVE This study seeks to examine the impact of varying shoe configurations on the protective function of the peroneus longus muscle during unanticipated foot inversion. METHODS The peak amplitude, latency and post-peak average amplitude of the ipsilateral peroneus longus muscle were recorded by surface electromyography following unanticipated inversion of the feet of 35 subjects in a two-footplate tilting platform from 0° to 20°. The test conditions were barefoot, standard training shoe, shoe with a sole flare, and an above the ankle laced boot. RESULTS Analysis revealed significant differences in peak muscle contraction between shod and unshod conditions. The standard shoe and the flared sole design showed greater statistically significant differences from the unshod condition, than the boot. The muscle was responding earlier in the shod conditions compared to the barefoot. The post-peak average amplitude with the standard shoe and the flared sole shoe were significantly different from the barefoot condition. CONCLUSION Albeit no marked differences could be demonstrated between the tested shoes, the inherent construct of the laced boot probably attempts to protect the ankle-subtalar joint complex evidenced by evoking a less strong peroneus longus muscles protective response.

Differences in foot pressures between Caucasians and Indians

BACKGROUND Indians are the largest single ethnic minority group in the United Kingdom and form more than one million of the current population. No studies have investigated foot pressure differences between Caucasians and Indians. OBJECTIVE The aim of our study was to investigate the in-shoe pressure differences in Caucasians and Indians using the Pedar(®)-m (Novel GmbH, Germany). METHODS The study included 12 Caucasians and 21 Indians. Peak pressure (PP), contact area (CA), contact time (CT), pressure-time integral (PTI), force-time integral (FTI), instant of peak pressure (IPP), maximum force (MaxF) and mean force (MeanF) were recorded. RESULTS Caucasians had higher significant PP compared to Indians under the heel (293 kPa vs. 251 kPa; P<0.001), 1st metatarsal head (294 kPa vs. 233 kPa; P=0.01), 2nd metatarsal head (266 kPa vs. 236 kPa; P=0.03), 3rd metatarsal head (254 kPa vs. 223 kPa; P=0.04), and the 5th metatarsal head (168 kPa vs. 133 kPa; P=0.04). There was no significant difference in the contact area between the two race groups. The PTI was statistically significantly higher in Caucasians in the region of the 1st metatarsal head (79 kPas vs. 62 kPas; P=0.03) and 5th metatarsal head (58 kPas vs. 44 kPas; P=0.03). There were no significant differences among CT, FTI, IPP, MaxF and MeanF among them. CONCLUSION The PP under the heel, 1st, 2nd, 3rd and 5th metatarsal heads and the PTI under the 1st and 5th metatarsal heads in Caucasians is higher than in Indians. There is no difference in the CA.

The influence of shoe sole's varying thickness on lower limb muscle activity

BACKGROUND The lateral ligament injury of the ankle is acknowledged to be the most common ankle injury sustained in sport. Increased peroneus longus muscle contraction in the shod population has already been documented. This study aimed to quantify the effect of shoe soles varying thickness on peroneus longus muscle activity. METHODS Electromyographic recordings of the peroneus longus muscle activity following unanticipated inversion of the foot from 0° to 20° in a two-footplate tilting platform were collected from 38 healthy participants. The four test conditions were: barefoot, standard shoe, and shoes with 2.5 cm and 5 cm sole adaptation respectively. RESULTS Compared to the barefoot condition, there is an increase in the magnitude of muscle contraction on wearing shoes, which further increases with thickening shoe soles. The peroneus longus was responding earlier in the shod conditions when compared to the barefoot, although the results were variable within the three shod conditions. CONCLUSION Footwear with increasing shoe sole thickness evokes a correspondingly stronger protective eversion response from the peroneus longus to counter the increasing moment at the ankle-subtalar joint complex following sudden foot inversion. Hence, fashion footwear with thicker sole is likely to increase the risk of lateral ligament injury of the ankle when such protective response is overwhelmed. Similarly, the clinicians need to be cautious regarding the amount of shoe raise that they could provide for patients with limb length discrepancy without any detrimental untoward side effects.