Angela Höhne

Reduced plantar cutaneous sensation modifies gait dynamics, lower-limb kinematics and muscle activity during walking.

Peripheral neuropathy is the most common long-term complication in diabetes and is involved in changes in diabetic gait and posture. The regression of nerve function leads to various deficits in the sensory and motor systems, impairing afferent and efferent pathways in the lower extremities. This study aimed to examine how reduced plantar-afferent feedback impacts the gait pattern. Cutaneous sensation in the soles of both feet was experimentally reduced by means of intradermal injections of an anaesthetic solution, without affecting foot proprioception or muscles. Ten subjects performed level walking at a controlled velocity before and after plantar anaesthesia. Muscle activity of five leg-muscles, co-contraction ratios for the knee and ankle joint, ground reaction forces (GRF), spatiotemporal characteristics, joint angles and moments of the hip, knee and ankle were analysed. The intervention significantly lowered plantar sensation, reducing it to the level of sensory neuropathy. Spatiotemporal gait characteristics remained unchanged. The ankle joint was more dorsiflexed which coincided with increased tibialis anterior and decreased gastrocnemius medialis muscle activity during foot flat to mid-stance. In addition, the knee joint was more flexed accompanied by increased biceps femoris activity and higher internal knee-extension moment. With regard to gait dynamics, a delay of the first peak of the vertical GRF was observed. Increased soleus and tibialis anterior muscle activity were found during the end of stance. Short-term loss of plantar sensation affects lower-limb kinematics and gait dynamics, particularly during the first half of stance, and contributes to modified muscle-activation patterns during locomotion.

Effects of reduced plantar cutaneous afferent feedback on locomotor adjustments in dynamic stability during perturbed walking

This study examined the effects of reduced plantar cutaneous afferent feedback on predictive and feedback adaptive locomotor adjustments in dynamic stability during perturbed walking. Twenty-two matched participants divided between an experimental-group and a control-group performed a gait protocol, which included surface alterations to one covered exchangeable gangway-element (hard/soft). In the experimental-group, cutaneous sensation in both foot soles was reduced to the level of sensory peripheral neuropathy by means of intradermal injections of an anaesthetic solution, without affecting foot proprioception or muscles. The gait protocol consisted of baseline trials on a uniformly hard surface and an adaptation phase consisting of nineteen trials incorporating a soft gangway-element, interspersed with three trials using the hard surface-element (2nd, 8th and 19th). Dynamic stability was assessed by quantifying the margin of stability (MS), which was calculated as the difference between the base of support (BS) and the extrapolated centre of mass (CM). The horizontal velocity of the CM and its vertical projection in the anterior-posterior direction and the eigenfrequency of an inverted pendulum determine the extrapolated-CM. Both groups increased the BS at the recovery step in response to the first unexpected perturbation. These feedback corrections were used more extensively in the experimental-group, which led to a higher MS compared to the control-group, i.e. a more stable body-position. In the adaptation phase the MS returned to baseline similarly in both groups. In the trial on the hard surface directly after the first perturbation, both groups increased the MS at touchdown of the disturbed leg compared to baseline trials, indicating rapid predictive adjustments irrespective of plantar cutaneous input. Our findings demonstrate that the locomotor adaptational potential does not decrease due to the loss of plantar sensation.

Plantar pressure distribution in gait is not affected by targeted reduced plantar cutaneous sensation

BACKGROUND Plantar ulcers are a common and severe complication of the diabetic neuropathic foot. Increased plantar pressures while walking are associated to incidence of plantar ulcer formation in diabetes. There is a strong correlation between the increase in plantar pressures and the severity of peripheral neuropathy. One consequence of peripheral sensory neuropathy is insensitive skin. The influence of reduced plantar sensitivity on changes in plantar pressure distribution is not well understood. The purpose of this study was to identify possible causal dependences between reduced plantar cutaneous sensation and plantar pressure distribution during gait. METHODS Dynamic pressure distribution in gait and sensory perception threshold for pressure touch and vibration (25Hz/200Hz) of the plantar foot were determined pre and post sensory intervention in ten healthy subjects. Cutaneous sensation in both foot soles was experimentally reduced by means of intradermal injections of an anaesthetic solution. This procedure leaves foot and ankle proprioception as well as intrinsic foot muscles unaffected. FINDINGS The intervention significantly reduced plantar cutaneous sensation to the level of sensory neuropathy. Plantar pressure and force variables, contact times for the entire foot and for the plantar foot regions were not influenced significantly. INTERPRETATION Experimentally reducing plantar cutaneous sensation causes no changes in plantar pressure distribution while walking. Our findings suggest that in the diabetic neuropathic foot insensitive plantar skin due to peripheral sensory neuropathy may be not a decisive factor for altering plantar pressures. This is underpinning the importance of concomitant affection of different systems secondary to diabetic peripheral neuropathy.

Effect of rocker shoe design features on forefoot plantar pressures in people with and without diabetes

BACKGROUND There is no consensus on the precise rocker shoe outsole design that will optimally reduce plantar pressure in people with diabetes. This study aimed to understand how peak plantar pressure is influenced by systematically varying three design features which characterise a curved rocker shoe: apex angle, apex position and rocker angle. METHODS A total of 12 different rocker shoe designs, spanning a range of each of the three design features, were tested in 24 people with diabetes and 24 healthy participants. Each subject also wore a flexible control shoe. Peak plantar pressure, in four anatomical regions, was recorded for each of the 13 shoes during walking at a controlled speed. FINDINGS There were a number of significant main effects for each of the three design features, however, the precise effect of each feature varied between the different regions. The results demonstrated maximum pressure reduction in the 2nd-4th metatarsal regions (39%) but that lower rocker angles (<20°) and anterior apex positions (>60% shoe length) should be avoided for this region. The effect of apex angle was most pronounced in the 1st metatarsophalangeal region with a clear decrease in pressure as the apex angle was increased to 100°. INTERPRETATION We suggest that an outsole design with a 95° apex angle, apex position at 60% of shoe length and 20° rocker angle may achieve an optimal balance for offloading different regions of the forefoot. However, future studies incorporating additional design feature combinations, on high risk patients, are required to make definitive recommendations.

Is it possible to predict optimal rocker shoe design using barefoot gait parameters

Curved rocker shoes are routinely prescribed for people with diabetes in order reduce in-shoe plantar pressures. However, previous research has shown that different individuals may require different rocker outsole geometries in order to optimise pressure reduction [1, 2]. This has led some researchers to suggest that every individual should try a range of possible outsole designs to identify the design which maximises pressure reduction [1]. However, this process may not be feasible in a clinical setting. Given that plantar pressure has been shown to depend on specific gait variables [3], it may be possible to develop an algorithm which could predict an individual’s pressure response to a specific rocker outsole design using an input of gait data. Such an algorithm would remove the need to try on a large number of pairs of rocker shoes.

What is the best Rocker Shoe design

Background Rocker shoes are often prescribed to reduce in-shoe pressures in order to minimise the risk of ulceration in diabetic patients. However, the efficacy of the 3 principal design features of a rocker shoe (apex position, rocker angle and apex angle, see Figure 1) is unknown. Only one known study to date has systematically varied 2 of the 3 design features [1]. Therefore the aim of this study was to investigate the effect of the three principal design features, quantify inter subject variability and establish whether there is any difference in the response of the diabetic and the healthy cohort by recording in shoe plantar pressure.

Evaluating the effect of apex position and rocker in curved rocker shoes

Curved rocker shoes are designed with a contoured outsole which can be characteristics by three principle design features: rocker angle, apex angle and apex position. Although these shoes are routinely prescribed to reduce in-shoe pressure in patients with diabetes, there is only minimal scientific evidence to inform the choice of value for each of the three design features. Results from a previous study [1], suggested that a 95° apex angle may be the best compromise for offloading the different regions of the forefoot. The results of this study also suggested that higher rocker angle may lead to decrease pressure, however, this study did not quantify the precise effect of rocker angle and apex position in shoes with a 95° apex angle.

Enhanced foot muscle strength and plantar pressure in the neuropathic diabetic foot

dition. This time is longer than that found in other studies, e.g. 5 minutes in Hardin et al. (2004). This could be explained by the fact that minimalist shoes induced an important change, compared to classical running shoes, requiring more time for runners to adapt. It could be that barefoot running required at least as much time as minimal shoes for the subjects to adapt. Results also showed that foot strike pattern was not systematically maintained up to the end of the test. This may be due to fatigue, to energy expenditure regulation or to limitation of loads applied to the musculoskeletal system. These findings suggest care should be taken when interpreting results from other studies based on a first instant running with minimalist shoes. These results also suggested performing measurements after eight minutes adaptation barefoot or with minimal footwear. Future studies should use the same warm-up time when assessing the effect of barefoot and minimal footwear.