Optimization of rocker sole footwear
optimize designs for groups of patients or individual
patients. Furthermore, the degree of offloading in
each anatomical area is strongly influenced by the
precise geometry of the rocker outsole [15, 16] . For
example, our earlier work showed that altering the
rocker sole apex angle by only 10–20°, can have a
critical effect on the degree of offloading under the
1st metatarsophalangeal (MTP) joint [16] .
A further issue is that several previous studies
investigating pressure reducing footwear intended
for people with diabetes have in fact involved
only healthy individuals [15, 17, 18] . There are known
differences between the gait and feet of those with
and without diabetes [19] and the transferability of
results has not been tested. Therefore, three issues
need to be addressed. Firstly, we need to better
understand the systematic effect of changing different
rocker shoe design features on plantar pressure. With
this we could propose group-optimized designs which
would be used in prefabricated footwear aimed at
reducing pressure beneath the 200 kPa threshold.
Secondly, we need to understand the extent to which
this group-optimized footwear meets the <200 kPa
target compared to personalized footwear designs.
Thirdly, since previous research has often assumed
results from healthy participants can be transferred
to those with diabetes, we need to compare footwear
effects in healthy and diabetes populations.
Methods
of type 1 or type 2 diabetes at least 6 month prior
to enrolment on the study. Exclusion criteria were
any current/history of foot ulceration or any foot
deformity/ medical foot condition that prevented the
wearing of off-the-shelf therapeutic footwear. Healthy
participants were recruited via community advert and
required to have no medical diagnosis of diabetes or
current musculoskeletal pain. All subjects provided
written consent to participate in the study after
appropriate ethical approval had been obtained (UK
NRES 10/H1013/32). Sensation loss in the participants
with diabetes was assessed using a 10 g monofilament
at 5 locations (hallux, 1st MTP, 5th Metatarsal head
(MTH), 5th toe and styloid process) [20] .
Footwear and plantar pressure
measurement
We sought to optimize the curved rocker outsole
profile [13] . Although personalized therapeutic
footwear has a wide range of different features that
can be modified, this study focused on the outsole
geometry of the rocker profile. This geometry can be
described by three independent design features: apex
angle, apex position and rocker angle [16] (Fig. 1). Apex
angle and position define the orientation (relative
to the long axis of the shoe) and position (% of shoe
length) of a theoretical mediolateral line where the
outsole begins to curve upwards under the forefoot.
Our previous study demonstrated that an apex angle
of 95° was appropriate for footwear designed to offload
high risk regions of the forefoot [16] and was used for
all footwear.
Participants
Subjects with diabetes were recruited at two sites:
the University of Salford (UK) and the German
Sport University. At both sites’ participants were
identified through primary care clinics and through
advertisement in the community. Inclusion criteria
were age ≥ 18 and medically confirmed diagnosis
Previous research has shown that varying apex
position can have a pronounced effect on peak plantar
pressure [15, 16] . Furthermore, modifying apex position
for each individual patient is one customization
option available when aiming to reduce plantar
pressure [12] . We therefore studied apex positions of
52, 57, 62 and 67% of shoe length. The precise choice
Current Pedorthics | July/August 2019
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