shank stiffener

shank stiffener

firm splinting material (e.g. stiff leather, glass fibre) lying between the heel seat and forefoot tread of a shoe during construction, to prevent buckling of the waist, often used in conjunction with a Thomas heel (see Table 1)
Table 1: Footwear and last terminology
Footwear/last elementComment
TreadlineThat part of the forepart of a shoe that is in direct contact with the ground surface when the heel height, pitch and toe spring are correct; i.e. the area that runs obliquely across the foresole, which in a well-fitting shoe corresponds to the MTPJs and thus is subject to the greatest wear. Where the treadline of the shoe and MTPJ parabola of the foot do not coincide, the foot will be subject to shoe trauma: if the MTPJ parabola lies distal to the treadline the lesser toes will be compressed
Toe springThe elevation of the toe end of the last from the horizontal surface when the seat is raised to its correct height (pitch) so that the last stands correctly on its treadline or the elevation of the toe end of the shoe from the horizontal when the sole and heel rests on a horizontal surface
The toe spring reduces the resistance to flexion that the shoe places on the foot when the foot is flexed at the MTPJs, and thus reduces both fatigue during walking and wear at the vamp area of the upper
The more rigid the outsole, the greater the effort required to allow flexion of the foot at the MTPJs; thus the more rigid the outsole, the greater the height of the toe spring. (Consider the height of the toe spring of a clog, which, although totally inflexible, allows the foot to 'rock' forward in response to the forward motion of the body's centre of gravity)
The toe spring of 'slip-on' shoes is shallow, and designed to flatten during gait, so that the quarters close into the rearfoot and the shoe does not fall off
The toe spring of a high-heeled shoe is shallow as this style of shoe automatically places the toes in a dorsiflexed position, and the degree of toe spring is only required to prevent the toe end of the sole scuffing against the ground during gait
Heel pitchThe angle of elevation of the heel seat of the last from the horizontal surface when the last is standing correctly on its treadline; the heel pitch varies directly with the height of heel of the shoe, and the toe spring will be increased if too shallow a heel is used, or decreased if too high a heel is added to the shoe
A significant increase in heel height throws the body weight forward, with the need to make a resultant compensatory alteration in back posture (an increase in the lumbar curvature, and decrease in the thoracic curvature, so that the bottom and chest are exaggerated) with constant plantarflexion of the ankle and inversion of the subtalar joint reducing normal shock absorption
FlareThe relative positions in the centre of the heel seat and the sole. Flare is determined by projecting the line that bisects the centre of the heel seat distally through the treadline of the sole of the shoe
• An in-flare shows a greater sole area medial to the line of bisection
• An out-flare shows a greater sole area lateral to the line of bisection
• straight-flare shows equal amounts of sole on either side of the line of bisection
The plantar aspect of the foot should be examined in a similar manner. The foot bisection passes:
• Through the middle of the third toe in a straight-flare foot
• Between the second and third toes in an out-flare (e.g. pes valgus) foot
• Between the third and fourth toes in an in-flare (e.g. pes cavus) foot
Misfit of foot and shoe flare will cause shoe-related foot trauma
SizingHeel to ball length:
The distance between the posterior aspect of the heel and the midpoint of the medial aspect of the first MTPJ (ideally equivalent to 0.7 of the heel to toe length)
Heel to toe length:
The distance from the heel to the toe
Both lengths should be measured to ensure that the widest part of the foot co-incides with the widest part of the shoe
Girth/width measurement (A-E fittings)
There are a number of shoe-sizing conventions (see Table 2)
StylesOxford/brogue: a conventional laced shoe with a decorative toe cap, close-fitting quarters and facings, a stitched tongue, five pairs of eyelets; unsuitable for oedematous or highly arched feet
Derby/Gibson: a conventional laced shoe with a wide throat and integral tongue, three pairs of eyelets; more suitable for oedematous and highly arched feet
Moccasin/loafer: a slip-on style with an apron front on to which the vamp is stitched; the seam does not stretch, and thus can traumatize prominent toe joints
Sandal: a shoe with a cut-away upper
Court shoe/pump: close-fitting, thin-soled, slip-on shoes, often made for women, with a high-heeled style
Sports shoes/trainers: shoes that are designed to incorporate features that protect the foot from the trauma incurred by heavy exercise
Monk shoe: an Oxford or Derby-style shoe, where the medial quarter is extended to overlap the lateral quarter, with a side buckle or Velcro fixing
Boots: footwear that extend proximally to just below the malleoli, to cover the malleoli, or as far as the knee

MTPJ, metatarsophalangeal joint.

Table 2: Comparison of UK, US and continental adult shoe sizes
• UK: There is a 8.5-mm difference in the length of the shoe between each full shoe size, and a half-size difference adds 4.25 mm to the length; children's shoes are sized from 0 (102mm long) to 13; adult shoes are sized from 1 (8.5mm longer than a child's size 13) to 13
• USA: There is a 8.5-mm difference in the length of the shoe between each full shoe size, and a half-size difference adds 4.25 mm to the length; shoe sizes are based on a child's size 0 of 100 mm long (that is, 1/12-inch shorter than the UK size 0; women's shoes are marked up 1.5 sizes greater than the UK length equivalent, and men's by 1 size greater than the UK equivalent)
• Continental: The length difference between each full size is 6.6 mm, known as the Paris point, with 3 Paris points in each 2 cm of shoe length
UK (men and women)USA (women)USA (men)Continental (men and women)
56.5638
67.5739
78.5841
89.5942
910.51043