Anthropometric foot measurements are imperative in the determination of obesity in children and adolescents. The measurements are categorized into direct and indirect. Direct measurements are calculated from the footprints while indirect are from radiographic and ultrasound images.
To begin with, the calculation of Footprint angle (FA), Chippaux-Smirak index (CSI), and Martirosov’s K Index (KI) is from the footprint. According to Razeghi et al (2002), a pedograph paper is placed under a membrane and the foot positioned above the membrane. The foot is then lowed into the membrane and the child is instructed to stand straight so that the weight disperses evenly. The foot is then cautiously removed after two seconds and the footprint obtained is used for the calculation. To get FA a line is drawn from the middle of the heel to the middle of the forefoot and another from the middle of the heel to the top of concavity of the medial arch and the resulting angle is FA (Forriol et al., 1990). These angles are then grouped into flat (0-300), lower (31-350), intermediary (36-420), and normal (430 +) arches.
On the other hand, to get CSI a line is drawn from the middle of the heel to the widest area of the forefoot and another line parallel to it is used to determine the narrow area of the medial arch and after the identification of that area, the two lines are divided and the findings expressed in percentage (Welton, 1992). High arch is 0%, low is 0-30%, normal is 0-30%, intermediary is 31-40% and low is 41-45% and morphological flat is more than 46%. Volpon (1993) states that the FA of the foot of obese children and adolescents is considerably less in comparison to non-obese while the CSI values of obese are greater than nonobese. A lower FA and a higher CSI are due to a low internal arch when measured longitudinally, a flat cavity, and a wider area of the middle foot. This is because the excessive weight that accompanies obesity exerts too much pressure on the foot hence flattening the middle foot and this is evidenced by a large area of the foot that is in contact with the ground.
Additionally, to calculate KI, a line is drawn from the middle of the metatarsal area to the lateral of the same area while another one is from this lateral area to the lateral of the heel (Riddiford-Harland, 2010). Another line is from the center of the heel to toes tip. The intersection of these lines is determined and measured. The resulting arch structure is classified as high, normal, or flat. According to Wong (1996), a flat arch is prominent in obese children and adolescents. This is because their weight exerts too much pressure on the feet resulting in flat feet.
Talus-first metatarsal angle (TFMA) and Calcaneal inclination angle (CIA) are calculated from the radiograph images of the lateral foot while the children have some weight (Vasilije et al., 2006). The children stand with extended knees while heels and toes are at an equal level. Equal weights are placed on both feet while the x-ray film is positioned between the feet. The x-ray beam is then targeted at the metatarsal. Rome et al (2010) explain that TFMA measures the way the forefoot is aligned about the hindfoot. In this assessment, an angle formed by the connection of the talar and the longitudinal axes of the first metatarsal is measured. This angle needs to be 00, (1-50) is a flat foot; (10-300) is moderate and 310 and above is severe. The flat foot is prominent in obese children and adolescents.
On the contrary, CIA results from drawing a line from the plantar surface of calcaneus to the lower border of where the distal surface articulates. Another line is from the same calcareous surface to the metatarsal head that is in the fifth position (Riddiford-Harland, 2010). In case the resulting angle is lower than 200 then flat feet that are common in obese children are present. In both TFMA and CIA the presence of flat feet in obese children and adolescent is due to the difference in the osseous structure of the medial longitudinal arch.
In recent research, Razeghi et al (2002) explain that Midfoot Plantar Fat Pad Thickness is quantified through ultrasound. The child’s foot is subjected to ultrasound and the mid foot fat is determined. The result is that obese children and adolescents have thicker fat pads than non-obese. Despite the correlation between plantar pressure and midfoot fat thickness, the vigor and the association are low. Therefore, the thickness is due to surplus body mass and not as a result of adaptation to the pressure that accompanies excess weight. This is because the excess adipose tissue in overweight children and adolescents is deposited in the whole body including the feet.
Finally, the Relaxed Calcaneal Stance Position (RCSP) shows the calcaneus position in the frontal plane following pronation (Parrot, 2010). Calcaneus is varus if inverted to transverse plane and valgus if everted. Onodera et al (2008) stated that the RCSP is the angle resulting from the calcaneus posterior aspect to the supporting surface in the stance position. The child stands in a relaxed position and the movable arm is sided on the line bisecting the calcaneal while the static arm is parallel to the supporting surface and the resulting angle is RCSP angle. A varus calcaneus is common in obese children and adolescents (Parrot, 2010). This is because the excess weight together with the thick mid-foot planter fat pad increases the foot pronation.
In conclusion, a direct measurement that involves the footprints includes CSI and Martirosov’s K Index. Moreover, RCSP is an indirect measurement obtained while the children are standing. Conversely, indirect measurements include Talus-first metatarsal angle and Calcaneal inclination angle that result from radiographic images as well as Midfoot Plantar Fat Pad Thickness that is obtained from ultrasound images.
References
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Onodera., et al., 2008, What is the Best Method for Child Longitudinal Plantar Arch Assessment and When does Arch Marturation Occur. Science Direct , 18 (2), 142 149.
Parrot, A. 2010, Normative Reference Values for Musculoskeletal Positions and Functional Motor Abilities in the Pediatric Poppulation: Literature Review. Institut De Readaptation En Deficience Physique De Quebec , 27 (9), 298-307.
Razeghi, M., & Batt, E. 2002, Foot Type Classification: A Critical Review of Current Methods. Gait and Posture , 15 (5), 282-291.
Riddiford-Harland, D. 2010, Childhood Foot Structure and Function: Is this Influenced by Obesity? University of Wollong , 8 (2), 13-70.
Rome, K., & Evans, A. 2010, Non-Surgical Interventions for Paediatric Pes Plantus. Cohrane Database of Systematic Reviews , 2 (7), 8-14.
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Welton, A. 1992, The Harris and Beath Footprint: Interpretation and Clinical Value. Foot Ankle , 13 (8), 462- 468.
Wong, F. 1996, Footprint Analysis During the Growth Period. Info-Med Orthopedics , 3 (20), 28-45.