Support for Using HeelRite™ Heel Seats for Infants with Overpronation: Part 1
Author: Billi (Beverly) Cusick, PT, MS, COF, NDT
The pediatric rehabilitation community is gaining support from researchers for investing in early intervention that is designed to optimize early sensorimotor development for children who show deficits. [1] The developing foot – our life-long body-ground interface – is an important component of early intervention. D’Amico (2021) [2] offers a thorough and thoughtful discussion that blends his vast clinical experience with evidence-based support for early intervention for flexible pronation in his open access article in Podiatry Today: Pediatric Overpronation: Treat Or Monitor?
FOOT FEATURES AND DEVELOPMENTAL FACTORS
Whereby much information is published pertaining to typical changes in the developing foot anatomy and load distribution, the biomechanical and kinesiologic elements and methods that foster those changes are largely unknown. All aspects of this discussion regarding those methods represent my science-based – and working - hypotheses.
In my nearly 50 years as a pediatric PT and student of developmental orthopedics, I have learned the significance of three major factors that appear to me to contribute to early foot development:
- The presence of the apparently innate drive to achieve and maintain the upright position while awake
- The organized achievement of neck and trunk muscle strength and control against gravity, beginning with antigravity extension, and
- The demands on the foot joints and muscles to support the verticality drive.
The feet are among the most nerve-rich of our body parts. Sensory load receptors inform
the essential drive to gain and retain upright postures and to preserve the integrity of the
plantar skin, and so, our health
While a part of foot development is driven by genetic influences, as in, “She has her
father’s feet”, another part is a product of the properties and positioning of the load-bearing structures and the context of routine loading on them that occurs in daily life.
Infants ideally show a degree of foot pronation that reflects the immaturity of their foot
ligaments and muscles and of control of this segment
The building of fully functioning feet usually occurs over about 6 years of typical
sensorimotor development. During this time, the foot muscles and ligaments gradually gain both passive and active strength. Foot joint functions serving balance and locomotion are refined with massed practice in optimum, age-appropriate, whole body and lower limb alignment.
The foot has three segments from back to front – the hind foot, midfoot, and forefoot and two long segments– the inner (medial)and outer (lateral) pillars. Using the language of Lois Bly, the lateral pillar is the foot’s “point of stability”– the segment that provides a base for the medial pillar to operate and develop as the “point of mobility”.[3]
With the life long operation of upright maintenance underway, early foot development – both typical and pathological - is a product of routine bodyweight loading on the foot segments and pillars. Optimum foot segment loading is neither intentional nor innate, but rather, is a feature of existing body and limb alignment, trunk control, the properties of the soft tissues, gravity, and ever-increasing movement in upright position. 2 About four months after full-term gestation, the typical lower limb alignment at birth - with knees far apart and feet close together– renders loading the lateral pillars inevitable.
About four months after full-term gestation, the typical lower limb alignment at birth - with knees far apart and feet close together – renders loading the lateral pillars inevitable
The new walker’s wide base of support is a transient stabilizing necessity with knees aligned more lateral to the feet much of the time. Lateral pillar loading remains a component of foot development that occurs primarily during walking.[4] With the medial pillar relatively off-loaded, the 1st ray can strive for upright stability by plantarflexing, forming the loaded tripod – heel, 1st and 5th metatarsal heads - and the medial longitudinal arch.
As the immature, hypermobile foot gains competency in enduring weight loading, the infant gains intentional and variable foot movements. The weight-loaded feet are rarely still. The ideal foot shape progresses from triangular to almost rectangular with the medial and lateral borders straight and the toes aligned parallel with the metatarsal shafts. The toes flex frequently in a balancing response to the bodyweight coming forward. The toes relax when the bodyweight moves back over the hindfeet.
The key to optimum foot development is the presence of weight loading on the lateral pillars combined with the challenges to move and to stay upright in the process.I’ll discuss pediatric overpronation in Parts 2 & 3 of this series.
Download Part 1 here.
[1] King AR, Machipisa C, Finlayson F, Fahey MC, Novak I, Malhotra A. 2021. Early detection of cerebral palsy in high-risk infants: Translation of evidence into practice in an Australian hospital. J Paediatrics Child Health. 57(2):246-50.
[2]D’Amico JC, Harris EJ. 2021. Pediatric Overpronation: Treat or Monitor? Podiatry Today. 34(12).
[3] Bly L. 2011. Components of Typical and Atypical Motor Development. Laguna Beach, CA; Neurodevelopmental Treatment Association; www.ndta.org
[4] Bosch K, Gerss J, Rosenbaum D. 2007. Preliminary normative values for foot loading parameters of the developing child. Gait & Posture. 26(2):238-47.