Etiology of Foot Hyperpronation: Embryological Perspective

The link between joint pain and poor posture is not a new concept. However, this author links the development of poor posture to a specific embryological foot structure, which is biomechanically dysfunctional [hyperpronates]. An innovative foot orthosis is introduced which significantly reduces foot hyperpronation associated with this foot type. The result is visually improved posture and less joint pain.

The Physician and Sportsmedicine, 2004

In Brief: Primary care physicians often see patients who have foot pain. Although foot disorders may have many diagnostic possibilities, the majority can be explained via the pathologic biomechanics of hyperpronation and the resulting changes in the kinetic chain. Four common problems often associated with hyperpronation are plantar fasciitis, posterior tibial tendon dysfunction, metatarsalgia, and hallux valgus. Interventions that seek to reduce hyperpronation and strengthen foot muscles are often recommended for treating foot pain.

The Foot, 1998

When studying biological form and function, it is revealing to examine structure from an evolutionary perspective. The ape foot and that of modern humans differ in many areas, two of which are the absence of a divergent first ray and the reduced range of motion at the midtarsal joint. Two principle modifications are required to reduce the range of motion at the human midtarsal joint, one in each of the talo-navicular and calcaneo-cuboid articulations. A suite of data was obtained from the hindtarsus of humans, chimpanzees, gorillas, orangutans and the OH8 fossil foot. Multivariate analyses revealed the functional affinities of the fossil to be mixed, the medial column being ape-like while the lateral column was found to be human-like. Phylogenetic implications are that the lateral part of the foot became adapted for terrestrial bipedalism first with the medial column being subsequent. It is suggested that pathology resulting from disturbances of normal ontogeny should reflect this trend with mild disturbance affecting the medial column alone and severe disturbance affecting both medial and lateral columns.

Morton (1935) describes a foot in which the 1st metatarsal is shorter than the 2nd, visually identified as a deep 1st web space . Clinical studies uncover a foot in which the 1st metatarsal is structurally inverted and elevated relative to the 2nd metatarsal, referred to as the Rothbart Foot Structure (RFS) (Rothbart 1988). Morphologically, Morton and Rothbart both foot structures are the same: both arising from an embryological retention of talar supinatus. Rothbart (1988) demonstrates that it is this elevated position of the 1st metatarsal that hyperpronates the walking foot. Hyperpronation draws the posture forward. Strain and deformation patterns develop that lead the patient into chronic pain.

Journal of Manipulative and Physiological Therapeutics, 2002

Objective: To challenge casual understanding of the causal mechanisms of foot orthotics. Although the classic orthotic paradigm of Merton L. Root and his colleagues is often acknowledged, the research attempting to explain and validate these mechanisms is far less clear in its appraisal. Data Sources: Studies evaluating the relationship of foot type (medial arch height) and use of foot orthoses to the motions of the foot and ankle were compared and contrasted. A search was conducted to evaluate other possible mechanisms of orthotic intervention. Results: Although Root's methods of foot evaluation (subtalar neutral position) and casting (nonweight-bearing) are well referenced, these methods have poor reliability, unproven validity, and are, in fact, seldom strictly followed. We challenge 2 widely held concepts: that excessive foot eversion leads to excessive pronation and that orthotics provide beneficial effects by controlling rearfoot inversion/eversion. Numerous studies show that patterns of rearfoot inversion/eversion cannot be characterized either by foot type or by orthotics use. Rather, subtle control of internal/external tibial rotation appears to be the most significant factor in maintaining proper supination/pronation mechanics. Recent evidence also suggests that proprioceptive influences play a large, and perhaps largely unexplored, role. Conclusions: Considerable evidence supports the exploration of new theories and paradigms of orthotics use. Investigations of flexible orthotic designs, proprioceptive influences, and the 3-dimensional effects of subtalar joint motion on the entire kinetic chain are areas of research that show great promise. (J Manipulative Physiol Ther 2002;25:125-34)

Proceedings of the Royal Society B

Fossil evidence for longitudinal arches in the foot is frequently used to con- strain the origins of terrestrial bipedality in human ancestors. This approach rests on the prevailing concept that human feet are unique in functioning with a relatively stiff lateral mid-foot, lacking the significant flexion and high plantar pressures present in non-human apes. This paradigm has stood for more than 70 years but has yet to be tested objectively with quan- titative data. Herein, we show that plantar pressure records with elevated lateral mid-foot pressures occur frequently in healthy, habitually shod humans, with magnitudes in some individuals approaching absolute maxima across the foot. Furthermore, the same astonishing pressure range is present in bonobos and the orangutan (the most arboreal great ape), yield- ing overlap with human pressures. Thus, while the mean tendency of habitual mechanics of the mid-foot in healthy humans is indeed consistent with the traditional concept of the lateral mid-foot as a relatively rigid or stabilized structure, it is clear that lateral arch stabilization in humans is not obligate and is often transient. These findings suggest a level of detach- ment between foot stiffness during gait and osteological structure, hence fossilized bone morphology by itself may only provide a crude indication of mid-foot function in extinct hominins. Evidence for thick plantar tissues in Ardipithecus ramidus suggests that a human-like combination of active and passive modulation of foot compliance by soft tissues extends back into an arboreal context, supporting an arboreal origin of hominin bipedalism in compressive orthogrady. We propose that the musculoskeletal conformation of the modern human mid-foot evolved under selection for a functionally tuneable, rather than obligatory stiff structure.

Gait & Posture, 2014

An abnormal foot structure is described in which the 1st metatarsal is structurally elevated and inverted relative to the 2nd metatarsal. This foot structure is termed Primus Metatarsus Supinatus (aka Rothbarts Foot). Embryological studies suggest that this foot structure is the end result of a failed or incomplete unwinding of the talar head. Clinically, the 1st metatarsal and hallux are off the ground when the standing foot is placed into its anatomical neutral position. This foot structure is biomechanically dysfunctional, demarcated by its prolonged mid-stance hyperpronation. Global postural distortions are linked to this foot structure, including: (1) anterior rotation of the innominates (2) unleveling of the pelvis (3) augmenting of the scoliotic and kyphotic spinal curves (4) shoulder protraction (5) forward head position (6) malocclusion This postural shift is termed Bio-Implosion.

Journal of Foot and Ankle Research, 2012

Proceedings of the National Academy of Sciences, 2019

The primate foot functions as a grasping organ. As such, its bones, soft tissues, and joints evolved to maximize power and stability in a variety of grasping configurations. Humans are the obvious exception to this primate pattern, with feet that evolved to support the unique biomechanical demands of bipedal locomotion. Of key functional importance to bipedalism is the morphology of the joints at the forefoot, known as the metatarsophalangeal joints (MTPJs), but a comprehensive analysis of hominin MTPJ morphology is currently lacking. Here we present the results of a multivariate shape and Bayesian phylogenetic comparative analyses of metatarsals (MTs) from a broad selection of anthropoid primates (including fossil apes and stem catarrhines) and most of the early hominin pedal fossil record, including the oldest hominin for which good pedal remains exist, Ardipithecus ramidus. Results corroborate the importance of specific bony morphologies such as dorsal MT head expansion and "doming" to the evolution of terrestrial bipedalism in hominins. Further, our evolutionary models reveal that the MT1 of Ar. ramidus shifts away from the reconstructed optimum of our last common ancestor with apes, but not necessarily in the direction of modern humans. However, the lateral rays of Ar. ramidus are transformed in a more human-like direction , suggesting that they were the digits first recruited by hominins into the primary role of terrestrial propulsion. This pattern of evolutionary change is seen consistently throughout the evolution of the foot, highlighting the mosaic nature of pedal evolution and the emergence of a derived, modern hallux relatively late in human evolution. bipedalism | hominin evolution | metatarsals | Ardipithecus | functional morphology T he obligate terrestrial bipedalism of modern humans is unique among extant primates, and its ancient adoption by early hominins impacted subsequent evolutionary changes in social behavior and the development of material culture. A suite of morphological changes in the feet of early hominins is associated with the evolution of habitual bipedal locomotion in the human career and ultimately led to the energetically efficient gait used by modern humans (1-5). The forefoot skeleton includes the metatarsals (MT) and phalanges, and its functional anatomy is strongly tied to the evolution of bipedalism in hominins (5-9). Thus, hominin fore-foot fossils can offer key insights into when and how bipedalism evolved in the human lineage. During bipedal walking, modern humans dorsiflex (i.e., hyperextend) their forefoot joints, specifically at the metatarsophalangeal joints (MTPJs), as part of the push-off phase of gait, which tightens plantar soft tissues to convert the foot into a relatively stiff, propulsive lever (10) (also see ref. 11). Features of MT head morphology such as "dorsal doming" are thought to facilitate this stiffening mechanism (6, 12); doming occurs when the distal articular surface expands and becomes particularly pronounced dorsally. Comparative analysis of humans and chimpanzees has shown that dorsal doming is correlated with in vivo ranges of motion at the MTPJs, with humans displaying greater doming and a greater range of MTPJ dorsiflexion during bipedalism (9). The form and function of the hominin forefoot have been studied extensively (5, 6, 13-16), especially in light of more recent discoveries of hominin pedal fossils (17-19). However, a quantitative analysis of the hominin forefoot in a broad phylogenetic context is lacking, despite the theorized importance of these bony elements to the biomechanical demands of bipedalism (10, 20). To better understand the adaptive evolution of bipedalism in early hominins we investigated MTPJ morphology in Plio-Pleistocene fossil hominins (including species of Ardipithecus, Australopithecus, Paranthropus, and Homo) and a comparative sample of fossil and extant anthro-poids (including modern humans, apes, and monkeys) using shape analyses and phylogenetic comparative methods to test hypotheses about the nature and timing of forefoot evolution in the human clade. Three-dimensional geometric morphometric techniques were used to quantify MT1-MT5 head shapes, and a multioptima Ornstein-Uhlenbeck (OU) model was used to estimate the placement and Significance A critical step in the evolutionary history leading to the origins of humankind was the adoption of habitual bipedal locomotion by our hominin ancestors. We have identified novel bony shape variables in the forefoot across extant anthropoids and extinct hominins that are linked functionally to the emergence of bipedal walking. Results indicate a consistent and generalizable pattern in hominin pedal evolution that spans from Ardipithecus to early Homo-the relatively late derivation of a modern hallux in comparison with the lateral rays. These data provide novel morphological and macroevolutionary evidence for how and when the hominin pedal skeleton evolved to accommodate the unique biomechanical demands of bipedalism.