ObjectivesThe femur is a major weight‐bearing bone that is variably loaded throughout growth as children transition through locomotory states prior to the attainment of a mature bipedal gait. Here, we document ontogenetic trends in femoral cross‐sectional geometry (CSG) and explore how changes in loading regime may impact the structural arrangement of cortical bone along the length of the developing diaphysis.Materials and methodsMicro‐CT scans of 110 immature femora were generated from a documented archaeological sample ranging in age from birth to 8.5 years old. CSG properties indicative of relative bone strength and bending rigidity were analyzed from cross‐sections extracted at 35%, 50% and 65% of total intermetaphyseal length.ResultsInfants experience a marked redistribution of cortical bone between birth and 7 months facilitating a more advantageous mechanical structure for early load bearing behaviors as bone is displaced further from the section centroid. Early walkers are characterized by a mediolaterally reinforced cross‐section that becomes more circular as gait continues to develop.DiscussionDuring ontogeny the femur undergoes distinct morphological phases, which correspond with changes in loading regime. This study illustrates the importance of loading conditions in shaping immature bone morphology. Nonmechanical factors such as changes in hormonal environmental can also impact on this dynamic.

The femoral neck-shaft angle (NSA) can adapt to the early onset of habitual but changeable loading behaviors, such as sitting, crawling, standing, and cruising behaviors, and the adoption of immature through to mature walking patterns. However, normal patterns of skeletal growth can be modified by underlying pathological conditions. Femoral head depression and neck angulation can occur during vitamin D deficiency rickets, but the pattern of NSA deformation occurring during the period of locomotor development in children with rickets has not been widely studied. This study aimed to broaden understanding of rickets beyond historical and bioarchaeological prevalence rates to explore the functional impacts of the condition on femoral development. Radiographs of 200 children from eighteenth-to nineteenth-century London (76 rickets, 124 non-rickets) were measured for femoral NSA. The results demonstrate notable differences in NSA in children with and without rickets, which vary depending on disease status, severity, and age at onset. Children under 2 years with severe and marked cases of active rickets typically presented a higher femoral NSA, which may be attributed to delayed development during this disease phase and/or limited or delayed activity, potentially exacerbated by pain, muscle weakness, and childcare practices. In contrast, children over the age of 1 year with healed rickets frequently displayed femoral neck deformation and reduced NSA likely linked to mechanical loading experienced during the deficiency. Importantly, defects in the proximal femur can develop during recovery from poor mineralization and endochondral defects and may exaggerate the appearance of femoral neck deformation during continued growth.   L’angle cervico-diaphysaire fémoral peut s’adapter à l’apparition précoce de comportements de charge habituels mais changeants, tels que les comportements assis, rampant, debout et de promenade avec appui, et l’adoption de modes de marche immatures à matures. Cependant, les schémas normaux de croissance squelettique peuvent être modifiés par des conditions pathologiques sous-jacentes. Une dépression de la tête fémorale et une angulationdu col peuvent survenir lors de rachitisme par carence en vitamine D, mais le schéma de déformation du NSA survenant au cours de la période de développement locomoteur chez les enfants atteints de rachitisme n’a pas été largement étudié. Cette étude visait à élargir la compréhension du rachitisme au-delà des taux de prévalencehistoriques et bioarchéologiques pour explorer les impacts fonctionnels de la condition sur le développement fémoral. Les radiographies de 200 enfants de Londres du 18e au 19e siècles (76 rachitiques, 124 non- rachitiques) ont été étudiées pour mesurer le NSA fémoral. Les résultats démontrent des différences notables dans la NSA chez les enfants avec et sans rachitisme, qui varient en fonction de l’état de la maladie, de la gravité et de l’âge au début. Les enfants de moins de 2 ans présentant des cas graves et marqués de rachitisme actif présentaient généralement une NSA fémorale plus élevée, qui peut être attribuée à un retard de développement au cours de cette phase de la maladie et/ou à une activité limitée ou retardée, potentiellement exacerbée par la douleur, la faiblesse musculaire et les pratiques de garde. En revanche, les enfants de plus de 1 an atteints de rachitisme guéri présentaient fréquemment une déformation du col fémoral et une réduction de la NSA probablement liée à la charge mécanique subie pendant la déficience. Il est important de noter que des défauts dans le fémur proximal peuvent se développer pendant la récupération après une mauvaise minéralisation et des défauts endochondraux et peuvent exagérer l’apparition de déformations du col fémoral pendant une croissance continue.

The external geometry of the human femur changes markedly during early ontogeny as children learn to sit, crawl, stand, and eventually walk. Here we examine the pattern of femoral angle development in a sample of children from 18th and 19th century London and evaluate how angular changes correspond to key stages of childhood locomotor development. Metaphyseal bicondylar angle (BCA) and neck‐shaft angle (NSA) measurements were collected from radiographs of a documented archeological sample of 112 children aged from birth to 8.5 years. Ontogenetic patterns were assessed by using a local regression (LOESS) to fit curves to each angle parameter according to chronological age and femur length, and group comparisons were made between successive locomotor stages. The results demonstrate an increase in BCA throughout growth, which accelerates rapidly between the ages of 1 and 2 years when children first start to walk with an immature waddling gait. NSA was observed to increase during the first few months after birth, followed by a rapid decline at about 7 months and a steady decline during the second year when children learn to walk. The findings from this study contribute to the current literature on femoral angle development and provide an insight into femur development in children from industrial London. Further research is required to ascertain whether this pattern of NSA development is specific to the studied population.

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