The relationship between bone form and function is well understood and has been investigated extensively in early studies from the 19th century (Ward, 1838; Von Mayer, 1867; Wolff, 1892, 1986; Evans, 1957), through seminal work in the past decades (Evans, 1973; Lanyon, 1974; Carter & Hayes, 1977; Gibson, 1985; Goldstein, 1987; Frost, 1990; Ciarelli et al. 1991; Biewener et al. 1996), to current research (Keaveny et al. 2001; Jee, 2005; Liu et al. 2006; Gosman & Ketcham, 2008). However, the knowledge of bone biomechanics and the specialized micro anatomy of trabecular characteristics has expanded exponentially over the past two decades with complex studies addressing the continuous modification and alteration of internal bone structure (Compston, 2006; Müller & Van Lenthe, 2006). With this expansion in knowledge there has been a greater understanding of the trabecular changes which occur in response to development (Nuzzo et al. 2003; Ryan & Krovitz, 2006; Gosman & Ketcham, 2008), ageing (Macho et al. 2005; Muller, 2005; Stauber & Muller, 2006, Nagaraja et al. 2007), bone biochemistry (Ripamonti, 2006) and therapeutic intervention (Ding et al. 2003; Pierroz et al. 2006). Traditionally, histomorphometric techniques performed on two-dimensional sections were recognized as the gold standard for the assessment and calculation of trabecular characteristics (Saparin et al. 2006) with occasional extrapolation to the third spatial dimension using various model assumptions of trabecular bone (Parfitt et al. 1987). These histomorphometric techniques were based on the use of optical microscopy and the principles of quantitative histology and stereology (Dalle Carbonare et al. 2005). However, there has been a noticeable and steady shift from these time-consuming techniques to the more widely used and accepted imaging modalities, which are specifically designed to assess three-dimensional microstructures at high resolution and have the benefit of being non-destructive (Genant et al. 2000; Jones et al. 2007). This high degree of spatial resolution coupled with the possibility to observe the internal structure via non-destructive techniques has made it possible to investigate previously inaccessible rare skeletal material (Cunningham & Black, 2009) where destructive analysis was forbidden due to the uniqueness and value of the material involved. The introduction of three-dimensional imaging techniques and associated software, which have the capabilities of handling large datasets and calculating complex trabecular characteristics, have been instrumental in the development of knowledge into the microenvironment of trabecular architecture. The imaging technique of choice for trabecular bone analysis is micro-computed tomography (Qin et al. 2007), an imaging modality which can visualize the internal structure of intact bones with a high degree of spatial resolution and provide an efficient and reliable means by which 3D architecture can be quantified (Cooper et al. 2003). However, although the knowledge of trabecular architecture has increased as a direct result of these imaging techniques, studies have generally been confined to animal models due to the size restrictions imposed by the capability of the imaging systems. This has prompted many studies to investigate trabecular architecture using rodent models and in particular the detailed knowledge of bone disease, such as osteoporosis, has increased considerably as investigators can manually control variables such as endocrine influences (Laib et al. 2001; Boyd et al. 2006) or induced stresses (Nakano et al. 2003), thereby assessing changing structural parameters in a longitudinal study. Studies of this kind in the human have been restricted to clinical and post-mortem trephined bone samples taken from various anatomical sites including the vertebrae, iliac crest, and calcaneus (Moore et al. 1989; Chappard et al. 1999; Hildebrand et al. 1999; Glorieux et al. 2000; Thomsen et al. 2002). This is restrictive as only limited anatomical regions can be accessed and an assessment of overall trabecular bone structure cannot be gained. Studies involving whole bone analysis have been curtailed due to micro CT apparatus size restrictions and the fact that with an increased field of view, which is inherent to whole bone analysis, there is a resultant and directly related decrease in image resolution (Kim et al. 2004). This is also the case for clinical CT, as although whole bones can be scanned, even the highest resolution multislice clinical CT scanner cannot produce scan resolutions which are capable of resolving the smallest trabeculae (Patel et al. 2005; Petersson et al. 2006). Only recently have technological advances in micro-computed tomography apparatus allowed for scanners to be produced with gantry sizes capable of accommodating much larger sample sizes coupled with a maintained high spatial resolution (Müller et al. 1998; Ritman, 2004; Stauber & Müller, 2008) in the range required for trabecular visualization (Whitehouse, 1974; Chappard et al. 1999; Byers et al. 2000). With this advance, studies have been able to investigate the ontogenetic development of the complete trabecular architecture within various human bones (Ryan & Krovitz, 2006; Gosman & Ketcham, 2008). However, although the potential is now available for such studies, the paucity of provenanced juvenile material remains restrictive to the advancement of this fundamental area of skeletal biology. As a result, a significant portion of research remains directed to phylogenetic variation in primates (Fajardo & Muller, 2001; Fajardo et al. 2002; Ryan & Ketcham, 2002; Ryan & van Rietbergen, 2005).
Ontogenetic studies of trabecular architecture are important for furthering our understanding of the mechanical properties of bone as during life, bone develops into a load-bearing structure (Mulder et al. 2007) requiring the trabecular architecture to be arranged structurally to accommodate and remodel in response to a life-time of changing stresses (Martinon-Torres, 2003). This structural arrangement is fundamentally important as trabecular architecture has been shown to have a significant role in bone strength and in determining its fundamental biomechanical properties (Majumdar et al. 1998; Ulrich et al. 1999; Muller, 2005; Bevill et al. 2006).
The pelvis is an area within the skeleton which undergoes continually changing stresses throughout development, therefore making it a functionally significant region for investigating ontogenetic trabecular structure. As few studies have considered the pelvic complex as a discrete entity due to its shape and complex structural architecture (Majumder et al. 2004), little is known about the changes to the internal developing structure (Dalstra et al. 1993). As such, this study will investigate the following trabecular parameters: bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N) and trabecular separation (Tb.S) in the neonatal human ilium as a baseline template prior to considering change in relation to the growing child.
In a previous communication (Cunningham & Black, 2009), the gross structural parameters within the neonatal ilium demonstrated an unexpected early trabecular organization which was considered in terms of associated anatomy and functional forces acting during the fetal and neonatal periods of development. This seemingly precocious structural patterning also prompted a reconsideration of the contribution biomechanical influences, in response to bipedalism, makes in securing the pelvic complex as a structurally optimized junctional complex for weight transfer in later years.