European Journal of Cardiovascular Medicine

The estimation of fetal gestational age (GA) is a cornerstone in obstetrics, fetal medicine, anthropology, and forensic science. Among various anatomical parameters, femur length has consistently been recognized as one of the most reliable indicators of fetal age and skeletal maturity. The femur begins ossification early in fetal life and demonstrates a steady, predictable growth pattern throughout gestation.

Ultrasound-based measurements of femur length are widely used for clinical assessments in antenatal care (Hadlock et al., 1985). However, ultrasound may underestimate true anatomical length due to the inability to visualize cartilaginous epiphyses, particularly during early gestation. Direct anatomical measurements, therefore, provide more accurate normative values—especially crucial in forensic investigations involving fetal remains, where precise age determination is often legally mandated.

Despite extensive work on fetal femur length in Western populations (Jeanty et al., 1984; Maršál et al., 1996), there is a scarcity of normative anatomical data for Indian fetuses. Ethnic variability in skeletal development necessitates population-specific datasets (Dhawan et al., 2013). Such reference values are indispensable for accurate GA estimation, fetal anomaly detection, growth restriction diagnosis, and anthropometric research.

This study provides a detailed investigation of longitudinal femoral growth in South Indian fetuses, focusing on two anatomical measurements:

• FL1: Greater trochanter to lateral condyle
• FL2: Fovea capitis to medial condyle

These parameters were chosen to capture lateral and medial growth trajectories, including epiphyseal contributions. This research creates a robust dataset for fetal age estimation and serves as a reference for future clinical and forensic applications.

Study Design and Sample Size

A descriptive anatomical study was conducted on 30 spontaneously delivered normal fetal specimens collected from a tertiary medical institution in South India. Gestational age ranged from 11 to 30 weeks.

Ethical approval was obtained, and all specimens were handled following institutional biomedical waste and anatomical guidelines.

Gestational Age Grouping

For the purpose of systematic analysis, all fetal specimens were categorized into four distinct gestational age groups. Group A comprised fetuses aged 11 to 15 weeks, representing early second-trimester development. Group B included fetuses between 16 and 20 weeks, a period characterized by rapid skeletal growth and early ossification. Group C consisted of fetuses aged 21 to 25 weeks, during which significant maturation of long bones and epiphyseal structures occurs. Group D comprised fetuses aged 26 to 30 weeks, reflecting advanced skeletal development approaching late second to early third trimester. Gestational age for all specimens was confirmed through a combination of obstetric records, crown–rump length (CRL) measurements, and date-based estimation methods, ensuring the highest possible accuracy in age determination Fetuses were grouped into four categories:

Gestational age was confirmed using obstetric records, crown–rump length (CRL), and date-based estimation.

Dissection Procedure

To expose and isolate the fetal femur, a systematic dissection procedure was followed. Initially, a horizontal incision was made across the lower abdomen to gain access to the underlying anatomical layers. This was followed by a vertical incision extending from the inguinal region down to the medial condyle, allowing adequate exposure of the thigh compartment. The skin and superficial fascia were carefully reflected, revealing the deeper muscular structures of the thigh. The major muscle groups—including the quadriceps anteriorly, the hamstrings posteriorly, and the adductor muscles medially—were gently separated to avoid damage to the underlying bone. Once the femoral shaft and its articulating ends were sufficiently exposed, the bone was disarticulated from the hip joint at the proximal end, and subsequently separated from the knee joint distally, ensuring the integrity of both epiphyses. All remaining soft tissues, including periosteum, connective tissue, and remnants of musculature, were meticulously removed to obtain a clean and measurable femoral specimen. Throughout the procedure, photographic documentation was performed using a 10-megapixel digital camera to record each stage of dissection for reference and validation

Measurement of Femur Length

For each fetal specimen, femur length was recorded using two distinct anatomical reference points to capture both lateral and medial growth dimensions. The first measurement, termed FL1, represented the lateral femoral length, defined as the linear distance extending from the greater trochanter superiorly to the lateral condyle inferiorly. This measurement reflects the primary diaphyseal growth pattern along the lateral aspect of the bone. The second measurement, designated as FL2, corresponded to the medial femoral length, measured from the fovea capitis located at the center of the femoral head to the medial condyle at the distal end. This parameter incorporates additional structural components such as the femoral head and neck, thereby providing a more comprehensive representation of total femoral growth. Both measurements were taken with meticulous precision using a digital Vernier caliper to ensure accuracy and reproducibility.

Instruments

• Digital Vernier caliper (accuracy 0.01 mm)
• Stainless steel dissection set
• Latex-free gloves
• Formalin containers
• Sterile green surgical drape (background for photography)

Each measurement was taken three times, and the mean value was recorded.

Statistical Analysis

All statistical analyses were conducted using SPSS software, version 26. Descriptive statistics, including the mean and standard deviation (SD), were calculated for all morphometric parameters to summarize the distribution of femoral measurements across gestational groups. To determine whether significant differences existed among the four gestational categories, a one-way analysis of variance (ANOVA) was performed. The strength and direction of the association between femur length (FL1 and FL2) and gestational age (GA) were evaluated using the Pearson correlation coefficient, providing insight into the linearity of these relationships. Additionally, the weekly growth rate of both femoral length parameters was derived by computing the slope of the linear regression line, representing the average increase in femoral length per week of gestation. A p-value of less than 0.05 was considered statistically significant for all analyses, ensuring rigorous evaluation of the findings.

Femoral Length Measurements Across Gestational Groups

The analysis of femoral length across gestational categories demonstrated a clear and consistent pattern of linear growth in both measurement parameters, FL1 and FL2. As shown in Table 1, fetuses in Group A (11–15 weeks) exhibited mean femoral lengths of 2.40 cm (FL1) and 2.06 cm (FL2), reflecting the early stages of femoral ossification. These measurements increased substantially in Group B (16–20 weeks), with FL1 reaching 3.87 cm and FL2 increasing to 4.09 cm, indicating accelerated mid-gestational growth. Further progression was observed in Group C (21–25 weeks), where mean FL1 and FL2 measurements rose to 4.95 cm and 5.18 cm, respectively. The greatest lengths were recorded in Group D (26–30 weeks), with mean FL1 measuring 6.73 cm and FL2 measuring 6.91 cm, corresponding to advanced maturation of both the diaphysis and epiphyseal structures. Overall, both femoral length parameters demonstrated a steady and predictable increase with gestational age, reflecting normal fetal skeletal development and underscoring the strong correlation between femoral growth and advancing gestation.

Table 1. Mean femoral lengths (FL1 & FL2) by gestational group

Both FL1 and FL2 showed progressive increase across all groups.

Growth Rate Analysis

Analysis of the weekly increase in femoral length revealed a clear and consistent pattern of progressive growth throughout gestation. The FL1 parameter, which reflects the lateral measurement of the femur, demonstrated an average growth rate of 2.16 mm per week, indicating steady elongation of the diaphysis during fetal development. In comparison, the FL2 parameter, representing the medial measurement that includes the femoral head and neck, exhibited a slightly higher growth rate of 2.42 mm per week. This greater increase in FL2 highlights the additional contribution of the proximal epiphyseal structures to overall femoral length. Notably, across all gestational age groups, FL2 consistently exceeded FL1, emphasizing its heightened sensitivity as a marker of fetal skeletal maturation and its potential value in improving the accuracy of gestational age estimation.

Linear Relationship with Gestational Age

The statistical evaluation of the association between femoral length and gestational age(figure 6)  demonstrated a remarkably strong linear relationship for both measurement parameters. The Pearson correlation coefficient for FL1 in relation to gestational age was r = 0.962, indicating a highly significant positive correlation. Similarly, the correlation between FL2 and gestational age was even stronger, with a coefficient of r = 0.979, reflecting near-perfect linearity. Both correlations achieved statistical significance at p < 0.001, underscoring the reliability of femoral length as an indicator of fetal maturity. These results confirm that femoral length increases in a predictable manner with advancing gestation and further highlight FL2 as the more sensitive and accurate parameter for estimating fetal age due to its inclusion of proximal epiphyseal growth.

Femur length has consistently been regarded as one of the most reliable skeletal parameters for determining fetal gestational age, owing to its predictable and progressive pattern of growth throughout intrauterine development. The findings of the present study reaffirm this established understanding and contribute valuable population-specific anatomical data for South Indian fetuses—an area in which normative datasets remain limited. By providing detailed direct measurements of femoral length across gestational groups ranging from 11 to 30 weeks, this research enhances the existing repository of fetal morphometric standards and supports the development of regionally appropriate growth references.

Comparison With Previous Studies

When compared with established Western ultrasound-based reference charts, such as those developed by Hadlock et al. (1985) and Jeanty et al. (1984), the femoral lengths recorded in the present study show minor deviations. These differences are expected and likely attributable to several factors. First, ethnic and racial variations in skeletal development have been widely documented, with studies indicating that Asian, European, and African populations demonstrate measurable distinctions in fetal biometric parameters (Lim et al., 2000).

Second, nutritional status and maternal health, which vary substantially across geographic regions, may influence fetal skeletal growth.Third, and most importantly, differences in methodology contribute significantly to the observed variation. Western datasets primarily rely on ultrasound-based diaphyseal measurements, which do not account for cartilaginous epiphyses. In contrast, the present study employs direct anatomical measurement, which provides a more comprehensive assessment of true femoral length.

The results of this study align closely with those reported by Dhawan et al. (2013), who examined femoral morphometry in North Indian fetuses and similarly identified steady, linear growth of the femur with gestational progression. The concordance between the current findings and those from other regions of India reinforces the existence of intra-national consistency, while still acknowledging deviations from Western populations.

Why FL2 Consistently Exceeds FL1

A notable observation in this study is the consistent superiority of FL2 over FL1 at all gestational ages. This distinction can be explained by fundamental anatomical differences inherent to the two measurement approaches.FL2 includes the femoral head, the neck, and the associated cartilaginous epiphyses, all of which contribute additional measurable length beyond the diaphyseal axis captured by FL1. The rapid proliferation and maturation of these structures, particularly between 16 and 30 weeks of gestation, coincide with peak periods of epiphyseal development. This explains the comparatively higher weekly growth rate recorded for FL2 (2.42 mm/week) relative to FL1 (2.16 mm/week), and underscores the usefulness of FL2 as a more sensitive indicator of overall femoral maturation.

Forensic and Medicolegal Relevance

The implications of this study extend beyond clinical and anatomical domains into the field of forensic medicine, where accurate fetal age estimation plays a critical role in medicolegal proceedings. In cases involving suspected illegal abortion, infanticide, or unattended stillbirth, it is imperative to establish whether the fetus had reached the threshold of viability or term. Femur length serves as a reliable index for determining fetal maturity, particularly when other soft-tissue-based markers have deteriorated due to decomposition or trauma (Fazekas & Kósa, 1978; Ubelaker, 1989).

Direct anatomical measurements—such as those employed in the current study—are especially valuable in forensic scenarios because they remain unaffected by the limitations of ultrasound and radiography. When fetal remains are incomplete or fragmented, the femur is often among the most resilient skeletal elements available for analysis, making accurate reference values essential for postmortem age estimation.

Overall Significance

The results of this study confirm a robust, statistically significant correlation between femoral length and gestational age, validating the use of both FL1 and FL2 as dependable parameters of fetal development. The stronger correlation observed in FL2 highlights its greater anatomical sensitivity due to inclusion of epiphyseal structures, making it a superior marker for

skeletal maturity assessment.

By establishing normative femoral length values for South Indian fetuses, this study bridges a critical gap in fetal morphometric literature, enabling more accurate and culturally appropriate assessment tools for clinicians, anatomists, and forensic experts.

The present study provides a comprehensive analysis of femoral length development in South Indian human fetuses and establishes clear, population-specific growth patterns for both lateral (FL1) and medial (FL2) femoral measurements. The findings demonstrate that femur length increases in a predictable, linear manner with advancing gestational age, underscoring its reliability as a primary skeletal indicator for fetal age estimation. Among the two parameters evaluated, FL2 exhibited a consistently higher rate of growth owing to its inclusion of the femoral head, neck, and cartilaginous epiphyses, thereby emerging as a more sensitive marker of fetal skeletal maturation.

By generating direct anatomical measurements—unaffected by the limitations of ultrasound imaging—this study fills an important gap in fetal morphometric literature for the Indian population. These normative reference values hold significant clinical relevance for obstetric assessment, fetal growth monitoring, and the early detection of developmental abnormalities. Furthermore, the data have substantial implications in forensic and medicolegal contexts, where accurate estimation of gestational age is essential for determining fetal viability, assessing suspected cases of infanticide or unlawful termination, and supporting expert testimony.

Overall, this research enhances current understanding of fetal skeletal development and provides a scientifically robust framework that can be integrated into anatomical teaching, perinatal care protocols, forensic examination standards, and future multi-regional comparative studies. Continued investigations with larger, more diverse cohorts will further refine these reference standards and strengthen their applicability across broader populations.

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