European Journal of Cardiovascular Medicine

Accurate estimation of fetal gestational age (GA) is fundamental in obstetrics, perinatal pathology, and forensic medicine[1]. Long bone measurements—particularly femur length—are widely used for in utero dating. However, diaphyseal femur measurements obtained by ultrasound may not capture cartilaginous epiphyseal contributions and thus can underestimate anatomical length[2]. Direct anatomical morphometry of epiphyseal and metaphyseal dimensions provides essential complementary information, particularly for forensic age estimation where skeletal remains are examined post-mortem[3].

Population differences in fetal growth patterns are well documented. Indian fetuses may have different proportional growth compared with Western reference charts; therefore establishing regional, population-specific reference data is crucial for accurate clinical and medicolegal applications[4]. This study focuses on detailed morphometry of proximal (head transverse/vertical diameters, neck vertical diameter, greater trochanter–head fovea distance) and distal (condylar width) femoral structures, plus mid-shaft transverse diameter, in South Indian fetuses between 11 and 30 weeks of gestation, and evaluates their correlations with gestational age. The primary dataset and measurement protocol are those provided in the study materials.

Study design and ethical considerations

This was a retrospective anatomical morphometric study performed on fetal specimens collected at the Department of Anatomy, with institutional ethics committee approval and maternal consent for use in research. Only fetuses without gross external or skeletal malformations were included.

Sample

Thirty fetal specimens of South Indian origin with confirmed gestational ages between 11 and 30 weeks were studied. Gestational age was established from maternal obstetric records and confirmed where available by crown–rump length (CRL) recorded on antenatal ultrasound.

Grouping

For the purpose of systematic analysis and to enable meaningful comparison of morphometric trends across fetal development, all specimens were categorized into four distinct gestational age groups. This stratification ensured that developmental changes could be evaluated in well-defined chronological segments corresponding to early, mid, and late second-trimester growth phases.

Group A consisted of fetuses measuring 11 to 15 weeks of gestation. This interval represents the early second trimester, during which foundational skeletal formation and initial epiphyseal development occur.

Group B included fetuses between 16 and 20 weeks of gestation, a period characterized by active ossification, rapid longitudinal bone growth, and increasing clarity of epiphyseal contours.

Group C encompassed fetuses aged 21 to 25 weeks, corresponding to the mid-second trimester, during which both diaphyseal and epiphyseal regions exhibit steady dimensional expansion and maturation.

Group D comprised fetuses between 26 and 30 weeks of gestation, representing the late second and early third trimester phases, where substantial increases are observed in metaphyseal width, condylar growth, and overall femoral robustness.

This four-tier classification allowed for precise assessment of growth trajectories and facilitated statistical comparisons across increasingly advanced gestational stages.

Dissection and specimen preparation

Fetuses were dissected using standard anatomical technique to expose the femur. Briefly, a lower abdominal horizontal incision with a longitudinal extension to the medial condyle was made; skin and fascia were reflected, thigh musculature (quadriceps, hamstrings, adductors) was carefully separated, and the femur was disarticulated at the hip and knee, preserving cartilaginous epiphyses. Each femur was cleaned of soft tissue while preserving the shape of epiphyses and metaphysis. Photographic documentation of dissection and measurement steps was recorded for quality assurance.

Measurements

All morphometric measurements in this study were obtained using a calibrated digital Vernier caliper (Mitutoyo or equivalent) with a least count of 0.01 mm, ensuring high precision appropriate for fetal bone analysis. Measurements were recorded in centimeters. Whenever both left and right femora were available, each parameter was measured bilaterally, and the mean of the two sides was used for analysis to minimize side-related anatomical variability. To further enhance reliability, each measurement was repeated three separate times, and the average of these readings was taken as the final recorded value (figure 1).

Six anatomical parameters were evaluated in detail, following standardized osteological landmarks:

1. Head Transverse Diameter (HTD): This measurement represented the maximum antero-posterior (transverse) breadth of the femoral head. The caliper jaws were positioned across the widest horizontal point of the head, ensuring perpendicular alignment to the neck axis.
2. Head Vertical Diameter (HVD): The vertical dimension of the femoral head was measured by placing the caliper along its supero-inferior axis. The widest vertical extent of the head cartilage was recorded as the HVD.
3. Neck Vertical Diameter (NVD): This parameter represented the narrowest supero-inferior diameter of the femoral neck. Care was taken to place the caliper at the minimal tapered region between the head and the greater trochanter, avoiding distortion of the soft cartilaginous margins.
4. Greater Trochanter–Head Fovea Distance (GTHFD): This distance was measured as a straight line between two defined landmarks: the most lateral tip of the greater trochanter and the central depression of the femoral head (fovea capitis). This measurement reflects both proximal epiphyseal development and neck orientation.
5. Mid-Shaft Transverse Diameter (MSTD): The transverse diameter at the mid-point of the femoral shaft was measured by identifying the midpoint between the proximal and distal metaphyses. The caliper was positioned transversely across the shaft to obtain the maximum width.
6. Condylar Width (CW): The distal femoral condyles were measured across their maximum transverse breadth. The caliper spanned the most lateral point of the lateral condyle to the most medial point of the medial condyle, capturing the full distal articular expansion.

A detailed stepwise measurement protocol and identification of anatomical landmarks were followed rigorously, with reference to established fetal osteometry guidelines. Representative images documenting the dissection, isolation of the femur, and measurement techniques are provided in the figures section along with corresponding legends, ensuring full reproducibility of the methodology

Data management and statistical analysis

Data were entered into Microsoft Excel and analyzed using SPSS v25.0. Descriptive statistics (mean, standard deviation, range) were calculated for each parameter in every gestational group. Growth rates per week (mm/week) were computed by linear regression slope across the gestational interval. One-way ANOVA followed by Tukey post-hoc tests were used to compare means between groups. Pearson’s correlation coefficient (r) quantified the linear relationship between each morphometric parameter and gestational age. Statistical significance threshold was set at p < 0.05.

Mean values by gestational group

A total of thirty fetal specimens were analyzed and distributed across the four predefined gestational age groups (Groups A–D). The mean values of all six femoral morphometric parameters demonstrated a clear and progressive increase with advancing gestational age. The detailed distribution of these measurements is presented in Table 1.

As shown in Table 1, all proximal and distal femoral measurements—including Head Transverse Diameter (HTD), Head Vertical Diameter (HVD), Neck Vertical Diameter (NVD), Greater Trochanter–Head Fovea Distance (GTHFD), Mid-Shaft Transverse Diameter (MSTD), and Condylar Width (CW)—increased consistently across the four gestational categories.

The proximal epiphyseal parameters (HTD, HVD, NVD) exhibited steady and uniform growth. HTD increased from 0.22 cm in Group A to 0.87 cm in Group D, while HVD increased from 0.22 cm to 0.88 cm. Similarly, NVD showed a rise from 0.22 cm in the earliest group to 0.86 cm in the most advanced gestational group, indicating progressive maturation of the femoral head and neck region.

The trochanteric and metaphyseal parameters also demonstrated proportional growth with gestational age. GTHFD expanded from 0.29 cm in Group A to 1.23 cm in Group D, reflecting the increasing size and spatial separation of the greater trochanter from the femoral head fovea.

The mid-shaft transverse diameter (MSTD) showed a gradual increase from 0.15 cm in Group A to 0.71 cm in Group D, marking substantial diaphyseal growth during the second trimester.

Among all parameters, condylar width (CW) exhibited the largest absolute increment, increasing from 0.76 cm in Group A to 1.80 cm in Group D. This pronounced growth of the distal femur is consistent with early ossification and rapid metaphyseal expansion characteristic of the later second trimester.

Collectively, the measurements presented in Table 1 demonstrate strong age-dependent growth patterns across all femoral regions studied, supporting the reliability of epiphyseal and metaphyseal dimensions as indicators of gestational age

Table 1. Mean values (cm) of femoral parameters across gestational age groups

Growth rates

Linear regression analysis across the full gestational span (11–30 weeks) revealed distinct weekly growth rates for each of the six femoral morphometric parameters (Figure 2). These rates reflect the differential maturation patterns of the proximal and distal femoral epiphysis and diaphysis.

The proximal epiphyseal parameters—HTD (0.32 mm/week), HVD (0.33 mm/week), and NVD (0.32 mm/week)—demonstrated nearly identical weekly increments, indicating a coordinated and proportional enlargement of the femoral head and neck complex during mid-gestation. This uniformity suggests synchronized chondroepiphyseal expansion, consistent with known patterns of proximal femoral development.

The greater trochanter–head fovea distance (GTHFD) showed a higher weekly growth rate of 0.47 mm/week, reflecting the increasing spatial differentiation between the femoral head and greater trochanter. This parameter is influenced by both epiphyseal growth and increasing lever-arm development for hip musculature, making its higher rate biologically plausible.

In contrast, the mid-shaft transverse diameter (MSTD) exhibited the slowest growth rate at 0.28 mm/week, which aligns with the later and more gradual thickening of the diaphysis relative to epiphyseal expansion. Diaphyseal transverse growth is primarily governed by periosteal apposition, which progresses more slowly compared to the rapid chondroepiphyseal growth of the fetal epiphyses.

The condylar width (CW) displayed the most accelerated weekly growth (0.65 mm/week), nearly double that of the head and neck parameters. This pronounced increase reflects the early and robust development of the distal femoral epiphysis, which is a known site of rapid ossification during the late second trimester. The high growth rate of CW aligns with the distal femoral epiphyseal center becoming radiologically detectable around 28–32 weeks, emphasizing its clinical and developmental significance.

Overall, the variation in growth rates highlights region-specific developmental priorities within the femur. Parameters associated with distal epiphyseal development (e.g., CW) grow markedly faster than those associated with diaphyseal thickness (MSTD), reinforcing the utility of epiphyseal measures as sensitive indicators of fetal maturation. These findings provide important normative data for gestational age estimation and contribute to population-specific fetal growth standards.

Linear regression across the gestational span produced the following weekly growth rates (mm/week):

• HTD: 0.32 mm/week
• HVD: 0.33 mm/week
• NVD: 0.32 mm/week
• GTHFD: 0.47 mm/week
• MSTD: 0.28 mm/week (lowest)
• CW: 0.65 mm/week (highest)

Correlation with gestational age

All femoral morphometric parameters demonstrated strong and highly significant positive correlations with gestational age (p < 0.001), indicating that each measurement increases predictably as fetal development progresses. Among the parameters, condylar width (CW) showed the strongest correlation (r ≈ 0.98), reflecting the rapid and consistent growth of the distal femoral epiphysis during mid-gestation. Proximal head and neck measurements—HTD, HVD, and NVD—also showed robust correlations (r ≈ 0.94–0.96), confirming their reliability as indicators of skeletal maturation. The mid-shaft transverse diameter (MSTD) presented the lowest, yet still strong, correlation (r ≈ 0.92), consistent with the relatively slower diaphyseal widening compared to epiphyseal expansion. Overall, these findings validate all six parameters as dependable predictors of gestational

age, with epiphyseal dimensions providing the highest accuracy(figure 3):

• HTD vs GA: r ≈ 0.95
• HVD vs GA: r ≈ 0.95
• NVD vs GA: r ≈ 0.94
• GTHFD vs GA: r ≈ 0.96
• MSTD vs GA: r ≈ 0.92
• CW vs GA: r ≈ 0.98

Statistical comparisons

One-way ANOVA demonstrated statistically significant differences between groups for every parameter (ANOVA p < 0.001). Post-hoc Tukey tests showed that most differences were significant when comparing Group A with Groups C and D, and Group B with Group D, reflecting accelerated growth after mid-gestation.

This study provides detailed, population-specific morphometric data on proximal and distal femoral epiphyseal and metaphyseal parameters in South Indian fetuses between 11 and 30 weeks. All measured parameters displayed a steady, statistically significant increase with gestational age, confirming that epiphyseal and metaphyseal growth is predictable and can be used for age estimation.

Key findings and interpretation

• Condylar width (CW) exhibited the highest absolute increase and the greatest weekly growth rate (0.65 mm/week). This suggests earlier and/or comparatively rapid growth of distal femoral components relative to some proximal measures, consistent with ossification patterns where distal femoral ossification centers appear and enlarge in later mid-gestation. This makes CW particularly useful for estimating GA in later second trimester specimens[5].
• GTHFD showed substantial growth and strong correlation with GA, indicating that greater trochanter–head spatial relationships reflect overall femoral maturation.
• MSTD had the smallest absolute weekly increase (0.28 mm/week) but a large proportional increase across groups, reflecting geometric changes related to shaft growth and early periosteal apposition.

Comparison with previous studies

The trends observed align with prior investigations that report strong relationships between long bone parameters and GA, including diaphyseal and epiphyseal components[6-7]. Where direct comparison is possible, early-gestation measurements from this South Indian cohort were somewhat smaller than Western ultrasound-derived norms (consistent with published observations of ethnic differences in fetal biometrics)[8]. These findings support the need for locally derived reference values for accurate clinical and forensic application.

Forensic and clinical implications

In forensic contexts—where fetal remains are encountered—morphometric parameters that incorporate epiphyseal dimensions augment accuracy in age estimation beyond diaphyseal lengths alone[9]. Clinically, the reference values derived here can contribute to improved antenatal assessment where population-specific centile charts are desirable, and they can aid in the prenatal detection of disproportionate growth or skeletal dysplasia when compared to normative values[10].

Strengths and limitations

Strengths:

This study possesses several notable strengths that enhance the reliability and relevance of its findings. First, the use of direct anatomical measurements, which include cartilaginous epiphyses, provides a more accurate representation of true femoral dimensions compared with ultrasound-based diaphyseal measurements that often exclude these structures. This approach ensures superior anatomical precision, especially important for forensic and developmental assessments. Second, the study followed a systematic and well-standardized measurement protocol, incorporating repeated readings and bilateral comparisons wherever possible. Detailed photographic documentation of dissection and measurement procedures further strengthens methodological transparency and reproducibility.

Limitations:

The present study has certain limitations that should be acknowledged. The sample size was relatively modest (n = 30), which restricts the ability to generate detailed week-by-week centile charts. Additionally, all specimens were sourced from a single tertiary care center, limiting the generalizability of the findings to broader regional or socioeconomic populations. A small number of fetuses lacked complete bilateral measurements for all parameters, which may have introduced minor variability in the dataset. Future research incorporating larger, multicentric samples would help strengthen population-specific reference standards and enhance the robustness of morphometric correlations.

Proximal and distal femoral morphometric parameters (HTD, HVD, NVD, GTHFD, MSTD, CW) demonstrate strong, statistically significant linear correlations with gestational age in South Indian fetuses between 11 and 30 weeks. Condylar width shows the most rapid growth and is a particularly informative marker in the later second trimester. The population-specific reference values generated in this study complement existing femur length standards and will be useful in clinical obstetrics, prenatal diagnostics, and forensic age estimation. Larger, multi-regional studies are recommended to expand these reference data into centile charts applicable on a week-by-week basis.

1.       Jeanty P, Rodesch F, Delbeke D, Dumont JE. Estimation of gestational age from measurements of fetal long bones. J Ultrasound Med. 1984;3(2):75–79.

2.       Dhawan V, Kapoor K, Sharma M, Singh B, Sehgal A. Morphometry of fetal femora as an indication of gestational age. Eur J Anat. 2013;17(3):148–153.

3.       Ziylan T, Murshed KA. An assessment of femur growth parameters in human fetuses and their relationship to gestational age. Turk J Med Sci. 2003;33(1):27–32.

4.       Fazekas IG, Kósa F. Forensic Fetal Osteology. Budapest: Akademiai Kiado; 1978.

5.       Ubelaker DH. Estimating age at death from immature human skeletons: an overview. J Forensic Sci. 1989;32(5):1254–1263.

6.       Lim JMH, Hong A, Raman S, Shyamala N. Relationship between fetal femur diaphysis length and neonatal crown-heel length: the effect of race. Ultrasound Obstet Gynecol. 2000;15(2):131–137.

7.       Carneiro C, Curate F, Cunha E. A method for estimating gestational age of fetal remains based on long bone lengths. Int J Legal Med. 2016;130(5):1333–1341. doi:10.1007/s00414-016-1393-5

8.       Rawal J, et al. Ultrasonographic fetal femur length in Indian population. Indian J Radiol Imaging. 2012;22:54–60.

9.       Saha S, et al. Ethnic variations in fetal growth. Eur J Obstet Gynecol Reprod Biol. 2024;295:112–8.

10.    Ziylan T, et al. Fetal femoral morphometry. Surg Radiol Anat. 2005;27:487–92.