The fracture of the femoral neck is one of the most clinically relevant fragility fractures in the elderly. The burden of hip fracture has greatly increased over the past few decades due to the increasing life expectancy and increasing osteoporosis prevalence. Such injuries are linked to longer hospital stay, decreased mobility, decreased independence, higher health care costs and significant short and long term mortality. Low energy

trauma, typically from a fall from standing height, is the cause of most femoral neck fractures in elderly people, reflecting both the decreased bone strength and age-related alterations in balance and muscle function (1-3).

Anatomical aspects of the femoral neck fracture are important because of their implications in the stability, compromise of blood supply, treatment and prognosis. The Garden classification classifies fractures based on the degree of displacement while the Pauwels classification classifies fractures based on the direction of the fracture line and the mechanical effects. The higher the grade of the higher grade the more the displacement; the higher the Pauwels the more the fracture is vertical and the more the shear stress across the femoral neck. Proximal femoral anatomy varies for many reasons, including trauma mechanics, proximal femoral geometry, quality of cortical and trabecular bone, osteoporosis, and metabolic abnormalities influencing the strength of the bone (4-6).

Vitamin D is an essential factor for bone health, which is evident from its ability to maintain calcium and phosphate homeostasis and promote normal mineralisation of the skeleton. Vitamin D deficiency is frequently encountered in older persons due to diminished production in the skin, decreased sunlight exposure, inadequate dietary intake, decreased absorption and age-related changes in the physiology. Low vitamin D can lead to secondary hyperparathyroidism, bone loss, muscle weakness, imbalance and fall fractures. It is thus possible that vitamin D status could affect fracture occurrence and also the fracture structure after fracture (7-9).

Osteocalcin is a non-collagenous protein synthesized mainly in the osteoblasts and generally accepted to be a biochemical marker of bone formation and turnover. Variations in circulating osteocalcin levels could be used as indicators of changes in skeletal remodeling and metabolic bone activity. In elderly patients with osteoporosis and/or patients with increased bone turnover, disturbed levels of osteocalcin could be a sign of disturbances in the relationship between bone formation and resorption. Despite the high number of studies investigating the relationship between osteocalcin and bone mineral density, osteoporosis, and fracture risk, there are fewer studies considering the anatomical configuration and severity of femoral neck fractures (10-12).

Understanding the relationship between biochemical markers of bone metabolism and fracture anatomy may offer additional insight into the biological factors underlying severe or unstable fracture patterns. Most previous investigations have focused on vitamin D deficiency, osteoporosis, fracture risk, and postoperative outcomes rather than directly examining the association of vitamin D and osteocalcin with Garden grade, Pauwels classification, displacement, and other anatomical characteristics. Therefore, the present study was conducted to determine the association of serum osteocalcin and vitamin D levels with the anatomical characteristics of femoral neck fractures in elderly patients

This hospital-based cross-sectional analytical study was conducted at the Orthopedic B Unit DHQ Teaching Hospital, Dera Ismail Khan and Department of Orthopedic Hayatabad Medical Complex, Peshawar, from April 2025 to October 2025. The study was designed to determine the association of serum osteocalcin and vitamin D levels with the anatomical characteristics of femoral neck fractures in elderly patients. A total of 97 patients fulfilling the predefined eligibility criteria were enrolled during the study period. Patients were recruited through a non-probability consecutive sampling technique after obtaining informed consent. Patients age 60 years and older with radiologically confirmed femoral neck fracture were eligible for study. Acute fracture cases were included in both genders, and were mostly low-energy trauma (fracture from falling from standing height). Patients with pathological fractures as a result of malignancy, high-energy polytrauma, previous surgery or any condition that significantly affects bone turnover (metabolic bone disease other than osteoporosis, chronic renal or hepatic failure, prolonged corticosteroid therapy) were excluded. Patients on therapeutic doses of vitamin D or drugs which significantly alter bone metabolism prior to presentation were also excluded where this might affect biochemical interpretation. Demographic and clinical data were collected on a structured data collection proforma following enrolment. Variables considered were age, sex, body mass index, mechanism of injury, side affected, previous history of fragility fracture, and major comorbidities. Pelvic and affected hip radiographs were assessed to record the characteristics of the fracture in the affected hip. Femoral neck fractures were categorized by Garden classification (grades I–IV) and Pauwels (types I–III) classification. The fractures were then further subdivided as displaced or undisplaced and as subcapital, transcervical or basicervical based on the anatomical location of the fracture. The femoral neck-shaft angle was also documented, as well as the presence or absence of posterior comminution, when radiographs were available. Blood samples were drawn from the venules, preferably before definitive surgical therapy and before starting vitamin D therapy. Serum was separated by routine laboratory methods and the levels of osteocalcin and 25-hydroxyvitamin D [25(OH)D] were measured. The serum osteocalcin was measured as a biochemical marker of bone turnover and expressed in ng/mL. Additionally, serum 25(OH)D was reported in ng/mL and classified as deficient, insufficient, or sufficient at levels <20, 20–29.9, and ≥30 ng/mL, respectively. Serum calcium, phosphate and alkaline phosphatase were also measured to give an overall picture of bone mineral metabolism. Routinely available and standard laboratory procedures were used to take all the laboratory measurements at the study institution. IBM SPSS Statistics (Version 25.0) was used to enter and analyze data. Means and standard deviations were used to report about the continuous variables (age, BMI, osteocalcin, vitamin D, calcium, phosphate, alkaline phosphatase and neck-shaft angle) which were approximately normally distributed, and percentages and frequencies were used to report about the categorical variables. Prior to conducting inferential testing, the distribution of continuous variables was assessed. When parametric assumptions were met differences in mean osteocalcin and vitamin D concentrations between Garden and Pauwels categories were analysed by one-way ANOVA; otherwise an appropriate non-parametric alternative was used. The independent-samples t-test or the Mann–Whitney U test was used to compare the results of displaced fractures with those of undisplaced fractures. Spearman's rank correlation coefficient was used to assess the relationship of the serum osteocalcin and vitamin D levels to the ordinal fracture classifications, and the Pearson's correlation or Spearman's correlation was used to assess the relationship of the serum osteocalcin and vitamin D levels with the continuous anatomical measurements, neck-shaft angle, according to the data distribution. When appropriate, multivariate regression analysis was done to determine if the relationship between osteocalcin and severe fracture morphology remained statistically significant after controlling for other factors that might have confounded the association, including age, sex and BMI. A p value less than 0.05 was regarded as statistically significant and results are reported with the corresponding 95% confidence interval.

In all, 97 elderly patients with femoral neck fractures were studied. Participants' mean age was 71.84 ± 7.36 years, ranging from 60 to 89 years. The female patients were slightly more, 56 (57.7%) cases, and the male were 41 (42.3%) cases. The mean body mass index was 25.61 ± 3.42 kg/m². The most common mechanism of injury was low energy fall from standing height in 83 (85.6%) patients. Fractures were seen in 51 (52.6%) – the right side and 46 (47.4%) – the left side. Fragility fracture was documented in 21 (21.6%) patients that had a previous history of fragility fracture.

Table 1. Demographic and clinical characteristics of the study participants (n = 97)

The mean serum osteocalcin level was 18.72 ± 6.41 ng/mL and serum 25 hydroxy vitamin D was 20.48 ± 8.17 ng/mL. Forty-eight (49.5 %) patients had low vitamin D levels (serum < 20 ng/mL) and 31 (32.0 %) had low levels of vitamin D (serum < 20 ng/mL) but 18 (18.6 %) had sufficient vitamin D levels (serum > 20 ng/mL). The mean serum calcium concentration was 8.71 ± 0.61 mg/dL, mean phosphate was 3.39 ± 0.57 mg/dL, and mean alkaline phosphatase was 111.63 ± 31.26 U/L.

Table 2. Biochemical profile of the study participants

The fracture pattern was assessed with Garden classification which showed that the commonest fracture pattern was Garden grade III in 31 (32.0%) patients and Garden grade IV in 28 (28.9%). In all, 59 (60.8%) patients had a displaced fracture (Garden grade III or IV). In this classification, Type II fractures were the most common, with 42 patients (43.3%), followed by 31 patients (32.0%) with Type III fractures. The most common site of fracture was the subcapital (48 (49.5%) patients). The mean femoral neck-shaft angle was found to be 126.42 ± 6.81 degrees, and 29 (29.9%) patients were found to have posterior comminution.

Table 3. Anatomical characteristics of femoral neck fractures

There was a decrease in serum vitamin D as the Garden fracture grade increased. Patients with Garden grade I fractures had a mean vitamin D concentration of 27.41 ± 7.62 ng/mL, compared with 23.76 ± 7.09 ng/mL in grade II, 18.83 ± 6.65 ng/mL in grade III, and 15.92 ± 6.27 ng/mL in grade IV. The differences between Garden grades were statistically significant (p < 0.001). There was also significant difference between the levels of serum osteocalcin by the fracture severity, ranging from 15.21 ± 4.87 ng/mL in Garden grade I to 22.04 ± 6.42 ng/mL in Garden grade IV (p = 0.003). The same results were observed based on Pauwels classification. Patients with Pauwels Type II fractures had a mean vitamin D level of 20.18 ± 7.39 ng/mL and Type III fractures 16.86 ± 6.72 ng/mL, which was significantly lower than the mean vitamin D level of 25.67 ± 7.61 ng/mL in patients with Pauwels Type I fractures (p < 0.001). Serum osteocalcin levels were found to be elevated in all the corresponding fracture groups, the highest being in Pauwels Type III fractures (21.33 ± 6.52 ng/mL, p = 0.012).

Table 4. Association of serum osteocalcin and vitamin D with fracture characteristics

The mean levels of serum vitamin D (17.32 ± 6.84 vs. 25.39 ± 7.28 ng/mL, p < 0.001) were significantly lower in patients with displaced femoral neck fracture than in those with undisplaced fractures. In contrast, mean levels of serum osteocalcin were significantly higher in patients with displaced fractures (20.27 ± 6.62 ng/mL) than in patients with undisplaced fractures (16.31 ± 5.29 ng/mL, p = 0.005). A significant negative association was found between serum vitamin D levels and Garden fracture grade (Spearman's ρ = −0.46, p < 0.001) and Pauwels fracture type (ρ = −0.39, p < 0.001) in the correlation analysis. Serum osteocalcin level was statistically significantly correlated with the Garden fracture grade (ρ = 0.31, p = 0.002) and Pauwels classification (ρ = 0.27, p = 0.008). There was also a moderate positive correlation of vitamin D with the femoral neck-shaft angle (r = 0.26, p = 0.011).

Table 5. Correlation of serum biomarkers with anatomical fracture characteristics

Overall, lower serum vitamin D levels were associated with more severe, displaced, and vertically oriented femoral neck fracture patterns, whereas higher serum osteocalcin concentrations were associated with increasing Garden grade, Pauwels type, and fracture displacement. These findings indicate a significant relationship between biochemical markers of bone metabolism and the anatomical severity of femoral neck fractures among elderly patients.

Figure 1. Mean serum osteocalcin and vitamin D levels across Garden fracture grades I–IV.

The graph shows a progressive increase in serum osteocalcin and a corresponding decrease in serum vitamin D with increasing fracture severity.

The present study evaluated the association of serum osteocalcin and vitamin D with the anatomical characteristics of femoral neck fractures among 97 elderly patients. A considerable proportion of the study population had suboptimal vitamin D status, with 49.5% classified as vitamin D deficient and a further 32.0% as insufficient. More importantly, vitamin D concentrations showed a progressive decline with increasing anatomical severity of the fracture. Mean vitamin D levels decreased from 27.41 ± 7.62 ng/mL in Garden grade I fractures to 15.92 ± 6.27 ng/mL in Garden grade IV fractures, while a similar decreasing pattern was observed from Pauwels Type I to Type III fractures. Vitamin D levels were also significantly lower among patients with displaced than undisplaced fractures. These observations support the possibility that poor vitamin D status may accompany impaired bone quality and more severe fracture morphology in older adults. Vitamin D deficiency and insufficiency are commonly reported among elderly patients presenting with hip fractures, although the prevalence varies substantially according to population, geography, nutritional status, sunlight exposure, and the definitions used for vitamin D deficiency (13-15). Reduced vitamin D levels were reported in the present study very frequently and this is of clinical significance, due to the importance of vitamin D in calcium homeostasis, skeletal mineralization and musculoskeletal function. Low levels of vitamin D in the elderly can occur in the presence of impaired bone health, diminished muscle strength, decreased mobility and falls susceptibility. There is more recent evidence that the relationship of vitamin D deficiency to hip fracture may be partly explained by a reduction in muscle function, not just bone mineral density. Han et al. also reported low levels of vitamin D in patients with low-energy hip fracture and noted that there were significant differences in vitamin D levels by hip fracture location. A prospective multicenter study of older adults with intertrochanteric fractures in 2024 also reported an inverse correlation between lower vitamin D and calcium levels with the unstable fracture types, indirectly supporting the inverse correlation we observed in our femoral neck fracture population. The results of these studies suggest that biochemical deficiencies could be linked not only with fracture susceptibility, but also with the anatomical configuration of the fracture (16, 17). In the current analysis, serum osteocalcin was a different picture than vitamin D. Osteocalcin levels were higher in displaced than undisplaced fractures, and rose with increasing Garden grade (I to IV). There was also a significant positive correlation between serum osteocalcin and Garden grade and Pauwels classification. The production of osteocalcin is mainly produced by osteoblasts which represents parts of the bone formation and skeletal turnover, and therefore, alterations in circulating concentrations may occur in conditions associated with disturbed bone remodeling. Elevated levels in more severe fractures that are anatomically more severe in our patients could be due to increased or dysregulated bone turnover in skeletal fragility. Several factors, however, may contribute to the differences in serum osteocalcin levels, including age, renal function, metabolic status, and the time of day the samples were collected in relation to the time of injury. Thus, the results of the present study should not be interpreted to indicate that high level osteocalcin alone results in a more severe fracture pattern. Instead, osteocalcin may be a biochemical marker associated with bone remodeling changes (18, 19). Anatomically, Garden grades III and IV accounted for 60.8% of the fractures, showing that displaced fractures made up the majority of fractures. Pauwels Type II was the most common configuration and about a third of patients had Pauwels Type III fractures. One noteworthy aspect of the inverse relationship between vitamin D and increasing Pauwels type is that higher Pauwels grades indicate increasingly vertical fracture orientation and higher shear forces across the femoral neck. Likewise, the high negative correlation between vitamin D and Garden grade indicates that higher levels of vitamin D were linked to high displacement of fracture. However, fracture morphology is multifactorial and depends on the interaction between several factors such as direction and energy of the fall, proximal femoral shape, cortical thickness, trabecular architecture, bone mineral density, and age-related changes in bone material properties. Advances in research over the last few years have highlighted the importance of structural and imaging information of the proximal femur in addition to traditional clinical risk factors to understand hip fragility. Thus, serum biomarkers should be used in addition to and not in place of radiological and clinical evaluation (20). The present results may have clinical implications as vitamin D and osteocalcin may be of value in the assessment of skeletal metabolism in elderly patients with femoral neck fracture. A diagnosis of vitamin D deficiency on admission might assist in the identification of patients with poor musculoskeletal health who could benefit from a complete evaluation for osteoporosis, a nutritional assessment, fall prevention, and appropriate secondary fracture prevention drugs. Optimisation of nutrition and bone health (as appropriate, sufficient calcium and vitamin D) is an important part of care for older people before and after a hip fracture. The present study, however, has some limitations: It was carried out in a single centre and with a small number of patients (97) and may not be generalizable. It is cross-sectional and thus does not allow for determination of a cause-and-effect relationship between biochemical markers and fracture anatomy. Some variables, such as bone mineral density, parathyroid hormone, dietary vitamin D consumption, sun exposure, and comprehensive history of osteoporosis treatment were not included in the main analysis and may have been confounding factors. Further multicenter prospective studies which would include DXA-derived measures, other bone-turnover markers, repeat biochemical markers, and detailed measurement of proximal femoral geometry are recommended to better understand the independent predictive capacity of osteocalcin and vitamin D for fracture morphology and clinical outcomes.

Serum osteocalcin and vitamin D levels were significantly associated with the anatomical characteristics of femoral neck fractures in elderly patients. Lower vitamin D concentrations were observed with increasing Garden grade, higher Pauwels classification, and fracture displacement, whereas serum osteocalcin showed a progressive increase with greater fracture severity. These findings suggest that altered bone metabolism may accompany more severe anatomical patterns of femoral neck fracture. Assessment of vitamin D and bone-turnover markers may therefore provide useful supplementary information when evaluating skeletal health in elderly patients with femoral neck fractures. Further prospective studies are required to determine whether these biomarkers independently predict fracture configuration and whether correction of metabolic abnormalities can influence future fracture risk or clinical outcomes.

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