Concordance of surgical treatment with AO/OTA subclassification in intertrochanteric femoral fractures

Abstract

Background

This study aimed to evaluate the association between AO/OTA subclassification and treatment selection in intertrochanteric femur fractures and to determine how closely real-world clinical decisions align with classification-based recommendations.

Methods

A retrospective analysis was performed on 474 patients treated for intertrochanteric femur fractures between 2015 and 2020. Fractures were subclassified according to AO/OTA 31-A classification using standard radiographs. Chi-square tests with Cramer’s V were used to assess the relationship between fracture groups and treatment modalities. Multinomial logistic regression evaluated predictors of treatment choice, while guideline adherence was analyzed using binary logistic regression. A p value < 0.05 was considered statistically significant.

Results

PFN was the most frequently applied treatment (74.1%), followed by conservative management (13.5%) and DHS (5.7%). Treatment distribution differed significantly among AO/OTA groups (χ² = 40.408, p < 0.001; Cramer’s V = 0.206). AO/OTA group independently predicted treatment selection (p = 0.002), whereas age (p = 0.179) and sex (p = 0.579) did not independently predict treatment selection. The regression model explained 8–10% of treatment variance (Nagelkerke R² = 0.097). Guideline adherence was 79.3%, with no independent predictors of non-adherence. Additionally, the 95% confidence intervals for regression coefficients crossed 1 for all variables (age: 0.947–1.016; sex: 0.570–1.483; AO group: 0.592–1.199), confirming that none independently predicted adherence. Conservative treatment was relatively frequent due to the cohort’s advanced age and comorbidity burden. Revision surgery occurred in 3.8% of cases.

Conclusions

Although AO/OTA subclassification significantly influences treatment choice, fracture morphology alone is insufficient for determining management. PFN remains preferred across fracture types, while non-operative care is suitable for high-risk patients. Future models should integrate frailty, bone quality, and functional status.

Introduction

Hip fractures in older adults represent a major socioeconomic burden, as they are associated with substantial rates of morbidity and mortality [1–8]. The global incidence of hip fractures continues to rise due to aging populations, increased life expectancy, and a growing burden of osteoporosis, placing substantial clinical and socioeconomic demands on healthcare systems [9–13]. Hip fractures in older adults are associated not only with increased mortality but also with significant loss of muscle mass and long-term functional decline, indicating that hip fracture surgery represents not merely a skeletal intervention but a process that critically influences postoperative functional recovery [14].

Beyond fracture morphology, perioperative patient management plays a crucial role in clinical outcomes following hip fracture surgery. Previous studies have demonstrated that orthogeriatric co-management in elderly hip fracture patients is associated with higher hemoglobin levels at discharge and reduced transfusion requirements, independent of the surgical procedure. These findings indicate that treatment decisions and outcomes in hip fractures depend not only on fracture classification but also on patient optimization and multidisciplinary care [15].

Classification systems play an essential role in guiding treatment decisions and providing a standardized language for clinical communication and research [16]. Several proximal femoral fracture classifications have been proposed, including Garden, Evans, Boyd–Griffin, Tronzo, and the AO/OTA system [17–20]. Among these, the AO/OTA classification is widely used and has demonstrated favorable reliability; however, its detailed subclassifications may reduce interobserver agreement and require substantial practical experience for consistent application [21]. Reverse oblique intertrochanteric fractures are classified as AO/OTA 31-A3, and intramedullary nailing is considered the preferred treatment for this fracture pattern because it allows early weight-bearing and minimizes soft tissue disruption. This example demonstrates that, in certain subtypes, fracture morphology can directly guide treatment selection [22].

Although the AO/OTA system is routinely referenced in clinical practice, the extent to which surgeons’ real-world treatment choices actually align with its subclassification-based recommendations remains unclear. Understanding this alignment is clinically relevant, as discrepancies may reflect variations in practice patterns, differences in experience, or limitations of the classification itself.

Therefore, the aim of this study was to evaluate the alignment between surgical treatment decisions and AO/OTA subclassification in intertrochanteric femoral fractures and to quantify real-world discrepancies between recommended and applied treatment modalities.

Methods

Study type, setting, and duration

This retrospective observational study was conducted at the University of Health Sciences Tepecik Training and Research Hospital between 2015 and 2020.

Population and sample

The study population consisted of patients with femoral intertrochanteric fractures. The final sample included 474 patients (n = 474) who were treated for femoral intertrochanteric fractures and had complete clinical and radiographic data. AO/OTA classification was performed by two experienced orthopaedic surgeons using anteroposterior pelvis and internal rotation radiographs obtained in the emergency department and archived in the PACS system. Computed tomography (CT) was not routinely used. In cases of disagreement, the final classification was determined by a third senior orthopaedic surgeon. Interobserver reliability for the AO/OTA 31-A subclassification was assessed between two orthopedic surgeons. In cases of disagreement, a third senior surgeon provided the final decision. To quantify agreement between the two primary raters, Cohen’s kappa analysis was performed. The kappa coefficient was 0.661 (p < 0.001), indicating good interobserver agreement according to conventional benchmarks. More than ten different orthopaedic surgeons performed the surgeries during the study period, which may have introduced variability in treatment preferences depending on surgeon experience and individual practice patterns. Patients diagnosed with femoral intertrochanteric fracture based on anteroposterior pelvis and internal rotation hip radiographs and treated either surgically or conservatively were eligible for inclusion. Only patients with complete clinical records, adequate radiographic images allowing reliable AO/OTA subclassification, and fully accessible information on treatment modality and follow-up were included in the final analysis. Patients with pathological fractures of metastatic, neoplastic, or metabolic origin; periprosthetic or peri-implant fractures; hemodynamically unstable multiple-trauma cases; and insufficient or missing radiographic images that prevented accurate AO/OTA classification were excluded. Additionally, cases with missing treatment or follow-up data and fractures not classifiable under the AO/OTA 31-A category, including those with significant subtrochanteric extension, were not included in the study .

Treatment approach

The treatment modalities applied to the patients included conservative management, proximal femoral nail (PFN), dynamic hip screw (DHS), hip arthroplasty, intramedullary nailing (IMN), and external fixator–Ilizarov application. Conservative treatment was reserved only for patients with very high surgical risk (high ASA scores or severe comorbidities), terminal illness, or cases in which surgery was refused by the patient or their family. The external fixator–Ilizarov method was not a routine treatment option in this cohort and was applied only in a single patient with an open fracture and severe soft tissue loss.

The parameters examined in the study included sex, age, fracture side, AO/OTA fracture subtype, treatment modality, concomitant upper extremity fractures, and revision surgery.

Data analysis

The data were analyzed using IBM SPSS Statistics 25.0 (IBM Corp., Armonk, NY, USA). Descriptive statistics were presented as frequency (n), percentage (%), mean ± standard deviation, minimum and maximum values. The association between AO/OTA fracture groups and treatment modalities was examined using the Pearson chi-square test, and the effect size was reported with Cramer’s V. A multinomial logistic regression model was used to evaluate whether age and the AO/OTA group independently predicted the applied treatment modality. In addition, guideline adherence was analyzed using binary logistic regression. A p value < 0.05 was considered statistically significant.

Ethical considerations

Approval to conduct the study was obtained from the University of Health Sciences Tepecik Training and Research Hospital Non-Interventional Clinical Research Ethics Committee [Date: 10/04/2025; Approval No: 2025 / 03–12]. The study was carried out in accordance with the principles of the Declaration of Helsinki.

Results

In this study, we examined the relationship between AO/OTA subclassification and the surgical treatment modalities applied in femoral intertrochanteric fractures. A total of 474 patients were included in the study, and age and sex information was available for all individuals. Patient ages ranged from 70 to 97 years, with a mean age of 81.46 ± 6.33 years. Regarding sex distribution, 68.1% of the patients were female (n = 323) and 31.9% were male (n = 151). Fracture laterality analysis showed that 242 patients (51.1%) had right-sided and 232 patients (48.9%) had left-sided femoral involvement (Table 1).

Table 1.

Demographic and clinical characteristics of patients with intertrochanteric femur fractures (N = 474)

Variables	Total	Gendere		p value
		Female	Male
	Mean ± SD (Min–Max)	Mean ± SD (Min–Max)	Mean ± SD (Min–Max)
Age	81.46 ± 6.33 (70–97)	81.81 ± 6.12 (70–97)	80.71 ± 6.7 (70–97)	0.069*

	n (%)	n (%)	n (%)
Side
Right	242 (51.1)	170 (35.9)	72 (15.2)	0.315+
Left	232 (48.9)	153 (32.2)	79 (16.7)
Treatment
Conservative	64 (13.5)	43 (9.1)	21 (4.4)	0.684+
PFN	351 (74.1)	239 (50.4)	112 (23.7)
DHS	27 (5.7)	20 (4.2)	7 (1.5)
Hip Arthroplasty (Partial + Total)	30 (6.3)	20 (4.2)	10 (2.1)
Femoral Intramedullary Nailing	1 (0.2)	0 (0.0)	1 (0.2)
External Fixator	1 (0.2)	1 (0.2)	0 (0.0)
Total	474 (100)	323 (68.1)	151 (31.9)

SD standard deviation, PFN proximal femoral nail, DHS dynamic hip screw

^*Mann Whitney U test

⁺Pearson Chi-Square test, p < 0.05

According to the AO/OTA classification, the most common fracture subtype was AO/OTA A2.2 (29.5%), followed by AO/OTA A1.1 (24.5%) and AO/OTA A1.2 (18.4%). The remaining subtypes were distributed as follows: AO/OTA A2.1 (8.0%), AO/OTA A2.3 (8.2%), AO/OTA A1.3 (3.8%), AO/OTA A3.1 (1.9%), AO/OTA A3.2 (1.5%), and AO/OTA A3.3 (4.2%). When categorized into the three main AO groups, 221 patients (46.6%) were classified as Group 1 (type 31A1), 217 (45.8%) as Group 2 (type 31A2), and 36 (7.6%) as Group 3 (type 31A3) (Table 2). Regarding treatment modalities, PFN was the most frequently applied method, performed in 351 patients (74.1%). Conservative treatment was used in 64 patients (13.5%), DHS in 27 patients (5.7%), hip arthroplasty in 30 patients (6.3%), intramedullary nailing in 1 patient (0.2%), and external fixation in 1 patient (0.2%) (Table 1).

Table 2.

AO/OTA 31-A fracture subtype distribution (N = 474)

Variables	Total	Gender		p value
		Female	Male
	n (%)	n (%)	n (%)
Fracture classification
AO 31 A1.1	116 (24.5)	66 (13.9)	50 (10.6)	0.081+
AO 31 A1.2	87 (18.4)	64 (13.5)	23 (4.9)
AO 31 A1.3	18 (3.8)	10 (2.1)	8 (1.7)
AO 31 A2.1	38 (8)	26 (5.5)	12 (2.5)
AO 31 A2.2	140 (29.5)	107 (22.6)	33 (6.9)
AO 31 A2.3	39 (8.2)	25 (5.3)	14 (2.9)
AO 31 A3.1	9 (1.9)	6 (1.3)	3 (0.6)
AO 31 A3.2	7 (1.5)	5 (1.1)	2 (0.4)
AO 31 A3.3	20 (4.2)	14 (2.9)	6 (1.3)

⁺ Pearson Chi-Square test, p < 0.05

A concomitant upper extremity fracture was present in 17 patients (3.6%). These injuries included proximal humerus fractures, distal radius fractures, combined radius–ulna fractures, olecranon fractures, and shoulder dislocations. Revision surgery was performed in 18 patients (3.8%), most commonly involving arthroplasty procedures (n = 15; 83.3%), followed by PFN (n = 2; 11.1%) and total hip arthroplasty (n = 1; 5.6%).

A significant association was identified between AO/OTA fracture groups and treatment modalities (χ² (10) = 40.408, p < 0.001). In Group A1 (n = 221), PFN was preferred in 71.5% of cases, followed by conservative treatment (11.3%) and DHS (7.7%). In Group A2 (n = 217), PFN remained the predominant treatment (78.3%), followed by conservative management (13.8%) and DHS (3.7%). In Group A3 (n = 36), PFN was used in 63.9% of patients, conservative treatment in 25.0%, DHS in 5.6%. Cramer’s V was calculated as 0.206 (p < 0.001), indicating a low-to-moderate but statistically significant relationship between fracture stability and treatment selection (Table 3, Fig. 1).

Table 3.

Distribution of treatment modalities according to AO/OTA 31-A fracture subtypes (N = 474)

Total		Treatment modality
		Conservative	PFN	DHS	Hip arthroplasty	Femoral intramedullary nail	External fixator	p value
Variables	n (%)	n (%)	n (%)	n (%)	n (%)	n (%)	n (%)
Fracture classification								< 0.001+
AO 31 A1.1	116 (24.5)	15 (3.2)	79 (16.7)	10 (2.1)	12 (2.5)	0 (0)	0 (0)
AO 31 A1.2	87 (18.4)	9 (1.9)	62 (13.1)	7 (1.5)	9 (1.9)	0 (0)	0 (0)
AO 31 A1.3	18 (3.8)	1 (0.2)	17 (3.6)	0 (0)	0 (0)	0 (0)	0 (0)
AO 31 A2.1	38 (8)	4 (0.8)	28 (6)	3 (0.6)	3 (0.6)	0 (0)	0 (0)
AO 31 A2.2	140 (29.6)	19 (4.1)	117 (24.7)	2 (0.4)	2 (0.4)	0 (0)	0 (0)
AO 31 A2.3	39 (8.3)	7 (1.5)	25 (5.4)	3 (0.6)	4 (0.8)	0 (0)	0 (0)
AO 31 A3.1	9 (1.8)	3 (0.6)	4 (0.8)	2 (0.4)	0 (0)	0 (0)	0 (0)
AO 31 A3.2	7 (1.4)	3 (0.6)	4 (0.8)	0 (0)	0 (0)	0 (0)	0 (0)
AO 31 A3.3	20 (4.2)	3 (0.6)	15 (3.2)	0 (0)	0 (0)	1 (0.2)	1 (0.2)

PFN proximal femoral nail, DHS dynamic hip screw

⁺Pearson chi-square test, p < 0.05

Fig. 1.

Distribution of AO/OTA fracture subtypes by treatment modality

To evaluate factors influencing treatment decisions, a multinomial logistic regression analysis was conducted with age, sex, and AO/OTA fracture subtypes as independent variables. The overall model was significant (χ² = 39.363, df = 20, p = 0.006). Cox–Snell and Nagelkerke pseudo R² values were 0.080 and 0.097, respectively, showing that approximately 8–10% of the variance in treatment selection was explained by the model. AO/OTA fracture groups were found to be an independent and statistically significant predictor of treatment choice (χ² = 28.096, df = 10, p = 0.002), whereas age (p = 0.179) and sex (p = 0.579) were not significantly associated with treatment modality.

To assess whether applied treatments were consistent with commonly accepted management principles, a “guideline_adherence” variable was created. Among the 474 patients, 376 (79.3%) received a treatment deemed adherent to guideline recommendations, while 98 (20.7%) received a non-adherent treatment. Logistic regression assessing factors potentially associated with guideline adherence—age, sex, and AO group—revealed that none were significant predictors of adherence (age: p = 0.291; AO group: p = 0.340; sex: p = 0.730). Model fit was limited (Hosmer–Lemeshow χ² = 18.329, p = 0.019), and explained variance was low (Cox & Snell R² = 0.004; Nagelkerke R² = 0.007). The overall classification accuracy was 79.3%, reflecting the high adherence rate within the sample. Additionally, the 95% confidence intervals for the regression coefficients crossed 1 for all variables (age: 0.947–1.016; sex: 0.570–1.483; AO group: 0.592–1.199), which confirmed that none of these factors independently predicted guideline adherence.

A concomitant upper extremity fracture was identified in 17 patients (3.6%). The prevalence was 3.4% in surgically treated patients and 4.7% in those treated conservatively. There was no statistically significant difference between treatment groups with regard to the presence of concomitant fractures (Pearson χ² = 0.259, p = 0.611). The effect size was minimal and not significant (Cramer’s V = 0.023).

Discussion

This study addresses a significant clinical gap by evaluating the relationship between the AO/OTA subclassification and the treatment modalities applied in intertrochanteric femur fractures. Our findings demonstrated that treatment distribution varied significantly across different AO/OTA groups (p < 0.001). Although this indicates that the classification influences clinical decision-making, the low-to-moderate strength of this association (Cramer’s V = 0.206) suggests that the AO/OTA classification alone is not the sole determinant of treatment selection. While the AO/OTA classification is a strong instrument for defining fracture morphology, its lack of patient-specific biological and clinical factors likely explains much of the variability in treatment decisions.

In the regression analysis, AO/OTA groups were identified as an independent predictor of treatment modality (p = 0.002), although the overall explanatory power of the model remained low (Nagelkerke R² = 0.097). This suggests that treatment decisions are influenced not only by fracture morphology but also by various parameters not included in the classification system—such as frailty level, comorbidities, degree of osteoporosis, functional capacity, and perioperative risk. The absence of independent associations between age (p = 0.179) or sex (p = 0.579) and treatment selection further supports the conclusion that decision-making is shaped by clinical variables beyond the fracture type.

In our study, PFN was the predominant treatment across all AO/OTA groups (74.1%), consistent with the marked increase in PFN use over the last two decades [23]. PFN is associated with shorter operative time and reduced intraoperative blood loss compared with DHS [24, 25]. These advantages make intramedullary fixation a more favorable option for elderly patients with significant comorbidities in whom perioperative risk must be minimized. In a prospective study, Grønhaug et al. analyzed data from 17,341 patients registered in the Norwegian Hip Fracture Register between 2013 and 2019 and reported significantly lower reoperation rates for intramedullary nails compared with DHS in unstable fractures [26]. Furthermore, biomechanical studies have demonstrated the superiority of intramedullary nails, particularly in A3-type fractures [27, 28]. Thus, the preference for PFN in both stable and unstable fracture patterns can be attributed to these biomechanical and clinical advantages. Supporting this, a recent biomechanical study simulating complex AO/OTA 31A2.2 intertrochanteric fractures demonstrated that cephalomedullary nails with superior locking provide construct stability comparable to standard long nails, without significant differences in varus collapse or rotational deformity [29].

In this context, cement augmentation of the blade has recently gained attention as a technique aimed at enhancing implant stability in patients with severe osteoporosis. In the study by Cibula et al., cement augmentation of the blade did not significantly reduce varus deformity, regardless of blade position or fracture stability. The same study indicated that cement augmentation may prevent cut-out in selected high-risk subgroups, although further research is required to clarify its clinical efficacy [30]. Therefore, augmentation appears to be a selective option for osteoporotic individuals rather than a technique suitable for routine use in the general population.

Despite the biomechanical and clinical advantages of intramedullary fixation, failure of internal fixation remains a challenging scenario in a subset of intertrochanteric fractures. In this context, Huang et al. proposed a novel classification system to guide femoral stem selection in hip arthroplasty following failed internal fixation, demonstrating a significant reduction in intraoperative and postoperative periprosthetic fractures and improved functional outcomes. These findings highlight the importance of structured decision-making not only in primary fracture management but also in revision settings [31].

In our study, the rate of conservative treatment was 13.5%, which appears higher than in several previous studies [32]. However, considering the advanced age of our cohort (mean age 81.46 years), substantial comorbidity burden, and overall frailty profile, this rate is clinically expected. In elderly individuals with multiple comorbidities, surgical risks are increased, making non-operative treatment strategies more prominent. Conservative management remains an appropriate approach when surgical risk is unacceptably high, when patients require terminal care, or when surgical intervention is unlikely to provide meaningful functional benefit. Therefore, the higher rate of conservative treatment in our series should not be interpreted as a deviation from classification-based recommendations but rather as a natural reflection of the biological and clinical realities of the geriatric population.

Although 79.3% of treatment decisions were consistent with guideline-based recommendations, age, sex, and the AO fracture group were not significant predictors of guideline adherence. This finding reflects the multidimensional nature of clinical decision-making in real-world practice. While the AO/OTA classification provides a structural framework, surgical decisions are often guided by factors beyond fracture morphology, including frailty, cardiopulmonary reserve, functional capacity, degree of osteoporosis, and patient–family preferences. Thus, the low predictive value for guideline adherence highlights the complexity and individualized nature of treatment selection in geriatric fracture management. Supporting this perspective, Liu et al. demonstrated that orthogeriatric co-management reduces the risk of adverse events in elderly hip fracture patients with multimorbidity, indicating that post–hip fracture outcomes cannot be explained by fracture morphology alone [33]. In a similar context, Han et al. identified advanced age, multiple comorbidities, hypoalbuminemia, and low body mass index as independent predictors of one-year mortality following intramedullary fixation of fragility intertrochanteric fractures [34]. Consistently, Chen et al. reported that advanced age, female sex, a high FRAX score, anemia, osteoporosis, visual impairment, and cognitive dysfunction are significant risk factors for contralateral refracture after hip fracture surgery. Collectively, these findings underscore the dominant role of patient-related factors in determining both short- and long-term outcomes after hip fracture, beyond fracture classification alone [35].

This study demonstrates that while the AO/OTA classification significantly influences treatment selection in intertrochanteric femur fractures, clinical decision-making cannot rely on fracture morphology alone. In elderly and osteoporotic patients, factors such as frailty, comorbidities, and perioperative risk play a critical role, which explains the predominant use of PFN across fracture groups. Despite these findings, the retrospective design and the lack of CT imaging may limit the accuracy of fracture classification. Future prospective studies integrating patient frailty, bone quality, and functional status into decision algorithms are needed to optimize individualized treatment strategies.

Limitations

This study has several limitations. First, its retrospective design restricted the ability to fully capture clinical decision-making details and may have affected data completeness. Second, CT imaging was not routinely available for all patients, which may have limited the accuracy of the AO/OTA subclassification—particularly in differentiating between A2 and A3 patterns. Third, treatment decisions were influenced by the preferences and experience levels of different surgeons, reflecting real-world variability but reducing standardization. Finally, the single-center design may limit the generalizability of the findings. Despite these limitations, the study provides valuable insight due to its large sample size and comprehensive analytical approach.

Author contributions

(1) Conception, Y.T.; (2) Design, Y.T, V.Z, and Ö.U; (3) Supervision, Y.T., and V.Z.; Ö.U.; (4) Funding, Y.T; (5) Materials, Y.T., and V.Z.; (6) Data Collection and/or Processing, Y.T., V.Z., Y.E.Ö., A.A., and D.T.K.; (7) Analysis and/or Interpretation, Y.T., and B.E. (8) Literature Review, Y.T.; (9) Writing Y.T., V.Z., and Y.E.Ö; (10) Critical Review, Y.T., and V.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Data availability

The datasets generated and analyzed during the current study are available from the corresponding author upon reasonable request.

Declarations

Informed consent

Informed consent was waived because of the retrospective design of the study and the analysis of fully anonymized data, in accordance with institutional regulations.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.