Abstract
Background
Lag screw cutout remains the most frequent mechanical failure after proximal femoral nailing (PFN) for geriatric intertrochanteric femur fractures and is strongly influenced by bone quality, reduction, and implant positioning. This study aimed to evaluate these domains comprehensively and to identify independent predictors of cutout.
Methods
In this retrospective cohort study, patients aged ≥ 65 years who underwent PFN (single implant design, APFN®) for AO/OTA 31.A1–A3 intertrochanteric fractures between January 2017 and June 2025 were reviewed. Patients with follow-up < 6 months, non-APFN fixation, insufficient radiographs, cut-through, pathological fractures, major trauma, severe prefracture dependency, or secondary surgery due to infection/major complications were excluded. Demographics and Charlson comorbidity index were recorded. Preoperative and early postoperative plain AP/lateral radiographs were assessed by three blinded observers (two orthopaedic surgeons and one radiologist) who were not involved in the initial planning or surgery to prevent potential bias, by consensus. Bone quality/morphology (Singh index, Dorr type, fracture type), reduction quality (neck-shaft angle-NSA, Baumgaertner criteria, reduction pattern), and fixation quality (tip-apex distance-TAD, calcar referenced tip-apex distance-CalTAD, lag screw position/Cleveland zones) were analyzed. Receiver operating characteristic (ROC) analysis determined clinically relevant cutoffs, and binary logistic regression analysis identified independent predictors.
Results
A total of 371 patients (mean age 78.8 ± 6.95 years; 66% female) met inclusion criteria. Cutout occurred in 48 patients (12.9%) at a mean of 6.29 ± 5.52 weeks. The cutout group demonstrated significantly poorer bone quality (Singh index 2.56 ± 0.51 vs. 3.70 ± 0.67; p < 0.001), greater varus fixation (NSA 126.6° vs. 131.7°; p < 0.001), higher TAD and CalTAD (both p < 0.001), and a higher proportion of center-anterior zone lag screw position (p < 0.001), which conferred increased risk (Odds ratio-OR 6.26; p < 0.001), whereas center-center zone was protective (OR 0.32; p < 0.001). CalTAD showed the highest discriminative performance for cutout (AUC 0.757; cutoff 26 mm; sensitivity 63.8%, specificity 75%). In logistic regression analysis, only Singh index (OR 0.009; 95% CI 0.001–0.060; p < 0.001) and NSA (OR 0.830; 95% CI 0.710–0.971; p = 0.020) remained independent predictors.
Conclusion
In geriatric intertrochanteric femur fractures treated with PFN, osteoporosis severity and varus fixation are the strongest independent predictors of cutout complication. Meticulous avoidance of varus reduction and anterior lag screw placement combined with rigorous assessment of bone quality may decrease cutout risk.
Keywords: Intertrochanteric femur fracture, Geriatric fractures, Proximal femoral nail (PFN), Lag screw cutout, Osteoporosis, Neck–shaft angle
Background
Intertrochanteric femur fractures are one of the most common fracture types in the geriatric population and are a major cause of mortality and morbidity [1, 2]. Proximal femoral nails (PFNs) are commonly used in the surgical treatment of these fractures [3–5]. Despite significant advances in surgical techniques and implant technology, mechanical failure of the implant remains a persistent problem. The most common reason for failure in the treatment of intertrochanteric fractures with PFN is cutout, which is defined as the perforation of the femoral neck or head by the lag screw as a result of varus collapse of the neck-shaft angle [6].
The cutout rate varies between 1.8% and 16.5% in the literature [7–9]. Several variables associated with cutout have been identified; these can be classified under three main headings: bone quality, reduction quality, and fixation quality [10–13].
Bone quality is closely related to age, gender, and comorbid systemic diseases. It plays a decisive role in the mechanism of fracture formation but is a factor that cannot be altered by intraoperative surgical intervention. In contrast, the quality of reduction and fixation is directly related to surgical technique and experience, and is therefore a parameter that can be controlled by the surgeon. There are a limited number of studies in the literature that address the parameters evaluating these criteria simultaneously in the geriatric patients and holistically assess their effects on the development of lag screw cutout [14, 15].
The main hypothesis of this study is that although cutout development is multifactorial, the most important independent predictive/risk factors for the development of cutout in geriatric intertrochanteric femur fractures treated with PFN will be the grade of osteoporosis and the varus position of the femoral neck.
The aim of this study is to comprehensively evaluate bone quality, reduction quality, and fixation quality-the three key factors in the successful surgical treatment of geriatric intertrochanteric femur fractures-and their relationship with cutout. The goal is to generate more applicable clinical implications for predicting and reducing the risk of cutout for lag screw.
Methods
All procedures involving human participants were performed in accordance with the ethical standards of the institutional committee. This retrospective study was approved by the Institutional Review Board of our university (IRB#716/2025).
Patient inclusion
In this study, AO/OTA type 31.A1/A2 and A3 intertrochanteric femur fractures that underwent surgical treatment between January 2017 and June 2025 were retrospectively evaluated (Fig. 1).
Fig. 1.
The flow diagram of the study
Exclusion criteria
Age <65 years, follow-up ≤6 months, undergone surgical treatment other than PFN, having used an implant other than APFN (APFN® Antirotator Proximal Femoral Nail, TST Medical Devices Inc, Istanbul, Turkey), concomitant fracture or additional organ injuries such as thoracic, cranial and abdominal trauma, pathological fracture, history of previous fracture or surgery in the same or contralateral hip, being completely bedridden or completely dependent on care before the fracture, CAS ≤4, severe cognitive impairment such as dementia, having a malignancy or end-stage organ failure such as chronic renal failure and lack of suitable radiological data. Medial migration of the lag screw towards the acetabulum was called cut-through and was excluded from the study as it was considered a confounding factor because its mechanism of formation may be biomechanically different from cutout [16]. The study also excluded patients who required secondary surgery due to wound infection or surgical complications such as femur diaphyseal fracture, because these situations can have an additional effect on the lag screw cutout, and therefore prevent us from evaluating the independent effect of potential predictive factors.
Evaluation of patients
Detailed demographic and clinical data such as age, sex, body mass index (BMI), fracture type, and Charlson comorbidity index (CCI) were recorded for all patients. Radiological assessments were performed digitally using the picture archiving and communication system (PACS). Radiological evaluations of the patients were performed using preoperative and early postoperative zeroth or first day plain anteroposterior (AP) and lateral radiographs-using the known actual dimensions of the implant as a criterion to eliminate magnification errors. All evaluations were conducted by three independent observers-two orthopedic specialists and one radiologist-who were not involved in the initial planning or surgery to prevent potential bias, and decisions were reached by consensus.
Radiological evaluation
Cutout diagnosis was made by comparing previous control plain radiographs in patients without any new trauma or signs/history of infection in the postoperative period. Newly developed lateral migration of the lag screw or perforation of the lag screw through the femoral neck/head and varus collapse in the head-neck angle and/or rotational deformity in the head-neck segment were considered cutout [17, 18] (Fig. 2). The presence of cortical bridging in both AP and lateral radiographs was considered evidence of bony union [19].
Fig. 2.
An intertrochanteric femur fracture in an 82-year-old female patient resulted in cutout at postoperative 11th week, despite adequate reduction and fixation
Evaluation of bone quality and morphology/type.
Singh index
Used to evaluate osteoporosis, is a simple, practical and semi-qualitative evaluation method performed on plain radiographs [20, 21]. Various studies have confirmed that it is an effective method for determining bone strength/quality because it reflects the structural integrity of the trabecular bone architecture in the proximal femur [22–24]. In this study, the distribution of trabecular bone in the proximal femur was evaluated in plain AP radiographs of the contralateral healthy side hips of the patients, and Singh’s six-grade classification system (Grade I–VI) was used [25]. It is accepted that the arrangement and density of trabecular structures gradually increase as the grade increases.
Dorr index
Used to evaluate the morphology and bone quality of the proximal femur, was calculated by dividing the medullary canal width at the level of the lesser trochanter in plain AP radiographs by the medullary canal width at the level of the isthmus, 10 cm distal to the lesser trochanter [26]. The ratio was classified as type A if < 0.5, type B if the ratio was between 0.50 and 0.75, and type C if the ratio was > 0.75.
Fracture type
Was evaluated according to AO/OTA classification [27].
Evaluation of reduction quality
Neck-shaft angle (NSA)
Was recorded as the angle measurement between the femoral neck and the diaphysis on early-zeroth or first day-postoperative plain radiographs after fixation [28].
Baumgaertner classification
Reduction quality was classified/typed as good (both 1 and 2 are met), acceptable (only 1 criterion is met) or poor (neither 1 nor 2 is met) using Baumgaertner criteria consisting of alignment and displacement in plain AP and lateral radiographs [29] (Table 1).
Table 1.
Reduction quality criteria of Baumgaertner classification
| Baumgaertner criteria | View | Radiographic measurement |
|---|---|---|
| Alignment | AP | Normal or slight valgus* neck-shaft angle |
| Lat | < 20o of angulation | |
| Displacement | AP | < 4 mm displacement of any fragments |
| Lat | > 4 mm displacement of any fragments |
AP Anteroposterior, Lat Lateral, mm Milimeter, o Degree
*Slight valgus means a valgus of no more than 10o
Reduction pattern
Divided into three types by considering the position of the proximal part relative to the distal part in plain AP and lateral radiographs [30] (Fig. 3).
Fig. 3.
Reduction pattern in plain anteroposterior and lateral radiographs, (a) Medial type; the proximal fragment is located medial to the anatomical location, (b) Anatomical type; the proximal fragment is precisely positioned in the anatomical location, (c) Lateral type; the proximal fragment is located lateral to the anatomical location, (d) Extramedullary type; the anterior cortex of the proximal fragment is located in front of the anterior cortex of the distal fragment, (e) Anatomical type; proximal fragment was reduced in the anatomical position while the anterior cortex of the proximal and distal fragments was in contact, (f) Intramedullary type; the anterior cortex of the proximal fragment was located at the rear of the anterior cortex of the distal fragment
Evaluation of fixation quality.
Tip-apex distance (TAD)
Was measured and recorded as the sum of the distances between the point where the midline axis of the femoral neck intersects the articular line of the femoral head and the tip of the implant in AP and lateral radiographs [31] (Fig. 4).
Fig. 4.
Schematic representation of tip-apex distance (TAD) and calcar referenced tip-apex distance (CalTAD) calculation on anteroposterior (a) and lateral radiographs (b). TAD=TADAp+TADLat, CalTAD=CalTADAp+CalTADLat. DTrue: The known actual diameter of the implant. DAp: Measured lag screw diameter in the AP radiograph
Calcar referenced tip-apex distance (CalTAD)
Unlike conventional TAD, uses the femoral calcar as a reference point, rather than the center of the femoral neck. CalTAD, was measured and recorded as the sum of the distances between the tip of the lag screw and the medial calcar in AP and lateral radiographs [8, 11] (Fig. 4).
Lag screw position
Was measured on plain AP and lateral radiographs using Parker’s ratio method [32]. In this measurement, 0-0.33 indicates inferior/posterior, 0.34–0.66 indicates central/central, and above 0.66 indicates superior/anterior position of lag screw (Fig. 5). Based on this measurement, the position of the lag screw in the femoral head was classified into zones using the Cleveland Bosworth system [33] (Fig. 6).
Fig. 5.
Parker’s ratio method (PRM); is the ratio of AB/AC in each plain anteroposterior (a) and lateral radiographs (b) [AC: femoral head equatorial diameter, A: inferior/posterior pole, C: superior/anterior pole, B: center of screw through AC line]
Fig. 6.
Lag screw position within the femoral head (%: The cutout ratio in each Cleveland Bosworth zone, *: Statistically significant zones for cutout)
Statistical analysis
Statistical analyses were performed using IBM SPSS Statistics Standard Concurrent User Version 27 (IBM Corp., Armonk, NY, USA). Descriptive statistics were presented as number of cases (n), percentage (%), mean ± standard deviation, median, minimum, and maximum values, as appropriate. The distribution of continuous variables was assessed using the Kolmogorov–Smirnov test together with graphical methods, and the homogeneity of variances was evaluated using Levene’s test. For comparisons between two independent groups, the independent samples t-test was applied for normally distributed variables, whereas the Mann–Whitney U test was used for non-normally distributed variables.
Categorical variables were compared using the Pearson chi-square test or Fisher’s exact test, depending on expected cell frequencies.
Receiver operating characteristic (ROC) curve analysis was conducted for parameters that demonstrated statistically significant differences between groups and were considered clinically relevant for predicting cutout development. For each parameter, the area under the curve (AUC), standard error, 95% confidence interval, sensitivity, specificity, and optimal cutoff values were calculated. The optimal cutoff points were determined based on the Youden index to achieve the best balance between sensitivity and specificity.
Binary logistic regression analysis was performed to evaluate the independent predictive effects of variables potentially associated with cutout development. Variables showing statistical significance in univariate analyses and those considered clinically relevant were included in the multivariable regression model. The strength of associations was expressed as odds ratios (OR = Exp β) with corresponding 95% confidence intervals. Statistical significance was defined as a p-value < 0.05 for all analyses.
Results
The retrospective review revealed 2543 patients diagnosed with and treated for AO/OTA Type 31 A1/A2 and A3 intertrochanteric femur fractures. After excluding patients who met the exclusion criteria, the remaining 371 patients were included in the study. The mean age of the patients was 78.8 ± 6.95 years (median 79; range 65–96 years), and 66% were female.
Patients were divided into two groups: those who developed a cutout (cutout group) and those who did not (non-cutout group). A cutout developed in 48 patients (12.9%). The mean time to cutout development was 6.29 ± 5.52 weeks (median 3.5; range 1–24 weeks). The mean time to bone union in the non-cutout group was 13.54 ± 3.38 weeks (median 14; range 6–24 weeks). The groups were similar in terms of age, gender, BMI, and CCI (for each, p > 0.05) (Table 2).
Table 2.
Demographic variables of groups
| Variable | Non-cutout Group (n = 323) |
Cutout Group (n = 48) |
Test value | p-value |
|---|---|---|---|---|
| Age* (years) |
78.68 ± 7.11 79 (65–96) |
79.83 ± 5.74 77.5 (73–94) |
0.685 | 0.493† |
|
Gender Male n (%) Female |
115 (35.6) 208 (64.4) |
11 (22.9) 37 (77.1) |
2.999 | 0.083& |
| CCI score* |
4.41 ± 1.09 4 (2–8) |
4.47 ± 0.96 4 (3–7) |
0.202 | 0.840† |
| BMI* |
25.41 ± 4.38 24 (14–41) |
26.02 ± 3.59 25.5 (19–39) |
1.409 | 0.159† |
n Number of patients, % Column percentage, CCI Charlson comorbidity index, BMI Body mass index
*: The data is presented as mean ± standard deviation and median (minimum-maximum)
†: Mann-Whitney U test, &: Chi-square analysis
Bone quality and morphology/type
Singh index was found to be significantly lower in the cutout group (2.56 ± 0.51 vs. 3.70 ± 0.67; p < 0.001). 47.9% of patients in the cutout group had Dorr type C femur morphology, and this rate was significantly higher compared to the non-cutout group (p < 0.001). No significant difference was observed in terms of cutout formation between AO/OTA fracture subtypes (p = 0.332) (Table 3).
Table 3.
Comparative analysis of predictive/risk factors for cutout
| Variables | Non-cutout Group (n = 323) |
Cutout Group (n = 48) |
Test value | p-value |
|---|---|---|---|---|
| A- Bone quality and type | ||||
| I- Singh index* |
3.70 ± 0.67 4 (2–5) |
2.56 ± 0.51 3 (2–3) |
9.304 | < 0.001 † |
| II- Dorr type n (%) | ||||
| A | 2 (0.6) a | 0 (0) a | 16.773 | < 0.001 ƞ |
| B # | 258 (79.9) a | 25 (52.1) b | ||
| C # | 63 (19.5) a | 23 (47.9) b | ||
| III- Fracture type (AO) n (%) | ||||
| A1.2 | 99 (30.7) | 8 (16.7) | 6.383 | 0.332 ƞ |
| A1.3 | 53 (16.4) | 7 (14.6) | ||
| A2.2 | 52 (16.1) | 10 (20.8) | ||
| A2.3 | 81 (25.1) | 18 (37.5) | ||
| A3.1 | 5 (1.5) | 0 (0) | ||
| A3.2 | 7 (2.2) | 1 (2.1) | ||
| A3.3 | 26 (8.0) | 4 (8.3) | ||
| B- Reduction quality | ||||
| I- NSA* (degree) |
131.76 ± 6.44 132 (115–150) |
126.60 ± 4.41 127 (116–134) |
5.284 | < 0.001 † |
| II- Reduction type n (%) | ||||
| Good # | 242 (74.9) a | 18 (37.5) b | 26.562 | < 0.001 ƞ |
| Acceptable # | 78 (24.2) a | 28 (58.3) b | ||
| Poor | 3 (0.9) a | 3 (4.2) a | ||
| IIIa- Reduction pattern AP n (%) | ||||
| Medial | 101 (31.3) a | 17 (35.4) a | 10.307 | 0.006 & |
| Anatomical # | 209 (64.7) a | 24 (50.0) b | ||
| Lateral # | 13 (4.0) a | 7 (14.6) b | ||
| IIIb- Reduction pattern Lat n (%) | ||||
| Extramedullary | 71 (22.0) a | 5 (10.4) a | 105.673 | < 0.001 & |
| Anatomical # | 217 (67.2) a | 8 (16.7) b | ||
| Intramedullary # | 35 (10.8) a | 35 (72.9) b | ||
| C- Fixation quality | ||||
| I- TAD* (mm) |
22.47 ± 7.42 22 (8–45) |
30.08 ± 9.46 28.5 (17–57) |
5.286 | < 0.001 † |
| II- CalTAD* (mm) |
25.07 ± 7.55 24 (10–48) |
33.08 ± 9.06 31.5 (18–60) |
5.752 | < 0.001 † |
| III- Cleveland zones n (%) | ||||
| Superior-Central | 5 (1.5) a | 1 (2.0) a | 28.186 | < 0.001 ƞ |
| Central-Anterior # | 26 (8.0) a | 17 (35.4) b | ||
| Central-Central # | 244 (75.6) a | 24 (50.0) b | ||
| Central-Posterior | 15 (4.7) a | 2 (4.2) a | ||
| Inferior-Anterior | 2 (0.6) a | 0 (0) a | ||
| Inferior-Central | 28 (8.7) a | 2 (4.2) a | ||
| Inferior-Posterior | 3 (0.9) a | 2 (4.2) a | ||
n Number of patients, % Column percentage, CCI Charlson comorbidity index, BMI Body mass index, NSA Neck–shaft angle, TAD Tip-apex distance, CalTAD Calcar referenced tip-apex distance, mm Millimeter, AP Anteroposterior, Lat Lateral
*: The data is presented as mean ± standard deviation and median (minimum-maximum)
# : The variables that cause the statistically significant difference. If both columns contain
†: Mann-Whitney U test
&: Chi-square analysis
ƞ: Fisher exact test
“a”, there is no difference; if one column contains “a” and the other contains “b”, then there is a difference
p-values reported in bold indicate statistical significance
Reduction quality
NSA was found to be lower in the cutout group, and this difference was statistically significant (126.6° vs. 131.7°; p < 0.001). This means that varus reduction and fixation were greater in the cutout group. According to the Baumgaertner classification, reduction quality was largely good (74.8%) in the non-cutout group. This rate decreased in the cutout group (37.5%), and the most common type was acceptable (58.3%). This change in reduction quality was significant (p < 0.001). Looking at the reduction pattern; according to AP radiographs, the reduction type distribution was significantly different in the cutout group (p = 0.006), and while anatomical reduction was decreased compared to the non-cutout group, lateral reduction was increased. There is also a significant difference in the evaluation based on lateral radiographs (p < 0.001), and while anatomical reduction was significantly reduced in the cutout group (16.7%), intramedullary reduction increased and became the most common type of reduction (72.9%) (Table 3).
Fixation quality
Among the fixation parameters, TAD (30.08 ± 9.46 mm) and CalTAD (33.08 ± 9.06 mm) were significantly higher in the cutout group (for each, p < 0.001).
Cleveland zone analysis showed that in the non-cutout group, screw position was most frequent in the center-center region (75.6%). This rate decreased in the cutout group (50%), and center-anterior placement increased significantly (35.4%). There was a statistically significant relationship between Cleveland zone distribution and the development of cutout (p < 0.001). When evaluated which zones were at higher risk, the center-anterior zone had a total of 43 patients in both groups, 17 of whom developed a cutout (17/43 = 39.5%). The cutout rate in all other zones was 9.5% (31/328). The center-anterior zone was significantly higher risk for cutout, and this was statistically significant (Odds ratio = 6.26, p < 0.001). In the center-center zone, there were a total of 268 patients in both groups, and only 24 of them developed a cutout (24/268 = 9%). The center-center zone was significantly lower risk for cutout (Odds ratio = 0.32, p < 0.001). Other zones were not significantly higher in terms of cutout risk (for each, p > 0.05). Although there was a percentage increase in the inferior-posterior zone (2/5 = 40%), it could not be statistically significant due to the small number of cases and insufficient data (Table 3; Fig. 6).
In the ROC analysis, the discriminative power of parameters that can be used to predict cutout development was evaluated. According to the analysis results, CaITAD was found to have the highest discriminative power (AUC = 0.757; 95% CI: 0.710–0.800; p < 0.001). The cutoff value calculated as 26.0 mm was found to be discriminative with 63.78% sensitivity and 75% specificity for cutout development (Fig. 7). The cutoff values for NSA and TAD were found to be 130 degrees and 23 mm, respectively, and both parameters had a significant relationship with cutout development (Table 4).
Fig. 7.
Receiver operating characteristic (ROC) curve diagram and area under the curve (AUC) (95% confidence interval) of calcar referenced tip-apex distance (CalTAD)
Table 4.
Receiver operating characteristics analysis; the optimal cutoff values of predictive parameters for the differentiation of cutout
| Variables | Cutoff | AUC | se | p | 95% CI | Sensitivity | Specificity | |
|---|---|---|---|---|---|---|---|---|
| Lower | Upper | |||||||
| NSA (degree) | 130.0 | 0.736 | 0.032 | < 0.001 | 0.688 | 0.780 | 56.35 | 79.17 |
| TAD (mm) | 23.0 | 0.736 | 0.035 | < 0.001 | 0.688 | 0.780 | 56.97 | 79.17 |
| CaITAD (mm) | 26.0 | 0.757 | 0.033 | < 0.001 | 0.710 | 0.800 | 63.78 | 75.0 |
NSA Neck–shaft angle, TAD Tip-apex distance, CalTAD Calcar referenced tip-apex distance, mm Millimeter, AUC Area under the curve, se Standard error, CI Confidence interval
In logistic regression analysis, the independent predictive power of parameters that may effect cutout development was evaluated. Model results showed that the Singh index and NSA were statistically significant independent predictors (p < 0.05). As the Singh index value increased, i.e., as bone quality improved, the probability of cutout development decreased significantly (β = -4.663; p < 0.001). Similarly, in terms of NSA, the probability of cutout was inversely related to the angle value; as the angle increased, the risk of cutout decreased significantly (β = -0.186; p = 0.020). The coefficients obtained for the other variables, TAD and CalTAD, did not reach the significance level (Table 5).
Table 5.
Logistic regression analysis; the independent predictive power of parameters that may affect cutout development
| Variables | β | se | Wald | p | Exp (β) | 95% CI | |
|---|---|---|---|---|---|---|---|
| Lower | Upper | ||||||
| Singh index | -4.663 | 0.943 | 24.430 | < 0.001 | 0.009 | 0.001 | 0.060 |
| NSA (degree) | -0.186 | 0.080 | 5.435 | 0.020 | 0.830 | 0.710 | 0.971 |
| TAD (mm) | 0.275 | 0.172 | 2.556 | 0.110 | 1.316 | 0.940 | 1.844 |
| CaITAD (mm) | -0.131 | 0.164 | 0.631 | 0.427 | 0.878 | 0.636 | 1.211 |
NSA Neck–shaft angle, TAD Tip-apex distance, CalTAD Calcar referenced tip-apex distance, mm Millimeter, β Statistical power, se Standard error, Exp (β) Odds ratio, CI Confidence Interval, Wald Maximum likelihood estimation
p-values reported in bold indicate statistical significance
Discussion
Despite technical advances in PFNs, cutout complications remain a serious problem, particularly in geriatric intertrochanteric femur fractures. In the present study, a cutout rate of 12.9% after PFN was observed, and 48 cutout cases, which can be considered a large series, were analyzed. This is quite important, because in most studies evaluating cutout risk factors in the current literature, the number of cutout cases analyzed is usually much lower [34, 35].
This limits statistical modeling of risk factors. Therefore, the present study, being methodologically conducted on a relatively large and homogeneous cohort, can contribute to a more detailed and reliable analysis of cutout predictors in geriatric patients.
The findings of this study reveal that the factors influencing cutout formation in geriatric intertrochanteric femur fractures are multifactorial, and it is evident that these factors are closely related to each other. These factors can be grouped under three main headings: bone quality and morphology, reduction quality, and fixation quality. When the subheadings were examined, osteoporosis grade (Singh index), bone morphology (Dorr type C), fixation of the femoral neck in varus position (NSA), deviation of the reduction type from the good criteria, lateral and intramedullary reduction patterns, and lag screw position parameters (increase in TAD and CalTAD and central-anterior position) were found to be important. However, although these factors showed significance in univariate analyses and were considered clinically relevant, only the NSA and Singh index were found to be significant as independent predictive factors in multivariate analyses. According to these results, it can be said that the most important/strongest independent predictor factors of cutout in geriatric patients are the osteoporosis grade and fixation of the femoral neck in varus position.
Bone quality and morphology/type
Are the most fundamental determinants that cannot be changed by the surgeon, and are associated with many factors such as age, gender, and comorbidity. In this study, there was no significant difference in age, gender, and CCI between patients who developed cutout and those who did not. This finding shows that age or comorbidity burden alone cannot explain cutout. Some studies in the literature consider female gender as an important risk factor for cutout [36, 37]. This may be due to differences in proximal femur geometry and bone strength in women compared to men, primarily due to differences in bone mineral density. Indeed, Xu et al. argued that advanced osteoporosis is a significant determinant of cutout risk and that hip arthroplasty may be a more appropriate treatment option in these patients [38]. In this study, the significantly lower Singh index in the cutout group clearly demonstrates the decisive role of osteoporotic bone in the development of cutout complication. The fact that the Singh index remained a strong independent predictor in the logistic regression analysis emphasizes the importance of this relationship. As the Singh index value decreases, i.e., as bone quality decreases and the severity of osteoporosis increases, the probability of developing a cutout increases significantly.
Turgut MC et al. stated that the Dorr type is an important parameter for predicting implant failure in proximal femoral fractures treated with PFN, and emphasized that the probability of early failure is high, especially in Dorr type C [39]. In the present series, the distribution of bone morphology differed significantly according to Dorr index, and the C-type femur morphology was particularly dominant in the cutout group. This finding may be explained by the biomechanical difficulty of achieving primary stability or adequate three-point fixation in Dorr type C femurs with a wide medullary canal. This situation may cause macro or micro movement in the nail, increasing the stress and load on the lag screw. Therefore, the risk of cutout may be higher in osteoporotic geriatric patients with Dorr type C morphology.
Another parameter that may be associated with cutout development is fracture type. In present study, no significant difference was found in terms of cutout development among fracture subtypes according to the AO/OTA classification. This finding indicates that fracture morphology alone is not sufficient to predict cutout development in geriatric patients.
Similarly, there are studies in the literature reporting that fracture type does not show an independent relationship with cutout [8, 15]. The lack of statistically significant difference in our study also reveals that other risk factors are much more decisive for cutout development in the geriatric patient group compared to fracture type.
Reduction quality
Is a critical factor that directly affects surgical success and also shapes the quality of fixation. The reduction criteria defined by Baumgaertner have been used in the literature for many years [40]. Among the patients included in this study, acceptable type reduction was more common in the cutout group (58.3%). Compared to the non-cutout group, there was a decrease in the good type reduction, and this difference was statistically significant. In the literature, it is generally accepted that poor reduction quality, according to the Baumgaertner classification, increases the risk of cutout, while good reduction quality significantly reduces this risk [41–43]. Moreover, a recent study by Kaya et al. evaluating intertrochanteric femur fracture surgery in older patients highlighted that patients with poor reduction quality had approximately ten times higher cutout risk compared to those with good reduction quality [44]. Therefore, one of the surgeon’s primary intraoperative goals should be to achieve good reduction quality. Considering that reduction quality is a variable that can be modified and controlled by the surgeon intraoperatively, the importance of reduction quality assessment systems in daily practice becomes even more apparent. Although the dominant reduction type in the cutout group in our study was acceptable, the progression to cutout reveals that Baumgaertner’s acceptable reduction category, in particular, may be controversial in terms of current clinical requirements. The displacement range of up to 4 mm included in the Baumgaertner criteria may be overly broad. Therefore, authors are forced to include disadvantageous reduction patterns in the acceptable category when using this classification.
Indeed, the lateral reduction pattern in AP radiographs and the intramedullary reduction pattern in lateral radiographs, which were statistically significantly higher in the cutout group in our study, are biomechanically quite unfavorable patterns, even though they must be classified as acceptable in the Baumgaertner classification. Because, in the relevant literature, the lateral type reduction pattern is called negative medial cortical support and the intramedullary reduction pattern is called negative anterior cortical support, and it has been stated that both of these reduction patterns are associated with mechanical failure in intertrochanteric fractures [14]. These data support our concern about the Baumgaertner classification.
Another important parameter used in evaluating the quality of reduction is NSA. Turgut et al. reported that NSA values below 130° (varus reduction) are the most decisive parameter for cutout, while Yam et al. reported that NSA below 128° is a significant predictor for cutout [28, 37]. In the current series, NSA values were found to be significantly lower in cases that developed cutout. The cutoff value determined for NSA is 130°, and the AUC value, which shows the diagnostic power of this value in predicting cutout development, was calculated as 0.736 (p < 0.001). This result shows that NSA is a parameter that can be used with high accuracy in predicting cutout risk. Furthermore, in the logistic regression analysis, NSA maintained its significance and was identified as an independent risk factor; it was determined that an increase in the angle value has a protective effect that decreases the risk of cutout. In light of all this data, it can be said that one of the most important risk factors for cutout is NSA. The surgeon should never forget that one of the most important intraoperative modifiable risk factors for geriatric patients is fixation in the varus position, and should work meticulously to obtain the optimal NSA value.
Fixation quality
Is assessed using TAD, CalTAD, and Cleveland zones, which indicate the position of the lag screw. These parameters are used as reference points to define the ideal screw position, and their correlation with the cutout complication is widely accepted [15, 34, 45]. TAD refers to the total distance from the screw tip to the apex of the femoral head, and it is recommended to be less than 25 mm [29]. However, TAD is only a parameter that evaluates the depth of the lag screw, not its direction. Therefore, two screws with the same TAD value can be in completely different positions within the femoral head [46]. Because of this weakness, it is argued that CalTAD, as defined by Kuzyk, provides more accurate information in predicting cutout development [11]. CalTAD differs from TAD only in the AP plane, and it measures according to a line as a reference that passes parallel to the neck but adjacent to the calcar (Fig. 4). There is still no consensus on the optimal cutoff value for CalTAD, and reported values range from 23.7 to 35.2 mm [47, 48]. In our study, ROC analysis showed cutoff values of 23 mm and 26 mm for TAD and CalTAD, respectively. The literature reports that individual anatomical differences and geometric variables lead to changes in optimal cutoff values from study to study [46, 47]. Garabano et al. stated that the CalTAD value was the parameter that provided the highest sensitivity (100%) and specificity (82.9%) for cutout, and they determined that the cutoff value was 24.95 mm. Furthermore, they stated that this value was the only independent variable associated with cutout and that being above this cutoff value increased the risk of cutout by 24 times [15]. Our study data show that CalTAD is a more reliable indicator than TAD (AUCs of 0.757 and 0.736, respectively), but both parameters are significantly associated with cutout development.
According to these data, both can be used with high accuracy in predicting cutout development. One of the surgeon’s main goals during the intraoperative process should be to obtain optimal cutoff values for TAD and CalTAD. Because these values, just like the NSA, are key factors that determine the intraoperative decision-making process. However, both parameters lost their significance in logistic regression analysis. This indicates that the effect of these variables decreases when evaluated together with other factors, and they are not sufficient to independently predict cutout development alone. However, this should not be interpreted as meaning that TAD and CalTAD are clinically insignificant, secondary or negligible, as these parameters are modifiable intraoperative factors and are extremely important from a practical surgical perspective.
The Cleveland zone diagram, showing the distribution of screw position areas, evaluates the three-dimensional localization of implant, and thus provides a critical reference for the cutout complication. Screw position, just like TAD and CalTAD, is extremely important in surgical practice and is an important technical risk factor that can be modified intraoperatively. There is no complete consensus in the literature regarding which zone significantly increases the risk of cutout [28, 37, 43, 49, 50]. Some studies suggest that the inferior-posterior zone may be protective, while others report that the posterior zone increases the risk of insufficiency [28, 37, 43]. Caruso et al. stated that the risk of cutout is high in other zones, which they call the peripheral zone, outside the center-center zone [49]. In a biomechanical study, Kane et al. showed that inferior-center position with TAD greater than 25 mm provides equal or greater stability than center-center position with TAD less than 25 mm [50].
The center-center zone localization was identified in 75.6% of the non-cutout group and 50% of the cutout group in the present study.The center-anterior zone localization in the cutout group, the rate increased significantly compared to the non-cutout group, rising from 8% to 35.4%, and this change was statistically significant. According to the risk analysis performed, the center-anterior zone localization was associated with a significantly higher risk of cutout, while the center-center zone localization appeared protective with a lower cutout rate. The differences in cutout rates in other zones were not statistically significant, but some of these zones had a limited number of patients. According to these results of the present study, it can be said that the most risk zone for cutout in geriatric intertrochanteric femur fractures treated with PFN is the center-anterior localization. The surgeon should not be reassured solely by a centrally located lag screw on intraoperative fluoroscopic AP images. The anteversion of the lag screw must be carefully evaluated using a lateral view, and it must be absolutely certain that it is not in an anterior localization. Because central-anterior zone localization is a very high-risk position for cutout complication in osteoporotic geriatric patients.
This study has some limitations. Due to its retrospective design, the assurance of completeness and homogeneity of clinical and radiological data is limited; furthermore, it was not possible to fully control for potential confounding variables. Another limitation is that bone quality is assessed using the Singh index. This method may involve difficulty in distinguishing between osteoporosis grades and may show observer-dependent variability.
Given the observer-dependent variable nature of the Singh index, this inherent subjectivity is a potential limiting factor on the robustness of the findings. Therefore, the failure to use a more objective evaluation method such as DEXA is a methodological limitation. In addition, the failure to assess inter- and intra-observer agreement in radiological measurements prevented the exclusion of potential differences in measurements. This can be considered a significant limitation, because many of the potential risk factors we evaluate to determine cutout risk-such as the Singh index, Dorr type, Baumgaertner classification, reduction pattern, and Cleveland zones-are important factors that may be subject to observer variability.
However, this limitation was minimized by having all radiological evaluations performed by an independent team consisting of two orthopedic specialists and one radiology specialist who were not involved in the initial planning or surgery to prevent potential bias, and by making all decisions by consensus. The exclusion of patients who underwent secondary surgery due to infection or major surgical complications can be considered another limitation of the study. Because this situation can lead to the exclusion of individuals at high risk of mechanical failure, and thus to selection bias. However, this is a conscious methodological choice. In fact, this choice can be considered a strong point. Because the study aimed to isolate the determinants of cutout risk and create a homogeneous cohort. Likewise, while restricting the sample to a single implant design may increase internal consistency, it may also limit generalizability. Therefore, caution should be exercised regarding the applicability of the study’s results to all geriatric intertrochanteric femur fractures treated with other types of implants. Another limitation was that some Cleveland zones included a limited number of patients. This is due to the retrospective design of the study and the surgeon’s desire to capture the ideal intraoperative screw position. Therefore, analyses based on all subgroups could not be clearly performed in terms of cutout risk. However, the fact that our study was conducted on as homogeneous a cohort as possible, the large sample size, and the support of the findings with ROC and binary logistic regression analyses stand out as important strengths that increase the clinical reliability and generalizability of the results.
Conclusion
In conclusion, the findings reveal that the factors influencing cutout formation are multidimensional. Therefore, the most effective approach to preventing cutout complications, especially in geriatric/high-risk patients, is to accurately assess bone quality, obtain biomechanically advantageous reduction patterns, and meticulously ensure optimal implant positioning. Although cutout development is multifactorial, it should be remembered that the main independent predictors for cutout of geriatric intertrochanteric femur fractures are osteoporosis grade and fixation in varus position. The surgeon should always carefully examine these two parameters, especially the degree of osteoporosis.
This study presents one of the largest cutout series in the literature, providing strong evidence based on multivariate analysis of risk factors and making a significant contribution to clinical decision-making. Further studies with prospective and standardized measurements are important for confirming these findings and further developing treatment algorithms.
Acknowledgements
Not applicable.
Abbreviations
- AO/OTA
Arbeitsgemeinschaft für Osteosynthesefragen / Orthopaedic Trauma Association
- AP
Anteroposterior
- APFN
Antirotator proximal femoral nail
- AUC
Area under the curve
- BMI
Body mass index
- CalTAD
Calcar referenced tip–apex distance
- CAS
Cumulative ambulatory score
- CCI
Charlson comorbidity index
- CI
Confidence interval
- NSA
Neck–shaft angle
- OR
Odds ratio
- PACS
Picture archiving and communication system
- PFN
Proximal femoral nail
- ROC
Receiver operating characteristic
- TAD
Tip–apex distance
Authors' contributions
YO: Conceptualization, methodology, investigation, data collection, formal analysis, writing-original draft, writing-review and editing.TB: Investigation, data collection, writing-review and editing. TK, MB and MT: Writing-review and editing.
Funding
The authors received no specific funding for this work.
Data availability
The datasets generated and/or analyzed during the current study are not publicly available due to institutional and privacy restrictions, but are available from the corresponding author on reasonable request.
Declarations
Ethics approval and consent to participate
All procedures involving human participants were performed in accordance with the ethical standards of the institutional committee and the 1964 Helsinki Declaration and its later amendments. This retrospective study was approved by the Institutional Review Board of (IRB#716/2025). Due to the retrospective nature of the study, the requirement for informed consent was waived by the Ethics Committee.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The datasets generated and/or analyzed during the current study are not publicly available due to institutional and privacy restrictions, but are available from the corresponding author on reasonable request.