Trochanteric fractures of the femur constitute a major proportion of orthopedic trauma worldwide and represent a significant cause of morbidity, mortality, and healthcare burden, particularly among the elderly population. With the progressive increase in life expectancy and the growing prevalence of osteoporosis, the incidence of trochanteric fractures continues to rise globally. These fractures most commonly result from low-energy trauma such as trivial falls in elderly osteoporotic individuals, whereas high-energy trauma remains the predominant mechanism in younger patients. Several associated risk factors have been identified, including osteoporosis, recurrent falls related to dementia, Parkinson’s disease, impaired vision, unsteady gait, and underlying neuromuscular disorders, all of which contribute to increased fracture susceptibility and poorer functional outcomes [1,2]. The surgical management of trochanteric fractures depends largely on fracture stability. Stable fracture patterns are typically managed using sliding hip screw systems, while unstable fractures are preferably treated with cephalomedullary nails, which offer biomechanical advantages by reducing the bending moment, controlling varus collapse, and allowing early mobilization. Despite advancements in implant design and surgical techniques, implant-related complications continue to pose significant challenges, with lag screw cut-out remaining one of the most commonly reported causes of fixation failure. The risk of screw cut-out is multifactorial and is influenced by fracture configuration, bone quality, adequacy of fracture reduction, and, most importantly, the position of the lag screw within the femoral head [3–5]. In an effort to optimize screw placement and minimize cut-out risk, Baumgaertner and colleagues introduced the concept of the Tip-to-Apex Distance (TAD) in 1995 as a quantitative radiographic parameter. TAD is calculated by summing the distance from the tip of the lag screw to the apex of the femoral head on both anteroposterior and lateral radiographs, corrected for radiographic magnification. Their study demonstrated that a TAD value of less than 25 mm was associated with a significantly reduced incidence of screw cut-out, making it a widely accepted guideline in clinical practice [6]. Subsequently, Kuzyk et al. proposed the calcar-referenced Tip-to-Apex Distance (CalTAD), which emphasizes inferior-central placement of the lag screw in the femoral head to achieve improved purchase in the denser calcar bone, particularly in osteoporotic patients. Additionally, biomechanical concerns have been raised regarding excessive load transmission to the derotation screw, with some studies suggesting that derotation screw length may play a crucial role in implant perforation, especially in biaxial proximal femoral nail constructs [7,8]. However, more recent studies have challenged the absolute predictive value of both TAD and CalTAD, suggesting that quality of fracture reduction and overall fracture stability may be equally, if not more, important determinants of implant survival [9,10]. The trochanteric region of the femur comprises two prominent bony projections that serve as essential attachment sites for major hip musculature and play a critical role in hip biomechanics and gait. The greater trochanter is a large quadrilateral prominence located on the lateral aspect of the proximal femur just distal to the femoral neck and serves as the insertion site for the gluteus medius, gluteus minimus, obturator internus, piriformis, and obturator externus muscles, all of which contribute to hip abduction, rotation, and pelvic stabilization during ambulation. The lesser trochanter, situated on the posteromedial aspect of the femur, provides attachment for the iliopsoas muscle, the primary flexor of the hip joint. Integrity of the lesser trochanter and the postero-medial cortical buttress is critical for maintaining fracture stability, and its disruption is often associated with unstable fracture patterns [11]. Radiological evaluation of trochanteric fractures begins with an anteroposterior pelvis with both hips view to assess fracture configuration, compare the injured side with the contralateral hip, and evaluate the neck-shaft angle. A dedicated anteroposterior hip view helps delineate the fracture pattern more clearly, while a cross-table lateral view is essential for assessing posterior cortical comminution. A full-length femur radiograph is recommended to evaluate subtrochanteric extension, rule out pathological fractures, assess femoral bowing, determine canal diameter, and estimate the appropriate length of the intramedullary nail. Advanced imaging modalities such as computed tomography or magnetic resonance imaging may be required in cases of occult fractures or equivocal radiographic findings [12]. Several classification systems have been developed to categorize intertrochanteric fractures and guide management. The Tronzo classification categorizes fractures based on displacement and stability, ranging from stable nondisplaced fractures to highly unstable fractures with severe comminution or reverse obliquity, thereby assisting in predicting fracture stability and implant selection [13]. Evans classified intertrochanteric fractures into stable and unstable types based on the integrity of the postero-medial cortex, emphasizing that restoration of the medial cortical buttress after reduction is critical for stability [14]. The AO/OTA classification system further stratifies these fractures into 31-A1 (simple, stable), 31-A2 (multifragmentary, unstable), and 31-A3 (reverse obliquity or transverse fractures extending into the subtrochanteric region), and is widely accepted due to its reproducibility and relevance in guiding treatment decisions [15]. Postoperative complications following trochanteric fracture fixation most commonly occur within the first four months after surgery. Implant failure and lag screw cut-out are the most frequently encountered complications, particularly in elderly osteoporotic patients with unstable fracture patterns or suboptimal reduction. Other reported complications include non-union, malunion, peri-implant fractures, anterior perforation of the distal femur, fat embolism syndrome, and postoperative anemia, all of which contribute to prolonged hospital stay and increased morbidity [5,16]. The aim of this study is to evaluate and compare the predictive value of Tip Apex Distance (TAD) and Calcar-Referenced Tip Apex Distance (CalTAD) in determining osteosynthesis failure in patients with intertrochanteric and pertrochanteric femoral fractures treated surgically. The primary objective is to assess the association of TAD and CalTAD measurements with implant failure outcomes, particularly lag screw cut-out, in patients undergoing fixation with cephalomedullary devices. Secondary objectives include analyzing the relationship between osteosynthesis failure and fracture pattern, quality of fracture reduction, bone quality, implant position, and other radiological parameters, as well as determining the optimal threshold values of TAD and CalTAD for predicting failure. The findings of this study are expected to clarify the relative clinical utility of TAD and CalTAD as predictors of fixation failure and may contribute to refining intraoperative decision-making and implant positioning strategies. In the future, these results may aid in the development of standardized radiological guidelines, improve surgical outcomes by reducing implant failure rates, and serve as a foundation for larger multicenter studies aimed at establishing evidence-based protocols for fixation of intertrochanteric and pertrochanteric fractures.

This retrospective observational study was conducted on consecutive patients presenting with intertrochanteric and pertrochanteric fractures of the femur who were treated with closed reduction and internal fixation using a proximal femoral nail (PFN). The study included patients admitted to the Department of Orthopaedics, Dhiraj General Hospital, between November 2022 and 30 June 2023. Institutional records were reviewed to identify eligible cases. Only patients who had undergone fixation with a short proximal femoral nail and had a minimum radiological follow-up of 90 days were included in the analysis. Surgical Technique All surgeries were performed with the patient positioned supine on a fracture table under spinal or epidural anesthesia, with the trunk slightly deviated to the contralateral side to facilitate surgical access. Closed reduction of the fracture was achieved under fluoroscopic guidance in 65 patients, while joystick-assisted reduction maneuvers were required in 2 patients to obtain acceptable alignment. A longitudinal skin incision of approximately 3 cm was made 2 cm proximal to the tip of the greater trochanter, parallel to the femoral shaft. A guide wire was inserted through the trochanteric tip and advanced across the fracture site into the femoral canal under image intensifier control. The proximal femur was reamed to a diameter of 15 mm, following which a short proximal femoral nail was inserted after mounting it on a radiopaque 135° targeting jig. Proximal fixation was achieved using one lag screw and one anti-rotation (AR) screw, while distal locking was performed with a single static locking bolt in all cases, irrespective of fracture configuration. The choice of short PFN was based on ease of insertion, reduced operative time, and lower risk of distal femoral complications. Radiological Assessment Postoperative radiographs were obtained immediately after surgery, at 45 days, and at 90 days follow-up. Radiological parameters, including Tip Apex Distance (TAD) and Calcar-referenced Tip Apex Distance (CalTAD), were measured using an in-house picture archiving and communication system (PACS) software. Measurements were performed on standardized radiographs comprising an anteroposterior view of the pelvis and affected limb with 15° internal rotation and a cross-table lateral view with the contralateral limb flexed and abducted. To assess the role of anti-rotation screw length, a three-zone classification system was used based on the position of the AR screw tip on the anteroposterior radiograph. AR screws were classified as Zone 1 if they crossed an imaginary line drawn between the proximal end of the nail and the tip of the lag screw, Zone 3 if the screw did not reach the junction between the femoral head and neck, and Zone 2 for intermediate positions. This classification was used to objectively evaluate the influence of AR screw length and position on implant failure. Data Collection and Outcome Assessment For each patient, demographic and perioperative data were collected, including age, gender, type of anesthesia, duration of surgery, length of hospital stay, postoperative complications, mortality, and incidence of lag screw cut-out. Radiological outcomes were assessed during follow-up visits, with special emphasis on osteosynthesis failure, defined as lag screw cut-out or mechanical failure requiring revision surgery. All measurements of TAD and CalTAD were performed by a single observer to eliminate inter-observer variability. The primary outcome of the study was the occurrence of lag screw cut-out, while secondary outcomes included the association of cut-out with TAD, CalTAD, fracture pattern, and AR screw position. Figure 1: Radiographic measurements of TAD and CalTAD performed on the anteroposterior(a) and lateral (b)view of the final postoperative x-ray (a) (b) Table 1. Demographic and Clinical Profile of Patients with Intertrochanteric Fractures (n = 67) Variable Category Frequency (n) Percentage (%) Age (years) Mean ± Range 75.21 (48–92) — Gender Male 24 35.8 Female 43 64.2 Side of fracture Right 37 55.2 Left 30 44.8 Radiological follow-up Duration 3–6 months — Table 2. Fracture Characteristics According to AO Classification and Stability (n = 67) Variable Category Frequency (n) Percentage (%) AO Classification A1 40 59.7 A2 8 11.9 A3 19 28.4 Fracture stability Stable 48 71.6 Unstable 19 28.4 Table 3. Incidence of Cut-out and Association with Demographic and Fracture Variables (n = 67) Variable Category Cut-out Present (n = 10) Cut-out Absent (n = 57) p-value Age (years) Mean 74.6 75.3 NS Gender Male 4 (40.0%) 20 (35.1%) NS Female 6 (60.0%) 37 (64.9%) Side of fracture Right 6 (60.0%) 31 (54.4%) NS Left 4 (40.0%) 26 (45.6%) AO Classification A1 3 (30.0%) 37 (64.9%) — A2 1 (10.0%) 7 (12.3%) A3 6 (60.0%) 13 (22.8%) NS – Not statistically significant Table 4. Association of TAD and CalTAD with Osteosynthesis Failure (Cut-out) (n = 67) Radiological Parameter Category Cut-out Present (n = 10) Cut-out Absent (n = 57) χ² value p-value TAD ≤ 25 mm 2 (20.0%) 55 (96.5%) 4.6 0.032* > 25 mm 8 (80.0%) 2 (3.5%) CalTAD ≤ 25 mm 1 (10.0%) 54 (94.7%) 11.2 <0.001* > 25 mm 9 (90.0%) 3 (5.3%) *Statistically significant Figure 1: Comparative Distribution of Cut-Outs: TAD vs CalTAD The combined comparative graph demonstrates a clearer separation of cut-out events when Calcar-Referenced Tip–Apex Distance (CalTAD) is used compared to conventional Tip–Apex Distance (TAD). While both parameters showed an increased number of cut-outs when values exceeded 25 mm, the contrast between low-risk and high-risk categories was more distinct for CalTAD, supporting its superior predictive value for osteosynthesis failure. Figure 2: ROC Curve for Prediction of Cut- Out Receiver operating characteristic (ROC) curve analysis was performed to compare the predictive accuracy of Tip–Apex Distance (TAD) and Calcar-Referenced Tip–Apex Distance (CalTAD) for implant cut-out. The area under the curve (AUC) for CalTAD was higher than that for TAD, indicating superior diagnostic performance of CalTAD in predicting cut-out. This finding suggests that CalTAD is a more reliable radiological parameter for assessing the risk of osteosynthesis failure in intertrochanteric fractures treated with biaxial cephalomedullary nailing.

A total of 67 patients with 67 intertrochanteric fractures were included in the study. The mean age of the study population was 75.21 years, with the youngest patient aged 48 years and the oldest 92 years. There was a clear female predominance, with 43 females (64.2%) and 24 males (35.8%). Regarding laterality, 37 patients (55.2%) sustained fractures on the right side, while 30 patients (44.8%) had left-sided fractures. The mean radiological follow-up duration ranged between 3 and 6 months, with a mean follow-up of approximately 3.5 months in patients who developed cut-out. Based on the AO/OTA classification, the majority of fractures were classified as A1 (40 fractures, 59.7%), followed by A3 fractures (19 fractures, 28.4%), and A2 fractures (8 fractures, 11.9%). With respect to fracture stability, 48 fractures (71.6%) were considered stable, while 19 fractures (28.4%) were classified as unstable. Unstable fracture patterns were more frequently associated with mechanical complications. A total of 10 cut-outs (15.0%) were observed during the follow-up period. Comparison between patients with and without cut-out revealed that age, gender, and side of fracture did not show any statistically significant association with implant failure. Among patients with cut-out, 6 patients (60.0%) were female and 4 patients (40.0%) were male. Right-sided fractures accounted for 6 cases (60.0%), while 4 cases (40.0%) involved the left side. Cut-out was more commonly observed in AO type A3 fractures (6 cases, 60.0%), compared to A1 fractures (3 cases, 30.0%) and A2 fractures (1 case, 10.0%), and was predominantly seen in unstable fractures (8 out of 10 cases, 80.0%). Radiological analysis demonstrated a significant association between screw position parameters and osteosynthesis failure. When Tip Apex Distance (TAD) was analyzed, 8 out of 10 cut-outs (80.0%) occurred in patients with TAD >25 mm, compared to only 2 cut-outs (20.0%) in patients with TAD ≤25 mm, and this association was statistically significant (p = 0.032). However, Calcar-referenced Tip Apex Distance (CalTAD) showed an even stronger association with cut-out. Nine out of 10 cut-outs (90.0%) were observed in patients with CalTAD >25 mm, whereas only one patient (10.0%) with CalTAD ≤25 mm developed cut-out. This association was found to be highly statistically significant (p < 0.001), indicating that CalTAD was a superior predictor of osteosynthesis failure compared to conventional TAD in this cohort. Overall, the results indicate that while demographic factors did not significantly influence implant failure, fracture instability, AO type A3 fractures, and increased CalTAD values were strongly associated with cut-out. Among the radiological parameters evaluated, CalTAD demonstrated better predictive accuracy than TAD for osteosynthesis failure in intertrochanteric fractures treated with cephalomedullary nailing.

In this study of 67 intertrochanteric fractures treated with a short proximal femoral nail, the cohort was predominantly elderly (mean age 75.21 years; range 48–92) with a clear female preponderance (64.2%), which matches the well-known epidemiology of fragility hip fractures driven by osteoporosis and fall risk in older adults [1,2]. The distribution of AO types in this study—A1: 59.7%, A2: 11.9%, A3: 28.4%—and the predominance of stable fractures (71.6%) reflect a typical operative intertrochanteric fracture mix, where both stable and unstable patterns are increasingly managed surgically to enable early mobilization and reduce complication burden [4]. Although classic debates exist regarding the choice between sliding hip screw and cephalomedullary (CM) nailing, broader evidence shows that outcomes are often comparable for many extracapsular fracture patterns, yet CM nails are increasingly favored in contemporary practice—particularly for unstable patterns—due to perceived biomechanical advantages and ease in certain fracture configurations [3,4]. A key clinical outcome in this study was a cut-out incidence of 15% (10/67), occurring at a mean follow-up of around 3.5 months, which falls within the recognized early postoperative period when mechanical failures typically manifest. Cut-out remains one of the most important modes of fixation failure in peritrochanteric fracture surgery, and multiple reports have consistently emphasized that failure is multifactorial—driven by fracture instability, bone quality, reduction quality, and implant position [5]. In this study, demographic variables such as age, sex, and side of fracture were not statistically different between the cut-out and non–cut-out groups, which is consistent with the concept that mechanical and technical factors outweigh demographic factors once an elderly osteoporotic population is already established [5]. Importantly, the cut-out events clustered in mechanically unfavorable patterns: A3 fractures contributed 60% of cut-outs (6/10), and unstable fractures accounted for 80% (8/10), supporting the established view that instability and posteromedial compromise predispose to varus collapse and implant failure when fixation and biomechanics are suboptimal [5,14,15]. The central objective of this study was to assess screw position predictors of failure, particularly Tip–Apex Distance (TAD) versus Calcar-referenced TAD (CalTAD). Baumgaertner et al. originally demonstrated that TAD <25 mm markedly reduces cut-out risk and remains one of the most cited technical guidelines for peritrochanteric fixation [6]. In this study, TAD retained statistical relevance—80% of cut-outs occurred with TAD >25 mm (8/10), and the association was significant (p = 0.032)—supporting the foundational principle that excessive tip–apex distance increases failure risk [6]. However, a critical limitation of relying solely on TAD is that it may not fully capture the biomechanical advantage of inferior–central placement in osteoporotic femoral heads, particularly when the screw is intentionally positioned nearer the calcar to improve purchase and reduce rotational instability. This conflict has been described in later work where cut-out remains low despite “higher” TAD values when the screw is placed inferiorly, suggesting that location within the head matters as much as—or more than—the absolute distance metric [9,10]. This is where CalTAD becomes clinically meaningful. Kuzyk et al. emphasized that inferior placement of the lag screw enhances construct stiffness and purchase, providing biomechanical rationale for calcar-oriented positioning [7]. In this study, CalTAD showed a stronger and more clinically discriminating association with cut-out than TAD: 90% of cut-outs had CalTAD >25 mm (9/10), with a highly significant association (p < 0.001). This finding supports the practical argument that CalTAD may better reflect “safe” inferior-central screw positioning than conventional TAD, particularly in cephalomedullary constructs. The implication is that a calcar-referenced metric aligns more closely with the biomechanical goal of engaging denser inferior femoral head bone, which is consistent with biomechanical reasoning and finite-element/construct-stiffness observations favoring inferior positioning [7]. The observation in this study—that CalTAD appears more predictive than TAD—also aligns with reports challenging the universal applicability of a strict TAD >25 mm threshold, particularly when surgeons deliberately position the screw inferiorly to reduce rotational failure and cut-out. Several clinical and outcome studies have highlighted that failures can occur even with “acceptable” TAD if reduction is poor, while some cases remain stable despite higher TAD if the screw is optimally positioned and reduction is sound, reinforcing that screw position metrics should be interpreted alongside reduction quality and fracture stability [9,10]. Therefore, while the original Baumgaertner threshold remains a valuable intraoperative target, this study supports that CalTAD may be the more practical predictor when inferior-central placement is intended, especially in osteoporotic and unstable patterns where purchase and rotational control are paramount [6,7]. With regard to implant design concepts, cephalomedullary systems are often discussed as monoaxial versus biaxial constructs and the theoretical influence of additional anti-rotation elements on stability and cut-through or perforation. Although biomechanical investigations have explored how implant design and head element configuration affect stress distribution and fixation behavior, robust clinical evidence linking anti-rotation element length alone to failure remains limited. In this study, anti-rotation screw length/zone classification did not emerge as a reliable predictor of failure, suggesting that in this elderly osteoporotic population, factors such as bone quality, fracture instability, and lag screw purchase and positioning likely dominate the failure pathway. This interpretation is consistent with the broader literature emphasizing that mechanical failure is most strongly associated with construct positioning and stability rather than a single isolated implant measurement [5,9,10]. Overall, the findings of this study reinforce three clinically actionable points. First, cut-out remains concentrated in unstable and A3 fracture patterns, highlighting the need for meticulous reduction and optimal fixation strategy selection in these subgroups [5,14,15]. Second, while TAD >25 mm remains associated with failure and should not be ignored, CalTAD demonstrated superior predictive strength in this cohort, supporting calcar-oriented positioning principles [6,7]. Third, isolated anti-rotation screw length did not appear to independently predict failure in this dataset, and larger prospective studies incorporating reduction quality grading and bone density assessment may better clarify its role, if any, in real-world failure mechanisms [5,10,16].

This study evaluated predictors of osteosynthesis failure in intertrochanteric and pertrochanteric fractures treated with biaxial cephalomedullary nailing, with particular emphasis on Tip–Apex Distance (TAD) and Calcar-Referenced Tip–Apex Distance (CalTAD). The overall cut-out rate of 15% occurred predominantly in unstable fracture patterns and AO type A3 fractures, highlighting the critical role of fracture stability in mechanical failure. While increased TAD remained significantly associated with cut-out, CalTAD demonstrated a stronger and more consistent association with osteosynthesis failure. These findings suggest that CalTAD is a more reliable radiological predictor of cut-out than conventional TAD in biaxial cephalomedullary nail constructs, as it better reflects inferior-central lag screw placement within the femoral head. In contrast, anti-rotation screw length did not show a significant association with implant failure in this cohort. Overall, the study supports the clinical utility of CalTAD as a superior predictor of cut-out and emphasizes the importance of optimal screw positioning and fracture reduction in preventing fixation failure. Limitations This study has several limitations. Its retrospective design may introduce selection and information bias, and the relatively small sample size limited the statistical power for subgroup analyses. A substantial number of patients were excluded due to inadequate follow-up, which can be attributed to the advanced age of the study population and poor compliance with long-term follow-up. Bone quality was not objectively assessed using dual-energy X-ray absorptiometry or similar measures, despite osteoporosis being a major contributor to implant failure in elderly patients. Additionally, reduction quality was not graded using standardized scoring systems, and long-term functional outcomes were not evaluated. These factors may have influenced the observed outcomes and should be addressed in future studies. Recommendations Based on the findings of this study, meticulous attention should be given to inferior-central placement of the lag screw during cephalomedullary nailing, with greater emphasis on achieving an optimal CalTAD rather than relying solely on conventional TAD thresholds. Surgeons should be particularly cautious in unstable and AO type A3 fractures, where the risk of cut-out is highest. Routine intraoperative assessment of CalTAD may aid in improving fixation outcomes in biaxial cephalomedullary constructs. Future research should include larger, prospective, multicenter studies with standardized assessment of reduction quality, objective evaluation of bone density, and longer follow-up to validate the predictive value of CalTAD and further explore the biomechanical role of anti-rotation screw parameters.

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