Comparison between Proximal Femur Nail (PFN) and Dynamic Hip Screw (DHS) in Non-Displaced or Minimally Displaced Intertrochanteric Fractures of the Femur: Prospective Study

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Introduction

Over recent years, the application of the Proximal Femoral Nail (PFN) in managing intertrochanteric fractures (ITF) has seen notable growth, largely attributed to improvements in implant engineering and refinements in surgical techniques. PFN has emerged as a preferred fixation method due to multiple advantages, including decreased intraoperative blood loss, quicker implantation, facilitation of early mobilization, and minimal postoperative limb shortening (1).

From a biomechanical perspective, PFN's design ensures proximity to the mechanical axis of the lower limb, effectively shortening the lever arm and diminishing the bending forces exerted on the implant. This configuration not only enhances load distribution but also mitigates collapse and reduces tensile stress, collectively lowering the risk of implant failure. Furthermore, PFN provides stable three-point fixation with controlled axial impaction, promoting fracture stability and improved clinical outcomes (2).

A recognized technical challenge associated with Proximal Femoral Nail (PFN) fixation is the so-called “wedge effect,” characterized by distraction at the fracture site during nail insertion. This phenomenon can result in lateral displacement of the FS and varus malalignment of the femoral neck (3). It typically arises when the proximal femoral canal has not been sufficiently reamed to accommodate the broader cephalomedullary portion of the PFN. In contrast, the Dynamic Hip Screw (DHS) is generally indicated for stable intertrochanteric fractures where the medial buttress remains intact. Its use is contraindicated in cases with unstable fracture configurations, reverse obliquity patterns, significant osteoporotic changes, or a compromised lateral femoral wall thickness of less than 20.5 mm (4) (5). As a surface-based fixation system, DHS is biomechanically less likely to contribute to intraoperative fracture displacement (6).

This study hypothesizes that PFN may occasionally cause iatrogenic displacement of non-displaced or minimally displaced ITF more frequently than DHS. Hence, this study aims to quantify the degree of fracture displacement after fixation with DHS versus PFN in cases of non-displaced or minimally displaced intertrochanteric femur fracture.

Materials and methods

Design and population:

This prospective study was performed on 40 cases at XXXXX University Hospitals from January 2024 to June 2024 to quantify the degree of fracture displacement after fixation with DHS versus PFN in cases of non-displaced or minimally displaced intertrochanteric femur fracture. Approval was obtained from the Research and Ethics Committee of XXXXX University (XXXXXXX; approval number XXXXXXX). Informed consent was secured from all cases prior to surgery.

Grouping

Forty cases were divided into two equal groups: DHS Group and PFN Group.

Eligibility Criteria

Patients were eligible for inclusion if they had minimally displaced (<5 mm) or non-displaced intertrochanteric fractures classified as AO Type 31-A1 (subtypes 1.1, 1.2, and 1.3). Exclusion criteria included open fractures, prior surgeries on the ipsilateral or contralateral hip, non-ambulatory status, and pathological fractures due to malignant disease.

All patients underwent comprehensive preoperative evaluation, including detailed history, general and local physical examination, and radiological assessment with anteroposterior and lateral hip radiographs. The femoral NSA was measured as part of the radiographic analysis.

Post-operative: Prevention of infection, analgesia and anticoagulation.

Radiological assessment

Postoperative evaluation included immediate anteroposterior (AP) and lateral radiographs of the hip. The femoral NSA was determined according to the methodology described by Boese and colleagues (7). This angle was calculated between the axis of the femoral neck and the anatomical axis of the FS. The neck axis was drawn from the center of the femoral head (HC) to the center of the neck (NC), the latter defined as the midpoint between points where a circle (centered on the HC) intersected the superior and inferior borders of the femoral neck. The shaft axis was established by connecting central points identified at both proximal and distal segments of the femoral diaphysis (8). The tip–apex distance (TAD) was calculated as the cumulative length from the screw tip to the apex of the femoral head as seen on both the AP and lateral projections (9). FS lateralization was assessed by measuring the horizontal distance from the femoral head center to a reference line parallel to the lateral cortex of the femur, comparing the injured side with the contralateral uninjured side (4). Figure 1

 

Figure 1: (A) The measurement method of neck-shaft angle on upright pelvis plain radiograph. HC, femoral head center; NC, femoral neck center. (B) Calculation of the wedge effect (Net Lateralization of the shaft compared to the head/neck segment) Line [B] represents the distance from the center of the femoral head [C] to the lateral femoral shaft [A].

Quality of reduction

A score out of 4 was used to quantify the quality of fracture reduction depending on radiological findings. Score 4 is Excellent reduction, 2-3 is acceptable reduction while score 0-1 is poor. Table 1

Table 1: Quality of reduction scoring system (10)

Items	Scores
Garden alignment
AP view: slight valgus or normal	1
Lat view: 160°–180°	1
Fragment displacement
AP view: positive or neutral medial cortex support	1
Lat view: anterior cortex smooth continuity	1
Quality of fracture reduction
Excellent	4
Acceptable	3 or 2
Poor	1 or 0

AP: Anteroposterior, Lat: Lateral

Statistical methods

Data processing and analysis were conducted using IBM SPSS Statistics for Windows, version 23.0 (SPSS Inc., Chicago, IL, USA). Continuous variables with normal distribution were expressed as mean ± standard deviation along with the range, whereas skewed (non-parametric) data were presented as medians with their corresponding interquartile ranges (IQR). Categorical data were summarized using frequencies and percentages. The normality of data distribution was evaluated using both the Kolmogorov-Smirnov and Shapiro-Wilk tests. Comparative analysis between groups was performed using the independent samples t-test for normally distributed variables, and the Mann–Whitney U test for non-normally distributed data. Qualitative variables were compared using the Chi-square test, and Fisher’s exact test was applied when the expected frequency in any cell was below five. Statistical significance was determined at a 95% confidence level, with p-values < 0.05 indicating statistical significance.

 

Results

There were no notable variations between the DHS and PFN groups regarding baseline characteristics. The mean age was 63.45 ± 14.95 years in the DHS group and 66.45 ± 9.08 years in the PFN group (p = 0.147). Sex distribution (male: 75% vs. 50%, p = 0.102), fracture side (left: 60% vs. 55%, p = 0.749), AO classification (31A1.2: 55% vs. 65%, p = 0.519), and surgeon experience (consultant: 45% vs. 60%, p = 0.272) were also comparable between the two groups.

There was no notable variations between the DHS and PFN groups regarding the quality of reduction score (mean ± SD: 3.20 ± 0.77 vs. 3.10 ± 0.72; p = 0.673). Similarly, the distribution of reduction quality levels (acceptable vs. excellent) showed no significant difference between the groups (p = 0.507). Table 2

Table 2: Comparison between DHS Group and PFN Group according to Quality of reduction

	DHS (n=20)	PFN (n=20)	P-value
Quality of reduction score
Mean±SD	3.20±0.77	3.10±0.72	0.673
Median (IQR)	3 (3-4)	3 (3-4)
Range	2-4	2-4
Level of quality of reduction score
Acceptable	12 (60.0%)	14 (70.0%)	0.507
Excellent	8 (40.0%)	6 (30.0%)

PFN: Proximal Femoral Nail, DHS: Dynamic Hip Screw, SD: Standard Deviation, IQR: Interquartile Range.

There was no notable variation in TAD between the DHS and PFN groups. The mean TAD was 24.88 ± 9.41 mm in the DHS group and 21.72 ± 7.01 mm in the PFN group (p = 0.236). The proportion of cases with normal TAD was 60% in the DHS group and 70% in the PFN group (p = 0.507). Table 3

Table 3: Position of the implant (TAD) (mm) between the studied groups

	DHS (n=20)	PFN (n=20)	P-value
TAD (mm)
Mean±SD	24.88±9.41	21.72±7.01	0.236
Range	7-42	6-32
TAD Level
Abnormal	8 (40.0%)	6 (30.0%)	0.507
Normal	12 (60.0%)	14 (70.0%)

DHS: Dynamic Hip Screw, PFN: Proximal Femoral Nail, TAD: Tip-Apex Distance, SD: Standard Deviation

In the PFN group (n=20), the mean postoperative neck shaft angle was 131.30 ± 4.54°, compared to 134.70 ± 3.77° on the contralateral intact side, showing an average varus malalignment of approximately 3°, though this variation was not notable (p=0.109). In contrast, the DHS group (n=20) showed no appreciable difference between the postoperative neck shaft angle (135.45 ± 6.33°) and the intact side (135.70 ± 6.42°), with a non-significant p-value of 0.827. Overall, there was no notable change between the postoperative and contralateral neck shaft angles in either group (p > 0.05). Table 4 and Figure 2

Table 4: Comparison between Post neck shaft angle and neck shaft angle of contralateral intact side in each group DHS Group and PFN Group

	Post Neck Shaft Angle	Neck shaft angle of intact side	P-value
DHS (n=20)
Mean±SD	135.45±6.33	135.70±6.42	0.827
Range	124-147	126-147
PFN (n=20)
Mean±SD	131.30±4.54	134.70±3.77	0.109
Range	123-139	126-140

DHS: Dynamic Hip Screw, PFN: Proximal Femoral Nail, Post Neck Shaft Angle: Postoperative Neck Shaft Angle, mean ± SD: Mean ± Standard Deviation.

 

Figure 2: (A) Post Neck shaft angle and Neck Shaft Angle of Contralateral unaffected side of a case of DHS. (B) There is 5 degrees of Varus malalignment as compared to the unaffected contralateral side in a PFN case.

 

In the PFN group (n=20), the mean lateralization of the FS on the injured side was significantly higher compared to the DHS group (56.60 ± 7.07 vs, 49.50 ± 6.59 mm, p=0.002). However, on the non-injured side, there was no statistically significant difference between the PFN group and the DHS group (51.65 ± 4. vs. 49.65 ± 6.09 mm, p-value = 0. 261. Figure 3 and Figure 4

 

Figure 3: Comparison between DHS Group and PFN Group according to injured side lateralization of femoral shaft.

 

Figure 4: (A) shows Lateralization of femoral shaft in DHS (uninjured side 50 mm, injured side 49 mm). (B) shows lateralization of femoral shaft in PFN (uninjured side 47 mm, injured side 54 mm).

Discussion

DHS and PFN are both widely accepted surgical options for the management of intertrochanteric (IT) hip fractures. Although extensive literature exists comparing their performance in unstable fracture patterns, data specifically addressing their outcomes in stable IT fractures remain relatively scarce. The present study was designed to evaluate and compare the clinical and radiographic outcomes of DHS versus PFN in the operative treatment of stable intertrochanteric fractures.

The findings revealed a statistically significant increase in FS lateralization in cases treated with PFN compared to those who underwent DHS fixation. As for the NSA, the PFN group exhibited a mean varus deviation of approximately three degrees relative to the DHS group; however, this difference did not reach statistical significance.

In a study involving 70 cases with AO 31A1–2 intertrochanteric fractures, Long Fang and Jian Qi (4) observed an inverse correlation between the femoral NSA and the degree of FS lateralization following PFN fixation. Specifically, a reduction in the NSA was associated with a corresponding increase in lateralization of the FS.

The concept of femoral lateralization parallels that of femoral offset, a critical parameter used to evaluate hip geometry, particularly in total hip arthroplasty (THA). Femoral offset is modulated by the NSA —rising with varus orientation and diminishing with valgus alignment. Importantly, femoral offset has been shown to positively correlate with the strength of the hip abductor musculature, especially the gluteus medius, as well as with the extent of hip abduction. Consequently, in the context of peritrochanteric fractures, restoration of femoral lateralization—akin to optimizing femoral offset in THA—is essential for preserving normal hip biomechanics and should approximate the patient’s native anatomical values as closely as possible (4).

A comprehensive Cochrane systematic review (11), encompassing 73 studies, compared DHS and PFN in the treatment of both stable and unstable IT fractures. The findings indicated that extramedullary fixation methods, such as DHS, provide functional outcomes comparable to those of intramedullary (cephalomedullary) devices in managing extracapsular fragility fractures of the hip. Although intramedullary nails are linked to lower incidences of infection and non-union, they are associated with a higher rate of implant-related fractures—a complication that remains unresolved despite advances in nail design.

In a separate study, Hariharan Mohan and Prakash Kumar (12) evaluated 54 cases with two-part IT fractures (AO 31A1 classification) and concluded that there was no definitive evidence favoring PFN over DHS. Their results supported the clinical equivalence of both fixation methods in managing these specific fracture patterns.

In a comparative study conducted by Weiguang Yu (13) with extended follow-up, outcomes of cases treated with Proximal Femoral Nail Antirotation (PFNA) were evaluated against those managed with DHS. The DHS group exhibited a higher incidence of reoperation within the first postoperative year and experienced more orthopedic-related complications. Statistically significant improvements in Harris Hip Scores (HHS) were consistently observed in the PFNA group across multiple follow-up intervals. However, there was no notable difference in the incidence of systemic medical complications between the two cohorts. Based on these findings, the study suggested that DHS may be less favorable than PFNA for the surgical management of stable intertrochanteric femoral fractures.

A key limitation of the study was its relatively small sample size and the absence of comprehensive clinical follow-up, which restricted the ability to correlate radiographic parameters with long-term functional outcomes.

Conclusions

Both DHS and PFN provide good and comparable radiological outcomes for minimally displaced intertrochanteric fractures. However, DHS demonstrated advantages over PFN in terms of reduced FS lateralization and lower cost. The functional impact of FS lateralization on union rates and failure rates remains unclear.

Acknowledgments: None.

Declaration of interest statement: None to be declared.

Financial Disclosure and Sources of Support: None to be declared.

About the authors

Mohamed Hamdy Abdel Rahim

Orthopedic Surgery Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt

Email: Mohamedhamdy9581@gmail.com
ORCID iD: 0009-0006-2557-1004

Assistant Lecturer, MSc, Orthopedic Surgery Department

Mohamed Awad

Orthopedic Surgery Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt.

Email: Mohamed_awad2007@hotmail.com
ORCID iD: 0000-0003-4916-0411

Assistant Professor, MD, Orthopedic Surgery Department

Ahmed Morsi

Orthopedic Surgery Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt.

Email: ahmorsi74@gmail.com
ORCID iD: 0009-0004-0124-3351

 Assistant Professor, MD, Orthopedic Surgery Department

Ahmed Elsaeed

Orthopedic Surgery Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt.

Email: Drahmedsaeed88@yahoo.com
ORCID iD: 0000-0002-9929-3071

Professor, MD, Orthopedic Surgery Department

Mostafa Aly Elabd

Orthopedic Surgery Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt.

Author for correspondence.
Email: Moustaphaali135@gmail.com
ORCID iD: 0000-0001-5543-4971

Lecturer, MD, Orthopedic Surgery Department

References

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