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Views: 0 Author: Site Editor Publish Time: 2026-07-24 Origin: Site
Introduction
Intertrochanteric fractures are among the most common hip fractures in elderly patients, accounting for approximately 50% of all hip fractures.
Because these fractures frequently occur in patients with osteoporosis, achieving stable fixation remains one of the greatest challenges in orthopedic trauma surgery.
Currently, Proximal Femoral Nail Antirotation (PFNA) is widely regarded as one of the preferred fixation methods for intertrochanteric fractures due to its minimally invasive design, strong rotational stability, and favorable biomechanical characteristics.
However, despite continuous improvements in implant design, postoperative complications remain clinically significant, including:
Lag screw or blade cut-out
Varus collapse
Screw migration
Loss of reduction
Implant failure
These complications are particularly difficult to manage in:
Unstable intertrochanteric fractures
Osteoporotic bone
Lateral wall fractures
Reverse oblique fracture patterns
To overcome these limitations, Chinese orthopedic researchers have explored new fixation concepts based on proximal femoral anatomy, trabecular architecture, and biomechanical reconstruction principles.
Two major research directions have emerged:
Based on the proximal femoral trabecular system, Professor Yingze Zhang’s team proposed the Zhang’s N-Triangle Theory and developed the:
Proximal Femoral Bionic Nail (PFBN)
Professor Dianying Zhang’s team further developed the concept of mechanical balance and designed:
Proximal Femoral Lateral Wall Bionic Nail (PFLBN)
Proximal Femoral Total Bionic Nail (PFTBN)
These innovations represent a new generation of proximal femoral fixation concepts, aiming to restore the natural biomechanics of the proximal femur rather than simply stabilize the fracture mechanically.
Key Takeaways
PFNA remains a widely used standard implant for intertrochanteric fractures, but mechanical complications still occur.
The proximal femur relies on complex trabecular structures for load transmission and stability.
Zhang’s N-Triangle Theory provides a new understanding of proximal femoral biomechanics.
PFBN introduces an additional transverse supporting screw to reconstruct a triangular fixation structure.
PFLBN and PFTBN focus on restoring lateral wall support and mechanical lever balance.
These designs represent a shift from traditional fixation toward biomechanical reconstruction.
The intertrochanteric region plays a critical role in transferring forces between the femoral head and shaft.
During normal activities such as:
Standing
Walking
Stair climbing
the proximal femur experiences complex:
Compression forces
Tensile forces
Rotational stresses
Bending moments
In elderly patients with osteoporosis, reduced bone density weakens this mechanical system.
After fracture, the original force transmission pathway is disrupted, resulting in:
Loss of medial support
Damage to trabecular structures
Increased risk of collapse
Therefore, successful fixation requires more than simply connecting fracture fragments.
The ideal implant should restore:
Load-bearing capacity
Rotational stability
Varus resistance
Proximal femoral biomechanical balance
The Proximal Femoral Nail Antirotation (PFNA) system has become one of the most commonly used intramedullary fixation devices worldwide.
Its advantages include:
Minimally invasive insertion
Shorter operative time
Reduced soft tissue damage
Strong rotational control
Good performance in osteoporotic bone
Compared with traditional sliding hip screws, PFNA provides improved stability by placing the implant closer to the mechanical axis of the femur.
However, PFNA does not completely reproduce the natural biomechanical structure of the proximal femur.
Despite excellent clinical results, PFNA-related complications remain reported.
The proximal fixation element may migrate through weakened cancellous bone, especially in:
Severe osteoporosis
Poor blade position
Unstable fracture patterns
Loss of medial support may cause:
Femoral neck shortening
Increased neck-shaft angle reduction
Hip dysfunction
Traditional cephalomedullary nails mainly reconstruct compression support.
However, the tensile trabecular system remains insufficiently restored.
This limitation became the theoretical foundation for the development of PFBN.
Traditional intramedullary nails, such as PFNA and Gamma nails, have significantly improved the treatment outcomes of intertrochanteric fractures. However, despite their excellent biomechanical properties, postoperative complications remain a major concern.
The main reason is that conventional implants mainly reconstruct the compressive force transmission system of the proximal femur but fail to fully restore the tensile trabecular structure.
In normal proximal femoral anatomy, the stability of the femoral neck depends on the coordinated function of:
Primary compression trabeculae
Primary tensile trabeculae
Secondary compression trabeculae
Lateral femoral wall structure
When an intertrochanteric fracture occurs, the fracture line usually extends from the greater trochanter toward the lesser trochanter, disrupting both:
The primary compression trabecular system
The primary tensile trabecular system
This disruption leads to:
Loss of medial support
Increased varus stress
Femoral head-neck collapse
Screw migration or cut-out
Therefore, restoring only the compression axis is insufficient. A more comprehensive reconstruction strategy is required.
Based on this biomechanical concept, Professor Zhang Yingze’s team developed the Proximal Femoral Bionic Nail (PFBN).
The core philosophy of PFBN is:
Reconstruct the natural biomechanical triangle of the proximal femur through implant design.
Compared with conventional cephalomedullary nails, PFBN introduces an additional transverse supporting screw.
The implant consists of:
Main intramedullary nail
Cephalocervical screw
Transverse supporting screw
Together, these three components create a stable triangular configuration.
The traditional PFNA mainly relies on:
Blade or screw fixation within the femoral head
Intramedullary nail support inside the femoral canal
However, because the tensile trabecular system remains unreconstructed, the proximal femoral fragment may still experience:
Rotational instability
Varus collapse
Lateral migration
PFBN attempts to solve this problem by adding a transverse supporting element.
This design provides:
The additional supporting screw improves resistance against:
Femoral head rotation
Fracture fragment displacement
Implant toggling
Especially in unstable fractures with:
Posteromedial comminution
Large lesser trochanter fragments
Reverse oblique fracture patterns
the additional support may provide improved mechanical control.
Varus collapse is one of the most common failure mechanisms after intertrochanteric fracture fixation.
The main causes include:
Loss of medial cortical support
Excessive axial loading
Insufficient lateral wall stability
The triangular fixation structure created by PFBN distributes loading forces through multiple directions, reducing excessive concentration of stress at the screw-bone interface.
The normal proximal femur functions as an integrated mechanical structure.
The compression trabeculae transmit:
Body weight loading
The tensile trabeculae resist:
Bending stress
Muscle traction forces
PFBN attempts to restore both systems through implant geometry.
Therefore, compared with traditional nails, PFBN represents a transition from:
"Fracture fixation"
to:
"Biomechanical reconstruction."
To verify the theoretical advantages of PFBN, multiple biomechanical studies have evaluated its performance compared with conventional fixation systems.
Published studies have investigated PFBN through:
Finite element analysis
Cadaveric biomechanical testing
Comparative mechanical experiments
The main findings include:
Rotational instability is an important factor affecting healing after intertrochanteric fracture fixation.
Traditional cephalomedullary nails mainly rely on:
Blade/screw purchase within cancellous bone
Nail-canal interaction
However, osteoporotic bone may provide insufficient rotational resistance.
PFBN improves rotational control through its additional supporting screw, creating a stronger three-dimensional fixation structure.
Potential benefits include:
Reduced femoral head rotation
Lower risk of screw loosening
Better maintenance of fracture reduction
Postoperative femoral neck shortening and collapse remain frequent concerns, especially in:
Unstable intertrochanteric fractures
Severe osteoporosis
Reverse oblique fractures
The triangular support structure of PFBN increases the mechanical stability of the proximal fragment.
By distributing forces across multiple fixation points, PFBN may reduce:
Excessive sliding
Varus deformation
Implant failure
Elderly patients with intertrochanteric fractures commonly present with:
Reduced bone mineral density
Enlarged medullary canal
Weak cancellous bone
These conditions increase the risk of:
Screw cut-out
Blade migration
Loss of fixation
The bionic design concept attempts to compensate for poor bone quality by improving implant-bone force transmission rather than relying solely on screw purchase.
Although PFNA remains the current mainstream implant for most intertrochanteric fractures, PFBN represents a new direction in implant development.
The significance of PFBN is not simply the addition of another screw.
More importantly, it introduces a new treatment philosophy:
Fix the fracture with stronger implants.
Reconstruct the natural biomechanical structure of the proximal femur.
This concept may be particularly valuable for:
AO/OTA 31-A2 unstable fractures
AO/OTA 31-A3 reverse oblique fractures
Severe osteoporosis
Loss of lateral wall support
Comminuted proximal femoral fractures
Despite promising biomechanical advantages, several limitations remain.
Most current evidence comes from:
Biomechanical studies
Finite element analysis
Early clinical observations
Large-scale multicenter randomized controlled trials are still needed.
Compared with conventional PFNA:
PFBN implantation requires:
Accurate positioning
Understanding of proximal femoral anatomy
Familiarity with additional screw placement
Therefore, appropriate surgical training is necessary.
As a relatively new implant system, PFBN is not yet as widely available as traditional devices such as:
PFNA
Gamma Nail
InterTan
Long-term clinical outcomes require further evaluation.
While the PFBN concept focuses on reconstructing the trabecular structure of the proximal femur, Professor Zhang Dianying’s team from Peking University People’s Hospital proposed another important biomechanical theory:
The Lever Reconstruction Balance Theory.
This theory provides a new perspective for understanding why fixation failure occurs after intertrochanteric fracture surgery.
Traditional concepts mainly emphasize:
Implant strength
Screw purchase
Medial cortical support
Reduction quality
However, postoperative complications such as:
Varus collapse
Femoral neck shortening
Implant loosening
Screw cut-out
cannot always be fully explained by these factors.
The Lever Reconstruction Balance Theory suggests that the proximal femur functions similarly to a mechanical lever system.
The stability of fixation depends on whether the implant can reconstruct the balance between:
The support side
The resistance side
The mechanical fulcrum
In this theory, the proximal femur can be compared to a tower crane structure.
The components play different mechanical roles:
The lateral femoral wall acts like the counterweight of a tower crane.
Its main function is:
Providing lateral resistance
Preventing excessive collapse
Maintaining alignment of the femoral head-neck fragment
When the lateral wall remains intact, it can effectively resist:
Varus forces
Rotational displacement
Lateral migration
However, when the lateral wall is damaged by fracture:
The mechanical balance is lost
The proximal fragment becomes unstable
The risk of fixation failure increases significantly
The fulcrum of this lever system is located near:
The fracture interface
The junction between the implant and proximal fragment
The closer the implant support point is to the physiological fulcrum, the greater the mechanical stability.
Therefore:
An ideal implant should reconstruct the natural mechanical fulcrum of the proximal femur.
This concept provides a theoretical basis for the development of new implant designs such as PFLBN and PFTBN.
Based on the lever reconstruction balance theory, Professor Zhang Dianying’s team developed:
Proximal Femoral Lateral Wall Bionic Nail (PFLBN)
The core design objective is:
Replace the lost lateral wall resistance using implant-based mechanical reconstruction.
In unstable intertrochanteric fractures, especially those involving lateral wall destruction, conventional implants may lose their natural lateral support.
PFLBN introduces an additional anchoring screw beneath the lesser trochanter region.
This screw connects:
The proximal fracture fragment
The femoral shaft
creating a new mechanical resistance structure.
Depicted in the figure are PFLBN (left) and PFTBN (right).
In normal anatomy:
The lateral femoral wall provides resistance against:
Femoral head-neck varus displacement
Lateral migration of the proximal fragment
Excessive sliding of cephalocervical screws
After fracture:
The lateral wall may become:
Fragmented
Shortened
Mechanically ineffective
Traditional fixation relies heavily on the damaged bone structure.
PFLBN changes this strategy.
Instead of depending on the damaged lateral wall, it uses the implant itself to recreate the missing support function.
The additional anchoring screw acts as an artificial lateral wall.
This transforms the fixation concept from:
Bone-dependent stability
into:
Implant-assisted biomechanical reconstruction.
Based on further development of PFBN and PFLBN, researchers designed:
Proximal Femoral Total Bionic Nail (PFTBN).
The goal of PFTBN is not only to reconstruct:
Compression support
but also:
Tensile support
Rotational stability
Lateral resistance
Therefore, PFTBN represents a more comprehensive reconstruction strategy.
The design philosophy of PFTBN includes:
Through cephalocervical fixation:
Maintains femoral head position
Provides axial load transmission
Through additional supporting components:
Restores missing tensile trabecular function
Improves resistance against bending forces
Through anchoring screws:
Restores lateral resistance
Reduces varus collapse tendency
Together, these components create a multi-directional stabilization system.
Implant | Main Design Concept | Main Advantage | Suitable Fracture Patterns |
|---|---|---|---|
PFNA | Intramedullary fixation with blade/screw support | Mature technique, reliable outcomes | Stable and most unstable fractures |
PFBN | Reconstruction of proximal femoral trabecular structure | Improved rotational and anti-collapse stability | Unstable intertrochanteric fractures |
PFLBN | Reconstruction of lateral wall resistance | Restores missing lateral support | Lateral wall deficient fractures |
PFTBN | Comprehensive biomechanical reconstruction | Multi-dimensional stability | Complex unstable fractures |
Although PFNA remains the preferred implant for most intertrochanteric fractures, bionic nail concepts may provide additional options for challenging cases.
Potential indications include:
Features:
Multiple fracture fragments
Loss of medial support
Poor rotational stability
Bionic fixation may provide additional mechanical control.
Reverse oblique fractures are among the most unstable intertrochanteric fracture patterns.
Characteristics include:
High shear forces
Lateral displacement tendency
Increased implant failure risk
Additional support structures may theoretically improve stability.
In osteoporotic bone:
Traditional fixation relies on:
Screw purchase strength
However, reduced bone quality limits fixation reliability.
Bionic nails aim to improve stability by:
Optimizing force transmission
Increasing mechanical balance
Reducing dependence on bone quality
The evolution from PFNA to PFBN, PFLBN, and PFTBN reflects a fundamental change in orthopedic implant philosophy.
The development pathway can be summarized as:
Fix the fracture
Focus:
Implant strength
Basic stabilization
↓
Improve fixation mechanics
Focus:
Better screw design
Improved rotational control
↓
Reconstruct biological biomechanics
Focus:
Trabecular restoration
Lever balance reconstruction
Bionic implant design
The future of intertrochanteric fracture fixation may no longer rely solely on stronger implants.
Instead, successful fixation may depend on:
Understanding native anatomy
Restoring physiological load transmission
Designing implants that imitate human biomechanics
Intertrochanteric fractures remain one of the most challenging problems in orthopedic trauma, especially among elderly patients with osteoporosis.
Although modern intramedullary systems such as PFNA, Gamma Nail, and InterTan have significantly improved treatment outcomes, complications related to mechanical failure continue to occur.
The main challenges include:
Screw cut-out
Femoral neck shortening
Varus collapse
Implant loosening
Loss of fracture reduction
These complications are not only related to implant strength but are closely associated with whether the fixation system can restore the natural biomechanics of the proximal femur.
The development of PFBN, PFLBN, and PFTBN represents a new stage in implant evolution:
From simple fracture fixation toward biomechanical reconstruction.
Despite the emergence of new bionic nail concepts, PFNA remains one of the most widely used implants for intertrochanteric fractures worldwide.
The reasons include:
PFNA has been extensively studied with:
Large clinical series
Long-term follow-up
Established surgical techniques
It provides reliable fixation for the majority of intertrochanteric fractures.
PFNA offers:
Small incision
Reduced soft tissue damage
Short operation time
Early postoperative mobilization
These advantages are particularly important for elderly patients.
Because PFNA has been used globally for many years:
Surgeons are familiar with the technique
Instruments are widely available
Clinical protocols are well established
Therefore, PFNA will continue to play a major role in intertrochanteric fracture treatment.
The development of PFBN, PFLBN, and PFTBN does not mean traditional implants are ineffective.
Instead, these innovations aim to address situations where conventional fixation may be insufficient.
The main targets include:
When the lateral femoral wall is damaged:
The proximal fragment loses external resistance
Varus collapse risk increases
PFLBN attempts to reconstruct this missing support.
Poor bone quality reduces:
Screw holding strength
Implant-bone stability
Bionic systems attempt to improve stability through mechanical reconstruction rather than relying only on bone purchase.
Examples include:
AO/OTA 31-A2 unstable fractures
AO/OTA 31-A3 reverse oblique fractures
Multi-fragmentary fractures
These fractures involve complex force transmission problems requiring more advanced fixation concepts.
Yes.
PFNA remains the most commonly used intramedullary fixation system and has strong clinical evidence supporting its effectiveness.
However, for extremely unstable fractures, especially those with:
Severe comminution
Lateral wall destruction
Osteoporosis
newer designs such as PFBN or PFLBN may provide additional biomechanical advantages.
The main difference is the fixation concept.
PFNA:
Focuses on:
Intramedullary support
Femoral head fixation
Sliding compression
PFBN:
Adds:
A transverse supporting screw
A triangular stabilization structure
Its goal is to reconstruct both compression and tensile support systems of the proximal femur.
Potential indications include:
Unstable intertrochanteric fractures
Osteoporotic fractures
Fractures with rotational instability
Cases with high risk of implant failure
However, clinical indications should be determined according to fracture pattern, bone quality, and surgeon experience.
Currently, no.
Bionic nails are innovative implant concepts supported by biomechanical studies and early clinical research.
More:
Multicenter clinical studies
Long-term follow-up data
Randomized controlled trials
are needed before they can replace established systems.
Common reasons include:
Especially:
Varus reduction
Loss of medial support
Weak bone reduces implant stability.
Loss of lateral resistance increases collapse risk.
Examples:
Incorrect screw position
Insufficient fixation
Poor entry point
Intertrochanteric fractures are among the most common and challenging osteoporotic fractures.
PFNA remains the current mainstream fixation method with extensive clinical evidence.
Traditional implants mainly restore compression support but may not fully reconstruct tensile and lateral biomechanical structures.
The PFBN concept introduces trabecular reconstruction through a bionic triangular fixation design.
PFLBN and PFTBN further develop the idea of lever reconstruction and lateral wall restoration.
Future implant development may focus on restoring physiological biomechanics rather than simply increasing implant strength.
The evolution from PFNA to PFBN, PFLBN, and PFTBN reflects the continuous advancement of orthopedic trauma fixation concepts.
The treatment philosophy of intertrochanteric fractures is gradually shifting:
From:
“How to fix the fracture?”
to:
“How to restore the normal biomechanics of the proximal femur?”
By integrating:
Trabecular anatomy
Mechanical lever principles
Three-dimensional fixation concepts
bionic nail systems provide a new direction for the management of complex proximal femoral fractures.
Although further clinical studies are required to confirm their long-term superiority, these innovations represent an important step toward more anatomical, biomechanical, and patient-specific fracture fixation strategies.
