Bending Stress | Neutral Axis | Working Length | Plate Mechanics
Bending Stress Distribution
Critical Must-Knows
- Bending moment creates linear stress distribution from maximum tension to maximum compression
- Neutral axis at centroid has zero bending stress - material here does not resist bending
- Stress proportional to distance from neutral axis: σ = My/I where y is distance from neutral axis
- Working length (distance between screws) affects stiffness as L³ - doubling length reduces stiffness 8-fold
- Plate should be placed on tension side for optimal biomechanics
Clinical Pearls
- "Working length inversely proportional to stiffness cubed - critical for bridge plating
- "Section modulus (I/c) determines bending strength - increases with height squared
- "Plate on tension side prevents gap formation and reduces stress shielding
- "Eccentric loading increases bending moment - explains failure in varus/valgus malalignment
Clinical Imaging
Imaging Gallery
Critical Bending Moment Exam Points
Linear Stress Distribution
Bending creates linear stress profile from maximum tension to maximum compression. Neutral axis at centroid has zero stress. Maximum stress at outer fibers: σ_max = Mc/I where c is distance to extreme fiber.
Working Length Effect
Stiffness inversely proportional to working length cubed: k ∝ 1/L³. Doubling distance between screws reduces stiffness 8-fold. Too stiff = stress shielding. Too flexible = excessive motion.
Plate Placement Principle
Plate should be on tension side of bone. Prevents gap formation, provides compression across fracture, reduces plate stress by allowing load sharing with bone. Compression side can gap without loss of stability.
Section Modulus
Bending strength proportional to I/c (section modulus). Doubling height increases strength 4-fold. Explains why thicker plates resist bending better. Also why hollow tubes efficient.
At a Glance
Bending creates a linear stress distribution from maximum tension at one surface to maximum compression at the opposite surface, with zero stress at the neutral axis (centroid). The fundamental equation σ = My/I describes bending stress (proportional to moment M, distance from neutral axis y, and inversely to area moment of inertia I). Critical clinical concept: working length (distance between screws) affects construct stiffness as L³—doubling working length reduces stiffness 8-fold. The section modulus (I/c) determines bending strength, explaining why thicker plates resist bending better (strength increases with height squared). Plates should be placed on the tension side of bone to prevent gap formation and reduce plate stress through load sharing. Understanding these principles is essential for bridge plating, plate selection, and analyzing construct failure.
MY ICIBending Stress Formula Components
| M | Moment Bending moment at cross-section (N·m or N·mm) |
| Y | y-distance Distance from neutral axis to point of interest |
| I | I (area moment) Second moment of area - resistance to bending |
| C | c-distance Distance from neutral axis to extreme fiber |
| I | I/c ratio Section modulus - determines maximum bending stress |
| M | Moment Bending moment at cross-section (N·m or N·mm) | C | c-distance Distance from neutral axis to extreme fiber |
| Y | y-distance Distance from neutral axis to point of interest | I | I/c ratio Section modulus - determines maximum bending stress |
| I | I (area moment) Second moment of area - resistance to bending |
Hook:MY ICI determines bending stress: σ = My/I with max at c!
PLIESFactors Affecting Working Length Stiffness
| P | Plate modulus Material stiffness (E) - titanium vs steel vs carbon fiber |
| L | Length (working) Distance between screws - L³ relationship to stiffness |
| I | I (area moment) Plate cross-section - width × thickness³/12 for rectangle |
| E | Empty screw holes Stress concentration points - reduce fatigue life |
| S | Screw configuration Number and spacing affects load transfer |
| P | Plate modulus Material stiffness (E) - titanium vs steel vs carbon fiber | E | Empty screw holes Stress concentration points - reduce fatigue life |
| L | Length (working) Distance between screws - L³ relationship to stiffness | S | Screw configuration Number and spacing affects load transfer |
| I | I (area moment) Plate cross-section - width × thickness³/12 for rectangle |
Hook:PLIES together determine construct stiffness!
TENTOptimal Plate Application Principles
| T | Tension side Place plate on tension surface for best biomechanics |
| E | Eccentric loading Consider physiologic loading direction (varus, valgus) |
| N | Neutral axis Material at centroid doesn't resist bending |
| T | Three-point bending Most common loading mode in long bones |
| T | Tension side Place plate on tension surface for best biomechanics | N | Neutral axis Material at centroid doesn't resist bending |
| E | Eccentric loading Consider physiologic loading direction (varus, valgus) | T | Three-point bending Most common loading mode in long bones |
Hook:Put your TENT on the tension side!
Overview and Fundamentals
Bending moment distribution is fundamental to understanding fracture fixation mechanics. When a long bone or plate is loaded in bending, internal stresses develop that vary linearly from maximum tension on one surface to maximum compression on the opposite surface. The neutral axis, located at the centroid of the cross-section, experiences zero bending stress and contributes nothing to bending resistance.
The bending stress at any point is given by the flexure formula: σ = My/I, where M is the bending moment, y is the perpendicular distance from the neutral axis, and I is the second moment of area. Maximum stress occurs at the outer fibers where y is maximum (y = c), giving σ_max = Mc/I. The ratio I/c is called the section modulus and determines bending strength.
Why Bending Matters in Fracture Fixation
Most long bone fractures experience bending loads during physiologic loading. Understanding bending stress distribution explains: (1) why plates should be on tension side, (2) how working length affects construct stiffness, (3) why eccentrically loaded fractures fail in predictable patterns, (4) how to optimize screw spacing for biological fixation.
Pure Bending vs Combined Loading
Pure bending: M only, linear stress distribution, neutral axis at centroid
Combined axial + bending: Axial stress shifts neutral axis, asymmetric stress distribution
Clinical: Most fractures experience combined loading - eccentric axial loads create bending moments (varus/valgus stress)
Material at Neutral Axis
Material at neutral axis contributes ZERO to bending resistance
Explains why:
- Hollow tubes as efficient as solid rods (same I/c)
- Trabecular bone in marrow cavity doesn't resist bending
- Intramedullary nails optimized with hollow design
Neutral Axis and Stress Distribution
Location of Neutral Axis
The neutral axis passes through the centroid of the cross-section and is perpendicular to the plane of bending. For symmetric sections (circular, square, I-beam), the neutral axis is at the geometric center. For composite sections (plate plus bone), the neutral axis shifts based on relative stiffness and area.
| Cross-Section Type | Neutral Axis Location | Section Modulus (I/c) | Clinical Example |
|---|---|---|---|
| Solid circular (diameter d) | Center | πd³/32 | Intact long bone, IM nail |
| Hollow circular (outer D, inner d) | Center | π(D⁴-d⁴)/32D | Cortical bone, hollow nail |
| Rectangular plate (width b, height h) | Center | bh²/6 | Compression plate |
| Plate-bone composite | Shifts toward stiffer material | Complex calculation | Fixed fracture |
Key Principles:
- Stress increases linearly with distance from neutral axis
- Maximum tensile stress on one surface, maximum compressive on opposite
- At neutral axis: σ = 0 (no contribution to bending resistance)
- Stress sign changes across neutral axis (tension to compression)
Composite Beam Behavior
When plate and bone share load, neutral axis shifts toward the stiffer material (steel plate). This means bone near the plate experiences less stress (stress shielding), while bone far from plate experiences higher stress. Proper working length balances load sharing to promote healing while preventing excessive motion.
Stress Distribution Across Section
For a rectangular cross-section in pure bending:
- Outer tension fiber: σ = Mc/I = M/(bh²/6) = 6M/bh²
- Neutral axis (center): σ = 0
- Outer compression fiber: σ = -Mc/I = -6M/bh²
The linear distribution means stress gradient is constant: dσ/dy = M/I.
Why Section Modulus Matters
Q: Why is a plate twice as thick more than twice as strong in bending? A: Section modulus I/c increases with height squared. For rectangular section, I/c = bh²/6. Doubling thickness (h) increases section modulus 4-fold, thus strength increases 4-fold for same bending moment. This is why small increases in plate thickness dramatically improve bending resistance.
Working Length in Fracture Fixation
Definition and Biomechanical Significance
Working length is the distance between the two innermost screws on either side of a fracture. It determines construct stiffness and affects fracture healing, stress shielding, and implant failure risk.
Beam deflection under three-point bending: δ = FL³/48EI
Where F is load, L is working length, E is elastic modulus, I is area moment of inertia.
Key relationships:
- Stiffness k = F/δ ∝ 1/L³ (inversely proportional to length cubed)
- Doubling working length reduces stiffness 8-fold
- Halving working length increases stiffness 8-fold
| Working Length Strategy | Stiffness | Stress Shielding | Fracture Motion | Clinical Application |
|---|---|---|---|---|
| Short (compression plating) | Very high | Maximum | Minimal | Simple fractures, absolute stability |
| Intermediate (standard bridge) | Moderate | Moderate | Moderate | Most fractures, relative stability |
| Long (flexible bridge) | Low | Minimal | Excessive | Risk of delayed union, implant failure |
| Optimal (3-5 cortices) | Balanced | Balanced | Micromotion only | Modern locking plate technique |
Clinical Implications
Too short (stiff):
- Excessive stress shielding
- Reduced fracture site strain (may impair healing)
- All load through implant (fatigue risk if no healing)
- Higher stress at screw-bone interface
Too long (flexible):
- Excessive fracture motion (may prevent healing)
- Increased implant stress (bending moment ∝ L)
- Cantilever beam effect if fracture doesn't heal
- Risk of implant failure before union
Optimal working length:
- 3-5 cortices (1.5-2.5 screw holes) on each side of simple fracture
- Longer for comminuted fractures (bridge entire comminution zone)
- Balance stiffness for healing while allowing micromotion
- Modern locked plating allows increased working length vs conventional
Working Length and Screw Density
Current principle: fewer screws, longer working length for biological fixation. Traditional AO teaching (6 cortices per fragment) too stiff. Modern bridge plating: 3-4 screws per fragment with working length chosen for appropriate flexibility. Exception: periarticular fractures need short working length for stable articular reduction.
Working Length Calculation
Q: How do you calculate working length in a plated fracture? A: Distance between innermost screws on opposite sides of fracture. NOT the distance between screw holes, but actual occupied holes. Empty holes within the working length act as stress risers and should be avoided. For comminuted fractures, bridge the entire comminution zone - working length is from end of comminution to first screw.
Plate Placement and Tension Band Principle
Tension Side vs Compression Side
Plates should ideally be placed on the tension surface of bone for optimal biomechanics. This principle is based on bending moment distribution and composite beam behavior.
Plate on tension side:
- Prevents gap formation on tension surface (plate resists tensile stress)
- Creates compression across fracture (pre-loading effect)
- Bone compression side can tolerate contact and load sharing
- Reduces plate stress by allowing composite action with bone
- Minimizes interfragmentary motion
Plate on compression side:
- Gap opens on tension surface (uncontrolled)
- Plate experiences higher bending stress
- Less stable construct
- Risk of delayed union or nonunion from gap
| Bone Segment | Physiologic Tension Surface | Optimal Plate Position | Rationale |
|---|---|---|---|
| Femur - lateral cortex | Lateral (tension band of IT band) | Lateral | Resist varus moment from body weight |
| Tibia - medial cortex | Anterior or medial | Anteromedial | Subcutaneous position, resist anterior bow |
| Humerus - anterolateral | Anterior with forward flexion | Anterolateral | Accessible, resist AP bending |
| Forearm bones | Variable with rotation | Dorsal radius, volar ulna | Based on anatomy and soft tissue |
Eccentric Loading and Bending Moment
Axial loads applied eccentric to the bone's mechanical axis create bending moments: M = P × e, where P is axial force and e is eccentricity (perpendicular distance from load line to neutral axis).
Clinical examples:
- Varus knee: medial compartment overload creates varus bending moment
- Hip joint reaction force lateral to femoral shaft: creates varus bending moment in proximal femur
- Patellar tendon pull anterior to tibial axis: creates anterior bending moment
This explains why:
- Varus malunion of femur fracture leads to increased implant stress and failure
- Proper alignment critical to minimize bending moments
- Plates should resist the direction of expected bending from eccentric loading
Tension Band Plating Example
Q: Why place lateral plate on distal femur fracture? A: Hip joint reaction force creates varus bending moment. With body weight medial to femoral shaft, lateral cortex experiences tension. Lateral plate resists this tensile stress, prevents lateral gap formation, and creates medial compression across fracture. Medial plate would allow lateral gap and higher plate stress.
Beam Theory and Implant Design
Second Moment of Area (Area Moment of Inertia)
The second moment of area (I) quantifies a cross-section's resistance to bending. It depends on how material is distributed relative to the neutral axis.
For rectangular cross-section: I = bh³/12 (b = width, h = height perpendicular to bending axis)
Key insights:
- I proportional to height cubed (h³): doubling height increases I by 8-fold
- Material far from neutral axis contributes more to I (y² term)
- This is why I-beams, hollow tubes are efficient - material concentrated at extremes
For circular cross-section:
- Solid: I = πd⁴/64
- Hollow: I = π(D⁴ - d⁴)/64
Hollow tube advantage: Can remove material near neutral axis (low contribution) while maintaining I by preserving outer diameter. Explains efficiency of cortical bone, intramedullary nails.
Plate Thickness Effect
For a plate of width b and thickness h:
- Area moment: I = bh³/12
- Section modulus: I/c = bh²/6 (c = h/2)
- Maximum bending stress: σ_max = 6M/bh²
Doubling plate thickness:
- I increases 8-fold (h³ relationship)
- Section modulus increases 4-fold (h² relationship)
- For same bending moment, stress decreases 4-fold
- Stiffness increases 8-fold
Clinical implication: Small increase in plate thickness dramatically improves bending strength and stiffness. However, may increase stress shielding. Modern locked plates can be thinner due to different load transfer mechanism (angle stability vs friction).
Locking vs Conventional Plate Mechanics
Conventional plate: Load transfer via friction (plate compression to bone). Bending creates friction force at plate-bone interface. Requires precise contouring.
Locking plate: Load transfer via screw-plate construct acting as internal-external fixator. Less dependent on plate-bone contact. Can use longer working length, maintain bending stability with fewer screws. Allows biological fixation principles.
Evidence Base
Working Length Controls Stability of the Locked Internal Fixator
- Working length (distance of the first screw to the fracture) was the dominant determinant of both axial and torsional rigidity of the LCP construct
- Omitting one screw hole on either side of the fracture made the construct almost twice as flexible in both compression and torsion
- More than three screws per fragment added little axial stiffness, and four screws did not increase torsional rigidity
- Plate failures invariably occurred through a screw hole where finite element analysis showed peak von Mises stress; greater working length lowered the load to plastic deformation when bone contact was absent
Screw–Bone Interface Modelling and Local Stress Around Locked Screws (FEA)
- In a locked-plate tibial mid-shaft fracture model, the global load–deformation response varied less than 1% between interface modelling strategies
- Interface modelling markedly altered the LOCAL stress–strain field around the screws — the principal determinant of screw loosening, bone damage and stress shielding
- Frictional and tied (bonded) interfaces gave similar peak strains (under 5% difference); the undersized pilot-hole pre-stress model produced the largest peri-screw strains
- Demonstrates that bending stress concentrates at the screw–bone interface, the typical site of construct failure
Scientific Basis of Biological Internal Fixation: Stability vs Biology
- The internal fixator splints rather than compresses; flexible stabilisation induces callus and reliable healing without anatomical reduction (as shown by locked nailing)
- The strain theory defines the tolerable instability — gross instability may still heal by callus, whereas minimal motion across a rigidly fixed small gap can be deleterious
- Extensive plate–bone contact damages periosteal blood supply, causing necrosis and temporary porosity (a biological, not mechanical, cause of so-called stress protection)
- Locked, threaded bolts allow minimally invasive percutaneous osteosynthesis (MIPO) without contouring the splint to the bone
Interfragmentary Strain Governs Healing: Gap Size and Movement
- In a sheep metatarsal osteotomy with an adjustable external fixator, larger interfragmentary movement/strain (≈31% vs ≈7%) stimulated more callus in small gaps (1–2 mm) but not in 6 mm gaps
- Increasing gap size from 1 to 6 mm significantly reduced the bending stiffness of the healed bone
- Healing was inferior once the gap exceeded 2 mm
- Provides the experimental basis for the interfragmentary-strain concept that links construct flexibility, gap size and callus formation
Locked Plating of Distal Femur: Stiffness, Callus and Plate Material
- Across 64 distal femur fractures, deficient periosteal callus (≤20 mm²) was present in 52%, 47% and 37% of fractures at 6, 12 and 24 weeks
- Callus was asymmetric — the medial cortex formed on average 64% more callus than the anterior/posterior cortices, reflecting the stiff lateral construct
- A longer bridge span only minimally improved callus (significant at 6 weeks only)
- More flexible titanium plates produced 56–76% more callus than stainless-steel plates
Far Cortical Locking Reduces Stiffness and Restores Symmetric Motion
- Far cortical locking (FCL) diaphyseal fixation of a periarticular distal femur plate had 81% lower initial stiffness than standard locked plating
- FCL generated nearly five times more interfragmentary motion under one body-weight load (highly significant, p below 0.001)
- FCL produced near-parallel interfragmentary motion, whereas standard locked plates showed 48% less motion at the near cortex than the far cortex (asymmetric, shear-prone)
- Residual strength after 100,000 cycles was equivalent between FCL and standard locked constructs (≈5 kN; p = 0.73)
Exam Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Scenario 1: Bending Stress Distribution and Neutral Axis
"Examiner shows cross-section of a long bone and asks: Explain the stress distribution when this bone is loaded in bending. What is the neutral axis and why is it important?"
Scenario 2: Working Length in Bridge Plating
"You are treating a comminuted mid-diaphyseal femur fracture with a locked plate. Explain how you would determine the optimal working length and why it matters for fracture healing and construct stability."
Scenario 3: Plate Positioning and Tension Band Principle
"You are treating a distal femur fracture with lateral locked plate. The examiner asks: Why do we place the plate laterally? What would happen if you placed it medially?"
MCQ Practice Points
Bending Stress Formula
Q: What does the flexure formula σ = My/I represent? A: Bending stress at distance y from neutral axis. M is bending moment, y is perpendicular distance from neutral axis, I is second moment of area. Stress is linear across section, maximum at outer fibers (y = c).
Section Modulus
Q: How does doubling the thickness of a plate affect its bending strength? A: Increases strength 4-fold. Section modulus I/c = bh²/6 for rectangular section. Doubling h increases section modulus by factor of 4, thus maximum stress σ_max = M/(I/c) decreases 4-fold for same moment.
Working Length Relationship
Q: If you double the working length in a plated fracture, how does construct stiffness change? A: Stiffness decreases 8-fold. From beam theory, stiffness is inversely proportional to working length cubed: k ∝ 1/L³. Doubling L means new stiffness is 1/(2L)³ = 1/8 of original stiffness.
Neutral Axis Significance
Q: Why is material at the neutral axis not effective at resisting bending? A: Stress at neutral axis is zero. From σ = My/I, when y = 0 (at neutral axis), σ = 0. Material contributes to bending resistance proportional to its distance from neutral axis. This explains efficiency of hollow tubes.
Plate Positioning
Q: Why should plates be placed on the tension side of bone? A: Prevents gap formation and reduces plate stress. Plate directly resists tensile stress, creating compression across fracture. Allows load sharing with bone. Plate on compression side would allow gap on tension surface and experience higher stress.
Eccentric Loading
Q: How does varus malalignment affect bending moment in a femoral fracture? A: Increases bending moment via eccentric loading. M = P × e where e is eccentricity. Varus shifts load line medial, increasing distance to lateral cortex, thus increasing varus bending moment and lateral cortex tensile stress.
Guidelines, Registries & Global Practice
Bending mechanics is a principle, not a disease, so it is governed by educational and technical standards from the major trauma organisations rather than by NICE/AAOS clinical practice guidelines. The dominant global framework is the AO/OTA synthesis of absolute versus relative stability, with broadly concordant teaching from EFORT (Europe), the British Orthopaedic Association / BOAST standards (UK), the Orthopaedic Trauma Association (North America) and the AOA (Australia). There is little controversy about the underlying physics; practice variation lies in how aggressively surgeons reduce construct stiffness (working length, plate material, far cortical locking) to optimise secondary healing, especially in distal femur fractures.
| Body / Framework | Region | Position on Bending & Working Length | Evidence basis |
|---|---|---|---|
| AO Foundation / AO Trauma | Global | Absolute stability (lag screw + compression plate, short working length) for simple/intra-articular; relative stability (bridge plate, longer working length, minimal contact) for comminuted diaphyseal fractures | Expert consensus + biomechanical (Perren, Stoffel) |
| OTA / OTA-classification users | North America | Endorses bridge plating with adequate plate span and limited screw density for comminuted shaft fractures | Consensus + cohort/biomechanical |
| BOA / BOAST (e.g. open & femoral fracture standards) | UK | Stable fixation appropriate to fracture personality; supports biological/relative-stability constructs for comminution | Standard of care guidance |
| EFORT instructional faculty | Europe | Same absolute-vs-relative-stability paradigm; emphasises stiffness modulation to avoid asymmetric callus | Educational consensus |
| AOA / RACS surgical science | Australia / NZ | Beam theory, section modulus and working length are core basic-science viva content | Curriculum standard |
Global Practice and Variation
The flexure formula (σ = My/I), the L³ working-length relationship and tension-side plating are universal and uncontested. Where practice genuinely varies is stiffness modulation:
- Plate material: Titanium (lower modulus, E ≈ 110 GPa) deflects more than stainless steel (E ≈ 200 GPa) for the same geometry; titanium plating produced 56–76% more callus than steel in distal femur fractures (Lujan 2010).
- Working-length doctrine: Modern teaching favours fewer screws and a longer working length over the older "six cortices per fragment" rule, but periarticular and simple fractures still demand short working lengths and absolute stability.
- Stiffness-reduction devices: Far cortical locking and active/dynamic plates are used selectively (more in North America/Europe) to add controlled axial micromotion (Doornink 2011).
Distal femur locking-plate fixation is the canonical real-world example where over-stiff constructs cause asymmetric callus and nonunion — the strongest signal that bending mechanics is clinically, not just theoretically, important.
Management Algorithm
BENDING MOMENT DISTRIBUTION IN FRACTURE FIXATION
Clinical summary
Bending Stress Fundamentals
- •Bending creates LINEAR stress distribution from max tension to max compression
- •Flexure formula: σ = My/I (M = moment, y = distance from neutral axis, I = area moment)
- •Maximum stress at outer fibers: σ_max = Mc/I where c is distance to extreme fiber
- •Neutral axis at centroid: zero stress, no contribution to bending resistance
Section Modulus and Strength
- •Section modulus I/c determines maximum bending stress for given moment
- •For rectangle: I/c = bh²/6 - proportional to height squared
- •Doubling plate thickness increases strength 4x (h² effect) and stiffness 8x (h³ effect)
- •Hollow tubes efficient: material at neutral axis removed, outer fibers preserved
Working Length Principles
- •Working length = distance between innermost screws on opposite sides of fracture
- •Stiffness ∝ 1/L³ - doubling length reduces stiffness 8-fold
- •Optimal: 3-5 cortices (1.5-2.5 holes) per fragment for relative stability
- •Too short = stress shielding; too long = excessive motion and implant stress
Plate Positioning
- •Plate on TENSION side for optimal biomechanics
- •Prevents gap formation, creates compression, reduces plate stress
- •Femur: lateral plate (varus moment from medial hip reaction force)
- •Tibia: anteromedial plate (resist anterior bow, subcutaneous access)
Clinical Applications
- •Eccentric loading creates bending moment: M = P × e
- •Varus/valgus malalignment increases bending stress and implant failure risk
- •Empty screw holes within working length = stress risers (avoid)
- •Locked plates allow longer working length than conventional (angle stability)
Key Numbers to Remember
- •I/c for rectangle = bh²/6 (width × height squared / 6)
- •Deflection ∝ L³ (length cubed relationship)
- •Area moment ∝ h³ (height cubed for rectangular section)
- •Modern bridge plating: 3-4 screws per fragment (vs old rule of 6 cortices)
References
-
Perren SM. Evolution of the internal fixation of long bone fractures: The scientific basis of biological internal fixation: choosing a new balance between stability and biology. J Bone Joint Surg Br. 2002;84(8):1093-1110. PMID: 12463652. doi:10.1302/0301-620x.84b8.13752
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Stoffel K, Dieter U, Stachowiak G, Gächter A, Kuster MS. Biomechanical testing of the LCP - how can stability in locked internal fixators be controlled? Injury. 2003;34(Suppl 2):B11-B19. PMID: 14580982. doi:10.1016/j.injury.2003.09.021
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MacLeod AR, Pankaj P, Simpson AHRW. Does screw-bone interface modelling matter in finite element analyses? J Biomech. 2012;45(9):1712-1716. PMID: 22537570. doi:10.1016/j.jbiomech.2012.04.008
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Gautier E, Sommer C. Guidelines for the clinical application of the LCP. Injury. 2003;34(Suppl 2):B63-B76. doi:10.1016/j.injury.2003.09.026
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Bottlang M, Doornink J, Lujan TJ, et al. Effects of construct stiffness on healing of fractures stabilized with locking plates. J Bone Joint Surg Am. 2010;92(Suppl 2):12-22. PMID: 21123589. doi:10.2106/JBJS.J.00780
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Claes L, Augat P, Suger G, Wilke HJ. Influence of size and stability of the osteotomy gap on the success of fracture healing. J Orthop Res. 1997;15(4):577-584. PMID: 9379268. doi:10.1002/jor.1100150414
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Cordey J, Borgeaud M, Perren SM. Force transfer between the plate and the bone: relative importance of the bending stiffness of the screws and the friction between plate and bone. Injury. 2000;31(Suppl 3):C21-C28. doi:10.1016/s0020-1383(00)80028-5
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Doornink J, Fitzpatrick DC, Madey SM, Bottlang M. Far cortical locking enables flexible fixation with periarticular locking plates. J Orthop Trauma. 2011;25(Suppl 1):S29-S34. PMID: 21248557. doi:10.1097/BOT.0b013e3182070cda
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Lujan TJ, Henderson CE, Madey SM, et al. Locked plating of distal femur fractures leads to inconsistent and asymmetric callus formation. J Orthop Trauma. 2010;24(3):156-162. PMID: 20182251. doi:10.1097/BOT.0b013e3181be6720
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Henderson CE, Lujan TJ, Kuhl LL, et al. 2010 mid-America Orthopaedic Association Physician in Training Award: healing complications are common after locked plating for distal femur fractures. Clin Orthop Relat Res. 2011;469(6):1757-1765. doi:10.1007/s11999-011-1870-6
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Strauss EJ, Schwarzkopf R, Kummer F, Egol KA. The current status of locked plating: the good, the bad, and the ugly. J Orthop Trauma. 2008;22(7):479-486. doi:10.1097/BOT.0b013e31817996d6
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Henschel J, Tsai S, Fitzpatrick DC, Marsh JL, Madey SM, Bottlang M. Comparison of 4 methods for dynamization of locking plates: differences in the amount and type of fracture motion. J Orthop Trauma. 2017;31(10):531-537. PMID: 28657927. doi:10.1097/BOT.0000000000000879
Key Biomechanics References
- Hibbeler RC. Mechanics of Materials. 10th ed. Pearson; 2017. (Beam theory and bending stress fundamentals)
- Beer FP, Johnston ER, DeWolf JT, Mazurek DF. Mechanics of Materials. 8th ed. McGraw-Hill; 2020. (Section modulus and stress distribution)
Australian Context
- The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) is a joint-replacement registry and does not systematically capture diaphyseal fracture-fixation hardware. Outcome data on bending-related fixation failure (plate fatigue fracture, screw breakage, distal femur nonunion) come from institutional and trauma-network cohorts and national trauma audit programmes rather than the AOANJRR.
Suggested Reading
- Rüedi TP, Buckley RE, Moran CG. AO Principles of Fracture Management. 3rd ed. Thieme; 2018. Chapter on biomechanics of fracture fixation provides comprehensive review of bending mechanics, working length principles, and plate positioning.