Finite element simulation of three surgical treatments of distal radius intra-articular fracture

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FINITE ELEMENT SIMULATION OF THREE SURGICAL TREATMENTS OF DISTAL RADIUS INTRA-ARTICULAR FRACTURE

ARASH NASROLLAHI SHIRAZI

A report submitted in partial fulfillment of the requirements for the award of the degree of

Master of Engineering (Mechanical)

Faculty of Mechanical Engineering Universiti Teknologi Malaysia

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To my beloved mother and father, Fakhrosadat Banaroei and Mohsen Nasrollahi Shirazi and my brother and sister, Pooyan and Sanaz for their never ending support.

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ACKNOWLEDGEMENT

To complete this Master Degree Project report, I learned many useful softwares and I had received a lot of information and valuable guidance from my supervisor, Assoc Prof. Eng. Dr. Rafiq Abdul Kadir. His knowledge and proficiency in Biomechanics supported and encouraged me to complete this project.

I respect and thank my beloved family Mrs. Fakhrosadat Banaroei and Mr. Mohsen Nasrollahi Shirazi, my sibeling, Mr. Amir and Mrs Fateme for their constantly love and support.

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ABSTRACT

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ABSTRAKT

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TABLE OF CONTENT

CHAPTER TITLE PAGE

TITLE i

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF ABBREVIATIONS xiv

1 INTRODUCTION 1

1.1 Introduction 1

1.1.1 Wrist anatomy 1 1.1.1.1 Bones and joints 2

1.2 Wrist fracture 3

1.2.1 Distal radius fracture 3

1.3 Problem Statement 4

1.4 Objective of Study 5

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2 LITERATURE REVIEW 6

2.1 Introduction 6

2.1.1 Classification of intra-articular fracture 6 (1) Intra-articular fracture with displaced

dorsal fragment 7 (2) Dorsal split with dorsal dislocation 7 (3) palmar split with palmar dislocaton 8 (4) Complex distal radius fractures with

metaphyseal separation 9 (5) Destruction of the articular surface 9 2.2 Different studies on fixation methods 10 2.2.1 Clinical Method 10 2.2.1.1 Non-invasive Techniques 11 2.2.1.1.1 Conservative treatment 11 2.2.1.1.2 External Fixation 12 2.2.1.1.3 Pining 13 2.2.1.2 Open surgery 14 (a) Plates 14 (b) Fragment-specific Fixation 15 (c) Volar locking plates 16 2.2.2 Protocol for surgical treatment 17

2.3 Experimental Method 18

2.3.1 A novel non-bridging external fixator versus

volar angular stable plating 19 2.3.2 Comparing volar with dorsal fixation plates on

unstable extra-articular fractures 20 2.4 Computer Simulation Method 22

2.4.1 Biomechanical evaluation of three types of

implants 22

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3.1 Introduction 27

3.2 Mimics Software 27

Step 1: Imported the medical data 28 Step 2: Thresholding 29 Step 3: Segmentation density masks 29 Step 4: Region growing 30 Step 5: 3D Reconstruction 31 3.2.1 Constructed of fractured bone 32

3.3 Implant Design 35

3.3.1 Introduction of Solidworks Software 35 3.3.2 Designing the implants 36 3.4 Simulation of surgical fixation 37 3.5 Introduction to MSC.Marc Software 39 3.5.1 Analysing the three fixation methods 40 3.5.2 Applying the loads 41

4 RESULTS AND DISCUSSION 43

4.1 Introduction 43

4.2 Axial-loads results 44

4.2.1 Displacement 44 4.2.2 Von-Mises Stress 46

4.3 Bending results 49

4.3.1 Displacement 49 4.3.2 Von-Mises Stress 51

4.4 Torsional results 53

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5 DISCUSSION AND RECOMMENDATION 62

5.1 Discussion 62

5.2 Recommendations 63

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LIST OF TABLES

TABLE NO. TITLE PAGE

4.1 Maximum displacement (mm) and maximum von Mises stress (MPa) values of the bone around the screws of all three groups under the applied loads

47

4.2 Maximum displacement (mm) and maximum von Mises stress (MPa) values of the bone around the screws of all three groups under the bending loads

52

4.3 Maximum displacement (mm) and maximum von Mises stress (MPa) values of the bone around the screws of all three groups under the torsional loads

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TABLE OF FIGURES

FIGURE NO. TITLE PAGE

1.1 Distal and proximal rows of carpal bones 2

2.1 CT-based classification of comminuted intra-articular fractures of the distal radius. Type I: intra-articular

fracture with displaced dorso-ulnar fragment

7

2.2 Type II: dorsal split with dorsal dislocation 8

2.3 Type III: palmar split with palmar dislocation 8

2.4 Type IV: complex distal radius fractures with metaphyseal separation

9

2.5 Type V: destruction of the articular surface 10

2.6 Schematic drawing of a monolateral external fixator with double ball joints after application to the radial aspect of the second metacarpal and diaphysis of the radius: the distal ball joint is centred between the capitate (C) and lunate bone (L) (intraoperatively

by identification with a bone elevator under image intensification, lower part of the image) to allow for

mobilisation of the fixator.

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2.7 Typical placement of two T-pins for fixation a distal radius fracture is shown in this posterior-anterior radiograph. The surgeon has inserted two T-pins from

the radio styloid to stable fracture fixation. The surgeon has inserted two T-pins from the radio styloid

to stable fracture fixation

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2.8 A fragment-specific wrist fixation system 15

2.9 A 31-year-old woman with reverse Barton fracture fixed by volar locking plate

16

2.1O The southern Sweden treatment protocol for DRF when selecting different treatments the patient’s age

and demands

18

2.11 Experimental test with isolated radius placed of custom-made compensator to applied ratio (60-40%)

of the forces transferred to scaphoid and lunata fragments. (A) Non-bridging external fixation method.

(B) Volar locking fixation method

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2.12 (A)The LDRS 2.4-mm intermediate and styloid plates. (B)The LDRS 2.4-mm volar plate.

(C)The LDRS 2.4-mm volar and styloid plates. (D) The 3.5-mm stainless steel T plate.

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2.13 Finite element of different surgical methods. (A) T shape single volar plate meshing model. (B) Meshing

model of double-palates fixation method. (C) The modified double-plating (MDP) meshing model

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2.14 Loading conditions for model. Axial loading bending and torsion are indicated with arrows. The axial loading was applied in the middle of the upper radius

surface. The bending force was applied on the volar side of radius. Torsion is applied on both sides of the

radius representing the external rotating force

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2.15 (A) Average total displacement of the fracture site under 50 N axial compression, 2 N-m bending and 2 N-m torsion loads. (B) Maximum displacement of the

fracture site under 50 N axial compression, 2 N-m bending and 2 N-m torsion loads

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2.16 (A) Maximum von Mises stress value for bone in single, DP, and MDP models under 50 N axial compression, 2 N-m bending and 2 N-m torsional loads. (B) Maximum von Mises stress value of T plate

in single, DP, and MDP models under 50 N axial compression, 2 N-m bending and 2 N-m torsional loads

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3.1 CT scan image for using in mimic 28

3.2 The top and side views for radius bone that Thresholding by the white color triangular to separate

the radius bone

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3.3 The side view of region growing that shown in pink color

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3.4 The process of smoothing (A, B and C) to achieve radius bone

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3.5 The measured guide lines for cutting (A) Approximately 10 mm(10.44 mm) from the from articular surface. (B) About 15° (14.81°) volar wedge

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3.6 The simulated three segments unstable intra-articular fracture (AO 23-C2.1 fracture). The circle shows the

cut with the curve tool

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3.7 (A) The scaphoid segment cleaned meshes. (B) The lunate segment cleaned meshes. (C) The distal

part of the radius cleaned meshes (all segment related to the cortical parts only)

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3.8 (A) Intermediate dorsal LDRS 2.4 mm plate. (B) Volar T-shape LDRS 2.4 mm plate. (C) I-shape Styloid

LDRS 2.4 mm plate

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3.9 Fixed all the meshes around the screws on both cortical and cancellous parts of bone

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3.1O Fixed all the interfaced meshing part between all cancellous and cortical and screws. (The red parts

show the interfaced parts)

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3.11 Defined the young’s modulus, Poisson’s ratio and contact parts for each part (that showed in collared

parts)

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3.12 Axial loading that applied on scaphoid and lunate regions base on each percentage and tilt angle, bending load that exerted on simulated bone on volar side of the radius and the torsion applied of the radius part of the

bone

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4.1 Model rigidity under axial compressive load 45

4.2 Maximum displacement of the bone around the screws under the 10 N, 25 N, 50N, and 100 N loads

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4.3 Maximum von-Mises stress under the 10 N, 25 N, 50N and 100 N loads

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4.4 Maximum von-Mises stress of the bone around the screws under the 10 N, 25 N, 50N, and 100 N loads

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4.5 The contour plots of displacement for three groups of fixations under applied 100 N axial load

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4.6 The mean maximum displacement under bending loads (1 N-m, 1.5 N-m, 2 N-m)

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4.7 The maximum displacement around the screws under applied bending loads (1 N-m, 1.5 N-m, 2 N-m)

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4.8 The maximum von-Mises stress under applied bending loads (1 N-m, 1.5 N-m, 2 N-m)

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4.9 The maximum von-Mises stress around the screws under applied bending loads (1 N-m, 1.5 N-m and

2 N-m)

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4.1O The contour plots of displacement for three groups of fixations under applied 2 N bending load

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4.11 The mean maximum displacement under torsion loads (1.5 N-m, 2 N-m, 2.5 N-m)

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4.12 The maximum displacement around the screws under applied torsion loads (1.5 N-m, 2 N-m, 2.5 N-m)

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4.13 The maximum von-Mises stress under applied bending loads (1.5 N-m, 2 N-m and 2.5 N-m)

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4.14 The maximum von Mises stress around the screws under applied torsion loads (1.5 N-m, 2 N-m and

2.5 N-m)

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4.15 The contour plots of displacement for three groups of fixations under applied 2 N torsional load

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4.16 (A) Average total displacement of the fracture site under the 100 N axial compression, 2 N-m bending and 2.5 N-m torsional loads. The total displacement was averaged from the displacement of the nodes on the fracture site. (B) Maximum von Mises stress value

for bone in three groups of fixations under 100 N compression load, 2 N-m bending and 2.5 N-m

torsional loads

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LIST OF ABBREVIATIONS

2D - Two Dimensional 3D - Three Dimensional CAD - Computer-Aided design CT - Computerized Tomography DRFs - Distal Radius Fractures DP - Double Plating

FEA - Finite Element Analysis HU - Hounsfield Scale

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CHAPTER 1

INTRODUCTION

1.1 Wrist joint

Wrist joint is the most complex of all joints in the body. The wrist must be

extremely mobile to give our hands a full range of motion. At the same time, the wrist

must provide the strength for heavy gripping. The kinematics and kinetics of the wrist

hasn’t been completely understood yet. The wrist joint plays a significant role in

maintaining a normal daily life. Normal wrist motions involve with the ligaments as well

as the carpal, radius and ulna bones [1].

1.1.1 Wrist anatomy

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• bones and joints

• ligaments and tendons

• muscles

• nerves

• blood vessels

1.1.1.1 Bones and joints

The connections from the end of the forearm to the hand there are 15 bones. The

wrist itself contains 8 bones, called carpal bones, the ulna and the radius. The carpal

bones are separated into two rows, namely the proximal and distal that shown in Fig1.1.

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The wrist joint comprises into three different parts, the radiocarpal joint,

intercarpal joint and the distal radioulnar joint. Most of the movements of the wrist

occurs at the radiocarpal joint, which is a synovial articulation composed by distal end of

the radius and the scaphoid, lunate and triquetrum bones [2].

1.2 Wrist fracture

Wrist fractures are kind of fractures that happen any of carpal bones and two

forearm bones (radius and ulna). The most commonly wrist fractures are distal radius

and scaphoid fractures.

1.2.1 Distal radius fracture

Comminuted fractures of distal end of the radius are caused by high-energy

trauma and present as shear and impacted fractures of the articular surface of the distal

radius with displacement of the fragments. The position of the hand and the carpal bone

and also the impact of the forces cause the articular fragmentation and the displacement.

Distal radius fractures are very common. In fact, the radius is the most commonly

broken bone in the arm. The break usually happens when a fall causes someone to land

on their outstretched hands. It can also happen in a car accident, a bike accident, a skiing

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1.3 Problem Statement

Distal radius fractures are among the most common injuries, with an estimate

overall crude incidence of 36.6/10,000 years in women and 8.9/10,000

person-years in men. Assuming a continuous rise in the incidence of distal radial fractures with

age, and based on the fact that older population continues to grow, incidence of distal

radius fractures can be expected to increase. To allow for good functional outcome

following unstable distal radius fractures, restoration of both the radiocarpal and the

radioulnar relationship is essential, therefore surgical treatment should facilitate for

anatomic reduction and maintenance of the reduction. It means different surgical

methods can be used to fix the complicated, unstable and displaced distal radius

fractures.

The conventional volar plating for treated the dorsal displaced distal radius

fractures has been described with good results in young patients and with a mix of

fracture complexity. However, elderly patients with osteoporotic bone may have higher

risk of loss of reduction in conventional types of fixation because of screw loosening

and because of the toggle effect of the screws within the distal part of the plate.

Therefore the necessity of an optimum technique for restore not only the anatomical

alignment of the wrist but also its proper biomechanics such as preventing

re-displacement of the fragments and re-establishing the normal wrist load transmission

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1.4 Objective of study

The objective summery of this study included:

1) Simulation of the distal part of the wrist and also simulation the

intra-articular distal radius fracture (AO 23-C2.1).

2) To develop 3D model of the fractured bone for all types of fixation

methods.

3) To simulate various surgical treatments for this type of intra-articular

fracture.

4) To compare between all different types of surgical treatments for fracture

fixation of the distal radius.

1.5 Scope of study

The scope the study, to simulate the 3D model of radius bone and also simulated

the unstable intra-articular fracture on bone. The next step to find the surgical methods

for this kind of distal radius fracture and simulated these surgical method as same as the

real plates of fixations. Then according to surgical open reduction and internal fixation

should find the optimum positioning for all types of fixations on fractured bone. To

provide the valid analysis should find the best positions for boundary condition and

exerting the loads. Should mention that the loads values should be choose base on the

daily motions that fractured wrist faces. Finally, should compare the results of all types

Figure

Fig 1.1: Distal and proximal rows of carpal bones.

Fig 1.1:

Distal and proximal rows of carpal bones. p.19

References

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