Gap closed Osteoporosis   is a disease of bones. In osteoporosis, the bone mineral density is reduced, making the bones fragile and weak leading to an increased risk of fracture. Over 80% of all fracture in people 50+ are due to osteoporosis. Internal fixation implants are commonly used for fracture fixations, but the current fracture fixation plates are primarily designed for healthy bone. And whilst they provide the required strength to assist the bone during load-bearing activities, the stiffness of the materials used is considered to inhibit adequate healing due to stress shielding. In this project, bio-compatible materials were studied for optimum stiffness for osteoporotic fixation plates. The plates, bone and screws were modelled in solidworks and FEA analysis of the Bone – Fracture model was done in solidworks and ANSYS. The FEA analysis shows that no single material plate can be used for fracture fixation in all the bones. For different range of bone loading, different material should be used for the plates. Plate Dimension – 100 x 20 x 5 mm, screw – 3 mm diameter cylinders. Bone – 30×40 mm thickness – 3mm ABSTRACT

PLATE MATERIAL CONTACT FORCE (model 1) (N) CONTACT FORCE (model 2) (N) N-

PEEK 50 55 30% glass fiber reinforced PEEK 55 55 50% glass fiber reinforced PEEK 70 60 30% carbon fiber reinforced PEEK 75 70 50% carbon fiber reinforced PEEK 110 100 Titanium alloy (6% Al and 4% V) 500 500 Load Range (N) Optimum Material 0 – 50 N – PEEK 50 – 75 carbon reinforced PEEK (upto 30% carbon by weight) glass reinforced PEEK (upto 50% glass by weight) 75 – 100 carbon reinforced PEEK (40% carbon fiber by weight) 100 – 200 Carbon reinforced PEEK (50%-60% carbon fiber by weight) 200 – 500 Titanium alloy (6% Al and 4% V) OBJECTIVES 

Material Selection: Essential Properties – • Biocompatibility • Elastic modulus(stiffness) • Chemical inertness • Density • Tensile strength • Compressive strength • Cost  Modelling: •Two models were studied: 1. Model 1 (with both cancellous and cortical bone) 2. Model 2 (without cancellous bone) Fig4: Bone – Plate system (ref 3) 

COMPUTER ANALYSIS

Base of the model is fixed, and a compressive load is applied , varying 10-1000N, on the top face downwards. Closing of the gap between the bone fragments was used as the stopping criterion, as this is the maximum movement we would want to see in the body.

METHODOLOGY

Based on properties required, four materials were selected:

 Titanium  PEEK (polyether-etherketone)  Carbon reinforced PEEK  Glass reinforced PEEK  FEA results Fig6 – Stress and Strain analysis results for model 1 Fig7 – Stress and Strain analysis results for model 2  Observations:

RESULTS CONCLUSIONS

The Loads acting on different bones are not same, so no single material can be used for a fixation plate for all the bones. We can vary the design parameters to get the required strength, for example, by decreasing the plate thickness we can reduce the contact force. The table below shows the optimum material dependent on the load range. This could be used to help surgeons select the correct material plates in different scenarios and for different patients.

REFERENCES

1. http://www.arthritiswa.org.au/content/page/osteoporosisoverview.html 2. http://www.surgeongeneral.gov/library/bonehealth 3. http://health.allrefer.com/pictures‐images/internal‐fixation‐ devices.html 4. http://www.matweb.com/search/DataSheet.aspx?MatGUID=26 493f911a174fb8b73b778730ea34f5&ckck=1 5. http://en.wikipedia.org/wiki/Wolff’s_law 6. http://www.professionalplastics.com/PEEKGLASSFILLED30 GF 7. http://www.ncbi.nlm.nih.gov/pubmed/16115079 ACKNOWLEDGEMENTS I wish to express my deep gratitude to my supervisor Dr Laura Leslie and Dr. Greg Swadener for their encouragement and guidance during the course of this summer internship. I would also like to thanks the Surgeons, Mr Kanthan Theivendran and Mr Subodh Deshmukh for their guidance during the project. To explore new materials that may mitigate, or reduce incidence of, problems associated with the current plates in osteoporotic bone. Aston University, UK R. Sharma, S. Deshmukh, K. Theivendran, L. Leslie , G. Swadener SURGICAL FIXATION PLATES FOR OSTEOPOROTIC BONES CONTACT DETAILS • In Osteoporosis, the cortical bone(outer bone) becomes thinner, making the bone weak and more prone to fracture. Fig1: Normal vs Osteoporotic Bone (ref 1) • Wolff’s Law states that bone in a healthy person or animal will adapt to the loads under which it is placed. If the loading on a bone decreases, the bone will remodel and becomes weaker, it is less metabolically. •Due to the mismatch in the stiffness of the plate and the bone, no load is transferred to the bone, leading to stress shielding. • Stress Shielding refers to the reduction in the bone density due to removal of normal stress from the bone by an implant. PLATE 100mm Cancellous bone Cortical bone 30×40 Titanium screws 1 mm gap between the bones THEORETICAL BACKGROUND Fig5: Bone-plate model Model after meshing For further details contact: Ravi Sharma ([email protected] ) Fig2: normal and osteoporotic bone (ref 2) Fig 3: Model -1