Conservative surgical treatments for

osteoarthritis: A Finite Element Study

Diagarajen Carpanen, BEng (Hons), Franziska Reisse, BEng(Hons), Howard

Hillstrom, PhD, Kevin Cheah, FRCS, Rob Walker, PhD, Rajshree Mootanah,

PhD

Introduction

• Osteoarthritis (OA) : degenerative disease of all the tissues in

the di-arthrodial joint leading to pain, limited mobility and joint

deformation. (Coggon, et al., 2000)

• 14.1% of men & 22.8% of women over 45 years show symptoms

of OA of the knee. (Valkenburg, 1980)

• OA costs £12 billion to the NHS and $185.5 billion to the United

States annually. (Mathers, at al., 2006)

(Source: Arthritis Research, UK)

Common Causes of Knee Osteoarthritis

• Knee malalignment – 4x more prone to

develop OA. (Sharma, L., 2001)

• Joint injury - a torn meniscus or

ligament which can result from a twisting

injury ( football, skiing ). (Englund, et al., 2003)

Knee Mal-alignment

5 degrees of varus mal-alignment

=> 70% - 90% increase in

compressive loading in knee joint

=>resulting in OA

Meniscus & Meniscal Tears

Functions: Load bearing

and stabilisation

Four Basic Tears:

I - longitudinal;

II - horizontal;

III - oblique;

IV - radial (Source: Operative Orthopaedics, 2007)

• High tibial osteotomy (HTO) is a surgery aiming to relieve pain and

restore high-level function in active patients by re-aligning the lower limb

and lowering the contact stress in the knee joint.

• Partial meniscectomy is an arthroscopic surgical procedure commonly

performed to resect the injured part of the meniscus, to relieve

symptoms and restore knee function.

High Tibial Osteotomy &

Partial Meniscectomy

Gap in Knowledge

•The underlying link between malalignment and stress in the knee

compartment is not well understood. Also surgical realignment

outcomes by HTO have been unpredictable for unknown reasons

•Effects of resecting specific sizes and locations of meniscus on

knee joint contact stresses is not clear.

Methodology

CT scan /MRI

3- MATICS

Remesh ModuleSmooth surfaces,

Non-Manifold

assembly, meshing

MIMICS Modules

Image

processing,

generation of 3D

structure

FEA Package

Conversion of

mesh to solid

part & FEA

GE's Light Speed Plus Scanner (Courtesy of GE

Medical Systems)

• Cadaveric knee joint was CT-scanned,

using a GE Medical Systems CT-scanner.

• Slice thickness: 0.49mm

• Pixel size: 0.6 mm

CT Scan of the Knee

MRI of the Knee

GE Healthcare's Signa Excite HD 3T system

• MRI data acquired using 3T scanning systems.

• A combined 3D spoiled gradient recalled echo

(SPGR) and XETA sequence were used to create

accurate 3D models of the cartilage and meniscus,

respectively.(Mootanah et al., 2011)

• In-plane resolution: 0.29 mm x 0.29 mm.

3D Knee Model Development

CT Image MRI scan

Femur

FibulaTibia

Femoral Cartilage

Meniscus

Tibial Cartilage

Bones Soft Tissues

Image Registration of Osseous &

Soft Tissues

• 3D MRI model was registered to the 3D CT

model.

• Point and global registration techniques were

employed, using the minimum RMS error.

Non-manifold Assembly (NMA)

• NMA algorithm permits elimination of sections between surfaces.

• This ensures that a common border is calculated.

• Finally a volume mesh for NMA was created.

Preliminary FEA Studies

• Healthy knee

• Knee with a total

meniscectomy

• Knee with malalignment

Material Properties

employed

Young’s

Modulus

[MPa]

Poisson’s Ratio

Bones 1000 0.3

Cartilage 50 0.45

Meniscus 112 0.45

Ligaments 400 0.45

Source: Kubicek, M. and Florian,Z., 2009

Contact Definitions

Labelling Contact Pair

1 Tibial Cartilage - Meniscus

2 Femoral Cartilage - Meniscus

3 Femoral Cartilage - Tibial Cartilage

• Contact Surfaces are allowed to touch but not penetrate.

Boundary Conditions

Solve for stress at static equilibrium to

simulate standing on one leg:

1. Fix the distal tibia and fibula.

2. Apply axial load at the proximal femur .

3. Set constraints :

• Translation free in vertical direction only

• Flex/ext constrained to sagittal plane

• Other rotational degrees of freedom free

Preliminary Results

Intact knee ~ 2.6 Mpa

Total Meniscectomy ~ 4.9 MPa

Malaligned Knee ~ 4.2 MPa

P: posterior

A: anterior

M: medial

L: lateral

P

L

A

M

Conclusion

Preliminary findings show

• the importance of the meniscus in reducing knee joint

contact stresses.

• that malaligned knees are subjected to high stress levels

which indicates the importance of understanding realigning

(e.g. HTO) surgical techniques.

Further Works

• Simulation of HTOs and partial meniscectomies.

• Model cartilages and meniscus as visco-elastic materials.

• Model ligaments as hyper-elastic.

• Sensitivity analysis.

Coggon D, Croft P, Kellingray S, Barrett D, McLaren M, Cooper C. Occupational physical activities and osteoarthritis of the knee.

ArthritisRheum 2000; 43: 1443-9.

Englund, M., Roos, E. and Lohmander, L., 2003. Impact of type of meniscal tear on radiographic and symptomatic knee osteoarthritis: A

sixteen‐year followup of meniscectomy with matched controls. Arthritis & Rheumatism, 48(8), pp. 2178-2187.

Mathers CD, Loncar D. Projections of global mortality and burden of disease from 2002 to 2030. PLoS Med. 2006; 3:e442.

Mootanah, R., Imhauser, C., Koff, M., Potter, H. and Hillstrom, H., 2011. MRI Sequence Influences Geometrical Interpretation of Osseous

Tissues, Orthopaedic Research Society 2011.

Sharma, L. et al., The role of knee alignment in disease progression and functional decline in knee osteoarthritis. JAMA. 286 (2), 2001

Valkenburg H. Clinical versus radiological osteoarthritis in the general population. In: Peyron J (ed). Epidemiology of Osteoarthritis. Paris:

Ciba-Geigy, 1980:53-58.

References

Acknowledgement

• Supervisory Team: Dr Rajshree Mootanah, Dr Rob

Walker, Professor Kevin Cheah, Dr Howard Hillstrom

• The Higher Education Funding Council for England

• The Chelmsford Medical Education and Research Trust

For more information, please visit

www.anglia.ac.uk/medeng

Or contact:

rajshree.mootanah@anglia.ac.uk