Primary Osteoarthritis
We have identified significant changes in the subchondral bone of
patients with osteoarthritis of the hip and are currently investigating
the nature of these changes in more detail using a variety of physical
methods. We have proposed a new hypothesis for generalised osteoarthritis
that it is a systemic, metabolic disorder. This tries to explain the
involvement of multiple joints and the strong link with obesity. The
biological origin of these changes is being studied using cultured
cells from patients with osteoarthritis or osteoporosis, as well as
cell lines. However, until we solve that one, cement fixation of the
acetabular component of a total hip replacement is a significant but
under-researched problem. We showed that drilling wide shallow keyholes
is better than deep narrow ones for increasing the strength of the
fixation. In addition, we have shown that the capsular ligaments are
important structures in the hip and may play a fundamental role in
stabilising the upright posture. Finally, we have extended our shape
modelling studies to OA and a pilot study has suggested that we
can identify individuals who will go on to develop OA before they
can be detected using conventional (Kellgren / Lawrence scoring) methods
and it may also provide a means of assessing disease progression.
Secondary Osteoarthritis
Impact loads on joints, such as experienced in trauma, are a recognised
cause of secondary osteoarthritis. We have built a drop tower, instrumented
with an accelerometer and a force transducer to investigate the mechanical
interplay between the cartilage and the underlying bone during such
loading. This system is also being modelled using finite element methods.
The response of the cells to impacts of varying severity is being
investigated to determine the ability of the tissue to start a repair
process and the affects of apoptosis and necrosis on the effectiveness
of that process (publications).
Osteoporosis
Novel methods of analysing and characterising radiographs
and DXA images are being developed to try to increase our ability
to measure changes in bone quality. There appear to be changes in
the shape of the proximal femur which
are strongly related to osteoporotic fractures of the femoral neck
and identification of these is proving almost as good as bone mineral
density measurements for predicting fracture. We have also developed
novel methods for describing the trabecular
structure in bones and monitoring changes over time. Combining
these two measures with DXA (Dual energy absorptiometry) measurements
of bone mineral density (BMD) enabled to us to obtain complete identification
of fracture and non-fracture groups in a pilot study.
Mechanotransduction and tissue engineering
We have built a number of devices for applying mechanical stimuli
to cells in vitro and are using these to study the responses of osteoblasts
and chondrocytes. Connective tissues rely on mechanical stimuli to
maintain a functional tissue matrix but still relatively little is
known of how these signals are detected and transduced into synthesis
of matrix molecules. We found that chondrocytes from elderly human
cartilage do not behave in the same way as those from young bovine
tissue). Both cyclic and static loading reduced matrix biosynthesis
compared with unloaded controls, in contrast to most studies which
have shown that cyclic loading is stimulatory. Mechanical loads also
cancelled the effect of IGF-1 stimulation and a pilot gene array study
is indicating the presence of novel factors not previously identified
in the signalling process.
Modelling of tissues as fibre composite materials is showing how
tapered fibres, which is how collagen fibres appear in many tissues,
are advantageous for maximising stress transfer while minimising the
metabolic cost of the materials. They also reduce the risk of fibre
fracture by removing the highest axial stresses from the centre of
the fibre towards the ends (Link).
Spinal Biomechanics
There is also an interest in spinal biomechanics and two novel models
have been proposed to provide a better explanation of the load-bearing
function of the spine. The first considers the spine to function as
an arch-like structure and shows that in this way the closeness of
the muscles to the spinal axis enables stability to be ensured while
minimising the axial and shear stresses. The other shows how by controlling
the axial stiffness of the spine it can be considered as an Euler
pendulum (an inverted form of pendulum where the mass is above the
support) and in this way can maintain stability while enabling precise
control of movement. These models indicate how the curved flexible
structure of the spine provides some unique advantages for the upright,
bipedal human stance.
Recent papers
K.L. Goh, J.R. Meakin, R.M. Aspden and D.W.L. Hukins. Stress transfer in collagen fibrils reinforcing connective tissues: effects of collagen fibril slenderness and relative stiffness.
Journal of Theoretical Biology , in press.
K.L. Goh, R.M. Aspden and D.W.L. Hukins. Shear lag models for stress transfer from an elastic matrix to a fibre in a composite material.
International Journal of Materials & Structural Integrity , in press.
L.V. Burgin and R.M. Aspden. A drop tower for controlled impact testing of biological tissues
Medical Engineering and Physics 29 : 525-530, 2007.
J.E. Jeffrey and R.M. Aspden. The biophysical effects of a single impact load on human and bovine articular cartilage.
Proceedings of the Institution of Mechanical Engineers, part H: Journal of Engineering in Medicine 220 : 677-686, 2006.
 Doi: 10.1243/09544119JEIM31
M.S. Plumb, K. Treon and R.M. Aspden. Competing regulation of matrix biosynthesis by mechanical and IGF-1 signalling in elderly human articular cartilage in vitro .
Biochimica et Biophysica Acta 1760 : 762-767, 2006.
Doi:10.1016/j.bbagen.2006.01.019
R.M. Aspden, K.E. Rudman, and J.R. Meakin. A mechanism for balancing the human body on the hips.
Journal of Biomechanics 39 : 1757-1759, 2006.
Doi: 10.1016/j.jbiomech.2005.04.028
L. Yao, C.S. Bestwick, L.A. Bestwick, N. Maffulli, and R.M. Aspden. Phenotypic drift in human tenocyte culture.
Tissue Engineering 12 : 1843-1849, 2006.
DOI: 10.1089/ten.2006.12.1843
K.E. Rudman, R.M. Aspden, and J.R. Meakin. Compression or tension? The stress distribution in the proximal femur. BioMedical Engineering OnLine 2006, 5 :12.
J.R. Meakin and R.M. Aspden. Static and dynamic stability of the spine.
Journal of Biomechanics 39 (15): 2919-2920, 2006.
Rahmatallah, S., Li, Y., Seton, H. C., Gregory, J. S., & Aspden, R. M. 2005, "Measurement of relaxation times in foodstuffs using a one-sided portable magnetic resonance probe", European Food Research and Technology 222 (3-4): 298-301, 2006
J.S. Gregory, A. Stewart, P.E Undrill, D.M. Reid and R.M Aspden. Bone shape, structure and density as determinants of osteoporotic hip fracture: A pilot study investigating the combination of risk factors
Investigative Radiology 40 : 591-597, 2005
L.D. Mkukuma, C.T. Imrie, J.M. Skakle, D.W.L. Hukins and R.M. Aspden. Thermal stability and structure of cancellous bone mineral from the human femoral head of patients with osteoarthritis or osteoporosis. Annals of the Rheumatic Diseases 64 : 222-225, 2005.
T.L. Stewart, P. Roschger, B.M. Misof, V. Mann, P. Fratzl, K. Klaushofer, R. Aspden, and S.H. Ralston. Association of COLIA1 Sp1 Alleles with Defective Bone Nodule Formation In Vitro and Abnormal Bone Mineralization In Vivo .
Calcified Tissue International 77 : 113-118, 2005
K.L. Goh., J.R. Meakin, R.M. Aspden, and D.W.L. Hukins. Influence of fibril taper on the function of collagen to reinforce extra-cellular matrix.
Proceedings of the Royal Society B272 : 1979-1983, 2005.
S. Rahmatallah, Y. Li, H.C. Seton, I.S. Mackenzie, J.S. Gregory and R.M. Aspden. NMR detection and one-dimensional imaging using the inhomogeneous magnetic field of a portable single-sided magnet.
Journal of Magnetic Resonance 173 : 23-28, 2005.
M.S. Plumb and R.M. Aspden. The response of elderly human articular cartilage to mechanical stimuli in vitro.
Osteoarthritis and Cartilage 13 : 1084-1091, 2005.
J.S. Gregory, A. Stewart, P.E Undrill, D.M. Reid and R.M Aspden. Identification of hip fracture patients from radiographs using Fourier analysis of the trabecular structure: a cross-sectional study
BMC Medical Imaging , 4:4, 2004.
K.L. Goh, R.M. Aspden, K.J. Mathias and D.W.L. Hukins. Finite element analysis of the effect of material properties and fibre shape on stresses in an elastic fibre embedded in an elastic matrix in a fibre composite material.
Proceedings of the Royal Society A460 : 2339-2352, 2004.
L.D. Mkukuma, J.M.S. Skakle, I.R. Gibson, C.T. Imrie, R.M. Aspden and D.W.L. Hukins. Effect of the Proportion of Organic Material in Bone on Thermal Decomposition of Bone Mineral: an Investigation of a Variety of Bones from Different Species using Thermogravimetric Analysis coupled to Mass Spectrometry, High-Temperature X-ray Diffraction and Fourier Transform Infra-Red Spectroscopy.
Calcified Tissue International 75 : 321-328, 2004.
Gregory, J. S., Testi, D., Stewart, A., Undrill, P. E., Reid, D. M., & Aspden, R. M. "A method for assessment of the shape of the proximal femur and its relationship to osteoporotic hip fracture", Osteoporosis International, 15: 5-1, 2004
J.M. Somerville, R.M. Aspden, K.E. Armour, K.J. Armour and D.M. Reid. Growth of C57Bl/6 mice and the material and mechanical properties of bone. Calcified Tissue International 74: 469-475, 2004.
M.S. Plumb and R.M. Aspden. High levels of fat and (n-6) fatty acids in cancellous bone in osteoarthritis.
Lipids in Health and Disease 3 : 12, 2004.
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