Residual Limb Model for Osteointegration - Computational Biomechanics of the Musculoskeletal System - page 170

mesh density, and applied loading. The limitation of using a standardized femur is that it is not
patient-specific; however, the modeling methodology developed in this study allows comparative
assessment of different loading regimens on a well-defined femur-implant geometry.
Another limitation of the FE model was the use of linear and homogeneous bone material prop-
erties. In reality, there is likely to be a combination of damaged bone, new woven bone transformed
from hematoma, and some fibrous tissue at the interface after the surgical implantation. Future stud-
ies with patient-specific femur geometry derived from CT scans may also include patient-specific
bone properties; however, the focus of this study was a comparison of relative stress levels between
different loading cases. The tied contact interface between the implant and the bone did not permit
any relative motion between the implant and the bone, thus simulating the limiting case of complete
osseointegration. This assumption is consistent with the observation of close apposition between the
bone and the implant during the six months from the initial implantation surgery to the commence-
ment of loading after the second surgery. However, there is much potential for a better understand-
ing of the mechanical properties of the osseointegrated bone-implant interface through histological
studies and mechanical testing.
reFerenCeS
Aschoff, H., and Grundei, H., 2004. The Endo- Exo-Femurprosthesis: A new concept of prosthetic rehabilitation
engineering following thigh-amputation: Some cases and early results. Proceedings of the International
Society for Prosthetics and Orthotics 11th World Congress , Hong Kong SAR.
Brånemark, R., Brånemark, P.-I., Rydevik, B.L., and Myers, R.R., 2001. Osseointegration in skeletal reconstruc-
tion and rehabilitation: A review. Journal of Rehabilitation Research and Development 38(2):175-81.
Brånemark, R., Ohrnell, L.-O., Skalak, R., Carlsson, L., and Brånemark, P.-I., 1998. Biomechaical charac-
terization of osseointegration: An experimental in vivo investigation in the beagle dog. Journal of the
Orthopaedic Research Society 16(1):61-9.
Cairns, N.J., Frossard, L. A., Hagberg, K., and Branemark, R., 2006. Static load bearing during early rehabilita-
tion of transfemoral amputees using osseointegrated fixation. Proceedings of the 30th Annual Scientific
Meeting of the International Society for Prosthetics and Orthotics , pp. 51-52, Perth, Australia.
Carter, D.R., and Hayes, W.C., 1977. The compressive behavior of bone as a two-phase porous structure. The
Journal of Bone and Joint Surgery. American Volume 59(7):954-62.
Frossard, L., Beck, J., Dillon, M., Chappell, M., and Evans, J.H., 2003a. Development and preliminary test-
ing of a device for the direct measurement of forces and moments in the prosthetic limb of transfemoral
amputees during activities of daily living. Journal of Prosthetics and Orthotics 15(4):135-42.
Frossard, L., Lee Gow, D., Contoyannis, B., Nunn, A., and Branemark, R., 2003b. Load applied on the abut-
ment of transfemoral amputees fitted with an osseointegrated implant during load bearing exercises using
a long pylon. Proceedings International Society for Prosthetics and Orthotics-Australia , pp. 55-56,
Melbourne, Australia.
Gallagher, P., Allen, D., and MacLachlan, M.I., 2001. Phantom limb pain and residual limb pain following
lower limb amputation: A descriptive analysis. Disability and Rehabilitation 26:522-30.
Hagberg, K., and Brånemark, R., 2001. Consequences of non-vascular trans-femoral amputation: A survey of
quality of life, prosthetic use and problems. Prosthetics and Orthotics International 25:186-94.
Hagberg, K., Häggström, E., Uden, M., and Brånemark, R., 2005. Socket versus bone-anchored trans-femo-
ral prostheses: Hip range of motion and sitting comfort. Prosthetics and Orthotics International 29(2):
153-63.
Helgason, B., Viceconti, M., Rúnarsson, T.P., and Brynjólfsson, S., 2008. On the mechanical stability of porous
coated press fit titanium implants: A finite element study of a pushout test. Journal of Biomechanics
41(8):1675-81.
Lee, W.C.C., Doocey, J.M., Frossard, L., Branemark, R., Pearcy, M.J., and Evans, J.H., 2008. FE stress analysis
of the interface between the bone and an osseointegrated implant for amputees: Implications to refine the
rehabilitation program. Clinical Biomechanics 23(10):1243-50.
Lee, W.C.C., Frossard, L., Hagberg, K., Haggstrom, E., and Brånemark, R., 2007. Kinetics analysis of trans-
femoral amputees fitted with osseointegrated fixation performing common activities of daily living.
Clinical Biomechanics 22(6):665-73.