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Improving long-term stability of cemented total hip replacement - Part 1

PhD research student: Rajshree Mootanah
Supervisory team: Prof Paul Ingle, Prof Kevin Cheah, Prof John Dowell, Dr Julia Shelton (Queen Mary University of London)
Funding bodies: Chelmsford Medical Education and Research Trust - £ 15,800

Extracted failed hip implant

Extracted hip implant, showing failure at the neck of the cement peg

Total hip replacement operations have relieved patients with degenerative hip joints of pain and improved their quality of life. Although total hip replacements are successful operations, the rate of loosening of the cemented acetabular component increases exponentially from ten years post-operatively.

The author carried out a survey among orthopaedic consultants in the UK in 1999 to investigate the current practice in the fixation of the acetabular component. Although 94% of them perform cemented fixation, results showed wide variations in fixation techniques in terms of number, diameter and distribution of anchorage holes drilled and preservation or removal of the subchondral bone.

This study aims to improve the cement fixation techniques of the acetabular component and proposing designs of a special drill bit and jigs that would assist orthopaedic surgeons in preparing the acetabulum bed prior to cementation.

Stress distribution in the cement mantle near an anchorage hole

Stress distribution in the cement mantle in the hip joint near cement peg

Two-dimensional and three-dimensional finite element models of the reconstructed acetabulum were created to compare the stress distributions for the different methods of fixation of the acetabular component. The models were verified by carrying out torque resistance tests on simulated reconstructed acetabula. The results obtained suggested that keeping the subchondral bone and drilling three 12 mm diameter anchorage holes with chamfered necks perpendicularly to the acetabulum floor, one in each bone, with depth not exceeding the diameter gave the best results.

The designs of a special drill bit and a jig that would allow orthopaedic surgeons to drill three large anchorage holes perpendicuarly to the acetabulum floor were proposed. Another jig was also proposed for the deteriorated acetabulum that would give more flexibility in positioning the anchorage holes. An accurate three-dimensional model of the pelvis with geometry and material properties retrieved from CT-scan data has been developed for further work in this area.

Publications:
  • Mootanah, R. 2010, "Total Hip Replacement", LAP Lambert Academic Publishing, VDM Verlagsservicegesellschaft mbH, Germany, ISBN 978-3-8383-2679-5
  • Mootanah, R., Dowell, J.K., Cheah, K., Ingle, P., Shelton, J.C., 2008. "Configuration of anchorage holes affects cemented fixation of the acetabular component in total hip replacement - An in vitro study, Technology and Healthcare." 2008;16(1):19-30
  • Mootanah, R., Dowell, J.K., Cheah, K., Ingle, P, Shelton, J.C., 2007, "Configuration of anchorage holes affects fixation of the acetabular component in cemented total hip replacement-A finite element study", Computer Methods in Biomechanics and Biomedical Engineering, 10(6): 439-445
  • Mootanah, R., Ingle, P., Cheah, K., Dowell, J., & Shelton, J. 2004, "Total hip replacement: results of a postal survey of current practice on the cement fixation of the acetabular cup in the UK", Hip International, vol. 14, no. 3, pp. 155-162
  • Mootanah, R., Ingle, P., Cheah, K., Dowell, J., & Shelton, J. 2000, "Cemented fixation of the acetabular cup in total hip replacement: improving anchorage hole profile", Technology and Health Care , 8(6): 343-355
  • Mootanah, R. Lamvohee, J.M.S., Dowell, J. 2008, "Achieving uniform cement mantle of optimum thickness during orthopaedic surgery", Journal of Biomechanics, 41(1): 233
  • Mootanah, R, 2006, "Creation of accurate 3D models of reconstructed bones and joints for evaluations of surgical fixation techniques by finite element analysis", Journal of Biomechanics: The proceedings of the 5th World Congress of Biomechanics, Journal of Biomechanics, 39 (1):424
  • Mootanah, R. & Ingle, P. 2003, "Orthopaedic drill bit: Effect of diameter and point angle on cutting force and temperature rise", Journal of Bone and Joint Surgery, 86-B(3)
  • Mootanah, R., Ingle, P., Dowell, J., Cheah, K., & Shelton, J. 2002, "A survey of current practice on the cement fixation of the acetabular cup in total hip replacement", Journal of Bone and Joint Surgery supplement. -British Orthopaedic Research Society
  • Mootanah R, Ingle P, Allen E, Cheah K, Dowell J, Jarrett P, Shelton JC. 2002 "Total Hip Replacement: Improving the Cement Fixation of the Acetabular Component". Proceedings of the 13th conference of European society of biomechanics; Acta of Bioengineering and Biomechanics, 4(1): 600-01.
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