Clinical Applications

Hip, shoulder or other joint replacement/refurbishment

Inventors

The surgical kit has been developed at the Institute of Orthopaedics and Musculoskeletal Science at The Royal National Orthopaedic Hospital (University College London), by Professor Gordon Blunn, Professor Allen Goodship and Fang Sze-Ching

Background and Technology Summary

In conventional hip replacement surgery (total hip replacement) the surgeon replaces the femoral head and reams out the acetabulum prior to insertion of a prosthetic acetabulum. In some cases the hip is repaired by hemiarthroplasty in which the femoral head only is replaced and the acetabulum is left substantially untouched with the natural cartilage still in place. A major problem with total hip replacements is that the artificial bearing surfaces of the acetabulum wear during use until the replacement hip joint needs repair. It is desirable to defer or avoid this problem completely because the repair process involves a major surgical procedure with the associated discomfort and risk to the patient.

The technology developed at UCL consists of a surgical kit that is suited for performing a hip hemiarthroplasty, in which a femoral head is fitted directly into a socket reamed into the acetabular without any permanent liner or prosthetic acetabular being implanted. This methodology will therefore alleviate the requirement for prosthetic acetebular replacement, and the associated problems of repeat surgery to implant a new prosthetic acetebular

A reamer is used to ream out the acetabulum until cancellous bone is exposed so that it bleeds liquid containing stem cells. By selecting the size of the femoral head in accordance with the characteristics of the patient, the pressure imposed on the liquid/ synovial fluid of the joint is in the range between 0.5 and 2MPa. The stem cells within the liquid are, as a result of the pressure, encouraged to form chondrocytes which grow into cartilage lying on the subchondrial bone which provides a natural active bearing surface for the femoral head, rather than relying on a rigid wholly prosthetic bearing comprising a rigid acetabular shell prosthesis as used in total joint replacement, and giving a better refined joint than a conventional hemiarthroplasty. In order to further promote the formation of cartilage resorbable spacers can be provided to separate the surface of the femoral head and the reamed acetabulum. Alternatively, a resorbable/or removable membrane which suitably conforms to the shape of the surface of the femoral head and the reamed acetabulum can be used to provide a uniform and widely spread transfer of loading between the femoral head and the acetabulum.

In a further aspect of the surgical kit technology, a non- invasive reaming procedure for joint refurbishment has been developed which is particularly useful where neither the head of the femur nor the acetabular surface needs to be fully replaced. In this instance, a unique double-sided reamer head is used, having reamer cutting teeth facing not only outwardly toward the acetabular surface but also inwardly toward the femoral head surface. Both of those two surfaces may be simultaneously reamed to be thoroughly compatible with each other.

Competitive Advantage o Replacement of the hip without the requirement for implanting a prosthetic acetabular. o In cases where both the head of the femur or the acetabular surface do not need to be fully replaced, the double sided reamer technology provides a superior procedure to ensure joint bearing surfaces are thoroughly compatible.

Dr Paul Burrows Business Development Manager UCL BioMedica p.burrows@uclbiomedica.ucl.ac.uk

WO2004069062 At PCT Stage

Licensing