Abstract
Primary bone tumours are rare and account for only 1% of cancer deaths. The commonest area for tumour occurrence is around the knee. With the advent of chemotherapy and improved survivorship of patients with osteosarcoma and Ewings of the extremities, excision of the primary lesion and reconstruction has become both a viable and routine option in specialist centres.
The surgical options include; excision alone, or excision and reconstruction with Autograft or allograft, or using massive prostheses to fill the defect.
In the UK, we have developed and used massive endoprostheses to fill the defect made following tumour excision and I would like to report our experience.
The first report of the use of massive endoprostheses was by Seddon & Scales in 1949 at The Royal National Orthopaedic Hospital, Stanmore. Since then both the number primary and revision procedures has continued to grow on a yearly basis. In the year 2000 we carried out 95 primary massive endoprosthetic replacements and 27 revisions.
In terms of functional score (Musculoskeletal Tumour Soc), following excision of tumours of the lower limb including excision of the affected joint, results are superior in those patients who undergo reconstruction using an endoprostheses (87%), as opposed to reconstructions using either osteoarticular allograft (68%), or rotationplasty (85%).
The long term survivorship of prosthetic replacement varies enormously between the upper and lower limbs due to the different forces acting upon them, indeed revision for aseptic loosening in the upper limb is rare.
In the lower extremity the probability of survivor-ship of a cemented proximal femoral replacement at ten years is 93.8%, whilst those for the distal femur or proximal tibia using a fixed hinge (Stanmore Mk4) are 67.4% and 58% respectively. The two factors that have a huge bearing on this are; the age of the patient and the amount of the diaphysis of the long bone resected.
To try and improve the long-term fixation of implants we have used porous coated collars at the prosthesis bone interface. These were first used in 1988, however subsequent retrieval specimens showed only fibrous tissue ingrowth although initial x-rays were thought to be encouraging.
Hydroxyapatite coated collars were first used in 1989 and have become standard use in all endoprosthetic replacement since. Indeed, retrieval specimens have revealed good bone ingrowth and no delamination of the HA.
Another huge advance has been the introduction in 1991 of the rotating hinge for implants of the distal femur and proximal tibia.
Subsequent studies have shown a significant reduction in aseptic loosening in distal femoral replacements which have both an HA collar and incorporate a rotating hinge.
Since 191 we have also developed fully uncemented endoprosthetic replacements for our younger patients with a satisfactory outcome. These results will be discussed.
In the future we hope to make further developments in the area of the non-invasive growing prosthesis, and soft tissue attachment around prosthesis especially those of the proximal humerus and the proximal femur.
The abstracts were prepared by Professor Jegan Krishnan. Correspondence should be addressed to him at the Flinders Medical Centre, Bedford Park 5047, Australia.
