An ideal situation in the management of bone tumours is when the disease can be successfully removed and the resulting loss of bone and muscle comp-ensated by a method that retains near normal limb function. This involves reconstructing large defects. The only option that offers both stability and mobility is a prosthetic joint repla-cement. Unfortunately the locally made prosthetic joints are not of very high standards and do not pay adequate attention to biome-chanics and material prop-erties. The imported joints, though of excellent quality, are prohibitively expensive. The Tata Memorial Hospital (TMH) therefore endea-voured to design and manufacture an indigenous high quality, affordable prosthesis.

To use the best currently available technology and expertise in developing affordable and high quality indigenous customized joints, the Tata Memorial Hospital started collaborating with a reputed quality implant manufacturer. The aim was to provide service to patients afflicted with bone cancer and make limb salvage using prosthesis available to a larger number of patients..

A megaprosthesis (replacement of joint by removal of large segments of bones and tissues) called the TMH-NICE (Tata Memorial Hospital New Indigenous Customised Endoprosthesis) was developed. Initially the knee prosthesis was developed as 70% of bone tumours occur around the knee. A design was evolved by the surgeons with the aim of recreating the normal anatomy. A separate left and right-sided joint was developed to account for the normal valgus angulation present. Hyper- extension of 5 degrees was built into the joint to allow passive locking during gait; and prevent buckling on loading even in patients with extensive muscle resectioin. A patellar groove is added to allow normal patellar tracking. to get better movement than in the earlier designs.

The portion replacing the bone was machined out of a single block of steel. This is because welding creates weak areas, which could break at loading. The dimensions were standardized for the Indian population. A special order sheet was developed to simplify ordering. A customized joint now takes 5 minutes to order compared to 30 min previously. Due to standardization, even during revisions, only the defective component needs to be changed saving cost as well as operating time and morbidity. Standardisation has also helped reduce fabrication time for the prosthesis.

Specialised instrumentation to facilitate and simplify implantation of the prosthesis has also been designed and fabricated. This helped to standardize surgical technique with subsequent decrease in surgical time and reduced incidence of intra operative complications.

Various innovations in the design - continuously evolving with increasing experience - have helped in increasing the longevity of the prosthesis.

This joint has now been successfully used in over 50 patients. The results as evaluated by the International Musculoskeletal Tumour Society System are similar to the ones as obtained with the imported prosthesis. During a follow-up period of 30 months, there had been only 1 implant failure. The range of motion is similar to that of the imported joint and the cost is only 10 %.

Encouraged by the success of the distal femur prosthesis, TMH also developed the proximal tibia replacement prosthesis, which is technically more complicated than the distal femur resection. With increasing experience the design of the tibial prosthesis has been radically changed to make it lighter and increase the range of motion possible. This joint has been used with excellent outcome.

Based on similar principles elbow replacement prosthesis, hip replacement prosthesis and shoulder replacement prosthesis have also been developed. Recently the entire humerus and femur were replaced at TMH with an indigenously designed humeral and femoral prosthesis.

TMH is now able to offer limb salvage to patients where the entire arm bone or thigh bone is affected by cancer. In these massive and challenging reconstructions, joints at both ends of the bone as well as the entire intervening segment are replaced with an endoprosthesis. This allows function superior to that after an amputation and external prosthesis, apart from the psychosocial advantage.

In an endeavour to make the joints lighter in weight, TMH is collaborating with MIDHANI (Mishra Dhatu Nigam Ltd.), Hyderabad to fabricate joints in titanium alloy. An added advantage is the MRI (magnetic resonance imaging) compatibility of titanium allowing to pick up recurrences earlier inspite of the presence of a metallic prosthesis.

TMH has developed a titanium shoulder joint. This prosthesis for the shoulder is now in routine clinical use and is MRI compatible, thus facilitating early diagnosis of recurrence.

At TMH, a modular titanium knee joint is also being developed. This will shortly be available for clinical use. This joint is half the weight of the stainless steel joint. To further improve the longevity of the joint, it must have a joint surface onto which bone can grow. In this direction, collaboration of TMH is on with IIT-Bombay and BARC to provide a hydroxyapatite coating for this purpose.