Growth prosthesis

Malignant bone tumors (osteosarcoma, Ewing's sarcoma) often occur in the growing child and require an interdisciplinary treatment concept, in which chemotherapy plays an important role and has decisively improved the prognosis of those affected. However, the tumor must always be surgically removed completely, leaving only healthy tissue. Whereas in the past amputations or disfiguring rotationplasty surgery were unavoidable, today there are much better alternatives in many cases, especially for children and adolescents of growing age. Since the survival rate has improved significantly, it is important to deal with reconstruction and the consequences after tumor removal at an early stage so that all options are open later.

It depends on the location of the tumor

The operation must be discussed at an early stage

Under the stress of a devastating diagnosis and stressful chemotherapy, there is unfortunately hardly any time to think about the operation and its consequences. Nevertheless, it is important to make the right decision, because after the tumor has been removed, a bony defect remains that should be biologically restored whenever possible. Depending on the procedure, both legs are the same length after the initial operation in the beginning, but the growth on the opposite side causes a leg length difference, the extent of which depends on whether a growth plate had to be removed and how old the affected child is at the time of the operation. It is important to decide on the proper course of treatment from the beginning.

Growth prostheses, the better alternative to rotationplasty

The BioXpand is the result of years of experience

The BioXpand was patented in 2002 and used in a patient for the first time in the world at ZEM-Germany in 2007. Startlingly good results were achieved with the first cases, encouraging further development of the system. The basic principle of the BioXpand, that the remaining bone can grow instead of the prosthesis, is implemented in all models. For this purpose, the prosthesis is first anchored with a polished shaft that does not grow into the bone, as initially both legs are still the same length. Further surgery is required only when the leg length difference has reached about 3-4 cm due to the growth of the opposite side. With the BioXpand I, an exposure or even a change of the prosthesis, and thus a "large" surgical exposure, is necessary for the change from the initial, polished socket to a FITBONE distraction nail and for any subsequent change, e.g. also to the definitive remaining, ingrowing socket after the end of growth. The associated risk of infection was drastically reduced with the introduction of the BioXpand II. While retaining all the advantages of BioXpand I, the BioXpand II requires only minimal surgical access, as all replacement procedures are performed from the opposite side of the bone to the prosthesis via a small skin incision (max. 3 cm) and the prosthesis itself remains virtually untouched. Initially, BioXpand II was only available for use in the femur (thigh). Prototypes for BioXpand III are already in development at ZEM-Germany, which will simplify revision surgeries even more, and make the device available for other areas in the body.

The treatment proceeds in several steps

In the case of malignant bone tumors, complete removal of the bone tumor and the surrounding soft tissues is still the priority in the primary operation, as the survival of the patient depends on this. If the decision has been made to use a BioXpand, an interim prosthesis with "smooth, polished" stems should always be used in the primary operation, which initially ensures optimum stability and later keeps all options open. It is also important to bear in mind that children are weakened by the chemotherapy at this stage, and the ultimate prognosis is not yet clear. The BioXpand is basically available for all common locations of malignant bone tumors in the lower extremities, i.e. for the proximal and distal femur and the proximal tibia. With the BioXpand II, all follow-up operations for lengthening at the femur can be performed in a minimally invasive technique via small incisions. In the future, the patented BioXpand III will make this possible in both the femur and the tibia, so that only once, during tumor resection, a large surgical approach is required, a prospect that seemed unthinkable until recently.

Even later, the BioXpand is still an option

In principle, it is always possible to change to a BioXpand if this results in a meaningful improvement in the treatment options for the affected child. If a polished stem has been inserted, a change is relatively simple. However, if the primary prosthesis was inserted with coated stems that have grown firmly into the bone, the indication to BioXpand must be carefully considered, since removal of these stems is only possible in an extremely invasive manner. This makes it all the more important to choose a reconstruction strategy from the outset that does not make subsequent treatment more difficult or impossible. Therefore, you should seek advice at ZEM-Germany even if the tumor operation is to be performed in another clinic.