[Alloarthroplasty versus above-knee amputation]

We report an unusual case of a 38-year-old physically active patient, who suffered a Ewing sarcoma during adolescence and was therefore treated with a tumor endoprostheses ex domo (replacement of distal femur and proximal tibia). Since then he had undergone a couple of surgical interventions for revision and is currently suffering from persistent pain in the leg concerned. An aseptic loosening of the tibial component was evident after radiologic examinations. Because he had suffered for so long our patient refused further surgery to retain the affected limb and he preferred amputation.

We would have taken the risk of a femoral residual limb that is much too short compared with a classical above-knee amputation. In this regard we saw difficulties in exoprosthetic treatment with functional limitations that could easily have influenced the outcome negatively.

Consequently, we decoupled the tibial component from the femoral one within the knee joint and thus performed a knee disarticulation leaving the femoral component.

Postoperatively, we found a mostly harmonious gait pattern with a pure mechanical interim prosthesis regarding time-distance parameters, which may be even further improved with the final prosthesis. Sagittal joint angles are comparable to conventionally knee exarticulated ones.

To date, no comparable case of such an alloarthroplasty, which could regain mobility with an exoprosthetic treatment has been highlighted in the literature. In the result, a knee disarticulation within the area of a knee arthroplasty leaving the femoral component is not inferior to"ordinary" knee disarticulation.