gms | German Medical Science

Objectives: The occurrence of malignant bone tumors of the femur is extremely rare in children under the age of 8, but demands a challenging surgical treatment. In general, limb salvage approaches are preferable over ablative procedures. However, (extendable) tumor endoprostheses can often not be applied in small children due to anatomical conditions. While custom-made endoprostheses represent an alternative option for joint replacement, they do not provide the intraoperatively required variability regarding reconstruction length. Allo- and autograft replacements are well-studied procedures, but are associated with high complication rates. While rotationplasty has shown satisfactory functional results, it remains cosmetically unfavorable. We therefore present a new technique for limb reconstruction in young children suffering malignant bone tumors of the femur.

Methods: We conducted a retrospective chart review of 4 children (2 girls, 2 boys) aged 3, 4 (n=2) and 8 years with osteosarcoma (n=2) and Ewing's sarcoma (n=2) of the femur who underwent limb salvage treatment by MUTARS^® Humero pro Femur joint replacement. Radiological evaluation was performed on standardized anteroposterior and lateral radiographs. The functional outcome was assessed by applying the MSTS score. The mean follow-up time was 3.2 years.

Results and conclusion: Total femur resection was performed in 1 patient, while3 patients underwent intraarticular distal femur resection. Femoral reconstruction was conducted using modular components of the MUTARS^® system (implantcast, Buxtehude, Germany). After 180° sagittal rotation, a MUTARS^® distal humerus component was implanted to serve as a hinged distal femur, allowing flexion of the knee joint of up to 100°. The tibial component was custom-made in all cases. Diaphyseal reconstruction was achieved with standard modular humeral components of the MUTARS^® system.

Figure 1 [Fig. 1]

Surgical revisions with exchange of modular components were performed in 3 patients, of whom 2 were revised to gain length, and 1 due to periprosthetic joint infection. 1 patient with total femur replacement showed increasingly insufficient containment of the hip joint, requiring triple pelvic osteotomy 5 years after initial surgery.

1 patient succumbed to disease 1 year after surgery. The surviving 3 children were able to bear with full weight and fully extend the knee, while flexion ranged from 60–90° at the time of last follow-up. Mean MSTS score was 21.75.

MUTARS^® Humero pro Femur joint replacement permits limb-salvage treatment until application of an extendable tumor endoprosthesis is anatomically feasible. However, revision surgery will in most patients become necessary at some point due to sustained growth of the limb.