The dual mobility cup in muscular skeletal oncology: rationale and indications.

Purpose: Because of the improvement of medical therapy and the corresponding increase in life expectancy, orthopaedic surgeons are obliged to perform more wide resections rather than intramedullary stabilization nailing for patients affected by tumours of the hip compared to the past. Wide resection often causes joint instability, so prosthetic reconstruction presents a higher risk of dislocation than in primary osteoarthritis cases. The aim of the present paper is to classify the indications for the dual mobility cup (DMC) hip prosthesis based on the anatomic structures involved in the disease and to analyse the rationale to reduce the risk of dislocation.

Methods: Indications were analyzed and classified based on all the cases in which the DMC prosthesis was used for reconstruction after hip resection in an oncological research hospital.

Results: Four classes of indications were identified; for classes I and IV the indication for DMC prosthesis can be considered strong; for classes II and III the indications must be evaluated considering the specific case, based on life expectancy, performance status, presence of osteoarthritis, and availability of adjuvant local therapies. When the DMC prosthesis is indicated, the cup should always be cemented, either alone or with augmentation techniques, to decrease the risk of mobilization due to local disease progression.

Conclusions: DMC can be a valid alternative in reconstruction of the hip after tumor removal; nevertheless, prospective, randomized studies are necessary to verify the real dislocation rate based on the entity of resection.