Background: Mandibular modular endoprosthesis fixed with polymethylmethacrylate cement in the medullary space of the mandible to reconstruct segmental defects has been introduced in previous studies. However, device loosening and wound dehiscence have been reported.

Objective: In vivo study of a newly designed non-cemented Ti6Al4V modular endoprosthesis.

Methods: Endoprosthesis stems designed as hydroxyapatite coated tapered screws allow fitting into mandibular bone stumps without cementation. The body has a dove-tailed interlock with hydroxyapatite/bioglass surface coating. The devices were implanted for 6 months at unilateral mandibular segmental defects in 9 monkeys. Analysis was performed using biomechanical testing, histological and Micro CT analysis.

Results: Mandibular contour and initial stability were satisfactory immediately post operation. 6 months after reconstruction, mechanical load bearing test showed mean stiffness value of 110.43 N/mm. Histomorphology analysis found 64.17% bone to stem contact. There was fibrous capsule and woven bone around the device body. Percent bone volume calculated from Micro-CT around the stem surface was found to be superior to previously reported cemented mandibular endoprosthesis. However, intraoral wound dehiscence was found in 6 animals.

Conclusions: This newly designed mandibular endoprosthesis has potential in mandibular segmental reconstruction. Further modification to reduce wound dehiscence is required.

Key words: mandible; endoprosthesis; bioglass; hydroxyapatite