Replacement of the Condyle and Ascending Ramus by a Modular Endoprosthesis in Macaca fascicularis—Part 2: Microcomputed Tomographic and Histologic Evaluation of the Ramus and Stem

Purpose

The present study presents the microcomputed tomographic and histologic evaluation of the peri-implant tissues of a modular endoprosthesis used to replace the condyle and ascending ramus in Macaca fascicularis.

Materials and Methods

The right condyle and ascending ramus were resected in 8 adult monkeys and replaced by a modular endoprosthesis, fixed with polymethylmethacrylate bone cement (Palacos). Four monkeys were sacrificed at 3 months and 4 at 6 months postoperatively. Microcomputed tomographic scanning was performed to analyze the bone volume at the bone–cement interface. Histologic and histomorphometric assessments were done using a modified hard and soft tissue grading scale and by studying the total bone contact at the interface.

Results

The combined (buccal, lingual, and inferior) mean bone volume percentage of the 6-month group was significantly greater than that of the 3-month group (P < .05). The 6-month specimens showed a reduced inflammatory response and more abundant bone formation around the stem. The total soft tissue histologic score was significantly greater in the 6-month group (P < .05). A total bone contact percentage of 15.4% to 85.2% was achieved in 3 specimens.

Conclusions

Satisfactory bone growth was found at the bone–cement interface at the stem region, although direct bone contact with the cement was not achieved in all cases. Soft tissue contact with the prosthetic ramus, in the form of a fibrous capsule, was present in some areas. At 6 months, minimal interfacial inflammation was found in this monkey model.