Histologic analysis of costochondral and sternoclavicular grafts in the TMJ of the juvenile monkey

Variability in growth response of the mandible after replacement of the mandibular condyle with the costochondral junction of a rib (CCJ) is common. Other donor graft sites that are more similar to the mandibular condyle might be more suitable for mandibular condylar replacement. Previous studies have shown the histomorphologic and developmental similarities between the sternoclavicular joint (SCJ) and temporomandibular joint (TMJ). The purpose of this study was to evaluate histologically short-term adaptations within the TMJ after replacement of the mandibular condyle with the autogenous sternal head of the clavicle, and to compare these adaptations with autogenous CCJ and mandibular condyle (surgical control) transplants. Bilateral vertical ramus osteotomies were performed in 12 juvenile Macaca mulatta with the left condyle being immediately replaced and the right condyle removed and replaced with either the sternal head of the clavicle or costochondral junction of a rib. All grafts were stabilized with maxillomandibular fixation for five weeks. Two animals in each group were killed at five, 11, and 17 weeks postsurgery and prepared for histologic analysis. The results indicate that: 1) incorporation of all grafts into the recipient site occurred and all animals had good mandibular function and occlusion throughout the follow-up period; 2) the clavicular and mandibular condylar grafts were incorporated sooner than the CCJ grafts; 3) clavicular graft changes resembled those of the condylar grafts histologically while the costal grafts remained inert and unchanged; and 4) a new condylar process with cartilage similar to that of a normal mandibular condyle regenerated in the costal graft animals from cells presumably contributed by the periosteum of the mandibular ramus and TMJ capsule. These results indicate that the SCJ may be more suitable for mandibular condylar replacement than the CCJ, especially since individuals on whom such grafting procedures are contemplated are usually young persons who have compromised joints with a disrupted periosteum and decreased osteogenic potential.