The Macaca rhesus monkey skull and surgical intervention

CT anatomy and normal radiography of the skull of the Rhesus monkey (Macaca mulatta)

BACKGROUND

Considering the relationship between human morphology and physiology with the Rhesus monkey, this animal is the most prominent species of laboratory primate for human and animal health research. Moreover, sending Macaca mulatta monkey into space and simulating a living environment for humans shows the similarity of this animal's physiology with humans.

OBJECTIVE

So far, no comprehensive study has been done on computed tomography (CT) scan and radiography of skulls in Rhesus monkeys. Therefore, providing accurate documents from the CT anatomy of the skull in these animals can help us to better understand normal conditions and diseases, and we can use a functional atlas of diagnostic imaging from the skull of this animal.

METHODS

Ten mature monkeys weighing 6.5 kg were used for this project (five males and five females). A radiographic examination with standard views was performed during general anaesthesia. Then the monkeys were placed in a spherical CT scan during general anaesthesia with standard sternal recumbency.

RESULTS

The frontal bone was seen as two parallel radiopaque lines coming forward and downward. The frontal sinus in the Rhesus monkey was not visible in both lateral and dorsoventral radiographs, which could indicate the degeneration of this sinus in this species. The number of teeth in an adult monkey was 32. Molar teeth had a bilophodont arrangement.

CONCLUSIONS

The comparison between the size of the eye ball in human and Rhesus monkey, unlike other measured parameters, did not differ much, and this indicates that the volume ratio of the eye ball to the whole skull in Rhesus monkey is higher than that of humans.

Growth of the mandible after replacement of the mandibular condyle: an experimental investigation in Macaca mulatta

PURPOSE

The study goal was to investigate growth of the mandible after temporomandibular joint reconstruction in juvenile monkeys.

MATERIALS AND METHODS

Sixteen juvenile monkeys (Macaca mulatta) were used as experiment subjects. Animals were equally divided into 4 experimental groups based on the method of temporomandibular joint reconstruction after bilateral condylar excision via extraoral vertical ramus osteotomies. Group Condyle animals had their condylar segments immediately replaced to serve as surgical controls. Group Bone animals were reconstructed with a bony strut. Group sternoclavicular joint (SCJ) animals were reconstructed with the sternal end of their clavicles. Group costochondral junction (CCJ) animals were reconstructed with costochondral junction of ribs. Standardized lateral cephalometric radiographs with the aid of tantalum bone markers were used to evaluate mandibular growth. Twenty animals were used as controls and were allowed to grow undisturbed for an 18-month period (Group Control).

RESULTS

All animals showed good mandibular function and a Class I molar relationship after an 18-month follow-up period. Statistical and graphic comparisons showed no significant difference in mandibular growth among any of the groups.

CONCLUSIONS

The results of this investigation suggest that, within the limits of this model, the choice of autograft for condyle replacement may be irrelevant.

Facial asymmetries following unilateral condylar replacement. An experimental study in monkeys using metatarsal transplants

The aim of the present study was to evaluate qualitatively and quantitatively the effect of metatarsal transplantation on the mandibular condylar region. Two series of experiments were performed in four groups of Rhesus monkeys, a fifth group served as a nonoperated control group. The surgical procedures involved either the condyle and part of the ramus or the condyle only. Following the postoperative observation period the skulls of the animals were examined macroscopically, measured anthropologically and measured indirectly on vertical cephalograms. A new method developed by the authors for description of facial asymmetries was used. In all of the operated animals well-functioning joint structures were revealed, though all experimental groups showed the classical deformation features. Continued growth of the transplant was observed in only one case. The facial asymmetries were described as angular deviations from the true symmetry axis. No significant difference between the transplant and the corresponding nontransplant groups was detected for the two kinds of resection performed. However a difference in the degree of asymmetry between the ramus resection group and the condylectomy group was seen. It is concluded that a metatarsal transplant does not prevent the development of facial asymmetry following plain condylectomy or resection of the posterior third of the ramus of the mandible including the condyle.