Influence of an interdental full pin on stability of an acrylic external fixator for rostral mandibular fractures in dogs

OBJECTIVE

To determine total stiffness and gap stiffness of an external fixation system in a canine mandibular fracture gap model incorporating a full interdental pin as the only point of rostral fixation in a bilateral type-I external fixator.

SAMPLE POPULATION

10 canine mandibles.

PROCEDURE

Bilateral mandibular ostectomies were performed between premolars 3 and 4. A type-I external fixator incorporating a full interdental pin was placed to stabilize a 0.5-cm fracture gap. Four pin configurations (intact mandibular bodies with fixator; ostectomized mandibular bodies and complete fixator; ostectomized mandibular bodies with caudal pins of rostral fragment cut; ostectomized mandibular bodies with all pins of rostral fragment cut) were tested in dorsoventral bending 5 times on each mandible. The full interdental pin remained intact in all configurations. Total stiffness and gap stiffness were determined for each configuration on a materials testing machine.

RESULTS

Total stiffness of intact mandibles was significantly greater than that of ostectomized mandibles, regardless of external fixator configuration. However, total stiffness and gap stiffness were not significantly different among different external fixator configurations applied to ostectomized mandibles.

CONCLUSION AND CLINICAL RELEVANCE

External fixator configurations with only the full interdental pin engaging the rostral fragment were as stiff as configurations that had 2 or 4 additional pins in the rostral fragment for the applied loads. External fixators for rostral mandibular fractures may be rigidly secured with rostral fragment implants applied extracortically, avoiding iatrogenic trauma to teeth and tooth roots.

Extraskeletal osteosarcoma in the duodenum of a cat

A three-year-old, male neutered domestic longhair cat was referred for evaluation of icterus, vomiting, and anorexia. Abdominal ultrasonography revealed a proximal duodenal mass obstructing the common bile duct. The mass was surgically resected, and a cholecystoduodenostomy was performed. The histopathological diagnosis was osteosarcoma. Thoracic radiographs showed no evidence of metastasis, and bone scintigraphy revealed no signs of a primary skeletal osteosarcoma. Four months after surgery, the cat had intermittent vomiting, marked weight loss, and died.

INTERRELATIONSHIP OF COMB LOCI AND MATING BEHAVIOR IN CHICKENS

Qualitative and quantitative data obtained from lines of chickens divergently selected for male mating ability and from the unselected randombred control population were used to evaluate the relationship of comb type alleles and mating behavior. An apparent antagonistic relationship was found between the rose (R) allele and low cumulative number of completed matings in the low mating line, while the opposite association was found for the pea (P) allele. No association was found between alleles of the rose and pea loci and mating ability in the high mating or control lines. An antagonistic relationship was indicated between the rough (He+) allele and a high cumulative number of matings. These results support the hypothesis that two genetical systems interact to influence the mating frequency of male chickens and further suggest that alleles of the rose, rough, and pea loci should not be used as marker genes to estimate genetic drift in random mating populations maintained by natural matings.