Humerus osteosynthesis in Green Iguana (Iguana iguana)

Resumo

Background: The Green iguana (Iguana iguana) is a reptile belonging to the Iguanidae family. It is an ectothermic animal with arboreal habits and a daytime activity pattern. Leaves, fruits, and eggs are part of their diet. These animals can be found in the South, North and Central America. Free-living Green iguanas may suffer stress during environmental changes, which can lead to a homeostatic imbalance. There is a correlation between stress and anorexia which results in an increase in the occurrence of fractures. Reptile fractures are generally treated by providing rigid stabilization and alignment maintenance. The present study reports the use of locking-plate osteosynthesis in one iguana.

Case: One female green iguana, weighing 1.690 kg, was assisted at the Hospital Veterinário Federal da Universidade Federal de Mato Grosso. During anamnesis, it was observed that this iguana was a non-captive animal, which had fallen from a tree. The animal was unable to perform physical movements with the forearm displaying bone crepitation. It was also observed apathy and dehydration. The iguana was subjected to a range of supplementary examinations and on the x-ray image, it was detected that there was a complete right humerus fracture. Following examination, the animal underwent surgery for fracture stabilization. Humerus osteosynthesis was performed with compression in a 1.5 mm 6-hole locking-plate. During the osteosynthesis procedure a morphogenetic graft was inserted. Immediate post-surgery radiographic evaluation was performed, and that confirmed fracture reduction and bone alignment. The animal displayed clinical improvement after the second post-operative day once it returned to regular ingestion of diet. On the 30th post-operative day, the radiographic evaluation showed evidence of bone consolidation. On the 40th post-operative day, the animal displayed satisfactory gait and voluntary ingestion of food, thus enabling its return to the wild.

Discussion: In this case study, the iguana displayed a satisfactory body condition score and good bone quality, which suggested a fall from a tree as the cause of the fracture, rather than a metabolic bone disorder. The osteosynthesis procedure followed the principles of orthopaedic surgery. The literature shows that there are reports of osteosynthesis being performed with the aid of intramedullary rod insertion. The intramedullary rods do not neutralize rotational forces, and thus are not recommended for the treatment of transverse fractures, like the one in the present study. A 6-hole 1.5mm locking-plate was inserted during osteosynthesis on this iguana. The protocol used was the one letting just the two middle-locking-plate holes free. This technique provided the advantage of fixation as a means of functional support once the power of the vascular system has not been damaged.  In this case study, a bone morphogenetic protein was used in order to induce the differentiation of mesenchymal cells into chondroblasts and osteoblasts. However, whether such a procedure influenced the consolidation of the bone fracture remains unsolved since it was not possible to assess owing to a lack of previous studies to determine the base parameters of the bone healing process in this species. It was observed that osteosynthesis with a locking-plate, effectively consolidated the humerus bone fracture of the Iguana iguana, and enabled its early return to the wild notwithstanding.