Longitudinal tear of the inferior rectus muscle in orbital floor fracture.

We report a case of longitudinal avulsion of the inferior rectus muscle following orbital floor fracture and describe its clinical presentation, computed tomography (CT) features and management. A 53-year-old man felt vertical diplopia in all gaze immediately after the trauma. Orthoptic assessment showed left over right hypertropia of 20 prism diopters and left exotropia of 10 prism diopters in primary position. The left orbital floor fracture and the prolapse of orbital contents into the maxillary sinus were presented by CT. Exploration of the orbit was performed under general anesthesia. The displaced bone fragment was elevated and repositioned below the slastic implant. Diplopia continued in all directions of gaze, although the impairment of depression was reduced postoperatively. A residual left hypertropia of 10 prism diopters and exotropia of 10 prism diopters was present in primary position 1 month after surgery, though there were no enopthalmos or worsening of hypesthesia. Repeated CT revealed the muscle avulsion of inferior rectus at the lateral portion of the belly. The avulsion of a small segment of the inferior rectus and its herniation into maxillary sinus in more posterior views was detected by review of the preoperative images. Muscle avulsion should be considered in the management of orbital fracture if orbital tissue entrapment and nerve paresis are excluded as causes of reduction in ocular motility. A thorough review of the imaging studies for possible muscle injury is required before surgery in all cases of orbital fracture.