Isolated inferior rectus muscle rupture after blunt orbital trauma
A 44-year-old man was referred to our department with a monocular hematoma, swelling and diplopia. He was punched in the area of the left orbit the day prior during a violent conflict.\nThe clinical examination revealed a left-side periorbital swelling and monocular hematoma with significant subconjunctival haemorrhage. A vertical diplopia with restriction of infraduction was also observed (Fig. . Additionally, he presented with hyperopia. The palpation of the underlying bone showed no bony step-off of the orbital rim. A preoperative ophthalmological evaluation confirmed the vertical diplopia, and showed an isolated IR muscle underaction with deficiency of depression in abduction, as well as a vertical deviation in primary position.\nComputed tomography (CT 1 mm slices) presented a large, left-orbital floor fracture with caudal dislocation of the bone fragment and prolapse of the IR muscle and orbital fat into the maxillary sinus (Fig. a). Transection or disinsertion of the IR was not described.\nPreoperative forced-duction testing indicated mild restriction in the vertical upward direction, suggesting an entrapment of the IR muscle. Uneventful surgery via a transconjunctival incision was performed under general anaesthesia. The intraoperative finding showed a huge defect of the bone. Therefore, the entrapped orbital tissues were lifted out of the fracture, repositioned and a titanium mesh was inserted for repair of the orbital floor (Fig. b).\nFour days after surgery, despite good resolution of swelling, there had been essentially no change in the clinical–functional deficit and vertical diplopia persisted due to restriction of infraduction.\nA postoperative CT scan showed a good position of the titanium mesh, as well as repositioning of herniated tissues, but highlighted a tear of the IR muscle in its middle part.\nAccordingly, the preoperative CT scan was re-evaluated in 0.5 mm slices and the pre-existence of the ruptured IR was shown (Fig. . After ophthalmological consultation and treatment of the patient with a combination of orthoptics and prismatic glasses, satisfactory functional recovery was achieved after 6 months without need of surgical repair of the ruptured muscle.