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Entrapment of inferior rectus muscle as a complication of sinus balloon expansion for maxillary sinus fracture


Blunt facial or orbital trauma may cause fracture of the orbital or sinus walls. The most common type of orbital fracture is blow out fracture in which the inferior rectus muscle or orbital soft tissues attached to the muscle are entrapped within the orbital floor fracture.1 In cases of blow out fracture, treatment usually consists of exploring the orbital floor and releasing the entrapped tissue. For additional fractures, different approaches exist that include sinus expansion for compressed sinus fractures.2 This technique has been applied also to blow out fractures. Muscle entrapment is a potential complication of sinus expansion by balloon catheterization, although it has never been described according to literature search with Medline® using the terms muscle entrapment, sinus fracture, sinus expansion, and balloon catheterization.

We present a patient who had an inferior rectus muscle entrapment as a result of sinus expansion by balloon catheterization for treating a compressed sinus fracture.

Case report

A 39-year-old male was injured in his face from a pipe spanner. On examination, the patient had swelling of the right cheek and right eyelids haematoma. Visual acuity was 20/20 in each eye. The intraocular pressure was normal in each eye. Ocular motility and convergence were full without complaints of diplopia. The ocular anterior and posterior segments were normal. A computed tomography (CT) examination of the orbits, without contrast media on a 16–MDCT scanner (Brilliance, Philips Medical System, Cleveland) showed right anterior, medial, and lateral compressed maxillary sinus wall fractures and a fracture of the right orbital floor without soft tissue entrapment (Figure 1a and b). Small bone fragments were detected within the sinus as well as blood (haemosinus). The patient was place on amoxycillin 500 mg and clavulinic acid 100 mg i.v. t.i.d. and underwent Caldwell–Luc surgery to correct the compressed maxillary sinus fracture. During surgery, the compressed fracture was exposed. Free small bony fragments and blood clots were removed. Foley balloon catheter was placed and inflated within the maxillary sinus expanding the sinus space. Prednisone 1 mg/kg i.v. was added.

Figure 1

(a) A coronal CT scan of a 39-year-old patient injured from pipe spanner. Fracture of the orbital floor (short arrow) without entrapment of orbital soft tissue or inferior rectus (arrowhead) as well as haemosinus are noted. (b) A sagittal CT scan of the showing a normal course of the inferior rectus muscle within the orbit.

Following surgery, the patient complained of diplopia. The catheter was deflated and removed. The diplopia persisted and limitation of right supraduction to 30° was noted with positive forced-duction test. CT of the right orbit showed a disrupted course of the inferior rectus muscle in the orbit and stretching toward the orbital floor fracture due to entrapment of the inferior rectus sheath within bone fragments of the orbital floor (Figure 2a and b).

Figure 2

(a) A coronal CT scan of the same patient after Foley balloon catheterization demonstrating stretching of the inferior rectus muscle (arrowhead) toward the orbital floor fracture (short arrow) abutting bone fragments (long arrow). (b) A sagittal CT scan after Foley balloon catheterization showing a disrupted course of the inferior rectus muscle in the orbit and stretching toward the orbital floor fracture (‘deflection sign’). Orbital floor exploration disclosed entrapment of the inferior rectus muscle sheath within the orbital floor fracture.

The patient underwent exploration of the orbital floor and the entrapped inferior rectus muscle was released. Following surgery, the patient resumed full ocular motility.


Balloon sinus expansion is one option for treatment of compressed sinus fracture. Complications of this procedure are rare and include necrosis of sinus mucosa and infection. In this patient, entrapment of the inferior rectus muscle within orbital floor fracture was a complication of this procedure. This complication has never been described although injuries to the inferior and medial rectus muscles have been described following endoscopic sinus surgery and Caldwell–Luc operation in a patient with hypoplastic maxillary sinus.3, 4, 5

We termed ‘deflection sign’ the disrupted course of the inferior rectus muscle in the orbit and stretching toward the orbital floor fracture on sagittal CT of the orbit. The possible mechanism for muscle entrapment is muscle displacement into the fracture when the sinus was expanded allowing its entrapment by some deflation. High intraorbital pressure due to active bleeding into the orbit may further increase the displacement of the muscle through the bony fracture.

Balloon sinus expansion should be employed cautiously or avoided in the presence of orbital floor fracture. When employed, inflation should be slow and gradual and deflation should be avoided. Removal of the balloon may be delayed until complete healing. Otherwise, other open-system or endoscopic procedures may be preferred because they allow direct visualization of the surgical site.


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Correspondence to S Rumelt.

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Rath, E., Goldfeld, M., Samet, A. et al. Entrapment of inferior rectus muscle as a complication of sinus balloon expansion for maxillary sinus fracture. Eye 21, 97–99 (2007).

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