Prognostic CT findings of diplopia after surgical repair of pure orbital blowout fractureā˜†

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Abstract

Purpose

Diplopia is a common sequela of blowout fracture even after proper surgical management. We investigated the prognostic factors of diplopia after surgery of pure blowout fracture.

Materials and methods

We retrospectively reviewed CT images of 181 patients with pure orbital blowout fracture who underwent at least six months of postoperative follow-up. We evaluated the following CT factors: (1) fracture site (orbital floor, medial wall of the orbit, or both), (2) fracture type (closed flap, open flap), (3) fracture size, (4) volume of herniated orbital soft tissue, (5) ratio of volume of herniated orbital soft tissue to fracture size, (6) number of points of contact between extraocular muscle (EOM) and bony edge, (7) presence of EOM thickening, (8) EOM swelling ratio, (9) presence of displacement of EOM, (10) presence of deformity of EOM, (11) presence of tenting of EOM, and (12) presence of entrapment of EOM. The associations between diplopia at six months after surgical repair and various risk factors were analyzed using logistic regression models for univariable and multivariable analyses.

Results

EOM tenting and deformity and ratio of volume of herniated orbital soft tissue to fracture size were found to be statistically significant risk factors of diplopia at six months after repair on univariable analysis (all PĀ <Ā 0.05). Patients who showed EOM tenting or deformity on CT images had 5.22 and 10.85 times greater probability of diplopia after surgery, respectively (P-value, <0.001 and 0.026; 95% confidence interval of odds ratio, 2.071ā€“13.174 and 1.323ā€“88.915, respectively). On the other hand, ratio of volume of herniated orbital soft tissue to fracture size was not significant on multivariable analysis (PĀ =Ā 0.472).

Conclusion

The prognosis of patients was predicted by CT evaluation. Patients who have tenting or deformity of EOM on CT scan are more likely to have postoperative diplopia.

Introduction

Orbital fractures are a common component of facial trauma. Orbital blowout fracture (BOF), a subtype of orbital fracture, refers to a fracture involving only the orbital inferior and/or medial wall, with an intact orbital rim. The fracture typically occurs after blunt trauma to the orbit. Sequelae of BOF include enophthalmos, diplopia, infraorbital nerve anesthesia, disfiguring facial contours, and tearing from obstruction of the nasolacrimal duct (Harris etĀ al., 2000, Burnstine, 2002). The goal with orbital wall reconstruction is to improve visual function and orbital appearance. However, even after proper surgical management, ocular motility disturbance and diplopia persists in 9ā€“30% of patients (Cope etĀ al., 1999; Harris etĀ al., 2000, Hosal and Beatty, 2002, Gosau etĀ al., 2011). Diplopia results from deformity of the orbit (causing positional changes of the muscles), adhesive impingement of the content (disturbing ocular excursion), or impairment of the contracting muscle (resulting from neurogenic or myogenic palsy) (Yano etĀ al., 2010).

Many prognostic factors have been implicated in diplopia (Harley, 1975, Hawes and Dortzbach, 1983, Gilbard etĀ al., 1985, Lyon and Newman, 1989, Biesman etĀ al., 1996, Folkestad and Westin, 1999, Okinaka etĀ al., 1999; Harris etĀ al., 2000, Hosal and Beatty, 2002, Furuta etĀ al., 2006, Jin etĀ al., 2007, Tahiri etĀ al., 2010, Matsunaga etĀ al., 2011, Hwang etĀ al., 2012, Neinstein etĀ al., 2012). Several studies have analyzed CT findings associated with diplopia after surgical management (Harris etĀ al., 2000, Furuta etĀ al., 2006, Jin etĀ al., 2007, Tahiri etĀ al., 2010, Matsunaga etĀ al., 2011). Furuta etĀ al. (2006) reported that fracture type and number of extraocular muscle (EOM) contact points with the fracture edge on multiplanar reconstruction CT images are important prognostic indicators of ocular motility. Harris etĀ al. classified blowout fractures based on soft tissue distortion relative to bone fragment configuration and noted that fracture type influences postoperative motility (Harris etĀ al., 2000). Jin etĀ al. (2007) demonstrated that EOM swelling on CT is associated with a higher incidence of residual diplopia after surgery and seems to be a reliable prognostic factor of postoperative diplopia. Matsunaga etĀ al. (2011) also reported that diplopia and impairment of eye movement after surgery tends to remain in the patients with EOM swelling on preoperative CT images. Tahiri etĀ al. (2010) reported that initial EOM injury leading to EOM swelling and preoperative diplopia seems to be the origin of diplopia after surgical repair of pure BOF. However, these studies evaluated the relationship between only one or two CT findings and postoperative diplopia. Therefore, the aim of this study was to evaluate various CT findings and determine possible prognostic factors leading to new or persistent diplopia after surgical repair of pure BOF.

Section snippets

Patients

The institutional review board approved this study, and the informed consent requirement was waived for this retrospective review.

Between January 2007 and October 2014, a search of the electronic database of our hospital revealed 488 patients who underwent surgical repair for orbital fractures. Among them, 306 patients were excluded from the study group using these exclusion criteria: (1) postoperative follow-up period shorter than six months (nĀ =Ā 217), (2) revision surgery (nĀ =Ā 40), (3)

Results

The patients in this study included 134 (74.0%) males and 47 (26.0%) females, aged 4ā€“71 years (mean, 27.5 years). Most of the patients (164, 90.6%) were injured through a low-velocity mechanism. Before surgery, 138 patients (76.2%) complained of diplopia, 38 patients (21.0%) presented with enophthalmos, and 74 patients (40.9%) had abnormality of ocular motility. The mean interval between trauma and surgery was 14.8 days (range; 1ā€“151) in all enrolled patients, 17.0 days (range; 2ā€“151) in

Discussion

Diplopia is an indication for repair surgery after BOF but remains a common sequela of BOF even after proper surgical management. Diplopia results from injury to the anatomical structure of the orbit including EOMs and/or functional impairment of EOM movement. The rectus EOMs originate in the annulus of Zinn, which is a common fibrous ring surrounding the optic nerve in the orbital apex. The rectus EOMs run anteriorly through loose, areolar lobules of orbital fat without mechanical constraint,

Conclusions

This study provides prognostic CT findings of postoperative diplopia in patients who underwent surgical repair for pure BOF. Patients who had EOM tenting or deformity on CT scan were more likely to have postoperative diplopia. Injury and fibrosis of the connective tissue framework and subsequent muscular adhesions may play a role in diplopia.

Funding

None.

Conflict of interest

None.

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    The authors declared that they did not receive any grant from others.

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