Association between preoperative inferior rectus muscle swelling and outcomes in orbital blowout fracture

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Abstract

Purpose

In 18 patients with orbital blowout fracture who underwent reconstruction using a bone autograft, the association between preoperative inferior rectus muscle swelling and the outcome 1 year after the operation was evaluated.

Material and methods

The patients were classified according to outcomes into four groups: Group A without double vision showing normal ocular movements, Group B with double vision showing normal ocular movements, Group C with double vision showing improvement in ocular movements, and Group D with double vision showing no improvement in ocular movements. Inferior rectus muscle swelling was evaluated by calculating its swelling rate on the injured compared with the non-injured side on preoperative coronal CT images.

Results

Concerning outcomes, 12, 2, and 4 patients were classified as Groups A, B, and C, respectively, and no patient was classified as Group D. The inferior rectus muscle swelling rate was ≤1.2 in Group A, and 1.6–2.4 in Groups B and C.

Conclusion

In patients in whom inferior rectus muscle swelling on the injured is ≥1.6 times that on the non-injured side on preoperative coronal CT images, double vision and slight impairment of eye movements may remain after surgery.

Introduction

In orbital blowout fracture, impairment of eye movements often persists after surgery. One of the possible causes may be extraocular muscle injury (Smith et al., 1984, Gilbard et al., 1985, Lisman et al., 1987, Watanabe et al., 2000, Oba et al., 2001, Kase, 2007). We (Matsunaga et al., 2009) previously evaluated outcomes 1 year after the surgery in patients with orbital blowout fracture who underwent reconstruction using a bone autograft, and reported marked swelling of the extraocular muscle close to the fracture site on preoperative CT images as a finding common to patients in whom impaired eye movements remained.

However, there have been no studies on objective preoperative evaluation methods for prediction of the postoperative impairment of eye movements. Therefore, we objectively evaluated inferior rectus muscle swelling on the injured side in comparison with that on the non-injured side on preoperative CT images in 18 patients with blowout fracture of the orbital floor who underwent reconstruction using a bone autograft, and analyzed the association of this swelling and remaining double vision or impaired eye movements after the surgery.

Section snippets

Subjects

Among orbital blowout fractures, those showing punched out type bone defects with a maximum width  20 mm are treated by reconstruction using a bone autograft in principle at our department. We performed operations employing a previously reported technique (Matsunaga et al., 2009). Fig. 1 summarizes the surgical methods. At first, we performed a subciliary incision and determined the fracture site in the orbital floor. We removed bone fragments and repaired the orbital tissue (Fig. 1a), inferior

Classification of postoperative outcomes

Table 4 presents findings on HESS tests and outcomes 1 year after surgery in each patient. According to the outcome 1 year after the surgery, 12 cases (66.7%) were classified as Group A, 2 (11.1%) as Group B, and 4 (22.2%) as Group C, with no case in Group D. In Group A, the interval until double vision disappeared was varied with individual and raged from 1 month to 1 year postoperatively.

Evaluation of inferior rectus muscle swelling by preoperative CT

Figs. 3a, 4a and 5a present slice images showing the most marked swelling of the inferior rectus muscle on

Discussion

The reported factors associated with a poor prognosis in surgically treated patients with orbital fracture include: (1) extraocular muscle injury (Smith et al., 1984, Gilbard et al., 1985, Lisman et al., 1987, Watanabe et al., 2000, Oba et al., 2001, Kase, 2007), (2) preoperative severe double vision (Kase, 2000, Watanabe et al., 2000, Lee et al., 2005), and (3) young patients (de Man et al., 1991, Watanabe et al., 2000, Burnstine, 2002, Kamijo et al., 2005, Kwon et al., 2005). Concerning

Conclusion

In 18 patients with orbital blowout fracture who underwent reconstruction using a bone autograft, the association between preoperative inferior muscle swelling and the outcome 1 year after surgery was evaluated. In patients in whom the preoperative cross-sectional area of the inferior rectus muscle on the injured was ≥1.6 times that on the non-injured side, double vision or slightly impaired eye movements may remain after surgery.

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