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[Effect of porous polyethylene channel implants on volume reconstruction of large orbital wall fractures evaluated by computed tomography measurement].

OBJECTIVE
To assess the clinical effectiveness of porous polyethylene medpor channel implants (MCI) to restore orbital volume in repairing orbital wall fractures, evaluated by computed tomography (CT) and volume measurement program.


METHODS
Sixteen patients with unilateral large orbital fractures were included in this study. Computed tomography (CT) scans were used to obtain computer-based orbital volume measurement to assess the change in orbital volume pre- and post-operatively. Pre- and post-operative enophthalmos were measured using a Hertel exophthalmometer. The average time interval between injury and surgery was (17.4+/-10.0) days, and the mean follow-up period was 9 months.


RESULTS
Postoperative CT scan showed that most of the MCI to be well positioned. The orbital volume of the injured orbit was significantly increased [mean: (28.16+/-4.32) cm3] as compared with unaffected orbit preoperatively (t=3.044, P<0.01). There was no statistical difference in orbital volume between the injured and normal orbits after orbital reconstruction (t=0.069, P>0.05). The orbital volume change after reconstructive surgery was significantly positively correlated with the decrease of enophthalmos (r=0.715, P<0.01). In order to resolve 2 mm enophthalmos, more than 2.86 cm3 orbital volume augmentation is recommended.


CONCLUSIONS
Orbital volume measurement by CT scan is useful in the post-traumatic evaluation of severity of orbital fractures, and it can help predict the degree of late enophthalmos. Orbital reconstruction with the MCI, when indicated, is recommended.