Evaluation of computer-based volume measurement and porous polyethylene channel implants in reconstruction of large orbital wall fractures

PURPOSE. To describe the use of computer-based orbital volume measurement as a predictor of late enophthalmos, and to assess the effectiveness of the MedPor (Porex Surgical Products Group, Newnan, GA) porous polyethylene channel implant to restore orbital volume in repairing large orbital wall fractures. METHODS. Sixteen patients with unilateral large orbital fractures were included. Computed tomographic (CT) scans were used to obtain computer-based orbital volume measurement to predict the likelihood of late enophthalmos and to assess the change in orbital volume before and after surgery. The effectiveness of a channel implant was evaluated by the orbital volume and postoperative exophthalmetric measurement. RESULTS. The average time interval between injury and surgery was 17.4 +/- 10 days, and the mean follow- up was 9 months. The orbital volume of the injured orbit was significantly increased ( mean, 4.22 +/- 2.61 cm(3)) compared with the unaffected orbit before surgery (t = 3.046, P = 0.005). There was not a significant difference in orbital volume between the two orbits after orbital reconstruction ( t = 0.069, P = 0.945). The orbital volume change after reconstructive surgery was significantly positively correlated with the decrease of enophthalmos (r = 0.715, P = 0.001; enophthalmos [E] = 0.72; volume increment [ V] = 0.06). To resolve 2 mm enophthalmos, more than 2.9 cm(3) orbital volume augmentation is recommended for early reconstructive surgery. Postoperative CT scan showed most of the channel implants to be well positioned. CONCLUSIONS. Computer-based orbital volume measurement from a CT scan is useful in the posttraumatic evaluation of orbital fractures, and it can help predict the degree of late enophthalmos that can be expected. Orbital reconstruction with the MedPor channel implant ( Porex Surgical Products Group), when indicated, is recommended, especially for large orbital wall fractures.