Quantitative assessment of increase in orbital volume after orbital floor fracture reconstruction using a bioabsorbable implant

Purpose: To assess the postoperative changes in the orbital volume and the degree of enophthalmos after orbital floor fracture reconstruction using a bioabsorbable implant and to determine the predictors of postoperative orbital volume change. Methods: Single-center, retrospective case series of 16 patients who underwent orbital floor fracture reconstruction using a bioabsorbable implant [poly(L-lactic acid)–poly(glycolic acid)/β-tricalcium phosphate; Biobsorb β^®] were included. Three-dimensional volumetric calculations of orbit were determined using computed tomography scans and the degree of enophthalmos was assessed via Hertel exophthalmometry. Postoperative changes in the orbital volume and the degree of enophthalmos and their correlation were assessed. Results: The mean volume of fractured orbits immediately after surgery was 22.26 ± 1.98 cm³, increasing to 23.67 ± 2.00 cm³ at 6-month follow-up (p < 0.001); the increased orbital volume was associated with postoperative deformation of the implant. The mean degree of enophthalmos was 0.09 ± 0.27 mm at 1-month follow-up, which increased to 0.66 ± 0.30 mm at 6-month follow-up (p = 0.001). Increase in orbital volume and enophthalmos progression showed a linear correlation (R = 0.682, p = 0.004). Patients with more herniated orbital tissue preoperatively showed increased postoperative orbital volume change (p = 0.015), whereas the size of the fracture area was not predictive of postoperative orbital volume change (p = 0.442). Conclusion: Increase in orbital volume by deformation of the bioabsorbable implant resulted in progressive enophthalmos during the postoperative follow-up period after orbital floor fracture reconstruction. Thus, careful selection of proper implants before surgery and close postoperative follow-up is needed for an optimal outcome.