Time-Dependent Changes in Resorbable Implants for Orbital Wall Fractures: Evaluation Using Orbital Volume Measurements

Resorbable implants are increasingly used in orbital wall fracture reconstruction because of their ability to provide temporary structural support without the long-term complications associated with permanent materials. However, the long-term effects of implant resorption on orbital morphology are unclear. This retrospective study evaluated volumetric changes over time following reconstruction using 2 types of resorbable plates: uncalcined hydroxyapatite/poly-L-lactic acid (u-HA/PLLA) and poly-L-lactic acid/polyglycolic acid (PLLA/PGA). Thirty patients with fresh orbital wall fractures were analysed using computed tomography (CT)-based orbital volume measurements at 3 time points: preoperative, early postoperative, and late postoperative (≥4 mo). Orbital volumes were calculated with Mimics software, and ocular protrusion was assessed to estimate enophthalmos. In the u-HA/PLLA group, the mean orbital volume difference decreased from 2.30±1.29 cm3 preoperatively to 1.10±0.58 cm3 immediately after surgery and remained stable at 1.17±0.63 cm3 during follow-up (P=0.2784 versus early). In contrast, the PLLA/PGA group initially showed improvement, which was followed by significant regression during follow-up periods. A significant correlation was observed between orbital volume differences and enophthalmos (P=0.004, R2=0.260). These findings indicate that PLLA/PGA implants may lead to morphologic regression, whereas u-HA/PLLA provides more stable outcomes. Implant selection should therefore consider long-term mechanical strength to ensure sustained structural integrity and optimal clinical results.