The aim of this study was to elucidate the supporting strength of the curved
poly-L-lactic acid (PLLA) sheet and porous
polyethylene (
Medpor) for reconstruction of orbital floor fractures. For one-half and two-thirds orbital floor fractures, reconstruction was performed using the PLLA sheet and
Medpor. The PLLA sheet was molded to fit the orbital floor (concavity). The anterior portion (1 cm) was curved to fit the inferior orbital rim and fixed with a screw.
Medpor was designed to fit the orbital floor. A screw was fixed 6 mm away from the anterior border of the orbital floor. Each implant was hung by wire, and the degree of sagging of the implant was measured using micrometers by the power of a force gauge. For one-half orbital floor fractures, the power of the PLLA sheet to sag 5 mm was 2.46 (SD, 0.14) N, and that of
Medpor was 0.59 (SD, 0.04) N. The power of the PLLA sheet to sag 10 mm was 6.9 (SD, 0.14) N, and that of
Medpor was 1.52 (SD, 0.16) N. For two-thirds orbital floor fractures, the power of the PLLA sheet to sag 5 mm was 1.79 (SD, 0.24) N, and that of
Medpor was 0.39 (SD, 0.04) N. For 10 mm of sagging, the power of the PLLA sheet was 5.61 (SD, 0.29) N, and that of
Medpor was 0.94 (SD, 0.09) N. For sagging of 15 mm, the power of the PLLA sheet was 8.99 (SD, 0.16) N, and that of
Medpor was 2.98 (SD, 0.24) N. The PLLA sheet was irreversibly bent when the force reached approximately 8 to 9 N. For
Medpor, the degree of sagging during the early stage was larger than at the later stage. In all situations, the supporting power of the PLLA sheet was greater than that of
Medpor. The differences were significant in all situations (P = 0.000). The degree of sagging in one-half orbital floor fractures was 2.87 mm for the PLLA sheet and 7.96 mm for
Medpor. There was an increased orbital volume of 0.4 mL with the PLLA sheet and 1.19 mL for
Medpor. The predicted
enophthalmos was 0.41 mm with the PLLA sheet and 1.07 mm with
Medpor. The degree of sagging for the two-thirds orbital floor fractures was 4.28 mm for the PLLA sheet and 11.47 mm for
Medpor. The increased orbital volume was 0.78 mL for the PLLA sheet and 2.22 mL for
Medpor. The predicted
enophthalmos was 0.73 mm with the PLLA sheet and 1.93 mm with
Medpor. The predicted
enophthalmos was below 2 mm with both the PLLA sheet and
Medpor for reconstruction of orbital floor fractures; however, it was near 2 mm with
Medpor in reconstruction of two-thirds orbital floor fractures. The results of this study show that the PLLA sheet and
Medpor were sufficient for reconstruction of one-half and two-thirds orbital floor fractures with a defective posterior part. However, the supporting power of the PLLA sheet was stronger than that of
Medpor.