In Vivo Degradation of Forged-Unsintered Hydroxyapatite and Poly-L-lactide Mesh Used for Orbital Reconstruction.

The aim of this study was to assess compositional changes in a forged-unsintered hydroxyapatite and poly-L-lactide (uHA/PLLA) mesh at 651 days after insertion into human body.A 35-year-old female patient had left tripod fracture, orbital medial wall and floor fracture, and superficial lateral palpebral ligament rupture. On the 9th posttrauma day, the tripod fracture was reduced and fixed with plates, and the orbital wall and floor were reconstructed with a resorbable mesh. The floor and medial wall were reconstructed with a trimmed mesh made of uHA/PLLA (Osterotrans-MX; Takiron Co, Umeda, Japan). On postoperative day 620, she complained of enophthalmos of left eye (right eye, 18 mm; left eye, 16 mm). Secondary reconstruction of the orbital floor was performed with an iliac bone graft 651 days after insertion. During the secondary operation, the uHA/PLLA mesh that had been previously inserted was removed. The mesh was removed and analyzed using gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR).The GPC revealed that the weight average molecular weight (Mw) decreased from 542,000 to 83,300 Da and the number average molecular weight (Mn) decreased from 124,000 to 20,200 Da in the specimen from the operation. In the postinsertion FTIR spectrum, weak 1648.6 and 1656.1/cm peaks newly appeared. The strong 1038/cm peak of the initial specimen changed slightly into a less strong 1041.8/cm peak.In conclusion, the reduced Mw and Mn in the postinsertion specimen suggest that uHA/PLLA has one of the favorable degradation properties. The newly appeared bands are thought to be carbon-carbon double bonds of alkenes.