What Is the Best Candidate to Replace the Tarsus? A Biomechanical, Histological, and Optical Study Comparing Five Grafts

PURPOSE: Reconstruction of the posterior lamella after eyelid tumor removal is challenging and not consensual. Tarsus is the most suitable graft, but is only available in small amounts. Herein, we aim to determine the most appropriate way to replace the tarsus by comparing the biomechanical, histological, and optical properties of five commonly used grafts. METHODS: This study was conducted at the University hospital of Nice between June 2019 and June 2020. Five posterior lamella grafts (tarsus, conchal cartilage, sclera, hard palate, and dermis) were harvested in five fresh frozen cadavers. Biomechanical properties were assessed by tractometry. Collagen and elastin fibers were analyzed by using histological analysis and optical characterization with the second harmonic generation imaging. RESULTS: The mean Young's modulus was 8.92 MPa (range, 2.90–22.90 MPa), 1.05 MPa (range, 0.39–1.76 MPa), 8.72 MPa (range, 2.0–23.50 MPa), 2.57 MPa (range, 0.41–4.35 MPa), and 1.44 MPa (range, 0.71–2.30 MPa) for the tarsus, the conchal cartilage, the sclera, the hard palate mucosa, and the dermis, respectively. The mean tensile strength was 3 MPa (range, 1.70–6.88 MPa), 0.54 MPa (range, 0.13–0.79 MPa), 2.87 MPa (range, 1.23–5.40 MPa), 1.4 MPa (range, 0.21–2.40 MPa) and 1.0 MPa (range, 0.46–1.43 MPa) for the tarsus, the conchal cartilage, the sclera, the hard palate mucosa, and the dermis, respectively. Hard palate mucosa was the closest to the tarsus regarding the ratio of elastin and collagen fibers. The average second harmonic generation intensity was 221 arbitrary units (a.u.) (range, 165–362 a.u.), 182 a.u. (range, 35–259 a.u.), 369 a.u. (range, 206–533 a.u.), 108 a.u. (range, 34–208 a.u.), and 244 a.u. (range, 195–388 a.u.) for the tarsus, the conchal cartilage, the sclera, the hard palate mucosa, and the dermis, respectively. The hard palate mucosa and the dermis were the closest to the tarsus regarding the collagen fiber size and orientation, respectively. CONCLUSIONS: By attributing 2 points for each characteristic (biomechanical, histological, and optical), the hard palate mucosa and the sclera seem to be the most suitable grafts to replace the tarsus. TRANSLATIONAL RELEVANCE: The aim of this article was to assess the biomechanical, histological and optical characteristics of five of the most commonly used tarsal grafts; this may be helpful in decisions for clinical practice.