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Orbital Stress Analysis: Part III: Biomechanics of Orbital Blowout Fracture Repair Using Bioresorbable Poly-l/dl-Lactide (P[l/dl]LA 70:30) Implant

Al-Sukhun, Jehad PhD, MSc, BDS, ICOIF*; Penttilä, Heikki MD; Ashammakhi, Nureddin MD, PhD, FRCSEd‡§

Journal of Craniofacial Surgery: July 2011 - Volume 22 - Issue 4 - p 1299-1303
doi: 10.1097/SCS.0b013e31821c6ae9
Original Articles
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Purpose of the Study: The purpose was to study the biomechanics of bone fracture repair, of the orbital floor, using osteosynthetic bioresorbable implant and how to improve the implant design.

Materials and Methods: A finite element model of the orbit and the globe of 1 patient who experienced orbital blowout fracture and treated with bioresorbable poly-l/dl-lactide (P[l/dl]LA 70:30) implant (PolyMax; Synthes, Oberdorf, Switzerland) was generated based on computed tomographic scans. Simulations were performed with a computer using a commercially available finite element software. The effects of changing the geometry, bony support, and method of fixation of the implant on the finite element model predictions were investigated.

Results: The factor that had the biggest impact on the predicted principal strain magnitudes was absence of bony support of the implant (up to 65%). Applying elastic fixation reduced stresses (up to 40%) posteriorly. The principal stresses inside the bone and the implant were evenly distributed when elastic fixation was applied to the implant. Applying rigid fixation increased stresses (up to 50% and 80% anteriorly and posteriorly, respectively). The resulting stress values indicated a likely rapid failure of the osteosynthetic implant when rigid fixation was applied.

Conclusions: Applying rigid fixation induced a significant increase in stress patterns. Principal stresses were reduced remarkably when elastic fixation was applied to the implant. The role of fixation becomes more prominent when there is no bony support posteriorly and/or medially. It is recommended to avoid rigid fixation and to apply elastic fixation when using bioresorbable P(l/dl)LA 70:30 implants to reconstruct inferior orbital wall bony defects.

From the *Department of Oral and Maxillofacial Surgery, Euro-Oral Hammaslääkärikeskus Fredrikinkatu, Helsinki; †Department of Plastic Surgery, Kotka Central Hospital, Kotka; ‡Institute of Biomaterials, Tampere University, Tampere; and §Department of Surgery, Oulu University Hospital, Oulu, Finland.

Received January 12, 2011.

Accepted for publication February 5, 2011.

Address correspondence and reprint requests to Jehad Al-Sukhun, PhD, MSc, BDS, ICOIF, Department of Oral and Maxillofacial Surgery, Euro-Oral Hammaslääkärikeskus Fredrikinkatu 41A, 9 00330 Helsinki, Finland; E-mail: Jalsukhun@hotmail.com

The authors report no conflicts of interest.

© 2011 Mutaz B. Habal, MD