Application of poly-L-lactide screws in flat foot surgery: histological and radiological aspects of bio-absorption of degradable devices
P. Sena1, G. Manfredini2, C. Barbieri2, F. Mariani2, G. Tosi3, B. Ruozi3, M. Ferretti1, L. Marzona1 and C. Palumbo1
1Department of Biomedical Sciences-Section Human Morphology, 2Orthopaedic and Traumatologic Clinic, University Hospital, 3Department of Pharmaceutical Sciences and University of Modena and Reggio Emilia, Modena, Italy.
Offprint requests to: Prof. Carla Palumbo, Human Anatomy Associate Professor, University of Modena and Reggio Emilia, Department of Biomedical Sciences, Section of Human Morphology, c/o Instituti Anatomici (Area Policlinico), Via del Pozzo nº 71, 41125 Modena, Italy. e-mail: email@example.com
Summary. The flat foot in childhood is a condition frequently observed in orthopedic practice but it is still debated when and in which patients surgical corrective treatment is appropriate; recently, the application of poly-L-lactic-acid (PLLA) screws was proposed. The present study investigates a group of 33 patients treated with PLLA expansion endorthesis in order to evaluate the deformity correction. Clinical and radiological outcomes in patients were correlated with: a) morphological characterization of screws both before and after being removed from patients, when necessary; b) histological and bio-molecular evaluation of degradation processes of the implants, focusing attention on the correlation between the cellular cohort involved in inflammatory reaction and the bio-absorption degree of PLLA screws. Deformity correction was mostly achieved, with minimal need of screw removal; the results obtained clearly show the occurrence of chronic rather than acute inflammation in removed screw specimens.
At the histological level, after biomaterial implantation, the sequence of events occurring in the surrounding tissues ultimately ends in the formation of foreign body giant cells (FBGCs) at the tissue/material interface; but the mechanisms which influence the fate of screw implants, i.e. the resolution of acute inflammation rather than the progression towards chronic inflammation, are of crucial importance for biodegradable materials like “polylactic acid”. In fact, the FBGC response ensures a long-term mechanism which eliminates the foreign material from the body, but at the same time the implications of prolonged FBGC responses, which generate negative side effects, could significantly impede the healing progress. Histol Histopathol 27, 485-496 (2012)
Key words: PLLA screws, Flat foot, Bio-absorption, Histological analysis