Evaluation of the effect of osteosynthesis wires on the structural reorganization of metaepiphyseal cartilage (an experimental and morphological study)

Abstract

Introduction Premature arrest of bone growth is the most common complication of bone fractures at the growth plate level. The purpose of the work was to evaluate the structural reorganization of metaepiphyseal cartilage following its direct injury with metal and biodegradable wires in an experiment. Materials and methods The metaepiphyseal cartilage of the distal femur of 18 lambs of both sexes was studied. The age of the animals at the beginning of the study was (43.92 ± 0.8) days, by 60 and 120 days (102.63 ± 0.82) and (161.1 ± 0.9) days, respectively. The animals underwent transphyseal insertion of wires/ pins: series 1 — Kirschner wires, series 2 — titanium wires, series 3 — poly-L-lactic acid pins. The duration of the experiment was 60 and 120 days. Clinical and radiographic studies were carried out. Histomorphometry was performed using an AxioScope.A1 microscope and Zenblue software (CarlZeissMicroImagingGmbH, Germany). Results Reactive changes in the growth plate at the interface with the wire were manifested by proliferation of chondrocytes in the zone of proliferating cartilage and in the reserve zone; the minimally expressed changes were noted in series 2, the most pronounced were in series 1. By the end of the experiment, at the interface with the wire in series 1, blood vessels penetrated into the metaepiphyseal cartilage; in series 3 the amount of the fibrous component was increased, which indicates further formation of “bone bridges” and “fibrous bridges,” respectively. In undamaged areas of the growth plate in all series, the zonal structure was preserved. By the end of the experiment, increased values of the thickness of the metaepiphyseal cartilage were noted (1.2 times higher than the control), differences between series were a tendency; in series 2 and 3 the ratio of metaepiphyseal cartilage zones was comparable to the control; in series 1 the proportion of the proliferating cartilage zone was increased by 4 %. Discussion The main problem with growth plate injuries is the formation of bone tissue or fibrosis, which affects the growing process. Currently, the question of choosing a treatment tactic for growth plate injury depending on the size of the “bone bridges” is debatable. Relevant are future comparative studies of the regeneration of metaepiphyseal cartilage defects after the use of fixators made from different materials. Conclusion Histomorphometric characteristics of the growth zone reliably showed that the insertion of wires, regardless of their material, was not accompanied by inhibition of the bone-forming function of the distal metaepiphyseal cartilage of the femur.

Keywords

• growth plate
• metal and biodegradable fixators
• histology
• morphometry