Intramedullary reaming of long bones

Abstract

In about 10% of all reconstructive operations caused by traumatic, resectional or congenital defects, bone grafts or bone substitutes are necessary. In the course of reconstructive surgery reaming debris has not been mentioned yet, because it was designated as a necrotic material, which does not contain vital cells. Autogenic bone grafting is still regarded as the golden standard to treat large bone defects. However, collection of the autogenic material from the iliac crest requires a second site of surgery, which can be associated with complications such as pain, infections and haematoma [1, 2]. Bone substitutes comprise a wide range of materials. Based upon their chemical and physical features, these materials closely mimic the mineral phase of natural bone. These biomimetic properties promote the process of bone healing. However, in contrast to the natural bone, anorganic bone substitutes reveal no signs of biological activity due to the lack of growth or differentiation factors and cells, whose participation in the process of bone healing is of great functional importance [3-5]. Therefore, new strategies have been developed to treat large bone defects. These innovations of tissue engineering are based upon the knowledge about complex interactions between osteoinductive factors and cells in vivo. Consequently, bone healing is improved by using implants in combination with autogenic or recombinant growth factors and/or cells [6]. The clinical use of autogenic cells requires their collection prior to their expansion in vitro before growth on a suitable matrix can be carried out [6]. Cancellous bone [6-8] and bone marrow [9] represent sources of osteoblastic cells and multi-potential mesenchymal stem cells (MSCs) [10-14]. Because of their differentiation capacity, MSCs have a therapeutic potential that is already used regarding the composition of newly developed bone graft substitutes [10]. Up to now, discussion of osteoregenerative effects of reaming debris has been controversial. It has been assumed that the cells undergo necrosis during the reaming procedure due to temperature elevations [15] and the influence of mechanical forces [15-19]. In contrast, experimental studies in the sheep and a few clinical studies in humans refer to the osteoinductive potential of reaming debris in vivo. Additionally, in vitro culturing of ovine reaming debris [19] has proven the vitality of the cells and has confirmed their osteoblast-like properties. In accordance with these findings, clinical studies have documented that fractures of long bones showed distinctly shorter times of healing when treated with reamed nails, than fractures treated with non-reamed nails [20-25]. Although the cause of this phenomenon has still to be clarified, it has been assumed that reaming creates a high potential of regeneration caused by the osteoinductive effects of blood and bone marrow, whereas dispersed bone fragments promote healing in an osteoconductive manner [26]. However, it has been taken into consideration that reaming of bones bears the risk of fat embolism or it can cause the adult respiratory distress syndrome. Although there is no final scientific evidence for the assumption that reaming debris has stimulatory effects on bone healing, it might represent an autogenous source of vital cells, which could be used in the scope of bone tissue grafting. With special regard to this potential clinical significance, cells of human reaming debris have been investigated in the present in vitro study. The purpose was to prove vitality of the cells by means of cell culturing and by transmission electron microscopy and-if so-to characterise the viable cells phenotypically by means of morphology, antigenic properties and their capacity to differentiate in multiple cell lineages. © Springer Berlin Heidelberg 2006.