Purpose: To evaluate the use of locked Compression Plate (L.C.P.) in metaphyseal long bones fractures, and report our preliminary results.

Materials and Methods: 23 patients 14–82 years old with long bones metaphyseal fractures underwent surgery with the use of L.C.P. between January 2004 and August 2004. Four patients were adolescents.

7 patients had Supracondylar femoral fracture. One of them had the fracture at the tip of IMN. 11 patients had distal Tibia, one had proximal+midshaft tibia and 4 had distal humerus fractures. All plates were prebended to fit the area of the fracture using a skeleton model. The plates were inserted percutaneously with reduction of the fracture.

Partial weight bearing started after 6 weeks and full weight bearing started after 12 weeks.

Results: Unuion was seen in x-ray after 6 to 12 week in 95% of patients. 20 patients regained full range of motion of the adjacent joints at 3 months follow-up.

Complications: One patient developed compartment Syndrome in a high energy tibial fracture. One patient developed deep infection at the site of fibular plate not affecting the L.C.P. at the tibia. One patient developed temporary weakness of extensor Hallucis longus.

Conclusions: L.C.P. proved to be effective in fixation of meta-epiphyseal zones which are difficult in IMN fixation. The use of this plate enables fixation of long bones in adolescents with open growth plate. The locking system enables good fixation of osteoporotic bones and in periprosthetic fracture. The high primary stability in combination with newly developed minimal-invasive techniques (MIPO = minimal invasive plate osteosynthesis) are the bases for a rapid bony consolidation, a low complication rate and good functional results.

Periprosthetic osteolysis is a major cause of aseptic loosening in artificial joint replacement. It is assumed to occur in conjunction with the activation of macrophages. We have shown in vitro that human osteoblast-like cells, isolated from bone specimens obtained from patients undergoing hip replacement, phagocytose fine particles of titanium alloy (TiAlV).

The human osteoblast-like cells were identified immunocytochemically by the presence of bone-specific alkaline phosphatase (BAP). With increasing duration of culture, a variable number of the osteoblastic cells became positive for the macrophage marker CD68, independent of the phagocytosis of particles, with a fine granular cytoplasmic staining which was coexpressed with BAP as revealed by immunodoublestaining. The metal particles were not toxic to the osteoblastic cells since even in culture for up to four weeks massively laden cells were vital and had a characteristic morphology. Cells of the human osteosarcoma cell line (HOS 58) were also able to phagocytose metal particles but had only a low expression of the CD68 antigen. Fluorescence-activated cell scanning confirmed our immunocytochemical results. Additionally, the cells were found to be negative for the major histocompatibility complex-II (MHC-II) which is a marker for macrophages and other antigen-presenting cells. Negative results of histochemical tests for tartrate-resistant acid phosphatase excluded the contamination by osteoclasts or macrophages in culture.

Our observations suggest that the osteoblast can either change to a phagocytosing cell or that the phagocytosis is an underestimated property of the osteoblast. The detection of the CD68 antigen is insufficient to prove the monocytic lineage. In order to discriminate between macrophages and osteoblasts additional markers should be used. To our knowledge, this is the first demonstration of cells of an osteoblastic origin which have acquired a mixed phenotype of both osteoblasts and macrophages.