A New Pressure-Free Intramedullary Reamer

Abstract

Use of intramedullary reamers (IR) is typically associated with pressure generation during the reaming process, which may result in the introduction of fat and marrow particles into the venous system. Thus, a new system was designed in order to avoid pressure generation and thus reduce the risk of embolic events. In-vitro testing was carried out using pig femura. Intramedullary pressure was recorded during drilling with either the new pressure-free intramedullary reamer (PF-IR; n = 10) or a standard AO-IR (n = 10). For in vivo testing, nailing of the femur  was performed in sheep using either the PF-IR (n = 7) or the standard AO-IR (n = 7). Fat intravasation was measured using echocardiography and the Gurd test. Hemodynamic and pulmonary parameters as well as intramedullary pressure were continuously recorded during the experiments. The animals were then sacrificed and tissue samples were taken from all regions of the lungs. The incidence of lung fat emboli in histological sections was scored in a blinded manner. A finite element analysis was carried out to assess performance of the PF-IR under load. The in-vitro tests showed that the new PF-IR resulted in significantly less intramedullary pressure (15 ± 12 mm Hg) than the standard AO-IR (813 ± 247 mm Hg; p < 0.001, Mann-Whitney U-test). These results were confirmed in-vivo. Moreover, the PF-IR group had significantly less fat intravasation (Gurd test) and better hemodynamic and pulmonary values than the AO-IR group. The incidence of fat microemboli in the lungs was reduced by 90 % in the PF-IR group. Final element analysis showed that the new drilling system performed well under load. The newly developed pressure-free IR clearly outperformed a standard AO-IR. Use of the new PF-IR was associated with low intramedullary pressures, significantly less fat intravasation, and a markedly lower incidence of fat emboli in the lung. This, in turn, may have been the reason for the better hemodynamic and pulmonary values in the PF-IR group.

Key words

Fat embolism - intramedullary pressure - reaming - endoprosthetic

References

• 1 Dewey P. Femoral nailing and pulmonary embolism.  J Bone Joint Surg [Br]. 1994;  67 677-678
• 2 Kröpfl A, Davies J, Berger U, Hertz H, Schlag G. Intramedullary pressure and bone marrow fat extravasation in reamed and unreamed femoral nailing.  J Orthop Res. 1999;  17 261-268
• 3 Patterson B, Healey J, Cornell C, Sharrock N. Cardiac arrest during hip arthroplasty with a cemented long-stem component.  J Bone Joint Surg [Am]. 1991;  73 271-277