An investigation of the performance of Biostop G and Hardinge bone plugs

Although distal plugging is a common procedure to prevent distal flow of polymethyl-methacrylate (PMMA) cement during cementing of femoral prostheses, there is little biomechanical testing to confirm that (a) the plugs do not displace under cementing pressure, and (b) they do in fact occlude cement flow. Two designs of femoral intramedullary plugs, the Biostop G (Bioland, France) and Hardinge (De Puy, Leeds, UK) were examined to determine their performance under cement pressurization in a biomechanical test. A testing rig was fabricated in which distal migration could be measured as a function of cement pressurization. Sectioning of the samples after polymerization of the cement revealed the extent of cement flow. The results show that, even in this well controlled test, there is significant variability in plug performance. It is shown that the Biostop G displaces less than the Hardinge for similar cement pressures. Sectioning reveals that cement can escape around the Hardinge plug at high pressures. Furthermore, a pore forming effect of the Biostop G plug was occasionally observed indicating that design improvements may be possible for this plug.