The tibial plateau leveling osteotomy (TPLO) was introduced in 1993 as an innovative surgical procedure to treat stifle instability secondary to rupture of the cranial cruciate ligament (CCL) (Slocum 1993). The TPLO procedure eliminates cranial tibial thrust by converting this force into a compressive joint reaction force without restoring the passive constraint of the cranial cruciate ligament, resulting in a stable stifle during the stance phase of the gait cycle (Slocum 1993, Sahar 2006). The osteotomy created is stabilized by one of a variety of custom designed TPLO plates all of which vary in design characteristics, material and biomechanical properties.
Large and giant breed dogs have been shown to have a predisposition to develop rupture of the cranial cruciate ligament at a young age and biomechanical data regarding the performance of TPLO implants in these breeds is lacking (Duval 1999, Whitehair 1993). The objective of this study was to compare the axial stiffness of TPLO constructs stabilized with a single Synthes® broad TPLO plate (TPLO-broad) or a Slocum TPLO plate and a limited contact dynamic compression plate (LC-DCP) (TPLO-double).
Synthetic bone models were randomly assigned to one of two groups. All models underwent a standard TPLO and were stabilized with either a Synthes® Broad TPLO
plate or a Slocum TPLO plate and a LC-DCP. A gap was maintained at the osteotomy during plate application. Constructs were testes in axial compression and axial displacement and loads were recorded. Construct stiffness was calculated from load-displacement curves and comparisons of mean stiffness were performed.
The mean construct stiffness for the TPLO-broad constructs was not significantly different from that of the TPLO-double constructs. The minimum effective number of implants should be used clinically to achieve stability when performing a TPLO. Implant stiffness is a key contributor to the stability of an osteotomy and is integral to osteotomy healing.