Abstract
BackgroundIn a standard total knee replacement, tibial component alignment is a key factor for the long term success of the surgery. The purpose of this study is to compare the accuracy of extramedullary and intramedullary tibial cutting guides used in indigenous and imported implants respectively, in positioning of the tibial components in megaprosthetic knee replacements.MethodsA comparative study of the accuracy of extramedullary and intramedullary tibial cutting guides was carried out in 92 megaprosthetic knee replacements for distal femoral tumors. For the proximal tibia cut for tibial component placement, an extramedullary guide was used in 65 patients and an intramedullary guide was used in 27 patients. Tibial component alignment angles were measured in postoperative X-rays with the help of CAD software.ResultsThere was more varus placement in coronal plane with extramedullary cutting guide (−1.18 +/− 2.4 degrees) than the intramedullary guide (−0.34 +/− 2.31 degrees) but this did not reach statistical significance. The goal of 90 +/− 2 degrees alignment of tibial component was achieved in 54% of patients in the extramedullary group versus 67% in the intramedullary group. In terms of sagittal plane alignment, extramedullary guide showed less accurate results (2.09 +/− 2.4 degrees) than intramedullary guide (0.50 +/− 3.80 degrees) for tibial component alignment, though 78% of patients were aligned within the goal of 0–5 degrees of tibial slope angle in extramedullary group versus 63% in intramedullary group. The mean error in the measurements due to rotation of the knee during taking the X-rays was less than 0.1 degrees and distribution of the X-rays with the rotation of knee was similar in both the groups.ConclusionsOverall, in megaprosthetic knee replacement intramedullary guides gave more accurate results in sagittal plane and exhibited similar variability as of extramedullary guides in coronal plane.
Highlights
In a standard total knee replacement, tibial component alignment is a key factor for the long term success of the surgery
The tibial component alignment is a key factor for the long term success of the surgery [1,2,3]
Extramedullary cutting guide was used in a group of patients who preferred Indigenous implant system
Summary
In a standard total knee replacement, tibial component alignment is a key factor for the long term success of the surgery. The purpose of this study is to compare the accuracy of extramedullary and intramedullary tibial cutting guides used in indigenous and imported implants respectively, in positioning of the tibial components in megaprosthetic knee replacements. Indigenous implant system (ResTOR knee system Sushrut, India) comes with an extramedullary cutting guide whereas the imported implant system (GMRS knee system, Stryker, USA) comes with an intramedullary cutting guide Both guides have an alignment rod which has to be first placed parallel to the anatomical axis. A saw blade is guided to make a cut perpendicular to the rod Both types of conventional guides use anatomical landmarks to position their alignment rod parallel to the anatomical axis of tibia [6]. The research objective of this study is to compare the accuracy of intramedullary and extramedullary guides used in the two implant systems as mentioned earlier for tibial resection
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