Abstract
Despite proven advantages, pulsatile lavage seems to be used infrequently during preparation in cemented total knee arthroplasty. This remains irritating, as the technique has been suggested to improve radiological survival in cemented TKA, where aseptic loosening of the tibial component represents the main reason for revision. Furthermore, there may be a potential improvement of fixation strength for the tibial tray achieved by increased cement penetration. In this study, the influence of pulsed lavage on mechanical stability of the tibial component and bone cement penetration was analyzed in a cadaveric setting. Six pairs of cadaveric, proximal tibia specimen underwent computed tomography (CT) for assessment of bone mineral density (BMD) and exclusion of osseous lesions. Following surgical preparation, in one side of a pair, the tibial surface was irrigated using 1800ml normal saline and pulsatile lavage, while in the other side syringe lavage using the identical amount of fluid was applied. After careful drying, bone cement was hand-pressurized on the bone surface, tibial components were inserted and impacted in an identical way. After curing of cement, specimen underwent a postimplantation CT analysis). Cement distrubution was then assessed using a three-dimenionsional visualization software. Trabecular bone, cement and implant were segmented based on an automatic thresholding algorithm, which had been validated in a previous study. This allowed to determine median cement penetration for the entire cemented area. Furthermore, fixation strength of the tibial trays was determined by a vertical pull-out test using a servohydraulic material testing machine. Testing was performed under displacement control at a rate of 0,5mm/sec until implant failure. Data was described by median and range. Results were compared by a Wilcoxon matched pairs signed rank test with a type 1 error probability of 5 %. Median pull-out forces in the pulsed lavage group were 1275N (range 864–1391) and 568N (range 243–683) in the syringe lavage group (p=0.031). Cement penetration was likewise increased (p=0.031) in the pulsed lavage group (1.32mm; range 0.86–1.94), when compared to the syringe irrigated group (0.79mm; range 0.51–1.66). Failure occurred in the pulsatile lavage group at the implant-cement interface and in the syringe lavage group at the bone-cement interface, which indicates the weakness of the latter. Altogether, improved mechanical stability of the tibial implant and likewise increased bone cement interdigitation could be demonstrated in the current study, when pulsed lavage is implemented. Enhanced fixation strength was suggested being a key to improved survival of the implant. If this is the case, pulsatile lavage should be considered being a mandatory preparation step when cementing tibial components in TKA.
