The Effect of Working Time and Application Technique on Cement Penetration into a Tibial Model.

Background: Aseptic loosening of the cemented tibial component is a source of failure in total knee arthroplasty. This study examined common techniques for cement application by quantifying depth and volume of penetration into tibia models. Material and methods: Thirty-six composite tibia models were cemented with a tibial component using 3 application techniques (gun, osteotome, and layered) with either early or late cement working time. Computed tomography and 3D-modeling were used to quantify volume and depth of penetration. Statistical analysis was conducted with analysis of variance with Bonferroni correction and Student's t-test. Results: No difference was found in overall volume of penetration between early and late cement application (P = .16). Beneath the baseplate, the layered technique had significantly less penetration and averaged less than 3 mm with early and late cement. The gun technique had the greatest depth of penetration with early cement and averaged greater than 3 mm in all zones regardless of cement working time. The osteotome technique achieved significantly greater depth of penetration around the keel with early and late cement, P < .01. Conclusions: Using a cement gun ensures adequate penetration beneath the baseplate regardless of cement working time while the osteotome technique is effective to increase penetration around the implant keel. According to our study, applying cement early in its working time may not increase volume of penetration. This study raises concern regarding adequate cement penetration using the layered technique for cementing the tibial component in total knee arthroplasty, and future research is warranted.

Tibial compression is anabolic in the adult mouse skeleton despite reduced responsiveness with aging.

The ability of the skeleton to adapt to mechanical stimuli diminishes with age in diaphyseal cortical bone, making bone formation difficult for adults. However, the effect of aging on adaptation in cancellous bone, tissue which is preferentially lost with age, is not well characterized. To develop a model for early post-menopausal women and determine the effect of aging on cancellous bone adaptation in the adult mouse skeleton, in vivo tibial compression was applied to adult (26 week old) osteopenic female mice using loading parameters, peak applied load and peak diaphyseal strain magnitude, that were previously found to be osteogenic in young, growing (10 week old) mice. A Load-Matched group received the same peak applied loads (corresponding to +2100 µÎµ at the medial diaphysis of the tibia) and a Strain-Matched group received the same peak diaphyseal strains (+1200 µÎµ, requiring half the load) as the young mice. The effects of mechanical loading on bone mass and architecture in adult mice were assessed using micro-computed tomography and in vivo structural stiffness measures. Adaptation occurred only in the Load-Matched group in both the metaphyseal and diaphyseal compartments. Cancellous bone mass increased 54% through trabecular thickening, and cortical area increased 41% through medullary contraction and periosteal expansion. Adult mice were able to respond to an anabolic stimulus and recover bone mass to levels seen in growing mice; however, the adaptive response was reduced relative to that in 10 week old female mice for the same applied load. Using this osteogenic loading protocol, other factors affecting pathological bone loss can be addressed using an adult osteopenic mouse model.