Towards a Standard Approach to Assess Tibial Bone Loss Following Total Knee Arthroplasty

Long-term implant failure in the form of aseptic loosening and periprosthetic fracture is the most common cause of revision procedures in total knee arthroplasty (TKA). While early loosening can often be attributed to failure of primary fixation, late implant failure could be associated with loss of fixation secondary to bone resorption, as a result of stress shielding in the proximal tibia. This current review study was performed to identify the clinical effects of different implant-, patient-, and surgery-related biomechanical factors on TKA-related tibial bone loss in clinical reality. Implant-related factors considered were the fixation method, and the implant type, geometry, and stiffness. In terms of patient characteristics, the effects of age, sex, knee alignment, bone density, body weight, and activity level were analyzed. The clinical literature on these topics mostly concerned longitudinal radiographic studies investigating the effect of a single factor on changes in the proximal tibia over time using bone densitometry. Implant stiffness, implant geometry and knee alignment were the only factors consistently found to affect regional bone density changes over time. Each clinical study used its own specific study design, with different definitions used for the baseline density, time points of baseline and follow-up measurements, and regions of interest. Due to the differences in study design, direct comparison between the clinical impact of different biomechanical factors was not possible. Based on the findings over the densitometry studies, a standardized guideline was proposed to allow reliable comparison between consistently reported outcome of future radiographic TKA studies.