summary TKA Aseptic Loosening is a macrophage-induced inflammatory response that results in bone loss and implant loosening in the absence of an infection. Diagnosis can be made with plain radiographs of the knee. Treatment is generally revision arthroplasty with exchange of all loose components. Etiology Steps in the process include particulate debris formation macrophage activated osteolysis prosthesis micromotion particulate debris dissemination Pathophysiology factors affecting wear rate of polyethylene in TKA sterilization method manufacturing method (conventional vs. crosslinked) presence of third-body debris motion between modular tibial insert and metal tray (i.e., backside wear) roughness of femoral component counterface alignment and stability of the TKA malalignment causes asymmetric loading causes early loosening more frequent with varus rather than valgus malalignment demand or activity level of patient Presentation Symptoms painless early disease pain location localized to the tissues around the loose components aggrevating factors weightbearing often activity related Physical exam may have minimal pain with ROM increased pain with weight bearing Radiographs recommended views AP tibial osteolysis readily visible on AP femoral osteolysis may be difficult to detect on AP as lesions are typically located in posterior condyles and are obscured by the femoral component lateral oblique often more helpful for identifying femoral osteolysis findings radiolucent area around implant or cement with sclerotic border especially radiolucencies > 2 mm change in position of the implant varus or valgus subsidence of tibial component progressive widening of cement-bone or bone-prosthesis interface cement cracking or fragmentation CT Scan & MRI viable options for assessing larger osteolytic lesions to aid in preoperative planning Studies Serum labs ESR normal CRP normal Differential Critical to rule out periprosthetic joint infection Treatment Nonoperative observation indications stable implant with minimal symptoms Operative revision TKA indications pain due to aseptic loosening pain with evidence of osteolysis extensive osteolysis that would compromise revision surgery in the future technique bone graft indicated for defects > 10 mm often used in younger patients to preserve bone stock prosthetic metal wedges/augments indicated for defects > 10 mm often used in elderly, low activity patients bone cement indicated for smaller defects heat released can cause thermal necrosis of surrounding bone and vascular tissue which can potential lead to aseptic loosening Techniques Revision TKA