Causes of Total Knee Arthroplasty Hardware Loosening

Primary Causes of Aseptic Loosening

Mechanical stresses are a leading contributor to aseptic loosening, creating micromotion at the implant-bone or cement-bone interface, according to the American College of Radiology 1, 2
Malalignment created during surgery can progress to instability and eventually loosening, as reported by the American College of Radiology 1, 3
Instability represents a common cause of prosthesis failure and can lead to loosening over time, with a reported incidence of 7.5% of cases, according to the American College of Radiology 3

Osteolysis is a leading cause of late TKA revision, typically triggered by polyethylene wear debris, as stated by the American College of Radiology 2, 4
Cement and metal debris can also trigger cell-mediated inflammatory responses leading to osteolysis, according to the American College of Radiology 2
The inflammatory process involves macrophage phagocytosis of particle debris, creating granulation tissue with phagocytosed particulate debris, as reported by the American College of Radiology 2
Osteolysis is more common in cementless TKAs compared to cemented ones, according to the American College of Radiology 2

Poor bone stock can contribute to inadequate fixation and subsequent loosening, as stated by the American College of Radiology 1, 2

Osteolysis commonly occurs in the region of the femoral condyles near the attachment of the collateral ligaments, along the periphery of the component, and along the access channels to the cancellous bone of the tibia, including screw holes, according to the American College of Radiology 2

Bone scintigraphy may be helpful in diagnosing loosening, but only when obtained many years after surgery due to high false positive rates in the first 1-2 years, as reported by the American College of Radiology 3, 4

Small areas of osteolysis may be monitored, but large areas suggest component loosening and may require revision surgery, according to the American College of Radiology 2
Serial bone scans are more helpful than a single examination for diagnosing loosening, as stated by the American College of Radiology 4
Normal bone scans have a high negative predictive value, indicating that loosening is unlikely, according to the American College of Radiology 4
Positive bone scans are noted in 20% of asymptomatic knees 1 year after surgery and in 12.5% of individuals 2 years after surgery, as reported by the American College of Radiology 4