Abstract
Modifiable factors contributing to stiffness include alignment, implant size, implant position and rotation, and soft tissue tightness or laxity. Less modifiable factors include genetics as in predisposition to inflammation and fibrosis, aberrations in perception and experience of emotional pain, and preoperative range of motion.
We reviewed 559 knees undergoing revision between 2007 and 2014, selecting out patients with a diagnosis of stiffness and greater than one-year follow-up. Stiffness was defined as greater than 15 degrees of flexion contracture or less than 75 degrees of flexion or less than 90 degrees of active motion and a chief complaint of limited motion and pain. Radiographic analysis used a set of matched controls with greater than 90 degrees and full extension prior to surgery and were further matched by age, gender, BMI.
Flexion contracture changed from an average of 9.7 to an average of 2.3 degrees, flexion changed from an average of 81 to an average of 94 degrees, active motion changed from an average of 72 to an average of 92 degrees, pain scores improved from 44 to 72 points, and Knee Society function scores improved from an average of 49 to an average of 70 points. There were four failures for stiffness, two knees underwent additional manipulation, gaining an average of 10 degrees; and two knees were revised.
Radiographic analysis demonstrated stiffness to be strongly correlated to anterior condylar offset ratio and to patellar displacement by multivariant regression analysis, suggesting that overstuffing the patellofemoral joint by anteriorization of the femoral component is associated with stiffness. Using modern revision techniques, revision for stiffness creates reliable improvements in pain, Knee Society clinical and functional scores, and motion.
