Abstract
The true results of revision total knee arthroplasty (TKA) are not fully understood, for a variety of understandable reasons. But it is has been clear for decades that revision without a diagnosis is likely to fail. The evaluation of the problem TKA should be systematic (follow the same scheme every time) and comprehensive (all possibilities should be considered even if one diagnosis seems obvious).
Evaluation begins, as with all of medicine with a list of possible causes: the mechanisms of failure. John Moreland was the first to describe a coherent system which needed only one simple addition to be complete: 1.) Prosthetic joint infection; 2.) Extensor disruption; 3.) Patella and malrotation; 4.) Loose; 5.) Component breakage; 6.) PP fracture; 7.) Poor motion; and 8.) Tibial femoral instability.
Evaluation begins with the history, where 10 questions in particular are useful: 1.) What seems to be the problem? 2.) Was the “knee” ever successful after surgery? If there was never pain relief, is the current pain, the same or different? 3.) Standard pain quality questions - Location, duration, frequency, quality, exacerbating, ameliorating. 4.) Swelling? 5.) Stiffness? 6.) Giving way? 7.) Weakness? 8.) Things “just don't feel right”? 9.) Possible sepsis questions - Fever, chills, sources, primary TKA healing. 10.) Mood, social situation?
The physical exam should cover these ten points: 1.) Active extension; 2.) Rising from chair; 3.) Gait: hip, knee alignment, knee instability; 4.) Hip (internal rotation); 5.) Inspection; 6.) Tenderness; 7.) ROM; 8.) Stability (extension and 30–45 degrees flexion; 9.) Sitting on edge of exam table (knee at 90 degrees); and 10.) Step up on low stool (stair).
Investigations include: 1.) ESR + CRP; 2.) CBC; 3.) HGB- anemia; 4.) Lymphocytes- nutrition; 5.) GGT- alcohol abuse; 6.) Albumen- nutrition; 7.) HbA1c- diabetic control.
Imaging includes: 1.) Single leg weightbearing AP; 2.) Lateral; 3.) Merchant; 4.) Full length (hip-knee-ankle); 5.) AP pelvis; 6.) CT scan; and 7.) (Technitium bone scan).
