Kelly G. Vince MD, FRCS(c), a, Ayesha Abdeen MD, FRCS(c)a and Tanzo Sugimori MDa
aDepartment of Orthopaedic Surgery, Keck School of Medicine of the University of Southern California, Health Consultation Center II, Los Angeles, California
Surgery for the unstable total knee arthroplasty requires a deep understanding of the causes and a plan that specifically addresses them. Isolated ligament reconstructions and polyethylene insert exchanges generally do not work. Patients may experience buckling from pain, flexion contracture, recurvatum, or patellar problems. True mechanical instability may result from loosening, bone loss, prosthetic breakage, component size or position, fracture, wear, or collateral ligament failure. Only the last one typically requires a constrained implant. The possible modes (directions) of instability are the following: varus-valgus, recurvatum, flexion, and global. Revision surgery must eliminate deforming forces, most frequently frontal plane alignment. Prosthetic implants, no matter how well engineered, are not a substitute for diagnosis and surgical technique.
The Journal of Arthroplasty. Volume 21, Issue 4, Supplement 1 , June 2006, Pages 44-49.