title: The unstable total knee arthroplasty: causes and cures.
abstract: 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.
authors.affiliation: Department of Orthopaedic Surgery, Keck School of Medicine of the University of Southern California, Health Consultation Center II, Los Angeles, California 90033, USA.
authors.forename: Kelly G
authors.initials: KG
authors.lastname: Vince
authors.forename: Ayesha
authors.initials: A
authors.lastname: Abdeen
authors.forename: Tanzo
authors.initials: T
authors.lastname: Sugimori
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D001265:Athletic Injuries / Q000601:surgery; D005260:Female; D005269:Femur / Q000601:surgery; D006801:Humans; D007593:Joint Instability / Q000209:etiology; D008022:Ligaments / Q000601:surgery; D011475:Prosthesis Failure; D016059:Range of Motion, Articular; D012086:Reoperation; D013977:Tibia / Q000601:surgery