title: The Position of the Patella and Extensor Mechanism Affects Intraoperative Compartmental Loads During Total Knee Arthroplasty: A Pilot Study Using Intraoperative Sensing to Guide Soft Tissue Balance.
abstract: The achievement of a well-balanced total knee arthroplasty is necessary for long-term success. We hypothesize that the dislocation of the patella during surgery affects the distribution of loads in the medial and lateral compartments. Intraoperative load sensors were used to record medial and lateral compartment loads in 56 well-balanced TKAs. Loads were recorded in full extension, relaxed extension, at 45 and 90° of flexion at full gravity-assisted flexion, with the patella in four different positions: dislocated (everted and not), located, and located and secured with two retinacular sutures. The loads in the lateral compartment in flexion were higher with a dislocated patella than with a located patella (P<0.001). A lateralized extensor mechanism artificially increases in the lateral compartment loads in flexion during TKA surgery. Instruments that allow intraoperative soft tissue balance with the patella in a physiologic position are more likely to replicate postoperative compartment loads.
  
  
  METHODS
  II (prospective comparative study).
authors.affiliation: Desert Orthopedic Center, Rancho Mirage, California.
authors.forename: Erik
authors.initials: E
authors.lastname: Schnaser
authors.affiliation: Hospital for Special Surgery-Weill Medical College of Cornell University, New York, New York.
authors.forename: Yuo-yu
authors.initials: YY
authors.lastname: Lee
authors.affiliation: Hospital for Special Surgery-Weill Medical College of Cornell University, New York, New York.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Boettner
authors.affiliation: Hospital for Special Surgery-Weill Medical College of Cornell University, New York, New York.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Gonzalez Della Valle
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods*; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D007593:Joint Instability / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D010329:Patella / Q000601:surgery*; D010865:Pilot Projects; D011446:Prospective Studies; D016059:Range of Motion, Articular / Q000502:physiology*; D013314:Stress, Mechanical; D016896:Treatment Outcome
keywords: extensor mechanism; instability; intraoperative sensors; ligament balance; total knee arthroplasty