title: Outcomes of untreated posterolateral knee injuries: an in vivo canine model.
abstract: OBJECTIVE
  The purpose of our study was to determine if sectioning the canine fibular collateral ligament, popliteus tendon, and popliteofibular ligament would result in residual posterolateral instability and produce measureable evidence of early-onset arthritis on ultra-high field MRI.
  
  
  METHODS
  The fibular collateral ligament, popliteus tendon, and popliteofibular ligament were surgically sectioned in six canines. Six months postoperatively, both limbs were biomechanically tested involving 3.25 Nm varus and 1.25 Nm internal and external rotation torques at 28.5° (mean full extension), 60°, and 90° of flexion. A 7.0-tesla MRI scanner acquired T (1ρ)-weighted images, and relaxation time constants were calculated.
  
  
  RESULTS
  Compared to the non-operative knees, varus angulation significantly increased by 2.0°, 8.0°, and 12.4° in the operative knees at full extension, 60° flexion, and 90° flexion, respectively. External rotation was significantly increased by 8.1° at full extension, 12.2° at 60°, and 8.2° at 90°. Internal rotation was significantly increased by 9.1° at full extension and 12.4° at 60°. T (1ρ) MRI mapping revealed a significant increase in relaxation times in the medial compartment of the surgical knees compared to controls.
  
  
  CONCLUSIONS
  This study validated that grade III surgically created posterolateral knee injuries do not heal and that the canine knee developed early-onset changes of the medial compartment, indicative of early-onset osteoarthritis, developed in the operative knees.
authors.affiliation: Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Chad J
authors.initials: CJ
authors.lastname: Griffith
authors.forename: Coen A
authors.initials: CA
authors.lastname: Wijdicks
authors.forename: Ute
authors.initials: U
authors.lastname: Goerke
authors.forename: Shalom
authors.initials: S
authors.lastname: Michaeli
authors.forename: Jutta
authors.initials: J
authors.lastname: Ellermann
authors.forename: Robert F
authors.initials: RF
authors.lastname: LaPrade
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D017885:Collateral Ligaments / Q000293:injuries; D004195:Disease Models, Animal; D004285:Dogs; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology*; D007718:Knee Injuries / Q000503:physiopathology*; D008023:Ligaments, Articular / Q000293:injuries*; D008279:Magnetic Resonance Imaging; D008297:Male; D020370:Osteoarthritis, Knee / Q000209:etiology; D012399:Rotation; D013708:Tendon Injuries / Q000503:physiopathology*