title: Assessment of the midflexion rotational laxity in posterior-stabilized total knee arthroplasty.
abstract: OBJECTIVE
  To evaluate changes in midflexion rotational laxity before and after posterior-stabilized (PS)-total knee arthroplasty (TKA).
  
  
  METHODS
  Twenty-nine knees that underwent PS-TKA were evaluated. Manual mild passive rotational stress was applied to the knees, and the internal-external rotational angle was measured automatically by a navigation system at 30°, 45°, 60°, and 90° of knee flexion.
  
  
  RESULTS
  The post-operative internal rotational laxity was statistically significantly increased compared to the preoperative level at 30°, 45°, 60°, and 90° of flexion. The post-operative external rotational laxity was statistically significantly decreased compared to the preoperative level at 45° and 60° of flexion. The post-operative internal-external rotational laxity was statistically significantly increased compared to the preoperative level only at 30° of flexion. The preoperative and post-operative rotational laxity showed a significant correlation at 30°, 45°, 60°, and 90° of flexion.
  
  
  CONCLUSIONS
  Internal-external rotational laxity increases at the initial flexion range due to resection of both the anterior or posterior cruciate ligaments and retention of the collateral ligaments in PS-TKA. Preoperative and post-operative rotational laxity indicated a significant correlation at the midflexion range. This study showed that a large preoperative rotational laxity increased the risk of a large post-operative laxity, especially at the initial flexion range in PS-TKA.
  
  
  METHODS
  III.
authors.affiliation: Department of Orthopaedic Surgery, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime, 790-0295, Japan. taimisaki@gmail.com.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Hino
authors.affiliation: Department of Orthopaedic Surgery, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime, 790-0295, Japan.
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Kutsuna
authors.affiliation: Department of Orthopaedic Surgery, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime, 790-0295, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Oonishi
authors.affiliation: Department of Orthopaedic Surgery, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime, 790-0295, Japan.
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Watamori
authors.affiliation: Department of Orthopaedic Surgery, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime, 790-0295, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kiyomatsu
authors.affiliation: Department of Orthopaedic Surgery, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime, 790-0295, Japan.
authors.forename: Yasutake
authors.initials: Y
authors.lastname: Iseki
authors.affiliation: Department of Orthopaedic Surgery, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime, 790-0295, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Watanabe
authors.affiliation: Department of Orthopaedic Surgery, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime, 790-0295, Japan.
authors.forename: Yasumitsu
authors.initials: Y
authors.lastname: Ishimaru
authors.affiliation: Department of Orthopaedic Surgery, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime, 790-0295, Japan.
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Miura
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007592:Joint Diseases / Q000601:surgery*; D007593:Joint Instability / Q000503:physiopathology / Q000601:surgery*; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D012399:Rotation; D025321:Surgery, Computer-Assisted
keywords: Midflexion laxity; Navigation system; Posterior-stabilized; Rotational laxity; Soft tissue balance; Total knee arthroplasty