title: Gap measurement in posterior-stabilized total knee arthroplasty with or without a trial femoral component.
abstract: OBJECTIVE
  To investigate the effects of a trial femoral component on the intraoperative joint gap and intraoperative joint gap kinematics throughout the range of knee motion in minimally invasive surgery-total knee arthroplasty (MIS-TKA) with the gap technique.
  
  
  METHODS
  A total of 103 patients [15 men (15 knees) and 89 women (89 knees)] aged 50-88 years (mean 74.8 years) who received MIS-TKA with the gap technique were included. The intraoperative joint gap differences (90° flexion gap distance minus 0° extension gap distance) with and without the trial femoral component were compared. Subsequently, the intraoperative joint gap kinematics at 0°, 45°, 90°, and 120° with the trial femoral component were investigated.
  
  
  RESULTS
  The intraoperative component gap difference (4.4 ± 2.7 mm) was larger than the estimated joint gap difference (1.2 ± 1.9 mm) (p < 0.01). The mean intraoperative component gap distances at 0°, 45°, 90°, and 120° of knee flexion were 14.7 ± 2.6, 19.0 ± 3.2, 19.2 ± 3.4, and 16.6 ± 3.3 mm, respectively. The intraoperative component gap distance increased significantly from 0° extension to 90° of knee flexion (p < 0.01), and then decreased significantly toward deep knee flexion at 120° (p < 0.01).
  
  
  CONCLUSIONS
  The trial femoral component influenced the intraoperative gap measurements, and increased the intraoperative gap difference. The joint gap kinematics with the trial femoral component were not constant throughout the range of knee motion, even if the appropriate joint gaps in extension and flexion were achieved. For acquisition of constant stability throughout the knee motion, the present results should be taken into account by surgeons performing MIS-TKA with the gap technique.
authors: Department of Orthopaedic Surgery, Hiroshima Prefectural Hospital, 1-5-54, Ujinakanda, Minami-ku, Hiroshima, 734-8530, Japan, payakichi0213@hotmail.com.
authors: Seiju
authors: S
authors: Hayashi
authors: Yuji
authors: Y
authors: Murakami
authors: Hiroyuki
authors: H
authors: Inoue
authors: Hiroo
authors: H
authors: Nobutou
authors: Koji
authors: K
authors: Nishida
authors: Yu
authors: Y
authors: Mochizuki
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D015331:Cohort Studies; D005260:Female; D005269:Femur / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000601:surgery; D016059:Range of Motion, Articular