title: Bone-femoral component interface gap after sagittal mechanical axis alignment is filled with new bone after cementless total knee arthroplasty.
abstract: OBJECTIVE
  This study retrospectively evaluated the fate of mismatch between an uncemented femoral component and each femoral cut surface (i.e., wedge-shaped gap) relative to sagittal mechanical alignment in total knee arthroplasty (TKA).
  
  
  METHODS
  Primary TKA was performed on 99 consecutive knees. The femoral components were aligned to the sagittal mechanical axis with CT-based navigation. All patients were assessed with postoperative true lateral radiographs. Bone-side surfaces of the uncemented femoral component were divided into five zones: anterior flange, anterior chamfer, posterior chamfer, posterior part, and distal part, which were defined as zones 1 to 5, respectively. Bone filling of wedge-shaped gaps in each zone was evaluated after 1 year.
  
  
  RESULTS
  Femoral anterior notching did not occur. However, wedge-shaped gaps were observed in at least one zone in 23 of 99 knees (23%), most frequently in zone 5 (18%). There were 9 and 7 gaps in zones 1 and 2, respectively. The femoral component showed malpositioning of approximately 3° of flexion in cases with wedge-shaped gaps in zones 2 and/or 5. After one year, 67% (6/9) of zone 1, 100% (7/7) of zone 2, and 94% (17/18) of zone 5 wedge-shaped gaps were filled in with new bone.
  
  
  CONCLUSIONS
  Femoral alignment relative to sagittal mechanical axis caused wedge-shaped gaps due to unstable anterior bone cutting through hard bone, but the small gaps were not clinically significant and filled in within one year. Sagittal setting of the femoral component should aim for the anatomical axis rather than the mechanical axis.
  
  
  METHODS
  IV.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan. kuriyama@kuhp.kyoto-u.ac.jp.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kuriyama
authors.affiliation: Department of Orthopaedic Surgery, Japanese Red Cross Society Wakayama Medical Center, Wakayama, Japan.
authors.forename: Katsufumi
authors.initials: K
authors.lastname: Hyakuna
authors.affiliation: Department of Orthopaedic Surgery, Nakae Hospital, Wakayama, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Inoue
authors.affiliation: Department of Orthopaedic Surgery, Japanese Red Cross Society Wakayama Medical Center, Wakayama, Japan.
authors.forename: Yasutsugu
authors.initials: Y
authors.lastname: Kawai
authors.affiliation: Department of Orthopaedic Surgery, Japanese Red Cross Society Wakayama Medical Center, Wakayama, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Tamaki
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan.
authors.forename: Hiromu
authors.initials: H
authors.lastname: Ito
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Matsuda
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D005269:Femur / Q000601:surgery*; D006801:Humans; D007593:Joint Instability / Q000517:prevention & control*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D016059:Range of Motion, Articular; D012189:Retrospective Studies
keywords: Malposition; Mechanical axis; Sagittal femoral alignment; Total knee arthroplasty; Wedge-shaped gap