title: A forty millimetre head significantly improves range of motion compared with a twenty eight millimetre head in total hip arthroplasty using a computed tomography-based navigation system.
abstract: Larger-diameter (≥40 mm) femoral heads decrease the incidence of post-operative dislocation in total hip arthroplasty (THA). This study was conducted to discover whether larger-diameter femoral heads result in greater range of motion of the hip with the use of a computed tomography (CT)-based navigation system.
  
  
  
  Thirty-nine primary THAs were performed via a posterolateral approach using a CT-based navigation system. The stem was inserted in the femur in line with the original femoral neck anteversion. Considering the range of motion during various daily activities which could occur without impingement, the cup anteversion was decided at 10 ° increments according to the stem anteversion. While the cup inclination was set at 40 ° in order to avoid a high inclination angle to prevent the edge roading between the HXLPE liner and ceramic head. After implantation, trial liners and femoral heads were used with either 28 or 40 mm diameter. Maximal hip flexion, extension, abduction, external rotation in extension at 0° and internal rotation angles in flexion at 90 ° were measured. The differences between the ranges of motion with the 40-mm and 28-mm heads were tested. The results were assessed with paired Student t-tests.
  
  
  
  The ranges of motion in flexion, extension, abduction and internal rotation angles improved significantly with the 40-mm heads compared with the 28-mm heads. The ranges of motion of cases where maximal flexion angle was 90° or less were excluded, improved significantly with the 40 mm heads.
  
  
  
  We concluded that the larger-diameter 40-mm femoral prosthetic heads result in greater ranges of motion in flexion, extension, abduction and internal rotation.
authors.affiliation: Arthroplasty Center, Osaka General Medical Center, 3-1-56, Bandai-higashi, Sumiyoshi, Osaka, Japan. kosuke-t@umin.net.|Department of Orthopaedic Surgery, Osaka General Medical Center, 3-1-56, Bandai-higashi, Sumiyoshi, Osaka, Japan. kosuke-t@umin.net.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Tsuda
authors.affiliation: Arthroplasty Center, Osaka General Medical Center, 3-1-56, Bandai-higashi, Sumiyoshi, Osaka, Japan.|Department of Orthopaedic Surgery, Osaka General Medical Center, 3-1-56, Bandai-higashi, Sumiyoshi, Osaka, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Haraguchi
authors.affiliation: Arthroplasty Center, Osaka General Medical Center, 3-1-56, Bandai-higashi, Sumiyoshi, Osaka, Japan.|Department of Orthopaedic Surgery, Osaka General Medical Center, 3-1-56, Bandai-higashi, Sumiyoshi, Osaka, Japan.
authors.forename: Junichiro
authors.initials: J
authors.lastname: Koyanagi
authors.affiliation: Department of Orthopaedic Surgery, Osaka Rosai Hospital, 1179-3, Nagasone-cho, Kita, Sakai, Osaka, Japan.
authors.forename: Shintaro
authors.initials: S
authors.lastname: Takahashi
authors.affiliation: Department of Orthopaedic Surgery, Saiseikai Nakatsu Hospital, 2-10-39, Shibata, Kita, Osaka, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Sugama
authors.affiliation: Department of Orthopaedic Surgery, Osaka General Medical Center, 3-1-56, Bandai-higashi, Sumiyoshi, Osaka, Japan.
authors.forename: Keiju
authors.initials: K
authors.lastname: Fujiwara
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D005260:Female; D005270:Femur Head / Q000601:surgery*; D006801:Humans; D004204:Joint Dislocations; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D012399:Rotation; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: CT-based navigation; Femoral head diameter; Range of motion; Total hip arthroplasty