title: Usefullness of three-dimensional templating software to quantify the contact state between implant and femur in total hip arthroplasty.
abstract: BACKGROUND
  It would be ideal if surgeons could precisely confirm whether the planned femoral component achieves the best fit and fill of implant and femur. However, the cortico-cancellous interfaces can be difficult to standardize using plain radiography, and therefore, determining the contact state is a subjective decision by the examiner. Few reports have described the use of CT-based three-dimensional templating software to quantify the contact state of stem and femur in detail. The purpose of this study was to use three-dimensional templating software to quantify the implant-femur contact state and develop a technique to analyze the initial fixation pattern of a cementless femoral stem.
  
  
  METHODS
  We conducted a retrospective review of 55 hips in 53 patients using a short proximal fit-and-fill anatomical stem (APS Natural-Hip™ System). All femurs were examined by density mapping which can visualize and digitize the contact state. We evaluated the contact state of implant and femur by using density mapping.
  
  
  RESULTS
  The varus group (cases that had changed varus 2° by 3 months after surgery) consisted of 11 hips. The varus group showed no significant difference with regard to cortical contact in the proximal medial portion (Gruen 7), but the contact area in the distal portion (Gruen 3 and Gruen 5) was significantly lower than that of non-varus group. Density mapping showed that the stem only has to be press-fit to the medial calcar, but also must fill the distal portion of the implant in order to achieve the ideal contact state.
  
  
  CONCLUSIONS
  Our results indicated that quantifying the contact state of implant and femur by using density mapping is a useful technique to accurately analyze the fixation pattern of a cementless femoral stem.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8641, Japan. daisuke_i_0909@yahoo.co.jp.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Inoue
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8641, Japan. tamonkabata@yahoo.co.jp.
authors.forename: Tamon
authors.initials: T
authors.lastname: Kabata
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8641, Japan. torumaed@gmail.com.
authors.forename: Toru
authors.initials: T
authors.lastname: Maeda
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8641, Japan. yoshitomokajino@gmail.com.
authors.forename: Yoshitomo
authors.initials: Y
authors.lastname: Kajino
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8641, Japan. kkkkkenji76@yahoo.co.jp.
authors.forename: Kenji
authors.initials: K
authors.lastname: Fujita
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8641, Japan. kazuhiro63hasegawa@gmail.com.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Hasegawa
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8641, Japan. t_y_410@yahoo.co.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8641, Japan. tpuyan@gmail.com.
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Takagi
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8641, Japan. takaaki3530@gmail.com.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Ohmori
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8641, Japan. tsuchi@med.kanazawa-u.ac.jp.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tsuchiya
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D015519:Bone Density / Q000502:physiology; D000069343:Bone-Implant Interface / Q000000981:diagnostic imaging*; D005260:Female; D005269:Femur / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D010347:Patient Care Planning; D011300:Preoperative Care; D011474:Prosthesis Design; D012189:Retrospective Studies; D012984:Software; D014057:Tomography, X-Ray Computed
keywords: Computed tomography; Contact state of implant and femur; Density mapping; Three-dimensional templating software; Total hip arthroplasty