title: New classification focusing on the relationship between the attachment of the iliofemoral ligament and the course of the fracture line for intertrochanteric fractures.
abstract: OBJECTIVE
  There are various types of intertrochanteric fractures that are unstable pertrochanteric fractures of the hip. The aim of this study was to develop a systematic and comprehensive classification of intertrochanteric fractures.
  
  
  METHODS
  This study enrolled 74 patients with intertrochanteric fractures treated by us between 2012 and 2015. The fractures were classified using 3D-CT images taken immediately after the fractures occurred based on the course of the lateral fracture line (LFL) that extends through the lateral femoral cortex distal to the vastus ridge of the greater trochanter in the intertrochanteric area. Furthermore, the presence or absence of additional typical fractures was also studied. Then, 4 orthopedic specialists examined the 3D-CT images of 20 patients randomly selected from the 74 patients to evaluate both the inter-rater and intra-rater agreement levels.
  
  
  RESULTS
  Intertrochanteric fractures were classified into three types according to the LFL patterns. Type I (41.9%), the Lateral Wall Pattern, has a LFL that extends towards the lateral fiber bundle attachment area of the iliofemoral ligament. Type II (24.3%), the Transverse Pattern, has a LFL that extends towards the medial bundle attachment area. Type III (33.8%), the Reverse Oblique Pattern, has a LFL that extends between the lateral and medial fiber bundle area of the iliofemoral ligament. Each type showed characteristic displacement and was associated with various combinations of typical fractures (fracture across the intertrochanteric line, posteromedial fragment, including the lesser trochanter, posterolateral fragment posterior to the femoral greater trochanter, and banana-shaped big fragment, including both the greater trochanter and the lesser trochanter). The mean κ values for the interobserver and intraobserver agreement levels were 0.77 (0.70-0.85) and 0.76 (0.70-0.85), respectively, which were considered substantial agreement levels.
  
  
  CONCLUSIONS
  We believe our new classification is a useful communication tool for medical professionals in the diagnosis of fractures.
authors.affiliation: Department of Orthopedic Surgery, Juntendo University Shizuoka Hospital, 1129 nagaoka, Izunokuni-shi, Shizuoka, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Futamura
authors.affiliation: Department of Orthopedic Surgery, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, Japan. Electronic address: tobaba@juntendo.ac.jp.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Baba
authors.affiliation: Department of Orthopedic Surgery, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Homma
authors.affiliation: Department of Orthopedic Surgery, Juntendo University Shizuoka Hospital, 1129 nagaoka, Izunokuni-shi, Shizuoka, Japan.
authors.forename: Atsuhiko
authors.initials: A
authors.lastname: Mogami
authors.affiliation: Department of Orthopedic Surgery, Juntendo University Shizuoka Hospital, 1129 nagaoka, Izunokuni-shi, Shizuoka, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Kanda
authors.affiliation: Department of Orthopedic Surgery, Juntendo University Shizuoka Hospital, 1129 nagaoka, Izunokuni-shi, Shizuoka, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Obayashi
authors.affiliation: Orthopedic Trauma Center, Sapporo Tokushukai Hospital, 1-1-1Oyachihigashi, Atsubetsu-ku, Sapporoshi, Hokkaido, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Sato
authors.affiliation: Orthopedic Trauma Center, Sapporo Tokushukai Hospital, 1-1-1Oyachihigashi, Atsubetsu-ku, Sapporoshi, Hokkaido, Japan.
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Ueda
authors.affiliation: Orthopedic Trauma Center, Sapporo Tokushukai Hospital, 1-1-1Oyachihigashi, Atsubetsu-ku, Sapporoshi, Hokkaido, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Kurata
authors.affiliation: Orthopedic Trauma Center, Sapporo Tokushukai Hospital, 1-1-1Oyachihigashi, Atsubetsu-ku, Sapporoshi, Hokkaido, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Tsuji
authors.affiliation: Department of Orthopedic Surgery, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kaneko
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D001863:Bone Screws; D005260:Female; D005593:Fracture Fixation, Internal / Q000379:methods; D017102:Fracture Healing; D006620:Hip Fractures / Q000145:classification* / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D007085:Ilium / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery*; D021621:Imaging, Three-Dimensional; D007593:Joint Instability / Q000000981:diagnostic imaging; D008023:Ligaments, Articular / Q000033:anatomy & histology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000601:surgery*; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
keywords: 3D-CT; AO/OTA classification; Iliofemoral ligament; Interobserver agreement; Intertrochanteric fracture; Intraobserver agreement; Lateral fracture line; New classification; Pertrochanteric fracture; Reverse oblique fractures; Subtrochanteric fractures