title: Ankle fracture spur sign is pathognomonic for a variant ankle fracture.
abstract: BACKGROUND
  The hyperplantarflexion variant ankle fracture is composed of a posterior tibial lip fracture with posterolateral and posteromedial fracture fragments separated by a vertical fracture line. This infrequently reported injury pattern often includes an associated "spur sign" or double cortical density at the inferomedial tibial metaphysis. The objective of this study was to quantitatively establish the association of the ankle fracture spur sign with the hyperplantarflexion variant ankle fracture.
  
  
  METHODS
  Our clinical database of operative ankle fractures was retrospectively reviewed for the incidence of hyperplantarflexion variant and nonvariant ankle fractures as determined by assessment of injury radiographs, preoperative advanced imaging, and intraoperative observation. Injury radiographs were then evaluated for the presence of the spur sign, and association between the spur sign and variant fractures was analyzed.
  
  
  RESULTS
  The incidence of the hyperplantarflexion variant fracture among all ankle fractures was 6.7% (43/640). The spur sign was present in 79% (34/43) of variant fractures and absent in all nonvariant fractures, conferring a specificity of 100% in identifying variant fractures. Positive predictive value and negative predictive value were 100% and 99%, respectively.
  
  
  CONCLUSIONS
  The ankle fracture spur sign was pathognomonic for the hyperplantarflexion variant ankle fracture. It is important to identify variant fractures preoperatively as patient positioning, operative approach, and fixation construct of variant fractures often differ from those employed for osteosynthesis of nonvariant fractures. Identification of the spur sign should prompt acquisition of advanced imaging to formulate an appropriate operative plan to address the variant fracture pattern.
  
  
  METHODS
  Level III, retrospective comparative study.
authors.affiliation: Orthopaedic Trauma Service, Hospital for Special Surgery, New York, NY, USA RichardHindsResearch@gmail.com.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Hinds
authors.affiliation: Hospital for Special Surgery, New York, NY, USA.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Garner
authors.affiliation: Hospital for Special Surgery, New York, NY, USA.
authors.forename: Lionel E
authors.initials: LE
authors.lastname: Lazaro
authors.affiliation: Hospital for Special Surgery, New York, NY, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Warner
authors.affiliation: Department of Radiology, Emergency and Musculoskeletal Division, Weill Cornell Medical College, New York, NY, USA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Loftus
authors.affiliation: Boston University Medical School, Boston, MA, USA.
authors.forename: Jacqueline F
authors.initials: JF
authors.lastname: Birnbaum
authors.affiliation: Department of Epidemiology and Biostatistics, Hospital for Special Surgery, New York, NY, USA.
authors.forename: Jayme C
authors.initials: JC
authors.lastname: Burket
authors.affiliation: Orthopaedic Trauma Service, Hospital for Special Surgery, New York, NY, USA New York Presbyterian Hospital, New York, NY, USA.
authors.forename: Dean G
authors.initials: DG
authors.lastname: Lorich
mesh_terms: D000328:Adult; D000368:Aged; D064386:Ankle Fractures / Q000145:classification / Q000000981:diagnostic imaging*; D016512:Ankle Injuries / Q000000981:diagnostic imaging*; D000843:Ankle Joint / Q000000981:diagnostic imaging; D005260:Female; D005593:Fracture Fixation, Internal / Q000379:methods; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013977:Tibia / Q000000981:diagnostic imaging / Q000293:injuries; D014057:Tomography, X-Ray Computed
keywords: ankle; fracture; hyperplantarflexion; spur sign; variant