title: In vitro evaluation of the effect lateral process talar excision on ankle and subtalar joint stability.
abstract: BACKGROUND
  Recent literature reflects a substantial increase in interest surrounding lateral talar process fractures. Previous anatomic investigations discovered that excision of a 1 cm3 fracture fragment from the lateral talar process involves approximately 100% of the lateral talocalcaneal ligament origin and 10% to 15% of both the posterior and anterior talofibular ligament insertions. The objective of this study was to determine the effect that excision of this 1 cm3 fragment has on ankle and subtalar joint stability.
  
  
  METHODS
  Ten fresh-frozen cadaver lower limbs were thawed before testing and placed in a clinical stress apparatus (Model SE 20, Telos, Marburg, Germany). Radiographs were taken before and after application of a 150 N of force. Three views (lateral, anteroposterior, 30-degree Bróden) were used to asses anterior tibiotalar translation (AT), talar tilt (TT), medial talocalcaneal motion (TCM), and talocalcaneal tilt (TCT) before and after excision of the 1 cm3 fragment the lateral talar process.
  
  
  RESULTS
  The mean increases in AT, TT, TCM and TCT after excision of the 1 cm3 fragment were: AT=1.0 mm+/-0.94 mm (p=0.0085); TT=0.4+/-0.52 degrees (p=0.0368); TCM=1.0 mm+/-1.25 mm (p=0.0319); TCT=1.2+/-1.32 degrees (p=0.0181).
  
  
  CONCLUSIONS
  Since it has been generally accepted that a 3 mm increase in AT, 3-degree increase in TT, 5-mm increase in TCM, more than 5-degree increase in TCT define instability of the ankle and subtalar joints, respectively. These results suggest that excision of a 1 cm3 fragment causes neither ankle nor subtalar instability as defined by radiographic stress examination.
authors.affiliation: Rhode Island Hospital, Department of Orthopedics, Providence, RI 02903, USA.
authors.forename: Phillip
authors.initials: P
authors.lastname: Langer
authors.forename: Florian
authors.initials: F
authors.lastname: Nickisch
authors.forename: David
authors.initials: D
authors.lastname: Spenciner
authors.forename: Braden
authors.initials: B
authors.lastname: Fleming
authors.forename: Christopher W
authors.initials: CW
authors.lastname: DiGiovanni
mesh_terms: D000368:Aged; D000843:Ankle Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002102:Cadaver; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011859:Radiography; D013380:Subtalar Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D013628:Talus / Q000601:surgery*