title: Compression forces of internal and external ankle fixation devices with simulated bone resorption.
abstract: BACKGROUND
  Internal and external fixation techniques have been developed to provide rigidity and stability to a fusion site such as in tibiotalocalcaneal (TTC) arthrodesis. Compression of the fusion site plays an integral role in primary bone healing, though little work has been done to quantify the compressive force values of ankle fixation devices.
  
  
  METHODS
  Using synthetic and cadaveric bone models, a Newdeal/Integra PantaNail and DePuy VersaNail were tested as compressive intramedullary (IM) nails while an Encore True/Lok and an Ace-Fischer frame were tested as external fixators.
  
  
  RESULTS
  The PantaNail experienced maximum compressive loads of 1898 and 1255 N in synthetic and cadaveric constructs, respectively. The VersaNail experienced max compressive loads 388 N during installation. All IM nails tested experienced decreased compressive loads after removal of the external guide and instrumentation. The external fixators were loaded to approximately 1200 N in both synthetic and cadaveric constructs. The decrease in compressive load was recorded as a function of simulated fusion site bone resorption for all devices. The IM nails experienced a 90% reduction in load with less than 1 mm of resorption, while the external fixators held 50% load for over 4 mm of resorption. These data were verified using a simple constitutive model of IM nails and external fixators.
  
  
  CONCLUSIONS
  Intramedullary nails are capable of generating compression, however, are unable to provide sustained compression for any considerable amount of resorption. External fixators are inherently capable of applying and sustaining greater amounts of compression.
  
  
  CONCLUSIONS
  Surgeons who perform TTC arthrodesis procedures should be aware of a device's ability to generate and sustain compression with respect to bone resorption.
authors.affiliation: MedShape Solution, Inc., Research and Development, 1575 Northside Drive, Suite 440, Atlanta, GA 30318, USA. chris.yakacki@medshape.com
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Yakacki
authors.forename: Heidi F
authors.initials: HF
authors.lastname: Khalil
authors.forename: Sean A
authors.initials: SA
authors.lastname: Dixon
authors.forename: Ken
authors.initials: K
authors.lastname: Gall
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Pacaccio
mesh_terms: D000368:Aged; D016512:Ankle Injuries / Q000601:surgery*; D001858:Bone Nails; D001862:Bone Resorption; D002102:Cadaver; D016267:External Fixators; D005592:Fracture Fixation / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D008954:Models, Biological; D013314:Stress, Mechanical