title: Intramedullary nail fixation with posterior-to-anterior compared to transverse distal screw placement for tibiotalocalcaneal arthrodesis: a biomechanical investigation.
abstract: BACKGROUND
  Biomechanical studies on retrograde intramedullary fixation for tibiotalocalcaneal fusion have been reported, but no studies have investigated dorsiflexion stiffness, load-to-failure, fatigue endurance, and plastic deformation using different distal screw orientations. Also, no studies have examined the effect of bone density on different distal screw orientations while using a fatigue loading mode.
  
  
  METHODS
  Eight matched pairs of cadaver legs were used. In one leg from each pair an intramedullary nail was inserted with lateral-to-medial distal screws and in the other with posterior-to-anterior screws. These samples underwent dorsiflexion fatigue testing with determination of initial and final stiffness, load-to-failure, and degree of plastic deformation at failure. DEXA scanning was done of each cadaver specimen to determine bone mineral density. Statistical analysis was performed using the Student t-test and a Pearson correlation. Significance level was set at p < 0.05.
  
  
  RESULTS
  The specimens with posterior-to-anterior screws had a significantly higher fatigue endurance load-to-failure (1130.0 +/- 362.0 N compared to 801.0 +/- 227 N, p = 0.01). They also had significantly higher final stiffness (203.1 +/- 23.1 N/mm compared to 146.6 +/- 46.2 N/mm, p = 0.05) and lower plastic deformation (2.4 +/- 1.5 mm compared to 3.8 +/- 2.3 mm, p = 0.04). There was a statistically significant correlation between bone mineral density and the difference in construct deformation with posterior-to-anterior and lateral-to-medial screw orientation (r = 0.76, p = 0.03).
  
  
  CONCLUSIONS
  In this biomechanical investigation of tibiotalocalcaneal arthrodesis with intramedullary nail fixation, posterior-to-anterior distal screw orientation provided more stable fixation than lateral-to-medial screw orientation.
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Means
authors.forename: Brent G
authors.initials: BG
authors.lastname: Parks
authors.forename: Augustine
authors.initials: A
authors.lastname: Nguyen
authors.forename: Lew C
authors.initials: LC
authors.lastname: Schon
mesh_terms: D000368:Aged; D001174:Arthrodesis / Q000295:instrumentation* / Q000379:methods*; D001696:Biomechanical Phenomena; D015519:Bone Density; D001858:Bone Nails; D001863:Bone Screws; D002102:Cadaver; D002111:Calcaneus / Q000502:physiology / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013628:Talus / Q000502:physiology / Q000601:surgery; D013977:Tibia / Q000502:physiology / Q000601:surgery