title: Gravity reduces the tibia when using a tibial guide that targets the intercondylar roof.
abstract: BACKGROUND
  Reduction of the tibia relative to the femur with the knee in maximum extension is required to correctly position the tibial tunnel in the sagittal plane when using a guide that targets the intercondylar roof. The authors found no studies that determined (1) whether gravity reduces the tibia and (2) whether roof impingement is prevented without a roofplasty and without positioning the tibial tunnel too posteriorly.
  
  
  METHODS
  The position of the tibia relative to the femur was measured from a lateral radiograph of the treated knee in maximum extension with and without the tibial guide and of the contralateral normal knee in extension in single-leg stance (control).
  
  
  RESULTS
  The position of the tibia with and without the tibial guide was not different (P = .33, not significant) and was only 0.7 mm more posterior than the control knee (P = .0075). A roofplasty was not required, and the clearance was 2 mm or less.
  
  
  CONCLUSIONS
  Gravity reduces the tibia on the femur when using a guide that targets the intercondylar roof. The use of a tibial guide that targets the intercondylar roof prevents roof impingement without a roofplasty and without positioning the tibial tunnel too posteriorly.
authors.affiliation: University of California, Davis, USA. sebhowell@mac.com <sebhowell@mac.com>
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Howell
authors.forename: Keith W
authors.initials: KW
authors.lastname: Lawhorn
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000601:surgery*; D001858:Bone Nails; D005260:Female; D005269:Femur / Q000033:anatomy & histology; D006112:Gravitation; D006801:Humans; D007718:Knee Injuries / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000295:instrumentation*; D011187:Posture; D011859:Radiography; D019651:Plastic Surgery Procedures / Q000295:instrumentation; D013977:Tibia / Q000033:anatomy & histology* / Q000502:physiology