title: Antirotation pins improve stability of the compress limb salvage implant: a biomechanical study.
abstract: BACKGROUND
  Limb salvage implants that rely on compliant compression osseointegration to achieve bone fixation may achieve longer survivorship rates compared with traditional cemented or press-fit stemmed implants; however, failures resulting from rotational instability have been reported. The effect of using antirotation pins on the rotational stability of the fixation has not been well studied.
  
  
  OBJECTIVE
  We asked the following question: When tested in a cadaver model, does the use of antirotation pins increase the torque required to cause implant failure or rotation?
  
  
  METHODS
  Thirty-two cadaver femurs were divided into four groups of eight femurs. We compared the torque to failure among groups containing zero, one, two, three, and four pins using a servohydraulic testing device.
  
  
  RESULTS
  Adding antirotation pins increased the torque required to cause failure (R(2) = 0.77; p < 0.001). This increase was most notable in groups comparing zero pins with one pin (14 N-m, [95% CI, 10.9-17.1] versus 23 N-m, [95% CI 22.5-23.48]; p = 0.01) and two compared with three pins (29 N-m, [95% CI, 21.7-36.3] versus 42 N-m, [95% CI, 37.8-46.2]; p = 0.35).
  
  
  CONCLUSIONS
  It appears that the use of antirotation pins improves rotational stability of the compliant compression endoprosthesis. Although these findings need to be verified in a clinical study, the addition of antirotation pins may improve osteointegration and we have changed our practice to use a minimum of three antirotation pins when implanting this device.
  
  
  CONCLUSIONS
  Improvements in implant technology and surgical techniques may lead to improved clinical outcomes and patient quality of life. Addition of antirotation pins appears to improve implant stability and may decrease the need for revision surgery.
authors.affiliation: Department of Orthopaedic Surgery, Stanford University, 450 Broadway Street, MC 6342, Redwood City, CA, 94063, USA, ravedian@stanford.edu.
authors.forename: Raffi S
authors.initials: RS
authors.lastname: Avedian
authors.forename: Timothy
authors.initials: T
authors.lastname: Chen
authors.forename: Derek
authors.initials: D
authors.lastname: Lindsey
authors.forename: Ariel
authors.initials: A
authors.lastname: Palanca
authors.forename: David
authors.initials: D
authors.lastname: Mohler
mesh_terms: D001696:Biomechanical Phenomena; D001858:Bone Nails; D002102:Cadaver; D005269:Femur / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D023821:Limb Salvage / Q000009:adverse effects / Q000295:instrumentation*; D019637:Orthopedic Procedures / Q000009:adverse effects / Q000295:instrumentation*; D016348:Osseointegration; D011312:Pressure; D011474:Prosthesis Design; D011475:Prosthesis Failure; D019919:Prosthesis Implantation / Q000009:adverse effects / Q000295:instrumentation*; D011859:Radiography; D012399:Rotation; D013314:Stress, Mechanical; D019415:Torque