title: Enhanced cephalomedullary nail lag screw placement and intraoperative tip-apex distance measurement with a novel computer assisted surgery system.
abstract: OBJECTIVE
  The goal of this study was to evaluate the ability of a novel computer assisted surgery system to guide ideal placement of a lag screw during cephalomedullary nailing and then accurately measure the tip-apex distance (TAD) measurement intraoperatively.
  
  
  METHODS
  Retrospective case review.
  
  
  METHODS
  Level II trauma hospital.
  
  
  METHODS
  The initial 98 consecutive clinical cases treated with a cephalomedullary nail in conjunction with a novel computer assisted surgery system were retrospectively reviewed.
  
  
  METHODS
  A novel computer assisted surgery system was utilized to enhance lag screw placement during cephalomedullary nailing procedures. The computer assisted surgery system calculates the TAD intraoperatively after final lag screw placement.
  
  
  METHODS
  The ideal TAD was considered to be within a range of 5mm-20mm. The ability of the computer assisted surgery system (CASS) to assist in placement of a lag screw within the ideal TAD was evaluated. Intraoperative TAD measurements provided by the computer assisted surgery system were then compared to standard postoperative TAD measurements on PACS (picture archiving and communication system) images to determine whether these measurements are equivalent.
  
  
  RESULTS
  79 cases (80.6%) were available with complete information for a retrospective review. All cases had CASS TAD and PACS TAD measurements >5mm and<20mm. In addition, no significant difference could be detected between the intraoperative CASS TAD and the postoperative PACS TAD (p=0.374, Wilcoxon Test; p=0.174, paired T-Test). A cut-out rate of 0% was observed in all patients who were treated with CASS in this case series (95% CI: 0 - 3.01%).
  
  
  CONCLUSIONS
  The novel computer assisted surgery system tested here is an effective and reliable adjunct that can be utilized for optimal lag screw placement in cephalomedullary nailing procedures. The computer assisted surgery system provides an accurate intraoperative TAD measurement that is equivalent to the standard postoperative measurement utilizing PACS images.
  
  
  METHODS
  Therapeutic Level IV.
authors.affiliation: Department of Orthopaedic Surgery, St. Cloud Orthopedics and St. Cloud Hospital, St. Cloud, MN, United States. Electronic address: mkuhl@stcloudorthopedics.com.
authors.forename: Mitchell
authors.initials: M
authors.lastname: Kuhl
authors.affiliation: Scientific Research and Statistics with Stryker, Trauma and Extremities, Kiel, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Beimel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001858:Bone Nails; D001863:Bone Screws; D019544:Equipment Failure Analysis; D005260:Female; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation / Q000379:methods; D006620:Hip Fractures / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted
keywords: Cephalomedullary nailing; Computer assisted surgery; Hip fractures; Tip apex distance