title: Laser method for intraoperative evaluation of lower extremity alignment: comparison of a novel technique to CT and a conventional method.
abstract: BACKGROUND
  Accurate restoration of mechanical alignment is an important factor in reconstructive surgery of the lower extremity. Conventional intraoperative methods, such as using an electrocautery cable, provide only a momentary evaluation of alignment. In this study, we evaluated a novel technique using a laser emitter, which projected the mechanical axis of the lower extremity, providing continuous intraoperative information on alignment.
  
  
  METHODS
  Alignment of 16 cadaver lower extremities was measured using the electrocautery cable method, the laser method, and CT scan as the standard measurement. The mechanical axis was defined by a line from the center of the femoral head to the center of the ankle. For simplifying measurements the intersection with the tibial plateau was divided into percentages from the medial border (0 %) to the lateral border (100 %). For using the laser method a laser emitting and laser catching device was developed, which is positioned and centered on the femoral head and the ankle using an image intensifier. By catching the laser on the knee region the actual mechanical axis is marked.
  
  
  RESULTS
  The data demonstrated good correlation of the laser method when compared to the cable method (P = 0.44). Comparison of the average mechanical axis between cable method and CT (P = 0.819) and laser method and CT (P = 0.647) did not show a statistically significant difference. Average radiation time in comparison between cable method and laser method showed a statistically significant difference (P = 0.013), with the laser method requiring more radiation time.
  
  
  CONCLUSIONS
  Determination of the mechanical axis during surgery remains a difficult clinical problem. Restoration of alignment is an important prognostic factor for surgical outcome. Based on these data, the laser method represents a simple, yet effective tool for continuous intraoperative evaluation of lower extremity alignment.
authors.affiliation: Trauma Department, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany, hawi.nael@mh-hannover.de.
authors.forename: Nael
authors.initials: N
authors.lastname: Hawi
authors.forename: Seth
authors.initials: S
authors.lastname: Yarboro
authors.forename: Eduardo M
authors.initials: EM
authors.lastname: Suero
authors.forename: Emmanouil
authors.initials: E
authors.lastname: Liodakis
authors.forename: Rupert
authors.initials: R
authors.lastname: Meller
authors.forename: Christian
authors.initials: C
authors.lastname: Krettek
authors.forename: Musa
authors.initials: M
authors.lastname: Citak
mesh_terms: D017760:Bone Malalignment / Q000517:prevention & control*; D002102:Cadaver; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery; D007834:Lasers; D035002:Lower Extremity / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D016343:Monitoring, Intraoperative / Q000295:instrumentation / Q000379:methods*; D019651:Plastic Surgery Procedures; D013977:Tibia / Q000601:surgery; D014057:Tomography, X-Ray Computed