title: What Is the Expected Learning Curve in Computer-assisted Navigation for Bone Tumor Resection?
abstract: BACKGROUND
  Computer navigation during surgery can help oncologic surgeons perform more accurate resections. However, some navigation studies suggest that this tool may result in unique intraoperative problems and increased surgical time. The degree to which these problems might diminish with experience-the learning curve-has not, to our knowledge, been evaluated for navigation-assisted tumor resections.
  
  
  OBJECTIVE
  (1) What intraoperative technical problems were observed during the first 2 years using navigation? (2) What was the mean time for navigation procedures and the time improvement during the learning curve? (3) Have there been any differences in the accuracy of the registration technique that occurred over time? (4) Did navigation achieve the goal of achieving a wide bone margin?
  
  
  METHODS
  All patients who underwent preoperative virtual planning for tumor bone resections and operated on with navigation assistance from 2010 to 2012 were prospectively collected. Two surgeons (GLF, LAA-T) performed the intraoperative navigation assistance. Both surgeons had more than 5 years of experience in orthopaedic oncology with more than 60 oncology cases per year per surgeon. This study includes from the very first patients performed with navigation. Although they did not take any formal training in orthopaedic oncology navigation, both surgeons were trained in navigation for knee prostheses. Between 2010 and 2012, we performed 124 bone tumor resections; of these, 78 (63%) cases were resected using intraoperative navigation assistance. During this period, our general indications for use of navigation included pelvic and sacral tumors and those tumors that were reconstructed with massive bone allografts to obtain precise matching of the host and allograft osteotomies. Seventy-eight patients treated with this technology were included in the study. Technical problems (crashes) and time for the navigation procedure were reported after surgery. Accuracy of the registration technique was defined and the surgical margins of the removed specimen were determined by an experienced bone pathologist after the surgical procedure as intralesional, marginal, or wide margins. To obtain these data, we performed a chart review and review of operative notes.
  
  
  RESULTS
  In four patients (of 78 [5%]), the navigation was not completed as a result of technical problems; all occurred during the first 20 cases of the utilization of this technology. The mean time for navigation procedures during the operation was 31 minutes (range, 11-61 minutes), and the early navigations took more time (the regression analysis shielded R2= 0.35 with p < 0.001). The median registration error was 0.6 mm (range, 0.3-1.1 mm). Registration did not improve over time (the regression analysis slope estimate is -0.014, with R2= 0.026 and p = 0.15). Histological examinations of all specimens showed a wide bone tumor margin in all patients. However, soft tissue margins were wide in 58 cases and marginal in 20.
  
  
  CONCLUSIONS
  We conclude that navigation may be useful in achieving negative bony margins, but we cannot state that it is more effective than other means for achieving this goal. Technical difficulty precluded the use of navigation in 5% of cases in this series. Navigation time decreased with more experience in the procedure but with the numbers available, we did not improve the registration error over time. Given these observations and the increased time and expense of using navigation, larger studies are needed to substantiate the value of this technology for routine use.
  
  
  METHODS
  Level IV, therapeutic study.
authors.affiliation: Carlos E. Ottolenghi Institute of Orthopedics, Italian Hospital of Buenos Aires, Potosí 4247, 1199, Buenos Aires, Argentina. german.farfalli@hospitalitaliano.org.ar.
authors.forename: Germán L
authors.initials: GL
authors.lastname: Farfalli
authors.affiliation: Carlos E. Ottolenghi Institute of Orthopedics, Italian Hospital of Buenos Aires, Potosí 4247, 1199, Buenos Aires, Argentina.
authors.forename: José I
authors.initials: JI
authors.lastname: Albergo
authors.affiliation: Carlos E. Ottolenghi Institute of Orthopedics, Italian Hospital of Buenos Aires, Potosí 4247, 1199, Buenos Aires, Argentina.
authors.forename: Lucas E
authors.initials: LE
authors.lastname: Ritacco
authors.affiliation: Carlos E. Ottolenghi Institute of Orthopedics, Italian Hospital of Buenos Aires, Potosí 4247, 1199, Buenos Aires, Argentina.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Ayerza
authors.affiliation: Department of Bioengineering, Instituto Tecnologico de Buenos Aires, Buenos Aires, Argentina.|CONICET (Consejo Nacional de Investigaciones Cientificas y Tecnicas), Buenos Aires, Argentina.
authors.forename: Federico E
authors.initials: FE
authors.lastname: Milano
authors.affiliation: Carlos E. Ottolenghi Institute of Orthopedics, Italian Hospital of Buenos Aires, Potosí 4247, 1199, Buenos Aires, Argentina.
authors.forename: Luis A
authors.initials: LA
authors.lastname: Aponte-Tinao
mesh_terms: D000293:Adolescent; D000328:Adult; D001118:Argentina; D001859:Bone Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D002648:Child; D002675:Child, Preschool; D002983:Clinical Competence; D005260:Female; D006801:Humans; D059032:Learning Curve; D008297:Male; D000072662:Margins of Excision; D008875:Middle Aged; D061646:Operative Time; D010027:Osteotomy / Q000009:adverse effects / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted / Q000009:adverse effects; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D055815:Young Adult