title: Tumor resection at the pelvis using three-dimensional planning and patient-specific instruments: a case series.
abstract: BACKGROUND
  Sarcomas are associated with a relatively high local recurrence rate of around 30 % in the pelvis. Inadequate surgical margins are the most important reason. However, obtaining adequate margins is particularly difficult in this anatomically demanding region. Recently, three-dimensional (3-D) planning, printed models, and patient-specific instruments (PSI) with cutting blocks have been introduced to improve the precision during surgical tumor resection. This case series illustrates these modern 3-D tools in pelvic tumor surgery.
  
  
  METHODS
  The first consecutive patients with 3-D-planned tumor resection around the pelvis were included in this retrospective study at a University Hospital in 2015. Detailed information about the clinical presentation, imaging techniques, preoperative planning, intraoperative surgical procedures, and postoperative evaluation is provided for each case. The primary outcome was tumor-free resection margins as assessed by a postoperative computed tomography (CT) scan of the specimen. The secondary outcomes were precision of preoperative planning and complications.
  
  
  RESULTS
  Four patients with pelvic sarcomas were included in this study. The mean follow-up was 7.8 (range, 6.0-9.0) months. The combined use of preoperative planning with 3-D techniques, 3-D-printed models, and PSI for osteotomies led to higher precision (maximal (max) error of 0.4 centimeters (cm)) than conventional 3-D planning and freehand osteotomies (max error of 2.8 cm). Tumor-free margins were obtained where measurable (n = 3; margins were not assessable in a patient with curettage). Two insufficiency fractures were noted postoperatively.
  
  
  CONCLUSIONS
  Three-dimensional planning as well as the intraoperative use of 3-D-printed models and PSI are valuable for complex sarcoma resection at the pelvis. Three-dimensionally printed models of the patient anatomy may help visualization and precision. PSI with cutting blocks help perform very precise osteotomies for adequate resection margins.
authors.affiliation: Department of Orthopedics, Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008, Zurich, Switzerland. thorsten.jentzsch@balgrist.ch.
authors.forename: Thorsten
authors.identifier: http://orcid.org/0000-0002-6133-3314
authors.initials: T
authors.lastname: Jentzsch
authors.affiliation: Computer Assisted Research and Development (CARD) Group, Balgrist University Hospital, University of Zurich, Zurich, Switzerland.
authors.forename: Lazaros
authors.initials: L
authors.lastname: Vlachopoulos
authors.affiliation: Computer Assisted Research and Development (CARD) Group, Balgrist University Hospital, University of Zurich, Zurich, Switzerland.
authors.forename: Philipp
authors.initials: P
authors.lastname: Fürnstahl
authors.affiliation: Department of Orthopedics, Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008, Zurich, Switzerland.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Müller
authors.affiliation: Department of Orthopedics, Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008, Zurich, Switzerland.
authors.forename: Bruno
authors.initials: B
authors.lastname: Fuchs
mesh_terms: D000293:Adolescent; D000328:Adult; D001859:Bone Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007085:Ilium / Q000000981:diagnostic imaging / Q000601:surgery; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D000072662:Margins of Excision; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control*; D010027:Osteotomy / Q000295:instrumentation* / Q000379:methods*; D010347:Patient Care Planning; D066230:Patient-Specific Modeling; D010388:Pelvis / Q000000981:diagnostic imaging*; D012189:Retrospective Studies; D012446:Sacroiliac Joint / Q000000981:diagnostic imaging / Q000601:surgery; D012509:Sarcoma / Q000000981:diagnostic imaging / Q000601:surgery*; D014057:Tomography, X-Ray Computed
keywords: 3-D-printed models; Patient-specific guides (PSG); Patient-specific instruments (PSI); Patient-specific templates (PST); Pelvis; Resection margins; Sarcomas; Three-dimensional (3-D, 3D) planning