title: Value of the cumulative sum test for the assessment of a learning curve: Application to the introduction of patient-specific instrumentation for total knee arthroplasty in an academic department.
abstract: BACKGROUND
  The purpose of the study was to use the cumulative summation (CUSUM) test to assess the learning curve during the introduction of a new surgical technique (patient-specific instrumentation) in total knee arthroplasty (TKA) in an academic department.
  
  
  METHODS
  The first 50TKAs operated on at an academic department using patient-specific templates (PSTs) were scheduled to enter the study. All patients had a preoperative computed tomography scan evaluation to plan bone resections. The PSTs were positioned intraoperatively according to the best-fit technique and their three-dimensional orientation was recorded by a navigation system. The position of the femur and tibia PST was compared to the planned position for four items for each component: coronal and sagittal orientation, medial and lateral height of resection. Items were summarized to obtain knee, femur and tibia PST scores, respectively. These scores were plotted according to chronological order and included in a CUSUM analysis. The tested hypothesis was that the PST process for TKA was immediately under control after its introduction.
  
  
  RESULTS
  CUSUM test showed that positioning of the PST significantly differed from the target throughout the study. There was a significant difference between all scores and the maximal score. No case obtained the maximal score of eight points. The study was interrupted after 20 cases because of this negative evaluation.
  
  
  CONCLUSIONS
  The CUSUM test is effective in monitoring the learning curve when introducing a new surgical procedure. Introducing PST for TKA in an academic department may be associated with a long-lasting learning curve. The study was registered on the clinical.gov website (Identifier NCT02429245).
authors.affiliation: Centre for Orthopaedic and Hand Surgery (CCOM), University Hospital of Strasbourg, Avenue Baumann, Illkirch-Graffenstaden, France; Department of Orthopaedic and Trauma Surgery, "Magna Graecia" University, Viale Europa, Catanzaro, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: De Gori
authors.affiliation: Centre for Orthopaedic and Hand Surgery (CCOM), University Hospital of Strasbourg, Avenue Baumann, Illkirch-Graffenstaden, France.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Adamczewski
authors.affiliation: Centre for Orthopaedic and Hand Surgery (CCOM), University Hospital of Strasbourg, Avenue Baumann, Illkirch-Graffenstaden, France. Electronic address: jean-yves.jenny@chru-strasbourg.fr.
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Jenny
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000193:education* / Q000379:methods; D004521:Educational Measurement / Q000379:methods*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery; D059032:Learning Curve; D008297:Male; D020370:Osteoarthritis, Knee / Q000601:surgery; D011300:Preoperative Care; D011446:Prospective Studies; D025321:Surgery, Computer-Assisted; D014057:Tomography, X-Ray Computed
keywords: Cumulative sum test; Learning curve; Patient-specific instrumentation; Total knee arthroplasty