title: Determining the Cost-Savings Threshold and Alignment Accuracy of Patient-Specific Instrumentation in Total Ankle Replacements.
abstract: BACKGROUND
  Traditional intraoperative referencing for total ankle replacements (TARs) involves multiple steps and fluoroscopic guidance to determine mechanical alignment. Recent adoption of patient-specific instrumentation (PSI) allows for referencing to be determined preoperatively, resulting in less steps and potentially decreased operative time. We hypothesized that usage of PSI would result in decreased operating room time that would offset the additional cost of PSI compared with standard referencing (SR). In addition, we aimed to compare postoperative radiographic alignment between PSI and SR.
  
  
  METHODS
  Between August 2014 and September 2015, 87 patients undergoing TAR were enrolled in a prospectively collected TAR database. Patients were divided into cohorts based on PSI vs SR, and operative times were reviewed. Radiographic alignment parameters were retrospectively measured at 6 weeks postoperatively. Time-driven activity-based costing (TDABC) was used to derive direct costs. Cost vs operative time-savings were examined via 2-way sensitivity analysis to determine cost-saving thresholds for PSI applicable to a range of institution types. Cost-saving thresholds defined the price of PSI below which PSI would be cost-saving. A total of 35 PSI and 52 SR cases were evaluated with no significant differences identified in patient characteristics.
  
  
  RESULTS
  Operative time from incision to completion of casting in cases without adjunct procedures was 127 minutes with PSI and 161 minutes with SR ( P < .05). PSI demonstrated similar postoperative accuracy to SR in coronal tibial-plafond alignment (1.1 vs 0.3 degrees varus, P = .06), tibial-plafond alignment (0.3 ± 2.1 vs 1.1 ± 2.1 degrees varus, P = .06), and tibial component sagittal alignment (0.7 vs 0.9 degrees plantarflexion, P = .14). The TDABC method estimated a PSI cost-savings threshold range at our institution of $863 below which PSI pricing would provide net cost-savings. Two-way sensitivity analysis generated a globally applicable cost-savings threshold model based on institution-specific costs and surgeon-specific time-savings.
  
  
  CONCLUSIONS
  This study demonstrated equivalent postoperative TAR alignment with PSI and SR referencing systems but with a significant decrease in operative time with PSI. Based on TDABC and associated sensitivity analysis, a cost-savings threshold of $863 was identified for PSI pricing at our institution below which PSI was less costly than SR. Similar internal cost accounting may benefit health care systems for identifying cost drivers and obtaining leverage during price negotiations.
  
  
  METHODS
  Level III, therapeutic study.
authors.affiliation: 1 Rush University Medical Center, Chicago, IL, USA.
authors.forename: Kamran S
authors.initials: KS
authors.lastname: Hamid
authors.affiliation: 2 Duke University Medical Center, Durham, NC, USA.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Matson
authors.affiliation: 3 Hospital for Special Surgery, New York City, NY, USA.
authors.forename: Benedict U
authors.initials: BU
authors.lastname: Nwachukwu
authors.affiliation: 2 Duke University Medical Center, Durham, NC, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Scott
authors.affiliation: 2 Duke University Medical Center, Durham, NC, USA.
authors.forename: Richard C
authors.initials: RC
authors.lastname: Mather
authors.affiliation: 2 Duke University Medical Center, Durham, NC, USA.
authors.forename: James K
authors.initials: JK
authors.lastname: DeOrio
mesh_terms: D000368:Aged; D000843:Ankle Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D058737:Arthroplasty, Replacement, Ankle / Q000191:economics / Q000295:instrumentation*; D017046:Cost Savings; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000191:economics; D007595:Joint Prosthesis; D008297:Male; D008875:Middle Aged; D061646:Operative Time; D011859:Radiography; D013628:Talus / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D013977:Tibia / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed
keywords: accuracy; alignment; analysis; cost; cost-effectiveness; cost-savings; patient-specific instrumentation; sensitivity; threshold; total ankle replacement