title: Patient-specific instrumentation development in TKA: 1st and 2nd generation designs in comparison with conventional instrumentation.
abstract: BACKGROUND
  This study was conducted to determine if the difference in magnetic resonance imaging (MRI)-based 2nd generation patient-specific instrumentation (PSI) design affects post-operative restoration of neutral mechanical alignment in total knee arthroplasty (TKA) compared with the 1st generation PSI design and conventional surgical techniques. In addition, it is aimed at elucidating whether PSI improves surgical efficiency with respect to operating room time, estimated blood loss and the number of instrument trays used intra-operatively.
  
  
  METHODS
  We report our experience in TKA using PSI techniques in 234 patients from August 2012 to March 2015. The patients were divided into 1st (n = 64) and 2nd (n = 70) generation PSI design. The control group (n = 100) underwent TKA with the conventional instrument technique.
  
  
  RESULTS
  The mean surgical time was significantly shorter in the 2nd generation PSI design (62.1 ± 12.1 min) than in the control group (80.6 ± 21.7 min; P < 0.001). A mechanical axis malalignment of >3° of the lower limb was observed in 5.7% of the patients in 2nd generation PSI design compared with 26.0% of the control group (P = 0.006). No significant difference in mechanical alignment on post-operative long alignment radiography was found between 20.3% of the patients in 1st generation PSI design and the control group (P = 0.584).
  
  
  CONCLUSIONS
  The 1st generation PSI design did not have a shorter surgical time or improved alignment compared with conventional instrumentation (CI). However, the use of the perfectly fitted 2nd generation PSI design was associated with improvements in both of these measurements. This study emphasizes the importance of PSI design in intra-operative and post-operative outcomes of TKA.
authors.affiliation: Department of Orthopaedic Surgery, Joint Reconstruction Center, Yonsei Sarang Hospital, 10 Hyoryeong-ro, Seocho-gu, Seoul, 06698, Republic of Korea.
authors.forename: Oh-Ryong
authors.initials: OR
authors.lastname: Kwon
authors.affiliation: Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea.
authors.forename: Kyoung-Tak
authors.initials: KT
authors.lastname: Kang
authors.affiliation: Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea.
authors.forename: Juhyun
authors.initials: J
authors.lastname: Son
authors.affiliation: Department of Orthopaedic Surgery, Joint Reconstruction Center, Yonsei Sarang Hospital, 10 Hyoryeong-ro, Seocho-gu, Seoul, 06698, Republic of Korea.
authors.forename: Dong-Suk
authors.initials: DS
authors.lastname: Suh
authors.affiliation: Department of Orthopaedic Surgery, Joint Reconstruction Center, Yonsei Sarang Hospital, 10 Hyoryeong-ro, Seocho-gu, Seoul, 06698, Republic of Korea.
authors.forename: Dong Beom
authors.initials: DB
authors.lastname: Heo
authors.affiliation: Department of Orthopaedic Surgery, Joint Reconstruction Center, Yonsei Sarang Hospital, 10 Hyoryeong-ro, Seocho-gu, Seoul, 06698, Republic of Korea. osygkoh@gmail.com.
authors.forename: Yong-Gon
authors.initials: YG
authors.lastname: Koh
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*; D016063:Blood Loss, Surgical; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery; D007720:Knee Prosthesis; D008279:Magnetic Resonance Imaging; D008297:Male; D061646:Operative Time; D011474:Prosthesis Design; D011859:Radiography; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*; D016896:Treatment Outcome
keywords: Design improvement; Patient-specific instrument; Total knee arthroplasty