title: Changes in femoral posterior condylar offset and knee flexion after PCL-substituting total knee arthroplasty: comparison of anterior and posterior referencing systems.
abstract: OBJECTIVE
  Anterior referencing and posterior referencing are two major techniques for positioning femoral components and balancing the sagittal plane during total knee arthroplasty (TKA). The purpose of this study was to evaluate the changes in medial and lateral posterior condylar offset (PCO) after bilateral TKA using anterior referencing (AR) or posterior referencing (PR) systems and compare the effect of the PCO changes on knee flexion.
  
  
  METHODS
  Twenty female patients (mean age, 68.6 years) underwent bilateral TKA using the AR technique in one knee and the PR technique in the contralateral knee. Three-dimensional reconstructed computed tomographic images from the sagittal plane were used to evaluate PCO before and after arthroplasty. Knee Society scores and range of motion were evaluated postoperatively at a mean of 2.9 years.
  
  
  RESULTS
  Postoperative medial and lateral PCOs were significantly greater (p < 0.001 and p = 0.048, respectively) in the AR group (30.9 ± 2.2 and 29.1 ± 1.5 mm, respectively) than those in the PR group (29.1 ± 2.7 and 27.3 ± 2.3 mm, respectively). In addition, the degree of change in the PCO after TKA was greater in the AR group than in the PR group. On the final follow-up, no differences in the degree of knee flexion were observed between the two groups (124.7° for AR and 124.5° for PR). Knee Society scores were similar in the two groups both preoperatively and postoperatively. On the final follow-up, individual changes in the medial and lateral PCO were not associated with changes in the knee flexion angle.
  
  
  CONCLUSIONS
  Restoration of PCO after TKA was more accurate with the PR technique than with the AR technique. However, the postoperative differences in PCO showed no correlation with changes in knee flexion 2 years after PCL-substituting TKA.
  
  
  METHODS
  Therapeutic study, Level I.
authors.affiliation: Department of Orthopedic Surgery, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul, 110-744, South Korea.
authors.forename: Hyuksoo
authors.initials: H
authors.lastname: Han
authors.affiliation: Department of Biostatistics, Seoul National University Boramae Medical Center, 20 Boramae 5th Road, Dongjak-gu, Seoul, 156-707, South Korea.
authors.forename: Sohee
authors.initials: S
authors.lastname: Oh
authors.affiliation: Department of Orthopedic Surgery, Seoul National University Boramae Medical Center, 20 Boramae 5th Road, Dongjak-gu, Seoul, 156-707, South Korea.
authors.forename: Chong Bum
authors.initials: CB
authors.lastname: Chang
authors.affiliation: Department of Orthopedic Surgery, Seoul National University Boramae Medical Center, 20 Boramae 5th Road, Dongjak-gu, Seoul, 156-707, South Korea. ossbkang@gmail.com.
authors.forename: Seung-Baik
authors.initials: SB
authors.lastname: Kang
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D017760:Bone Malalignment; D004838:Epiphyses / Q000601:surgery; D005260:Female; D005269:Femur / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology* / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D056888:Patient Positioning; D011184:Postoperative Period; D011446:Prospective Studies; D016059:Range of Motion, Articular; D016037:Single-Blind Method; D014057:Tomography, X-Ray Computed
keywords: Anterior referencing; Knee flexion; Posterior condylar offset; Posterior referencing; Total knee arthroplasty; Total knee replacement