title: Comparison of extramedullary versus intramedullary referencing for tibial component alignment in total ankle arthroplasty.
abstract: BACKGROUND
  The majority of total ankle arthroplasty (TAA) systems use extramedullary alignment guides for tibial component placement. However, at least 1 system offers intramedullary referencing. In total knee arthroplasty, studies suggest that tibial component placement is more accurate with intramedullary referencing. The purpose of this study was to compare the accuracy of extramedullary referencing with intramedullary referencing for tibial component placement in total ankle arthroplasty.
  
  
  METHODS
  The coronal and sagittal tibial component alignment was evaluated on the postoperative weight-bearing anteroposterior (AP) and lateral radiographs of 236 consecutive fixed-bearing TAAs. Radiographs were measured blindly by 2 investigators. The postoperative alignment of the prosthesis was compared with the surgeon's intended alignment in both planes. The accuracy of tibial component alignment was compared between the extramedullary and intramedullary referencing techniques using unpaired t tests. Interrater and intrarater reliabilities were assessed with intraclass correlation coefficients (ICCs).
  
  
  RESULTS
  Eighty-three tibial components placed with an extramedullary referencing technique were compared with 153 implants placed with an intramedullary referencing technique. The accuracy of the extramedullary referencing was within a mean of 1.5 ± 1.4 degrees and 4.1 ± 2.9 degrees in the coronal and sagittal planes, respectively. The accuracy of intramedullary referencing was within a mean of 1.4 ± 1.1 degrees and 2.5 ± 1.8 degrees in the coronal and sagittal planes, respectively. There was a significant difference (P < .001) between the 2 techniques with respect to the sagittal plane alignment. Interrater ICCs for coronal and sagittal alignment were high (0.81 and 0.94, respectively). Intrarater ICCs for coronal and sagittal alignment were high for both investigators.
  
  
  CONCLUSIONS
  Initial sagittal plane tibial component alignment was notably more accurate when intramedullary referencing was used. Further studies are needed to determine the effect of this difference on clinical outcomes and long-term survivability of the implants.
  
  
  METHODS
  Level III, retrospective comparative study.
authors.affiliation: Department of Orthopaedic Surgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Samuel B
authors.initials: SB
authors.lastname: Adams
authors.forename: Constantine A
authors.initials: CA
authors.lastname: Demetracopoulos
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Viens
authors.forename: James K
authors.initials: JK
authors.lastname: DeOrio
authors.forename: Mark E
authors.initials: ME
authors.lastname: Easley
authors.forename: Robin M
authors.initials: RM
authors.lastname: Queen
authors.forename: James A
authors.initials: JA
authors.lastname: Nunley
mesh_terms: D058737:Arthroplasty, Replacement, Ankle / Q000295:instrumentation / Q000379:methods*; D017760:Bone Malalignment / Q000517:prevention & control; D006801:Humans; D007595:Joint Prosthesis; D017755:Prosthesis Fitting / Q000379:methods; D012189:Retrospective Studies; D013977:Tibia
keywords: component alignment; extramedullary referencing; intramedullary referencing; tibial component; total ankle arthroplasty