title: Change in Talar Translation in the Coronal Plane After Mobile-Bearing Total Ankle Replacement and Its Association with Lower-Limb and Hindfoot Alignment.
abstract: BACKGROUND
  Mobile-bearing total ankle replacement (TAR) enables motion at the tibial implant-polyethylene insert interface. This motion could lead to coronal translation of the talus relative to the tibia and may affect radiographic outcome. We aimed to assess the translation of the talus before and after mobile-bearing TAR to determine whether translation of the talus after TAR is associated with coronal plane alignment of the lower limb and hindfoot as well as to investigate the complications associated with talar translation.
  
  
  METHODS
  In this retrospective cohort study, we enrolled 153 patients (159 ankles) with a minimum follow-up of 3 years who underwent mobile-bearing TAR. The location of the talus in the coronal plane was quantified with use of talar center migration (TCM) on anteroposterior radiographs both preoperatively and at postoperative intervals, and the relationship between them was investigated. Radiographic parameters in the coronal plane-including mechanical axis deviation (MAD), lateral distal tibial angle (LDTA), hindfoot alignment angle, and hindfoot moment arm-were measured. The relationship between TCM and radiographic parameters in the coronal plane was assessed in each group. The complications associated with talar translation were examined during the same period.
  
  
  RESULTS
  During the 36-month follow-up period, the postoperative TCM showed a strong relationship with the preoperative TCM. Moreover, MAD, LDTA, and hindfoot alignment were significantly related to talar translation (p < 0.01). Complications included medial malleolar impingement in 5 cases (including delayed medial malleolar fracture due to medial impingement in 2 cases), insert dislocation in 1 case, and edge-loading in 2 cases; all of the cases with complications demonstrated implant overhang with talar translation.
  
  
  CONCLUSIONS
  Talar translation in the coronal plane after mobile-bearing TAR correlates with the preoperative talar translation. Talar translation arises from deformities of MAD, LDTA, and hindfoot alignment, and it may be accompanied by various complications, as observed on coronal radiography. Therefore, additional realignment procedures for coronal malalignment should be considered to prevent talar translation after mobile-bearing TAR.
  
  
  METHODS
  Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: 1Seoul Foot and Ankle Center, Inje University Seoul Paik Hospital, Seoul, Republic of Korea 2Department of Orthopedic Surgery, Chuncheon Sacred Heart Hospital, Hallym University College of Medicine, Chuncheon, Republic of Korea 3Department of Biostatistics, Soonchunhyang University Hospital, College of Medicine, Seoul, Republic of Korea.
authors.forename: Young
authors.initials: Y
authors.lastname: Yi
authors.forename: Jae-Ho
authors.initials: JH
authors.lastname: Cho
authors.forename: Ji-Beom
authors.initials: JB
authors.lastname: Kim
authors.forename: Jae-Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Su-Yeon
authors.initials: SY
authors.lastname: Park
authors.forename: Woo Chun
authors.initials: WC
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000843:Ankle Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D058737:Arthroplasty, Replacement, Ankle / Q000379:methods*; D005260:Female; D006801:Humans; D007595:Joint Prosthesis; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012189:Retrospective Studies; D013628:Talus / Q000000981:diagnostic imaging / Q000601:surgery*; D016474:Weight-Bearing / Q000502:physiology*