title: Total hip arthroplasty using a cementless dual-mobility cup provides increased stability and favorable gait parameters at five years follow-up.
abstract: Rates of dislocation following primary total hip arthroplasty (THA) vary from 0.5 to 10%. Dual-mobility cups in THA demonstrate increased stability. Clinical outcomes following THA with dual-mobility cups have been reported, but gait has not been assessed. Therefore we performed a retrospective case control study to answer: (1) is gait better in patients following THA with a dual-mobility cup than in frail, elderly patients of the same age? (2) Are clinical outcomes better in patients following THA with a dual-mobility cup than in frail, elderly patients? (3) What is the dislocation rate following THA with a dual-mobility cup?
  
  
  
  We hypothesized that patients who underwent THA with a dual-mobility cup have a better gait compared to frail, elderly patients of the same age.
  
  
  
  Twenty patients (22 hips), mean age 79.9±7.7 (range, 62.3-88.3) years were assessed in this retrospective case-control series 5.6±1.4 (range: 4.1-8.8) years following dual-mobility cup THA. A reference group consisted of 72 "frail elderly" patients in a rehabilitation hospital for health problems unrelated to the lower limb, with no lower limb surgery or neurological conditions. Temporal and spatial gait performance were measured with four miniature gyroscopes, mounted on each thigh and calf, while patients walked freely along a 30m corridor. Harris Hip Score, WOMAC, radiological outcomes, and dislocation rate were determined.
  
  
  
  All gait parameters were better in the dual-mobility group compared to the frail elderly group. The dual-mobility group had a higher cadence (100.3 steps/minute versus 75.6 steps/minute), shorter (relative to gait cycle time) stance (61.6% versus 67.8%), shorter (relative to gait cycle time) double stance (23.3% versus 36.0%), longer stride (1.13m versus 0.80m), and faster walking speed (0.96m/s versus 0.52m/s). Range of motion of the shank, thigh and knee were better in the dual-mobility group. Harris Hip Score was 87.6±13.9 (range 51-100) and WOMAC score was 11.3±12.1 (range 0-34) in the THA group. We observed no dislocations.
  
  
  
  Gait patterns five years following THA with the dual-mobility cup were better or comparable to published study populations.
  
  
  
  III, retrospective case-control series.
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, centre hospitalier universitaire vaudois (CHUV) and University of Lausanne, bureau HO/03/321, avenue Pierre-Decker 4, 1011 Lausanne, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Acker
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, établissements hospitaliers du nord vaudois (EHNV), rue d'Entremonts 11, 1400 Yverdon-les-Bains, Switzerland.
authors.forename: J-F
authors.initials: JF
authors.lastname: Fischer
authors.affiliation: Laboratory of Movement Analysis and Measurement, Interinstitutional Centre of Translational Biomechanics (STI CBT), École polytechnique fédérale de Lausanne, ELH 132, Station 11, 1015 Lausanne, Switzerland.
authors.forename: K
authors.initials: K
authors.lastname: Aminian
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, centre hospitalier universitaire vaudois (CHUV) and University of Lausanne, bureau HO/03/321, avenue Pierre-Decker 4, 1011 Lausanne, Switzerland.
authors.forename: E
authors.initials: E
authors.lastname: Lécureux
authors.affiliation: Swiss BioMotion Lab, Department of Musculoskeletal Medicine (DAL), centre hospitalier universitaire vaudois (CHUV) and University of Lausanne, Bureau HO/03/321, avenue Pierre-Decker 4, 1011 Lausanne, Switzerland. Electronic address: brigitte.jolles-haeberli@chuv.ch.
authors.forename: B M
authors.initials: BM
authors.lastname: Jolles
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D016330:Frail Elderly; D005684:Gait; D006617:Hip Dislocation / Q000209:etiology*; D006621:Hip Joint / Q000503:physiopathology*; D006622:Hip Prosthesis / Q000009:adverse effects; D006801:Humans; D007593:Joint Instability / Q000209:etiology; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011859:Radiography; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D016896:Treatment Outcome; D016138:Walking
keywords: Dual-mobility cup; Gait analysis; Outcomes; Total hip arthroplasty