title: Total hip arthroplasty dislocation rate following isolated cup revision using Hueter's direct anterior approach on a fracture table.
abstract: BACKGROUND
  Instability is a major complication after revision total hip arthroplasty. Studies in the literature have shown that the dislocation rate after primary arthroplasties by anterior approach on a fracture table is satisfactory, but the rate of instability following revision surgery is not known.
  
  
  OBJECTIVE
  We hypothesized that the Hueter direct anterior approach would result in a lower rate of postoperative dislocation following revision surgery. This hypothesis was tested in a series of isolated acetabular component replacements.
  
  
  METHODS
  Seventy-three consecutive isolated acetabular component replacements were performed between January 2000 and December 2007. Twelve revisions using constrained liners or dual mobility cups were excluded, thus 61 revisions in 59 patients, mean age 65.8-year-old (range 27-86) were included. The indications for revision arthroplasty were: 51 (83.6%) cases of aseptic loosening, five (8.2%) non-integration of cementless cups, three (4.9%) cases of instability, one (1.6%) case of impingement with the psoas and one (1.6%) case of excessive (3cm) lengthening. Acetabular bone defects were moderate, with 12 stage I, 26 stage II, 19 stage III, and only four stage IV defects on the SOFCOT bone stock deficiency score. There was no acetabular reconstruction in 18 cases, while there were four isolated reconstruction cages and 39 cages with a graft. The replacement cup was cemented in 52 cases and cementless in nine. Inclination and anteversion were measured by the Pradhan method on standard X-rays.
  
  
  RESULTS
  Results were evaluated after a mean follow-up of 2.4 years±1.7 years (1-7 years). Four dislocations were observed (6.6%) all anterior and early in the postoperative period (less than 2 months): three patients had a single episode of dislocation and one patient again underwent revision cup replacement by Hueter anterior approach for recurrent anterior dislocation. The only factor associated with a risk of dislocation was a high body mass index: 29.7±0.8 in the group with dislocation compared to 25.6±3.2 in the group without (P=0.008). A high number of prior interventions was also a significant risk factor (P=0.045). On the other hand, there was no difference in cup inclination or femoral offset between the group with dislocation and that without.
  
  
  CONCLUSIONS
  Although the rate of dislocation is higher than after primary THA by anterior approach, it remains acceptable for revision THA and is similar to rates observed with other approaches. The literature does not clearly establish that one surgical approach is better than another in terms of instability. This study was limited by the absence of CT-scan measurements of component orientation both preoperatively to evaluate the femoral component which is preserved, as well as during follow-up to evaluate cup angle and compare the groups with and without dislocation.
  
  
  CONCLUSIONS
  The Hueter direct anterior approach is a viable option for isolated cup revision, as long as femoral loosening has been excluded, and the orientation of the preserved femoral component is known.
  
  
  METHODS
  Level IV; retrospective study.
authors.affiliation: Diaconesses and Croix Saint-Simon Hospitals Group, Department of bone surgery and Traumatology, 125, rue d'Avron, 75020 Paris, France. cog20002002@yahoo.fr
authors.forename: A
authors.initials: A
authors.lastname: Cogan
authors.forename: S
authors.initials: S
authors.lastname: Klouche
authors.forename: P
authors.initials: P
authors.lastname: Mamoudy
authors.forename: E
authors.initials: E
authors.lastname: Sariali
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D005260:Female; D006617:Hip Dislocation / Q000453:epidemiology*; D006801:Humans; D008297:Male; D011475:Prosthesis Failure; D012086:Reoperation; D012189:Retrospective Studies