title: Mid-term survival following primary hinged total knee replacement is good irrespective of the indication for surgery.
abstract: OBJECTIVE
  The use of 'hinged' knee prostheses for primary knee arthroplasty procedures is increasing. This analysis reports the rates of implant survival, modes of failure, revision details and functional outcomes with particular reference to the primary indication for surgery for a cohort of patients treated with primary hinged knee replacement.
  
  
  METHODS
  Systematic review with supplementary analysis using data from the National Joint Registry and Department of Health. Analysis included 964 patients undergoing primary hinged knee replacement between April 2003 and December 2010. Survival at a maximum of 7 years was calculated for the group as a whole and dependent upon the indication for surgery (osteoarthritis vs. rheumatoid/inflammatory arthritis vs. post-traumatic arthritis). Functional outcomes (pre- and post-operative Oxford Knee and Euroqol-5D scores and post-operative satisfaction) were available for 46 patients.
  
  
  RESULTS
  In total, 20 cases required revision. The 5-year survival rate (96.8% [95% CI 95.1-98.4%]) was not dependent upon the primary surgical indication (p = n.s.). The commonest reasons for revision were infection (8 cases), peri-prosthetic fracture (4 cases) and aseptic loosening (3 cases). Patients reported substantial improvements in their Oxford Knee Score (mean improvement = 17.6, [95% CI 14.4-20.8]) and EQ5D index (mean improvement = 0.357, [95% CI 0.248-0.467]). Levels of post-operative satisfaction were high.
  
  
  CONCLUSIONS
  Hinged knee replacement can be considered as a viable alternative to more traditional unconstrained designs in the complex primary setting. These findings are clinically relevant as they support the increasing use of hinged knee replacements for the arthritic knee in which there is concomitant severe bone loss, deformity or instability. Surgeons using these implants can have confidence that their mid-term performance is comparable to more conventional knee designs.
  
  
  METHODS
  Prospective cohort study, Level II.
authors.affiliation: National Joint Registry, Hemel Hempstead, UK, drpnbaker@hotmail.com.
authors.forename: Paul
authors.initials: P
authors.lastname: Baker
authors.forename: Rebecca
authors.initials: R
authors.lastname: Critchley
authors.forename: Andrew
authors.initials: A
authors.lastname: Gray
authors.forename: Simon
authors.initials: S
authors.lastname: Jameson
authors.forename: Paul
authors.initials: P
authors.lastname: Gregg
authors.forename: Andrew
authors.initials: A
authors.lastname: Port
authors.forename: David
authors.initials: D
authors.lastname: Deehan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000601:surgery*; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery*; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012042:Registries; D012086:Reoperation / Q000706:statistics & numerical data; D016896:Treatment Outcome