title: Comparative Epidemiology of Revision Arthroplasty: Failed THA Poses Greater Clinical and Economic Burdens Than Failed TKA.
abstract: BACKGROUND
  Revision THA and TKA are growing and important clinical and economic challenges. Healthcare systems tend to combine revision joint replacement procedures into a single service line, and differences between revision THA and revision TKA remain incompletely characterized. These differences carry implications for guiding care and resource allocation. We therefore evaluated epidemiologic trends associated with revision THAs and TKAs.
  
  
  OBJECTIVE
  We sought to determine differences in (1) the number of patients undergoing revision TKA and THA and respective demographic trends; (2) differences in the indications for and types of revision TKA and THA; (3) differences in patient severity of illness scoring between THA and TKA; and (4) differences in resource utilization (including cost and length of stay [LOS]) between revision THA and TKA.
  
  
  METHODS
  The Nationwide Inpatient Sample (NIS) was used to evaluate 235,857 revision THAs and 301,718 revision TKAs between October 1, 2005 and December 31, 2010. Patient characteristics, procedure information, and resource utilization were compared across revision THAs and TKAs. A revision burden (ratio of number of revisions to total number of revision and primary surgeries) was calculated for hip and knee procedures. Severity of illness scoring and cost calculations were derived from the NIS. As our study was principally descriptive, statistical analyses generally were not performed; however, owing to the large sample size available to us through this NIS analysis, even small observed differences presented are likely to be highly statistically significant.
  
  
  RESULTS
  Revision TKAs increased by 39% (revision burden, 9.1%-9.6%) and THAs increased by 23% (revision burden, 15.4%-14.6%). Revision THAs were performed more often in older patients compared with revision TKAs. Periprosthetic joint infection (25%) and mechanical loosening (19%) were the most common reasons for revision TKA compared with dislocation (22%) and mechanical loosening (20%) for revision THA. Full (all-component) revision was more common in revision THAs (43%) than in TKAs (37%). Patients who underwent revision THA generally were sicker (> 50% major severity of illness score) than patients who underwent revision TKA (65% moderate severity of illness score). Mean LOS was longer for revision THAs than for TKAs. Mean hospitalization costs were slightly higher for revision THA (USD 24,697 +/- USD 40,489 [SD]) than revision TKA (USD 23,130 +/- USD 36,643 [SD]). Periprosthetic joint infection and periprosthetic fracture were associated with the greatest LOS and costs for revision THAs and TKAs.
  
  
  CONCLUSIONS
  These data could prove important for healthcare systems to appropriately allocate resources to hip and knee procedures: the revision burden for THA is 52% greater than for TKA, but revision TKAs are increasing at a faster rate. Likewise, the treating clinician should understand that while both revision THAs and TKAs bear significant clinical and economic costs, patients undergoing revision THA tend to be older, sicker, and have greater costs of care.
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, USA, kevin.bozic@ucsf.edu.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Bozic
authors.forename: Atul F
authors.initials: AF
authors.lastname: Kamath
authors.forename: Kevin
authors.initials: K
authors.lastname: Ong
authors.forename: Edmund
authors.initials: E
authors.lastname: Lau
authors.forename: Steve
authors.initials: S
authors.lastname: Kurtz
authors.forename: Vanessa
authors.initials: V
authors.lastname: Chan
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Vail
authors.forename: Harry
authors.initials: H
authors.lastname: Rubash
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Berry
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000191:economics* / Q000295:instrumentation / Q000639:trends; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000191:economics* / Q000295:instrumentation / Q000639:trends; D005260:Female; D017048:Health Care Costs / Q000639:trends; D006295:Health Resources / Q000191:economics* / Q000639:trends; D006301:Health Services Needs and Demand / Q000191:economics; D006622:Hip Prosthesis; D006801:Humans; D007720:Knee Prosthesis; D007902:Length of Stay / Q000191:economics; D008297:Male; D008875:Middle Aged; D020380:Needs Assessment / Q000191:economics; D057068:Periprosthetic Fractures / Q000191:economics / Q000453:epidemiology / Q000601:surgery; D011183:Postoperative Complications / Q000175:diagnosis / Q000191:economics* / Q000453:epidemiology / Q000601:surgery*; D015995:Prevalence; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation / Q000191:economics; D012307:Risk Factors; D013530:Surgical Wound Infection / Q000191:economics / Q000453:epidemiology / Q000601:surgery; D013997:Time Factors; D017211:Treatment Failure; D014481:United States / Q000453:epidemiology