In general, patients who underwent revision THA had more medical comorbidities than did patients undergoing revision TKA. Patients who had revision THAs were more likely to have a major severity of revision score (53%) compared with patients who had revision TKAs (15%).
Resource utilization was greater for patients who had revision THAs than TKAs with respect to LOS and hospitalization costs. The mean LOS was longer for patients who had revision THA (mean ± SD, 5.8 days ± 14.0 days) than for patients who had TKA (mean ± SD, 4.8 days ± 10.5 days). The mean hospitalization costs were greater for revision THA (mean ± SD, USD 24,697 ± USD 40,489) than revision TKA (mean ± SD, USD 23,130 ± USD 36,643 (Table 6). Periprosthetic joint infection and periprosthetic fracture were associated with the greatest LOS and costs for revision THAs and TKAs.
Limitations exist with the use of administratively coded data. The value of administrative codes in determining how total joint arthroplasties fail, and the procedures used to revise failing implants, depend largely on the adoption of diagnosis and procedure codes, and their definitions and use. Accuracy of revision total joint arthroplasty procedure codes may depend on interpretation of clinical documentation by coding staff, and completeness of diagnosis descriptions may be surgeon-dependent. Confounding factors, when comparing revision THA with revision TKA, include changing design factors and particular implant failures (eg, early failure of certain designs like metal-on-metal implants for THA). Although administrative datasets and improved ICD-9-CM diagnosis and procedure coding are not a substitute for a formal national arthroplasty registry [34, 57], a large, nationally representative, and generalizable study population provides increased external validity, and administrative datasets are used by public reporting and governmental agencies. While the NIS contains hospital charge data (ie, how much the hospitals billed for particular services), the cost data in our study derived from the NIS does not reflect how much hospital services actually cost or the specific amounts that hospitals received in payment. In addition, as this study principally was descriptive, statistical analyses were not performed. However, owing to the large sample size in the NIS dataset, even small observed differences are likely to be highly statistically significant and unlikely to be a consequence of chance. Therefore, one should focus on the effect size in terms of absolute differences in the changes.
Our analysis of the demographic trends associated with revision TKAs and THAs showed important differences among patients who undergo the respective procedures.
Although a 23% increase in the number of hospitalizations was seen for patients having revision THAs from 2006 to 2010, a nearly 40% increase in the number of hospitalizations for patients having revision TKAs was observed. Revision TKAs are increasing at a faster rate than revision THAs, likely attributable in part to the higher underlying rates of primary TKA . This trend is mirrored in worldwide rates of revision TKAs  using international registry data .
The revision TKAs were mostly attributable to mechanical loosening and periprosthetic joint infection in younger patients (younger than 75 years), which may represent an emerging age shift, given that an increasing proportion of primary TKAs are being performed in younger patients [18, 58]. The similar patient age trends in revision THA also may represent an emerging age shift in the burden of revision, given that an increasing proportion of primary THAs are being performed in younger patients [11, 19, 23, 42, 44]. It is estimated that by 2030, patients younger than 65 years will comprise 52% of primary THAs being performed . Nevertheless, the largest difference across age subgroups for revision THA was for periprosthetic fracture, for which more than 30% of total revisions were in patients 75 to 84 years old. Future data will show if age-related trends prove to be important for revision THAs and TKAs.
When comparing the indications and types of procedures associated with revision TKA and revision THA, several differences were found. Our findings of indications for revision echo previous epidemiologic studies of revision total joint arthroplasties [7, 8]; however, our findings for revision THAs differ from prior observational cohort studies [3, 54] and international registry reports [33, 43] that identified aseptic loosening, bearing surface wear, and osteolysis as primary causes of TKA failure. Likewise, our revision TKA findings differ from those of prior reports implicating aseptic etiologies, including polyethylene wear, prosthetic loosening, and instability as the primary mechanisms for failed TKA [16, 36, 37, 41, 51, 52]. Other studies have reported that periprosthetic joint infection is a primary indication for revision TKA [14, 56]. Population and other regional differences might exist that may explain differing results in international registry data. Some of the variation in reasons reported for revision total joint arthroplasties may be based on differences in coding between administrative and clinical databases. For example, there are several categories of “mechanical problems” in ICD-9-CM coding that may be included under different titles (eg, aseptic loosening) in clinical databases.
The increasing trend for the use of the “mechanical loosening” code (ICD-9-CM 996.41) may be partly explained by a relative increase in mechanical loosening as a dominant mode of total joint replacement failure. The second most common reason for revision TKA, mechanical loosening (16.1%), may have been surpassed owing to the coalescing of other codes for mechanical complications. All-component revision ranks as the most common type of revision procedure and has remained fairly constant [7, 8]. With a periprosthetic joint infection, “arthrotomy or removal” accounted for more than 45% of procedures for revision THAs and TKAs, and all-component revision was the next most common reason.
Patient comorbidities and severity of illness proved to be important factors in treating patients who undergo revision arthroplasty. Analysis of severity of illness in our patient populations found differences with respect to revision THAs and TKAs. The revision THA diagnoses most often associated with a major severity of illness score were implant-related problems, followed by periprosthetic joint infection. For a periprosthetic joint infection, the minimum severity of illness score for patients was moderate (ie, no patients received a minor score), which points to the potential for comorbidities and poor overall health often associated with a periprosthetic joint infection. Revision TKAs for periprosthetic joint infections and fracture are the two diagnoses most frequently seen in patients in urban, nonteaching settings, and these diagnoses were most often associated with a major (and/or extreme) severity of illness score. Comorbidities have been reported to be associated with increased risk of periprosthetic joint infection in patients who have undergone TKA . The diagnoses most often associated with a moderate severity of illness score were periprosthetic osteolysis, then implant-related problems. The proportion of patients with older age (≥ 65 years) undergoing revision THA affects the underlying frequencies of population comorbidities. Revision THAs tend to be performed in sicker patients, and comorbidities particularly influence the rate of revision after primary THA , including the rate of early revision in the elderly . Risk-assessment tools may offer physicians the opportunity to counsel elderly patients regarding the specific risks of infection after THA . Bearing surface wear was the only diagnosis in which a moderate severity of illness score was more common than a major score; again, this may have been related to age or other patient-related factors that track with bearing surface failure mechanisms. It also may have been related to younger patients who had hip implants with conventional polyethylene during previous decades, who now more often are undergoing revision for bearing wear.
We noted important differences in resource utilization, including LOS and cost, between revision THAs and TKAs. The differences between LOS for revision THAs and TKAs may relate to severity of illness scoring and complexity of surgical procedures and rehabilitation issues. Periprosthetic joint infection and periprosthetic fracture were associated with the highest costs for revision THA and revision TKA. Hospitalization costs contribute to the overall economic burden of patients with an infected arthroplasty [24, 27]. Outcomes after revision TKAs for patients with periprosthetic joint infection are worse than for patients with aseptic knee revision [2, 15, 20, 50, 59].
The prevalence of revision THAs and TKAs is increasing. Our study highlights the comparative differences between revision THAs and TKAs. For both procedures, numerous epidemiologic changes, compared with prior reports [7, 8], have been identified, and variability continues to exist in patient characteristics, modes of failure, procedure types, and resource utilization across hospitals and different regions of the country. Identifying the mechanisms of failure in revision joint arthroplasties is critical to guiding efforts to improve clinical outcomes. Beyond clinical demands associated with revisions, the increasing economic burden of these procedures creates financial strains for surgeons, patients, and health systems [23, 47, 48]. These data may be important for healthcare systems to appropriately allocate resources in arthroplasty service lines: The revision burden for THA is greater than for TKA, but revision TKAs are increasing at a faster rate. Likewise, the treating clinician should understand that, while 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. The results of our study should inform avenues for research, clinical care, and cost measurements . Continued analyses will further characterize emerging trends in the provision of care to patients undergoing revision THAs and TKAs.
2. Bengtson S, Knutson K. The infected knee arthroplasty: a 6-year follow-up of 357 cases. Acta Orthop Scand.
3. Berry DJ, Harmsen WS, Cabanela ME, Morrey BF. Twenty-five-year survivorship of two thousand consecutive primary Charnley total hip replacements: factors affecting survivorship of acetabular and femoral components. J Bone Joint Surg Am.
4. Bourne RB, Maloney WJ, Wright JG. An AOA critical issue: the outcome of the outcomes movement. J Bone Joint Surg Am.
6. Bozic KJ, Katz P, Cisternas M, Ono L, Ries MD, Showstack J. Hospital resource utilization for primary and revision total hip arthroplasty. J Bone Joint Surg Am.
7. Bozic KJ, Kurtz SM, Lau E, Ong K, Chiu V, Vail TP, Rubash HE, Berry DJ. The epidemiology of revision total knee arthroplasty in the United States. Clin Orthop Relat Res.
8. Bozic KJ, Kurtz SM, Lau E, Ong K, Vail TP, Berry DJ. The epidemiology of revision total hip arthroplasty in the United States. J Bone Joint Surg Am.
9. Bozic KJ, Lau E, Ong K, Chan V, Kurtz S, Vail TP, Rubash HE, Berry DJ. Risk factors for early revision after primary total hip arthroplasty in Medicare patients. Clin Orthop Relat Res.
10. Bozic KJ, Ong K, Lau E, Berry DJ, Vail TP, Kurtz SM, Rubash HE. Estimating risk in Medicare patients with THA: an electronic risk calculator for periprosthetic joint infection and mortality. Clin Orthop Relat Res.
11. Corbett KL, Losina E, Nti AA, Prokopetz JJ, Katz JN. Population-based rates of revision of primary total hip arthroplasty: a systematic review. PLoS One.
12. Daigle ME, Weinstein AM, Katz JN, Losina E. The cost-effectiveness of total joint arthroplasty: a systematic review of published literature. Best Pract Res Clin Rheumatol.
13. Emmerson KP, Moran CG, Pinder IM. Survivorship analysis of the Kinematic Stabilizer total knee replacement: a 10- to 14-year follow-up. J Bone Joint Surg Br.
14. Fehring TK, Odum S, Griffin WL, Mason JB, Nadaud M. Early failures in total knee arthroplasty. Clin Orthop Relat Res.
15. Goldman RT, Scuderi GR, Insall JN. 2-stage reimplantation for infected total knee replacement. Clin Orthop Relat Res.
16. Gonzalez MH, Mekhail AO. The failed total knee arthroplasty: evaluation and etiology. J Am Acad Orthop Surg.
17. Huang CH, Liau JJ, Lung CY, Lan CT, Cheng CK. The incidence of revision of the metal component of total knee arthroplasties in different tibial-insert designs. Knee.
18. Jain NB, Higgins LD, Ozumba D, Guller U, Cronin M, Pietrobon R, Katz JN. Trends in epidemiology of knee arthroplasty in the United States, 1990-2000. Arthritis Rheum.
19. Katz JN, Wright EA, Wright J, Malchau H, Mahomed NN, Stedman M, Baron JA, Losina E. Twelve-year risk of revision after primary total hip replacement in the U.S. Medicare population. J Bone Joint Surg Am.
20. Kramhoft M, Bodtker S, Carlsen A. Outcome of infected total knee arthroplasty. J Arthroplasty.
21. Kurtz S, Mowat F, Ong K, Chan N, Lau E, Halpern M. Prevalence of primary and revision total hip and knee arthroplasty in the United States from 1990 through 2002. J Bone Joint Surg Am.
22. Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am.
23. Kurtz SM, Lau E, Ong K, Zhao K, Kelly M, Bozic KJ. Future young patient demand for primary and revision joint replacement: national projections from 2010 to 2030. Clin Orthop Relat Res.
24. Kurtz SM, Lau E, Watson H, Schmier JK, Parvizi J. Economic burden of periprosthetic joint infection in the United States. J Arthroplasty.
25. Kurtz SM, Ong KL, Lau E, Bozic KJ, Berry D, Parvizi J. Prosthetic joint infection risk after TKA in the Medicare population. Clin Orthop Relat Res.
26. Kurtz SM, Ong KL, Lau E, Widmer M, Maravic M, Gomez-Barrena E, de Pina Mde F, Manno V, Torre M, Walter WL, de Steiger R, Geesink RG, Peltola M, Roder C. International survey of primary and revision total knee replacement. Int Orthop.
27. Kurtz SM, Ong KL, Schmier J, Mowat F, Saleh K, Dybvik E, Karrholm J, Garellick G, Havelin LI, Furnes O, Malchau H, Lau E. Future clinical and economic impact of revision total hip and knee arthroplasty. J Bone Joint Surg Am.
2007;89:suppl 3144-151 10.2106/JBJS.G.00587.
28. Kurtz SM, Ong KL, Schmier J, Zhao K, Mowat F, Lau E. Primary and revision arthroplasty surgery caseloads in the United States from 1990 to 2004. J Arthroplasty.
29. Leskinen J, Eskelinen A, Huhtala H, Paavolainen P, Remes V. The incidence of knee arthroplasty for primary osteoarthritis grows rapidly among baby boomers: a population-based study in Finland. Arthritis Rheum.
30. Losina E, Thornhill TS, Rome BN, Wright J, Katz JN. The dramatic increase in total knee replacement utilization rates in the United States cannot be fully explained by growth in population size and the obesity epidemic. J Bone Joint Surg Am.
31. Losina E, Walensky RP, Kessler CL, Emrani PS, Reichmann WM, Wright EA, Holt HL, Solomon DH, Yelin E, Paltiel AD, Katz JN. Cost-effectiveness of total knee arthroplasty in the United States: patient risk and hospital volume. Arch Intern Med.
2009;169:1113-1121; discussion 1121-1122.
32. Lyman S, Marx RG, Bach PB. Cost-effectiveness analysis of an established, effective procedure. Arch Intern Med.
33. Malchau H, Herberts P, Eisler T, Garellick G, Soderman P. The Swedish Total Hip Replacement Register. J Bone Joint Surg Am.
34. Maloney WJ. National Joint Replacement Registries: has the time come? J Bone Joint Surg Am.
35. Maloney WJ. An American implant registry: a clinical use trip wire. Orthopedics.
36. Mikulak SA, Mahoney OM, dela Rosa MA, Schmalzried TP. Loosening and osteolysis with the press-fit condylar posterior-cruciate-substituting total knee replacement. J Bone Joint Surg Am.
37. Mulhall KJ, Ghomrawi HM, Scully S, Callaghan JJ, Saleh KJ. Current etiologies and modes of failure in total knee arthroplasty revision. Clin Orthop Relat Res.
38. Ong KL, Lau E, Suggs J, Kurtz SM, Manley MT. Risk of subsequent revision after primary and revision total joint arthroplasty. Clin Orthop Relat Res.
39. Ong KL, Mowat FS, Chan N, Lau E, Halpern MT, Kurtz SM. Economic burden of revision hip and knee arthroplasty in Medicare enrollees. Clin Orthop Relat Res.
40. Peltola M, Malmivaara A, Paavola M. Learning curve for new technology? a nationwide register-based study of 46,363 total knee arthroplasties. J Bone Joint Surg Am.
41. Peters PC Jr, Engh GA, Dwyer KA, Vinh TN. Osteolysis after total knee arthroplasty without cement. J Bone Joint Surg Am.
42. Prokopetz JJ, Losina E, Bliss RL, Wright J, Baron JA, Katz JN. Risk factors for revision of primary total hip arthroplasty: a systematic review. BMC Musculoskelet Disord.
43. Puolakka TJ, Pajamaki KJ, Halonen PJ, Pulkkinen PO, Paavolainen P, Nevalainen JK. The Finnish Arthroplasty Register: report of the hip register. Acta Orthop Scand.
44. Ravi B, Croxford R, Reichmann WM, Losina E, Katz JN, Hawker GA. The changing demographics of total joint arthroplasty recipients in the United States and Ontario from 2001 to 2007. Best Pract Res Clin Rheumatol.
45. Rorabeck CH, Murray P. Cost effectiveness of revision total knee replacement. Instr Course Lect.
46. Saleh KJ, Santos ER, Ghomrawi HM, Parvizi J, Mulhall KJ. Socioeconomic issues and demographics of total knee arthroplasty revision. Clin Orthop Relat Res.
47. Schairer WW, Sing DC, Vail TP, Bozic KJ. Causes and frequency of unplanned hospital readmission after total hip arthroplasty. Clin Orthop Relat Res.
48. Schairer WW, Vail TP, Bozic KJ. What are the rates and causes of hospital Rradmission after total knee arthroplasty? Clin Orthop Relat Res.
49. Schmalzried TP, Shepherd EF, Dorey FJ, Jackson WO, dela Rosa M, Fa'vae F, McKellop HA, McClung CD, Martell J, Moreland JR, Amstutz HC. The John Charnley Award: Wear is a function of use, not time. Clin Orthop Relat Res.
50. Segawa H, Tsukayama DT, Kyle RF, Becker DA, Gustilo RB. Infection after total knee arthroplasty: a retrospective study of the treatment of eighty-one infections. J Bone Joint Surg Am.
51. Sharkey PF, Hozack WJ, Rothman RH, Shastri S, Jacoby SM. Insall Award paper: Why are total knee arthroplasties failing today? Clin Orthop Relat Res.
52. Sheng P, Lehto M, Kataja M, Halonen P, Moilanen T, Pajamaki J. Patient outcome following revision total knee arthroplasty: a meta-analysis. Int Orthop.
53. Singh JA, Vessely MB, Harmsen WS, Schleck CD, Melton LJ 3rd, Kurland RL, Berry DJ. A population-based study of trends in the use of total hip and total knee arthroplasty, 1969-2008. Mayo Clin Proc.
54. Ulrich SD, Seyler TM, Bennett D, Delanois RE, Saleh KJ, Thongtrangan I, Kuskowski M, Cheng EY, Sharkey PF, Parvizi J, Stiehl JB, Mont MA. Total hip arthroplasties: what are the reasons for revision? Int Orthop.
55. Vasarhelyi EM, MacDonald SJ. The influence of obesity on total joint arthroplasty. J Bone Joint Surg Br.
56. Vessely MB, Whaley AL, Harmsen WS, Schleck CD, Berry DJ. The Chitranjan Ranawat Award: Long-term survivorship and failure modes of 1000 cemented condylar total knee arthroplasties. Clin Orthop Relat Res.
57. Knoch F, Malchau H. Why do we need a national joint replacement registry in the United States? Am J Orthop (Belle Mead NJ).
58. Weinstein AM, Rome BN, Reichmann WM, Collins JE, Burbine SA, Thornhill TS, Wright J, Katz JN, Losina E. Estimating the burden of total knee replacement in the United States. J Bone Joint Surg Am.
59. Wilde AH, Ruth JT. Two-stage reimplantation in infected total knee arthroplasty. Clin Orthop Relat Res.
60. Wright EA, Katz JN, Baron JA, Wright RJ, Malchau H, Mahomed N, Prokopetz JJ, Losina E. Risk factors for revision of primary total hip replacement: results from a national case-control study. Arthritis Care Res (Hoboken).