Knee Arthroplasty in the Young Patient Survival in a Community Registry

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1 CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Number 464, pp Lippincott Williams & Wilkins Knee Arthroplasty in the Young Patient Survival in a Community Registry Terence J. Gioe, MD *, ; Clifford Novak, MD ; Penny Sinner, MPH ; Wenjun Ma, MS, MD ; and Susan Mehle, BS Operative options for the younger patient with an arthritic knee remain controversial. We prospectively followed 1047 patients 55 years old or younger who underwent knee arthroplasty in a community joint registry over a 14-year period. Patients were implanted with 1047 joints of three predominant designs by 48 surgeons in four hospitals associated with a community joint registry. The mean age for this cohort was 49.8 years, and 62.8% (657/1047) of the patients were female. There were a total of 73 revisions performed, 5.6% (37/653) in women and 9.2% (36/394) in men. Cemented TKAs performed best, with a cumulative revision rate of 15.5%, compared to 32.3% in unicompartmental knee arthroplasty (UKA) patients and 34.1% in cementless designs. Men had a higher cumulative revision rate than women, 31.9% compared to 20.6%. Adjusting for implant type and gender, there was no difference in cumulative revision rate based on diagnosis (OA versus other) or age group ( 40, 41 45, 46 50, years) or between cruciateretaining and -substituting designs. Eighty five percent of cemented TKA implants survived at 14 years in the population under 55 years of age in this community registry. Cementless designs and UKA increased revision risk independently. Level of Evidence: Level II, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence. From * St Anthony Orthopaedic Specialists, St Paul, MN; University of Minnesota Medical School, Department of Orthopaedic Surgery, Minneapolis, MN; Research & Education, HealthEast Care System, St Paul, MN. Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. Each author certifies that his or her institution has approved the human protocol for this investigation and that all investigations were conducted in conformity with the ethical principles of research, and that informed consent was obtained. Correspondence to: Terence J. Gioe, MD, Dept. of Orthopaedic Surgery, University of Minnesota Medical School, Minneapolis VAMC, Section 112E, 1 Veterans Drive, Minneapolis, MN Phone: ; Fax: ; tjgioe@gmail.com. DOI: /BLO.0b013e31812f79a9 Arthritic disease in active, younger patients ( 55 years) is not uncommon and its prevalence is expected to increase. 1 A number of surgical options for the arthritic knee exist for these patients. Arthroscopic débridement, realignment osteotomy, and arthrodesis are all surgical options that have been proposed for this difficult problem. Many of these treatments, however, provide only short-term relief of symptoms or compromise function. 10,16 More recently, there has been a trend of offering knee arthroplasty as an option to provide pain relief and improve function in the active, younger patient with knee osteoarthritis. 10,11 Accelerated failure rates and the presumed difficulty in performing subsequent revision surgery remain the primary concerns of knee arthroplasty in this population. A number of studies suggest knee arthroplasty in younger patients is a reasonable option. 3 7,11,16,17,19,21,22 However, these studies have generally involved small numbers of patients, provided only short- to mid-term followup, and were performed by a limited number of surgeons at specialized total joint centers. Further, the study subjects often represent populations skewed toward those with a diagnosis of rheumatoid arthritis. The number of variables in such studies makes it difficult to draw conclusions. We prospectively followed knee arthroplasty patients 55 years old or younger in our community joint registry. We hypothesized cemented total knee arthroplasty (TKA) would demonstrate superior survival over other designs. We also considered whether preoperative diagnosis, age grouping, gender, cruciate ligament status, or index surgery year influenced survival of the knee arthroplasty in this group. MATERIALS AND METHODS The HealthEast Joint Registry (HEJR) provides information on survival of over 16,500 joint arthroplasties performed over a 14-year time period (September 1991 December 31, 2005). Details of the registry data collection methods and application of statistical analyses have been previously reported. 9 We prospec- 83

2 84 Gioe et al Clinical Orthopaedics and Related Research tively followed 1047 joint registry patients age 55 years and younger who underwent knee arthroplasty during this period. We used revision of the primary arthroplasty as the endpoint and defined revision as removal, exchange, or addition of any prosthetic component. The minimum followup of this group was zero months (mean, 55 months; range, months). Seventy-three patients had revisions, and 974 patients were censored; 15 patients died and 959 reached the end of the study. A joint registry, by definition, cannot account for every potential patient lost to followup, but prior work in our registry 9 has demonstrated a capture rate of 94%, similar to that of the Swedish Knee Arthroplasty Register (SKAR). 23 Preoperative diagnosis, age grouping, gender, component design, cruciate ligament status, and index surgery year were analyzed as possible factors that could influence survival. Over time the total percentage of young patients in the overall registry TKA population increased from 4.6% in 1991 to 17.1% in 2005 (Fig 1). The mean age of the patients in this study was 49.8 years (range, years). Fifty-five percent (572/1047) were age 51 to 55, 29% (302/1047) were age 46 to 50, 11% (116/1047) were age 41 to 45 and 5% (57/1047) were 40 years old or younger. The majority of patients were female (62.8%). Osteoarthritis was the underlying diagnosis prompting the original surgery in 93.3% of all cases. Preoperative activity level and body mass index were not captured in the registry. Most of our implants (85%) were of three manufacturers designs: DePuy/Johnson and Johnson (47%), Stryker/Osteonics (23.4%), and Wright Medical (14.1%). Six AAHKS or Knee Society members performed 48% of the surgeries (501/1047). Five of those surgeons performed 50 surgeries or more, 10 surgeons performed between 25 and 50 surgeries, and 33 surgeons performed 25 surgeries or less. Descriptive analysis was performed using the mean and standard deviation for continuous variables and frequencies for categorical variables. Cumulative survival rates and associated 95% confidence intervals were calculated using the Kaplan-Meier survival function. The log-rank test was used to compare differences in cumulative survival rates between groups. Cox proportional hazard regression was used to calculate the risk of revision. Gender, age grouping ( 40 versus versus versus 51 55), implant design (cemented tricompartmental TKA versus hybrid [cementless femur, cemented tibia] versus cementless tricompartmental TKA versus unicompartmental knee arthroplasty), cruciate ligament status (cruciate-retaining versus cruciate-substituting), index surgery year ( 1995 versus > 1995), and preoperative diagnosis (osteoarthritis versus rheumatoid arthritis versus others) were considered for their potential effect on cumulative survival rates and risk of revision in the study population. The above factors were included in the Cox proportional hazards regression model if they were significantly associated with the risk of revision (p < 0.05). All analyses were performed with SPSS version 14.0 (SPSS Inc, Chicago, IL). RESULTS Seventy-three cases from the study population were revised during the study period. The 14-year cumulative survival rate for all knee arthroplasty procedures was 74.5% (95% CI %) (Table 1). The cemented group had the highest (p 0.002) survival rate and the hybrid, UKA, and cementless groups all had lower survival rates (Fig 2). No factors considered (age, gender, cruciate ligament status, or index surgery year) influenced cumulative survival rate. Compared to patients with cemented implants, patients with cementless implants were 2.7 times as likely to be revised, patients with UKA implants were 2.9 times as likely to be revised, and patients with hybrid implants were 1.8 times as likely to be revised (Table 2). No factors considered (age, gender, cruciate ligament status, or index surgery year) influenced risk of revision. The most common reason for revision in this population was aseptic loosening (31.5%), followed by wear/osteolysis (19.2%), and progression of arthritis in unresurfaced compartments (13.7%, typically a UKA revision diagnosis). Fig 1. The percentage of patients undergoing knee arthroplasty in the HEJR who are 55 years old or less has increased over time.

3 Number 464 November 2007 Registry Survival of Young TKAs/UKAs 85 TABLE 1. Primary Knee Replacements and Revisions in Patients 55 Years Old Variable Total Primary Knees Total Revisions 14-Year CSR (95% CI) p Value Overall % ( %) Implant Design* Cemented % ( %) Cementless % ( %) UKA % ( %) Hybrid % ( %) *Five cases that were other implant types were excluded. UKA = unicompartmental knee arthroplasty; CSR = cumulative survival rate; CI = confidence interval Of the revised implants, 76.7% (56 of 73) had originally been sterilized by gamma-irradiation-in-air, 8.2% (6 of 73) by ethylene oxide, and the remaining 15.1% (11 of 73) by irradiation in an inert environment. Sterilization method and shelf storage life were not routinely recorded in the registry. In the case of the revised implants, sterilization method was determined retrospectively by the manufacturer based on catalog and lot number. Because this information was not available for all knee implants in the registry, variable regression analysis could not be performed based on sterilization method or shelf life. We observed no difference in the cumulative survival rate of implants performed by the surgeon specialists and the lower-volume surgeons in this study. DISCUSSION Despite the predictable results in an older population, the application of knee arthroplasty to a younger, more active population was initially discouraged out of concern for revisions due to wear or aseptic loosening. 12,20 Nevertheless, demand for knee arthroplasty in this younger age group continues to increase, driven by numerous factors. 15 The prudent surgeon individualizes the care of such patients, considering carefully the alternatives of continued nonoperative management, arthroscopic procedures, tibial or femoral osteotomy, UKA, or TKA. However, delaying knee arthroplasty indefinitely in the younger patient with marked pain and restricted function also appears to lead to worse outcomes. 13,14,18 Our study was designed to demonstrate the results that can be expected when knee arthroplasty is performed in a patient 55 years or younger in a community setting. We sought to determine the influence of preoperative diagnosis, age grouping, gender, component design, and cruciate ligament status on survival of the implant in this population. Limitations of the study include those inherent to any total joint registry study. Although we have taken steps to validate the registry data, and have a capture rate of 94%, 9 similar to that of the SKAR, we cannot rule out the possibility that some revisions were performed outside the registry capture area. Similarly, because registry studies only record revision information, we cannot comment on TABLE 2. Risk of Revision Using Hazard Ratios (HR) from Cox PH Regression Model Implant Design HR (95% CI) p Value Fig 2. Cemented TKAs have a significantly higher (p < 0.002) cumulative survival rate than the other three arthroplasty designs in the registry. Cementless versus cemented 2.67 ( ) 0.01 UKA versus cemented 2.90 ( ) Hybrid versus cemented 1.83 ( ) 0.05 UKA = unicompartmental knee arthroplasty; HR = hazard ratio; CI = confidence interval

4 86 Gioe et al Clinical Orthopaedics and Related Research radiographic performance, poor clinical results, or pending revisions in this population. All registries utilize the cumulative revision rate, which describes the risk of revision of a surviving implant at a given time, and accounts for deceased patients. This is a more useful measure than the crude revision rate (percentage of revisions to total number of primary TKAs performed), as the crude rate can be distorted by varying lengths of time to revision and increasing numbers of primary surgeries performed. Registries have the added benefits of pooling large numbers of procedures from surgeons with varying volumes but with more detail and accuracy than in population-based health services research. 2 However, a registry database cannot account for varying indications between surgeons or varying patient populations as is possible in a randomized clinical trial. The small numbers of revision operations performed in the RA population and in the cemented CS designs preclude definitive conclusions about these populations. Although most of the revised implants were gamma irradiated in air, lack of sterilization and shelf life data on the entire population also limited analysis in this area. As the registry expands both in time and population, the limitations imposed by smaller numbers and wider confidence intervals at the extremes of followup will be lessened. Many authors have reported their series of TKA in younger patients (Table 3). In general, the results have been quite acceptable at intermediate followup, with survival ranging from 87% to 96.5% at 8 to 20 years. Typically, the TKA components have been cemented, many tibial components have been nonmodular, and the results reflect the work of one surgeon or a small group of arthroplasty surgeons. In addition, many of the studies involve populations that are largely composed of patients with inflammatory arthropathies. The SKAR demonstrates age has a considerable effect on the rate of revision of TKA in osteoarthritis, but not in rheumatoid arthritis. 23 Our study suggests the outcomes that can be expected when TKA arthroplasty is undertaken in a younger population by the community orthopaedic surgeon. The primary diagnosis for this population was overwhelmingly osteoarthritis, reflecting both the nature of our community practice and presumably a somewhat more active population than that seen with a diagnosis of rheumatoid arthritis. Clearly, some elements of component design did play a role in implant survival in our registry. Cementless designs and UKA fared considerably worse than cemented tricompartmental designs when all other variables were excluded. However, because the majority of the TKAs in this age group in our population were of CR designs, we were unable to detect a difference in survival between CR and CS designs. Comparison with other registry results is enlightening. The percentage of patients receiving TKA in Sweden un- TABLE 3. Study/ Authors Selected Prior Published Studies of TKA in Young Patients Subjects Mean Age Mean F/U (yrs) Diagnosis Components Surgeons Revisions Survivorship Stern et al % OA All cemented; 9 MB N/A 5.9% N/A patellae Dalury et al % RA 29% JRA All cemented; CR; 80 MBT N/A 3.4% N/A vs. 7 APT Diduch et al % OA 5 MB patellae; 107 PS 2 N/A 87% at 18 years designs; 15 APT Gill et al % OA 29% RA All CR; 61 patellar 1 4.4% 96.5% at 18 years resurfacing Duffy et al % RA 24% OA All cemented; 21 CR and N/A N/A 95% at 15 years 53 TC; 43 APT and 31 MBT Lonner et al % OA Variety of implants; 27 N/A 12.5% 90.6% at 8 years cemented Sorrells et al % OA 21% LCS rotating 1 7% 88% at 14 years inflammatory platform (Depuy) Hoffmann et al % OA All cementless; 32 CS, % N/A CR Mont et al % OA All CR; 9 cemented, 8 2 3% N/A hybrid, 18 uncemented; 15 patella resurfaced Ranawat et al % OA All cemented; PS APT 2 1.8% N/A Crowder et al % RA All cemented; 23 MBT and 24 APT; 17 CR and 30 TC N/A 13% 93.7% at 20 years OA = osteoarthritis; RA = rheumatoid arthritis; CR = cruciate-retaining; CS = cruciate-substituting; TC = total condylar; MBT = metal-backed tibia; APT = all-polyethylene tibia; PS = posterior stabilized

5 Number 464 November 2007 Registry Survival of Young TKAs/UKAs 87 der the age of 55 is relatively small (well under 10% each year from 1990 through 2004). Although the SKAR has not specifically looked at the younger population, our results are consistent with their findings in the larger population. 23 The most common indication for revision of TKA in both registries is aseptic loosening. The UKA has a consistently higher cumulative revision rate than TKA, a finding that we have noted in our general population as well. 8 Cementless tibial components were also seen as an increased revision risk in both registries, although this difference is negligible at present in the SKAR because cementless tibial components are used only 2% of the time. Brand differences in cumulative revision rate for many of the most commonly used designs in Sweden are insignificant. The SKAR has been able to demonstrate a decreasing cumulative revision rate for TKA in OA over the years. We noted a similar but insignificant trend for knee arthroplasty performed in this younger population before 1995 versus after 1995 in the HEJR that we attributed to decreased use of cementless and UKA designs after However, as the SKAR report authors note, this difference may not be explained solely by an increase of operations in the elderly or by improved implants alone. 23 A combination of factors, including improvements in patient selection, implant design, and surgical technique remains the most likely explanation for this encouraging trend. We observed what we judge an acceptable survival in our registry of cemented TKA implants of various designs (cumulative revision rate of 16%) at 14 years in this difficult younger population. We believe that ongoing followup and analysis of registry results will enable surgeons to decrease the revision burden in the future. Acknowledgments The authors thank Kathleen Killeen for her ongoing efforts to make the HEJR a success, and the 48 surgeons of HealthEast that contributed to this study of the HEJR. References 1. Arthritis. Data and Statistics page. Centers for Disease Control Web site. Available at: national_data_nhis.htm#future. Accessed September 1, Coyte PC, Hawker G, Croxford R, Wright JG. Rates of revision knee replacement in Ontario, Canada. J Bone Joint Surg Am. 1999; 81: Crowder AR, Duffy GP, Trousdale RT. Long-term results of the total knee arthroplasty in young patients with rheumatoid arthritis. J Arthroplasty. 2005;20: Dalury DF, Ewald FC, Christie MJ, Scott RD. Total knee arthroplasty in a group of patients less than 45 years of age. J Arthroplasty. 1995;10: Diduch DR, Insall JN, Scott WN, Scuderi GR, Font-Rodriquez D. Total knee replacement in young, active patients: long-term followup and functional outcome. J Bone Joint Surg Am. 1997;79: Duffy GP, Trousdale RT, Stuart MJ. 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