Duration of the Increase in Early Postoperative Mortality After Elective Hip and Knee Replacement

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1 This is an enhance PDF from The Journal of Bone an Joint Surgery The PDF of the article you requeste follows this cover page. Duration of the Increase in Early Postoperative Mortality After Elective Hip an Knee Replacement Stein Atle Lie, Nicole Pratt, Philip Ryan, Lars B. Engesæter, Leif I. Havelin, Ove Furnes an Stephen Graves J Bone Joint Surg Am. 2010;92: oi: /jbjs.h This information is current as of January 6, 2010 Reprints an Permissions Publisher Information Click here to orer reprints or request permission to use material from this article, or locate the article citation on jbjs.org an click on the [Reprints an Permissions] link. The Journal of Bone an Joint Surgery 20 Pickering Street, Neeham, MA

2 58 COPYRIGHT Ó 2010 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED Duration of the Increase in Early Postoperative Mortality After Elective Hip an Knee Replacement By Stein Atle Lie, PhD, MSc, Nicole Pratt, BSc, Philip Ryan, MBBS, BSc, FAFPHM, Lars B. Engesæter, PhD, MD, Leif I. Havelin, PhD, MD, Ove Furnes, PhD, MD, an Stephen Graves, MBBS, FRACS, DPhil Investigation performe at The Norwegian Arthroplasty Register, Department of Orthopaeic Surgery, Haukelan University Hospital, Bergen, Norway Backgroun: There is increase early postoperative mortality after elective joint replacement surgery. However, the magnitue an uration of the increase mortality are uncertain. Methos: Data on total knee an total hip replacement from the comprehensive national registries in Australia an Norway were assesse. Only patients between fifty an eighty years of age with osteoarthritis were inclue. Overall, the stuy inclue 81,856 patients with a total knee replacement an 106,254 patients with a total hip replacement. Smoothe intensity curves were calculate to show the change in mortality for the early postoperative perio, whereas the effects of risk factors were stuie with use of the nonparametric aitive Aalen moel. Results: We foun that early postoperative mortality was increase for the first twenty-six postoperative ays (95% confience interval, twenty-two to forty-one ays). The excess mortality, compare with a baseline mortality (calculate as the average mortality from Day 100 to Day 200), for these twenty-six ays was estimate to be 0.12% (95% confience interval, 0.11% to 0.14%). The most important risk factors for excessive early postoperative mortality were male sex an high age (more than seventy years of age). Conclusions: There is an increase, but low, early postoperative mortality following lower extremity joint replacement surgery. The excess mortality persists, but steaily ecreases, for approximately the first twenty-six postoperative ays. Level of Evience: Prognostic Level II. See Instructions to Authors for a complete escription of levels of evience. Total hip an total knee replacements of egenerate joints are highly successful an cost-effective proceures 1. Nevertheless, the surgical operation itself poses a risk an may even result in eath of the patient 2-4. The crucial magnitue of early postoperative mortality is rarely reporte an varies greatly because of ifferences in patient characteristics 4. In aition, sample sizes are often too small to prouce accurate figures on mortality, an the baseline mortality of the patients at risk is rarely consiere. Previous stuies have shown that patients manage with total hip replacement have a higher long-term survival than the general population 5,6, which inicates a selection of healthy patients for hip replacement surgery. Using ata from Norway, we also previously showe that patients manage with total hip replacement ha an excess early postoperative mortality as compare with a baseline mortality (calculate as the average mortality between Day 100 an Day 200) 7. To obtain accurate information on the magnitue an uration of the excess early postoperative mortality after hip an knee replacement, a substantial number of patient recors is require. We therefore use information from two valiate an large national atabases on joint replacement patients from Australia an Norway The primary purposes of the present stuy were to quantify the magnitue an uration of increase mortality following total hip replacement an total knee replacement an to etermine if there were ifferences in the magnitue an uration of this mortality. We wishe to obtain information that might be valuable in the ecision-making process relate to averse events after lower extremity total joint replacement. Disclosure: In support of their research for or preparation of this work, one or more of the authors receive, in any one year, outsie funing or grants in excess of $10,000 from the Norwegian an Australian governments an the Australian Orthopaeic Association. Neither they nor a member of their immeiate families receive payments or other benefits or a commitment or agreement to provie such benefits from a commercial entity. A vieo supplement to this article will be available from the Vieo Journal of Orthopaeics. A vieo clip will be available at the JBJS web site, The Vieo Journal of Orthopaeics can be contacte at (805) , web site: J Bone Joint Surg Am. 2010;92:58-63 oi: /jbjs.h.01882

3 59 TABLE I Number of Operations, Age, an Female Sex Number of Operations Age* (yr) Percentage of Patients Who Were Female Australia Total knee replacement 68, ± % Total hip replacement 48, ± % Total 117, ± % Norway Total knee replacement 13, ± % Total hip replacement 57, ± % Total 70, ± % Overall total 188, ± % *The values are given as the age an the stanar eviation. Materials an Methos The present stuy is base on ata from the National Joint Replacement Registry of the Australian Orthopaeic Association an the Norwegian Arthroplasty Register. Both registries provie iniviual recors on all patients an receive recors on approximately 95% of all operations performe The Australian registry began collection of ata on both hip an knee replacements in 1999, an full national ata became available in The registry collects ata on both total joint an partial (hemi) joint replacements. The available Australian ata in the time span from 1999 through 2003 were inclue in the present stuy. The Norwegian registry began Fig. 1 Graphs illustrating early survival an mortality following total hip an knee replacement surgery. A: Total early postoperative patient survival, with 95% confience interval, after total hip an total knee replacement surgery. B: Observe aily mortality (thin ashe line) an smoothe aily mortality (bol soli line), with 95% confience intervals (thin soli lines) an baseline mortality (horizontal bol ashe line). Excess mortality is the area between the baseline mortality an the smoothe aily mortality.

4 60 TABLE II Observe Deaths, Mortality, Baseline Mortality, an Excess Mortality in Ten-Day Categories Postoperative Days Deaths Observe Mortality* (%) Baseline Mortality (%) Excess Mortality* (%) 0 to (0.082 to 0.110) (0.058 to 0.086) 11 to (0.049 to 0.085) (0.025 to 0.060) 21 to (0.016 to 0.055) ( to 0.031) First 30 ays (0.180 to 0.220) (0.110 to 0.150) *The 95% confience interval is given in parentheses. registration of total hip arthroplasties in 1987, an all other joint replacements have been registere since Only total joint replacements (total hip replacements an total knee replacements) were inclue in the present stuy. The Norwegian total hip replacement ata from 1987 through 2005 an total knee replacement ata from 1994 through 2005 were inclue in the present stuy. For the Australian registry, mortality information was obtaine by matching patient information obtaine at the time of surgery an the eath recors from the National Death Inex using a stanar probabilistic matching algorithm (National Death Inex, Australian Institute of Health an Welfare). Patient recors with no matching eath recors were exclue from the stuy after the matching. For the Norwegian Arthroplasty Register, ata from surgery an eath files (from Statistics Norway) were matche with use of the unique eleven-igit Norwegian personal ientification number. The observation time was consiere censore at December 31, 2003, for the Australian ata an at December 31, 2005, for the Norwegian ata. Iniviuals who emigrate from Norway (incluing eighty-one patients manage with total knee replacement an 182 patients manage with total hip replacement) were censore at the ate of emigration. To obtain a homogeneous ataset, we selecte only patients with osteoarthritis of the hip or knee who ha ha a primary total replacement between the ages of fifty an eighty years. We further categorize the age interval into three bans: fifty to sixty years, sixty-one to seventy years, an seventy-one to eighty years. We also performe subanalyses on patients who ha been manage operatively after 1999 to avoi possible confouning effects of the operation year. Statistical Methos Survival curves were calculate with use of the Kaplan-Meier metho, with log-transforme 95% confience intervals an a lower limit ajustment for the number of patients at risk. The early postoperative mortality rate was calculate by means of kernel smoothing (with a normally istribute kernel an seven ays banwith) of the observe aily mortality rates. The smoothe mortality curves are presente with point-wise 95% score confience intervals. The baseline mortality was calculate with use of the average mortality between Day 100 an Day 200. This perio was chosen because we expect that the postoperative mortality no longer persists an thereshoulbeaminorincreaseinmortalityuetoincreasing age within this narrow time interval. We calculate the observe mortality, baseline mortality, an excess mortality for ten-ay intervals for the first thirty ays. The excess mortality was calculate as the ifference between the observe an baseline mortality. The ay at which the smoothe aily mortality was normalize (reache the baseline) was calculate on the basis of the intersection of the smoothe curve an the baseline mortality with use of a three-ay kernel smoothing. The 95% confience interval for the ay on which the mortality was normalize was base on bootstrapping (with use of 1000 samples). To quantify the time-epenent ifferences in mortality for patients manage with total hip replacement an total knee replacement accoring to sex, age, an country, ajuste nonparametric excess hazars were calculate with use of the Aalen aitive regression moel 13. Source of Funing There was no external funing source for the present stuy. Funing from the Norwegian an Australian governments (an the Australian Orthopaeic Association) was use for expenses relate to the operation of the registries (salaries, office space, computers, an so on). Results There was a greater proportion of women in the Norwegian registry than in the Australian registry, both for total hip arthroplasty an total knee arthroplasty, an patients were an average of 1.5 years oler in the Norwegian registry (Table I) (p < for all comparisons). The long-term survival of the patients from the two countries an the two joints were almost the same, except for a longer follow-up time for the patients in the Norwegian registry. The ata on the two joints for the two countries were therefore merge to calculate the total survival rate. For this total survival rate, the early postoperative phase (up to the 120th postoperative ay) is shown in Figure 1, A. We observe that the slope of the earliest phase of the curve is steeper at the start, inicating an excess mortality (hazar). The smoothe aily mortality curve showe that the early postoperative mortality was highest immeiately after the operation, with slightly more than one eath per 10,000 patients per ay (Fig. 1, B). The mortality ecrease thereafter an was normalize (at the lowest level) on the twenty-sixth postoperative ay (95% bootstrap confience interval, twenty-secon

5 61 to forty-first ay). The excess mortality for the first twenty-six ays was calculate as 0.124% (95% confience interval, 0.105% to 0.143%) on the basis of Figure 1, B. The baseline mortality was calculate as 0.063%, giving an observe mortality of 0.187% (95% confience interval, 0.168% to 0.206%) for the first twenty-six postoperative ays. The accumulate mortalities for the ten-ay intervals showe that the excess mortality was highest for the first ten ays, low from Day 11 to Day 20, an almost negligible from Day 21 to Day 30 (Table II). This fining was also apparent when the ata were stratifie accoring to age category (Table III). When stratifie by country, the smoothe aily mortality curves showe that the level an uration of the excess mortality were similar for Australia an Norway. Figure 2 shows the cumulative excess mortality curves from the aitive Aalen moel for the inclue variables. The curves can be rea as the approximate number of excess eaths (per 10,000 patients) at the given number of ays. For example, compare with women, we saw that, at 100 ays, the total number of excess eaths for men per 10,000 patients was ten (Fig. 2, B). Thus, we woul expect approximately thirty eaths among each 10,000 women (base on the reference mortality, Fig. 2, A), whereas we woul expect forty eaths among each 10,000 men. There was significantly increase excess mortality for men as compare with women (Fig. 2, B) an for patients with an age of seventy-one to eighty years as compare with those with an age of fifty to sixty years (Fig. 2, F). There was no significant ifference in the excess mortality for total hip arthroplasty as compare with total knee arthroplasty (Fig. 2, C), for Norway as compare with Australia (Fig. 2, D), or for patients from sixty-one to seventy years of age compare with those from fifty to sixty years of age (Fig. 2, E). From the nonparametric estimates from the Aalen regression, we also foun that there was a tenency to an even further increase mortality for the earliest perio after the operation for men an for patients from seventy-one to eighty years of age (Fig. 2, B an F). Fig. 2 Graphs illustrating nonparametric (time-epenent) estimates, with 95% confience intervals, for the cumulative excess hazar from an Aalen moel; the horizontal ashe line at 0 represents no effect or ifference. A: Reference mortality for women, total knee replacement, Australia, an an age of fifty to sixty years. B: Excess mortality for men. C: Excess mortality for total hip replacement (THR). D: Excess mortality for Norway. E: Excess mortality for an age of sixty-one to seventy years. F: Excess mortality for an age of seventy-one to eighty years.

6 62 TABLE III Observe Deaths, Mortality, Baseline Mortality, an Excess Mortality in Ten-Day Categories an Three Age Categories Age Category Postoperative Category Deaths Observe Mortality* (%) Baseline Mortality (%) Excess Mortality* (%) 50 to 60 years 61 to 70 years 71 to 80 years 0 to 10 ays (0.015 to 0.058) (0.003 to 0.046) 11 to 20 ays (0.003 to 0.063) ( to 0.051) 21 to 30 ays (0.000 to 0.038) ( to 0.026) First 30 ays (0.045 to 0.110) (0.008 to 0.071) 0 to 10 ays (0.042 to 0.078) (0.028 to 0.064) 11 to 20 ays (0.023 to 0.071) (0.009 to 0.057) 21 to 30 ays (0.000 to 0.046) (20.02 to 0.032) First 30 ays (0.100 to 0.150) (0.059 to 0.110) 0 to 10 ays (0.120 to 0.160) (0.081 to 0.130) 11 to 20 ays (0.060 to 0.120) (0.025 to 0.086) 21 to 30 ays (0.021 to 0.090) ( to 0.055) First 30 ays (0.250 to 0.320) (0.150 to 0.220) *The 95% confience interval is given in parentheses. The subanalyses of ata from 1999 i not alter any of the results, except that the slightly, although not significantly, higher mortality for the Norwegian patients in the earliest postoperative phase (Fig. 2, D) isappeare. Discussion In this observational stuy involving 188,110 joint replacements, combining ata from two national joint replacement registries, we foun that there was an increase mortality following joint replacement surgery, which persiste for twenty-six ays postoperatively. This excess early postoperative mortality was similar for patients manage with total hip an total knee replacement an for Norway an Australia. However, the overall excess mortality for patients manage with total joint replacement was foun to be small (0.12% for the first twenty-six ays). Quantifying the operative risks an excess mortality is important for escribing the possible isavantages of total joint replacements an to target the nee for actions to prevent averse events Replacement of a egenerate hip or knee joint is a very successful proceure for relieving pain an restoring function. However, serious complications such as eath can occur 4,15,21. Still, we o not believe that mortality shoul be the sole measure after surgery 3. By combining ata from two national joint replacement registries, we were able to stuy the characteristics of postoperative mortality with use of a large ataset, to calculate mortality (intensity/hazar) curves, an to iscover how the mortality changes over time. Using results from stuies with preset cutoff points (such as thirty, thirty-five, sixty, or ninety ays) to establish how long an increase operative risk persists is common However, the results from such stuies merely show that for at least some part of the pre-chosen time point, there may be increase mortality. Therefore, to argue that the increase mortality persiste for as long as sixty or ninety ays, on the basis of accumulate figures, may be wrong 25. Stanar statistical tools (such as cross-tables, chi-square tests, logistic regression, or Cox regression) require a preset time point in orer to be use. The Aalen regression moel, applie in the present stuy, is not subject to this constraint. The Australian mortality ata were obtaine by matching registry ata with the National Death Inex, a atabase maintaine by the Australian Institute of Health an Welfare. A stanarize probabilistic matching routine was use to match patients in the registry with those registere in the National Death Inex on the basis of emographic variables such as name, sex, age, or aress. We consier it unlikely that early postoperative mortality has any relation to the probability of a match; therefore, bias ue to missing ata shoul be negligible. We have emonstrate that the excess mortality rate is very low (0.12%). Possible mechanisms leaing to excess eath from the relatively high occurrence of thromboembolic events may involve several known an unknown factors 26,27. The increase in early postoperative mortality was highest immeiately after the operation, an after twenty-one ays postoperatively the increase in the early postoperative mortality was negligible. Furthermore, we believe that patient age an sex (which are the most important risk factors) shoul be taken into account when the iniviual early postoperative mortality risk is consiere. n

7 63 Stein Atle Lie, PhD, MSc Lars B. Engesæter, PhD, MD Leif I. Havelin, PhD, MD Ove Furnes, PhD, MD Department of Orthopaeic Surgery, The Norwegian Arthroplasty Register, Haukelan University Hospital, N-5021 Bergen, Norway. aress for S.A. Lie: Nicole Pratt, BSc Philip Ryan, MBBS, BSc, FAFPHM Discipline of Public Health, Aelaie Health Technology Assessment, The University of Aelaie, SA 5005, Australia Stephen Graves, MBBS, FRACS, DPhil AOA National Joint Replacement Registry, Discipline of Public Health, School of Population Health an Clinical Practice, University of Aelaie, SA 5005, Australia References 1. Segal L, Day SE, Chapman AB, Osborne RH. Can we reuce isease buren from osteoarthritis? Me J Aust. 2004;180(5 Suppl):S Seagroatt V, Golacre M. Measures of early postoperative mortality: beyon hospital fatality rates. BMJ. 1994;309: Seagroatt V, Tan HS, Golacre M, Bulstroe C, Nugent I, Gill L. 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