Different incidences of knee arthroplasty in the Nordic countries

Full Te ms & Condi ions o access and use can be ound a h p://www. and online.com/ac ion/jou nalIn o ma ion?jou nalCode=io 20 Download by: [Tampe e Uni e si y] Da e: 12 Ap il 2017, A : 03:39 Ac a O hopaedica ISSN: 1745-3674 (P in ) 1745-3682 (Online) Jou nal homepage: h p://www. and online.com/loi/io 20 Di e en incidences o knee a h oplas y in he No dic coun ies Mika J NiemeläInen, Keijo T MäKelä, O o Robe sson, Anne e W-Dahl, O e Fu nes, Anne M Fens ad, Alma B Pede sen, Hen ik M Sch øde , Heini Huh ala & An i Eskelinen To ci e his a icle: Mika J NiemeläInen, Keijo T MäKelä, O o Robe sson, Anne e W-Dahl, O e Fu nes, Anne M Fens ad, Alma B Pede sen, Hen ik M Sch øde , Heini Huh ala & An i Eskelinen (2017) Di e en incidences o knee a h oplas y in he No dic coun ies, Ac a O hopaedica, 88:2, 173-178, DOI: 10.1080/17453674.2016.1275200 To link o his a icle: h p://dx.doi.o g/10.1080/17453674.2016.1275200 © 2017 The Au ho (s). Published by Taylo & F ancis on behal o he No dic O hopedic Fede a ion. Published online: 06 Jan 2017. Submi you a icle o his jou nal A icle iews: 284 View ela ed a icles View C ossma k da a Ac a O hopaedica 2017; 88 (2): 173–178 173 Di e en incidences o knee a h oplas y in he No dic coun ies A popula ion-based s udy om he No dic A h oplas y Regis e Associa ion Mika J NIEMELÄINEN 1, Keijo T MÄKELÄ 2, O o ROBERTSSON 3, Anne e W-DAHL 3, O e FURNES 4,5, Anne M FENSTAD 4, Alma B PEDERSEN 6, Hen ik M SCHRØDER 7, Heini HUHTALA 8, and An i ESKELINEN 1 1 Coxa Hospi al o Join Replacemen , Tampe e; 2 Depa men o O hopaedics and T auma ology, Tu ku Uni e si y Hospi al, Tu ku, Finland; 3 The Swedish Knee A h oplas y Regis e , Depa men o O hopedics, Skåne Uni e si y Hospi al, Lund, and Depa men o Clinical Sciences, O hopedics, Lund Uni e si y, Lund, Sweden; 4 The No wegian A h oplas y Regis e , Depa men o O hopaedic Su ge y, Haukeland Uni e si y Hospi al, Be gen; 5 Depa men o Clinical Medicine, Uni e si y o Be gen, Haukeland Uni e si y Hospi al, Be gen, No way; 6 Depa men o Clinical Epidemiology, Aa hus Uni e si y Hospi al, Aa hus, and he Danish Knee A h oplas y Regis y; 7 Depa men o O hopaedic Su ge y, Naes ed Hospi al, Denma k; 8 School o Heal h Sciences, Uni e si y o Tampe e, Tampe e, Finland. Co espondence: [email p o ec ed] Submi ed 2016-02-25. Accep ed 2016-11-07. © 2017 The Au ho (s). Published by Taylo & F ancis on behal o he No dic O hopedic Fede a ion. This is an Open Access a icle dis ibu ed unde he e ms o he C ea i e Commons A ibu ion-Non-Comme cial License (h ps://c ea i ecommons.o g/licenses/by-nc/3.0) DOI 10.1080/17453674.2016.1275200 Backg ound and pu pose — The annual numbe o o al knee a h oplas ies (TKAs) has inc eased wo ldwide in ecen yea s. To make p ojec ions ega ding u u e needs o p ima ies and e isions, addi ional knowledge is impo an . We analyzed and compa ed he incidences among 4 No dic coun ies Pa ien s and me hods — Using No dic A h oplas y Regis e Associa ion (NARA) da a om 4 coun ies, we analyzed di e - ences be ween age and sex g oups. We included pa ien s o e 30 yea s o age who we e ope a ed wi h TKA o unicompa men al knee a h oplas y (UKA) du ing he pe iod 1997–2012. The nega- i e binomial eg ession model was used o analyze changes in gene al ends and in sex and age g oups. Resul s — The a e age annual inc ease in he incidence o TKA was s a is ically signi i can in all coun ies. The incidence o TKA was highe in women han in men in all 4 coun ies. I was high- es in Finland in pa ien s aged 65 yea s o mo e. A he end o he s udy pe iod in 2012, Finland’s o al incidence was double ha o No way, 1.3 imes ha o Sweden and 1.4 imes ha o Den- ma k. The incidence was lowes in he younges age g oups (< 65 yea s) in all 4 coun ies. The p opo ional inc ease in incidence was highes in pa ien s who we e younge han 65 yea s. In e p e a ion — The incidence o knee a h oplas y s eadily inc eased in he 4 coun ies o e he s udy pe iod. The di e ences be ween he coun ies we e conside able, wi h he highes inci- dence in Finland. Pa ien s aged 65 yea s o mo e con ibu ed o mos o he o al incidence o knee a h oplas y. ■ To al knee a h oplas y (TKA) o se e e os eoa h i is (OA) has good long- e m ou comes, and gi es g ea e pain elie and be e unc ional imp o emen han non-su gical ea - men (Ca e al. 2012, Skou e al. 2015). Good long- e m implan su i o ship has esul ed in TKA also becoming a ea men o se e e knee OA in younge pa ien s, al hough ou comes and implan su i o ship ha e been epo ed o be wo se han in elde ly pa ien s (Lonne e al. 2000, Rand e al. 2003, P ice e al. 2010, Julin e al. 2010). Repo ed inc eases in he a e o TKA and es ima es o u u e demand p edic a subs an ial inc ease in he incidence o TKA in many coun ies (Jain e al. 2005, Ku z e al. 2007, Kim e al. 2008, Culli o d e al. 2010, W-Dahl e al. 2010a, Nemes e al. 2015). Bo h he b oadening o indica ions o younge pa ien s and he inc ease in o al incidence o TKA ha e aised conce ns o a possible inc ease in e ision bu den in he long e m (Ku z e al. 2007, Gioe e al. 2007). Di - e ences be ween geog aphic loca ions and age g oups ha e been no ed in he incidences o TKA (Ka z e al. 1996, Wells e al. 2002). The majo inc ease in he incidence o TKA has been ound in people bo n in he pe iod 1946–1964 ( he baby- boome gene a ion) (Leskinen e al. 2012). The aim o his s udy was o analyze ends in he incidence o TKA and unicompa men al knee a h oplas y (UKA) using No dic A h oplas y Regis e Associa ion (NARA) da a om be ween 1997 and 2012, o iden i y any changes o di e ences in (o be ween) age g oups, he sexes, and coun ies. 10097 Niemela inen D.indd 17310097 Niemela inen D.indd 173 3/16/2017 11:17:21 AM3/16/2017 11:17:21 AM 174 Ac a O hopaedica 2017; 88 (2): 173–178 Pa ien s and me hods The NARA compiles da a on 4 No dic coun ies ha ha e sim- ila o ganiza ion o heal hca e and compa able pa ien cha ac- e is ics (Table 1). The NARA has in o ma ion on he TKAs and UKAs pe o med in Denma k, No way, and Sweden om 1997 h ough 2012 and in Finland om 2000 h ough 2012. The knee a h oplas y egis ies o Sweden (SKAR) and Denma k (DKR) and he a h oplas y egis ies o No way (NAR) and Finland (FAR) pa icipa ed in he p esen s udy. All 4 egis ies ha e used indi idual-based egis a ion o ope a ions and pa ien s. A minimal NARA da ase was c e- a ed o con ain da a ha all 4 egis ies could deli e , bu o adminis a i e easons he Finnish A h oplas y Regis e has been able o p o ide Finnish da a acco ding o he NARA da a de i ni ions om he beginning o 2000. A pilo s udy ca ied ou om NARA da a did no include FAR da a and i did no ha e an age cu o (Robe sson e al. 2010). The NARA da a- base includes da a on he pa ien s ha enable TKA and UKA incidence analyses, i.e. pa ien -le el da a on bo h demog aph- ics and implan ypes. Selec ion and ans o ma ion o he espec i e da ase s and de-iden i i ca ion o he pa ien s, which included dele ion o he na ional ci il egis a ion numbe s, we e pe o med wi hin each na ional egis e . The anonymous da a we e hen me ged in o a common da abase. Because o he small numbe o pa ien s aged 30 yea s o less who we e ope a ed, in he p es- en s udy we only included pa ien s aged 30 yea s o mo e who had unde gone a TKA o UKA su gical p ocedu e due o p ima y os eoa h i is o he knee. The da a we e ea ed wi h ull con i den iali y, acco ding o he egula ions o he espec i e coun ies. This included es ic ed access o he common da abase, which was limi ed o he au ho s o he p esen pape . The quali y o da a in he No dic egis ies is high, and he egis ies ha e bo h na ional co e age and a high deg ee o comple eness (annual epo s 2015: Danish Knee A h oplas y Regis e , No wegian A h o- plas y Regis e , Swedish Knee A h oplas y Regis e , Finnish A h oplas y Regis e ) (A hu sson e al. 2005, Espehaug e al. 2006). o TKAs and UKAs in Denma k, No way, and Sweden om 1997 o 2012 and in Finland om 2000 o 2012. The inci- dence was calcula ed as incidence densi y, which is de i ned as he numbe o new cases in a popula ion du ing a gi en ime pe iod ela i e o he sum o he pe son- ime alues o he a - isk popula ion. Nega i e binomial eg ession was used o es ima e he incidence a e a ios (IRRs) and he 95% con- i dence in e als (CIs) o UKAs and TKAs o each coun y because o e idence o o e dispe sion o da a. IRR epo s he es ima ed a e age annual inc ease o incidence. Analyses we e s a i i ed by sex and age g oup. The s a is ical analyses we e conduc ed wi h SPSS 22.0 and S a a 8.2 so wa e. Resul s Pa ien cha ac e is ics 385,310 p ima y knee a h oplas ies we e egis e ed in he 4 coun ies du ing he s udy pe iod. Du ing his pe iod, we obse ed an inc ease in OA om 84% o 90% and simul ane- ously a decline in heuma oid a h i is om 10% o 4% as indica ion o knee a h oplas y. O hese ope a ions, 317,008 TKAs and 27,687 UKAs we e pe o med o knee OA in pa ien s aged 30 yea s o mo e. Female pa ien s ep esen ed 202,940 (64%) o he TKA cases and 15,778 (57%) o he UKA cases. The mean age o he pa ien s was 70 yea s (SD 9.0) in he TKA g oup and 65 yea s (SD 9.4) in he UKA g oup (Table 1). Incidence o knee a h oplas y (TKA and UKA) In all 4 coun ies, he incidences o knee a h oplas y inc eased du ing he s udy pe iod (Figu e 1). A he beginning o he s udy, he incidences we e 3.4 in Denma k, 3.6 in No way, 9.0 in Sweden, and 13 in Finland pe 10,000 popula ion. A he end o he s udy, he incidences we e 21 in Denma k, 14 in No way, 21 in Sweden, and 28 in Finland pe 10,000 popula- ion. The ela i e change in incidence o knee a h oplas y was 6.0- old in Denma k, 3.9- old in No way, 2.3- old in Sweden, and 2.1- old in Finland om he s a o he s udy o he end. Table 1. Pa ien cha ac e is ics. Mean age applies o bo h TKA and UKA. The numbe o ope a ions has been di ided in o age g oups. S udy pe iod 1997–2012, excep o Finland (2000–2012) Denma k No way Sweden Finland To al Mean age (SD) 69.0 (9.5) 69.7 (9.2) 69.8 (9.0) 69.0 (9.0) Females, % 63 66 60 68 UKA (n) 5,395 5,054 12,956 4,282 Age g oups, n (%) 30–64 21,624 (33) 12,872 (31) 42,084 (30) 30,264 (31) 106,844 65–74 24,577 (38) 15,751 (37) 53,492 (39) 38,305 (39) 132,125 75+ 18,587 (29) 13,412 (32) 43,403 (31) 30,324 (31) 105,726 To al 64,788 42,035 138,979 98,893 344,695 E hics E hical app o al o he s udy was ob ained h ough he e hical app o al p ocess o each na ional egis y. S a is ics We desc ibed pa ien cha ac e is ics, ca - ego ized in o sex and age g oups, using desc ip i e s a is ics p esen ed as mean and s anda d de ia ion (SD). Incidences a e p esen ed as he numbe o ope a- ions pe o med pe 104 o popula ion. Age was ca ego ized in o 3 g oups: < 65 yea s, 65–74 yea s and ≥ 75 yea s. We analyzed ends in he gene al incidence 10097 Niemela inen D.indd 17410097 Niemela inen D.indd 174 3/16/2017 11:17:21 AM3/16/2017 11:17:21 AM Ac a O hopaedica 2017; 88 (2): 173–178 175 The ela i e change in incidence o UKA was 10- old in Denma k, 1.5- old in Finland, 7.1- old in No way, and 0.5- old in Sweden om he s a o he s udy o he end. Du ing he s udy pe iod, he es ima ed a e age annual inc ease in he incidence o TKA by age g oups and sex was s a is ically signi i can in all coun ies, wi h he excep ion o Finnish emales aged 65–74 yea s (IRR = 1.02, 95% CI: 1.00–1.03) (Table 2). IRR was highes in he younges age g oup in bo h sexes and a dec easing end was de ec ed as age inc eased. Females had lowe IRRs, excep in Denma k in pa ien s aged 65–74 yea s. A s a is ically signi i can dec ease in UKAs was de ec ed in Sweden in pa ien s who we e 65 yea s o mo e, whe eas in Denma k and in No way he e was a signi i can ly highe annual incidence o UKA in all age g oups—excep o UKAs in women aged 75 yea s o mo e in No way. The e was no signi i can change in he annual inci- dence o UKA o e he s udy pe iod in Finland, in men o women o any age g oup (Table 2). Incidence by sex The incidences o TKA acco ding o sex a e shown in Fig- u es 2 and 3. The incidence was highe in women han in men in all 4 coun ies. A he end o he s udy pe iod, he inci- dences o TKA we e 9.1 in Denma k, 11.0 in No way, 18.2 in Sweden, and 20.9 in Finland pe 10,000 men—gi ing a ela i e change o 4.2- old in Denma k, 5.9- old in No way, 2.8- old in Sweden, and 2.7- old in Finland om he s a o he s udy o he end. In women, he incidences o TKA we e 22.6 in Denma k, 15.7 in No way, 22.5 in Sweden, and 32.8 in Finland pe 10,000 women a he end o he s udy, and he ela i e change was 5.2- old in Denma k, 3.1- old in No way, 2.4- old in Sweden, and 1.9- old in Finland om he s a o he s udy o he end. The incidence o UKA was highe in Sweden in bo h men and women a he s a o he s udy han a he end o he s udy, whe eas in he o he 3 coun ies he incidence o UKA was highe a he end o he s udy han a he s a o he s udy (Figu es 4 and 5). 20122010200820062004200220001998 Denma k No way Sweden Finland 40 35 30 25 20 15 10 5 0 Incidence o TKA + UKA pe 10,000 inhabi an s Yea o ope a ion 20122010200820062004200220001998 Denma k No way Sweden Finland 40 35 30 25 20 15 10 5 0 Incidence o TKA in men pe 10,000 inhabi an s Yea o ope a ion 20122010200820062004200220001998 Denma k No way Sweden Finland 40 35 30 25 20 15 10 5 0 Incidence o TKA in women pe 10,000 inhabi an s Yea o ope a ion Figu e 1. To al incidence o TKA and UKA by yea o ope a ion in pa ien s aged 30 yea s o mo e. Incidences a e shown pe 10,000 inhab- i an s. The incidence in Denma k is es ima ed o include 10–15% unde es ima ion be ween 1997 and 2007 due o lowe comple eness. Figu e 2. Incidence o TKA in males aged 30 yea s o mo e. Incidences a e shown pe 10,000 inhabi an s. Figu e 3. Incidence o TKA in emales aged 30 yea s o mo e. Incidences a e shown pe 10,000 inhabi an s. Table 2. Nega i e binomial eg ession analysis. Incidence a e a ios (IRRs) wi h 95% con i dence in e als A h oplas y Male Female Age, yea s IRR 95% CI IRR 95% CI Denma k TKA 30–64 1.17 1.14–1.19 1.15 1.13–1.17 UKA 30–64 1.26 1.20–1.32 1.24 1.17–1.30 TKA 65–74 1.08 1.04–1.13 1.12 1.10–1.13 UKA 65–74 1.25 1.18–1.31 1.20 1.16–1.24 TKA 75+ 1.12 1.10–1.13 1.10 1.08–1.12 UKA 75+ 1.20 1.14–1.26 1.14 1.11–1.17 No way TKA 30–64 1.16 1.14–1.18 1.13 1.12–1.15 UKA 30–64 1.13 1.07–1.19 1.11 1.05–1.18 TKA 65–74 1.11 1.10–1.13 1.08 1.07–1.09 UKA 65–74 1.12 1.08–1.16 1.07 1.01–1.13 TKA 75+ 1.09 1.08–1.10 1.06 1.04–1.07 UKA 75+ 1.09 1.05–1.14 1.02 0.96–1.06 Sweden TKA 30–64 1.15 1.13–1.16 1.13 1.11–1.14 UKA 30–64 1.02 0.99–1.05 1.00 0.98–1.02 TKA 65–74 1.07 1.06–1.09 1.05 1.04–1.07 UKA 65–74 0.93 0.92–0.94 0.91 0.90–0.92 TKA 75+ 1.07 1.06–1.08 1.05 1.04–1.05 UKA 75+ 0.90 0.89–0.91 0.88 0.87–0.89 Finland TKA 30–64 1.13 1.11–1.16 1.11 1.09–1.14 UKA 30–64 10.5 0.99–1.11 1.02 0.95–1.09 TKA 65–74 1.04 1.02–1.06 1.02 1.00–1.04 UKA 65–74 0.99 0.91–1.06 0.96 0.92–1.00 TKA 75+ 1.04 1.03–1.06 1.03 1.01–1.05 UKA 75+ 0.99 0.92–1.06 0.95 0.90–1.00 10097 Niemela inen D.indd 17510097 Niemela inen D.indd 175 3/16/2017 11:17:21 AM3/16/2017 11:17:21 AM 176 Ac a O hopaedica 2017; 88 (2): 173–178 Incidence by age g oup The incidence o TKA was highes in Finland in pa ien s aged 65 yea s o mo e. The o al incidence was lowes in he young- es age g oup in all coun ies. The incidence was highe a he s a o he s udy han a he end in all age g oups (Figu e 6). Discussion We ound ha he o al incidence, comp ising bo h TKAs and UKAs, inc eased in all coun ies and he ends o inc ease we e compa able be ween coun ies. The inc ease in su gical p ocedu es in Finland om 2004 o 2006 may be explained by he coming in o o ce o a new social and heal hca e egula ion ha ins uc ed hospi als o sho en pa ien wai ing imes o su ge y. Despi e ha ing compa able socioeconomic si ua ions and heal hca e sys ems, di e ences in he incidence o knee a h oplas y be ween coun ies we e no able. A pilo s udy om he NARA da a es ed a common da ase and epo ed esul s om he pe iod 1997–2007 (Robe sson e al. 2010). The p esen s udy con inued o analyze changes in he inci- dence o a h oplas y un il 2012, based on expe ience gained om he pilo s udy. The o al inc ease in he numbe o a h oplas ies in all coun ies was mainly caused by an inc eased incidence o TKA. In Sweden, he e was a signi i can dec ease in he inci- dence o UKA in pa ien s aged 65 yea s o mo e. In 3 o he coun ies, a ia ions in incidences o UKA be ween g oups we e mo e he e ogeneous (Table 2, Figu es 4 and 5). The ea- sons o he changes in incidence o UKA a e mul i ac o ial. P e ious s udies om na ional egis ies ha e a ec ed UKA incidences, as mos egis ies show highe o e all e ision a es o UKAs han o TKAs (Fu nes e al. 2007, Koskinen e al. 2008, W-Dahl e al. 2010b). Howe e , he e ha e also been s udies claiming be e clinical ou come om UKA and also mo e cos -e ec i eness (Slo e e al. 2006, Lyg e e al. 2010). Di e en UKA implan models wi h a longe lea ning cu e compa ed o TKA, indica ions o p ima y UKA su ge y, and a highe e ision isk han wi h TKA may explain he di e - ences in he incidence compa ed o TKA. The inc ease in he incidence o UKA in pa ien s less han 65 yea s o age may be explained by he inc ease in minimally in asi e su ge y (MIS), which enables a sho e pos ope a i e s ay in hospi al. The 4 coun ies had compa able popula ions wi h ega d o age and sex, and he e o e ins ead o age-s anda dized da a we analyzed incidence be ween age g oups. O he 3 age g oups, pa ien s less han 65 yea s o age had he lowes incidence o TKA. Howe e , he ela i e inc ease in incidence was highe in ha age g oup han in he o he age g oups. In ecen yea s, i appea s ha he indica ions ha e widened o include younge pa ien s, which has esul ed in a p opo ionally highe inc ease in incidence in pa ien s less han 65 yea s o age, compa ed o pa ien s aged 65 yea s o less (Robe sson e al. 2010, Leski- nen e al. 2012). Be o e his, knee a h oplas y su ge y was ini ially ese ed o elde ly pa ien s and hose wi h se e e disease (Robe sson e al. 2014), and younge pa ien s wi h heuma oid a h i is. The easons o inc easing incidence in younge TKA pa ien s may be mul i ac o ial. Inc easing obesi y in young people (Kau iainen 2005, Lohmande e al. 2009), pa icipa ion in con ac spo s (D iban e al. 2015), and he in oduc ion o as - ack su ge y (which sui s younge pa ien s well) a e p obable easons. The p esen s udy had some s eng hs and limi a ions. The majo s eng h was he unique collabo a ion o 4 na ional eg- is ies in he c ea ion o a mul ina ional da abase co e ing a la ge numbe o pa ien s, which enabled in e na ional com- pa isons o e eal possible di e ences and which migh help o es ima e u u e demands. Fu he mo e, he comple eness 20122010200820062004200220001998 Denma k No way Sweden Finland 4 3 2 1 0 Incidence o UKA in men pe 10,000 inhabi an s Yea o ope a ion 20122010200820062004200220001998 80 60 40 20 70 50 30 10 0 Incidence o TKA by age pe 10,000 inhabi an s Yea o ope a ion Denma k No way Sweden Finland Age 30–64 Age 65–74 Age 75– Figu e 4. Incidence o UKA in males aged 30 yea s o mo e. Incidences a e shown pe 10,000 inhabi an s. Figu e 5. Incidence o UKA in emales aged 30 yea s o mo e. Incidences a e shown pe 10,000 inhabi an s. Figu e 6. Incidence o TKA acco ding o age g oup. Incidences a e shown pe 10,000 inhabi an s. 20122010200820062004200220001998 Denma k No way Sweden Finland 4 3 2 1 0 Incidence o UKA in women pe 10,000 inhabi an s Yea o ope a ion 10097 Niemela inen D.indd 17610097 Niemela inen D.indd 176 3/16/2017 11:17:25 AM3/16/2017 11:17:25 AM Ac a O hopaedica 2017; 88 (2): 173–178 177 and alidi y o da a we e high in he No dic coun ies a he end o he s udy pe iod (comple eness, NAR: 95%; SKAR: 97%; DKR: 97%; FAR: 96%) (annual epo s 2015: Danish Knee A h oplas y Regis e , No wegian A h oplas y Regis- e , Swedish Knee A h oplas y Regis e , Finnish A h oplas y Regis e ). Comple eness in he DKR was epo ed o be 89% in 2007 (Robe sson e al. 2010), which may ha e caused 10–15% unde es ima ion o incidence in Denma k o e he pe iod 1997–2007. To al ela i e change in incidence was highes in Denma k, and ha may ha e been due o he in l u- ence o a lowe comple eness o he DKR in he ea ly yea s o he s udy pe iod (Table 3). The lack o da a on BMI and o he subg oups could also be conside ed a limi a ion o he p esen s udy. The incidence o TKA s eadily inc eased in all pa icipa - ing coun ies in his s udy, which is in line wi h i ndings om o he s udies (Ku z e al. 2007, W-Dahl e al. 2010a, Leskinen e al. 2012). The incidence o knee a h oplas y in emales was ound o be g ea e han ha in males in ou s udy, bu he esul s o p e ious s udies ha e also shown ha he p opo - ion o emale pa ien s has dec eased wi h ime (Nemes e al. 2015). Mo eo e , he sex dis ibu ion may also a y be ween na ions (Pax on e al. 2011, Nemes e al. 2015). One s udy deli e ed p ojec ions o p ima y and e ision hip and knee a h oplas y in he Uni ed S a es om 2005 o 2030 (Ku z e al. 2007). In ha s udy, he au ho s p edic ed ha i he numbe o o al knee a h oplas ies pe o med con inues a he cu en a e, he demand o p ima y TKA would be p ojec ed o g ow by a ac o o 7 by 2030. In ano he p e ious s udy om he Finnish A h oplas y Regis y, he annual cumula i e incidence o UKA and TKA inc eased apidly be ween 1980 and 2006, especially in pa ien s aged 50–59 yea s, he so- called baby-boome gene a ion (Leskinen e al. 2012). In ou s udy, he inc ease in incidence was mainly due o he inc ease in incidence o TKAs. This i nding is consis en wi h a s udy by W-Dahl e al. (2010a) om he Swedish Knee A h oplas y Regis e , which showed ha al hough he incidence o TKA has inc eased in pa ien s unde 55 yea s o age, he incidence o UKA and high ibial os eo omy (HTO) has dec eased. Obe- si y is also a g owing bu den in many coun ies and, as his has been shown o be a ce ain isk ac o o knee os eoa h i is, especially in young pa ien s, i may con ibu e o he inc eas- ing demand o TKAs in u u e (Apold e al. 2014a, b, Sil e - wood e al. 2015). A p e ious s udy has aised conce ns abou he long- e m ou come o TKAs and he possibili y o an inc easing e ision bu den, because younge age has been associa ed wi h a highe isk o ea ly pe ip os he ic join in ec ion and asep ic mechan- ical ailu e a e TKA (Meehan e al. 2014). In ano he s udy, young age was ound o impai he p ognosis o TKA and was associa ed wi h inc eased e ision a es o non-in ec ious ea- sons (Julin e al. 2010). A compa ison s udy unde aken by he No wegian Knee A h oplas y Regis e and a Uni ed S a es a h oplas y egis y showed an inc eased isk o e ision in pa ien s less han 65 yea s o age compa ed o pa ien s aged 65 yea s o olde (Pax on e al. 2011). In ou s udy, he p o- po ional g ow h o TKAs du ing he s udy pe iod was highes in pa ien s who we e younge han 65 yea s. Despi e his, he incidence o knee a h oplas y in he younges age g oup was lowe han in pa ien s aged 65 yea s o mo e. Based on his i nding, he majo i y o knee a h oplas ies will p obably be pe o med on elde ly pa ien s in he u u e also. E en hough pa ien s less han 65 yea s old ep esen ed a lowe incidence le el han pa ien s who we e 65 o olde in ou s udy, hese wo king-age pa ien s should be conside ed o be an impo an subg oup because o hei highe physical ac i i y and highe demands o su ge y, and he mul i ac o ial easons behind he success o TKA (Keeney e al. 2014, Kli e al. 2014, Pa izi e al. 2014). An e ec on he e ision bu den can he e o e be an icipa ed in u u e. In summa y, he incidence o knee a h oplas y has s eadily inc eased in he 4 No dic coun ies. This inc ease was caused by an inc ease in he incidence o TKA, whe eas he incidence o UKA a ied be ween coun ies. The p opo ional inc ease in incidence was highes in pa ien s aged less han 65 yea s. Howe e , pa ien s who a e 65 yea s o mo e s ill comp ise he majo i y o hose who unde go knee a h oplas y, and hey a e he main con ibu o y ac o o he inc ease in he o al numbe o TKA ope a ions. S udy design: MN and AE. Analysis o da a and s a is ics: HH and MN. Re iew and in e p e a ion o he esul s: MN, HH, and AE. Re ision and app o al o he i nal manusc ip : MN, KM, OR, AW-D, OF, AF, AP, HS, and AE. This s udy was unded by a No dFo sk g an . No compe ing in e es decla ed. Apold H, Meye H E, No dsle en L, Fu nes O, Bas e V, Flugs ud G B. Risk ac o s o knee eplacemen due o p ima y os eoa h i is, a popula ion based, p ospec i e coho s udy o 315,495 indi iduals. BMC Musculoske- le Diso d 2014a; 15: 217. Apold H, Meye H E, No dsle en L, Fu nes O, Bas e V, Flugs ud G B. Weigh gain and he isk o knee eplacemen due o p ima y os eoa h i is: A pop- ula ion based, p ospec i e coho s udy o 225,908 indi iduals. Os eoa - h i is Ca ilage 2014b; 22 (5): 652-8. A hu sson A J, Fu nes O, Espehaug B, Ha elin L I, So eide J A. Valida ion o da a in he no wegian a h oplas y egis e and he no wegian pa ien egis e : 5,134 p ima y o al hip a h oplas ies and e isions ope a ed a a single hospi al be ween 1987 and 2003. Ac a O hop 2005; 76 (6): 823-8. Ca A J, Robe sson O, G a es S, P ice A J, A den N K, Judge A, Bea d D J. Knee eplacemen . Lance 2012; 379 (9823): 1331-40. Culli o d D J, Maskell J, Bea d D J, Mu ay D W, P ice A J, A den N K. Tempo al ends in hip and knee eplacemen in he uni ed kingdom: 1991 o 2006. J Bone Join Su g B 2010; 92 (1): 130-5. D iban J B, Hoo man J M, Si le M R, Ha is K, Ca ano N M. Is pa icipa ion in ce ain spo s associa ed wi h knee os eoa h i is? A sys ema ic e iew. J A hl T ain 2015; [Epub ahead o p in ]. 10097 Niemela inen D.indd 17710097 Niemela inen D.indd 177 3/16/2017 11:17:28 AM3/16/2017 11:17:28 AM 178 Ac a O hopaedica 2017; 88 (2): 173–178 Espehaug B, Fu nes O, Ha elin L I, Engesae e L B, Vollse S E, Kindse h O. Regis a ion comple eness in he no wegian a h oplas y egis e . Ac a O hop 2006; 77 (1): 49-56. Fu nes O, Espehaug B, Lie S A, Vollse S E, Engesae e L B, Ha elin L I. Failu e mechanisms a e unicompa men al and icompa men al p ima y knee eplacemen wi h cemen . J Bone Join Su g Am 2007; 89 (3): 519-25. Gioe T J, No ak C, Sinne P, Ma W, Mehle S. Knee a h oplas y in he young pa ien : Su i al in a communi y egis y. Clin O hop Rela Res 2007; 464: 83-7. Jain N B, Higgins L D, Ozumba D, Gulle U, C onin M, Pie obon R, Ka z J N. T ends in epidemiology o knee a h oplas y in he Uni ed S a es, 1990- 2000. A h i is Rheum 2005; 52 (12): 3928-33. Julin J, Jamsen E, Puolakka T, Kon inen Y T, Moilanen T. Younge age inc eases he isk o ea ly p os hesis ailu e ollowing p ima y o al knee eplacemen o os eoa h i is. A ollow-up s udy o 32,019 o al knee eplacemen s in he Finnish A h oplas y Regis e . Ac a O hop 2010; 81 (4): 413-9. Ka z B P, F eund D A, Heck D A, Di us R S, Paul J E, W igh J, Coy e P, Holleman E, Hawke G. Demog aphic a ia ion in he a e o knee eplace- men : A mul i-yea analysis. Heal h Se Res 1996; 31 (2): 125-40. Kau iainen S. T ends in adolescen o e weigh and obesi y in he No dic coun ies. Scandina ian Jou nal o Nu i ion 2005; 49 (1): 4-14. Keeney J A, Nunley R M, W igh R W, Ba ack R L, Clohisy J C. A e younge pa ien s unde going TKAs app op ia ely cha ac e ized as ac i e? Clin O hop Rela Res 2014; 472 (4): 1210-6. Kim H A, Kim S, Seo Y I, Choi H J, Seong S C, Song Y W, Hun e D, Zhang Y. The epidemiology o o al knee eplacemen in sou h ko ea: Na ional egis y da a. Rheuma ology (Ox o d) 2008; 47 (1): 88-91. Kli J, Jacobsen S, Rosenlund S, Sonne-Holm S, T oelsen A. To al knee a h oplas y in younge pa ien s e alua ed by al e na i e ou come mea- su es. J A h oplas y 2014; 29 (5): 912-7. Koskinen E, Eskelinen A, Paa olainen P, Pulkkinen P, Remes V. Compa ison o su i al and cos -e ec i eness be ween unicondyla a h oplas y and o al knee a h oplas y in pa ien s wi h p ima y os eoa h i is: A ollow-up s udy o 50,493 knee eplacemen s om he Finnish A h oplas y Regis e . Ac a O hop 2008; 79 (4): 499-507. Ku z S, Ong K, Lau E, Mowa F, Halpe n M. P ojec ions o p ima y and e ision hip and knee a h oplas y in he uni ed s a es om 2005 o 2030. J Bone Join Su g Am 2007; 89 (4): 780-5. Leskinen J, Eskelinen A, Huh ala H, Paa olainen P, Remes V. The incidence o knee a h oplas y o p ima y os eoa h i is g ows apidly among baby boome s: A popula ion-based s udy in Finland. A h i is Rheum 2012; 64 (2): 423-8. Lohmande L S, Ge ha dsson de Ve die M, Rollo J, Nilsson P M, Engs om G. Incidence o se e e knee and hip os eoa h i is in ela ion o di e en measu es o body mass: A popula ion-based p ospec i e coho s udy. Ann Rheum Dis 2009; 68 (4): 490-6. Lonne J H, He shman S, Mon M, Lo ke P A. To al knee a h oplas y in pa ien s 40 yea s o age and younge wi h os eoa h i is. Clin O hop Rela Res 2000; (380) (380): 85-90. Lyg e S H, Espehaug B, Ha elin L I, Fu nes O, Vollse S E. Pain and unc ion in pa ien s a e p ima y unicompa men al and o al knee a h oplas y. J Bone Join Su g Am 2010; 92 (18): 2890-7. Meehan J P, Danielsen B, Kim S H, Jamali A A, Whi e R H. Younge age is associa ed wi h a highe isk o ea ly pe ip os he ic join in ec ion and asep ic mechanical ailu e a e o al knee a h oplas y. J Bone Join Su g Am 2014; 96 (7): 529-35. Nemes S, Rol son O, W-Dahl A, Ga ellick G, Sundbe g M, Ka holm J, Robe sson O. His o ical iew and u u e demand o knee a h oplas y in Sweden. Ac a O hop 2015; 86 (4): 426-31. Pa izi J, Nunley R M, Be end K R, Lomba di A V,J , Ruh E L, Clohisy J C, Hamil on W G, Della Valle C J, Ba ack R L. High le el o esidual symp- oms in young pa ien s a e o al knee a h oplas y. Clin O hop Rela Res 2014; 472 (1): 133-7. Pax on E W, Fu nes O, Namba R S, Inacio M C, Fens ad A M, Ha elin L I. Compa ison o he No wegian Knee A h oplas y Regis e and a Uni ed S a es a h oplas y egis y. J Bone Join Su g Am 2011; 93 Suppl 3: 20-30. P ice A J, Longino D, Rees J, Rou R, Pandi H, Ja aid K, A den N, Coope C, Ca A J, Dodd C A, Mu ay D W, Bea d D J. A e pain and unc ion be e measu es o ou come han e ision a es a e TKR in he younge pa ien ? Knee 2010; 17 (3): 196-9. Rand J A, T ousdale R T, Ils up D M, Ha msen W S. Fac o s a ec ing he du abili y o p ima y o al knee p os heses. J Bone Join Su g Am 2003; 85-A (2): 259-65. Robe sson O, Bizjaje a S, Fens ad A M, Fu nes O, Lidg en L, Mehne F, Odgaa d A, Pede sen A B, Ha elin L I. Knee a h oplas y in Denma k, No way and Sweden. A pilo s udy om he No dic A h oplas y Regis e Associa ion. Ac a O hop 2010; 81 (1): 82-9. Robe sson O, Rans am J, Sundbe g M, W-Dahl A, Lidg en L. The Swedish Knee A h oplas y Regis e : A e iew. Bone Join Res 2014; 3 (7): 217-22. Sil e wood V, Blagoje ic-Bucknall M, Jinks C, Jo dan J L, P o he oe J, Jo dan K P. Cu en e idence on isk ac o s o knee os eoa h i is in olde adul s: A sys ema ic e iew and me a-analysis. Os eoa h i is Ca ilage 2015; 23 (4): 507-15. Skou S T, Roos E M, Lau sen M B, Ra hle M S, A end -Nielsen L, Simon- sen O, Rasmussen S. A andomized, con olled ial o o al knee eplace- men . N Engl J Med 2015; 373 (17): 1597-606. Slo e J, Espehaug B, Ha elin L I, Engesae e L B, Fu nes O, Tomek I, Tos e- son A. Cos -e ec i eness o unicompa men al and o al knee a h oplas y in elde ly low-demand pa ien s. A ma ko decision analysis. J Bone Join Su g Am 2006; 88 (11): 2348-55. W-Dahl A, Robe sson O, Lidg en L. Su ge y o knee os eoa h i is in younge pa ien s. Ac a O hop 2010a; 81 (2): 161-4. W-Dahl A, Robe sson O, Lidg en L, Mille L, Da idson D, G a es S. Uni- compa men al knee a h oplas y in pa ien s aged less han 65. Ac a O hop 2010b; 81 (1): 90-4. Wells V M, Hea n T C, McCaul K A, Ande on S M, Wigg A E, G a es S E. Changing incidence o p ima y o al hip a h oplas y and o al knee a h o- plas y o p ima y os eoa h i is. J A h oplas y 2002; 17 (3): 267-73. 10097 Niemela inen D.indd 17810097 Niemela inen D.indd 178 3/16/2017 11:17:28 AM3/16/2017 11:17:28 AM