Just like age-de­fy­ing ba­by boomers, old­er folks have seen a surge in knee-re­place­ment surg­eries, dri­ven part­ly by a de­sire to stay ac­tive and by joint-dam­ag­ing obe­si­ty. The find­ings are in a study of more than three mil­lion Medicare pa­tients, aged 65 and old­er, who got ar­ti­fi­cial knees from 1991 through 2010. Al­most 10 per cent of the op­er­a­tions were re­dos-re­plac­ing worn-out ar­ti­fi­cial joints. The num­ber of ini­tial knee-re­place­ment surg­eries each year on these old­er pa­tients more than dou­bled dur­ing that time, ris­ing to near­ly 244,000 in 2010. Pa­tients were in their mid-70s on av­er­age when they had surgery; that age edged up slight­ly dur­ing the study. The age­ing pop­u­la­tion and ris­ing num­bers of Medicare en­rollees con­tributed to the in­crease. But the per capi­ta rate al­so in­creased, from about three surg­eries per 10,000 en­rollees in 1991 to five per 10,000 in 2010.

"There's a huge per­cent­age of old­er adults who are liv­ing longer and want to be ac­tive," and knee re­place­ment surgery is very ef­fec­tive, said lead au­thor Dr Pe­ter Cram, an as­so­ciate pro­fes­sor of in­ter­nal med­i­cine at the Uni­ver­si­ty of Iowa. The pace of growth slowed in more re­cent years-pos­si­bly be­cause in­creas­ing num­bers of younger adults have al­so been get­ting ar­ti­fi­cial knees, which typ­i­cal­ly last 15 to 20 years. The trou­bled econ­o­my may al­so have slowed de­mand for an op­er­a­tion that costs about $15,000, the study au­thors said. About 600,000 knee-re­place­ment surg­eries are done each year na­tion­wide on adults of all ages, cost­ing a to­tal of $9 bil­lion, the au­thors said. A jour­nal ed­i­to­r­i­al says mea­sures are need­ed to con­trol costs of these op­er­a­tions, not­ing that de­mand has been pro­ject­ed to rise to as many as al­most 4 mil­lion knee op­er­a­tions an­nu­al­ly by 2030.

Obese old­er pa­tients get­ting their first op­er­a­tions ac­count­ed for al­most 12 per cent, up from four per cent. The rate was about the same in those get­ting re­dos. Obe­si­ty takes a toll on joints and can con­tribute to arthri­tis, a lead­ing rea­son for knee re­place­ment surgery. The av­er­age hos­pi­tal stay dropped from al­most eight days to three and a half days, but many pa­tients were sent to re­hab cen­tres, most­ly out­pa­tient cen­tres in the most re­cent years. Read­mis­sion rates af­ter first and sec­ond op­er­a­tions in­creased in re­cent years for rea­sons in­clud­ing in­fec­tions and surgery com­pli­ca­tions. The re­sults sug­gest that short­en­ing hos­pi­tal stays doesn't al­ways achieve the goal of re­duc­ing costs, since read­mis­sions in­creased-a trend seen with oth­er types of surg­eries and ill­ness­es. (AP)