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192 Volume Outcome KCE reports 113
Table 7.26 shows that the most frequent complication observed during hospitalization
(initial or readmissions) within 90 days after admission was a complication due to
internal joint prosthesis with 1.06% (0.88,% 1.27%), followed by 0.82% mechanical
complication (0.66%, 1 %). As explained in the chapter on total hip arthroplasty (see
page 174), there may be some overlap between categories, and some patients
experienced different complications or are readmitted more than once. Therefore, a
global outcome category was created to group all patients who encountered any of the
above complications within 90 days after the initial TKR, with the exception of AMI and
pneumonia. 3.20% (2.88%, 3.55%) of the patients (number = 353) encountered at least
one of the above mentioned post-operative complications within 90 days after the initial
total knee arthroplasty admission. AMI and pneumonia were left out of this global
complication rate for two reasons: to be consistent with the definition for total hip
arthroplasty and because AMI and pneumonia are more generic complications that are
not particular for this orthopaedic intervention.
Table 7.26: Total knee arthroplasty: Outcomes measured during hospital
(re)admission within 90 days of index admission
COMPLICATION WITHIN 90 DAYS
Number number %
total outcome outcome
Deep venous thrombosis 11 017 46 0.42
Pulmonary embolism 11 017 69 0.63
Deep wound infection 11 017 34 0.31
Mechanical complication 11 017 90 0.82
Dislocation of knee 11 017 14 0.13
Other complication due to prosthesis 11 017 117 1.06
Any of the above complications *
Other complications:
11 017 353 3.20
Acute myocardial infarction 11 017 22 0.20
Pneumonia 11 017 62 0.56
* a patient may have more than one complication, but these are counted only once
7.2.5.3 Revision rate at 12 months
Revision rates at 12 months were retrieved by identifying the readmissions with an
ICD-9-CM procedure code 8155 or an NIHDI procedure code 293462 (see Table
7.19).
Table 7.27 shows that less than 1% of the patients needed a revision in the year after
the operation (0.98%). Since we disposed of a 12-month follow-up for all patients, there
was no need to estimate the rate of revision by the Kaplan-Meier method. Revision rate
at 36 months, as is done in scientific literature, was not calculated because data were
not available.
Table 7.27: Total knee arthroplasty: Revision rate at 12 months
Number number % 95% CI
total outcome outcome
Readmission for revision at 12 months 11 017 108 0.98 0.80 1.18