Table.
Sample description and incidence rates
| n | Person-years of follow-up | Cases | Incidence rate per 1000 person-years (95% CI) | ||
|---|---|---|---|---|---|
| Patient characteristics | |||||
| Sex | |||||
| Female | 386 047 | 1 913 858 | 1564 | 0·82 (0·78–0·86) | |
| Male | 292 963 | 1 418 437 | 2095 | 1·48 (1·41–1·54) | |
| Age, years | |||||
| <60 | 109 000 | 537 080 | 793 | 1·48 (1·38–1·58) | |
| 60–69 | 229 107 | 1 143 670 | 1342 | 1·17 (1·11–1·24) | |
| 70–79 | 247 636 | 1 233 478 | 1223 | 0·99 (0·94–1·05) | |
| ≥80 | 93 267 | 418 066 | 301 | 0·72 (0·64–0·81) | |
| Ethnic origin | |||||
| White | 515 098 | 2 491 245 | 3066 | 1·23 (1·19–1·28) | |
| Black African origin | 6011 | 27 217 | 52 | 1·91 (1·43–2·51) | |
| South Asian | 15 510 | 69 500 | 94 | 1·35 (1·09–1·66) | |
| Other and mixed | 6513 | 28 414 | 40 | 1·41 (1·01–1·92) | |
| Unclear | 14 294 | 71 896 | 30 | 0·42 (0·28–0·60) | |
| Unavailable* | 121 584 | 644 023 | 377 | 0·59 (0·53–0·65) | |
| BMI, kg/m2 | |||||
| <25 | 40 333 | 167 416 | 212 | 1·27 (1·10–1·45) | |
| 25–29·9 | 131 560 | 548 505 | 849 | 1·55 (1·45–1·66) | |
| ≥30 | 205 134 | 840 041 | 1558 | 1·85 (1·76–1·95) | |
| Missing | 301 983 | 1 776 333 | 1040 | 0·59 (0·55–0·62) | |
| ASA grade | |||||
| 1 | 92 441 | 523 023 | 490 | 0·94 (0·86–1·02) | |
| 2 | 484 992 | 2 347 559 | 2460 | 1·05 (1·01–1·09) | |
| 3–5 | 101 577 | 461 713 | 709 | 1·54 (1·42–1·65) | |
| Chronic pulmonary disease | |||||
| No | 478 788 | 2 350 416 | 2822 | 1·20 (1·16–1·25) | |
| Yes | 78 638 | 337 856 | 460 | 1·36 (1·24–1·49) | |
| Unavailable* | 121 584 | 644 023 | 377 | 0·59 (0·53–0·65) | |
| Diabetes | |||||
| No | 490 521 | 2 398 439 | 2809 | 1·17 (1·13–1·22) | |
| Yes | 66 905 | 289 833 | 473 | 1·63 (1·49–1·79) | |
| Unavailable* | 121 584 | 644 023 | 377 | 0·59 (0·53–0·65) | |
| Dementia | |||||
| No | 555 783 | 2 682 651 | 3274 | 1·22 (1·18–1·26) | |
| Yes | 1643 | 5621 | 8 | 1·42 (0·61–2·80) | |
| Unavailable* | 121 584 | 644 023 | 377 | 0·59 (0·53–0·65) | |
| Liver disease | |||||
| No | 553 389 | 2 672 866 | 3237 | 1·21 (1·17–1·25) | |
| Yes | 4037 | 15 406 | 45 | 2·92 (2·13–3·91) | |
| Unavailable* | 121 584 | 644 023 | 377 | 0·59 (0·53–0·65) | |
| Congestive heart failure | |||||
| No | 546 613 | 2 643 872 | 3211 | 1·21 (1·17–1·26) | |
| Yes | 10 813 | 44 399 | 71 | 1·60 (1·25–2·02) | |
| Unavailable* | 121 584 | 644 023 | 377 | 0·59 (0·53–0·65) | |
| Connective tissue–rheumatic disease | |||||
| No | 526 493 | 2 547 415 | 3059 | 1·20 (1·16–1·24) | |
| Yes | 30 933 | 140 856 | 223 | 1·58 (1·38–1·81) | |
| Unavailable* | 121 584 | 644 023 | 377 | 0·59 (0·53–0·65) | |
| Cancer | |||||
| No | 534 534 | 2 590 793 | 3170 | 1·22 (1·18–1·27) | |
| Non-metastatic cancer | 20 364 | 87 849 | 95 | 1·08 (0·87–1·32) | |
| Metastatic cancer | 2528 | 9629 | 17 | 1·77 (1·03–2·83) | |
| Unavailable* | 121 584 | 644 023 | 377 | 0·59 (0·53–0·65) | |
| Cerebrovascular disease | |||||
| No | 546 047 | 2 640 626 | 3221 | 1·22 (1·18–1·26) | |
| Yes | 11 379 | 47 646 | 61 | 1·28 (0·98–1·64) | |
| Unavailable* | 121 584 | 644 023 | 377 | 0·59 (0·53–0·65) | |
| Myocardial infarction | |||||
| No | 541 849 | 2 619 164 | 3186 | 1·22 (1·17–1·26) | |
| Yes | 15 577 | 69 107 | 96 | 1·39 (1·13–1·70) | |
| Unavailable* | 121 584 | 644 023 | 377 | 0·59 (0·53–0·65) | |
| Paraplegia and hemiplegia | |||||
| No | 555 229 | 2 678 669 | 3263 | 1·22 (1·18–1·26) | |
| Yes | 2197 | 9603 | 19 | 1·98 (1·19–3·09) | |
| Unavailable* | 121 584 | 644 023 | 377 | 0·59 (0·53–0·65) | |
| Peptic ulcer disease | |||||
| No | 549 071 | 2 649 116 | 3229 | 1·22 (1·18–1·26) | |
| Yes | 8355 | 39 155 | 53 | 1·35 (1·01–1·77) | |
| Unavailable* | 121 584 | 644 023 | 377 | 0·59 (0·53–0·65) | |
| Peripheral vascular disease | |||||
| No | 547 096 | 2 645 530 | 3207 | 1·21 (1·17–1·25) | |
| Yes | 10 330 | 42 742 | 75 | 1·75 (1·38–2·20) | |
| Unavailable* | 121 584 | 644 023 | 377 | 0·59 (0·53–0·65) | |
| Renal disease | |||||
| No | 539 605 | 2 628 852 | 3197 | 1·22 (1·17–1·26) | |
| Yes | 17 821 | 59 419 | 85 | 1·43 (1·14–1·77) | |
| Unavailable* | 121 584 | 644 023 | 377 | 0·59 (0·53–0·65) | |
| Surgical characteristics | |||||
| Osteoarthritis | |||||
| No | 18 529 | 92 371 | 157 | 1·70 (1·44–1·99) | |
| Yes | 660 481 | 3 239 923 | 3502 | 1·08 (1·05–1·12) | |
| Trauma | |||||
| No | 675 193 | 3 313 911 | 3613 | 1·09 (1·05–1·13) | |
| Yes | 3817 | 18 383 | 46 | 2·50 (1·83–3·34) | |
| Previous knee infection | |||||
| No | 678 522 | 3 329 986 | 3644 | 1·09 (1·06–1·13) | |
| Yes | 488 | 2309 | 15 | 6·50 (3·64–10·72) | |
| Avascular necrosis | |||||
| No | 676 515 | 3 319 900 | 3638 | 1·10 (1·06–1·13) | |
| Yes | 2495 | 12 394 | 21 | 1·69 (1·05–2·59) | |
| Inflammatory arthropathy | |||||
| No | 663 410 | 3 251 205 | 3534 | 1·09 (1·05–1·12) | |
| Yes | 15 600 | 81 089 | 125 | 1·54 (1·28–1·84) | |
| Other indication | |||||
| No | 675 312 | 3 317 114 | 3636 | 1·10 (1·06–1·13) | |
| Yes | 3698 | 15 181 | 23 | 1·52 (0·96–2·27) | |
| Surgical approach | |||||
| Medial parapatellar | 629 891 | 3 093 847 | 3 420 | 1·11 (1·07–1·14) | |
| Midvastus | 19 384 | 89 860 | 76 | 0·85 (0·67–1·06) | |
| Lateral parapatellar | 7992 | 42 506 | 47 | 1·11 (0·81–1·47) | |
| Subvastus | 9403 | 48 926 | 49 | 1·00 (0·74–1·32) | |
| Other approach | 12 340 | 57 155 | 67 | 1·17 (0·91–1·49) | |
| Procedure | |||||
| Primary TKR cemented | 569 737 | 2 760 945 | 3227 | 1·17 (1·13–1·21) | |
| Primary TKR uncemented | 33 754 | 188 639 | 153 | 0·81 (0·69–0·95) | |
| Primary TKR other | 7699 | 48 490 | 52 | 1·07 (0·80–1·41) | |
| Unicondylar | 58 885 | 291 906 | 211 | 0·72 (0·63–0·83) | |
| Patellofemoral | 8935 | 42 314 | 16 | 0·38 (0·22–0·61) | |
| Constraint | |||||
| Unconstrained fixed | 397 175 | 1 918 707 | 1987 | 1·04 (0·99–1·08) | |
| Unconstrained mobile | 47 532 | 262 875 | 278 | 1·06 (0·94–1·19) | |
| Posterior stabilised fixed | 144 960 | 705 782 | 981 | 1·39 (1·30–1·48) | |
| Posterior stabilised mobile | 9714 | 51 054 | 54 | 1·06 (0·79–1·38) | |
| Constrained condylar | 2968 | 11 498 | 43 | 3·74 (2·71–5·04) | |
| Fixed | 16 703 | 74 967 | 67 | 0·89 (0·69–1·14) | |
| Mobile | 41 297 | 212 086 | 141 | 0·66 (0·56–0·78) | |
| Undetermined | 18 661 | 95 326 | 108 | 1·13 (0·93–1·37) | |
| General anaesthesia | |||||
| No | 381 156 | 1 788 490 | 1889 | 1·06 (1·01–1·10) | |
| Yes | 297 854 | 1 543 804 | 1770 | 1·15 (1·09–1·20) | |
| Nerve block anaesthesia | |||||
| No | 547 783 | 2 644 393 | 2914 | 1·10 (1·06–1·14) | |
| Yes | 131 227 | 687 902 | 745 | 1·08 (1·01–1·16) | |
| Epidural anaesthesia | |||||
| No | 621 572 | 2 987 043 | 3311 | 1·11 (1·07–1·15) | |
| Yes | 57 438 | 345 251 | 348 | 1·01 (0·90–1·12) | |
| Spinal anaesthesia | |||||
| No | 283 120 | 1 499 422 | 1724 | 1·15 (1·10–1·21) | |
| Yes | 395 890 | 1 832 873 | 1935 | 1·06 (1·01–1·10) | |
| Thromboprophylaxis regimen | |||||
| Chemical | 606 001 | 2 870 437 | 3204 | 1·12 (1·08–1·16) | |
| Non-chemical | 73 009 | 461 857 | 455 | 0·99 (0·90–1·08) | |
| Femoral bone graft | |||||
| No | 675 147 | 3 317 925 | 3635 | 1·10 (1·06–1·13) | |
| Yes | 3863 | 14 370 | 24 | 1·67 (1·07–2·49) | |
| Tibial bone graft | |||||
| No | 676 271 | 3 319 182 | 3629 | 1·09 (1·06–1·13) | |
| Yes | 2739 | 13 112 | 30 | 2·29 (1·54–3·27) | |
| Intraoperative event | |||||
| No | 675 089 | 3 314 501 | 3636 | .. | |
| Yes | 3921 | 17 794 | 23 | 1·29 (0·82–1·94) | |
| Health system characteristics | |||||
| Country of surgery | |||||
| England | 638 835 | 3 136 010 | 3461 | 1·10 (1·07–1·14) | |
| Wales | 40 175 | 196 285 | 198 | 1·01 (0·87–1·16) | |
| Funding | |||||
| NHS | 574 433 | 2 722 013 | 3091 | 1·14 (1·10–1·18) | |
| Private | 75 507 | 395 514 | 362 | 0·92 (0·82–1·01) | |
| Unspecified | 29 070 | 214 768 | 206 | 0·96 (0·83–1·10) | |
| Grade of operating surgeon | |||||
| Consultant | 572 464 | 2 767 937 | 3032 | 1·10 (1·06–1·14) | |
| Other | 106 546 | 564 357 | 627 | 1·11 (1·03–1·20) | |
| Consultant involvement | |||||
| Operating | 572 464 | 2 767 937 | 3032 | 1·10 (1·06–1·14) | |
| Assisting | 38 327 | 188 754 | 223 | 1·18 (1·03–1·35) | |
| Not involved | 68 219 | 375 604 | 404 | 1·08 (0·97–1·19) | |
| Total volume (operating surgeon) of knee replacements done in previous 12 months | |||||
| ≤25 | 173 288 | 988 694 | 1091 | 1·10 (1·04–1·17) | |
| >25–50 | 160 104 | 815 890 | 983 | 1·20 (1·13–1·28) | |
| >50–85 | 170 157 | 788 139 | 816 | 1·04 (0·97–1·11) | |
| >85 | 175 461 | 739 571 | 769 | 1·04 (0·97–1·12) | |
| Total volume (surgeon in charge) of knee replacements done in previous 12 months | |||||
| ≤38 | 173 204 | 1 010 739 | 1113 | 1·10 (1·04–1·17) | |
| >38–70 | 174 209 | 872 816 | 986 | 1·13 (1·06–1·20) | |
| >70–110 | 162 179 | 730 804 | 791 | 1·08 (1·01–1·16) | |
| >110 | 169 418 | 717 936 | 769 | 1·07 (1·00–1·15) | |
| Total volume (hospital) of knee replacements done in previous 12 months | |||||
| ≤150 | 167 930 | 1 008 852 | 984 | 0·98 (0·92–1·04) | |
| >150–285 | 174 288 | 863 114 | 973 | 1·13 (1·06–1·20) | |
| >285–440 | 169 780 | 743 102 | 893 | 1·20 (1·12–1·28) | |
| >440 | 167 012 | 717 227 | 809 | 1·13 (1·05–1·21) | |
ASA=American Society of Anesthesiologists. TKR=total knee replacement. NHS=National Health Service.
*
Information about ethnicity and comorbidities is only available for the 557 426 patients operated on in England with a Hospital Episodes Statistics record, no record in the Patient Episode Database for Wales, and no evidence of residency outside England. See figure 1 and appendix p 2 for more details.