Risk factors associated with revision for prosthetic joint infection after hip replacement: a prospective observational cohort study.

Background: The risk of prosthetic joint infection (PJI) is influenced by patient, surgical, and health-care factors. Existing evidence is based on short-term follow-up. It does not differentiate between factors associated with early onset caused by the primary intervention from those associated with later onset more likely to result from haematogenous spread. We aimed to assess the overall and time-specific associations of these factors with the risk of revision due to PJI after primary total hip replacement.

Methods: We did a prospective observational cohort study analysing 623 253 primary hip procedures performed between April 1, 2003, and Dec 31, 2013, in England and Wales and recorded the number of procedures revised because of PJI. We investigated the associations between risk factors and risk of revision for PJI across the overall follow-up period using Poisson multilevel models. We reinvestigated the associations by post-operative time periods (0-3 months, 3-6 months, 6-12 months, 12-24 months, >24 months) using piece-wise exponential multilevel models with period-specific effects. Data were obtained from the National Joint Registry linked to the Hospital Episode Statistics data.

Findings: 2705 primary procedures were subsequently revised for an indication of PJI between 2003 and 2014, after a median (IQR) follow up of 4·6 years (2·6-7·0). Among the factors associated with an increased revision due to PJI there were male sex (1462 [1·2‰] of 1 237 170 male-years vs 1243 [0·7‰] of 1 849 691 female-years; rate ratio [RR] 1·7 [95% CI 1·6-1·8]), younger age (739 [1·1‰] of 688 000 person-years <60 years vs 242 [0·6‰] of 387 049 person-years ≥80 years; 0·7 [0·6-0·8]), elevated body-mass index (BMI; 941 [1·8‰] 517 278 person-years with a BMI ≥30 kg/mvs 272 [0·9‰] of 297 686 person-years with a BMI <25 kg/m; 1·9 [1·7-2·2]), diabetes (245 [1·4‰] 178 381 person-years with diabetes vs 2120 [1·0‰] of 2 209 507 person-years without diabetes; 1·4 [1·2-1·5]), dementia (5 [10·1‰] of 497 person-years with dementia at 3 months vs 311 [2·6‰] of 120 850 person-years without dementia; 3·8 [1·2-7·8]), previous septic arthritis (22 [7·2‰] of 3055 person-years with previous infection vs 2683 [0·9‰] of 3 083 806 person-years without previous infection; 6·7 [4·2-9·8]), fractured neck of femur (66 [1·5‰] of 43 378 person-years operated for a fractured neck of femur vs 2639 [0·9‰] of 3 043 483 person-years without a fractured neck of femur; 1·8 [1·4-2·3]); and use of the lateral surgical approach (1334 [1·0‰] of 1 399 287 person-years for lateral vs 1242 [0·8 ‰] of 1 565 913 person-years for posterior; 1·3 [1·2-1·4]). Use of ceramic rather than metal bearings was associated with a decreased risk of revision for PJI (94 [0·4‰] of 239 512 person-years with ceramic-on-ceramic bearings vs 602 [0·5‰] of 1 114 239 peron-years with metal-on-polyethylene bearings at ≥24 months; RR 0·6 [0·4-0·7]; and 82 [0·4‰] of 190 884 person-years with ceramic-on-polyethyene bearings vs metal-on-polyethylene bearings at ≥24 months; 0·7 [0·5-0·9]). Most of these factors had time-specific effects. The risk of revision for PJI was marginally or not influenced by the grade of the operating surgeon, the absence of a consultant surgeon during surgey, and the volume of procedures performed by hospital or surgeon.

Interpretation: Several modifiable and non-modifiable factors are associated with the risk of revision for PJI after primary hip replacement. Identification of modifiable factors, use of targeted interventions, and beneficial modulation of some of these factors could be effective in reducing the incidence of PJI. It is important for clinicians to consider non-modifiable factors and factors that exhibit time-specific effects on the risk of PJI to counsel patients appropriately preoperatively.

Funding: National Institute for Health Research.