RISK FACTORS FOR INFECTION IN HIP ARTHROPLASTY: A CASE-CONTROL STUDY

Abstract

Introduction: Deep infection continues to be the second most important early complication in hip arthroplasty. It is usual to apply standard prophylaxis to all patients, but it is not usual to use special measures in those of them who present a higher risk. Moreover, sometimes these patients are even not identified.

Purpose: To analyse statistically significant risk factors for deep infection in patients with a hip arthroplasty

Patients and Methods:

Design: Case-control study.

Observational and retrospective comparison of incidence or prevalence of all risk factors described in the literature. These factors have been classified according to the period of risk in: epidemiologic; pre, intra and postoperative; and distant infections.

Case series: 47 consecutive patients with a deeply infected hip arthroplasty operated in the same Department of a University General Hospital.

Control series: 200 randomly selected patients, operated in the same hospital and period of time, with no deep infection in their hip arthroplasty along follow-up.

Pearson was used for comparison of qualitative variables and ANOVA for quantitative ones.

Results: The following risk factors were significantly more frequent (p< 0.05) in the patients with an infected hip arthroplasty:

• Epidemiologic characteristics: female gender, post-traumatic osteoarthritis (17% vs 3%). On the contrary, primary osteoarthritis is a “protective” factor.

• Preoperative conditions: previous surgery in the same hip (60% vs 6%), obesity (BMI> 30) (9% vs 1%), chronic therapy with glucocorticoids (13% vs 0%), immunosuppressive treatments, chronic liver diseases (20% vs 2%), alcohol addiction (13% vs 0%) and intravenous drug abuse. Patients in this case-control did not present a significant difference in the prevalence of diabetes (a recognised risk factor for spine and knee surgery) or rheumatoid arthritis.

• Intraoperative facts: a prolonged surgical time is the only significant risk factor (133 min vs 98 min), but differences were not found in the amount of bleeding, need for transfusion or intraoperative fractures.

• Postoperative events: secretion of the wound longer than 10 days (46% vs 8%), palpable deep haematoma (27% vs 1%), dislocation of the prosthesis (40% vs 6%), and need for new surgery in the hip (21% vs 1%).

• Distant infections (risk for haematogenous seeding): deep cutaneous (30% vs 8%), upper and lower urinary tract (36% vs 2%), pneumonias and bronchopneumonias (23% vs 5%), and diverse abdominal focus (14% vs 3%). On the contrary, significant differences were not found in the prevalence of severe oral or dental infections.

Conclusion: To identify significative risk factors for deep infection in hip arthroplasty is important:

1. to control and minimize these risk factors when present

2. when this is not possible not possible, to implement additional prophylactic measures.