To assess the association of specific comorbidities with periprosthetic fractures after primary total knee replacement (TKA)
We used the prospectively collected data in the Mayo Clinic Total Joint Registry from 1989-2008 on all patients who had undergone primary TKA. The outcome of interest was postoperative periprosthetic fractures during the follow-up. Main predictors of interest were comorbidities grouped from the validated Deyo-Charlson index. Multivariable-adjusted Cox regression analyses adjusted for gender, age, body mass index (BMI), American Society of Anesthesiology (ASA) class, operative diagnosis and implant fixation. Hazard ratios and 95% confidence intervals were calculated.
We included 17,633 primary TKAs with a mean follow-up of 6.3 years. The mean age was 68 years, 55% were women and mean BMI was 31. There were 188 postoperative periprosthetic fractures on postoperative day one or later; 162 fractures (86%) occurred postoperative day 90 day or later. In multivariable analyses that simultaneously adjusted for all comorbidities and other variables (age, gender, BMI, ASA, operative diagnosis, cement status), two conditions were significantly associated with increased hazard of postoperative periprosthetic fractures: peptic ulcer disease, hazard ratio of 1.87 (95% confidence interval:1.28, 2.75; p=0.0014); and chronic obstructive pulmonary disease (COPD) hazard ratio of 1.62 (95% confidence interval:1.10, 2.40; p=0.02).
Peptic ulcer disease and COPD are associated with higher risk of periprosthetic fractures after primary TKA. This may be related to the disease or their treatments, which needs further study. Identification of specific risk factor may allow for implementation of intervention strategies to reduce this risk.