Transverse posterior wall acetabular fracture pattern is associated with increased risk of periprosthetic joint infection after conversion total hip arthroplasty.

INTRODUCTION

Acetabular fracture subtypes are associated with varying rates of subsequent conversion total hip arthroplasty (THA) after open reduction internal fixation (ORIF) with transverse posterior wall (TPW) patterns having a higher risk for early conversion. Conversion THA is fraught with complications including increased rates of revision and periprosthetic joint infections (PJI). We aimed to determine if TPW pattern is associated with higher rates of readmissions and complications including PJI after conversion compared to other subtypes.

METHODS

We retrospectively reviewed 1,938 acetabular fractures treated with ORIF at our institution from 2005 to 2019, of which 170 underwent conversion that met inclusion criteria, including 80 TPW fracture pattern. Conversion THA outcomes were compared by initial fracture pattern. There was no difference between the TPW and other fracture patterns in age, BMI, comorbidities, surgical variables, length of stay, ICU stay, discharge disposition, or hospital acquired complications related to their initial ORIF procedure. Multivariable analysis was performed to identify independent risk factors for PJI at both 90-days and 1-year after conversion.

RESULTS

TPW fracture had higher risk of PJI after conversion THA at 1-year (16.3% vs 5.6%, p = 0.027). Multivariable analysis revealed TPW independently carried increased risk of 90-day (OR 4.89; 95% CI 1.16-20.52; p = 0.03) and 1-year PJI (OR 6.51; 95% CI 1.56-27.16; p = 0.01) compared to the other acetabular fracture patterns. There was no difference between the fracture cohorts in 90-day or 1-year mechanical complications including dislocation, periprosthetic fracture and revision THA for aseptic etiologies, or 90-day all-cause readmission after the conversion procedure.

CONCLUSION

Although conversion THA after acetabular ORIF carry high rates of PJI overall, TPW fractures are associated with increased risk for PJI after conversion compared to other fracture patterns at 1-year follow-up. Novel management/treatment of these patients either at the time of ORIF and/or conversion THA procedure are needed to reduce PJI rates.

LEVEL OF EVIDENCE: Therapeutic Level III (retrospective study of consecutive patients undergoing an intervention with analyses of outcomes).