Hounsfield unit values are useful for predicting early outcomes after acetabular fractures: A retrospective study

Abstract

Abstract Background Acetabular fractures are among the most challenging orthopedic fractures, and a high total hip arthroplasty (THA) conversion rate has been reported in older patients with acetabular fractures. Bone quality is a poor prognostic factor after acetabular fractures and has been assessed using computed tomography (CT). However, the relation between Hounsfield unit (HU) values measured using CT and early acetabular fracture outcomes remains unknown. This study aimed to elucidate the effect of Hounsfield units (HU) on early acetabular fracture outcomes. Methods Consecutive 50 patients who underwent open reduction and internal fixation (ORIF) for acetabular fractures were included. The mean follow-up duration was 24 months. The HU values of the fifth vertebral body and unaffected side of the femoral head were measured. The fracture type, radiological hip arthropathy, conversion to THA, and postoperative displacement were recorded. Results All the surgeries were performed by a single orthopedic surgeon. Forty patients were males and 10 were females. The mean patient age was 49.3 years. Twenty-seven hips had elementary fractures and 23 had associated fractures. The reduction quality using CT was as follows: anatomical, 13 hips; imperfect, 10 hips; and poor, 27 hips. Hip arthropathy was observed in 10 patients (10%), and one patient (2%) converted to THA. The unaffected femoral head HU values in elementary fractures (250.5 ± 50.5) was significantly higher than those in associated fractures (221.5 ± 48) (p < 0.047). Both the HU values of the fifth vertebral body and unaffected femoral head were significantly correlated with postoperative residual displacement gap and these values in patients with arthropathy were significantly lower than those without arthropathy. The cut-off value for predicting early arthropathy after an acetabular fracture was approximately 180. Conclusion The HU values were correlated with the fracture type, postoperative displacement gap, and early arthropathy after acetabular fractures and are clinically useful prognostic factors for early acetabular fracture outcomes.