A new method for reduction quality assessment in acetabular fractures: acetabular congruency measurement.

Introduction: The determination of adequate reduction is difficult perioperatively due to inadequate radiographic scanning and objective measurement methods. The purpose of the present study is to evaluate an objective measurement of the weight bearing acetabular dome congruency. The sensitivity and specificity of 2 measurement methods after acetabular fracture fixation are compared.

Patients And Methods: Postoperative acetabular reduction was assessed based on postoperative anteroposterior radiographs according to hip joint congruency and Matta's classification in 55 patients. For hip joint congruency measurements, one circle was drawn as superior femoral head border and another one was drawn as weight-bearing acetabular dome border. The difference between the centres of the circles was measured in millimetres. Comparative studies were performed between groups according to reduction quality and clinical and radiological results.

Results: The threshold value for the difference between the 2 circle centres was found as 4.4 mm according to the clinical outcomes; 3.8 mm according to radiological outcomes in joint congruency method. The sensitivity of this method was found as 90.2% and 92.7%, and specificity as 64.3% and 57.1% considering the clinical and radiological results, respectively. In the assessment of joint congruency, false positive rate was lower than assessing reduction quality using the method defined by Matta.

Conclusions: Joint congruency assessment based on a postoperative anteroposterior radiograph in patients treated with open reduction internal fixation for acetabular fractures is a suitable method for assessing the adequacy of reduction. This method can be used intraoperatively using fluoroscopy imaging during surgery.