To assess the affecting factors of results after the operation of Crescent fracture-dislocation in sacro-iliac joint.

In 19 patients (mean age, 47.4 year-old) of open reduction and internal fixation for Crescent fracture-dislocation, there were seven type I, 9 type II, and 3 type III fractures according to Day's classification. We assessed affecting factors of radiological and functional results, such as patients' ages, surgical approaches, the fixation extent of pelvic ring, and fracture patterns.

Seventeen of 19 cases united at 14.5 weeks in average, and 2 non-unions occurred with the fixation failure of posterior ring. Satisfactory results were 14 and 15 in radiological and functional evaluation, respectively. In complications, three cases of leg length discrepancy were from an imperfect reduction and two fixation failures. Surgical approach did not show any difference of results, but all cases of unsatisfactory reduction occurred from posterior ring fixation through the anterior approach. Fixation of both rings seemed to have satisfactory results, comparing to posterior ring only. Older patients over 60 year-old had more complications and a tendency to show an unsatisfactory result.

In operative treatment of Crescent fracture-dislocation of sacro-iliac joint, it is better to fix both anterior and posterior rings. But, caution is needed to prevent complications in old-aged patients.