Background: During operative treatment of bunions, an attempt is made to correct the hallux valgus angle (HVA) and the intermetatarsal angle (IMA). In this study, the HVA and the IMA were measured using intraoperative C-arm fluoroscopic images obtained during surgical treatment of a bunion with chevron osteotomy. These angles were again measured using weight-bearing radiographs obtained 4 to 6 weeks postoperatively.

Methods: At our institution, we reviewed medical records of patients who underwent a bunion repair with chevron osteotomy between January 2013 and October 2017. A total of 26 feet from 24 patients were included. Three authors (ALP, TMH, and RAM) measured the HVA and IMA using intraoperative fluoroscopic images and postoperative weight-bearing radiographs (4 measurements per foot; total, 104 measurements). The authors were blinded to their previous angular measurements and to measurements made by the others. An intraclass correlation coefficient was calculated for the HVA and IMA measurements between groups (ie, intraoperative fluoroscopic images and postoperative radiographs) to determine interobserver reliability. We compared the angles measured by the authors between groups and used a paired t test for statistical evaluation.

Results: Interobserver difference of the HVA and IMA was low between intraoperative fluoroscopic images and postoperative weight-bearing radiographs (0.98 and 0.79; 0.78 and 0.95, respectively). The measured IMAs were relatively consistent between groups (6.21° and 6.37°, respectively); only two patients had a difference > 3°. There was a greater difference in HVAs between groups (11.5° and 14.2°, respectively). In 11 feet, the HVA was > 5° (range, 5.3-12.7°) in the postoperative radiograph compared to the fluoroscopic image. In one foot, we noted a 7° decrease of the HVA on the postoperative radiograph. The average difference of HVA between groups was 2.6° (P < 0.0001), whereas the IMA was 0.16° (P = 0.002).

Conclusions: Interobserver measurements of the HVA and IMA were reliable on both the intraoperative fluoroscopic images and the postoperative weightbearing radiographs. The IMA was similar between groups; however, the HVA was often greater on the postoperative weight-bearing radiographs.

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