Purpose:​ To evaluate the effectiveness of intraoperative stress test for diagnosis of occult Lisfranc injury.

Materials and Methods:​ Between April 2009 and October 2012, 21 patients with occult Lisfranc injuries underwent intraoperative stress test and internal fixation. There were 11 males and 10 females with an average age of 45.3 years (range, 23~79 years). Injuries were caused by traffic accident in 10 cases, indirect force (twisting injury) in 8 cases, and crush in 2 cases, falling from a height in 1 case. Unstable injuries on stress radiograph in occult injury of Lisfranc joint were treated by open reduction or closed reduction and fixation with cannulated screw or K-wire. Radiological evaluation was assessed according to preoperative and postoperative diastasis between 1st and 2nd metatarsal base.

Results:​ Assoicated injuries were 9 cases of metatarsal fractures, 6 cases of cuneiform fractures and 6 cases of both metatarsal and cuneiform fractures. Medial and middle column fixation was in 13 cases, and three columns fixation was in 8 cases. Initial diastasis between 1st and 2nd metatarsal base was 2.8 mm (1.3~4.7 mm) on AP radiograph and postoperative diastasis between 1st and 2nd metatarsal base was 1.2 mm (0.5~2.4 mm) on AP radiograph.

Conclusion:​ Even there is no sign of clear Lisfranc injury, it is necessary to pay attention and give evaluation on circumstances of occult Lisfranc injuries with metatarsal or cuneiform fractures. Intraoperative stress test is helpful to diagnose an occult Lisfranc injury. For unstable injuries on stress radiographs of occult Lisfranc joint injury, operative treatment with open or closed reduction and internal fixation is useful method.