Mechanical Testing of Maximal Shift Scarf Osteotomy with Inside-Out Plating Compared to Classic Scarf Osteotomy With Double Screw Fixation.

The purpose of the present study was to biomechanically compare the primary stability of our formerly described inside-out plate fixation to the classic double screw fixation for scarf osteotomy in the treatment of hallux valgus. We performed 20 scarf osteotomies on first metatarsal composite bone models. One half were fixed using a double screw technique and the other half using a locking plate inside-out technique. Using a testing device to simulate the physiologic load, the specimen was loaded until failure, and the load at failure, displacement at failure, and work at failure were recorded. The results were compared between the 2 groups and against the findings from intact sawbones. Compared with the intact bone models, the energy absorption was low for both types of osteotomy fixation. Between the 2 fixation groups, the load at failure was greater for plate fixation, although the difference was not statistically significant (p = .051). However, a statistically significant difference was found between both groups comparing work and displacement at failure (p < .001). In conclusion, the formerly described inside-out plating technique is a biomechanically reasonable alternative to screw fixation because of its primary stability after scarf osteotomy for hallux valgus.