Anterior or posterior obliquity of the lag screw in the lateral view--does it affect the sliding characteristics on unstable trochanteric fractures?
We investigated the sliding pattern characteristics of proximal fragment in 16 proximal femur models of 31-A2.1 type trochanteric fractures fixed with dynamic hip screw system under load. In eight models, the lag screw was inserted with an anterior-to-posterior vector within the neck and the head of femur (group 1). The other eight had a posterior-to-anterior vector (group 2). A force of 500 N (30 cycles) was applied to the fracture fragment-plate complex using the Instron 6022. No significant difference was noted in the sliding distance between the two groups (p=0.17). However, the mean angle of rotation of the proximal fragment was twice as great in group 1 (16+/-3.7 degrees ) than that in group 2 (8.1+/-1.5 degrees ) (p<0.001). In group 1, early eccentric contact in the anterior aspect of the intertrochanteric area caused internal rotation of the proximal fragment. Breakage of the anterior cortex of the lateral wall was noted in five out of the eight cases in group 1 and no case in group 2 (p=0.026). Fracture of the anterior cortices significantly threatened the integrity of the lateral wall in group 1.
Park
Si Young
SY
Department of Orthopaedic Surgery, Yonsei University, College of Medicine, Seoul, Republic of Korea.
Park
Jin
J
Rhee
Dong Joo
DJ
Yoon
Han Kook
HK
Yang
Kyu Hyun
KH
D001863:Bone Screws; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation*; D006620:Hip Fractures / Q000601:surgery*; D006801:Humans; D008953:Models, Anatomic