APRIL 2012 |฀Volume฀35฀•฀Number฀4 n Feature Article abstract Full article available online at Healio.com/Orthopedics. Search: 20120327-20 Because standard femoral supracondylar nails have certain disadvantages, they are of- ten replaced by traditional femoral or tibial locked nails. The purpose of this study was to make a biomechanical comparison between both types of traditional locked nails to determine which technique was more suitable for treating unstable femoral supracon- dylar fractures. Fourteen left Sawbones femurs (Pacific Research Laboratories, Vashon, Washington) were osteotomized in the femoral supracondylar area. One centimeter of the medial cortex in the proximal fragment was obliquely removed to simulate an unstable fracture without shortening. Seven specimens were treated with traditional retrograde dynamic femoral locked nails, and the other 7 with traditional retrograde dynamic tibial locked nails. All specimens were tested with a servohydraulic materials testing machine to compare their relative stability. Static compression, dynamic cyclic compression, and static compression to failure were tested. An extensometer was used to measure the displacement of fragments. Displacement between the fragments in- creased following the increment in loads in both nails. The load–displacement curve was nearly linear up to 1000 N for both nails. The femoral nail had a greater stiffness compared with the tibial nail at 100 and 200 N (P5.02 and P5.04, respectively) in static compression and at 700 to 1000 N (P5.01 in each case) in dynamic cyclic compression, as well as larger loads in static compression to failure (8663 vs 7547 N, respectively; P,.001). Clinically, a traditional femoral locked nail may be more suit- able to replace a standard femoral supracondylar nail in a retrograde fashion to treat an unstable femoral supracondylar fracture. Dr Wu is from the Department of Orthopedic Surgery, Chang Gung Memorial Hospital, and Dr Tai is from the Graduate Institute of Medical Mechatronics, Department of Mechanical Engineering, Chang Gung University, Taoyuan, Taiwan. Drs Wu and Tai receive financial support from the National Science Council (NSC 98-2314-B-182A-011), Executive Yuan, Republic of China. Correspondence should be addressed to: Chi-Chuan Wu, MD, Department of Orthopedic Surgery, Chang Gung Memorial Hospital, 5 Fu-Hsin St, 333, Taoyuan, Taiwan (ccwu@mail.cgu.edu.tw). doi: 10.3928/01477447-20120327-20 Retrograde Nailing of a Femoral Supracondyle CHI-CHUAN WU, MD; CHING-LUNG TAI, PHD Figure: All specimens were tested with a servohy- draulic materials testing machine for relative stabil- ity. The mechanical axis (from the femoral head to the center of the knee) was vertical to the ground. An extensometer was placed with a vertical contact on the surface of the femoral shaft between both frag- ments medially to measure the displacement. e491