A biomechanical study of simulated femoral neck fracture fixation by cannulated screws: effects of placement angle and number of screws.
The angle of placement of hip screws to fix femoral neck fractures is still a controversial subject, and it must be addressed. In the study reported here, we compared the relative stiffness of fixation of simulated Pauwels type III femoral neck fractures fixed with either 2 or 3 cannulated screws implanted at 135 degrees, 145 degrees, and 150 degrees. Each femur was fixed with 2 or 3 cannulated screws and tested under axial loading and anteroposterior (AP) bending. Then each femur was fatigued to 1000 cycles and tested to failure. Fourteen femurs were tested. Results showed that axial stiffness values were not statistically different at different angles. AP bending stiffness of the high-angle (150 degrees) construct was significantly higher than that of either of the other 2 constructs (for 2 screws only). Two-screw fixation appears to be adequate; adding a third screw may not be necessary.
Walker
Earl
E
Department of Orthopaedic Surgery, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA.
Mukherjee
Debi P
DP
Ogden
Alan L
AL
Sadasivan
Kalia K
KK
Albright
James A
JA
D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D005260:Female; D005265:Femoral Neck Fractures / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D016059:Range of Motion, Articular; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D016474:Weight-Bearing