Applied Anatomy Of Lag Screw Placement Internal Fixation In Anterior Column Of Acetabular Bone Via Kocher-langenback Surgical Approach

Objective To provide anatomic basis for lag screw placement internal fixation in anterior column of acetabular bone via kocher-langenback surgical approach. Method (1)50 adult hip bones (32 male,18 female) were observed for the direction of the long axis of acetabular anterior column and the position where the long axis penetrates the bone cortex. Then the point where the long axis of acetabular anterior column penetrates the outside of the iliac wing was set as the entering point of the screw in kocher-langenback surgical approach. A guiding pin (3.5mm in diameter) was inserted at the entering point and along the long axis of acetabular anterior column, and the penetration was below the pubic tubercule. The angle between the guiding pin and the sagittal planeα, the angle between the pin and coronal planeβ, length of the longitudinal axis of the acetabular anterior column, the"weak zone"where the guiding pin may easily penetrate bone cortex after inserted into the acetabular anterior column, and the distance from the penetration point to the pubic tubercle, were measured. All the measurement data were calculated by SPSS software. (2)34 corpse specimens were anatomized and observed for the distribution of the vessels and nerves around the Entering point of the guiding pin. The screw fixation of the anterior column was simulated in the specimens, and the study results were measured and examined with X-ray and CT scans. Result The screw Entering point was at the intersection between the line from tubercle of iliac crest to the middle of the ischial tuberosity and the line from anterior superior iliac spine to greater sciatic notch vertex. The exit point of the screw was(6.62±2.79)mm in males and(11.71±1.66)mm in females, respectively. Theαangle was(51.29±3.48)o, while theβangle was(22.32±3.66)o in males and(19.57±2.07)o in females, respectively. The length of longitudinal axis of the acetabular anterior column was(108.64±5.49)mm in males and(100.92±6.25)mm in females, respectively. The distance between the Entering point and"weak zone 1"(between the anterior inferior iliac spine and the migration of eminentia iliopectinea) of the anterior column was(42.15±3.50)mm in males and(38.09±2.50)mm in females, while the distance between the Entering point and"weak zone 2"(at the obturator formamen) was(80.72±4.85)mm in males and (73.82±2.62)mm in females. All the said data exceptαwere of remarkable statistical significance. The simulated fixation showed appropriateness of the screw placement with satisfactory clinical effect. Conclusion It is convenient and safe to place the lag screw to fix the anterior column while fixing the posterior column via kocher-langenback surgical approach in case of compound fracture of both anterior and posterior column of acetabular bone.