Applied Anatomy Study Of The Parameters Of The Iliac Screw (Rod) For Lumbopelvic Fixation

Object:To explore the entering spot,the length,the diameter and the direction of the iliac screw in the lumbopelvic fixation operations.To provide anatomic basis Implanting correctly the iliac screw.Methods:A total of 30 side hipbones specimens of native adults were studied.There were 29 side male specimens and 1 side female,14 left side and 16 right side.One line from the arc of the notch between posterior superior iliac spine and posterior inferior iliac spine was difined as the baseline(a).It was extended to acetabulum reason.Anather line(b)was marked through the ischial spine and anterior superior iliac spine.It was intersected with baseline(a)in C spot.The C spot was located on the surface of ilium body behind the acetabulum and determinated as one of reference symbols for implanting iliac screw.The fan-shaped lines were described in the posterior part of iliac through the C spot and the baseline.7 oblique sections were obtained through there fan-shaped lines.Observe various oblique sections shape and survey correlation data above the 10~0～30~0 oblique sections.At the same time,the medial lip,lateral lip and intermediate line in the behind part of iliac were observed.After definiting the entering spot,the length,the diameter and the direction of the iliac screw,these data were verificated in 2 native adut cadavers.Results:35~0 oblique section arrivals to the iliac fossa and 5~0 oblique section clings to the arc of the greater sciatic notch,so the oblique sections above 35~0 and below 5~0 are not determineated as the nail plane for fixation.The perpendicular distances fome A spot to 10~0～30~0 oblique sections are:10~0—left 5.67±1.79mm,right 7.08±1.39mm;15~0—left 8.21±1.23 mm,right 9.79±1.43mm;20~0 left—11.06±1.75mm,right 13.71±2.40mm;25~0—left 14.12±3.62mm,right 16.63±2.83mm;30~0—left17.59±3.40mm,right 20.32±3.59mm.The diameter of the iliac screw bases on(f)line which is the shotest distance between the gluteal surface and pelvic surface.It is next to the pelvic surface and the results are:10~0—left13.97±1.80mm,right 15.08±2.20mm;15~0—left 15.59±2.04mm,right 16.13±2.32mm;20~0—left 14.94±1.53mm,right 15.00±2.22mm;25~0—left 12.99±1.27mm,right 13.62±3.01 mm; 30~0—left 12.08±1.67mm,12.35±2.56mm.The minimum is 10.39mm,so the diameter of iliac screws should not surpass 10mm.The intermediate line on posterior part of the il-iac spine can be distinguished clearly,which is like a regular arc and the most raised part.In the paper,the intermediate line is considered as the anatomic reference of implanting screws. The entering spots are:10~0—left 1.26±1.01mm,right 2.10±1.41mm;15~0—left 2.75±1.10mm,right 1.26±1.60mm;20~0—left 5.04±1.88mm,right 4.13±3.01mm;25~0—left 4.49±3.07mm,right 4.04±3.02mm;30~0—left 5.08±3.66mm,right 5.40±2.62mm.The distances(K) from entering spots to the cartilage of the acetabulum roof are:10~0—left 114.20±4.11 mm,right118.24±8.45mm;15~0—left 116.17±4.59mm,right 118.75±9.36 mm;20~0—left117.63±5.11mm,right20.31±9.80mm;25~0—left 121.94±3.22mm,right 121.11±6.58 mm;30~0—left121.75±3.71mm,right 122.29±5.51mm,in which the minimum is 109.39mm, so the Length of iliac screw should not surpass 100mm.The baseline,the line b and the C spot can be concerned accurately.The angles of implanting screw are determinated by C spot and the outer plate in 10~0～30~0 posterior part of the iliac.Conclusions:The intermediate line on posterior part of the iliac spine can be distinguished clearly, which canbe considered as the anatomic reference of implanting screws.Iliac screws can be implanted accurately and safely by the C spot,the baseline and the outer plate in 10~0～30~0 posterior part of the iliac.the Length of iliac screw should not surpass 100mm and the diameter of iliac screws should not surpass 9mm.