Normal Anatomy Ossification Osteology & Attachments Anterior view Posterior view Lateral view Radiographic Views AP view Positioning patient supine legs IR 15-20° beam aim midway between ASIS + pubic symphysis Indications pelvic/acetabular fractures assess 6 lines posterior rim (1) = posterior wall/column posterior horn of acetabulum more lateral + horizontal line anterior rim (2) = anterior wall/column inferior margin of superior pubic ramus more medial + horizontal line sourcil (3) = anterior/posterior column acetabular roof = superior weight-bearing portion normal 45-60° arc teardrop (4) = anterior/posterior column external/lateral limb = inferior anterior acetabular wall + outer cotyloid fossa lower border = ischiopubic/acetabular notch + superior obturator foramen internal/medial limb = outer wall of obturator canal + quadrilateral surface internal + external limbs = not in same coronal plane but usually parallel + forms U ilioischial line (5) = posterior column pelvic brim + quadrilateral surface + posterior obturator foramen + ischiopubic ramus always superimposed on teardrop = disruption 2/2 rotation vs. quadrilateral surface Fx iliopectineal line (6) = anterior column anterior ¾ = pelvic brim, pubic symphysis to ilioischial line posterior ¼ = lower ½ of sciatic buttress to roof of greater sciatic notch Critique no pelvic tilt coccyx located 2cm above pubic symphysis no rotation of pelvis sacrum in midline symmetrical greater trochanters + obturator foramen no visualization of lesser trochanters too much external rotation of leg leads to increased visualization of lesser trochanter if lesser trochanters are visible, they should be of symmetrical size and shape Lateral view Positioning patient supine vs. lateral decubitus beam aim 5cm above greater trochanters Critique no superimposition of femurs + pubic arch achieve via leg extension superimposition of femurs + acetabulum superimposition of posterior ischium/ilium Axial/Chassard-Lapine view Positioning patient seated + leaning forward pelvis tilted anteriorly 45° + hips abducted beam aim between greater trochanters Indications assess relationship of femoral head + acetabulum measurement of horizontal/bi-ischial diameter Critique symmetrical greater trochanters equal distance between greater trochanters + sacrum Inlet view Positioning patient supine legs IR 15-20° beam aim at ASIS + 40° caudad Indications AP displacement + IR/ER of hemipelvis rotational stability of pelvis SI joint widening sacral Fx Critique superimposition of S1 + S2 body Outlet view Positioning patient supine legs IR 15-20° beam aim 5cm below pubic symphysis til 20-35° cephalad if male, 30-45° cephalad if female Indications vertical displacement + flexion/extension of hemipelvis SI joint widening sacral Fx Critique superimposition of pubic symphysis + S2 body open obturator foramen Judet view Positioning patient iliac oblique = semi-lateral 45° on ipsilateral side obturator oblique = semi-lateral 45° on contralateral side beam aim 5cm medial + inferior to ASIS Indications iliac oblique = anterior wall + posterior column obturator oblique = posterior wall + anterior column Critique iliac oblique = visualization of iliac wing obturator oblique = open obturator foramen Normal Radiographic Findings Female pelvis wider in the mediolateral dimensionsuprapubic angle > 90° Male pelvis wider in AP dimension suprapubic angle < 90° Normal variants phleboliths calcifications in walls of veins usually found laterally around bladder can be symmetrical can occur in clusters os acetabuli located at anterosuperior margin of acetabulum round in shape with concave lateral border and convex medial border may be bilateral and partially fused to the acetabulum paraglenoidal sulcus groove at insertion of anterior SI ligament commonly seen in multiparous females associated with osteitis condensans ilii Risser staging (based on ossification of iliac crest) Radiographic Clinical Pearls Pelvic Avulsion Fracture More common in pediatric patients occurs at apophysis MUSCLE NON-OP TREATMENT CRITERIA Iliac crest abdominal muscles always ASIS sartorius + TFL < 3 cm displacement AIIS rectus femoris always Ischial tuberosity hamstrings (ST, SM, long head of biceps femoris) 1 tendon + < 2 cm displacement Pubic symphysis adductors + gracilis always Pediatric Pelvic Ring Fracture Classification = Torode & Zieg Torode/Zieg Classification Type I • Avulsion injuries Type II • Fractures of the iliac wing Type III • Fractures of the ring with no segmental instability Type IV • Fracture of the ring with segmental instability Recommended views (only detects 50% of pediatric pelvic fractures) AP inlet/outlet judet views if suspected acetabular njury Treatment criteria nonoperative treatment acceptable if type I avulsion injuries with < 2 cm displacement type II iliac wing fractures with < 2 cm displacement type III pelvic ring fractures without segmental instability ORIF vs. ex-fix if type I avulsion injuries with > 2-3 cm displacement type II iliac wing fractures with > 2-3 cm displacement type III pelvic ring with displaced acetabular fractures > 2mm type IV pelvic ring with instability and > 2 cm pelvic ring displacement Pediatric Acetabular Fracture Classification = Bucholz Bucholz Classification Shearing • Salter Harris I or II Blow to pubis/ischial ramus/proximal femur leads to injury at interface of 2 superior arms of triradiate cartilage and metaphyses of ilium. A triangular medial metaphyseal fragment (Thurston-Holland fragment) is often seen in SH II injuries. Crushing/Impaction • Salter Harris V Difficult to see on initial radiographs. May detect narrowing of triradiate space. Leads to premature triradiate cartilage closure. The earlier the closure, the greater the eventual deformity. Recommended views AP judet inlet/outlet views if suspected pelvic ring injury Findings displacement of growth plates disruption of iliopectineal line asymmetric teardrop Treatment criteria nonoperative treatment acceptable if minimally displaced ORIF if comminuted acetabular fracture when traction does not improve the position of fragments joint displacement >2mm joint incongruity intra-articular fragments joint instability (persistent medial subluxation or posterior subluxation) central fracture dislocation open fractures