Tile Classification — Pelvic Ring Stability

Overview — Pelvic Ring Stability

The Tile classification of pelvic ring fractures (Tile 1988, further developed with Pennal and Helfet into the AO/OTA pelvic classification) is the primary stability-based classification system for pelvic ring injuries. It grades fractures according to the integrity of the posterior sacroiliac (SI) complex — the primary determinant of pelvic ring stability — and divides injuries into three main types based on whether the posterior arch is intact (stable), rotationally disrupted but vertically stable, or completely unstable in all planes. This classification directly guides surgical decision-making and predicts haemorrhage risk and long-term functional outcomes.

The posterior SI complex as the stability determinant: the pelvis is a closed ring structure requiring that force applied to one area is transmitted to all others; the posterior sacroiliac complex (the posterior SI ligaments — the strongest ligaments in the body — plus the interosseous SI ligaments, the sacrospinous and sacrotuberous ligaments) is the PRIMARY determinant of pelvic stability; when the posterior SI complex is intact, even with anterior ring disruption, the pelvis maintains vertical stability; when the posterior complex is disrupted, vertical translation of the hemipelvis occurs (the most unstable pattern); the anterior ring structures (pubic symphysis, pubic rami) contribute to rotational stability but NOT vertical stability; a pelvic injury with only anterior ring disruption and intact posterior complex = rotationally unstable but vertically stable
Pelvic ring anatomy and the `ring`: the pelvis forms a ring composed of the sacrum posteriorly + the two innominate bones (ilium, ischium, pubis) laterally and anteriorly + connected by the pubic symphysis anteriorly and the SI joints posteriorly; for the ring to fracture or dislocate, it must be disrupted in at least two places (Pennal`s rule — a ring can only break in two places); this means that a pubic ramus fracture should always prompt a search for a posterior ring injury (and vice versa)

Tile Classification — Types A, B, C

Type	Stability	Posterior SI Complex	Subtypes	Haemorrhage Risk
Type A — Stable	STABLE — the posterior arch is INTACT; the posterior SI ligaments are undamaged; the pelvis will not displace further	INTACT — no posterior arch disruption; the ring is breached anteriorly (if at all) but the posterior complex holds	A1 — avulsion fractures (ASIS from sartorius, AIIS from rectus femoris, ischial tuberosity from hamstrings); A2 — iliac wing fractures (Duverney fractures — direct lateral blow); undisplaced pubic rami fractures (stress fractures, isolated rami fractures in elderly); A3 — transverse sacral fractures below S2 (sacrococcygeal injuries)	LOW — the posterior arch is intact; haematoma is contained; no large presacral or retroperitoneal space disrupted by posterior ring displacement
Type B — Rotationally unstable, vertically stable	ROTATIONALLY UNSTABLE but VERTICALLY STABLE — the posterior SI complex is partially disrupted (the ANTERIOR sacroiliac ligaments ± sacrospinous and sacrotuberous ligaments are torn) but the POSTERIOR SI ligaments (the strongest component) remain INTACT; this intact posterior complex prevents vertical translation	PARTIALLY DISRUPTED — the anterior ligamentous structures of the SI joint are torn; the posterior SI ligaments are intact; the hemipelvis can rotate (externally or internally) but CANNOT translate vertically because the posterior ligaments are intact	B1 — `Open book` (APC II/III equivalent — external rotation of one hemipelvis; symphysis diastasis >2.5 cm; anterior SI ligaments + sacrospinous + sacrotuberous torn; posterior SI INTACT); B2 — Lateral compression (LC I/II — internal rotation; ipsilateral pubic rami fractures + ipsilateral sacral impaction; or crescent fracture — partial disruption of the SI joint through the iliac wing; posterior SI PARTIALLY intact); B3 — Bilateral B-type injuries (`bucket-handle` — one side internally rotated, one side externally)	MODERATE to HIGH (B1 `open book` carries the highest haemorrhage risk among B-type injuries because the pelvic volume is DRAMATICALLY increased by the external rotation — opening the `book` increases the retroperitoneal space and allows greater blood accumulation; pelvic binder = close the `book` = reduce volume = tamponade venous haemorrhage)
Type C — Rotationally AND vertically unstable	ROTATIONALLY AND VERTICALLY UNSTABLE — complete disruption of the posterior SI complex; ALL posterior ligaments (posterior SI + interosseous SI + sacrospinous + sacrotuberous) are torn; the hemipelvis is free to translate in ANY direction — superiorly (vertical shear), anteriorly/posteriorly, or rotate; this is the MOST UNSTABLE pelvic ring injury	COMPLETELY DISRUPTED — all posterior ligaments torn; complete SI joint dislocation, or sacral fracture Zone II/III, or iliac wing fracture with posterior extension fully through the posterior SI complex; NO remaining posterior stabilisers	C1 — Unilateral complete disruption (one hemipelvis completely unstable); C2 — Bilateral complete disruption (BOTH hemipelves completely unstable — maximally unstable pelvis); C3 — Complete disruption + acetabular fracture on the same side	VERY HIGH — the completely unstable hemipelvis can translate superiorly, tearing the presacral venous plexus and the superior gluteal artery; the retroperitoneal space is effectively unlimited; massive uncontrolled haemorrhage; mortality in haemodynamically unstable Type C fractures is 30–50% without prompt haemorrhage control

Emergency Management of Haemodynamically Unstable Pelvic Fractures

Pelvic binder: the FIRST intervention for a haemodynamically unstable Type B1 (open book) pelvic fracture in the emergency department; a circumferential compression device (SAM Pelvic Sling, T-POD, or even a folded bed sheet) applied at the level of the GREATER TROCHANTERS (not the iliac crests — too high and creates a `trumpet` deformity of the iliac wings without closing the SI joint); the binder approximates the hemipelves, reduces pelvic volume, and tamponades venous haemorrhage from the presacral plexus; the binder should be applied in the field by paramedics and confirmed on the trauma bay AP pelvis X-ray (the binder should overlay the greater trochanters); Note: pelvic binders are MOST EFFECTIVE for B1 open-book injuries (external rotation); they are LESS effective for lateral compression (LC) injuries (the hemipelvis is already internally rotated — further compression with a binder does not reduce the fracture and may actually worsen an LC injury)
Pelvic packing (preperitoneal pelvic packing — PPP): surgical packing of the presacral space through a small suprapubic incision without entering the peritoneal cavity; large surgical swabs are placed into the pelvic retroperitoneal space bilaterally, applying direct pressure to the presacral venous plexus (the source of ~85% of pelvic haemorrhage); performed in the operating room; highly effective for venous haemorrhage; packs are removed at 24–48 hours; PPP is the first-line surgical haemorrhage control option at most major trauma centres
Angioembolisation: for ARTERIAL pelvic haemorrhage (arterial bleeding accounts for ~15% of pelvic haemorrhage — predominantly the superior gluteal artery from the posterior pelvis); performed by interventional radiology; selective catheterisation and embolisation of the bleeding vessel; required when the patient continues to bleed despite binder + pelvic packing (suggesting arterial source); not effective for venous haemorrhage; REBOA (Resuscitative Endovascular Balloon Occlusion of the Aorta) Zone III placement can bridge the patient to definitive haemostasis

Definitive Fixation

Anterior ring: symphysis diastasis >2.5 cm → symphyseal plate fixation; pubic rami fractures → INFIX (subcutaneous anterior pelvic fixator) or rami screws; external fixator (anterior pelvic frame) for temporary stabilisation in haemodynamic instability
Posterior ring: percutaneous iliosacral (IS) screw fixation is the gold standard for posterior pelvic ring stabilisation; a 7.3 mm or larger cannulated screw is placed under fluoroscopic guidance through the SI joint and into the S1 (or S2) sacral body; the screw trajectory must be within the safe `sacral corridor` (the bone between the S1 neural foramina, the upper sacral endplate, and the anterior sacral cortex); misplaced screws risk S1 nerve root injury (anterosuperior placement) or S2 nerve root injury (posterior placement); CT post-operatively confirms screw position; performed under fluoroscopic guidance (inlet, outlet, and lateral views confirm safe corridor placement)

Exam Pearls

Tile classification: A = stable (posterior arch intact); B = rotationally unstable, vertically stable (anterior SI torn, posterior SI INTACT); C = rotationally AND vertically unstable (ALL posterior ligaments torn); based on posterior SI complex integrity
Type B1 (open book): external rotation; symphysis >2.5 cm; anterior SI + sacrospinous/sacrotuberous torn; posterior SI INTACT; pelvic binder MOST effective for this type; reduces volume and tamponades venous haemorrhage
Pelvic binder position: over the GREATER TROCHANTERS (not the iliac crests); trochtanter level closes the SI joint and reduces pelvic volume; iliac crest level opens the pelvis (trumpet deformity); check AP pelvis X-ray to confirm correct binder position
Type C: ALL posterior ligaments torn; vertically AND rotationally unstable; vertical shear mechanism (fall from height); superior migration of hemipelvis; highest mortality; highest haemorrhage risk
Haemorrhage sources: venous (presacral plexus ~85% — responds to pelvic binder and packing); arterial (~15% — superior gluteal artery most common → requires angioembolisation); ongoing haemorrhage despite binder + packing = arterial source → angiography
IS screw corridor: placed into the S1 sacral body through the SI joint; safe corridor = between the foramina (inferiorly), the upper endplate (superiorly), and the anterior sacral cortex (anteriorly); check on inlet (anterior cortex), outlet (neuroforamina), and lateral views (S1 body); L5 root at risk with superiorly placed screw
Type A management: stable fractures; non-operative in most cases; protected weight-bearing; avulsion fractures in athletes (large fragment >1.5 cm with significant displacement) may require ORIF for return to sport; most isolated pubic rami fractures in elderly = conservative management

Tile Classification — Pelvic Ring Stability

References

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