Pelvic & Acetabular Trauma MCQs

The clinical scenario describes an Anteroposterior Compression Type II (APC-II) pelvic ring injury. By definition, an APC-II injury involves disruption of the pubic symphysis (typically >2.5 cm) along with tearing of the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments. The critical distinguishing factor of an APC-II injury from an APC-III injury is that the strong posterior sacroiliac ligaments remain intact, providing vertical stability while allowing rotational instability.

The Young-Burgess classification for APC injuries relies on progressive disruption of the pelvic ring from anterior to posterior. APC-I involves pubic diastasis <2.5 cm with intact posterior ligaments. APC-II involves diastasis >2.5 cm with disruption of the anterior sacroiliac (SI), sacrotuberous, and sacrospinous ligaments, but intact posterior SI ligaments (rotationally unstable, vertically stable). APC-III involves complete disruption of both the anterior and posterior SI ligaments, resulting in a globally (rotationally and vertically) unstable hemipelvis.

For a pelvic binder to be mechanically effective in reducing pelvic volume (especially the posterior ring) and minimizing hemorrhage, it must be centered directly over the greater trochanters. Placement over the iliac crests is a common error and is ineffective at closing the pelvic ring; it can even exacerbate the deformity in some injury patterns.

The injury mechanism is anteroposterior compression (APC). APC-II is characterized by disruption of the symphysis pubis (or anterior ring fractures) along with disruption of the anterior sacroiliac ligaments, sacrotuberous, and sacrospinous ligaments, while the posterior sacroiliac ligaments remain intact. This causes rotational instability but preserves vertical stability. APC-III involves complete disruption of both anterior and posterior SI ligaments, resulting in both rotational and vertical instability.

In a hemodynamically unstable patient with an APC III pelvic ring injury who does not respond to a pelvic binder and initial fluid resuscitation, the source of bleeding is typically venous (presacral plexus) or arterial. Preperitoneal pelvic packing and/or angiography with embolization are the most appropriate next steps to achieve hemodynamic stability before any definitive orthopedic fixation.

In hemodynamically unstable patients with pelvic ring injuries, the first step is mechanical stabilization of the pelvic volume (e.g., pelvic binder or sheet). If the patient remains persistently hypotensive despite resuscitation and stabilization, hemorrhage control is required. Institutional protocols vary between pre-peritoneal pelvic packing (to control venous bleeding, which is the most common source) and angiography with embolization (for arterial bleeding). Laparotomy is contraindicated unless there is a clear concurrent intra-abdominal source of bleeding, as it eliminates the tamponade effect.

While arterial bleeding (commonly from the superior gluteal or internal pudendal arteries) can occur and is often addressed by angioembolization, the vast majority (approximately 80-90%) of life-threatening hemorrhage in blunt pelvic ring injuries arises from the presacral venous plexus and the fractured cancellous bony surfaces. Venous and bony bleeding are primarily managed by reducing pelvic volume (e.g., with a pelvic binder or external fixator).

Pelvic binders should be centered directly over the greater trochanters to effectively close the pelvic ring, generate appropriate compressive vectors, and avoid excessive pressure on the abdomen or inadequate reduction seen with higher placements (e.g., over the iliac crests).

Resnick's criteria for DISH include: flowing ossification of at least 4 contiguous vertebral bodies (bridging 3 intervertebral disc spaces), preservation of disc height, and the absence of apophyseal joint ankylosis or sacroiliac erosion.

To effectively reduce pelvic volume in open-book (APC) pelvic ring injuries, a pelvic binder or sheet must be centered squarely over the greater trochanters of the femurs. Placement over the iliac crests is a common error that can actually force the pelvis into further outward rotation or fail to adequately close the posterior pelvic ring, exacerbating hemorrhage.

Optimal placement of a pelvic binder is centered directly over the greater trochanters. Placing the binder too high (e.g., iliac crests or ASIS) reduces its biomechanical efficacy in closing the pelvic volume and can paradoxically open the true pelvis further.

In the Young-Burgess classification, an APC-II injury is characterized by symphyseal diastasis and disruption of the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments, but the posterior sacroiliac ligaments remain intact (rotationally unstable, vertically stable). An APC-III injury involves complete disruption of both the anterior AND posterior sacroiliac ligaments, rendering the hemipelvis both rotationally and vertically unstable.

Pelvic binders should be centered over the greater trochanters to effectively close the pelvic ring and reduce pelvic volume. Placement over the iliac crests or ASIS can paradoxically widen the true pelvis or fail to achieve adequate reduction in an open-book pelvic injury.

In the Young-Burgess classification, APC I involves symphysis widening <2.5 cm with intact posterior ligaments. APC II involves symphysis widening >2.5 cm, disruption of the anterior sacroiliac, sacrospinous, and sacrotuberous ligaments, but the critical posterior sacroiliac (SI) ligaments remain intact (rotationally unstable, vertically stable). APC III indicates complete disruption of the anterior SI, sacrospinous, sacrotuberous, AND the posterior SI ligaments, resulting in a completely unstable hemipelvis (both rotationally and vertically).

An APC III pelvic injury involves complete disruption of both the anterior and posterior pelvic rings. This includes the symphysis pubis anteriorly, and all of the posterior ligamentous structures: the anterior sacroiliac ligaments, the pelvic floor ligaments (sacrospinous and sacrotuberous), and the strong posterior sacroiliac ligaments, leading to complete global instability of the hemipelvis.

The Young-Burgess classification describes the mechanism of injury for pelvic fractures. Anteroposterior Compression II (APC II) injuries are characterized by symphyseal diastasis > 2.5 cm with tearing of the anterior SI ligaments, sacrotuberous, and sacrospinous ligaments. Crucially, the posterior SI ligaments are intact, meaning the hemipelvis is rotationally unstable but vertically stable. APC III involves complete disruption of both anterior and posterior SI ligaments, resulting in both rotational and vertical instability.

This patient has an Anteroposterior Compression Type III (APC III) pelvic ring injury and is in hemorrhagic shock. In a hemodynamically unstable patient with a pelvic ring injury and a negative FAST (ruling out massive intra-abdominal hemorrhage), the source of bleeding is presumed to be the pelvis (often venous or cancellous bone, though arterial bleeding can occur). Preperitoneal pelvic packing or angioembolization (depending on institutional protocol and immediate availability) are the appropriate next steps after mechanical stabilization with a binder. Exploratory laparotomy is incorrect as the FAST is negative.

To be effective in reducing pelvic volume and closing an open-book pelvic injury, a pelvic binder (or sheet) must be centered low, directly over the greater trochanters. Positioning it too high over the iliac crests can actually worsen the deformity by acting as a fulcrum. Its primary mechanism of action is reducing pelvic volume to encourage tamponade of the massive venous plexus bleeding, not arterial bleeding.

The patient has an Anterior-Posterior Compression (APC) Type II pelvic ring injury. In pelvic trauma, roughly 80-90% of life-threatening hemorrhage is venous in origin, most commonly from the presacral and prevesical venous plexuses. While arterial bleeding (e.g., superior gluteal, internal pudendal) can occur and is often more rapidly fatal if present (particularly in severe APC III or highly displaced vertical shear/lateral compression patterns), the overall most common source of severe bleeding across pelvic ring disruptions is the venous plexus.

The Young-Burgess classification divides anteroposterior compression (APC) injuries into three types. APC I: symphysis widening <2.5 cm with intact SI ligaments. APC II: symphysis widening >2.5 cm with disruption of the anterior SI, sacrotuberous, and sacrospinous ligaments, but INTACT posterior SI ligaments (rotationally unstable, vertically stable). APC III involves complete disruption of anterior and posterior SI ligaments.