Chapter 15. Pelvic bone fractures

Injuries of the pelvis and pelvic organs are classified as the most severe category of traumas. The incidence of pelvic fractures in relation to the total number of injuries ranges from 5 to 15%. The deep location of the most bone frame under powerful muscle masses creates objective difficulties for the diagnosis and treatment of injuries of this localization, as evidenced by the frequency of discrepancies between clinical and pathological diagnoses, which is 42-54%.

The mortality rate for pelvic bone fractures is about 10% with isolated injuries and reaches 60-80% with combined and multiple traumas including pelvic damages. The cause of death of more than half of the victims is shock, which is noted in 93% of sufferers with fractures of the pelvic bones upon admission to the hospital. With closed pelvic injuries in 25-30%, massive bleeding occurs in the surrounding tissues, exceeding 2 liters. In 25-45% of cases, fractures of the pelvic bones are combined with damage to other bones or internal organs.

Anatomical and biomechanical features

Both pelvic, or innominate, bones, connecting with one another and the sacrum, form a bony ring - the pelvis, which serves to connect the body with the free lower limbs and at the same time surrounds the cavity containing the viscera (protection of the pelvic organs).

The pelvic ring can be divided into two semi-rings relative to the acetabulum -posterior and anterior.

Posterior semi-ring is positioned behind the articular surface of the acetabulum. It includes the sacrum, the sacroiliac joints with ligaments, and the posterior ilium. This loaded part of the pelvic ring provides load transmission along the axis of the skeleton to the lower extremities.

Anterior semi-ring is located anteriorly from the articular surface of the acetabulum. It includes branches of the pubic bones and symphysis.

Pelvic stability depends primarily on the weight-bearing posterior semi-ring, as well as the sacroiliac complex, which includes sacroiliac joints, the major sacroiliac, sacrotuberous and sacrospinous ligaments, and the muscles and fascia of the pelvic floor. Strong dorsal sacroiliac ligaments maintain normal position of the sacrum in the pelvic ring. Sacrospinous ligaments oppose the external rotation of the pelvic semi-ring, while the sacrospinous ligaments oppose rotational forces in the sagittal plane.

The main forces acting on the pelvic ring are outward rotation, inward rotation and vertical shear forces. Each of these forces results in different types of pelvic fractures.

Pelvic injuries are quite diverse. Common to them, as a rule, is the application of significant force to obtain such an injury. The pelvic area is richly innervated and supplied with blood, therefore, with injuries, there is a high probability of acute blood loss and the development of hypovolemic shock (pelvis is a "shockogenic zone"). Shock is especially severe with simultaneous disruption of the continuity of the anterior and posterior semi-rings with extensive destruction of the spongy bone, since in these cases, in addition to the pain component caused by irritation of the rich reflexogenic zone, there is always a significant hemorrhage in the intrapelvic tissue, which can reach 2.0-2.5 liters.

Classification and mechanism of damage

According to UFC, the group of fractures of the pelvic bones also includes fractures of the acetabulum. However, the specificity of acetabular injuries, the peculiarities of diagnosis and treatment, led to the creation of independent classifications for these fractures.

Injuries to the pelvic bones are divided into three types:

• type A - marginal (stable) fractures of the pelvic ring without breaking its discontinuity;
• type B - vertically stable but rotationally unstable fractures with discontinuity of the pelvic ring in its anterior section (fractures of the pubic and ischial bones, ruptures of the symphysis). The posterior ligaments of the pelvis and pelvic floor remain intact, which protects against vertical displacements, but functional blockade of the sacroiliac joint is quite common;
• type C - rotationally and vertically unstable fractures with discontinuity of the pelvic ring in its anterior and posterior parts.

Separately, it is worth dwelling on some groups of fractures.

Saddle-horn fracture

One- or two-sided fractures of the branches of the pubic bone are classified as type A. Despite the fracture of two bones at once, the integrity of the pelvic ring is not broken, since the sciatic bones are not damaged.

Fractures of type B1 ("open book")

The traumatic force is directed in the sagittal plane with outward rotation (a typical situation - the pelvis is compressed in the anteroposterior direction), which leads to rupture of the pubic symphysis and rotational displacement of the pelvic bones, which "open" like a book. If the divergence of the pubic articulation is less than 2.0-2.5 cm, the sacroiliac joint does not rupture; if the symphysis is "open" by more than 2.5 cm, there is a rupture of the sacrospinous and anterior sacroiliac ligaments.

Fractures of type B2 ("closed book")

The traumatic force is directed in the frontal plane with inward rotation (in a typical situation, the pelvis is compressed from the sides), which leads to damage to the sacroiliac complex with a compression fracture of the anterior part of the sacrum and a fracture of the pubic and ischial bones on the same name (unilateral type) or on the opposite (contralateral type) to the side with internal rotation of the pelvis, which "closes" like a book. The remaining intact pelvic floor ligaments and the pelvic diaphragm maintain vertical stability, preventing displacements in this direction.

Fractures of type C

Rotational and vertical instability is caused by complete damage to both the anterior and posterior pelvic semi-rings with rupture of the pelvic diaphragm. Such fractures are both unilateral and bilateral. In other classifications, such injuries are called Malgaigne-type fractures (by the name of the author who described them). Severe instability leads not only to rotational displacements but also to a vertical shift: the damaged half of the pelvis is displaced upward (Fig. 15.1).