What types of fractures can occur?
These injuries occur in younger people and are not common. They are often the result of sports as the patient makes an extra effort in a situation of mechanical disadvantage. Thus trying to spring up, straightening the knee when the load is suddenly increased may result in a pull-off fracture of the site of origin of rectus femoris, one of the muscles that straightens the knee. This point of attachment is the anterior inferior iliac spine in the groin. Avulsion fracture of the hamstring origin (the ischial tuberosity) is less common; a ruptured hamstring muscle occurs more frequently. These injuries generally heal without the need for surgery.
Fragility Fractures of the Pelvis
In osteoporotic elderly patients, a fall compressing the pelvis may result in a fracture through the pubic rami. Both rami on one side are usually broken but this is an exception to the rule about a ring only breaking in one place. Although it must be looked for, it is uncommon for there to be significant disruption of the sacro-iliac complex posteriorly in these cases. These fractures are painful and limit mobility but they generally heal without the need for intervention. Their major significance is as an indication of generalized osteoporosis and an increased risk of fracture elsewhere. These are probably the most common fractures of the pelvis.
Bilateral Pubic Rami Fractures
This pattern of fracture involves breaks of both pubic rami on both sides. It is the result of a direct blow to the pubic region of the pelvis. This may occur in a variety of accidents or collisions. Injury to the bladder is common especially if it was full at the time of impact. The fractures may be displaced a few centimeters but do not need reduction and usually heal without intervention.
Fractures of the Iliac Wing
An impact from the side or directly onto the crest of the pelvis may cause a fracture of the wing of the ilium. This usually affects only one side and does not always break the ring. This fracture has a bad reputation for bleeding and may need surgery on this account, but it does not usually require intervention to heal the fracture. Even if the shape of the iliac wing is not restored exactly there is very little long term effect on function.
Vertical Shear Fractures
Vertical shear fractures occur with motor vehicle accidents and other forms of high energy trauma.The force that causes this type of fracture is applied to one side of the pelvis only. An example might be falling from a height and landing on one leg. The pelvis on that side may be driven upwards and the other side is driven downwards by the momentum of the upper body. The fracture line commonly goes through the pubic rami and posterior sacroiliac complex on the same side. It is most important to establish the stability of this type of fracture. If the posterior disruption is complete the fracture is unstable and one half of the pelvis is likely to migrate upwards relative to the other side. This injury also may disrupt the nerves that pass over the wing of the sacrum and there is a high incidence of injury to the internal organs with this type of fracture.
Lateral Compression Injuries
If the ring of the pelvis is compressed forcefully from the side it may break through the pubic rami at the front and the sacroiliac complex at the back. The two components of the break may be on different sides. If the posterior component is through bone, the injury is unstable and may need to be fixed. However, if only the posterior ilio-sacral ligaments are torn, the fracture may be stable enough to be treated non-operatively.
Sometimes called open book injuries these occur when the legs are forced wide apart pulling on the pelvic ring in the front. If the pull is too great there is a spectrum of damage. The lowest grade results in disruption (called diastasis) of the pubic symphysis. If this is less than 2 cms it is usually stable and may not need to be reduced or stabilized. At the next level of injury the pubic symphysis is pulled apart more widely and there is also partial damage to the posterior sacroiliac complex. This injury is potentially unstable and needs to be treated by some method to "close the book" - meaning to pull and hold the ring of the pelvis back together in the front.
The most severe type of injury results in complete disruption of the posterior structures as well as wide separation of the pubic symphysis. This is definitely unstable and needs surgery to close the pubic symphysis and stabilize the pelvic ring posteriorly. Straddle injuries occur in riding accidents as well as motor vehicle accidents and other high energy trauma. The urethra is quite commonly injured in straddle injuries as it is so close to the pubic symphysis.
Fractures of the pelvis that involve the hip socket (acetabulum) are amongst the most challenging of all fractures to treat. They are rare, variable, demand meticulous assessment, require complex surgical treatment and have major consequences for long term disability. For these reasons patients with acetablular fractures are often transfered to a tertiary trauma center where the treating team has experience managing these injuries. These fractures usually occur as a result of severe forces transmitted through the legs, motor vehicle accidents, or falls from a height.
Dislocations of the hip joint can push off fragments of the rim of the socket or the head of the femur can be driven up into the pelvis. Because of the importance of the hip as a weight bearing joint it is recommended to restore the joint surface to smoothness as exactly as possible. This usually means surgery - often requiring a very extensive exposure to reduce all the pieces. The force required to cause this injury means that other injuries are common and may be life-threatening, so the decision to undertake surgery is a complicated one.