The pelvis is a ring of bone at hip level, made up of several separate bones. A pelvic fracture is a break in any one of those bones. Some pelvic fractures involve breaking more than one of the bones; these can be more serious as the bones are more likely to slip out of line.
What is a pelvic fracture?
A pelvic fracture is a break in any of the bones that make up the pelvis. The pelvis is a ring of bones in a bowl shape that attach the legs to the trunk. (See picture below). The shape of the pelvis means that it protects organs which sit inside it (the bladder, the womb and ovaries, parts of the bowel) so sometimes fractures of the pelvis can also lead to injuries of one or more of these organs.
How serious is a pelvic fracture?
The seriousness of a pelvic fracture depends on how many bones are broken and how badly, and on what injuries may have occurred to the organs inside the pelvis. Pelvic fractures therefore range in severity from fairly minor to life-threatening.
Anatomy of the pelvis
The term 'pelvis' is sometimes used to describe the lower part of the abdomen from the iliac crest (see diagram) downwards. In women, this pelvic cavity contains the womb and ovaries as well as the bladder and lower part of the bowel.
This cavity is enclosed in a ring made up of several bones, with the lower end of the spine (sacrum and coccyx) at the back. It is sometimes also called the pelvic girdle.
Types of pelvic fracture
Because the pelvis is a ring of bones, when forceful injury causes a fracture in one part of the structure, there can be a matching fracture at the opposite point in the ring. There are several common patterns, which depend upon the direction and severity of the trauma.
Stable and unstable fractures
Perhaps the most important way of classifying pelvic fractures is into stable or unstable fractures. The majority of pelvic fractures are stable.
Stable fracture: the broken bones are still properly lined up, so that the ring has kept its shape. Usually only one bone is affected, with a single fracture.
Common fracture patterns include:
- Breaks across the top of one ilium.
- Cracks to the pubic ramus on one side.
- Cracks in the sacrum.
In each of these cases the other bones are intact and will keep the bony ring of the pelvis together.
Pelvic avulsion fractures (in which a fragment of bone is broken off by the pull of a muscle) and pelvic stress fractures (hairline cracks which do not extend all the way across the bone) are also types of stable pelvic fractures.
Unstable fracture: this usually occurs when there are two or more breaks in the pelvic ring and the ends of the broken bones move apart. This type of fracture is more likely to occur after high-impact injury and there may, therefore, be other associated injuries.
These injuries involve much more bleeding than stable fractures, as the separation of the broken bones allows them to bleed much more freely. They may also involve direct damage to the internal organs.
There are some typical patterns of unstable fractures. These include 'open book' fractures, when the pelvis is broken at the front and the back by severe force from the front (for example, in a significant road traffic accident) and lateral (or sideways) force fractures which often fracture the pubic rami and the sacroiliac joints, sometimes also involving the hip socket.
Open and closed fractures
Pelvic fractures, whether stable or unstable, can also be divided into 'open' fractures, in which injuries to the skin mean that the broken bones are visible, or 'closed' fractures, in which the skin is not broken. Open fractures are more serious because infection can easily reach the wound, which may already be contaminated from the injury.
Causes of pelvic fractures
Major pelvic fractures are caused by major trauma such as:
- Road traffic accidents.
- Crush injuries (for example, being run over by a car or rolled on by a horse).
- Falls from a height.
Pelvic fractures caused by high-force or high-speed injuries are often unstable and they need urgent hospital treatment.
Less severe fractures which involve undisplaced fractures can occur after falls or trips, particularly if the bones are 'thin' (osteoporosis). For this reason painful but stable fractures are more common in elderly people who tend to have 'thinner' bones, and who are sometimes prone to falls.
Causes of pelvic avulsion fractures
A pelvic avulsion fracture occurs when the tendon of a muscle comes away from the bone, taking a small chip of bone with it. This most commonly occurs at bottom of the ischium where the big hamstring muscles are attached, or on the front of the ilium where one of the large quadriceps muscles attaches.
These types of fractures typically occur during sports that involve speed and sudden stops, particularly in young people who are still growing. Examples are:
- Football (particularly miskicks that hit the ground).
A pelvic avulsion fracture may also be caused by a car accident.
Causes of pelvic stress fractures
Pelvic stress fractures are caused by repeated stresses to the bone, usually due to sport. They usually affect the pubic bone and cause exercise-related pain which gets gradually worse, but they do not usually prevent exercise.
Sports involving repeated impact, such as running or jumping, carry the highest risk. Stress fractures often occur in those who suddenly increase their training distance or activity level, including sedentary people who suddenly start to exercise.
They are uncommon in the pelvis, although more common in women and those with 'thinning' of the bones (osteoporosis).
How common are pelvic fractures?
Significant pelvic fractures can occur in anyone who experiences a major trauma. Less severe, stable fractures are most commonly seen in elderly people, particularly those with 'thinner' bones (osteoporosis).
Avulsion fractures are particularly common in sporty teenagers. Stress fractures are typically seen in runners, although they more commonly affect other sites than the pelvis.
Symptoms of stable pelvic fractures
A stable pelvic fracture is usually painful. Pain in the hip or groin is usual and is made worse by moving the hip or trying to walk, although walking may still be possible. Some patients find if they try to keep one hip or knee bent this can ease the pain.
Other symptoms will vary with the severity of the fracture. They may include:
- Pain and tenderness in the groin, hip, lower back, buttock or pelvis.
- Bruising and swelling over the pelvic bones.
- Numbness or tingling in the genital area or in the upper thighs.
- Pain which may also be present on sitting or straining.
There may be visible signs of bleeding. Bleeding can track out to the skin in several places, some of which are more likely to be visible than others. They include:
- Bruising over the pelvic bones themselves.
- Bruising or a tender lump in the groin or on the perineum.
- Bruising in the small of the back.
- Vaginal bleeding in women and bruising to the scrotum in men.
- Blood in the urine or coming from the back passage.
Symptoms of unstable pelvic fractures
Major and unstable pelvic fractures
Major and unstable pelvic fractures are likely to cause severe pain and shock (loss of significant volume of blood, sufficient to cause serious symptoms or even death).
Pain may be in the pelvis, groin, back, tummy (abdomen), or down the legs.
The pelvic bones are large and have a rich blood supply, so when broken they will bleed heavily and the bleeding will not stop quickly. Whilst the blood may not be visible, because it is on the inside of your tummy, this level of blood loss will cause a sudden drop in your blood pressure. Affected people will be pale, clammy and seriously unwell, perhaps even unconscious.
It is sometimes possible to move around and attempt to walk immediately after a major unstable pelvic fracture - particularly after road accidents. This is because the extra adrenaline released after an accident can initially reduce or prevent feelings of pain.
Pelvic avulsion fractures
Pelvic avulsion fractures are mainly seen in young, active sportspeople who are still growing. Symptoms are usually of sudden pain during a sudden powerful movement. The pain is often in the bottom, in the crease of the buttock, or at the bony part on the front of the hip. Afterwards the athlete will feel weakness and pain when doing the movements which use the affected tendon and muscle. Bruising and swelling are likely.
Pelvic stress fractures
Stress fractures - where there is a fine crack in the bone which does not extend all the way through - are one of the mildest sorts of stable fracture. Stress fractures of the pelvis are easy to miss as the pain may be quite hard to locate. Symptoms typically consist of a dull pain that is difficult to localise at first. This may get better as exercise continues but be worse afterwards.
How are pelvic fractures diagnosed?
In the case of major injuries, such as road traffic accidents, where pelvic fracture is likely and must be excluded, X-rays will be performed urgently to assess the state of the pelvic bones. A pelvic fracture is also suspected if there has been a lesser injury but there is pelvic bone tenderness, difficulty walking or any loss of sensation in the lower part of the body.
An X-ray will show most pelvic bone injuries, although it will not show details of injuries to organs inside the pelvis. X-rays provide images of bones and in the case of the pelvis, they are usually taken from a number of different angles, so that doctors can check whether (and how much) the bones are out of line.
A computerised tomography (CT) scan involves multiple X-rays in 'slices' down through the pelvis in order to build up a three-dimensional image of the injuries. This will be done in complicated cases to get a better picture of the fractures and to look for associated injuries.
A magnetic resonance image (MRI) scan is an alternative to CT and may give a clearer picture of damage. This is not usually necessary, except in the case of stress fractures, which can show up well on MRI scanning but which.
Ultrasound scans and contrast studies (where a radioactive dye is injected to create pictures to enable doctors to check on internal organs and structures) may be needed to assess internal organs.
Radioisotope bone scans are sometimes used to look for stress fractures, particularly in patients who cannot have an MRI scan (for example, if they have a pacemaker).
If the fracture happened unusually easily, and there is a possibility that there is underlying 'thinning' of the bones (osteoporosis), a bone scan might be suggested to check the bone density. This scan is called dual-energy X-ray absorptiometry (DXA - formerly DEXA).
Other investigations may include blood tests to assess the degree of blood loss and the function of the liver and kidneys, and testing of the urine to look for damage to the bladder.
How are pelvic fractures treated?
With an unstable pelvic fracture the treatment will depend on the location of the fractures, and on any other injuries that might have been sustained (for example, fractures of bones in the legs). The main aims of treatment of an unstable pelvic fracture are first to stabilise the pelvis and prevent further blood loss, then to keep the bones still to allow healing.
First aid in pelvic fracture
Any person with a suspected pelvic fracture should be kept warm (eg, covering with a jacket) and should not be moved by non-trained personnel, especially if there is severe pain, until help arrives.
The first person to arrive at a serious road accident should ask people to sit still if they are walking around. It is useful to ask if there is any pain anywhere, particularly in the chest, tummy (abdomen) or hips. If there is pain anywhere near the pelvis they could have a major pelvic fracture, and it should be assumed that they are seriously injured. It is best to keep them still and warm until emergency services arrive.
Treatment of blood loss
Reduction in bleeding from the pelvis is initially helped by keeping the pelvis as stable as possible. Initially this is done by binders and sheets, followed by stabilisation using external fixation (see below).
External pelvic fixation
This involves long screws inserted into the bones from the sides and a large external frame. It is done in the operating theatre, under anaesthetic. It helps prevent further blood loss by holding the bones together.
The metal pins or screws are inserted into the bones through small incisions into the skin and muscle. They project out of the skin on both sides of the pelvis where they are attached to carbon fibre bars. The external fixator acts as a stabilising frame to hold the bones in proper position.
This involves a pulley system of external pins in the bones, with weights and counterweights. It helps line up the pieces of bone. Skeletal traction is sometimes used as a temporary treatment, and it often provides some pain relief. Occasionally, pelvic fractures are treated with skeletal traction alone but this is unusual.
Internal pelvic fixation
Some patients require internal fixation to keep the bones in place. This is open surgery, performed under anaesthetic. The bone fragments are repositioned, then held together with screws or metal plates which are left permanently in place.
Getting the pelvis fixed and stable is very important both for pain control and for the long-term results of your treatment. It is more likely to be necessary if there are multiple fractures.
Management of pain
Pain is managed using painkillers and by stabilising an unstable pelvis. Strong painkillers and local anaesthetics may initially be needed. An epidural anaesthetic is sometimes used to help manage the initial pain.
Doctors usually prescribe 'blood thinners' (anticoagulants) to reduce the risk of blood clots forming in the veins of the legs and pelvis. Pelvic fractures are known to increase the risk of blood clots.
Initial treatment is with pain relief and bed rest, followed by mobilisation. It is very important to get moving as soon as possible, as this is better for long-term recovery, as well as reducing the risk of blood clots forming (deep vein thrombosis).
However, crutches or a walker may be needed for several weeks, depending on the severity of the injury, until the bones are fully healed.
Physiotherapists can be helpful to try to provide exercises to maintain muscle strength and joint mobility unable to weight bear or whilst less mobile than normal.
Treatment for other pelvic fractures
Stable pelvic fracture treatment
With a stable fracture, the most common treatment is bed rest and painkillers.
Surgical treatment is not usually needed for stable fractures. Crutches and walking aids may occasionally be used as part of the recovery, and physiotherapy will often be useful.
Pelvic avulsion fracture treatment
Treatment of pelvic avulsion fractures is with rest. These fractures usually heal by themselves over 4-6 weeks. Initially, applying ice can help pain and inflammation.
Occasionally, surgery is needed to re-attach the bone and tendon to the pelvis; however, this is mainly reserved for unusually large avulsion fractures.
Following the rest period, a gradual rehabilitation programme can be commenced which aims to regain full strength and movement at the hip.
Pelvic stress fractures treatment
Pelvic stress fractures can cause lingering, worsening pain and may become full-thickness fractures, so rest from the activity which caused them is very important. A gradual reintroduction to running can begin after a few weeks, once the athlete is pain-free.
Some specialists now suggest treatment with an infusion of pamidronate, a drug more commonly used to treat 'thinning' of the bones (osteoporosis). This treatment appears to be fairly effective in speeding the healing of stress fractures, even in patients without osteoporosis.
What is the outlook for a pelvic fracture?
Most people who experience pelvic fracture regain full mobility. Recovery will be quicker if the fracture is less severe and in someone who is younger and fitter or who has healthy active muscles. Sometimes, major pelvic fracture can affect mobility in the long term.
Dr Mary Lowth is an author or the original author of this leaflet.
Further reading and references
Coccolini F, Stahel PF, Montori G, et al; Pelvic trauma: WSES classification and guidelines. World J Emerg Surg. 2017 Jan 1812:5. doi: 10.1186/s13017-017-0117-6. eCollection 2017.