Pelvic Fractures – Low Energy

The pelvis is made up of 2 bones, joined at the front where the joint is called the pubic symphysis, and at the back it joins the sacrum (bottom of the spine) at the sacro-iliac joints. It is important for many things – the hip sockets are part of the pelvis, the spine attaches to the lower limbs via the pelvis, and within the pelvic bones are many organs such as the lower bowels and the bladder.


Pelvic fractures typically fall into 2 groups, which we arbitrarily classify as low or high energy fractures. In general, a low energy fracture is one caused by a fall from standing height or less, and occurs most commonly due to poor bone quality (eg osteoporosis). At times pelvic fractures can occur in poor bone even without a fall, and therefore this group of patients is typically elderly.

High energy fractures by contrast typically occur in younger patients, and involve significant mechanisms such as road traffic accidents, sports injuries or falls from a height. In this group there are often multiple injuries, and this can be life-threatening.

This section only refers to low energy pelvic fractures.

Normal parts of the pelvis



Low energy pelvic fractures most commonly occur as a result of a simple fall. Most people have fallen to one side, and the pelvis cracks as it is forced together from side to side. The pelvis functions mechanically as a ring, and so fractures nearly always occur in 2 places at the same time. This is usually at the front (the ramus fractures) and at the back (the sacrum fractures).

The injury is hard to distinguish from a hip fracture at first, as they both happen from a fall in elderly / osteoporotic patients, and both result in pain and inability to walk or stand. However X-rays or CT scans will always show the diagnosis.


There is a particular form of pelvic fracture called a fatigue fracture, which happens without any fall or specific event. When we walk there are large forces passing through the pelvis. In patients where the bone quality is very poor, sometimes these forces can become too much for the pelvic bone to withstand, and a “slow” fracture occurs. Pain often comes on over a matter of days or weeks, and builds with time.



A broken pelvis causes significant pain, and usually makes walking difficult or impossible. Whilst lying still in bed can be tolerable, often even moving from side to side in bed can be very painful. The location of the pain varies depending on the site of the fractures, but typically anterior rami fractures cause pain in the groin, and posterior sacral fractures cause low back pain. Unlike with high energy pelvic fractures, nerve symptoms or problems with bowel or bladder function are rare in this group of injuries.



To diagnose a broken pelvis, your doctor will ask you questions about how you injured the area, and will examine your hips and legs. Simple x-rays will often show this fracture, but at times a CT scan may be needed to make the diagnosis. A CT scan is almost always done even if the xray shows the diagnosis – the pelvis has such a complicated shape that the information added by a CT scan is useful for clarification of the fractures as well as planning treatment.



On the left is a normal pelvic Xray. The pelvis on the right has fractures running through the rami on the left side (the right as we look at it). There is also a fracture through the sacrum in this case, but it is very difficult to see without a CT scan.



It is important to note that these fractures (and especially the fatigue fractures) tend to happen in patients with poor bone quality. Part of the treatment of this injury is to assess the bone quality  and look for other medical conditions that might affect bone. Most commonly a physician will be involved at this stage, and investigations will include a full blood screen looking at many things, but including liver function, kidney and thyroid function, calcium levels, Vitamin D levels and general nutrition. All of these areas will need to be corrected to allow any fractures to heal.


Many of these fractures can be treated without surgery – this means adequate pain relief and help with mobility. In simple cases this can mean just using a walking stick for a few weeks, whereas more painful cases may need a period of time in hospital, stronger pain relief, physiotherapy and a walking frame. One of the difficulties with this fracture is that it interferes with mobility in what is typically an elderly patient, and so coping at home can be challenging.

The acute pain lasts for a few weeks, but usually improves significantly after the first 10 days; by 8-12 weeks most patients are back to being nearly pain free.

The fracture seen above has now healed, with complete bone bridging the fracture gaps.

There are times when the pain caused by the fracture is intolerable, and mobilization impossible. If patients are unable to get out of bed because of the pain, especially after 2-3 days, then surgery may be an option. Similarly, if the fracture ends happen to be far apart (and so less likely to heal), or in cases of fatigue fractures, then surgery is often discussed as an option.



If surgery is required, then the aim of this is to hold the fractures still, enabling the patient to mobilise whilst the fractures heal. The surgery itself does not make the fractures heal – this still takes several weeks and happens naturally.

The most common operation that is performed for low energy pelvic fractures involves passing long screws across the fractures. This is done using a “percutaneous” technique – that means that it is done through very small cuts (1cm or so) and using Xray in the operating theatre to place the screws. This minimally invasive surgery therefore has very little risk of causing bleeding or further pain after surgery, but the stability afforded by the long screws usually results in significantly less pain for the patient by the next day.


This pelvic fracture has been fixed with 4 long screws, controlling pain and allowing easier mobility.


Rehabilitation / return to function


Whether treated surgically or not, low energy pelvic fractures tend to heal well over a period of several weeks. Bony healing is usually seen to be complete by 3-4 months on x-rays. During this healing time however, most patients find mobility difficult, and as a result do little exercise; muscles waste away and elderly patients lose confidence in their ability to do things. Whilst the fractures themselves heal fairly rapidly, full recovery from this injury can take up to a year, and often requires support from family members, and input from physiotherapists / carers. Patients can lose a level of independence permanently, or require walking aids in the long term, and often require more help at home.


Longer term issues

Other than the issues mentioned above, the only other complication seen from this fracture is if they fail to heal – fracture non-union. This is uncommon, and affects less than 5% of cases. It typically happens in cases where non-operative management has been tried – although no specific cause for non-healing is usually apparent, if the original fracture resulted in the bone ends being far apart then it is more likely. The options in this situation are to leave things alone and accept the resultant symptoms / limitations, or consider surgical fixation after non-healing becomes apparent. In these uncommon cases, surgery is more complex as the bones are often displaced, and so more significant open surgery is required.