Fracture of the pelvis is a relatively uncommon but potentially devastating injury.
It is important to establish the exact type of fracture, as a return to full athletic use may be possible in certain situations. Obtaining an accurate diagnosis is critical for managing the horse during recovery and determining his chances of returning to work.
One of the most common causes of fracture is trauma, such as a kick or fall, or from walking into a doorframe. The second common type is a stress fracture as a result of repetitive strain from exercise.
Important clues that a horse may have fractured his pelvis can often be found in his recent history.
A horse that slides with his hindlimbs underneath himself and falls over, landing on his bottom, is at risk of fracturing the prominence either side of the tail head (the tuber ischium). Knocking a hip while walking through a doorway may fracture the bony prominence at the sides of the pelvis (the tuber coxae).
With complete fractures, lameness is usually severe from the outset and distress may be quite marked. The horse will probably be reluctant to bear any weight on the limb on the affected side and may suffer local muscle spasm (known as “guarding”, which protects the site).
In the rare event of bilateral fracture (both sides), the horse will struggle to stay standing due to a complete break in continuity of the load-bearing skeleton.
In the case of fracture of a bony prominence (tuber coxae or tuber ischium), a depression where this prominence should be located can often be seen on inspection. Due to the size and visually prominent location of the tuber coxae, these fractures are more obvious and are often recognised sooner. Initial swelling due to bleeding at the site, along with muscle spasm, however, may mask this for the first few days.
Following complete fractures of the wings or shaft of the ilium (see diagram, above), there is often a gradual but progressive movement of the bones, resulting in the bony prominences becoming displaced. This results in asymmetry of the pelvis when the horse is stood square.
In racehorses, stress fractures of the pelvis are quite common as a result of the repetitive strain of training. These typically affect the wing, then the shaft, of the ilium. Such fractures start off incomplete, as the bone fails to adapt to the forces being applied during exercise. Lameness is often transient and mild, if present at all.
With continued exercise the fracture becomes progressively more severe, until the bone eventually fails completely. The resulting displaced fracture (with a gap between the ends of the bone) causes acute and severe lameness, along with the typical signs described earlier.
Spotting signs
Careful clinical examination is often sufficient for diagnosis.
Displaced or depressed bony prominences are characteristic. Swelling often develops in the overlying muscles due to bleeding at the fracture site, although this may take a couple of days to become noticeable. With more severe haemorrhage, this can be seen sooner and often gravitates into
the thigh muscles.
Internal (rectal) palpation can enable identification of some fractures.
Due to the pelvis of the adult horse being enveloped in large muscle masses, it is impossible to X-ray the area comprehensively. Although X-rays of some parts of the pelvis can be obtained, high exposures are needed, which carry risk to veterinary staff.
General anaesthesia is often necessary for examination of the hip and more central parts of the pelvis. A horse with a suspected fracture is at substantial risk, however, as he struggles to stand after anaesthesia.
Because of the limitations of X-ray, ultrasound has become the first option for imaging and defining fractures of the pelvis. Ultrasound is reflected by bone surfaces, enabling examination of the bone contours and the identification of any breaks in bone surface continuity (pictured, below right).
When fractures are incomplete and there is no displacement, ultrasound may not be able to detect any abnormalities. Here, scintigraphy (bone scan) is an invaluable tool.
A low-dose radioactive dye injected into the area is taken up where there is more intense bone activity, creating “hot spots” that are visible with a specific camera.
Rest and rehab
With severe fractures, bleeding from the major blood vessels that cross through the pelvis can be
life-threatening.
Because of this, when such an injury is suspected, the horse should be cross-tied in a stable.
The simple act of getting up or lying down may be enough to worsen the fracture sufficiently to lacerate the blood vessels.
A horse with such a major injury may need to be cross-tied (pictured, below) for up to a month and box-rested for a further month. Walking exercise can then resume, with restricted turnout introduced a month or two later.
Successful treatment of stress fractures is greatly enhanced by obtaining an early diagnosis, before the fracture becomes complete. The horse is then given a period of rest followed by a gradual reintroduction to work (typically taking two to three months).
Other than rest and restriction, there are limited treatment options for pelvic fractures. Due to the horse’s size and weight, surgical repair is rarely possible.
Pain relief is an extremely important part of injury management, to keep the horse comfortable and to prevent overloading of the opposite limb with the associated risks of laminitis.
Incomplete fractures usually heal well and a full return to work is expected. While a permanent alteration to the horse’s skeletal structure (and shape) is expected with fractures of the bony prominences, many horses are still able to resume work.
Complete fractures of the wings or shaft of the ilium carry a more guarded prognosis, although this depends on the extent of displacement and the severity of the fracture. If the hip joint is involved, permanent lameness to some degree would be expected.
For future breeding activities, careful examination of the birth canal should be performed — although surprisingly few pelvic fractures lead to future foaling problems.
‘An exploratory scan revealed a fracture’
Soreness behind the saddle was the first sign last year that eventer Livingstone II had pelvic problems. When regular physio sessions produced no long-lasting suppleness and looseness, the big-moving 17hh gelding was sent for an exploratory bone scan.
“The scan revealed a pelvic stress fracture,” says Will Furlong, who rides “Henry” for Ingrams Eventing. “After two months of walking in-hand, he was brought back to fitness for the start of the season.
“He had never showed signs of lameness and had been going really well at the time,” adds Will, who has since ridden Henry to individual and team gold at the young rider European Championships in 2015. “We were lucky it was picked up — if it had got worse, it could have broken.”
Ref Horse & Hound; 18 August 2016