Cast in stall, hitting gates or doorways, road traffic accidents.
Race training: fatigue failure of bone or stress fractures:
Accumulated bone microdamage induced by repetitive loading.
Leads to disturbance in remodeling and frank stress fracture.
Pre-existing fracture may displace acutely with further strenuous activity or trauma: evidence of pre-existing pathology may be present in pelvic bone asymmetry, muscle atrophy of the hindquarters and spasm or tenderness on palpation of the gluteal muscles prior to the acute fracture.
Tarsal valgus conformation and increased coxal angle have been reported as predisposing factors.
Ilial wing is the most common site for pelvic fractures in the Thoroughbred racehorse. Single fractures are more common with other fractures in order of occurrence are ischium, ilial shaft and acetabulum. When two fractures are present, the most common are bilateral ilial wings and unilateral ilial wing and shaft together.
Tuber coxae is the most prominent part of the pelvis and most vulnerable to external impact trauma causing fractures.
Fractures of the pubis and sacrum are rare:
Fractures of the pubis and shaft of the ischium can be part of multiple fractures that involve the acetabulum or occasionally they can be isolated to the ischium caudal to the acetabulum.
The muscles of the pelvic floor and the origins of attached hindlimb muscles generally maintain reasonable alignment of caudal pelvic fractures that are displaced.
Healing can progress rapidly without long term consequences.
In non-racing horses, tuber ischii and tuber coxae fractures may be identified in cases of hindlimb lameness. These are often mildly to moderately displaced on radiographs but heal well conservatively with a return to soundness.
Relatively infrequent fractures in horses with reported incidence of between 0.5% and 4.4%.
In a post-mortem examination of 36 Thoroughbred racehorses that died of vertebral or pelvic injuries, 28% had pelvic stress fractures.
Pelvic fractures and third metacarpal fractures are said to be the most common fractures in National Hunt racehorses. In flat racehorses, they are said to be less frequent than tibial stress fractures, and P1 and carpal fractures.
Soft tissue swelling.
Acute lameness, after race, training, at pasture.
Observed trauma: a fall, hitting gate, fence, dystocia.
Ilial wing fractures have variable lameness but initially can be at the walk in some cases and usually obviously at the trot. Occasionally the horse is unable to stand. May resolve in some cases quite rapidly and the horse is left with a gait abnormality. Bilateral lesions do occur and confuse the lameness picture.
Acute and severe initially, becoming less severe (mild to moderate) if fracture of the tubercles such as the tuber coxae or ischii.
Incomplete fractures of the ilial wing, whether uni- or bilateral may show poor propulsion and poor hindlimb action rather than overt lameness.
Ilial shaft fractures may occur from a fall or as an athletic injury. They are often very painful and produce non-weight-bearing lameness.
Fractures involving the acetabulum are extremely lame and, when moved, hop rather than weight-bear. There may be a shortened caudal phase of the stride. There may be pain on limb abduction and muscle pain and spasm around the joint region.
Palpation of the overlying muscles for swelling, muscle spasm, atrophy or pain.
Crepitus may be felt on palpation of the greater trochanter, by rocking the horse side to side, or during manipulation of the affected hindlimb or pelvis (may decrease with time since injury).
Muscle atrophy (in injuries of prolonged duration >2 weeks). Usually gluteals but also quadriceps, semimembranosus, semitendinosus muscles in tuber ischium fractures.
Majority of tuber coxae fractures lead to visible and palpable asymmetry, with displacement in a cranioventral direction. Most cases have an unusual hindlimb gait [LINK], with the hindlimbs tracking to one side of the forelimbs. Horses are usually more lame at the walk than the trot. Lameness often rapidly improves in 24-48 hours.
Displacement of ilial shaft fractures may lead to laceration of the iliac artery and death by fatal hemorrhage.
Palpation of the bony landmarks of the pelvis for position, symmetry, angle and pain:
Ventral displacement of one tuber sacrale is common in unilateral ilial wing fractures and pain may also be present.
External swelling may be noted in tuber coxae or ischii fractures (painful swelling often below the tubera) or where there is an iliac wing fracture (soft tissue swelling over upper thigh and/or lateral pelvis). There may be guarding and muscle spasm on palpation.
Deviation or tipping of the pelvis toward the side of the fracture.
Tuber coxae and tuber ischii fractures are often not painful on palpation in the more chronic stages but asymmetry may become more evident.
Direct manual assessment Musculoskeletal: rectal palpation of the pelvic integrity especially the pubis, internal surface of the ilial wing and ventral border of the sacroiliac joint.
Crepitus (usually associated with external crepitus).
Swelling or protrusion into the pelvic cavity (often associated with acetabular fracture): maybe hematoma, callus formation, or displaced pelvic bones.
Rocking the horse from side-to-side or picking a leg up and moving it in a rotary action may increase the chances of palpable crepitation.
Only 30% of cases were positive to this in one study and usually only within the first 48 h of injury.
Bilateral ilial wing fractures can produce similar neurological findings to sacral fractures associated with severe nerve root damage consequent to movement of the pelvis in relation to the sacrum Neurology: examination - adult.
The sacral wing, internal part of the sacroiliac joint and the deeper parts of the femoral head are not possible to visualize.
Minimally displaced fractures, those with poorly developed callus and incomplete fractures of the ventral surface of the ilium are difficult to image.
Should always be used in conjunction with careful clinical examination and other imaging modalities.
Site and extent of the fracture can often be determined helping to give accurate information about management and prognosis. The healing process can also be monitored allowing changes in management to be made if necessary.
Easily performed in the standing horse:
Linear or sector-array 3.5 to 5 MHz transducer is required.
A standoff may be required for structures close to the skin surface.
Clipping may be required for cases with thicker coats and in the winter.
Always evaluate both sides of the pelvis.
Change in contour of pelvic surface.
Callus may be detected in chronic cases.
Acetabular involvement can only be partially determined.
Increased risks to the patient from the induction and recovery process in general anesthesia:
Further injury or exacerbation of the original problem.
Risk of iliac artery damage from further displacement of iliac fractures.
Some clinicians have suggested delaying radiographs until 6 weeks after onset of lameness if horse is to be anesthetize, but the above risks still exist at this time.
Ventrodorsal and oblique views of the acetabulum, ilium and ischium.
Considerable debate about the use of radiography under anesthesia where pelvic fractures are suspected. A combination of standing radiography and standing ultrasonography provides very accurate chances of a specific diagnosis and is usually preferred in most patients, particularly as the animal increases in size.
Scintigraphy Bone: scintigraphyis very effective at detecting pelvic fractures in the standing horse. Early fractures may not be evident for several days after injury.
Dorsal and oblique views as the former can miss some ilial fractures.
Valuable for early diagnosis of the presence of a fracture but not in assessing the degree of comminution. The latter may be assessed by ultrasonography and the two imaging modalities complement each other.
No need to use general anesthesia.
Sensitivity estimated at 94%.
Computed tomography (CT)
CT Computed tomography can be used and has been found to be more accurate than radiography in assessing fracture configuration, treatment options and correlation to future athletic performance.
Particularly helpful when there is a possibility of acetabular and periarticular involvement.
Confirmation of diagnosis
Discriminatory diagnostic features
Definitive diagnostic features
Gross autopsy findings
Fractures of femoral head maybe identified that were not apparent on radiography.
Stall or box rest for 3-43-6 months depending on the fracture type:
Cross-tying has been suggested for the treatment of pelvic fractures to prevent the horse lying down and further exacerbating the fracture. Usually this is necessary for about one month. The horse should be fed from the floor and monitored carefully for signs of respiratory disease. Some clinicians do not agree with cross-tying and many horse have been treated successfully without it.
After 1-2 months of strict box/stall rest, depending on the fracture type and displacement, another 1-2 months of box rest with light in hand walking may be possible.
In severe displaced fractures a further 2 months of limited area pasture rest may be necessary.
Incomplete ilial wing stress fractures often do not require cross-tying and can start in hand walking as early as 4 weeks post diagnosis with ridden trot work at 8 weeks.
Return to exercise after convalescence needs to be slow and progressive to allow the horse’s skeletal system to adapt post the fracture layoff.
Ensure sound footing in box/stall. Overuse damage to the opposite hindlimb, including laminitis Foot: laminitis, is possible and should be treated by deep litter bedding and then frog supports as soon as it is possible to lift to the non-lame limb safely.
Surrounding muscles keep most non-articular pelvic fractures stable and aligned with rapid formation of a bony callus.
Currently, the only published surgical treatment for pelvic fractures is debridement and removal of secondary septic osteitis of fractured tuber coxae, a situation which is relatively uncommon.
Other procedures that have been cited in textbooks include internal fixation of ilial fractures that extend into the acetabulum; arthroscopic removal of comminuted portions within the coxofemoral joint; femoral head excision in small horses and ponies; and hip replacement in small horses with chronic fracture-induced osteoarthritis. Additionally select ilial shaft fractures that are unstable and uni-/bilateral, and which compromise the pelvic canal axially, may be candidates for surgical repair.
Carefully thought-out training regimens for Thoroughbred racehorses, especially when young.
Regular monitoring of Thoroughbred racehorses for signs of hindlimb gait changes and changes in performance.
Good if there is no relationship between fracture location/type and long-term survival, however horses that sustain an acetabular fracture are less likely to return to athletic function (about 20%). Survival rate for all pelvic fractures with medical treatment ranges from 50-77%.
Good for racing and other athletic pursuits with fractures of the tuber coxae (93% recovery). Partial and less displaced fractures had the best prognosis.
In Thoroughbred racehorses with non-articular pelvic fractures, the degree of fracture displacement of the ilium or ischium appears to have no bearing on their return to racing, although displaced fractures may have fewer starts.
Fractures involving the acetabulum have a very poor likelihood of returning to racing and at least 50% are euthanized Euthanasia because of continuing pain and debility. The prognosis in foals is considerably better and treatment by 12 weeks box rest and then progressive turnout to pasture has been successful with less chance of the development of osteoarthritis Musculoskeletal: osteoarthritis (joint disease).
Fair for comminuted fractures involving the acetabulum or sacroiliac joint → prolonged weight bearing on contralateral limb → secondary complications.
Distortion of the pelvic canal after fracture may → future dystocia Reproduction: dystocia although the degree of mobility and comfort in the hindlimbs is more significant to the future ability of a mare to carry a foal to term and have no problems at parturition.
Ilial shaft fractures that are very lame for a long time can develop permanent upward fixation of the patella Patella: upward fixation, contracture of the hamstring group of muscles, and spastic hyperextension of the tarsus. These complications result in a very poor prognosis.
Reasons for treatment failure
Incorrect or inadequate rest following fracture.
Further displacement of the fracture during convalescence.
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Other sources of information
Ducharme N G & Nixon A J (2020) Fractures of the Pelvis. In: Equine Fracture Repair.Ed: Nixon A J. 2nd edn. Wiley Blackwell, USA.
Almanza A & Whitcomb M B (2003) Ultrasonographic Diagnosis of Pelvic Fractures in 28 Horses. In: Proc 49th AAEP Convention. pp 50-54.