Ch 56 Pelvis fractures Flashcards
Epid, Pathophys
- often observed in young animals, younger than 2 or 3 years old
- road traffic accident is considered the most common cause
- The pubis was the most frequently fractured bone
- bilateral: many require multiple and bilateral surgeries in order to restore weight-bearing
- 71% had multiple body system injuries
pulmonary trauma (29%), cat 53%
hemoabdomen (15%),
soft tissue injury (15%),
cardiac arrhythmia (9%),
spinal trauma (6%) cat 28%
urinary tract injury (2%)
abdominal 39% cats
Anatomy
- box-like structure
- rigid structure, in order for a fragment to become displaced, associated with at least two, and often three, additional fractures
- fractures commonly occur in specific locations
- Stress fracture has been observed in the acetabulum in racing Greyhounds
What % of pelvic fractures have fractures at three of more sites in the pelvis?
76%
What percentage of pelvic fractures effect the weight bearing axis?
Bilateral weight bearing axis?
Unilateral 89%
Bilateral 39%
What % of pelvic fractures have urinary tract trauma?
How many require surgery?
- 39%
- 16% require surgery
- ruptured bladder , urethral rupture, and ureteral avulsion
What is the most common cause of neuro injury secondary to pelvis fractures?
outcome?
How many have permanent neuro dysfunction?
Injury to the lumbosacral trunk
- associated with craniomedial displacement of iliac fractures or sacroiliac separation
- 91%
81% peripheral nerve injury had good or excellent recovery within 16 weeks
15% permanent
entrapment of the sciatic nerve
- The lumbosacral trunk becomes the sciatic nerve as the second sacral nerve joins the lumbosacral trunk, passes over the greater ischiatic notch and exits the greater ischiatic foramen
- 6% sciatic nerve from displaced acetabular and ischial fractures.
pelvic fracture Dx
- general physical, complete orthopedic, and neurologic examinations are important in all polytrauma
- minimum database (CBC, serum chemistry profile, blood gas analysis, UA, and ECG)
- abdomen (AFAST) and the thorax (TFAST)
- thorax rads
- Radiographs: standard ventrodorsal, lateral, and oblique views
- ## CT is useful for complex injuries to the acetabulum and sacrum > 3D images do provide a rapid identification of the injuries (2D more accurate)
pelvic # surgery
pre-op considerations?
indications? (6)
- delayed until the animal is hemodynamically stable and respiratory function is considered adequate for GA
- soft tissue injuries, such as diaphragmatic hernia or urinary tract rupture, take precedence
- repair of pelvic fractures more time dependent > best completed within 7 to 10 days (Muscle contraction and early fibrosis may prevent normal repair options)
indications
- Restoration of weight bearing,
- restoration of joint congruity/reduce DJD
- preservation and protection of neurovascular
- prevent pelvic diameter narrowing
- prevent pelvic malunion
- Bilateral > to distribute early weight bearing
repaired surgically
- acetabulum
- ilium
- luxations of the sacroiliac joint
treated conservatively
- pubis
- ichium
may require sx
- pubic fracture (provide an attachment point in case of prepubic tendon rupture or avulsion
- avulsion fracture of the ischiatic tuberosity (muscular origins of the semitendinosus, semimembranosus, and adductor muscles)
Malunion and narrowing of the pelvic canal, particularly if the pelvic canal is narrowed by 50% or more, may result in obstipation.
This is a particular concern in cats
conservative tx
- Selected cases may be amenable to conservative management > 75% of dogs attained complete recovery
- recovery period was often prolonged compared to that of surgical treatment
- nondisplaced or minimally displaced fractures of the ilium and minimally displaced fracture-separations of the sacroiliac joint may be selected for nonsurgical
- Sequential physical and radiographic examinations are indicated in the first 5 to 7 days after trauma because fragment displacement and pelvic canal narrowing may continue to worsen
conservative tx
- cage rest
- moderation of activity,
- appropriate nursing
- analgesia,
- physical rehabilitation as the fractures begin to stabilize
Do caudal acetbaular fractures need surgical fixation?
Controversial
- Animals seem to weight bear and be more comfortable than with other acetabular fractures
- Two studies have demostrated that the caudal acetabulum DOES have a important weight-bearing role
- Long term follow up of conservatively managed cases has shown unsatisfactory results for lameness and pain associated with significant DJD
- Often difficult to reduce and stabilise
- finances and chronicity also influence decision
What is the common obliquity of ilial fractures?
often compromises pelvic canal diameter
Cranioventral to caudodorsal
Usually cranially and medially displaced
may cause injury to the lumbosacral trunk (medial to ilium)
surgical approach for common iliac body fractures
gluteal roll-up
muscles are elevated from the lateral and ventral aspect of the ilium and are retracted dorsally
surgical approach for repair of caudal iliac fractures that extend dorsal to the acetabulum
lateral approach combined with a dorsal surgical approach to the hip joint
What are some techniques of reducing ilial fractures? (6)
- Direct fragment manipulation (bone forceps on caudal fragment)
- Gentle levering
- Lifting proximal femur (forceps on trochanter)
- Approach to tuber ischii (kern forceps)
- Using the implant (plate slightly overcontoured and secured to caudal fragment, additional screws are placed in sequence, from caudal to cranial)
- Forceps sliding maneuver (oblique fractures)
if contouring is inadequate, under-reduction may result.
What are the surgical options for ilial fractures?
Bone plating (lateral, dorsal, ventral)
ESF
Lag screws (strong mechanically, difficult to achieve)
Composite fixation (screw, sire, PMMA)
- Dorsal plating in cats has shown less screw loosening and less canal narrowing (longer plate and also allows longer screws)
- 3 screws caudal and a minimum of 3 screws cranial (bone thin and soft)
- one or two screws to penetrate deeply into the sacral wing (effect on long-term stability has not yet been fully elucidated)
- avoid misdirection > penetration of the lumbosacral disc space or L7 vertebra
- T-plate can be used as alternative to only 2 screws in caudal fragment
- Stronger fixation > positioning a longer plate dorsally to extend over the acetabulum
Plates: 2.7mm cats/small dogs, 2.7-3.5mm medium/large dogs)
what is the tension surface of the ilium?
Ventral
locking plates vs DCP
- cadaveric study: did not show any difference between locking and nonlocking plates
- others found a decrease in complications and screw loosening when locking plates were used for triple pelvic osteotomy
prognosis for iliac fractures
- with plate fix: considered to be excellent, and healing allows early return to controlled weight bearing
complications
- mild pelvic canal, resulting from inadequate plate contouring
- screw loosening (often cranial fracture segment), may or may not lead to revision
- implant failure
- collapse or malreduction of the pelvis (narrowing > 45%) must be addressed quickly
- Neurological damage caused by surgical manipulations or reduction
-»_space;> lack of improvement after 3 to 4 months warrants a poor prognosis for return to function
What is secondary acetabular protrusion?
Medial luxation of the femoral head inside the pelvic canal following acetabular fracture
acetabular fracture
Anatomical reduction, rigid fixation, and early mobilization are critical for successful treatment
- simple transverse, oblique, or comminuted
- classified by location: cranial, dorsal, caudal, and central (fossa, the medial wall +/- articular)
- CRanial #: femoral head generally remains attached to the caudal fragment, which displaces medially
- caudal #: femoral head generally remains attached to the cranial fragment, and many animals will be weight bearing upon presentation
- Central #: femoral head is generally displaced medially
Repair of acetabular fractures is generally directed at reconstruction of C-shaped articular surface
acetabular sx
too comminuted:
- salvage procedure, FHNE
- partially reconstruct the acetabulum + total hip replacement once healed
Fractures of the medial wall
- often present in conjunction with fractures of the dorsal rim
- continued significant medial displacement/subluxation of the femoral head are often considered unrepairable
- in some cases, repair of the medial wall through a ventral approach may be possible
- salvage procedure: FNE or THR
APPROACH:
- Bone holding forceps placed on the greater trochanter to apply lateral distraction
- caudal segment is often displaced medially > Bone forceps placed on ischium
- Medially displaced fragments can be brought into alignment with small bone hook or a Senn (avoid damage to the sciatic nerve)
- maintain reduction: pointed reduction forcep, K-wires placed across (prevent perforation of the rectum), assisstant to maintain
surgical approach to the acetabulum?
caudal acetabulum and the cranial aspect of the ischium?
dorsal approach with osteotomy of the greater trochanter
accomplished by tenotomy and elevation of the insertional tendons of the gemelli and internal obturator muscles
sx options for acetabular fracture (4)
- Bone plate fixation applied to the dorsal surface > Curved acetabular, straight, reconstruction, and “T” or “L” plates
- Comminuted acetabular fractures may require a longer plate than the acetabular plate
- Locking plates with locking screws > aid in maintaining reduction because contour does not have to be perfect, no advnatge in strength
- screws placed in lag fashion
- composite: K-wires, screws, orthopedic wire (18 or 20 g), and PMMA (PROS: no need contouring, all # types, mechanically strong)
- excessive volume of cement may cause interference with the sciatic nerve or hip joint
Careful contouring of the bone plate is essential to maintain reduction of the articular surface
Plate luting with PMMA way of artificially improving the fit
What is the prognosis for acetabular fractures?
generally very good!
- 83% occassional or no lameness
- 83% reduced mid-thigh circumference
DJD of varying severity was observed.
Sciatic nerve iatrogenic damage occurring during reduction and stabilization.
Loose or broken implants were uncommon.
Combined Iliac and Acetabular Fractures
two recognizable patterns?
- oblique iliac fracture is widely spaced from the acetabular fracture, allows several possible methods of fixation using one or two plates
- comminuted iliac fracture is located in close proximity to a comminuted acetabular fracture, often characterized by a large triangular iliac/cranial acetabular fragment
- requires combined gluteal roll-up and dorsal open surgical approach
- Widely spaced: iliac fracture is often reduced and plated first
- comminuted: triangular fragment is first reduced to the proximal ilium, kwire/lag srews for interfragmentary fixation of smaller fragments, caudal acetabular fragment is then reduced, consider single, long, straight plate can be used as primary fixation
- recon plates not strong enought for large dogs
What % of SI luxations are bilateral?
23% in dogs
18% in cats
Sacroiliac Luxation
- iliac wing in sacroiliac luxation usually occurs cranial and slightly dorsal to the sacrum
- more severe displacement may occur during the recovery period
- ischial and pubic fractures are frequently present
- caudal hemipelvis displaces medially and compromises the diameter of the pelvic canal
- ventrodorsal radiograph, the medial wall of the iliac body should transition smoothly in a gentle curve with the caudal aspect of the sacral wing
- 85% have severe orthopedic injuries that disable both pelvic limbs
Ex
- severe weight-bearing or non–weight-bearing lameness
- pain upon palpation of the joint or when attempting to stand.
- Sacral nerve roots and the lumbosacral trunk > urinary bladder, anal sphincter, and sciatic nerve
- STUDY: 81% of the cases had good functional neurologic recovery within 16 weeks
Surgical stabilization of the sacroiliac joint
selected for cases that have severe pain or displacement that compromises the pelvic canal
- conservative treatment often results in prolonged cage rest, recumbency, or discomfort
- pelvic # repaired before the sacroiliac luxation (though implants may obscure the view of the sacral body with fluoroscopy)
- dorsal approach (ventral possible)
- Where available, intraoperative fluoroscopy
- largest screws maximizes sacroiliac repair strength, and penetration 60% width of the sacrum minimize postop loosening
Where is the ideal location of the screw in the sacral body?
Inserted at what angle?
- drill hole in the sacral wing is made exactly perpendicular to the table
- sacral wing surface will not be exactly parallel to the table > tilted approximately 10 degrees inward dorsally
Inserted at 100 +/- 4.7 degrees in dogs
97 +/- 6.9 degrees in cats
What are the landmarks for screw placement in the wing of the ilium for a SI lag screw?
- iliac glide hole is located by palpating the joint surface on the medial side of the ilium.
- A prominence may be palpated on the medial joint surface of the adult dog
- Screw length is determined by glide hole and the sacral wing hole or determined presurgically on appropriately calibrated preoperative radiographs
- Bilateral sacroiliac repairs may be completed with screw fixation, in lag fashion, from each side
- > > alternative: use an aiming device or fluoroscopy to drill 100% across the sacral body and place a single long trans-iliosacral screw or a rod
- Fluoroscopy can greatly aid in the placement, Adequate positioning of the animal is essential (confirming the superposition of the lumbar transverse processes) small K- wire inserted across the sacroiliac joint, keyhole incision through middle gluteal muscle, hole is drilled to an appropriate depth, based on preoperative planning
What are the 5 types of sacral fracture?
% neuro dysfunction?
Abaxial
- all fractures located lateral to the sacral foramina + spinous processes
Axial
- all fractures medial to the sacral foramina and ventral to the spinous processes.
- more likely to have associated neurologic deficits.
Type I: Alar
Type II: Foraminal
Type III: Transverse
Type IV: Avulsion
Type V: Comminuted
compared with SI, extreme pain and neurologic deficits are more common
Mechanical evaluation of canine sacroiliac joint
stabilization using two short screws
Hanlon 2022
2 short 3.5 mm cortical screws, each spanning an average of 23% of the width of the sacral body
Cadaveric experimental study.
Sample population: Twenty-four canine pelvis specimens
stabilized using a single long lag screw (LLS), 2 short lag screws (SLS) or 2 short positional screws (SPS)
Sacroiliac luxation fixation using 2 short screws created a stronger, stiffer construct when compared with fixation using a single lag screw spanning 60% of the width of the sacral body. No mechanical advantage was observed between short screws inserted in positional vs. lag fashion.
Ventral sacral nerve foraminal impingement was
observed in 3 samples
screw length shorter than the distance from the lateral aspect of the ilial cortex to the ipsilateral spinal canal wall increases the area for safe implant placement > a technique that may greatly decrease the risk of injury to sensitive surrounding anatomy.
authors hypothesize the stronger thread purchase obtained by the short positional screws in the ilium compared to lag screws
2 screws: greater resistance to rotational forces and an increased bone-implant interface providing
additive resistance to bending and shear
Defining a safe corridor for trans-iliac pin placement in cats
Garcia-Pertierra 2021
AVJ
Twenty-one cats with straight orthogonal normal pelvic radiographs were included.
A theoretical defined safe corridor is available for trans-iliac pin placement in cats between 2.0 and 5.5 kg. A 1.2-mm pin is the safest if using the mid-iliac wing start point. A more dorsal start point can accommodate up to a 2.0-mm pin if correctly aligned to the sacrum.
dorsal start point was considered to be 2 mm ventral to the most dorsal aspect of the iliac wing, 1.6mm pin recommended.
particularly where a fluoroscopy-guided surgery cannot be performed.
Trans SI lag screw fixation for SI luxation is currently the surgical method of choice in cats.20 However, the safe drill corridor is narrow at 0.5 cm2
trans-iliac pin placement are less than lag screw fixation in the sacrum. This is due to the larger area for implant placement and the more distant relationship of the pin tract to the vertebral canal and
its nervous tissue
Although an SI lag screw has shown increased
friction in the SI joint, providing a more stable construct, Yap et al.14
hypothesised that iliac wing compression achieved by trans-iliac implants is enough to reduce hemipelvis displacement based on their reported clinical cases. 14,15,24 Trans-iliac pinning, however, is not
without risks, with pin loosening and/or soft tissue focal irritation reported in dogs 4–6 weeks postoperatively.
although the amount of stability required is unknown as healing is through fibrosis and therefore may not require the same stability as bone fracture healing
Biomechanical Comparison of Double 2.3-mm Headless Cannulated Self-Compression Screws and Single 3.5-mm Cortical Screw in Lag Fashion in a Canine Sacroiliac Luxation Model: A Small Dog Cadaveric Study
Kang 2024
Fluoroscopically guided percutaneous application of double HCSwas safe in a
unilateral sacroiliac luxation model in small dogs without violation of the vertebral and
ventral sacral foramen. Furthermore, resistance to rotational force applied on fixation of the sacroiliac joint repaired with double 2.3-mm HCS estimated by maximum
failure load was significantly higher than that of a single 3.5-mm cortical screw
70% of the sacral width in the 3.5-mmCS group and 70% for the first and 40% for the second screws in the 2.3-mm HCS group.
double 2.3-mm HCS are mechanically superior to the resistance of the rotational force than single 3.5-mm CS placed in the lag fashion
a headless cannulated self-compression
screw (HCS) has an advantage in precision because the screw can be placed over a positional guidewire under fluoroscopic guidance
postoperative loosening rate of lag screw fixation for canine sacroiliac luxation has been reported to be as high as 38%, favorable outcomes can be obtained when the screw engages at least 60% of the sacral width
Conservative management of
sacroiliac luxation fracture in cats:
medium- to long-term functional
outcome
Bird 2020
Seventeen cats met the inclusion criteria, and 13 owners completed the questionnaire. Twelve cats had
an excellent outcome, with no difficulty performing normal activities. One cat had a good outcome, with slight or
occasional difficulty performing normal activities.
Sacroiliac joint ankylosis and degenerative joint disease
are thought to develop after conservative management
of SILF
indications for conservative management of SILF are
- being ambulatory,
- displacement of <50% of the joint surface,
- minimal pain or instability,
- absence of concurrent fractures of the weightbearing axis,
- absence of neurological deficits
- <45% narrowing of the pelvic canal
Evaluation of prognostic factors
for return of urinary and defecatory
function in cats with sacrocaudal
luxation
Elizabeth Couper and Steven De Decker
2020
Fifty-five of 61 cats (90%) regained voluntary urinary function. A higher neurological grade was associated with a decreased likelihood (P = 0.01) and longer duration (P = 0.0003) of
regaining urinary function. No significant associations were found between urinary outcome and age, sex, anal tone, perineal sensation, tail base sensation, degree of craniocaudal or dorsoventral sacrocaudal displacement, concurrent orthopaedic injury, tail amputation, defecatory function at diagnosis and survival. Cats that regained
defecatory function had longer survival times than those that did not recover defecatory function
neurological grade is the most important prognostic indicator
Severity of neurological signs was graded from 1 to 5, based on previous grading
systems for cats with sacrocaudal luxation. Degree of vertebral displacement was calculated on survey radiographs.
50% of cats with neurological grade 5 regained the ability to urinate.
87% of cats that regained urinary function doing so within the first 30 days.
(60%) that regained urinary function
did so in the first week
Tail amputation was performed in 36 cats (51%).
Seventeen of the 34 cats (50%) that were managed medically, regained, according to the owners, normal tail motility
only half of cats in this study that presented with loss of defecatory function regained the ability to defecate voluntarily.
Caudal nerve lesions are responsible for tail
paralysis, while damage to either the pelvic or pudendal nerves can result in urinary and faecal dysfunction
Early tail amputation has been recommended to relieve ongoing neuronal traction caused by a combination of persistent motion at the fracture site and the ‘hanging weight’ of the paralysed and atonic tail.3 internal tail stabilisation has been
suggested as a treatment option that combines reducing
instability, minimising ongoing neuronal traction
and sparing the tail,9,16 it remains unclear if this treatment
option results in better outcomes than medical
management or tail amputation.
the majority of these cats was euthanased in the first 4 days after presentation.
The Use of Intraoperative Skeletal Traction for the Repair of Pelvic Fractures: An Experimental Cadaveric Study
Bourbos 2021
Cadavers from 10 adult dogs, A distraction of at least 2 cm was obtained
Intraoperative skeletal traction provides a useful and reliable tool for the
reduction in experimental oblique and transverse iliac fractures in dogs. There were
strong correlations between body weight and the force required
studies in human medicine have shown that the duration of traction is a critical feature because traction devices have been associated with iatrogenic damage.22 Excessive traction is associated with complications such as impairment
of vascular and nerve integrity
Triple Pelvic Osteotomy Fixed with Lag Screw for the Treatment of Pelvic Canal Stenosis in Five Cats
Cinti 2020
The iliac fragments were fixed by a
2.7-mm lag screw (5/5 cases) and an additional 2 Kirschner wires 0.8mm (1/5 cases).
bone decortication 4/5 cases or not 1/5
case
The radiographic examination immediately postoperatively and 8 weeks
postoperatively showed a mean pelvic canal enlargement of 20% (range 7–38%).
Minor complication occurred in one case; this resolved 15 days postoperatively without
any treatment. Complications and recurrence of obstipation did not occur during the
final follow-up, ranging between 5 months and 1 year in any of these cases
If clinical signs have been present for less than 6 months, widening the pelvic canal has been proposed as a treatment option for obstipation/megacolon, greater than 6 months, subtotal colectomy might be indicated
The pelvic canal can be widened by revising the fracture malunion via ostectomy of impinging bone or corrective osteotomy and stabilization after correcting the pelvic canal
narrowing, distraction of each hemipelvis after osteotomy of the entire pelvic symphysis is performed
use of a single compression screw does not follow the AO23 principles of fracture management; however, the clinical results indicate that the screw positioned in this fashion gives sufficient stability to allow the healing of the osteotomy
more cases needed to deterimine success/risk
Single Transsacral Screw and Nut Stabilization of
Bilateral Sacroiliac Luxation in 20 Cats
Andrea Pratesi 2018
Twenty consecutive cats with bilateral SI luxation were included. Six cats (35%)
had additionalmusculoskeletal injuries that required stabilization. Luxationswere stabilized
with a single 2.7 cortical self-tapping transsacral screw and nylon nut (a metallic nut was
used in one case). Postoperative radiographs confirmed SI reduction in all cats and a mean
pelvic canal width ratio of 1.21 (a ratio of 1.1was considered optimal). All cats available at follow-up examination were able to walk without signs of discomfort
the drilling angle does
not need to be determined due to the use of a drill bit aiming
device, which directs the drill bit to the calculated location on
the opposite sacral wing.
it is complicated,
if not impossible, to draw conclusions as to whether
this technique compares favourably with previously published
reports of other techniques used for stabilization of bilateral
luxation in cats, due to the significant variation of data that can
be obtained from these case series.
Biomechanical properties of plate constructs for feline ilial
fracture gap stabilization
Double plating improved stiffness and resistance to failure of comminuted
feline ilial fracture constructs compared with all other fixations. Single locking
plates produced superior constructs compared with single nonlocking constructs.
Clinical significance: Locking implants are recommended to repair comminuted
feline ilial fractures for their extended fatigue life and resistance to screw loosening.
Orthogonal plating offers a strong nonlocking alternative.
