The Pelvis and Sacrum

Question 1

identify the major anatomical landmarks of the pelvis and sacrum relevant to fractures and other injuries

Answer 1

see ppt slide!

Question 2

describe the functional implications of fractures along the weight bearing axis of the pelvis

Answer 2

1. a general rule is that fractures that occur along the weight bearing axis should be repaired!
2. weight bearing axis of pelvis: see ppt slide too
   -NOT in weight bearing: ischium
   -IN: ilial body, acetabulum and cranial!

Question 3

describe differences between cat and dog pelvis

Answer 3

feline:
more rectangular than dog, narrower pelvic canal, no sacrotuberous ligament, but still treat the same way!

Question 4

describe basics of pelvic fractures

Answer 4

1. the pelvis is a box: if displacement is present, there MUST be at least 3 fractures
2. MOST animals with pelvic fractures have OTHER major body systems affected (it takes a lot to break a pelvis): check pulmonary, abdomen, urinary, spinal!!!, other skeletal, cardiac, soft tissue injuries
3. neurologic injuries are common comorbidities with pelvic fractures too! (lumbosacral trunk common)

Question 5

describe treatment timing for pelvic fractures

Answer 5

1. best repaired 7-10 days after injury
   -perform bilateral repairs simultaneously or within a short period of time to allow early weight bearing and avoid overstress of one repair
2. narrowing of pelvic canal at least or greater than 50% may result in obstipation or constipation (esp in cats with their narrower pelvic canal!)
   -normal parturition can never be ASSURED even with surgery

Question 6

describe the basics of sacroiliac luxation

Answer 6

1. synovial and cartilaginous components only allow for small amount of natural movement in this joint, and as animals age the joint may become fused!
2. luxation is separation of the joint between the sacrum and ilium WITHOUT fracturing

Question 7

describe how to diagnose sacroiliac luxation (palpation and imaging)

Answer 7

palpation: instability between ilial wings and sacrum

imaging (V/D radiographs):
1. cranial displacement of ilial wing
2. SI joint: a step at the transition between the wing of the ilium and sacrum (check here first if suspect SI luxation!)
3. ilial wing: cranial aspects are not at same level

Question 8

desribe treatment of sacroiliac luxation

Answer 8

1. non-surgical/conservative: MANY dogs do well with this option!!
   -consider if there is minimal instability, low pain, minimal neuro involvement, and minimal narrowing of pelvic canal
   -strict cage rest for at least 4-6 weeks and use oral analgesics
2. surgical: place a screw across sacrum to lock into place

-consider if severe pain, displacement compromises pelvic canal or hip joint alignment, sporting or working dogs who need rapid return to function, of if concurrent injuries that require stabilization of SI joint

-open approach: MUST know anatomy, small margin without entering spinal canal!, difficult visualization

-closed approach (minimally invasive)
–use of intra-operative radiography, better visualization of the sacrum, less likely to drill into spinal canal

Question 9

describe basics and fixation of ilial fractures

Answer 9

fracture configuration:
1. a long oblique mid-body fracture is MOST COMMON
2. often the caudal fragment displaces medial and cranial and compromises the pelvic canal and can cause injury to the lumbosacral trunk medial to the body of the ilium

fixation:
1. a bone plate placed on the lateral side of the ilial wing is most common
2. dorsal or ventral plating may improve stability; the ventral surface of the ilium is tension surface in weight bearing but is more difficult technically to plate
3. optimal lateral plating: 3 screws cranial and caudal to fractures; 1-2 screws may penetrate sacral wing

Question 10

describe prognosis of ilial fractures

Answer 10

excellent! good environment for bone healing, excellent soft tissue coverage, great blood supply

mild narrowing due to inappropriate contouring is rarely of clinical consequence

Question 11

describe classification and diagnosis of acetabular fractures

Answer 11

1. articular fractures so precise reduction is essential!!
   -cranial 2/3 of acetabulum carries most of the weight-bearing forces so REPAIR is a priority
   -caudal 1/3 carries minimal lameness but lack of repair leads to OA
2. 4 classifications based mainly on location:
   -cranial, central, caudal, comminuted
3. diagnosis:
   -CT often required! for complete understanding of the fracture configuration; oblique rads can be helpful but CT IS BETTER

Question 12

describe treatment decisions of acetabular fractures

Answer 12

1. ALL should be stabilized due to being articular!
2. exceptions:
   -very caudal fracture: some may elect to treat conservatively and manage OA
   -high comminuted: FHO/FHNE can be a good option
3. best results when:
   -perfect anatomic reduction
   -rigid stabilization
   -early controlled motion
4. 4 repair options:
   - bone plate (acetabular plate)
   -bone plate (with concurrent ilial body fracture)
   -lag screws
   -screws, wire, and bone cement)

Question 13

describe the basics of ischial and pubic fractures

Answer 13

1. rarely surgically stabilized (not weight bearing axis)
2. surgery considered when:
   -working dogs
   -uncontrollable pain
   -herniation of abdominal contents due to: muscle avulsion with displacement, pubic symphysis fractures, prepubic tendon rupture
   -entrapment of the LS nerve trunk/sciatic nerve
   -pelvic canal narrowing of >50% that can lead to obstipation or dystocia