Ch 57 Hip luxation

Question 1

Answer 1

diarthrodial articulation between the femoral head and acetabulum
- luxation: complete loss of contact between articular surfaces.
Subluxation: partial dislocation where the normal relationship is altered but contact between the joint surfaces remains.
- luxation involving the hip joint is described by the direction the femoral head moves relative to the acetabulum

Question 2

What are the primary jip joint stabilisers?
How many have to be damaged for luxation to occur?

Answer 2

Primary Stabilisers:
- Ligament of the head of the femur
- Joint capsule
- Dorsal acetabular rim

2 of 3 need to be damaged for joint luxation

Question 3

What are the secondary stabilisers of the hip?

Answer 3

Acetabulum labrum
Transverse acetabular ligament
Hydrostatic pressure
Periarticular muscles (gluteals, iliopsoas, quadratus femoris, gemelli, internal obturator, external obturator)

Question 4

What percentage of joint luxations does the hip joint account for?

Answer 4

90%

Question 5

What percentage of hip luxations are bilateral?

Answer 5

6% in dog
9% in cat

Question 6

What percentage of hip luxations are craniodorsal?

Answer 6

75%

Question 7

Etiology and Pathophysiology

Answer 7

• Vehicular trauma is the cause of up to 85%
• severe hip dysplasia, falls, spontaneous luxation, and unknown
• Injuries to other body systems occur concurrently in up to 55% of patients
• trauma > supraphysiologic forces on femur
• falls laterally > femur in adduction and distracting the femoral head from the acetabulum (stretched capsule and ligament)
• greater trochanter strikes the ground > femoral head is forced over the dorsal rim, causing a tear of capsule and the ligament.
• pull of the gluteal muscles aids in displacing the femoral head craniodorsally

luxation results in:
- tearing and contusion of the periarticular muscles and the articular cartilage
- contact and abrasion of the femoral head
- loss of lubrication and nourishment normally provided by the synovial fluid

Question 8

How does a dog with craniodorsal hip lux classically hold its leg?

Answer 8

Externally rotated and adducted, usually NWB

Question 9

Dx hip lux

Answer 9

confirm the luxation and identify concurrent trauma-related injuries
- pain, crepitus, lameness, external rotation and adduction, asymmetry of the hips (dorsal displacement),
- increased distance between the greater trochanter and the ischiatic tuberosity,
- apparent shortening of the affected limb
- CS ventral luxation (abduction and internal rotation, engthening of limb)
- placing a thumb in the ischiatic notch
- When the hip joint is reduced, the greater trochanter is positioned distal

Radiographic
- orthogonal, confirm the luxation, determine the direction
- presence of acetabular or other pelvic fractures, femoral head or neck fractures, slipped capital physis (in immature patients), and evidence of hip dysplasia

Question 10

treatment hip lux

Answer 10

Reduction and stabilization > accomplished using closed or open techniques.
- treatment for shock
- not a surgical emergency, should be treated within 72 hours to minimize pathologic changes (more difficult 4 to 5 days after luxation > minimize destruction of cartilage (gene exprssion changes) and before muscle spasticity and fibrosis prevent easy relocation)
- attempted closed reduction before open surgical reduction is recommended and does not appear to alter the long-term prognosis Bone 1984

SX indicated:
- acetabular or femoral head fractures,
- reluxation after confirmed closed reduction,
- concurrent injuries or the luxation is chronic (need to assess cartilage)
- In dysplastic joints, restoration of joint stability may not be possible because of preexisting pathology

Question 11

Closed Reduction and Stabilization

Answer 11

more likely to be successful if performed in the first few days after luxation.
- Unsuccessful: intra-articular fracture, muscle contracture, the presence of soft tissue or hematoma within the acetabulum, inflammation of the ligament, or periarticular fibrosis.
- under general anesthesia or sedation with epidural

craniodorsal luxation:
- the femoral head is disengaged from the dorsal acetabular rim by grasping the hock and stifle and externally rotating
- Traction applied to the limb in a distocaudal direction to align the femoral head over the acetabulum.
- The limb is internally rotated and abducted to seat the femoral head into the acetabulum

caudoventral luxation:
- femoral head is disengaged from the obturator foramen using traction on the limb and countertraction on the ischiatic tuberosity.
- disengaged from the obturator foramen, the femoral head is manipulated laterally and cranially into the acetabulum.
- medially directed force is applied to the greater trochanter as the limb is manipulated through a full range of motion to displace blood clots, joint capsule

Joint stability is assessed during gentle manipulation of the hip joint, including flexion, extension, external rotation,
- Reluxation occurs most often during external rotation, chronic luxations or hip dysplasia

Question 12

reluxation following closed reduction?

Answer 12

more than 50% of cases
- augmentation recommend after closed reduction
- Lefloch 2021: 51% success of closed reduction in 51 cats
- sling is generally required for 10 to 14 days, until the joint capsule and the periarticular soft tissues are sufficiently healed to maintain reduction

Question 13

In what position does an Ehmer sling hold the leg?
What is the relux rate after a closed reduction and Ehmer?

complications?

Answer 13

Flexes the hip, abducts and internally rotates the femur

Reluxation 15-71%

complications
- slipping of the sling,
- vascular compromise/necrosis,
- decubital ulcer formation

Question 14

What method are available to augment a closed reduction? (5)

Answer 14

.1. Ehmer sling
- schlag 2019: - 40 of 92 (43.5%) dogs had reluxation, Forty-six (50%) dogs had soft tissue injuries

.2. Hobbles (ventral luxation)

.3. Ischioilial pinning (devita pin)
- reduction rate 73% but 32% complication
- Complications:pin migration, reluxation, sciatic nerve injury, damage to the femoral head, and joint sepsis

.4. ESF

.5. Transarticular pinning

Question 15

What is the overall success rate with open reduction?
What are the available options? (10)

Answer 15

Overall success 85%
- Capsulorrhaphy (83-90%)
- Prosthetic ligament technique (66-100%)
- Transposition of greater trochanter (84%)
- Transarticular pinning
- Toggle-rod (81%, relux 6-11%)
- Fascia lata loop stabilisation
- Transposition of sacrotuberous ligament
- Extra-articular iliofemoral suture
- FHO
- THR

Question 16

sx approach

Answer 16

craniolateral approach +/- osteotomy of the greater trochanter or tenotomy of the deep and middle gluteal muscles

• soft tissues and hematoma are removed from the acetabulum,
• Damage to the femoral head, acetabular rim, and joint capsule is assessed
• cartilage damage is severe, total hip replacement or femoral head and neck

Question 17

Capsulorrhaphy

Answer 17

• Large, monofilament, nonabsorbable or absorbable sutures are preplaced in the capsule using a horizontal mattress or cruciate pattern and then tied with the femur internally rotated and abducted
• Success rates of 83% to 90% have been reported
• Alternative methods are required if the joint capsule is severely damaged or avulsed from the femur or acetabulum.
• Tenodesis of the deep gluteal muscle

Question 18

Prosthetic Capsule Technique

Answer 18

two bone screws or bone anchors are placed in the dorsal acetabular rim
- An anchor point is created on the femoral side by drilling a hole from cranial to caudal through the proximal portion of the femoral neck.
- Large monofilament or multifilament suture material in a figure of eight pattern > nylon, Fiberwire or Fibertape.
- prevent reluxation in 66% to 100%
- Excellent or good outcomes were noted in 65% to 67% of dogs; 18% had mild lameness and 18% had severe lameness.

Question 19

Transposition of the Greater Trochanter

Answer 19

• When the osteotomy is repaired, be transposed distal and caudal to its original location (approximately 1 to 2 cm, depending on the size of the patient)
• increasing the medial pull of the gluteal > abduction and internal rotation the femur.
• reattached with a tension band wire fixation or a screw in lag fashion.
• Trochanteric transposition alone prevented reluxation in 84% of patients in one report.

Question 20

Transarticular Pinning

used after closed or open hip reduction

Answer 20

• Steinmann pin or Kirschner wire
• The appropriate pin is selected based on the size of the patient
• For closed insertion, the pin is inserted normograde, into the medial wall of the acetabulum.
• For open insertion, the pin may be inserted in a retrograde fashion
• removed after 2 to 3 weeks
• 40 dogs described an overall 80% success rate
• results were worse in heavier dogs and were considered unsatisfactory in 40% of dogs weighing more than 20 kg
• 70 dogs. Reluxation occurred in only 1 dog (1.6%); however, the rate of significant complications was reported to be 6%, and the rate of minor complications was reported to be 45%.

not recommended due to its high complication rate, and techniques
that do not cause additional damage to the articular cartilage are usually preferred

Question 21

Toggle Rod Stabilization

allows early use of the limb after surgery

Answer 21

• Both open and closed techniques have been described
• considered a physiologic method of hip stabilisation
• aims to maintain joint stability until the soft tissues have healed with maturation of scar tissue and reformation of the joint capsule.
• Once this has occurred, the anatomic shape of the hip joint and fibrosis of the joint capsule hold the femoral head in place

closed
- closed application with the use of fluoroscopy resulted in cartilage damage in 20% of cases and is not currently recommended Serdy 1999
- 2018 cadaver study Cartilage damage did not occur with independent drilling of the acetabulum but occurred in 6/16 hips in which the acetabulum was drilled via the femoral tunnel.
- MI with drill guides show some promise in a 2019 study, but requires more study
- Arthroscopic placement case study

open technique:
- A hole is drilled through the femoral head and neck from the region of the third trochanter to the fovea capitis with the aid of a C -shaped drill guide, second hole is drilled in the center of the acetabular fossa
- One or two strands of suture material are then inserted
- taking care not to overtighten the suture. (not allow subluxation but good ROM).

toggle
Trostel found no significance, whereas Demko found that homemade toggles increased reluxation risk

suture
Various suture materials and toggle type combinations have been biomechanically compared, including woven polyester, monofilament nylon, fiberwire and orthofibre
- OrthoFiber passed straight through the toggle rod eyelet, may provide superior stability and resistance to fatigue
- Piermattei toggle combined with #5 OrthoFiber achieved a higher load at failure
- Jha 2012
(Baltzer et al 2001, Jha and Kowaleski 2012, Kraska and Jackson 2018)

- Demko 2006: Toggle rod stabilization in dogs: 62

Question 22

toggle outcome

Answer 22

• reluxation 6% - 25% (recent lit ~10-15%)
  Premature suture failure, most within 2 weeks of surgery
• [trostel 2020] Postoperative complications (43%) dogs, major complications in 9 cases (15.5%). reluxation (10%).
• [ruperez 2021] cats 11% reluxation
• multiple studies suggest Increased risk of failure in more chronically luxated hips
• Type of suture and toggle may or may not influence outcome:
  Homemade toggles were identified to have significant variability in mechanical strength
  OrthoFiber may provide superior stability, risk of infection
• Osteoarthritis of the hip joint may progress on rads (up to 60%) may/may not br clinically significant
  -** complications**: premature suture failure; joint reluxation; injury to the rectum; sciatic nerve damage; articular cartilage damage OA, persistant lameness

Question 23

although various toggle rod constructs can sustain 41% to 47% of the load of the ligament of the head of the femur in intact specimens, they are likely sufficient for normal physiologic forces in the postoperative recovery period.

Question 24

Fascia Lata Loop Stabilization

Answer 24

similar to toggle rod fixation, except that fascia lata is used rather than suture material
- 1-cm-wide strip
- Good results have been reported in one retrospective study evaluating the fascia lata loop technique in 10 dogs and 2 cats

Question 25

transposition of the Sacrotuberous Ligament

Answer 25

another technique similar to toggle rod fixation.
- The ischial insertion of the sacrotuberous ligament is cut using an osteotome (to include a piece of ischial bone) and the ligament is isolated, taking care to avoid injury to the sciatic nerve.
- The ligament is then passed through the femoral tunnel (6-mm diameter) and is attached below the greater trochanter by placing a screw through the bone fragment and into the femur.

Question 26

Extra-Articular Iliofemoral Suture

Answer 26

• A capsulorrhaphy is performed if possible.
• hole is drilled just cranial to the acetabulum. A second hole through the femur just distal to the insertion of the gluteal muscles.
• One or more strands of large, monofilament suture material
• The joint is internally rotated and abducted, and the suture is tied.
• report of 14 patients in which an iliofemoral suture was used to stabilize acute and chronic luxations described no reluxations and no complications. No reduction in range of motion was identified

Question 27

Surgical Stabilization of Ventral Luxations

Answer 27

• dorsal approach to the hip joint is recommended
• A prosthetic capsule technique or toggle rod procedure is used to enhance joint stability, although neither technique entirely prevents ventral displacement of the femoral head.
• If ventral instability persists, the ventral acetabular ligament can be sutured
• ventral augmentation > iliac crest shelf graft; extracapsular sling; an internal fixator plate can be used to augment the ventral acetabular rim.

Question 28

Femoral Head and Neck Excision Arthroplasty

Answer 28

indication: recurrent luxations, significant fractures or OA, if cost is a concern
- biomechanics of the hind limb change following FHNE because the femoral head no longer articulates with the acetabulum and a fibrous false joint is present. > This results in a mechanical lameness due to limb-shortening, dorsal displacement of femur and restricted extension of hip
- Aggressive pain management and aggressive physical therapy are therefore critical in the early postoperative period to allow early use of the limb good-to-excellent long-term clinical outcomes with complete or near complete return to function by 1–2 months postoperatively in cats (Yap et al 2015)
- Many studies cite better results in dogs weighing less than 18 to 20 kg
- factors that can influence postoperative outcome include age, temperament, activity, surgical technique, postoperative physical therapy, and the severity of muscle atrophy at the time of surgery
- The bone-on-bone contact is thought to be a significant cause of pain, discomfort, and an unwillingness to use the operated limb, particularly during the early postoperative period,7,18 especially in large and giant breeds of dogs

Generally, outcomes are difficult to compare between studies due to several confounding factors

Question 29

Triple Pelvic Osteotomy

Answer 29

• provides stability by rotating the acetabulum ventrolaterally to provide greater coverage of the femoral head.
• This technique has been used primarily for recurrent luxations, for dogs with hip dysplasia, and for femoral head luxation after total hip replacement

Question 30

Total Hip Arthroplasty

Answer 30

• Hip replacement arthroplasty may be used in cases of chronic luxation, reluxation, severe osteoarthritis, or damage to the femoral head
• Pozzi 2004: Treatment of traumatic coxofemoral luxation by cemented total hip

Question 31

What is the recommended screw position for synthetic capsule technique?

Answer 31

Left: 10 and 1 o’clock position on DAR
Right: 11 and 2 o’clock position on DAR

Question 32

List options of ventral augmentation after open reduction of ventral hip lux

Answer 32

Autogenous iliac crest graft
Extracapsular sling
Internal fixator plate to augment ventral acetabular rim

Question 33

post-op care

Answer 33

• confinement and restricted activity for 4 to 6 weeks to allow soft tissue healing
• monitored closely for clinical signs of reluxation
• • Management of osteoarthritis is most effective when started early in the disease process
• • Physical rehabilitation has been shown to improve joint range of motion and to enhance comfort in patients with joint injury. Once healing is complete and the joint is stable, rehabilitative techniques such as sit-to-stand exercises, inclined walking, hydrotherapy,

Question 34

Outcome

Answer 34

fair to good if reduction and stability are achieved soon after injury
- long-term study of 64 dogs treated using various techniques, including closed, extracapsular, transarticular pinning, toggle rod stabilization, DeVita and FHO found that 62% showed no lameness and 20% were severely lame
- - Osteoarthritis of the hip joint progresses in 55% to 62%
- - Closed reduction of coxofemoral joint luxation in cats had a 51% success rate.
- It may be worth attempting closed coxofemoral joint reduction in cats prior to recommending surgery
- - Placing a bandage (Ehmer or hobbles) after closed reduction may decrease the risk of the coxofemoral joint reluxating, but more studies are needed to evaluate this further
- - Retroseptive on toggle outcomes in 128 dogs: The overall complication rate was 24.2%, and the reluxation rate was 14.8%.
decreased risk of reluxation when the cause was traumatic in origin

• Multiple surgical options reported, suggesting that there is no single ideal method:
• No prospective studies compare the techniques

complication rate?
- overall: 15-43 (major -minor)
- intraop <5%
- reluxation 6-25% (10-15% dogs and cats)
- OA: 60-100% in dogs an cats

Question 35

Mathews 2020: Risk factors for reluxation after toggle rod stabilization for treatment of coxofemoral luxation in 128 dogs

Answer 35

retrospective case series, commercial toggle rod and nylon monofilament suture
The overall complication rate was 24.2%, and the reluxation rate was 14.8%.

median follow-up time was 151 days (range, 0-4440).

dogs with polytrauma that had additional
surgeries performed at the time of the open hip reduction surgery were not at an increased risk for reluxation

Published recommendations on nylon monofilament suture test selection are based on bone tunnel size, which includes having a femoral tunnel ≤20% the width of the femoral neck or a tunnel of a maximum width of onethird the diameter of the bone.2,8 Suture size to body weight ratio only approached significance (P = .07) in our study. Increasing test size of the monofilament nylon suture would be expected to provide increasingly better resistance to cycling, abrasion, and fatigue.

Question 36

Ruperez 2021: Complications and outcomes of cats with coxofemoral luxation treated with hip toggle stabilization using ultrahigh–molecular-weight-polyethylene or nylon (2009-2018): 48 cats

Answer 36

Multi-institutional retrospective cohort study.
Sample population
Forty-eight client-owned cats
Intraoperative and postoperative complications were recorded in two (4.2%) and 11 (24.4%) cats, respectively. The most common postoperative complication was reluxation (n = 5 [11.1%]). Outcome was classified as excellent in 81.1% and good in 16.2% of cats after a median of 445.5 days (range, 53-3720). No difference in rate of complications or outcomes was identified between UHMWPE and nylon.

Question 37

Trostel 2020: Coxofemoral Joint Luxation in Dogs Treated with Toggle Rod Stabilization: A Multi Institutional Retrospective Review with Client Survey

Answer 37

58 dogs
stabilized using a 4.0 or 3.2 mm commercial toggle rod and either one or two strands of OrthoFiber, FiberWire, or monofilament nylon suture. Postoperative complications developed in 25 of the 58 (43%) dogs, with major complications in 9 cases (15.5%). The most common major complication was reluxation, which occurred in 6 dogs (10%). Five of the 6 cases of reluxation received monofilament suture
good to excellent results for satisfaction with the procedure in 90%

Question 38

Schlag 2019: Analysis of outcomes following treatment of craniodorsal hip luxation with closed reduction and Ehmer sling application in 92 dogs

Answer 38

40 of 92 (43.5%) dogs had reluxation of the affected hip joint at or near the time of sling removal
Forty-six (50%) dogs had soft tissue injuries secondary to sling use; 17 of these dogs had injuries classified as severe, including 1 dog that required limb amputa¬tion. Odds of severe sling injury for dogs that had poor owner compliance with home care instructions noted in the record
Placement of an Ehmer sling following closed reduction of a craniodorsal hip luxation had a low success rate and high complication rate.

This study did not compare sling to no sling groups, so the finds should be interpreted with caution.
Ultimately > clinitian prefence – recommend choosing owners with high compliance or potentially keeping the patient in hospital for close monitoring.

Question 39

Lefloch 2021: Outcome of coxofemoral luxation treated with closed reduction in 51 cats

Answer 39

Results Closed reduction of coxofemoral joint luxation in cats had a 51% success rate. The only risk factor
demonstrating a statistically significant benefit to the success of closed coxofemoral joint reduction was the
application of a bandage (P = 0.02).

Conclusions and relevance It may be worth attempting closed coxofemoral joint reduction in cats prior to recommending surgery. Placing a bandage (Ehmer or hobbles) after closed reduction may decrease the risk of the
coxofemoral joint reluxating, but more studies are needed to evaluate this further

Question 40

Ultrasound is an accurate method compared to radiography for
diagnosing the presence of acute hip luxation in cadaver dogs and can identify the direction of luxation with variable reliability
Todd-Donato 2022

VRU

Answer 40

A total of 1140 hip ultrasounds were
performedwith good accuracy (median, 90.8%; range, 61.4–100%), sensitivity (89.5%),
and specificity (80.0%) for diagnosing the presence of hip luxation.
Intraobserver accuracy agreement varied widely.
study supported the use of ultrasound for diagnosing the presence of hip luxation but did not support replacing radiographs for diagnosing

Question 41

Open hip reduction using a novel transarticular suture stabilisation technique in 24 dogs: a retrospective study of technique, outcome and complications
Hybki 2022

NZVJ

Answer 41

single private practice, Long-term (>2 years) follow-up data
outcome was reported by owners to be excellent in 18/24
(75%) dogs with full return of limb function. Sixty-six percent (16/24) of owners reported that no lameness was observed 2 months after surgery. No minor complications were noted in this study. The hips of 6/24 (25%) dogs reluxated after surgery

the femoral head was reduced into the acetabulum and a hole was drilled through
the acetabulum. (D) Monofilament nylon was passed through the bone tunnel starting at the level of the third trochanter towards
the head of the femur (arrow), then through the hole made in the acetabulum (line) and retrieved at the ventral aspect of the ilium
(asterisk). (E) The suture was grasped and pulled under the rectus femoris muscle (asterisk) using a haemostat

small sample size, the retrospective nature of this study, variability in case management, the lack of biomechanical studies that have been used to test the strength of the nylon suture used, and the inability to perform
gait analysis on the dogs included in this study.

Question 42

Validation of a biomechanical testing
protocol of craniodorsal hip luxation
in feline cadavers and comparison
of two ultra-high molecular weight
polyethylene materials used for
extra-articular hip stabilisation
Letesson 2022

Answer 42

Eighteen hip joints, randomly
assigned either to group A (hip joints stabilised with an extra-articular ultra-high molecular weight polyethylene
(UHMWPE) implant secured by an interference screw [n = 8]) or to group B (hip joints stabilised with a UHMWPE
iliofemoral suture [n = 8]).

No statistical difference was found between groups A and B for yield and
failure load. However, the reoccurrence of craniodorsal hip luxation was higher in group B than in group A
The extra-articular UHMWPE implant stabilisation technique proved to be more efficient in avoiding reoccurrence of craniodorsal hip luxation than UHMWPE iliofemoral suture.

difference in failure mode between group A (caudodorsal hip luxation in 7/8 cases) and group B (craniodorsal hip luxation in 5/8 cases) associated with greater reoccurrence
of craniodorsal hip luxation in group B than in group A (in 5/8 and 0/8 tests, respectively).

Cyclic loading in clinical conditions and
the use of UHMWPE fibre in our study could explain this difference in failure mode.
Regarding linear stiffness, no statistical difference was found between the control group and group A, unlike between the control group and group B and between
groups A and B. This shows that stabilisation of the hip joint using a UHMWPE implant tends to approximate the
physiological ligament stiffness and capsular stabilisation of intact hip joints in feline cadavers.

Regarding relative fixation strength (% of intact joint) based on failure load in the control group, the results from
groups A (43.8 %) and B (34.7 %) were in the same range of surgical intra-articular stabilisation technique strength
as reported in previous publications on canine

The force applied to reach failure mode in groups A and B was 9.6 and 7.5 times, respectively, the force experienced through weightbearing in the limbs of the cats tested in this experiment.

Statistical differences were found between the control group and extra-articular stabilisation techniques (groups A and B) for yield and failure load.

load applied to the hip likely to be lower than the force measured.

Question 43

Outcome and Complications following Stabilization of Coxofemoral Luxations in Cats Using a Modified Hip Toggle Stabilization—A Retrospective Multicentre Study
Knell 2023

pozzi

Answer 43

mini-Tight Rope system
A multicentre retrospective study.
Animals Thirty-two client-owned cats.
A single or double loop mini-TR was used in 21 and 12 cats respectively. One
double loop (1/12 cats) and four single loop (4/16 cats) sutures failed. Moderate-tosevere
coxofemoral osteoarthritis developed in 14/27 cats (posttraumatic OA must be expected). Owner questionnaires
revealed excellent clinical outcomes.

We reported a mean long-term clinical follow-up of
13 months and a mean radiologic follow-up of 10 months.

15% complication rate, which is similar to
other studies using either the hip toggle stabilization technique with different or similar suture material (11–14%), or different surgical techniques, such as trans articular
pinning (15%) and iliofemoral sling (17%).

A 2.0mm tunnel can exceed the
recommended femoral tunnel-femoral neck diameter ratio of 20%, but did not create complications in our cases similar to
previous studies reaching even higher ratios

Suboptimal drilling of the femoral tunnel in terms of isometric position of the holes in the cis- and transfemoral cortices may lead to the persistence of joint instability and
OA progression.

Question 44

Caudoventral hip luxation in 160 dogs (2003–2023):
A multicenter retrospective case series
Loh 2024

Answer 44

Low-trauma accidents accounted for 82.9% of cases > MVA accounted
for only 6.5%. Over-represented
breeds included poodles (38.1%)
success rates of closed reduction alone, closed reduction/
Ehmer sling, closed reduction/hobbles were 9.1%, 15.2% and 48.8%, respectively.
Success rate for toggle rod stabilization was 88.2%. Complication rate of hobbles was 31.9% versus 60.6% for Ehmer slings.
Median age of presentation was 8.4 years
When accounting for repeated attempts using closed reduction alone,
Ehmer sling, or hobbles, eventual success rate increased to 10.3%, 18.5% and
61.8%, respectively (therefore consdier repeat closed reduction with hobbles)

Reluxation (11.8%)

Closed reduction with hobbles was successful in 61.8% of cases

Case numbers treated
by transarticular pinning and ventral capsulorrhaphy were very low, so comparison of clinical outcomes of
different surgical treatments was challenging.

A ventral approach, recently
reported by some of the authors, preserves the dorsal hip stabilizers while allowing assessment and primary repair/
augmentation of the ventral joint capsule, ligament of the femoral head and transverse acetabular ligament.

only 2/108 dogs showing
evidence of radiographically detectable osteoarthritis. As the majority of dogs with significant laxity develop osteoarthritis changes, this is suggestive, but not conclusive evidence, that dogs suffering CvH are not predisposed to hip dysplasia

The authors
theorize that dogs that luxate at a younger age may have
more severe underlying conformational or functional hip
abnormalities, such as deficient transverse acetabular ligament
predisposing to CvHL,

Increasing age, hobbles placement and treatment by specialist surgeons were statistically significant protective factors

Question 45

Total hip arthroplasty to address chronic hip luxation with pseudoacetabulum formation in seven dogs
Jones 2019

Answer 45

Retrospective, case-controlled study.
Animals: Seven dogs with pseudoacetabulum (group 1) and 21 matched control
dogs (group 2).
All dogs were treated by cementless (BioMedtrix BFX)
pseudoacetabulum was associated with ilial remodeling and heterotopic bone formation concentric to the luxated femoral head. Exposing the native acetabulum and reducing the prosthesis were surgically challenging. The mean (SD) operative time of dogs in group 1 (96 [18] minutes) was longer
Cup position/orientation was not different between dogs in group 1 and group 2. One intraoperative complication and two minor postoperative complications occurred in group 1 dogs. All dogs had good long-term outcomes.

complications group 1. This is well above the expected complication rate
in dogs undergoing THA with similar implants

high-volume surgeon (>120 THA/year

some of the dogs in group 1 were
noted to drag their foot during the swing phase of gait. No neurological deficits were identified in any of these dogs.
The foot dragging was transient and was probably associated with decreased hip flexion caused by abnormal coxofemoral
soft tissue tension.

concentric dorsal heterotopic ossification
around a luxated femoral head, that can help discriminate between the pseudoacetabulum case and the more classic dysplastic/osteoarthritic joint or the luxoid case

Placement of
the acetabular prosthesis at the level of the pseudoacetabulum
in man has been associated with higher rates of complications

caudal and distal retraction of the femur to develop appropriate exposure to the true acetabulum was found to be a significant challenge. cups were placed by
hand and then impacted incrementally by using the CFX femoral stem impactor and mallet. significant tension and leverage was required to fatigue the
periarticular soft tissues and enable appropriate reduction
of the prosthesis

Strategies such as placing the acetabular cup
more dorsally or medially, creating a more distal femoral
osteotomy, and/or distalization of the femoral component
can be employed to assist in overcoming tension and thus
facilitating reduction of the prosthesis

It has been shown in man that acute
limb lengthening, by relocating the chronically luxated
femur distally by greater than 2.7 cm, increases the risk of
peroneal nerve palsy.29 No nerve deficits were detected in
any dog in this study

aseptic acetabular cup loosening, which can occur years after
implantation. A longer follow-up period would be required