Hip luxation

Question 1

What are the primary and secondary stabilizers of the hip joint?

Answer 1

Primary: ligament of the head of the femur, joint capsule, dorsal acetabular rim.

Secondary: Acetabular labrum (transverse ligament ventrally), hydrostatic pressure, periarticular muscles (gluteals, iliopsoas, quadratus femoris, gemelli, internal and external obturator).

Question 2

How many of the primary stabilizers of the hip need to be disrupted for luxation to occur?

Answer 2

Two (out of 3)

Question 3

True or false. In immature dogs fractures of the capital physis are less likely to occur than hip luxation?

Answer 3

False

Question 4

What percentage of hip luxations are craniodorsal?

Answer 4

75%

Question 5

What is the function of the gluteal muscles on the hip joint?

Answer 5

Extension of the hip joint, with internal rotation and abduction of the femur

Question 6

How do patients with craniodorsal hip luxation typically hold the affected pelvic limb?

Answer 6

External rotation and adduction

Question 7

Within what timeframe should coxofemoral luxation ideally be treated?

Answer 7

72 hours

Question 8

When should immediate open reduction of hip luxation be considered?

Answer 8

Acetabular or femoral head fractures, reluxation after closed reduction, concurrent injuries that require immediate return of hip joint function, chronic luxation requiring assessment of the joint cartilage

Question 9

Reluxation of the hip occurs in what percentage of patients following closed reduction?

Answer 9

50%

Question 10

What is the function of the Ehmer sling?

Answer 10

Internal rotation and adduction of the femur, flexion of the hip joint.

Question 11

What is the reported rate of reluxation rate following Ehmer sling application alone after closed reduction?

Answer 11

15 - 71%

Question 12

What is the success rate of closed reduction of ventral hip luxations without the use of hobbles?

Answer 12

80%

Question 13

Aside from use of an Ehmer sling and hobbles, what other augmentation techniques are available following hip coxofemoral reduction?

Answer 13

Ischioilial pinning, ESF, transarticular pinning

Question 14

What is the complication rate of ischioilial pinning for maintenance of closed hip reduction?

Answer 14

32% (contact with sciatic nerve in 75% of cases when the pin is inserted in the center of the ischium). These include; pin migration, reluxation, sciatic nerve injury, damage to the femoral head, joint sepsis.

Question 15

What is the success rate of ischioilial pinning in preventing hip reluxation?

Answer 15

73%

Question 16

What is the success rate following open surgical reduction of hip luxation?

Answer 16

85%

Question 17

Name 8 surgical techniques that may be used for open reduction of hip luxation.

Answer 17

1. Capsulorrhaphy
2. Prosthetic joint capsule
3. Transposition of the greater trochanter
4. Transarticular pinning
5. Toggle rod
6. Fascia lata loop stabilization,
7. Transposition of the sacrotuberous ligament
8. Extra-articular iliofemoral suture.

Question 18

What is the reported success rate of capsulorrhaphy for open hip reduction?

Answer 18

83 - 90%, however may not be possible if the joint capsule is severely damaged

Question 19

In what percentage of cases is the prosthetic capsule technique reported to prevent hip reluxation?

Answer 19

66 - 100%

Question 20

What are some complications associated with the prosthetic capsule technique for open hip reduction?

Answer 20

Damage to the articular cartilage, reluxation through the web of suture material, displacement of the suture from the screw heads, infection.

Question 21

In what percentage of cases is transposition of the greater trochanter reported to prevent hip reluxation?

Answer 21

84%

Question 22

What is the reported success rate of transarticular pinning for open hip reduction?

Answer 22

80% at maintaining joint reduction. However results are worse in heavier dogs or patients with pre-existing hip dysplasia (unsatisfactory outcomes in 40% of patients weighing >20%)

Question 23

What are some complications of transarticular pinning for open hip reduction?

Answer 23

Cartilage damage, sciatic nerve injury, pin migration, perforation of the rectum, pin bending or breakage, OA.

Question 24

Why is closed application of a toggle rod with the use of fluoroscopy no longer recommended?

Answer 24

It resulted in cartilage damage in 20% of cases.

Question 25

What is the reported rate of reluxation following toggle rod fixation?

Answer 25

6% (81% of dogs had little or no long term lameness)

Question 26

What are reported surgical options for ventral hip luxation?

Answer 26

Prosthetic capsule or toggle rod +/- (if necessary) suturing of ventral acetabular ligament, autogenous iliac crest shelf graft, extracapsular sling, internal fixator plate to augment the ventral acetabular rim.

Question 27

According to Mathews 2020 in Vet Surg, what were two risk factors for hip reluxation following toggle rod stabilization? What was the overall rate of reluxation?

Answer 27

Decreased risk when the luxation was traumatic in nature, and the lameness was severe at presentation.

Overall rate of reluxation was 15%.

Question 28

In a study by Ruperez 2021 in Vet Surg what was the most common post-operative complication following toggle rod repair of feline hip luxation? What 3 factors were associated with an increased risk of this complication?

Answer 28

Reluxation was the most common complication (11.1% of cases).

Performance of additional orthopedic procedures, occurrence of intraoperative complications, and non-performance of capsulorrhahpy were associated with reluxation.

Question 29

In a study by Ruperez 2023 in Vet Surg, what were three issues identified with arthroscopic assisted hip toggle stabilization?

Answer 29

Intraoperative complications related to bone tunnel formation and toggle dislodgement, cartilage injury, and deviations in planned surgical technique.

Question 30

In a study by Loh 2024 in Vet Surg, what was the success rate of ventral hip luxation treated by closed reduction alone, closed reduction and Ehmer sling, and closed reduction and Hobbles? What 3 factors were associated with successful non-surgical treatment?

Answer 30

9%, 15%, 49%.

Factors associated with successful treatment were increasing age, treatment by a specialist, and use of Hobbles.

Additional info: most ventral hip luxations were caused by low impact trauma (83%). Success rate for toggle rod was 88%. Complication rate of hobbles was 32% (half that of Ehmer slings).

Question 31

In a study by Schalg 2019 in JAVMA, what was the rate of hip reluxation following Ehmer sling placement? What percentage of dogs had soft tissue injuries related to sling use? What were 3 factors associated with an increased risk of complication?

Answer 31

Reluxation rate was 43% (5x as likely for those patients suffering traumatic hip luxations).

50% of dogs had soft tissue injuries associated with sling use.

Three factors associated with increased risk of complications included poor owner compliance (13 x as likely), intern placing the bandage (4 x), wet or soiled (6x).

Question 32

In a study by Knell 2023 in VCOT, was use of a double or single strand mini-Tightrope system associated with a decreased risk of suture failure when used for toggle pin of feline coxofemoral luxation?

Answer 32

Double strand (1/12 cats) compared to single strand (4/16) cats had suture failure. Reluxation was the most common post-operative complication.

Osteoarthritis was common post-operative, but outcomes were generally considered excellent.