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 injury might occur in conjunction with ventrocaudal luxation of the hip?

Answer 5

Avulsion fracture of the greater trochanter.

Question 6

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

Answer 6

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

Question 7

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

Answer 7

External rotation and adduction.

Patients with caudoventral luxation typically hold the limb internally rotated and abducted.

Question 8

What are some clinical findings associated with craniodoral hip luxation?

Answer 8

1. Shortening of the limb.
2. Adduction and external rotation of the hip.
3. Assymetry of the hips.
4. Increased distance between the greater trochanter and the ischiatic tuberosity, and failure to ‘push-out’ a thumb placed in the ischiatic notch during external rotation of the femur.
5. Crepitus of the hip joint.
6. Proximal displacement of the greater trochanter in relation to a line between the craniodorsal iliac spine and the ischiatic tuberosity.

Question 9

Within what timeframe should coxofemoral luxation ideally be treated?

Answer 9

72 hours

Question 10

When should immediate open reduction of hip luxation be considered?

Answer 10

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 11

If a hip joint is dysplastic should closed reduction be attempted?

Answer 11

No - ideally FHO or THR are performed.

Question 12

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

Answer 12

50%.

Most likely to occur with external rotation of the hip or hip extension for craniodorsal luxations. Dysplastic and chronically luxated hips also at increased risk of re-luxation.

Question 13

What is the function of the Ehmer sling?

Answer 13

Internal rotation and abduction of the femur, flexion of the hip joint. Should be kept in place for 10-14 days.

Question 14

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

Answer 14

15 - 71%

Question 15

What is the function of hobbles?

Answer 15

To prevent limb abduction following closed hip reduction for ventrocaudal luxation.

Question 16

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

Answer 16

80%

Question 17

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

Answer 17

Ischioilial pinning, ESF, transarticular pinning

Question 18

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

Answer 18

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 19

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

Answer 19

73%

Question 20

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

Answer 20

85%

Question 21

What approach to the hip joint is used for dorsal and ventral luxations?

Answer 21

Dorsal: craniolateral.
Ventral: dorsal.

Question 22

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

Answer 22

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 23

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

Answer 23

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

Question 24

What technique may be combined with capsulorrhaphy to potentially help maintain hip reduction?

Answer 24

Deep gluteal tenodesis.

Question 25

How is the prosthetic capsule technique performed?

Answer 25

Screws and washers or bone anchors are placed in the acetabulum and suture is passed in a figure of eight pattern around the screws and through a hole in the femoral neck.

Question 26

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

Answer 26

66 - 100%

Question 27

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

Answer 27

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

Question 28

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

Answer 28

84%

Question 29

What are the two methods of transarticular pinning?

Answer 29

Normograde or retrograde (if performed open). The pin is left in place for 2-3 weeks.

Question 30

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

Answer 30

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 31

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

Answer 31

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

Question 32

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

Answer 32

It resulted in cartilage damage in 20% of cases.

Question 33

What is one of the main advantages of use of toggle rod for maintaining hip reduction?

Answer 33

Allows early use of the limb post-operative, which may be required in patients with additional orthopedic injuries.

Question 34

Why is closed application of toggle rod using fluoroscopy not currently recommended?

Answer 34

Resulted in cartilage damage in 20% of cases.

Question 35

What are some materials that have been used in toggle-rod stabilization of hip luxation?

Answer 35

Woven polyester, monofilament nylon, and FiberWire. The Tightrope system has also been used for Toggle rod.

Question 36

What techniques can be combined with toggle rod stabilization of the hip?

Answer 36

Capsulorrhaphy, prosthetic capsule technique, transposition of the greater trochanter.

Question 37

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

Answer 37

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

Question 38

What are some complications reported with the use of toggle rod repair for hip luxation?

Answer 38

Premature suture failure; joint reluxation; injury to the rectum; sciatic nerve damage; articular cartilage damage; and transient lameness.

Question 39

What is fascia lata loop stabilization for repair of hip reduction?

Answer 39

Similar to toggle rod fixation except that fascia lata rather than suture material is used.

Question 40

What is transposition of the sacrotuberous ligament for repair of hip reduction?

Answer 40

Similar to the toggle rod except the sacrotuberous ligament is used. It is detached from its attachment on the ischium, including a piece of bone. It is then passed from medial to lateral through the acetabular and femoral head bone tunnels, and attached to the femur using a bone screw.

Question 41

Where is the suture passed in for extra-articular iliofemoral suturing of the hip, to prevent coxofemoral luxation?

Answer 41

From the ilium just cranial to the acetabulum, through a hole drilled caudal to cranial through the femur just distal to the insertions of the gluteal muscles.

Question 42

What are reported surgical options for ventral hip luxation?

Answer 42

Prosthetic capsule or toggle rod +/- (if necessary) ventral augmentation. This may include: 1) Suturing of ventral acetabular ligament 2) Autogenous iliac crest shelf graft. 3) Extracapsular sling 4) internal fixator plate to augment the ventral acetabular rim. Trochanteric transposition is not recommended.

Question 43

Is progression of osteoarthritis common after closed or open hip reduction?

Answer 43

Yes - progresses in 55-62% of dogs and is more severe in heavier patients.

Question 44

Asides from closed or open coxofemoral reduction techniques, what other surgeries might be indicated in the treatment of coxofemoral luxation?

Answer 44

1. FHO 2. TPO 3. THR

Question 45

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 45

Decreased risk when the luxation was traumatic in nature, and the lameness was severe at presentation. Overall rate of reluxation was 15%.

Question 46

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 46

Reluxation was the most common complication (11.1% of cases). Performance of additional orthopedic procedures, occurrence of intraoperative complications, and non-performance of capsulorrhaphy were associated with reluxation.

Question 47

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

Answer 47

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

Question 48

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 48

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 49

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 49

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 50

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 50

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.

Question 51

In a study by LeFloch 2022 in JFMS, what was the success rate for cats undergoing closed hip reduction? What reduced the risk of reluxation?

Answer 51

51% Application of a bandage (either Ehmer sling or hobbles) reduced the risk of reluxation.