Issues

Joint Luxations

 

DEFINITION

Luxation is the complete disruption of the contiguous articular surfaces of a joint when the supporting structures around the joint are damaged or missing. Subluxation is a partial disruption.

 

PATHOPHYSIOLOGY

All synovial joints have a joint capsule that joins the articulating bones together. The fibrous layer of this capsule is a primary stabilizer of the joint. Most joints have additional ligaments that reinforce the joint capsule to improve the resistance to movement outside of the normal range of motion of that joint. All motion joints also have a system of muscles and tendons that exert forces on the joint to control movement. The co-contraction forces around a joint are very influential on the stability of that joint. Instability occurs when the stabilizing system is damaged or disrupted or does not develop normally.

If the laxity is clinically apparent, then the situation is generally described as luxation or subluxation of that joint.

Luxation may occur as a result of traumatic forces causing the joint to move beyond the elastic limits of the supporting tissues.

Secondary changes are set in motion by the damage to the tissues that create early, and then later, more chronic joint damage.

 

SYSTEMS AFFECTED

Musculoskeletal—primarily the intra-articular environment and the support structures around the joint including joint capsule, collateral ligaments, and support muscle/tendon units.

Neurologic—neurologic feedback and supply to the support system may also be affected.

GENETICS

Hyper laxity syndrome is an inherited factor in humans. Puppies may show temporary hyper laxity when confined.

Hip dysplasia is a form of inherited laxity of the hip joint.

Shoulder luxation is an inherited predisposition in small breeds such as miniature poodles.

Femoropatellar instability leading to medial patellar luxation is a common inherited disease in small-breed dogs.

Ehlers-Danlos syndrome is a congenital collagen disorder that leads to joint laxity.

INCIDENCE/PREVALENCE

Some forms of laxity/luxation (hip dysplasia and medial patella luxation) are very common.

 

GEOGRAPHIC DISTRIBUTION

None observed

 

SIGNALMENT

Breed Predilections

Varies with the joint affected.

Hip—large breeds show clinical signs of hip dysplasia more frequently than smaller breeds, but breeds of all sizes can have radiographic signs.

Traumatic luxations are not breed-specific in any joint.

Congenital shoulder luxation occurs most commonly in miniature breeds (poodle).

Stifle luxation most commonly involves rupture of both cruciate ligaments and one of the collateral ligaments.

Medial patella luxation is more common in small-breed dogs.

Spinal luxations occur as a result of trauma, with associated injury to the spinal cord.

Mean Age and Range

Traumatic—any age.

Congenital laxity/luxation is typically seen in the juvenile dog, with secondary degenerative joint disease showing later in life.

Predominant Sex

None

 

SIGNS

Abnormal anatomic position of one bone in relation to the adjoining bone.

Hip luxation is commonly cranio-dorsal (the displacement of the femoral head in relation to the acetabulum).

Shoulder luxation is commonly medial.

Elbow luxation is commonly proximo-lateral.

Carpal and tarsal luxations commonly result in varus, valgus, or hyperextension when stressed.

Acute swelling, pain, and non-use of the limb are usually seen with acute luxation. Partial weight-bearing may occur with subluxation or chronic luxation.

 

CAUSES

Traumatic displacement of normal tissues beyond their elastic limit.

Minimal stress on abnormally unstable joints of congenital etiology.

RISK FACTORS

Abnormal conformation, causing elevated joint stresses

Fatigue, causing muscle weakness and incoordination

Neurologic abnormalities

Access to moving vehicles

 

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS

Fractures

Joint disease—immune-mediated, septic, or degenerative

 

CBC/BIOCHEMISTRY/URINALYSIS

No abnormalities expected that are directly related to the luxation.

Trauma-induced abnormalities in traumatic situations.

OTHER LABORATORY TESTS

Arthrocentesis may eliminate non-traumatic joint disease.

 

IMAGING

Radiographs confirm the diagnosis by documenting the anatomic malalignment.

Stress views may be needed in some situations.

DIAGNOSTIC PROCEDURES

Palpation of the laxity/luxation (Ortolani, cranial drawer, medial patella luxation, stress-induced laxity/instability).

Palpation of the position of the displaced bone.

PATHOLOGIC FINDINGS

Trauma-induced hemorrhage, edema, and disruption of ligaments and joint capsule.

Secondary changes related to degenerative joint disease.

treatment TREATMENT

APPROPRIATE HEALTH CARE

Rest, reduce mobility, reduce swelling, control pain, and stabilize the joint or salvage the limb by removing the source of pain.

 

NURSING CARE

Immobilize the joint with a bandage/splint if the affected joint is distal to the inguinal or axial areas.

Cold compresses for 5–10 minutes four or five times a day initially to reduce inflammation.

ACTIVITY

Cage rest until joint stabilization, then slow return to function to encourage healing and strengthening of soft tissue support of the limb.

 

DIET

Normal

 

CLIENT EDUCATION

Activity and weight gain increase the likelihood of degenerative changes in the long term.

 

SURGICAL CONSIDERATIONS

Closed reduction under anesthesia may be successful if the support structures are intact and no anatomic aberrations are present. This method is generally not recommended for the hock, carpus or stifle.

Failing closed reduction, an open surgical approach may be used. After reduction, some form of surgical stabilization (e.g., toggle pin for hip luxation) should be applied to reduce the possibility of reluxation. After surgical closure, an external support sling is often used to limit movement until the tissues around the joint have healed (e.g., Ehmer sling after cranio-dorsal hip luxation reduction, spica splint after elbow luxation reduction).

The incidence of reluxation is high, especially in the case of congenital luxations.

Salvage procedures include prosthetic joint replacement, surgical removal of bone-to-bone contact points (femoral head and neck ostectomy), arthrodesis, and amputation.

 

MEDICATIONS

DRUG(S) OF CHOICE

• NSAIDs decrease prostaglandin synthesis by inhibiting cyclooxygenase enzymes:
• Carprofen (2.2 mg/kg PO or SC q12h, or 4.4 mg/kg PO or SC q24h).
• Deracoxib (1–2 mg/kg PO q24h).
• Firocoxib (5 mg/kg PO q24h).
• Meloxicam (0.1 mg/kg PO or SC q24h).
• Tramadol (1–4 mg/kg PO q8–12h)
• Serotonin reuptake inhibitor, in combination with NSAID.

 

CONTRAINDICATIONS

Gastrointestinal sensitivity

Liver or renal pathology

 

PRECAUTIONS

Stop medications if diarrhea or vomiting is seen.

 

POSSIBLE INTERACTIONS

Other NSAIDs

Steroids

 

ALTERNATIVE DRUG(S)

Analgesics

 

FOLLOW-UP

PATIENT MONITORING

Always take a radiograph after reduction.

Take follow-up radiographs when the splint/sling is removed (typically 2–4 weeks post-reduction).

PREVENTION/AVOIDANCE

Fenced-in yards

Keep the sling in place until healing has occurred

 

POSSIBLE COMPLICATIONS

Reluxation

Infection after surgery

Implant failure of joint prosthetic

 

EXPECTED COURSE AND PROGNOSIS

Return of function is expected unless a complication occurs.

The high incidence of reluxation makes the prognosis guarded.

Progressive degenerative joint disease.

 

MISCELLANEOUS

SYNONYMS

Dislocation

 

Visit your veterinarian as early recognition, diagnosis, and treatment are essential.

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