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Woelfel et al: Subaxial cervical articular process subluxation and dislocation: Cervical locked facet injuries in dogs
Veterinary Surgery 1, 2022

🔍 Key Findings

  • Locked facet injuries in dogs involved unilateral dorsal displacement of the cranial articular process of the caudal vertebra, most commonly at C5/6 or C6/7.
  • All affected dogs were small/toy breeds, typically following trauma (most often attacks by larger dogs).
  • Neurologic severity ranged from ambulatory tetraparesis to tetraplegia, often with thoracic limb deficits more severe than pelvic limbs — suggesting a central cord syndrome-like pattern.
  • CT and MRI revealed axial rotation, subluxation, and articular process displacement; MRI showed T2 hyperintensity, nerve root impingement, and soft tissue changes.
  • Surgical treatment included ventral fixation with screws, pins, and PMMA, and one case required dorsal facetectomy for reduction.
  • Medical management, including external coaptation or rest, also resulted in functional recovery in select cases.
  • All dogs with follow-up data (8/8) had functional recovery, with nonambulatory dogs regaining ambulation in a median of 4 weeks.
  • No consistent differences in outcome were observed between surgical and nonsurgical management, suggesting locked facets may be biomechanically stable.

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← Articles

Woelfel et al: Subaxial cervical articular process subluxation and dislocation: Cervical locked facet injuries in dogs
Veterinary Surgery 1, 2022

🔍 Key Findings

  • Locked facet injuries in dogs involved unilateral dorsal displacement of the cranial articular process of the caudal vertebra, most commonly at C5/6 or C6/7.
  • All affected dogs were small/toy breeds, typically following trauma (most often attacks by larger dogs).
  • Neurologic severity ranged from ambulatory tetraparesis to tetraplegia, often with thoracic limb deficits more severe than pelvic limbs — suggesting a central cord syndrome-like pattern.
  • CT and MRI revealed axial rotation, subluxation, and articular process displacement; MRI showed T2 hyperintensity, nerve root impingement, and soft tissue changes.
  • Surgical treatment included ventral fixation with screws, pins, and PMMA, and one case required dorsal facetectomy for reduction.
  • Medical management, including external coaptation or rest, also resulted in functional recovery in select cases.
  • All dogs with follow-up data (8/8) had functional recovery, with nonambulatory dogs regaining ambulation in a median of 4 weeks.
  • No consistent differences in outcome were observed between surgical and nonsurgical management, suggesting locked facets may be biomechanically stable.

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Multiple Choice Questions on this study

In Woelfel 2022 et al., on cervical locked facets, which best describes the neurologic pattern often observed?

A. Pelvic limbs more affected than thoracic limbs
B. Diffuse flaccid tetraparesis
C. Asymmetric hindlimb monoparesis
D. Thoracic limbs more affected than pelvic limbs
E. Normal neurologic function

Answer: Thoracic limbs more affected than pelvic limbs

Explanation: Half the tetraparetic dogs had greater thoracic than pelvic limb deficits, consistent with central cord-like syndrome.
In Woelfel 2022 et al., on cervical locked facets, what was the most common inciting cause?

A. Congenital instability
B. Intervertebral disc herniation
C. Chronic spinal cord disease
D. Attacks by larger dogs
E. Jumping from height

Answer: Attacks by larger dogs

Explanation: 9 out of 10 cases were due to external trauma from dog attacks.
In Woelfel 2022 et al., on cervical locked facets, what was the most consistent outcome in dogs with follow-up?

A. Persistent nonambulatory status
B. Partial improvement only in surgical cases
C. Recovery only in dogs without fractures
D. Functional recovery in most dogs regardless of treatment
E. Poor outcomes in medically managed dogs

Answer: Functional recovery in most dogs regardless of treatment

Explanation: 8/8 dogs with outcome data regained ambulation, whether treated surgically or medically.
In Woelfel 2022 et al., on cervical locked facets, which vertebral levels were exclusively affected in this case series?

A. C1–C2
B. C3–C4
C. C4–C5
D. C5–C6 and C6–C7
E. C7–T1

Answer: C5–C6 and C6–C7

Explanation: All locked facet injuries were at C5/6 or C6/7, based on imaging and intraoperative findings.
In Woelfel 2022 et al., on cervical locked facets, which imaging sign was associated with this injury on CT?

A. Vacuum sign
B. Reverse hamburger bun sign
C. Central canal narrowing
D. Schmorl’s node
E. Banana sign

Answer: Reverse hamburger bun sign

Explanation: The reverse hamburger bun sign describes loss of normal facet congruity seen on CT at the site of locked facet.

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