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Hanlon et al: Mechanical evaluation of canine sacroiliac joint stabilization using two short screws
Veterinary Surgery 7, 2022

🔍 Key Findings

  • Two short screws (SLS or SPS) provided >2× peak load, yield load, and stiffness vs a single long screw (LLS) for SI joint stabilization.
  • No mechanical advantage was seen between the two short screw types (lag vs positional).
  • All short screws terminated lateral to the spinal canal, avoiding spinal impingement.
  • Ventral sacral foraminal impingement occurred in 3 short-screw cases (1 SPS, 2 SLS), all involving the caudal screw.
  • LLS group showed more abaxial displacement at osteotomy sites, suggesting inferior stabilization for concurrent pelvic fractures.
  • Short screw constructs had longer total screw length (48 mm) than LLS (40 mm), contributing to increased stiffness.
  • Positioning of caudal screw in a cranial/craniodorsal trajectory may help avoid nerve foraminal injury.
  • No significant difference in displacement at peak load among groups; stiffness and load capacity were the primary benefits.

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← Articles

Hanlon et al: Mechanical evaluation of canine sacroiliac joint stabilization using two short screws
Veterinary Surgery 7, 2022

🔍 Key Findings

  • Two short screws (SLS or SPS) provided >2× peak load, yield load, and stiffness vs a single long screw (LLS) for SI joint stabilization.
  • No mechanical advantage was seen between the two short screw types (lag vs positional).
  • All short screws terminated lateral to the spinal canal, avoiding spinal impingement.
  • Ventral sacral foraminal impingement occurred in 3 short-screw cases (1 SPS, 2 SLS), all involving the caudal screw.
  • LLS group showed more abaxial displacement at osteotomy sites, suggesting inferior stabilization for concurrent pelvic fractures.
  • Short screw constructs had longer total screw length (48 mm) than LLS (40 mm), contributing to increased stiffness.
  • Positioning of caudal screw in a cranial/craniodorsal trajectory may help avoid nerve foraminal injury.
  • No significant difference in displacement at peak load among groups; stiffness and load capacity were the primary benefits.

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Multiple Choice Questions on this study

In Hanlon 2022 et al., on short screw sacroiliac fixation, what intraoperative consideration may reduce foraminal trauma?

A. Use of longer screws
B. Placement through the sacral body
C. Caudal screw placed in cranial/craniodorsal direction
D. Use of fully threaded screws
E. Fluoroscopy-free placement

Answer: Caudal screw placed in cranial/craniodorsal direction

Explanation: Authors noted this trajectory may reduce ventral sacral foraminal impingement.
In Hanlon 2022 et al., on short screw sacroiliac fixation, what complication was observed in some short screw cases?

A. Ventral spinal canal violation
B. L7-S1 disc penetration
C. Iliac fracture at screw entry
D. Ventral sacral foraminal impingement
E. Pelvic canal collapse

Answer: Ventral sacral foraminal impingement

Explanation: Three cases (1 SPS, 2 SLS) had caudal screws impinging the ventral sacral foramina.
In Hanlon 2022 et al., on short screw sacroiliac fixation, what was the mechanical advantage of using two short screws versus one long screw?

A. Peak load and stiffness were more than doubled with two short screws
B. Yield load was lower with short screws
C. There was no mechanical difference between short and long screw techniques
D. Short screws caused significant spinal canal impingement
E. Short screws had inferior fixation strength

Answer: Peak load and stiffness were more than doubled with two short screws

Explanation: Two short screws (SLS and SPS) produced >2× peak load, yield load, and stiffness compared to a single long screw.
In Hanlon 2022 et al., on short screw sacroiliac fixation, how did screw positioning affect neurovascular safety?

A. All screws impinged the spinal canal
B. Short screws terminated lateral to the spinal canal
C. Short screws had higher incidence of nerve impingement
D. Spinal canal violation was common in the LLS group
E. Only the lag screw technique caused foraminal trauma

Answer: Short screws terminated lateral to the spinal canal

Explanation: All short screws were located lateral to the spinal canal, avoiding this risk entirely.
In Hanlon 2022 et al., on short screw sacroiliac fixation, what was the difference in mechanical performance between short lag and short positional screws?

A. Short lag screws were significantly stronger
B. Short positional screws had higher yield load
C. Short lag screws were stiffer
D. No mechanical difference was observed
E. Short screws failed earlier than long screws

Answer: No mechanical difference was observed

Explanation: No statistical difference in mechanical performance (stiffness, peak, or yield load) was found between SLS and SPS.

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