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Welsh et al: Biomechanical comparison of one pin versus two pin fixation in a canine tibial tuberosity avulsion fracture model
Veterinary Surgery 5, 2023

🔍 Key Findings

  • Two-pin fixation had significantly greater strength (639 N) than single-pin fixation (426 N) in TTAF models (p = .003).
  • Stiffness was also higher with two-pin constructs (72 N/mm vs 57 N/mm); statistically significant (p = .029).
  • Both fixation types withstood loads greater than quadriceps force in dogs at a walk (240 N), indicating clinical viability.
  • Failure was most commonly due to pin bending or pullout (82%), with fewer cases of ligament tearing or epiphyseal fracture.
  • K-wire insertion angle (KWIA) did not significantly differ between fixation types (p = .13).
  • Single larger pins delivered ~68% of the strength and ~83% of the stiffness of two smaller vertically aligned pins.
  • Clinical implication: Two vertically aligned pins are biomechanically superior for TTAF fixation in canine models.
  • Study used mature cadavers, which may underestimate loads and stiffness compared to immature clinical cases.

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← Articles

Welsh et al: Biomechanical comparison of one pin versus two pin fixation in a canine tibial tuberosity avulsion fracture model
Veterinary Surgery 5, 2023

🔍 Key Findings

  • Two-pin fixation had significantly greater strength (639 N) than single-pin fixation (426 N) in TTAF models (p = .003).
  • Stiffness was also higher with two-pin constructs (72 N/mm vs 57 N/mm); statistically significant (p = .029).
  • Both fixation types withstood loads greater than quadriceps force in dogs at a walk (240 N), indicating clinical viability.
  • Failure was most commonly due to pin bending or pullout (82%), with fewer cases of ligament tearing or epiphyseal fracture.
  • K-wire insertion angle (KWIA) did not significantly differ between fixation types (p = .13).
  • Single larger pins delivered ~68% of the strength and ~83% of the stiffness of two smaller vertically aligned pins.
  • Clinical implication: Two vertically aligned pins are biomechanically superior for TTAF fixation in canine models.
  • Study used mature cadavers, which may underestimate loads and stiffness compared to immature clinical cases.

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Multiple Choice Questions on this study

In Welsh 2023 et al., on TTAF fixation methods, which failure mode was **most common** in both groups during mechanical testing?

A. Patellar ligament rupture
B. Implant infection
C. Epiphyseal fracture
D. Pin bending and pullout
E. Physeal closure

Answer: Pin bending and pullout

Explanation: 82% of failures were due to pin bending and pullout in both fixation groups.
In Welsh 2023 et al., on TTAF fixation methods, what was the estimated quadriceps force at a walk used as a benchmark for load testing?

A. 150 N
B. 200 N
C. 240 N
D. 300 N
E. 400 N

Answer: 240 N

Explanation: 240 N was cited as the estimated quadriceps force during walking, used to benchmark construct strength.
In Welsh 2023 et al., on TTAF fixation methods, which of the following variables did **not significantly differ** between single- and two-pin constructs?

A. Construct stiffness
B. Construct strength
C. Kirschner wire insertion angle (KWIA)
D. Load to failure
E. Normalized stiffness

Answer: Kirschner wire insertion angle (KWIA)

Explanation: The KWIA values were not statistically different between groups (p = .13).
In Welsh 2023 et al., on TTAF fixation methods, what was the primary mechanical benefit of two-pin fixation over single-pin fixation?

A. Greater pin insertion angle
B. Lower KWIA variance
C. Improved stiffness and strength
D. Reduced surgical time
E. Lower implant migration

Answer: Improved stiffness and strength

Explanation: Two-pin fixation had significantly greater stiffness (72 N/mm) and strength (639 N) than single-pin fixation (57 N/mm and 426 N).
In Welsh 2023 et al., on TTAF fixation methods, what approximate % of the **strength** did the single-pin construct achieve compared to two-pin fixation?

A. 45%
B. 59%
C. 68%
D. 82%
E. 96%

Answer: 68%

Explanation: Single-pin constructs had a mean strength that was 68% of that provided by two-pin fixation.

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