Background: Fractures of the diaphyseal region account for roughly half of all feline long-bone lesions; however, evidence regarding the mechanical performance of alternative fixation systems remains limited. The paraosseous clamp-cerclage stabilization technique (PCCS) is used in cats because its low implant profile suits the small feline tibia, but its behavior under torsional loading-and in comparison with external skeletal fixators (ESF)-has not been previously evaluated.
Aims and objectives: To compare the torsional stiffness of PCCS with two acrylic ESF constructs (Type Ia and Type II) in a feline tibial fracture model.
Materials and methods: Fourteen paired tibiae with intact fibulae from adult cats were collected postmortem. A 5-mm mid-diaphyseal osteotomy was created in each specimen. PCCS was applied to the right tibia of 12 pairs; the contralateral tibiae received ESF Type II. A second cohort of paired limbs was instrumented with ESF Type Ia. Each construct underwent biomechanical testing three times under an axial preload of 0.5 N. Specimens were rotated ±15° at 10° min-1, torque-rotation curves were recorded, and torsional stiffness (Nm/°) was calculated from the linear region. Intact tibiae (n = 4) served as native controls.
Results: Twenty-four osteotomized tibiae were analyzed. Mean torsional stiffness was 0.114 Nm/° for ESF Type II, 0.049 Nm/° for PCCS, and 0.045 Nm/° for ESF Type Ia, compared with 0.264 Nm/° in native bone. ESF Type II retained 43.2% of intact stiffness, whereas PCCS and ESF Type Ia each retained approximately 18%. Coefficients of variation were 0.12 (ESF Type II), 0.18 (ESF Type Ia), and 0.52 (PCCS), indicating greater reproducibility for the fixator constructs. ESF Type II was significantly stiffer than PCCS and ESF Type Ia (P < 0.01).
Conclusion: PCCS and ESF Type Ia provide comparable but relatively low torsional rigidity, making them suitable for simple, non-comminuted fractures but likely insufficient for stabilizing large segmental defects. ESF Type II provides substantially greater torsional stability, approaching half that of intact bone, and may therefore be more appropriate for bridging comminuted fractures where minimizing interfragmentary strain is essential for bone healing. Selecting the fixation method according to the required torsional stability may help optimize clinical outcomes in feline fracture management.
