Kinematic Analysis of Sagittal Plane Stability of Delta Frame External Fixation




Beck, Cameron
Tran, Apollo
Hoy, Austin
Barcak, Eric


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Purpose: External fixation with a delta frame construct is the most common construct used for temporizing patient distal tibia and ankle injuries. While these constructs may be the most common there are numerous variations that are often performed based on surgeon preference. The inclusion or exclusion of a posterior slab or 1st metatarsal pin to the construct is variable amongst surgeons and have little data to support their use aside from anecdotal evidence. Methods: 10 Fresh Frozen Cadavers were secured to a custom-made rig that held the tibia rigid and allowed the application of a standard delta frame external fixator. The specimens had a 2 cm segment of bone resected near the ankle plafond to simulate a highly unstable distal tibia or pilon fracture. The ankle was then loaded with a 10 lb weight from the great toe and 3D kinematics were recorded using an electromagnetic tracking system with 6 degrees of freedom. The 4 construct comparisons were: 1. Delta frame 2. Delta frame with 1st metatarsal pin 3. Delta frame with posterior slab 4. Delta frame with 1st metatarsal pin and posterior slab Results: The delta frame construct without any additions was less stable than all other constructs with statistical significance in the sagittal plane with regards to flexion/extension rotation. The most stable construct was a delta frame with 1st metatarsal pin and posterior slab. The most cost-effective measure to add sagittal plane stability was the addition of the posterior slab splint. Conclusion: Delta frame stability in the sagittal plane can be cost effectively augmented by the addition of a posterior slab. The addition of both a posterior slab or 1st metatarsal pin were able to significantly add stability to the base construct and the combination of the 2 were able to achieve highest stability.