Optimal Forearm Position Allowing Maximum Hand Function: A Quasi-experimental Study in Adolescent Children
Abstract
A functional simulation study determining the ideal angle of fusion for one-bone forearm salvage procedures. Using 3D-printed braces and standardized testing, the study defines the optimal position for unilateral vs. bilateral forearm arthrodesis.
The One-Bone Forearm Blueprint
Key Finding
"For unilateral fusion, the mid-prone position yielded the highest functional scores; for bilateral fusion, the dominant limb should be mid-prone and the non-dominant limb in 45° supination."
Background: Creating a one-bone forearm (radio-ulnar synostosis) is a salvage procedure for severe instability or bone loss. While it restores a stable lever arm, it sacrifices all rotation. Historical recommendations for the position of fusion varied wildly from pronation to supination, with no data accounting for modern functional demands like typing or smartphone usage.
Methods: 15 healthy adolescents underwent testing using a custom 3D-printed adjustable brace that locked the forearm in 5 discrete positions (Full Supination to Full Pronation). Participants performed the Sollermans Hand Function Test, modified to include modern tasks (typing, smartphone use). Both dominant and non-dominant limbs were tested individually and simultaneously to simulate bilateral salvage.
Results: The mid-prone (neutral) position consistently produced the highest mean functional scores for unilateral cases (Score ~82/100), regardless of limb dominance. Full supination significantly degraded performance (p = 0.002). However, in bilateral simulations, fixing the non-dominant arm in 45° supination (while keeping the dominant arm mid-prone) optimized bimanual tasks and personal hygiene without compromising grip strength.
Conclusion: Surgeons performing forearm arthrodesis should target the mid-prone position for all unilateral cases. In the rare devastating event of bilateral salvage, an asymmetric strategy (Dominant: Neutral / Non-Dominant: 45° Supination) provides the best balance between world-interaction (typing/eating) and self-care (hygiene).