Restoration of wrist biomechanics after long-segment ballistic radius metaphyseal injury complicated by chronic osteomyelitis – peg-in-cup osteosynthesis

Large segmental bone defects resulting from trauma, infection, or tumor resection present major reconstructive challenges due to four key factors: (1) loss of structural bone support, accompanied by progressive soft tissue contraction, complicates the maintenance of limb length and alignment; (2) difficulty in preserving normal joint biomechanics, particularly in the distal radius where radiocarpal and radioulnar relationships are critical; (3) compromised vascularity and soft tissue deficits increase the risk of nonunion and infection; and (4) the lack of commercially available fixation constructs for extreme segmental bone loss. We describe a novel reconstruction using peg-in-cup osteosynthesis combined with a vascularized fibular free flap to address all these challenges in a patient with a distal forearm shotgun injury, complicated by chronic osteomyelitis, who was referred to us after failed internal fixation and Masquelet reconstruction. In the first stage of our reconstruction, following debridement and hardware removal, the patient was left with a 17 cm radius defect. Limb length and soft tissue tension were maintained with an external fixator spanning from the second metacarpal to the proximal radius. During the second stage, distal wrist biomechanics were restored using peg-in-cup osteosynthesis of the fibular free flap, with the distal radius as the “cup” and the fibula as the “peg,” allowing stable fixation despite minimal distal bone stock. Proximally, a step-ladder osteotomy increased bone-to-bone contact and enhanced stability. At 4 months post-reconstruction, the flap remained viable with strong Doppler signals. Radiographs demonstrated restoration of ulnar variance, volar tilt, radial height, and inclination to normal ranges, with callus formation at both junction sites.