Biomechanical Comparison between Volar Plate Fixator and Nonbridge External Wrist Fixator

Intra-articular distal radius fractures are difficult to reduce and maintain by nonoperative means. ORIF leaves implants in the patient long after the fracture is healed. External fixation can stabilize the reduced fracture and leaves no long-term implants. The nonbridging fixator (NBX) will provide better reduction and comparable rigidity of fixation to a volar plate for a 5-fragment, OTA 23 C3.2 distal radius fracture. A 5-part distal radius fracture was created in 5 pairs of cadaver arms. One arm was randomly fixed with the NBX fixator; the matched pair was fixed with a volar plate (VPS). Fluoroscopic images recorded the extremes of passive volar-dorsiflexion range of motion (ROM) and radial-ulnar deviation ROM. Each arm was loaded with an axial force at a constant displacement rate until failure. The average reduction of radial tilt achieved for the NBX group was 13.8 ± 4.8° and 6.3 ± 4.7° for VPS; radial length: 3.4 ± 3.7 mm for NBX and 1.9 ± 1.0 mm for VPS; volar tilt: 26.3 ± 12.4° for NBX and 14.0 ± 13.5° for VPS. For NBX, ROM was slightly less after fixation than before fracture. ROM with volar plating was greater after fracture. The peak axial load for NBX was 925 ± 445 N; for VPS, 2,152 ± 1023 N. NBX had minimal effect on ROM and provided adequate strength and restoration of alignment at least as good as VPS for this 5-part fracture model.