JHS - 2026-04-01 - Journal Article; Comparative Study
Fracture Fixation in an Unstable Scaphoid Fracture Model: A Biomechanical Comparison of Double Screw Osteosynthesis With Two Common Bone Graft and Fixation Techniques.
Surke C, Del Rosario PA, Huntington LS, Ek ETH, Tham SK, Ackland D
Topics
Key Takeaway
Double screw fixation requires 78.3 N more force to achieve 2.0 mm displacement in bending and generates 60.6–65.6 N·mm greater maximum torque than single screw plus bone graft constructs in an unstable scaphoid waist fracture model.
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Summary
This study compared torsional and cantilever bending strength of double screw fixation versus single screw with strut graft or wedge graft in a cadaveric volar open wedge osteotomy model of unstable scaphoid waist fractures (n=48, 16 per group). Double screw constructs demonstrated significantly greater load to 2.0 mm displacement (mean difference 78.3 N over both single screw groups) and greater maximum torque in the screw tightening direction (65.6 N·mm vs. strut group; 60.6 N·mm vs. wedge group). Double screw fixation also showed higher maximum rotational stiffness compared to both bone graft groups (4.8 and 9.3 N·mm/deg, respectively).
Key Limitation
The osteotomy model simulates volar bone loss but does not replicate the variable fracture geometry, bone quality, and soft tissue envelope of clinical unstable scaphoid nonunions, limiting direct translation of force thresholds to in vivo performance.
Original Abstract
PURPOSE
Rotational instability is an important contributor to nonunion in scaphoid waist fractures treated with a single compression screw. Double screw osteosynthesis demonstrates enhanced resistance to bending loads in unstable fracture models. This method may also provide better rotational strength, improving the construct's resistance to higher loads. This study aimed to evaluate and compare the torsional and cantilever bending strength of double screw fixation against single screw repairs combined with a strut graft and a wedge graft.
METHODS
Volar open wedge osteotomies were performed on 48 cadaveric scaphoids using customized surgical guides. Each specimen was randomly allocated to one of three treatment groups: (1) a single screw with strut graft, (2) a single screw with wedge graft, and (3) double screw fixation. Constructs underwent bending or torsion testing to 10° rotation using a mechanical testing apparatus. Stiffness, maximum torsional force, and load to 2.0 mm displacement were measured.
RESULTS
Double screw fixation constructs required more force to achieve 2.0 mm displacement during bending than single screw fixation constructs (mean difference: 78.3 N). The double screw group exhibited considerably greater maximum torque in the screw tightening direction than both the single screw and strut group (mean difference: 65.6 N·mm) and the single screw and wedge group (mean difference: 60.6 N·mm). Furthermore, it also demonstrated considerably higher maximum stiffness in the screw tightening direction compared to the single screw and strut group (mean difference: 4.8 N·mm/deg) and the single screw and wedge group (mean difference: 9.3 N·mm/deg).
CONCLUSIONS
Double screw fixation for scaphoid waist fractures with volar bone loss yields greater rotational and bending stability than single screw and strut or single screw and wedge graft constructs.
CLINICAL RELEVANCE
The superior stability provided by the double screw osteosynthesis could eliminate the need for time-consuming corticocancellous bone grafting.