Volar fixed-angle plating of extra-articular distal radius fractures: a biomechanical analysis comparing threaded screws and smooth pegs

Weninger, Patrick, Dall'Ara, Enrico, Leixnering, Martin, Pezzei, Christoph, Hertz, Harald, Drobetz, Herwig, Redl, Heinz, and Zysset, Philippe (2010) Volar fixed-angle plating of extra-articular distal radius fractures: a biomechanical analysis comparing threaded screws and smooth pegs. Journal of Trauma: injury infection & critical care, 69 (5). E46-E55.

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Abstract

Background: Distal radius fractures represent the most common fractures in adult individuals. Volar fixed-angle plating has become a popular modality for treating unstable distal radius fractures. Most of the plates allow insertion of either threaded locking screws or smooth locking pegs. To date, no biomechanical studies compare locking screws and pegs under axial and torsional loading.

Methods: Ten Sawbones radii were used to simulate an AO/OTA A3 fracture. Volar fixed-angle plates (Aptus Radius 2.5, Medartis, Switzerland) with threaded locking screws (n = 5) or smooth locking pegs (n = 5) were used to fix the distal metaphyseal fragment. Each specimen was tested under axial compression and under torsional load with a servohydraulic testing machine. Qualitative parameters were recorded as well as axial and torsional stiffness, torsion strength, energy absorbed during monotonic loading and energy absorbed in one cycle.

Results: Axial stiffness was comparable between both groups (p = 0.818). If smooth pegs were used, a 17% reduction of torsional stiffness (p = 0.017) and a 12% reduction of minimum torque (p = 0.012) were recorded. A 12% reduction of energy absorbed (p = 0.013) during monotonic loading and unloading was recorded if smooth pegs were used. A 34% reduction of energy absorbed in one cycle (p < 0.007) was recorded if threaded screws were used. Sliding of the pegs out of the distal radius metaphyses of the synthetic bones was recorded at a mean torque of 3.80 Nm ± 0.19 Nm. No sliding was recorded if threaded screws were used.

Conclusions: According to the results of this study using Sawbones, volar fixed-angle plates with threaded locking screws alone are mechanically superior to volar fixed-angle plates with smooth locking pegs alone under torsional loading.

Item ID: 30050
Item Type: Article (Research - C1)
ISSN: 1529-8809
Keywords: distal radius fracture, volar fixed-angle plating, locking screws, locking pegs, biomechanical
Date Deposited: 04 Nov 2013 01:51
FoR Codes: 11 MEDICAL AND HEALTH SCIENCES > 1103 Clinical Sciences > 110314 Orthopaedics @ 100%
SEO Codes: 92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920116 Skeletal System and Disorders (incl. Arthritis) @ 50%
92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920118 Surgical Methods and Procedures @ 50%
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