How Many Screws Are Needed for Reliable Stability of Extra-articular Nonosteoporotic Distal Radius Fractures Fixed with Volar Locking Plates?

BACKGROUND: We hypothesized that volar locking pate fixation using a minimum number of screws—four in the distal row and two in the shaft of the plate—will provide sufficient stability for unstable extra-articular fractures of the distal radius. We aimed to compare the biomechanical properties of different numbers and locations of screws in volar locking plate fixation and describe the clinical and radiological outcome of plate fixation using a minimum number of screws for distal radius fractures. METHODS: We divided 48 artificial radius fracture bones into four groups (group A–D) based on the number and location of screws used for fixation with volar locking plates. The artificial bone models were subjected to axial compression and volar bending load with a force of 250 N and 80 N, respectively, for 1,000 cycles at a frequency of 1 Hz. We also retrospectively reviewed 42 patients with unstable, extra-articular, distal radius fractures who were treated with volar locking plate fixation using a minimum number of screws. RESULTS: Group A (seven distal screws and three proximal screws) had the highest mean stiffness: 303.7 N/mm under axial compression and 61.1 N/mm under volar bending. Compared with group A, group D (four screws in the distal part and two screws in the shaft) showed significantly lower stiffness; therefore, group D was considered inferior in terms of stability. However, in the fatigue test, neither deformation of the metal plate nor detachment or breakage of the metal screws was observed in all groups. In the clinical study, all fractures united without displacement and satisfactory clinical outcome was obtained. CONCLUSIONS: In the dorsally comminuted, extra-articular, nonosteoporotic distal radius fractures, the minimum number of screws—four in the distal row and two in the shaft—in volar locking plate fixation can provide sufficient stability. Further biomechanical studies involving osteoporotic bone will be necessary to confirm the results because volar plate fixation is most commonly used in patients with osteoporosis.