Scientific article
Number and Locations of Screw Fixation for Volar Fixed-Angle Plating of Distal Radius Fractures: Biomechanical Study

https://doi.org/10.1016/j.jhsa.2010.03.027Get rights and content

Purpose

To compare the biomechanical properties of different numbers and locations of screws in a multidirectional volar fixed-angle plate in a distal radius osteotomy cadaver model.

Methods

We created an extra-articular fracture in 16 pairs of fresh-frozen human cadaver radiuses. The 32 specimens were randomized into 4 groups. All fractures were fixated with a multidirectional volar fixed-angle plate. We tested 4 different screw-placement options in the distal fragment. The distal fragment was fixed with 4 locking screws in the distal row of the plate in group a, and with 4 locking screws alternately in the distal and proximal rows in group b. In group c, 3 locking screws were used in the proximal row; in group d, 7 locking screws were used, filling all screw holes in the distal and proximal rows of the plate. The proximal fragment was fixed with 3 screws. The specimens were loaded with 80 N under dorsal and volar bending and with 250 N axial loading. Finally, load to failure tests were performed.

Results

Group d had the highest mean stiffness, 429 N/mm under axial compression, and was statistically significantly stiffer than the other groups. Group b had a mean stiffness of 208 N/mm, followed by group a, with 177 N/mm. Group c showed only a mean stiffness of 83 N/mm under axial compression. There were no statistically significant differences under dorsal and volar bending.

Conclusions

In this model of distal radial fractures, there was a difference regarding the stiffness and the placement of screws in the distal rows of a volar fixed-angle plate. Inserting screws in all available holes in the distal fragment offered the highest stability. Using only the proximal row with 3 screws created an unstable situation. Based on these findings, we recommend placing at least 4 screws in the distal fragment and assigning at least 2 screws to the distal row of the multidirectional screw-holes.

Section snippets

Specimen

We selected 32 fresh-frozen cadaver radiuses (16 matched pairs) with no bony deformation and stripped the soft tissues from the bone. We performed x-rays of each bone. The specimens were obtained from the Anatomical Institute of our university; we obtained permission from the ethics commission. Specimens were stored at −20°C until needed for implantation and testing. The average age of the cadavers was 79.3 years of age (minimum, 61 years; maximum, 99 years). A total of 28 pairs were female and

Results

Bone mineral density was similar among the 4 groups. The median BMD of all groups was 197.7 ± 81.8 mgCaHA/mL.

With the numbers tested, there were no statistically significant differences among the 4 groups under dorsal and volar bending (Fig. 3). The mean stiffness under dorsal bending in group a was 59.33 ± 9.63 N/mm, and under volar bending 78.93 ± 16.33 N/mm. In group b the mean stiffness under dorsal bending was 49.93 ± 17.67 N/mm, and under volar bending 62.26 ± 33.58 N/mm; and in group c

Discussion

The purpose of the present study was to compare the biomechanical properties of 4 different configurations of screw placement in an extra-articular distal radius fracture model with one multidirectional angular stable plate system with 2 rows of distal fixation screw-holes. The loading conditions were axial compression and dorsal and volar bending. The biomechanical results demonstrated that by filling all screw holes in the distal fragment (7 locking screws), the highest stiffness under axial

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The authors thank Medartis for donating the plating systems tested.

The company Medartis provided the plating systems that were tested. No grants were received in support of this study.

No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.

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