Highlights
- •Four constructs were tested for fixation of vertical medial malleolus fractures.
- •Divergent unicortical screws were similar to parallel screws during offset loading.
- •Bicortical screws were superior to unicortical screws.
- •Antiglide plating provided the most stiffness.
Abstract
Background
Vertical shear fractures of the medial malleolus (44-A2 ankle fractures) occur through
a supination–adduction mechanism. There are numerous methods of internal fixation
for this fracture pattern.
Methods
Vertical medial malleolus osteotomies were created in synthetic distal tibiae. The
models were divided into four fixation groups: two parallel unicortical cancellous
screws, two divergent unicortical cancellous screws, two parallel bicortical cortical
screws, or an antiglide plate construct. Specimens were subjected to offset axial
loading and tracked using high-resolution video.
Findings
The antiglide plate construct was stiffer (P < 0.05) than each of the other three constructs, and the bicortical screw construct
was stiffer (P < 0.05) than both unicortical screw constructs. The mean stiffness (standard deviation)
was 111 (SD 35) N/mm for the parallel unicortical screw construct, 173 (SD 57) N/mm
for the divergent unicortical screw construct, 279 (SD 30) N/mm for the bicortical
screw construct, and 463 (SD 91) N/mm for the antiglide plate construct. The antiglide
plate construct resisted displacement better (P < 0.05) than each of the other three constructs. The mean force for 2 mm of articular displacement was 284 (SD 51) N for the parallel unicortical screw
construct, 339 (SD 46) N for the divergent unicortical screw construct, 429 (SD 112)
N for the bicortical construct, and 922 (SD 297) N for the antiglide plate construct.
Interpretation
An antiglide plate construct provides the stiffest initial fixation while withstanding
higher load to failure for vertical medial malleolus fractures when compared to unicortical
and bicortical screw fixation.
Keywords
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References
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Article info
Publication history
Published online: October 12, 2015
Accepted:
October 6,
2015
Received:
June 28,
2015
Footnotes
☆Sawbones were obtained through funding from AO Trauma North America.
☆☆Implants were supplied by DePuy-Synthes (West Chester, PA, USA).
Identification
Copyright
© 2015 Elsevier Ltd. Published by Elsevier Inc. All rights reserved.
