Stability of medial locking plate and compression screw versus two crossed screws for lapidus arthrodesis.
BACKGROUND
Lapidus (first metatarsocuneiform joint) arthrodesis is an established procedure for the management of hallux valgus. This study investigated the utility of fixation with a medial locking plate with adjunct compression screw versus fixation with two crossed screws.


METHODS
Eight pairs of fresh-frozen human specimens were used in a matched pair test. Bone mineral density (BMD) was measured with peripheral quantitative computed tomography (pQCT). Fixation with two 4-mm-diameter crossed screws was compared versus a medial locking plate (X-Locking Plate 2.4/2.7; Synthes, Solothurn, Switzerland) with adjunct 4-mm-diameter compression screw. The specimens were tested in a four-point bending test. Parameters obtained were initial stiffness; plantar joint-line gapping after one cycle, 100 and 1000 cycles; and number of cycles to failure. Failure was defined as more than or equal to 3 mm plantar gapping.


RESULTS
The groups did not differ significantly with regard to BMD (p = 0.866) and initial stiffness (p = 0.889). The plate-and-screw construct showed significantly less movement during testing, and significantly (p = 0.001) more cycles to failure than did the crossed-screw construct. There was a significant correlation (crossed-screw construct: p = 0.014; plate-and-screw construct: p = 0.010) between BMD and the number of cycles to failure.


CONCLUSIONS
Under cyclic loading conditions, the construct using a medial locking plate with adjunct compression screw was superior to the construct using two crossed screws.


CONCLUSIONS
The medial locking-plate technique described could help shorten the period of nonweightbearing and reduce the risk of non-union.
AO Foundation, Clavadelerstrasse 8, 7270 Davos Platz, Switzerland. kajetan.klos@aofoundation.org
Kajetan
K
Klos
Boyko
B
Gueorguiev
Thomas
T
Mückley
Rosemarie
R
Fröber
Gunther O
GO
Hofmann
Karsten
K
Schwieger
Markus
M
Windolf
D000368:Aged; D000369:Aged, 80 and over; D001174:Arthrodesis / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D015519:Bone Density; D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D005260:Female; D006215:Hallux Valgus / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed