Biomechanical analysis of two fixation methods for proximal chevron osteotomy of the first metatarsal.
OBJECTIVE
The proximal chevron osteotomy provides high correctional power. However, relatively high rates of dorsiflexion malunion of up to 17 % are reported for this procedure. This leads to insufficient weight bearing of the first ray and therefore to metatarsalgia. Recent biomechanical and clinical studies pointed out the importance of rigid fixation of proximal metatarsal osteotomies. Therefore, the aim of the present study was to compare biomechanical properties of fixation of proximal chevron osteotomies with variable locking plate and cancellous screw respectively.


METHODS
Ten matched pairs of human fresh frozen cadaveric first metatarsals underwent proximal chevron osteotomy with either variable locking plate or cancellous screw fixation after obtaining bone mineral density. Biomechanical testing included repetitive plantar to dorsal loading from 0 to 31 N with the 858 Mini Bionix(®) (MTS(®) Systems Corporation, Eden Prairie, MN, USA). Dorsal angulation of the distal fragment was recorded.


RESULTS
The variable locking plate construct reveals statistically superior results in terms of bending stiffness and dorsal angulation compared to the cancellous screw construct. There was a statistically significant correlation between bone mineral density and maximum tolerated load until construct failure occurred for the screw construct (r = 0.640, p = 0.406).


CONCLUSIONS
The results of the present study indicate that variable locking plate fixation shows superior biomechanical results to cancellous screw fixation for proximal chevron osteotomy. Additionally, screw construct failure was related to levels of low bone mineral density. Based on the results of the present study we recommend variable locking plate fixation for proximal chevron osteotomy, especially in osteoporotic bone.
Department of Orthopaedics, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria, reinhard.schuh@meduniwien.ac.at.
Reinhard
R
Schuh
Jochen Gerhard
JG
Hofstaetter
Emir
E
Benca
Madeleine
M
Willegger
Gobert
G
von Skrbensky
Shahin
S
Zandieh
Axel
A
Wanivenhaus
Johannes
J
Holinka
Reinhard
R
Windhager
D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D004867:Equipment Design; D006215:Hallux Valgus / Q000601:surgery*; D006801:Humans; D008682:Metatarsal Bones / Q000601:surgery*; D008875:Middle Aged; D010027:Osteotomy / Q000295:instrumentation / Q000379:methods*