Mechanical comparison of two types of fixation for proximal first metatarsal crescentic osteotomy.
BACKGROUND
The proximal crescentic osteotomy is an effective technique for correcting a widened 1-2 intermetatarsal angle associated with moderate to severe hallux valgus deformities. However, postoperative dorsal malunion at the osteotomy site from loss of fixation has been reported. The purpose of this study was to evaluate the biomechanical characteristics of a new custom-designed plate and compare it to the traditional screw and Kirschner wire construct.


METHODS
Twenty identical Sawbone (Pacific Research Laboratories, Vashon, WA) models were used for the study. A proximal crescentic osteotomy was done on each specimen, and 10 were secured with a dorsomedial plate (group I). The remaining 10 models were fixed with a screw and Kirschner wire combination (group II). Physiologic cyclical testing was done using a mechanical testing machine to evaluate dorsal displacement of the metatarsal. Load-to-failure testing was then done on each specimen to evaluate ultimate failure and stiffness of the constructs. Groups I and II were statistically compared using paired t-testing.


RESULTS
The mean dorsal displacement of the first metatarsal head after 1000 cycles was 0.19 mm (SD = 0.09 mm) for group I and 0.28 mm (SD = 0.15) for group II, and the difference was not statistically significant (p = 0.08). Group I demonstrated statistically superior ultimate failure strength (95.2 N) and stiffness (26.8 N/mm) compared to group II (73.7 N, 19.4 N/mm).


CONCLUSIONS
Based on Sawbone models, dorsal plate fixation of proximal crescentic osteotomy provides a stronger construct than the traditional screw and Kirschner wire construct. The clinical use of the specially-designed plate described in this study may lower the incidence of dorsal malunions that occur postoperatively and may decrease the occurrence of transfer metatarsalgia. Its application may be particularly helpful in patients with poor bone quality.
Jones
Carroll
C
Miller Orthopaedic Clinic, Charlotte, NC, USA.
Coughlin
Michael
M
Petersen
Wolf
W
Herbot
Mirco
M
Paletta
Jürgen
J
D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D001864:Bone Wires; D004868:Equipment Failure; D006215:Hallux Valgus / Q000601:surgery*; D006801:Humans; D008682:Metatarsal Bones / Q000601:surgery*; D008953:Models, Anatomic; D010027:Osteotomy / Q000295:instrumentation / Q000379:methods*