Biomechanical study of different internal fixators and fixation modes for middle 1/3 clavicle fractures

Abstract

Objective To investigate the effect of different internal fixators and fixation modes on the biomechanical properties of the middle 1/3 clavicle fractures.Methods Twenty-four artificial clavicle samples were prepared and used to simulate middle 1/3 oblique fractures.According to the clinical operative procedures,fractures were fixed respectively with locking plates in superior position,locking plates in anteroinferior position,reconstruction plates in superior position,and reconstruction plates in anteroinferior position.Then,resistance strain gauges were placed on the broken ends of the bone,embedded in polymethylmethacrylate (PMMA) and placed on Instron-8874 servo-hydraulic mechanical testing machine to have compression test,torsion test,and three-point bending test.Results Bending stiffness of control group,anteroinferior locking plate group,anteroinferior reconstruction plate group,superior locking plate group and superior reconstruction plate group was (539.16 ±47.45) N/mm,(1 013.47 ± 121.62) N/mm,(701.06 ± 53.28) N/mm,(360.98 ± 35.37) N/mm and (336.07 ± 18.83) N/mm respectively,with statistical significance in pair comparison among the control,superior,and anterior groups (P ＜ 0.05).In three-point bending test,the deflection limit of these groups was (8.75 ± 0.53) mm,(16.07 ±1.22) mm,(13.08 ±0.52) mm,(15.84±0.48) mm and (12.23 ±0.41) mm respectively.Moreover,the deflection limit of locking plate group and reconstruction plate group showed significant difference (P ＜ 0.05) and both were higher than that in control group (P ＜ 0.05).In torsion test,the mean torsion stiffness of locking plate group and reconstruction plate group was (0.77 ±0.08) Nm/deg and (0.73 ±0.11) Nm/deg in internal rotation and was (0.72 ± 0.07) Nm/deg and (0.75 ± 0.08) Nm/deg in external rotation,without statistically significant difference between groups.Resistor strain value in internal fixation groups lowered when compared to that in control group (P ＜ 0.05) and particularly lower strain value was observed in anteroinferior locking plate group.Conclusions (1) Plate fixation is the preferred method for treatment of clavicle fractures in that the plate can bear large amount of stress,provide a solid support and facilitate early fracture healing.(2) Anteroinferior clavicle plating using a locking plate possesses good biomechanical properties and has advantages of easy operation,low risk,solid fixation,few complications and cosmetic improvement.The technique is worthy of clinical practice. Key words: Clavicle; fracture fixation, internal; Biomechanics