[Research of the peak force of pullout about different thoracic hemi-epiphyseal compression staples in animal].
OBJECTIVE
To evaluate the initial dislocation resistance of the pullout force of different material or different type of goats thoracic hemi-epiphyseal compression staples.


METHODS
According to the measuring anatomic data of thoracic vertebra (T6 approximately T11) specimens in goats (age 2 approximately 3 months), we designed stainless steel staple whose original distances between two opened prone were 10 mm and three kinds of shape memory alloy (SMA) staples whose original distances between two opened prone were respectively 5.0, 6.5 and 8.0 mm. Four specimens were used and each was cut into three functional spinal units (FSU) of T6 - T7, T8 - T9 and T10 - T11, then FSU were redistributed. Stainless steel staples and SMA staples were implanted into both sides of FSU. There were four groups: group I was stainless steel staples. group II was SMA of 5.0 mm. group III was SMA of 6.5 mm. group IV was SMA of 8.0 mm. The peak force of pullout in each FSU was measured on 858 biomechanical test machine.


RESULTS
The peak force of group I was (20.62 +/- 9.15) N, group II was (74.18 +/- 8.81) N, group III was (51.28 +/- 5.44) N, group IV was (39.13 +/- 7.54) N. It is found that there were statistically different between all groups (P < 0.05). The peak force values of group I were lowest than others.


CONCLUSIONS
Differences of the initial dislocation resistance in different materials. SMA staples exhibit higher pullout force. Meanwhile, the pullout forces were also different between SMA staples, the smaller original distance the higher peak force of pullout.
Zhang
Wei
W
Department of Orthopedics, General Hospital of Chinese People's Liberation Army, Beijing 100853, China.
Zhang
Yong-gang
YG
Wang
Yan
Y
Wang
Ai-yuan
AY
D000497:Alloys; D000818:Animals; D001858:Bone Nails; D004838:Epiphyses / Q000601:surgery*; D005260:Female; D006041:Goats; D008422:Materials Testing; D019563:Mechanics; D019637:Orthopedic Procedures / Q000295:instrumentation*; D013193:Stainless Steel; D013904:Thoracic Vertebrae
D000497:Alloys; D013193:Stainless Steel