RESUMO
Objective To compare the biomechanical behavior of a triple Endobutton technique for anatomic reconstruction of coracoclavicular ligament and with a modified Weaver-Dunn procedure. Methods Twelve fresh frozen cadaveric shoulders were applied with 70 N in superior, anterior and posterior direction, respectively, to measure displacement of the acromioclavicular joint. The failure test with the load at the rate of 25 mm/min was conducted to record the failure load and failure mode. The specimens were then randomly assigned to 2 groups: the triple Endobutton technique group and the modified Weaver-Dunn procedure group for reconstruction and to conduct displacement test and failure test again. The stability and mechanical strength of acromioclavicular joints after reconstruction under different states were then compared. Results The triple Endobutton technique group had significantly less anterior ((8.72±1.41) mm vs (37.03±5.05) mm) and posterior ((8.03±3.68) mm vs (14.85±1.89) mm) displacement than that in the modified Weaver-Dunn procedure group after reconstruction (P<0.05), and the former had similar displacement ((7.81±2.22) mm anterior and (7.16±1.95) mm posterior) as compared to the intact state. There were no significant differences in superior displacement among the groups. The modified Weaver-Dunn procedure group had significantly smaller failure loads ((172±9) N) than that in the triple Endobutton technique group ((687±115) N) and the intact ligament group ((685±234) N) (P<0.05). Conclusions The triple Endobutton technique has less anterior and posterior displacement and its stability is more closely approximate to the intact ligament; meanwhile, it has similar strength as coracoclavicular ligaments, which can better restore the function of coracoclavicular ligaments.
RESUMO
Objective To study distributions of the compressive strength on the whole spine endplates by measuring the compressive strength at different locations of the whole spine endplates. Methods Indentation tests were performed at 49 locations in 225 bony endplates of intact human vertebrae (C3 S1) from 5 fresh male specimens to record the failure loads. Results (1) For the whole spine endplates, failure loads of the cervical and lumbar spine were found to be higher than those of the thoracic spine (P<0.01).The failure load was first decreased from C3 to C7 before increasing to T1, and then dropping through T7 and rising again from T8, reaching the maximum at L4, and dropping at L5 before increasing again at S1. (2) The failure load at inferior cervical endplates was significantly higher than that at superior endplates except at C5 and T1 (P＜0.05). (3) Within the intervertebral space, the cranial endplates had a higher yield stress than the caudal endplates except at C5/6, T12/L1 and L5/S1. (4) Failure loads were generally increased from the central to peripheral zones (P＜0.05). (5) For different angular points, failure load distributions were found among the endplates (P<0.01). (6) Distributions of the compressive strength on the endplates varied significantly within the whole spine（P<0.01）. It was found that at C3/4, the failure load at posterior was higher than that at anterior, but at C5/6, the failure load at posterior and anterior was balanced. At T1, the failure load was found to be higher at posterior again, until passing through T2 5, and at T6 L3, the failure load at anterior was higher than that at posterior, and balanced between the anterior and posterior again at L4. At L5 S1, the failure load at posterior was higher than that at anterior. Conclusions The strength distributions on the endplates varied significantly at different locations within the whole spine, which was closely correlated with the physiological curve of the spine. The failure load at inferior endplates was higher than that at superior endplates and it was increased from central to peripheral zones. Within the intervertebral space, the compressive strength at cranial endplates was higher than that at caudal endplates.