| Objective: In most cases, for mild degeneration of the intervertebral disc(IVD) and acute herniated nucleus pulposus(HNP), the clinical still recommend using simple lumbar discectomy, but the surgery can’t directly repair the damaged IVD. Due to lost the protection of the annulus fibrosus(AF), the rest of the nucleus pulposus(NP) is likely to herniated again under pressure, many symptomatic patients with same-site recurrent disc herniation may need reoperation. In recent years, increasing knowledge and technical advancements in the field of tissue engineering has resulted in numerous promising strategies to repair, replace or regenerate the HNP. None of these advancements, however,has yet resulted in a clinically proven effective therapy. Lack of effective strategies that deal with the damaged AF is one of the major limitations. Therefore, how to repair the AF is an urgently clinical problem that need to be resolved.The objective of our research is to study the effect of suturing AF on the biomechanical stability of lumbar spine and intradiscal pressure, and to assess the effectiveness of different techniques on repairing AF through quantitative discomanometry and cyclic fatigue loading.Methods: 1. The in vitro testing was performed on 20 lumbar functional spinal units(FSUs), which had been harvested from 1-month-old calves. We obtained the spinal units from an abattoir. The specimens were carefully stripped of soft tissue and muscle layers,preserving all bone structures and ligaments. Specimens can be divided into three groups:intact, annulotomy and suture,using self pre-and post-control observation. First, in three dimensional biomechanical Testing, we randomly selected 10 specimens, the range of motion(ROM) and neutral zone(NZ) were measured in flexion –extension(FE), lateral bending(LB) and axial rotation(AR) positions. Second, standard quantitative discomanometry(QD) test was performed using 10 other specimens in self-made apparatus,intradiscal pressure were determined by testing the leakage pressure.2. Another in vitro testing was performed on 50 lumbar FSUs, which had been harvested from 1-month-old calves, FSU consists of two adjacent vertebrae, the intervertebral disc and all adjoining ligaments between them and excludes other connecting tissues such as muscles. Each FSUs made one incision. According to their respective AF closure methods,FSUs were randomly assigned into 1-5 groups: 1--cyanoacrylate glue, 2--simplesuture(“U†suture), 3--modified purse-string suture(MPSS suture), 4--cyanoacrylate glue+simple suture, and 5--cyanoacrylate glue +MPSS suture. QD test and cyclic fatigue loading were then applied to compare their leakage pressure and loading cycles, as the parameter of disk integrity.Results: 1. On the flexion, left and right bending positions, The annulotomy significantly increased ROM and NZ compared with the intact state. Once AF were sutured,the stability of the intervertebral disc restored to the intact. The mean leakage pressure in intact,annulotomy and suture group was(5.0±0.0),(0.5±0.5)and(1.7±0.8)MPa,respectively. The leakage pressure of suture group was higher than annulotomy group,while lower than intact group.2. The leakage pressure in QD test from group 1-5 was 0.76±0.11 MPa, 1.66±0.11 MPa,1.84±0.15 MPa, 1.88±0.13 MPa and 2.16±0.24 MPa respectively. group 5 was dramatically higher than the other groups(P<0.05). The number of loading cycles in group 1-5 was4.42±0.59, 8.06±0.75, 8.44±1.01, 9.76±0.23 and 9.88±0.21 ten thousand times respectively,except for group 4, the difference between group 5 and the other groups was significant(P<0.05).Conclusion: Suturing annulus fibrosus after annulotomy can restore the stability and intradiscal pressure of lumbar spine incompletely. Closing the incision of AF with suture or fibrin glue alone might not be advisable, the better method was cyanoacrylate glue with modified purse-string suture. |
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