Analysis of the relationship between morphology of intervertebral disc and some correlated factors following discography in patients with chronic low back pain.

OBJECTIVE: To evaluate the diagnostic effectiveness of discography in discogenic low back pain (LBP). METHODS: Ninety-six cases of chronic LBP with or without referred thigh pain were enrolled in this study. All these cases received CT scan following discography once conservative treatment for at least 6 months had failed. There were 42 men and 54 women, aged from 24 to 67 years (average 46.4). Discography was performed on 218 discs. The positive discs were classified morphologically according to the Dallas Discogram Description (DDD). RESULTS: (i) The 56 cases (58.3%) which were positive on discography were divided into two subgroups of age less or more than 50 years. Positive rates for the two subgroups were 33.3% and 66.7%, respectively; (ii) one hundred and twenty-two discs, of which 62 (50.8%) were positive on discography, showed morphologic abnormality, whereas all the discography positive discs showed morphologic abnormality. No complication related to discography was found in any case. CONCLUSION: (i) Compared with the younger patients, older LBP patients have a lower positive rate of discography despite the presence of more serious degenerative disc changes; (ii) outer layer disruption of the annulus fibrous correlates with positive discography; (iii) MRI intensity changes are not specific in diagnosing discogenic pain. Additional discography is needed to identify the painful disc; and (iv) the contrast volume injected into discs can be affected by a variety of factors which restrict its diagnostic value.

[Instant and fatigue stability analysis of anterior lumbar interbody fusion with stand-alone cage].

OBJECTIVE: To investigate the spinal segment instant and fatigue stability of anterior lumbar interbody fusion with stand-alone cage. METHODS: The vertebrae L4 and S1 of 6 human lumbar specimens (L3 - S1) were embedded with dental base acrylic resin powder and fixed on mechanical machine, and the L4/L5 and L5/S1 disk spaces were left active. The 6 specimens underwent mechanical test as control group first, and then used as experimental group with a cage implanted in L5/S1. Instant instability was tested in three directions: flexion, extension, and lateral bend. The relative movement of L4/L5 and L5/S1 was recorded. Fatigue instability was tested after 50 000 times of flexion-extension movement, and the relative displacement between the cage and S1 was recorded. RESULT: In the three directions of flexion, extension, and lateral bend, the relative movements of L5/S1 in the experimental group were 0. 83 +/- 0.26 degrees, 1.60 +/- 0.19 degrees, and 0.72 +/- 0.20 degrees respectively, all significantly decreased than those of the control group (3.60 +/- 0.30 degrees, 4.82 +/- 0.34 degrees, and 3.80 +/- 0.28 degrees respectively, all P < 0.01). The relative movement of L4/L5 of the experimental group were 5.82 +/- 0.36 degrees, 5.38 +/- 0.30 degrees, and 4.96 +/- 0.29 degrees in the three directions respectively, all significantly higher than those of the control group (4.16 +/- 0.33 degrees, 4.02 +/- 0.30 degrees, and 3.48 +/- 0.34 degrees respectively, all P <0.01). After 50 000 times of flexion-extension fatigue movement, the relative displacement between the cage and S1 was zero. CONCLUSION: Anterior lumbar interbody fusion with a stand-alone cage has excellent instant and fatigue stability, which can provide enough stability for clinical bone fusion without other internal fixation.