Influence of flexion-extension motion of lumbar spine on lumbosacral dural sac. An experimental study

To analyze the effects of flexion-extension motion of lumbar spine on the position and shape of lumbosacral dural sac, 10 flexion/extension lateral myelograms of cadaver specimens of normal lumbar spine were measured. The results showed that moving from flexion to extension both sagittal diameter and length of the dural sac decreased significantly, the dural sac moved caudally, and the sagittal diameter of the anterior epidural space decreased in the mid-vertebral level but increased in the intervertebral level. The dynamic changes of the dural sac and their influence factors and clinical relevance were discussed.

Effect of partial discectomy on the stability of the lumbar spine. A study of kinematics

The effect on the stability of the lumbar motion segment, as affected by partial discectomy, was investigated using three-dimensional motion measurement technique. Eight functional spinal units from fresh cadaver lumbar spines were potted and clinically relevant loads applied through a special loading frame attached rigidly to the top vertebra of the specimen. Partial discectomy was performed on the right side of the specimen. The three-dimensional motions of each lumbar motion segment, before and after partial discectomy, were recorded. The results showed that partial discectomy significantly affects the stability of lumbar spinal motion segments. The clinical relevance of this finding is discussed.

Dynamic changes of the cervical ligamental flavum in hyperextension---hyperflexion movement and their measurements

Ten fresh cadaver cervical spine specimens were frozen and bisected through the median sagittal plane. The length, thickness of the ligamental flavum (LF) and its protruding depth into the cervical canal were measured in hyperextension, hyperflexion and mid-position. The results showed that LF was elongated and became thinner in hyperflexion and shortened, thickened, and protruded into the cervical canal in hyperextension. The protruding depth into the canal was 3.5 +/- 0.35 mm at C 5-6, 3.25 +/- 0.50 mm at C 4-5 and 2.96 +/- 0.35 mm at C 6-7 respectively. Segmental stenosis was observed at the level of intervertebral space in hyperextension.

Primary structure of rabbit skeletal muscle glycogen synthase deduced from cDNA clones

The complete amino acid sequence of rabbit skeletal muscle glycogen synthase was deduced from cDNA clones with a composite length of 3317 bp. An mRNA of 3.6 kb was identified by Northern blot analysis of rabbit skeletal muscle RNA. The mRNA coded for a protein of 734 residues with a molecular weight of 83,480. The deduced NH2-terminal and COOH-terminal sequences corresponded to those reported for the purified protein, indicating the absence of any proteolytic processing. At the nucleotide level, the 5' untranslated and coding regions were 79 and 90% identical for rabbit and human muscle glycogen synthases, whereas the 3' untranslated regions were significantly less similar. The enzymes had 97% amino acid sequence identity. Interestingly, the NH2 and COOH termini of rabbit and human muscle glycogen synthase, the regions of phosphorylation, showed the greatest sequence variation (15 of 19 mismatches and two insertion/deletion events), which may indicate different evolutionary constraints in the regulatory and catalytic regions of the molecule.

The effect of flexion-extension motion of the lumbar spine on the capacity of the spinal canal. An experimental study

The symptoms of lumbar spinal stenosis are often posture-dependent, and it is generally accepted that the capacity of the spinal canal is affected by flexion-extension motions of the lumbar spine. A study of spinal capacity in flexion-extension of ten cadaver specimens on the lumbar spine was done and measurements were obtained from the flexion-extension lateral myelograms. There proved to be a larger capacity of dural sac of 3.5 to 6.0 ml (4.85 +/- 0.75 ml) in flexion than in extension, and the differences were highly significant (P less than 0.001). In addition, the sagittal diameter of the dural sac and the length of the spinal canal increased from extension to flexion. Because of the effect of flexion-extension motion of the lumbar spine on the spinal capacity, we suggest that maintaining the lumbar spine in flexion is more suitable since spinal canal capacity is enlarged and symptoms may be mitigated.

Treatment of longitudinal injuries in avascular area of meniscus in dogs by trephination

A study promoting the healing of longitudinal injuries in an avascular area of the meniscus in 21 male dogs is reported. One horizontal hole from the peripheral vasculature to one of the artificial longitudinal injuries to both medial menisci of the knee in each dog was made with a needlelike trephine. The knee joints were not immobilized and the samples were taken 2, 4, 8, 12, and 24 weeks, respectively, after the operation. [3H]Thymidine was injected into the joint cavity 72 h before the sample was taken. Healed lengths were measured, and pathologic examinations and autoradiography were performed. The results showed that all of the injuries treated with trephination were partly or totally healed whereas those in controls were not healed at all, suggesting that trephination may be the procedure of choice for clinic orthopedists dealing with such injuries. By the 8th week, the healed length stopped increasing, the scar tissue began to mature, and the DNA synthesis of the fibroblasts in the granulation tissue and the fibrochondrocytes in the trephined meniscus reduced. It is thought that the fibrochondrocyte of the meniscus and the fibroblast in the granulation might be capable of obtaining the thymidine directly from the synovia of knee joint for their DNA metabolism. Multiplication of the fibrochondrocyte in the injured meniscus was also found.

Suture and immobilization of acute peripheral injuries of the meniscus in rabbits

A comparative study of suturing or nonsuturing with or without immobilization of acute peripheral injuries to the medial meniscus of rabbits is reported. Artificial injuries to both knees of 44 male China Blue-Violet rabbits were sutured or left unsutured. One knee joint of each rabbit was immobilized postoperatively for 6 weeks. The maximum breaking strength was measured, pathologic examinations were performed, and healed areas were measured. The results showed that there was greater healed area, higher maximum breaking strength, earlier matured scar tissue formation, and more regular fiber alignment in the treatment groups with simple immobilization of the knee joint. These results were superior to suturing plus immobilization, suggesting that external immobilization of the knee joint is the key to the treatment of acute peripheral injuries of the meniscus. It may be the procedure of choice for clinical orthopedists dealing with such injuries. The measurement of the meniscus healed area and maximum breaking strength and the use of new material with this method of immobilization were introduced by the authors.

A quantitative and histological study on pulmonary effects of asbestos exposure in general autopsied lungs

We demonstrated the distribution of asbestos bodies (ABs) in the lungs of 656 consecutive autopsy cases by KOH digestion method. Nine patients including one case with asbestosis had more than a thousand ABs. These patients were all blue-collar workers except the two cases without occupational history. The tissue sections for these patients revealed the constant presence of more than one or two ABs. In addition, five of these subjects had parenchymal and/or peribronchiolar fibrosis. On the basis of the result of AB counts, we selected 17 subjects for enumeration and typing of asbestos fibers (AFs). The number of AFs roughly correlated with that of ABs. However, the ratio of AFs to ABs ranged from 13 to 3,700. The fiber types in our selected subjects were almost always amphibole (crocidolite, amosite). These findings indicate that modest or secondary exposure to asbestos causes virtual asbestosis to several subjects among the general population.