Sohei Ebara

STUDY DESIGN: The in vitro tensile behavior of multiple-layer samples of anulus fibrosus were investigated from nondegenerate intervertebral discs. OBJECTIVES: To quantify the intrinsic tensile behavior of nondegenerate anulus fibrosus and the variations with position and age in the intervertebral disc. SUMMARY OF BACKGROUND DATA: Tension is an important loading mode in the anulus fibrosus. The tensile behavior of single- and multiple-layer samples of anulus fibrosus has been shown to vary with specimen orientation, position in the disc, and environmental conditions. Little is known of the changes in these site-specific tensile properties of the anulus with aging or degeneration of the intervertebral disc. METHODS: Multiple-layer specimens of anulus fibrosus were harvested with an orientation parallel to the circumference of the disc. Constant strain rate and uniaxial tensile tests were performed in 0.15 mol/l NaCl at slow strain rates to measure the intrinsic properties of the collagen-proteoglycan matrix of the anulus fibrosus. The tensile modulus, failure stress, failure strain, and strain energy density were determined. Statistical analyses were done to evaluate regional and age-related differences in these properties. RESULTS: Significant radial and circumferential variations in the intrinsic tensile properties of anular samples were detected. The anterior anulus fibrosus had larger values for tensile moduli and failure stresses than the posterolateral anulus. Also, the outer regions of the anulus had greater moduli and failure stresses and lower failure strains than the inner regions. Strain energy density did not vary significantly with region. Significant, but very weak, correlations were detected between tensile properties and age of the intervertebral disc. CONCLUSIONS: The observed variations in tensile behavior of multiple-layer anulus samples indicate that larger variations in tensile modulus and failure properties occur with radial position in the disc than from anterior to posterolateral regions. This pattern is likely related to site-specific variations in the tensile properties of the single-layer samples of anulus fibrosus lamellae and the organization of successive lamellae and their interactions. The results of the present study suggest that factors other than age, such as compositional and structural variations in the disc, are the most important determinants of tensile behavior of the anulus fibrosus.

A characteristic dysfunction of the hand has been observed in various cervical spinal disorders when there is involvement of the spinal cord. There is loss of power of adduction and extension of the ulnar two or three fingers and an inability to grip and release rapidly with these fingers. These changes have been termed "myelopathy hand" and appear to be due to pyramidal tract involvement. The characteristic nature of the signs permit the distinction between myelopathy and changes due to nerve root or peripheral nerve disorder. The clinical significance of these signs has been assessed against other tests and their value in management is discussed.

We have studied the morphometry of the spinal cord in 50 patients with cervical compression myelopathy. Computed tomographic myelography (CTM) showed that the transverse area of the cord at the site of maximum compression correlated significantly with the results of surgery. In most patients with less than 30 mm2 of spinal cord area, the results were poor; the cord was unable to survive. Several factors, such as chronicity of disease, age at surgery and multiplicity of involvement are said to influence the results of surgery, but the transverse area of the cord at the level of maximum compression provides the most reliable and comprehensive parameter for their prediction.

BACKGROUND: The authors sought to identify treatment-related factors that influenced survival after surgical treatment for metastatic spinal tumors and to evaluate the relationship between survival and postoperative ambulation time as a factor related to quality of life. METHODS: The medical records of 81 patients with metastatic spinal tumors who underwent palliative surgery at the study institution were assessed. Univariate analysis for factors influencing survival used the Kaplan-Meier log rank statistic and multivariate analysis used the Cox proportional hazards model. The Spearman correlation test was used to analyze the relationship between postoperative ambulation and survival time. RESULTS: The patients had a median age of 59.9 years and a median survival of 10.6 months after surgery. For patients, postoperative ambulatory median survival was 16.5 months and median ambulation time was 13.8 months. By univariate analysis, anatomic site of the primary tumor, postoperative ambulation, and combined adjuvant therapy (chemotherapy plus radiotherapy) were associated with prolonged survival (P < 0.05). Multivariate analysis identified primary site and postoperative ambulatory function as independent predictors of prolonged survival (P < 0.0001). Significant correlations were found between ambulation time and survival time of patients who were able to walk after surgery (P < 0.0001), even in patients with liver (P < 0.05) or lung carcinoma (P < 0.05). CONCLUSIONS: The anatomic site of primary carcinoma and postoperative ambulation were associated with longer survival after palliative surgery for metastatic spinal tumor. When ambulation is attained after surgery, it can be preserved until late in remaining life even when the primary tumor is unfavorable. Palliative surgery for spinal metastasis can improve the quality and quantity of life.