Factor analysis of the SRS-22 outcome assessment instrument in patients with adult spinal deformity.

PURPOSE: Designed for patients with adolescent idiopathic scoliosis, the SRS-22 is now widely used as an outcome instrument in patients with adult spinal deformity (ASD). No studies have confirmed the four-factor structure (pain, function, self-image, mental health) of the SRS-22 in ASD and under different contexts. Factorial invariance of an instrument over time and in different languages is essential to allow for precise interpretations of treatment success and comparisons across studies. This study sought to evaluate the invariance of the SRS-22 structure across different languages and sub-groups of ASD patients. METHODS: Confirmatory factor analysis was performed on the 20 non-management items of the SRS-22 with data from 245 American English-, 428 Spanish-, 229 Turkish-, 95 French-, and 195 German-speaking patients. Item loading invariance was compared across languages, age groups, etiologies, treatment groups, and assessment times. A separate sample of SRS-22 data from 772 American surgical patients with ASD was used for cross-validation. RESULTS: The factor structure fitted significantly better to the proposed four-factor solution than to a unifactorial solution. However, items 14 (personal relationships), 15 (financial difficulties), and 17 (days off work) consistently showed weak item loading within their factors across all language versions and in both baseline and follow-up datasets. A trimmed SRS (16 non-management items) that used the four least problematic items in each of the four domains yielded better-fitting models across all languages, but equivalence was still not reached. With this shorter version there was equivalence of item loading with respect to treatment (surgery vs conservative), time of assessment (baseline vs 12 months follow-up), and etiology (degenerative vs idiopathic), but not age (< vs ≥50 years). All findings were confirmed in the cross-validation sample. CONCLUSION: We recommend removal of the worst-fitting items from each of the four domains of the SRS-instrument (items 3, 14, 15, 17), together with adaptation and standardization of other items across language versions, to provide an improved version of the instrument with just 16 non-management items.

Neovascularization induced by anulus and its inhibition by cartilage endplate. Its role in disc absorption.

STUDY DESIGN: A study of neovascularization with respect to the anulus and the endplate. OBJECTIVES: To determine the ability of the anulus and the endplate to induce neovascularization and to study the effect of the endplate on the neovascularizing activity of the anulus. SUMMARY OF BACKGROUND DATA: Previous studies showed that herniations contain varying amounts of nucleus pulposus, anulus fibrosus, and endplate. Results of recent studies have shown preferential neovascularization around the herniated anulus rather than the endplate. METHODS: Human L4-L5 discs were harvested from three specimens. In the left cornea of New Zealand White rabbits, an anulus (AF group) or an endplate (EP group) was implanted 4 mm from the superior corneoscleral limbus. In a third group (AF and EP group), an endplate was implanted between the anulus and the limbus. Twelve assays were done for each group. Sham surgeries were done on a fourth group as a control. Neovascularization was monitored by stereomicroscopy and scored from 0 (no neovascularization) to +5 (capillaries growing around the implant). Histologic studies were done at weekly intervals. RESULTS: In the AF group, the anulus induced neovascularization in 11 or 12 corneas. By the third week, the anulus appeared thinner, and the newly formed vessels regressed. In the EP group, only two corneas showed neovascularization; 10 corneas showed no vascularization. In the AF and EP group, three corneas showed no neovascularization, seven had sustained neovascularization, and two had vascularization. In the corneas containing the endplates, the implants remained unchanged. Control corneas did show vascularization. Histologic sections showed that neovascularization and cell infiltration were most abundant in the AF group, followed by the AF&EP and the EP groups. CONCLUSION: The reactions to anulus fibrosus and to cartilage endplate differ. Anulus fibrosus may contain soluble substances that induce neovascularization, leading to its degradation and absorption. Cartilage endplate fails to induce neovascularization or diminishes the neovascular response, preventing its degradation. Disc herniations that contain a significant amount of endplate may not be degraded nor absorbed, leading to failure in spontaneous remission of symptoms.

Histologic changes in the disc after cervical spine trauma: evidence of disc absorption.

We examined the histologic changes in the disc in two cases of traumatic cervical disc herniation and compared it with previous histologic studies done in degenerative disc herniations. Differences in the absorption of herniated cartilage endplate and annulus fibrosus are also discussed. The herniated disc material was surrounded by fibrovascular tissue. Vessels in this fibrovascular tissue were seen to continue into the annulus fibrosus but not into the endplate. Scattered cartilage fragments and macrophages in the fibrovascular tissue were localized around the margin of the disc. The herniation produced a visible defect in the injured intervertebral disc. On serial sections, the amount of herniated annulus fibrosus appeared to be smaller than the defect produced in the annulus fibrosus of the injured disc. However, the herniated endplate seemed to be the same size as the defect produced in the endplate of the injured disc. Fibrovascular tissue formation, vessel infiltration into annulus fibrosus, and the presence of peripheral macrophages suggest marginal absorption. The cartilage fragments are probably remnants of disc tissue produced during the process of absorption. These findings are similar to that seen in degenerated herniated discs and suggest an absorptive process. Absorption of the annulus is more significant than absorption of the endplate.