The effect of posterior thoracic spine anatomical structures on motion segment flexion stiffness.

STUDY DESIGN: This in vitro human cadaveric study tested the loss of thoracic motion segment flexion stiffness after sequential posterior upper instrumented vertebra anchor placement techniques and posterior column destabilization. OBJECTIVE: This study was designed to determine the possible destabilizing effects of upper thoracic instrumentation anchor site preparation. SUMMARY OF BACKGROUND DATA: Proximal junctional kyphosis after instrumentation and arthrodesis for scoliosis and related spine deformities has recently been reported to range from 10% to 46%. The effect of posterior skeletal dissection associated with upper instrumented vertebra anchor placement on adjacent motion segment flexion stiffness has not been previously studied. METHODS.: Twenty-three intact thoracic motion segments were obtained from 6 human cadavers. Biomechanical testing was performed with each motion segment flexed to approximately 3.2 degrees at a rate of 0.1 Hz, with corresponding torques recorded. Data were collected after a series of 6 posterior procedures. Differences with P value <0.01 were considered significant and those with P value <0.05 marginally significant. RESULTS: Supratransverse process hook, supralaminar hook, pedicle screw placement, or pedicle screw removal done, bilaterally, produced similar, small (range, 2.09%-6.03%), nonsignificant reductions in motion segment flexion stiffness. But when totaled, these 4 procedures resulted in a significant 16.31% loss of flexion stiffness. The fifth procedure of supraspinous and interspinous process ligament transection added a marginally significant 6.59% incremental loss of flexion stiffness. Supralaminar hook site preparation combined with supraspinous and interspinous process ligament transection resulted in a marginally significant 12.62% incremental loss of flexion stiffness. Transection of the remaining posterior structures (facet joints and all other posterior soft tissue structures) produced a significant additional flexion stiffness loss of 44.72%. The anterior column alone provided only 32.39% of the total motion segment flexion stiffness. Transection of all posterior stabilizing structures, similar to a Smith-Peterson/chevron/Ponte resection, decreased motion segment flexion stiffness significantly, 67.61%. CONCLUSION: Posterior thoracic skeletal structures involved in upper instrumented vertebra exposure andanchor placement were found to contribute to adjacent segment flexion stiffness. Although stiffness loss was small after individual procedures, the effects were additive for routinely used combinations.

The prevalence of increased proximal junctional flexion following posterior instrumentation and arthrodesis for adolescent idiopathic scoliosis.

STUDY DESIGN: Retrospective case series. OBJECTIVE: To determine the prevalence of proximal junctional sagittal plane flexion increase after posterior instrumentation and arthrodesis. SUMMARY OF BACKGROUND DATA: Increased flexion proximal to the junction of the instrumented and fused spinal region with the adjacent mobile spine seems to be a relatively recent observation, may be increasing, and is occasionally problematic. METHODS: The proximal junctional sagittal angulation 2 motion segments above the upper end instrumentation levels was measured on lateral standing preoperative and follow-up radiographs. RESULTS: One hundred seventy-four of 208 consecutive patients (84%) at an average radiograph follow-up of 4.9 +/- 2.73 years had increased proximal junctional flexion in 9.2%. The preoperative junctional measurements were normal for both normal and increased flexion groups. At follow-up, proximal junctional flexion had increased significantly more in the increased flexion group (2.1 degrees vs. 14.1 degrees , P < 0.0001). None of the possible risk factors studied, including demographic comparisons, Lenke classification (including lumbar and sagittal modifiers), end-instrumented vertebrae, end vertebra anchor configurations, surgical sequence, additional anterior surgery, rib osteotomies, and instrumentation length, were significantly associated with increased proximal junctional flexion at follow-up. Lenke 6 curves were at marginal risk of increased proximal junctional flexion (P = 0.0108). There were no differences between the groups in total Scoliosis Research Society-22r scores at an average follow-up of 8.0 +/- 3.74 years. No patient had additional surgery related to increased proximal junctional flexion. CONCLUSION: The prevalence of increased proximal junctional flexion was 9.2%. No significant risk factors were identified. Total Scoliosis Research Society-22r scores were similar for groups with normal and increased proximal junctional flexion at follow-up.

The reliability and concurrent validity of the Scoliosis Research Society-22r patient questionnaire compared with the Child Health Questionnaire-CF87 patient questionnaire for adolescent spinal deformity.

STUDY DESIGN: This is a clinic-based cross-sectional study involving 2 health-related quality-of-life (HRQL) questionnaires. OBJECTIVES: To compare the score distribution and reliability of the spinal deformity specific Scoliosis Research Society-22r (SRS-22r) questionnaire and the established generic Child Health Questionnaire-CF87 (CHQ-CF87), and to assess the concurrent validity of the SRS-22r using the CHQ-CF87 in an adolescent spine deformity population. SUMMARY OF BACKGROUND DATA: Different questionnaires are commonly thought to be necessary to assess the HRQL of adolescent and adult populations. But since spinal deformities usually begin in the second decade of life, longitudinal follow-up with the same HRQL is desirable. The SRS-22r HRQL has recently been validated for score distribution and internal consistency in a spinal deformity population ranging in age from 7 to 78 years. METHODS: The SRS-22r and CHQ-CF87 HRQLs were completed by 70 orthopedic spinal deformity outpatients 8 to 18 years of age, of whom 54 returned mailed retest questionnaires at an average of 24 days later. RESULTS: The ceiling effect averaged 27% for the SRS-22r and 36% for the CHQ-CF87. Respective values for internal consistency (Cronbach alpha) were 0.81 and 0.82, and for test-retest reproducibility the intraclass correlations (ICC) were 0.73 and 0.61. Concurrent validity was r > or = 0.68 or more for relevant function, pain, and mental health domains. The SRS Self-Image and particularly the Satisfaction/Dissatisfaction with Management domains did not correlate well with any CHQ-CF87 domains (r = 0.50 and 0.30, respectively). CONCLUSION: In a spinal deformity population 8 to 18 years of age, the score distribution and reliability, internal consistency, and reproducibility of the SRS-22r were at least as good as the CHQ-CF87. The SRS-22r function, pain, and mental health domains were concurrently valid in comparison to relevant CHQ-CF87 domains, but the SRS-22r self-image and satisfaction/dissatisfaction domains were not, thereby providing health-related quality-of-life information not provided for by the CHQ-CF87.

Measuring outcomes in spinal deformity.

The development of validated health-related quality-of-life instruments that are generic (Short Form-36) or disease-specific (Scoliosis Research Society [SRS]-22) allows physicians and researchers to measure the qualitative impact of spinal deformity and its treatment on their patients quantitatively. Although some further research may be needed in the area of the responsiveness of the SRS-22r, it should be considered a validated instrument that is useful in the research and treatment of pediatric and adult patients with spinal deformity.