Curve severity and apical vertebral rotation and their association with curve flexibility in adolescent idiopathic scoliosis.

PURPOSE: To determine the association between coronal Cobb's angle and Nash-Moe index in patients with adolescent idiopathic scoliosis. We also attempted to determine whether apical vertebral derotation depended upon the curve flexibility. OVERVIEW OF LITERATURE: The three-dimensional nature of adolescent idiopathic scoliosis (AIS) is well established. Knowledge of all components of this complex deformity is essential to formulate effective treatment strategies. Though the importance of quantifying all the components of the deformity, in AIS, has been analysed in detail, very few studies have been done to ascertain the relationship between the coronal plane deformity and apical vertebral rotation. METHODS: Digitalised standing and supine stretch anteroposterior (AP) radiographs of 158 patients with AIS were analysed. The standing and supine stretch AP radiographs were compared to calculate the percentage reduction of Cobb's angle to determine curve flexibility. The derotation of the apical vertebra on application of traction was also noted. The one-way repeated ANOVA was used to determine the association between Cobb's angle and Nash-Moe index. The independent sample t test was used to determine whether a statistically significant difference was present, in the age of the patient, severity of the curve and percentage reduction of Cobb's angle between those curves that derotated and those that did not, when stretched. RESULTS: The one-way repeated ANOVA revealed an association between Cobb's angle and Nash-Moe index on the standing and supine AP stretch radiographs (P < 0.01). The Independent sample t-test showed a statistically significant difference in percentage reduction of Cobb's angle between those curves that derotated compared to those that did not, on stretch (P < 0.01). CONCLUSIONS: This study demonstrates that there is an association between apical vertebral rotation and the coronal plane deformity. It also demonstrates that flexible curves derotate to a greater extent compared to rigid curves, when stretched.

Single-stage anterior debridement, posterior instrumentation and global fusion in thoracic and thoracolumbar tubercular spondylodiscitis.

PURPOSE: The present study evaluated the clinical and radiological outcomes in patients with tuberculosis of the thoracic and thoracolumbar spine, treated by an operative technique in which anterior debridement with posterior instrumentation and global fusion was performed through a single-stage posterior approach. METHODS: Ninty-seven patients with spinal tuberculosis, between T1 and L1, in whom anterior debridement, bone grafting, with posterior instrumentation and fusion was performed through a single-stage posterior approach, with a minimum follow-up of 2 years, formed the basis of this study. During each follow-up, neurological recovery was assessed using modified American Spinal Injury Association grading, healing of the disease was assessed by appearance of sclerosis and interbody fusion and the degree of kyphotic deformity was analysed using the modified Konstam's angle. RESULT: Two hundred and twenty-six lesions were found in the radiographs of 97 patients with 28.9% of them having multiple lesions. The mean ± SD preoperative, post-operative, and 2-year follow-up kyphotic angle were 49.5 ± 18.4°, 22.6 ± 7.1° and 24.5 ± 7.6°, respectively, and showed significant kyphosis correction (P < 0.01). Sclerosis was seen as early as 3 months in 82(84.5%) patients whereas interbody fusion started appearing at the end of 6 months in 38.14% of patients and peaked at 1 year. All patients recovered neurologically, with no significant loss of kyphosis correction, at final follow-up. CONCLUSION: The surgical technique described in this study had favourable clinical and radiological outcomes. Early surgery helps in having a definitive diagnosis and detects the presence of drug-resistant strains.

Morphometry of the lower thoracic and lumbar pedicles and its relevance in pedicle fixation.

PURPOSE: To assess the pedicle morphology in the lower thoracic and lumbar spine in an Indian population and to determine the causes of pedicle wall violation by pedicle screws. METHODS: Computerised tomographic scans of 135 consecutive patients with thoracolumbar and lumbar spine fractures were prospectively analysed to determine the pedicle morphology. The transverse pedicle angle, pedicle diameter and screw path length at 527 uninjured levels were measured. Post-operative CT scans of 117 patients were analysed to determine the accuracy of 468 pedicle screws at 234 vertebrae. RESULTS: The lowest (mean ± SD) transverse pedicle width in the lower thoracic spine was 5.4 ± 0.70 mm, whereas in the lumbar spine it was 7.2 ± 0.87 mm. The shortest (mean ± SD) screw path length in lower thoracic pedicles was 35.8 ± 2.10 and 41.9 ± 2.18 mm in the lumbar spine. The mean transverse pedicle angle in the lower thoracic spine was consistently less than 5°, whereas it gradually increased from L1 through L5 from 8.5° to 30°. Forty-one screws violated the pedicle wall, due to erroneous angle of screw insertion. CONCLUSIONS: In the current study, pedicle dimensions were smaller compared to the Western population. In Indian patients, pedicle screws of 5 mm diameter and 30 mm length, and 6 mm diameter and 35 mm length can safely be used in the lower thoracic and lumbar spine, respectively. However, it is important to assess the pedicle morphology on imaging prior to pedicle fixation.

Pedicle screw fixation in thoracolumbar and lumbar spine assisted by lateral fluoroscopic imaging: a study to evaluate the accuracy of screw placement.

BACKGROUND: The purpose of this study was to evaluate the accuracy of pedicle screw placement, its advantages, and limitations in posterior instrumentation of thoracolumbar and lumbar burst fractures assisted only by lateral fluoroscopic imaging. MATERIALS AND METHODS: Pre- and postoperative computerized tomographic (CT) scans of 117 patients with thoracolumbar and lumbar burst fractures, who underwent posterior instrumentation with pedicle screw fixation, were prospectively analyzed. Accuracy of screw placement, reconstruction of the vertebral height, and correction of the kyphotic angle were studied. Position of the pedicle screws were determined, and cortical breach was graded on the postoperative axial CT scans. Percentage of vertebral height reconstruction and kyphotic angle correction were calculated from the postoperative midsagittal CT scans. RESULTS: Four hundred and sixty-eight pedicle screws in 234 motion segments were included in this study. 427 screws were centrally placed with an accuracy rate of 91.24%. Out of the 41 (8.76%) screws that breached the pedicle wall, 32 (6.84%) screws had violated the medial wall, while 9 (1.92%) screws breached the lateral wall. There were no "air-ball" screws. No screw penetrated the anterior wall. Postoperatively, none of the patients deteriorated neurologically, and no screw required revision. Postoperatively, there was significant restoration of vertebral height and correction of kyphosis (P < 0.05). CONCLUSION: Pedicle fixation performed on a Relton-Hall frame is relatively simple and, when performed carefully using only lateral fluoroscopic imaging, has a lower potential for complications due to cortical breach.