Agreement Between Manual and Computerized Designation of Neutral Vertebra in Idiopathic Scoliosis

Side bending radiographs and lowest instrumented vertebra in adolescent idiopathic scoliosis: A French quality-of-care study

BACKGROUND

Determining which spinal levels to instrument during surgical treatment of Lenke Type 1 adolescent idiopathic scoliosis (AIS) depends on the reducibility of the primary and secondary curve patterns. This reducibility can be evaluated in several ways, with the most popular being radiographs in bending for moderate thoracic and lumbar curvatures. Hypothesis Side-bending radiographs will alter the choice of the lowest instrumented vertebra (LIV) for the surgical treatment of AIS.

METHODS

Thirteen experienced French spine surgeons were invited to perform surgical planning on 23 patients based on stereoradiographs with and without (standing) side-bending views. The surgical planning was repeated a second time to assess the intra- and inter-rater reliability. Variations in the choice of LIV were analyzed for each evaluation.

RESULTS

The intra-rater reliability was moderate to substantial. The inter-rater reliability was low to moderate. The study compared 879 surgical plans. Selective fusion was chosen in 0.3% of the plans. The median LIV was L2. The availability of side bending views changed the plan in 39% of cases. However, 36% of the plans were changed in the control (test-retest) condition. No significant difference was found between the variations with side-bending radiographs and "control" variations (p>0.05).

CONCLUSION

The use of radiographs in bending has no significant effect on the LIV choice in this study. This result is derived from statistically robust analysis made possible by one of the largest datasets available on this topic. Large inter-rater variability was observed and will be explored further in a future study.

LEVEL OF EVIDENCE

II; non-randomized controlled comparative study.

Discovering the association between the pre- and post-operative 3D spinal curve patterns in adolescent idiopathic scoliosis

BACKGROUND

The advantage of considering the three-dimensional curve patterns, including the patterns of the vertebral position and alignment, in classification of adolescent idiopathic scoliosis (AIS) patients and whether such classification system relates to the surgical outcomes are not fully determined.

METHODS

A total of 371 AIS patients who received posterior spinal fusion surgery with 2-year follow-up were included retrospectively and consecutively. The 3D positions and orientations of the T1-L5 vertebrae were calculated from the 3D reconstructions of the spines at pre-operative and 2-year follow-up, a total of 102 variables per patient. A probabilistic clustering method was used to cluster the pre-operative and 2-year follow-up 3D spinal curve patterns separately. The distributions of the Lenke types and 3D pre-operative clusters in the post-operative clusters were determined.

RESULTS

A total of nine pre-operative clusters including, four right thoracic types, three left thoracolumbar/lumbar types, one low apex right thoracic/thoracolumbar, and one left thoracic/right lumbar were determined. Three post-operative 3D curve patterns were Type 1 with higher residual proximal Cobb angle, Type 2 with lower T5-T12 kyphosis and highest pelvic incidence-lordosis mismatch, and Type 3 with larger lumbar curve magnitude and rotation compared to the other two groups. More than 50% of patients in each of the 3D pre-operative clusters had the same post-operative group.

CONCLUSION

We developed a 3D classification of the AIS patients before and two-year after spinal fusion surgery. The link between the pre- and post-operative clusters lends itself to application of this classification system in developing predictive models of the AIS surgical outcomes.

Selection of the lowest instrumented vertebra in main thoracic adolescent idiopathic scoliosis: Is it safe to fuse shorter than the last touched vertebra?

HYPOTHESIS

Fusing shorter than the last touched vertebra (LTV) is a safe approach in flexible main thoracic (MT) adolescent idiopathic scoliosis (AIS) curves.

METHODS

This was a prospective study on consecutive AIS patients surgically treated with selective fusion of the MT curve. Fusion-level selection was based on the fulcrum-bending radiograph method. Patients were grouped based on the position of the lowest instrumented vertebra as proximal to the LTV (proxLTV, n = 43), at the LTV (atLTV, n = 45), and distal to the LTV (distLTV, n = 21).

RESULTS

A total of 109 patients were included in the study. Preoperatively, the distLTV group had greater lumbar Cobb angle, lumbar apical translation, and less flexibility in the MT curve. At 2-year follow-up, the groups did not differ in MT curve correction, but the distLTV had larger lumbar Cobb angle, more apical translation, and worse coronal balance. Distal adding-on was observed in 11 patients (26%) in the proxLTV group, four patients (9%) in the atLTV group, and one patient (5%) in the distLTV group (p = 0.031). Adding-on was associated with younger patients and lower Risser grade at the time of surgery but not with any other radiographic parameter. No differences in SRS-22r scores were observed between the groups.

CONCLUSIONS

Proximal fusion carries the risk of adding-on, but leaving unfused segments in the lower spine increases the potential for compensatory mechanisms to improve spinal and truncal balance. In mature patients with a flexible MT curve, surgeons may consider fusion at or cranial to the LTV.

Defining criteria for optimal lumbar curve correction following the selective thoracic fusion surgery in Lenke 1 adolescent idiopathic scoliosis: developing a decision tree

OBJECTIVE

The aim of this study was to identify the range of optimal versus suboptimal rates of spontaneous lumbar Cobb correction (SLCC%) and the factors predicting such outcomes in a cohort of Lenke 1 adolescent idiopathic scoliosis (AIS) after posterior spinal fusion surgery.

METHODS

Seventy-one consecutive Lenke1 B and C AIS patients with a fusion level to L1 and higher with two-year follow-up were included. Thoracic kyphosis (T1-T4 and T4-T12 TK), lumbar lordosis (L1-S1 LL), thoracic and lumbar Cobb angles, thoracic and lumbar apical vertebral rotations and translations (AVR and AVT), pelvic incidence, sacral slope, and sagittal and frontal balances were measured at preoperative, early postoperative, and two-year follow-up. The SLCC% was calculated between preoperative and two-year follow-up. A clustering analysis determined the subgroups of patients with significantly higher and lower (optimal versus suboptimal) rate of SLCC% in the cohort at two-year follow-up. The cutoff values of the preoperative and early postoperative radiographic parameters that significantly predicted the optimal and suboptimal SLCC% were determined using a decision tree.

RESULTS

The averages of the optimal versus suboptimal range of SLCC% in the cohort were 72% [55%, 105%] versus 39% [- 7%, 42%]. Preoperative and early postoperative spinal parameters predicted the optimal versus suboptimal SLCC% with an accuracy of 82%, 95%CI [0.73-0.94]. Preoperative AVT_Lumbar < 10 mm was a predictor of optimal SLCC%. In patients with a preoperative AVT_Lumbar > 10 mm, early postoperative T4-T12 TK < 24° (but not less than 17°) accompanied by - 5° < AVR_Thoracic < 5° were the main predictors of optimal SLCC% in our cohort.

CONCLUSION

Quantitative clustering of the SLCC% into optimal and suboptimal groups allowed identifying the cutoff values of preoperative (AVT_Lumbar) and early postoperative (T4-T12 TK and AVR_Thoracic) spinal parameters that can predict the optimal range of SLCC% at two-year postoperative in our cohort of Lenke 1 AIS.

LEVEL OF EVIDENCE

IV.

A hierarchical classification of adolescent idiopathic scoliosis: Identifying the distinguishing features in 3D spinal deformities

This study aimed to identify the differentiating parameters of the spinal curves’ 2D projections through a hierarchical classification of the 3D spinal curve in adolescent idiopathic scoliosis (AIS). A total number of 103 right thoracic left lumbar pre-operative AIS patients were included retrospectively and consecutively. A total number of 20 non-scoliotic adolescents were included as the control group. All patients had biplanar X-rays and 3D reconstructions of the spine. The 3D spinal curve was calculated by interpolating the center of vertebrae and was isotropically normalized. A hierarchical classification of the normalized spinal curves was developed to group the patients based on the similarity of their 3D spinal curve. The spinal curves’ 2D projections and clinical spinal measurements in the three anatomical planes were then statistically compared between these groups and between the scoliotic subtypes and the non-scoliotic controls. A total of 5 patient groups of right thoracic left lumbar AIS patients were identified. The characteristics of the posterior-anterior and sagittal views of the spines were: Type 1: Normal sagittal profile and S shape axial view. T1 is leveled or tilted to the right in the posterior view. Type 2: Hypokyphotic and a V shape axial view. T1 is tilted to the left in the posterior view. Type 3: Hypokyphotic (only T5-T10) and frontal imbalance, S shape axial view. T1 is leveled or tilted to the right, and 3 frontal curves. Type 4: Flat sagittal profile (T1-L2), slight frontal imbalance with a V shape axial view, T1 tilted to the left. Type 5: flat sagittal profile and forward trunk shift with a proximal kyphosis and S shape axial view. T1 is leveled or tilted to the right. In conclusion, a hierarchical classification of the 3D scoliotic spine allowed identifying various distinguishing features of the spinal curves in patients with a right thoracic curve in an orderly fashion. The subtypes’ characteristics resulting from this 3D classification can be identified from the pairs of the frontal and sagittal spinal curves i.e. X-rays in right thoracic AIS patients.