Rib Cage Measurement Reproducibility Using Biplanar Stereoradiographic 3D Reconstructions in Adolescent Idiopathic Scoliosis

Evaluation of Pulmonary Function After Halo-Pelvic Traction for Severe and Rigid Kyphoscoliosis Utilizing CT with 3D Reconstruction

BACKGROUND

The purpose of the present study was to evaluate changes in pulmonary function, caused by preoperative halo-pelvic traction (HPT) for the treatment of extremely severe and rigid kyphoscoliosis, with use of 3-dimensional computed tomography (3D-CT) reconstruction and pulmonary function tests (PFTs).

METHODS

Twenty-eight patients with severe and rigid scoliosis (Cobb angle, >100°) underwent preoperative HPT and staged posterior spinal fusion. CT, radiographic assessment, and PFT were performed during pre-traction and post-traction visits. The changes in total lung volume were evaluated with use of 3D-CT reconstruction, and the changes in pulmonary function were evaluated with PFTs at each time point. Differences were analyzed with use of 2-tailed paired Student t tests, and correlations were analyzed with use of Spearman rank tests.

RESULTS

None of the patients had pulmonary complications during traction, and all radiographic spinal measurements improved significantly after HPT. The main Cobb angle was corrected from 143.30° ± 20.85° to 62.97° ± 10.83° between the pre-traction and post-traction evaluations. Additionally, the C7-S1 distance was lengthened from 280.48 ± 39.99 to 421.26 ± 32.08 mm between the pre-traction and post-traction evaluations. Furthermore, 3D lung reconstruction demonstrated a notable increase in total lung volume (TLV) (from 1.30 ± 0.25 to 1.83 ± 0.37 L) and maximum lung height (from 176.96 ± 27.44 to 202.31 ± 32.45 mm) between the pre-traction and post-traction evaluations. Moreover, PFTs showed that total lung capacity (TLC) improved between the pre-traction and post-traction evaluations (from 2.06 ± 0.32 to 2.98 ± 0.82 L) and that the changes in T1-T12 distance and maximum lung height were correlated with changes in TLV (p = 0.0288 and p = 0.0007, respectively).

CONCLUSIONS

The application of HPT is a safe and effective method for improving pulmonary function in patients with extremely severe and rigid scoliosis before fusion surgery. The TLV as measured with CT-based reconstruction was greatly increased after HPT, mainly because of the changes in thoracic height.

LEVEL OF EVIDENCE

Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Global malalignment in adolescent idiopathic scoliosis: the axial deformity is the main driver

PURPOSE

To evaluate the global alignment of non-operated subjects with adolescent idiopathic scoliosis.

METHOD

A total of 254 subjects with AIS and 64 controls underwent low dose biplanar X-rays and had their spine, pelvis, and rib cage reconstructed in 3D. Global alignment was measured in the sagittal and frontal planes by calculating the OD-HA angle (between C2 dens to hip axis with the vertical). Subjects with AIS were classified as malaligned if the OD-HA was > 95th percentile relative to controls.

RESULTS

The sagittal OD-HA in AIS remained within the normal ranges. In the frontal plane, 182 AIS were normally aligned (Group 1, OD-HA = 0.9°) but 72 were malaligned (Group 2, OD-HA = 2.9°). Group 2 had a more severe spinal deformity in the frontal and horizontal planes compared to Group 1 (Cobb: 42 ± 16° vs. 30 ± 18°; apical vertebral rotation AVR: 19 ± 10° vs. 12 ± 7°, all p < 0.05). Group 2 subjects were mainly classified as Lenke 5 or 6. 19/72 malaligned subjects had a mild deformity (Cobb < 30°) but a progressive scoliosis (severity index ≥ 0.6). The frontal OD-HA angle was found to be mainly determined (adjusted-R² = 0.22) by the apical vertebral rotation and secondarily by the Lenke type.

CONCLUSIONS

This study showed that frontal malalignment is more common in distal major structural scoliosis and its main driver is the apical vertebral rotation. This highlights the importance of monitoring the axial plane deformity in order to avoid worsening of the frontal global alignment.

Estimating pulmonary function after surgery for adolescent idiopathic scoliosis using biplanar radiographs of the chest with 3D reconstruction

AIMS

This study addressed two questions: first, does surgical correction of an idiopathic scoliosis increase the volume of the rib cage, and second, is it possible to evaluate the change in lung function after corrective surgery for adolescent idiopathic scoliosis (AIS) using biplanar radiographs of the ribcage with 3D reconstruction?

METHODS

A total of 45 patients with a thoracic AIS which needed surgical correction and fusion were included in a prospective study. All patients underwent pulmonary function testing (PFT) and low-dose biplanar radiographs both preoperatively and one year after surgery. The following measurements were recorded: forced vital capacity (FVC), slow vital capacity (SVC), and total lung capacity (TLC). Rib cage volume (RCV), maximum rib hump, main thoracic curve Cobb angle (MCCA), medial-lateral and anteroposterior diameter, and T4-T12 kyphosis were calculated from 3D reconstructions of the biplanar radiographs.

RESULTS

All spinal and thoracic measurements improved significantly after surgery (p < 0.001). RCV increased from 4.9 l (SD 1) preoperatively to 5.3 l (SD 0.9) (p < 0.001) while TLC increased from 4.1 l (SD 0.9) preoperatively to 4.3 l (SD 0.8) (p < 0.001). RCV was correlated with all functional indexes before and after correction of the deformity. Improvement in RCV was weakly correlated with correction of the mean thoracic Cobb angle (p = 0.006). The difference in TLC was significantly correlated with changes in RCV (p = 0.041). It was possible to predict postoperative TLC from the postoperative RCV.

CONCLUSION

3D rib cage assessment from biplanar radiographs could be a minimally invasive method of estimating pulmonary function before and after spinal fusion in patients with an AIS. The 3D RCV reflects virtual chest capacity and hence pulmonary function in this group of patients. Cite this article: Bone Joint J 2022;104-B(1):112-119.

A Novel Classification of 3D Rib Cage Deformity in Subjects With Adolescent Idiopathic Scoliosis

STUDY DESIGN

This was a multicentric cross-sectional descriptive study.

OBJECTIVE

To analyze patterns of 3D rib cage deformity in subjects with adolescent idiopathic scoliosis (AIS) and their relationship with the spinal deformity.

SUMMARY OF BACKGROUND DATA

Subjects with AIS present with rib cage deformity that can affect respiratory functions. The 3D rib cage deformities in AIS and their relationship to the spinal deformity are still unelucidated.

METHODS

A total of 200 AIS and 71 controls underwent low-dose biplanar x-rays and had their spine and rib cage reconstructed in 3-dimensional (D). Classic spinopelvic parameters were calculated in 3D and: rib cage gibbosity, thickness, width, volume and volumetric spinal penetration index (VSPI). Subjects with AIS were classified as: group I with mild rib cage deformity (n=88), group II with severe rib cage deformity (n=112) subgrouped into IIa (high gibbosity, n=48), IIb (high VSPI, n=48), and IIc (both high gibbosity and VSPI, n=16).

RESULTS

Groups IIa and IIb had a higher Cobb angle (33 vs. 54 degrees and 46 degrees, respectively) and torsion index (11 vs. 14 degrees and 13 degrees, respectively) than group I. Group IIb showed more severe hypokyphosis (IIb=21 degrees; IIa=33 degrees; I=36 degrees; control=42 degrees) with a reduced rib cage volume (IIb=4731 cm3; IIa=4985 cm3; I=5257 cm3; control=5254 cm3) and thickness (IIb=135 mm; IIa=148 mm; I=144 mm; control=144 mm). Group IIa showed an increasingly large local gibbosity descending from proximal to distal levels and did not follow the axial rotation of the spine. Group IIc showed characteristics of both groups IIa and IIb.

CONCLUSIONS

This new classification of 3D rib cage deformity in AIS shows that the management of cases with high VSPI (groups IIb and IIc) should focus on restoring as much kyphosis as possible to avoid respiratory repercussions. Treatment indications in groups I and IIa would follow the consensual basic principles reported in the literature regarding bracing and surgery.

The Relationship Between 3-dimensional Spinal Alignment, Thoracic Volume, and Pulmonary Function in Surgical Correction of Adolescent Idiopathic Scoliosis: A 5-year Follow-up Study

STUDY DESIGN

Retrospective review of a prospective multicenter database.

OBJECTIVE

The aim of this study was to study the effects of thoracic kyphosis (TK) restoration in adolescent idiopathic scoliosis (AIS) Type 1 and 2 curves on postoperative thoracic volume (TV) and pulmonary function.

SUMMARY OF BACKGROUND DATA

Surgical correction of AIS is advocated to preserve or improve pulmonary function, prevent progressive deformity and pain, and improve self-appearance. Restoration of sagittal and 3D alignment, particularly TK, has become increasingly emphasized in efforts to improve pulmonary function, TVs, sagittal balance, and prevent adjacent-segment degeneration and deformity.

METHODS

AIS patients 10 to 21years undergoing surgical correction of Lenke Type 1 and 2 curves with baseline, 1-erect-postoperative, and 5-year (5Y) postoperative visits including stereoradiographic assessment and pulmonary function tests (PFTs) were included. 3D-radiographic analysis was performed to assess spinal-alignment, chest-wall, and rib-cage dimensions at each time point. Outcome variables were analyzed between time points with one-way analysis of variance and between variables with linear regression analysis.

RESULTS

Thirty-nine patients (37 females, 14.4 ± 2.2 years) were included. 3D-spinal-alignment analyses demonstrated significant reduction in preoperative to first-erect thoracic and lumbar Cobb-angles, an increase in TK:T2-12 (19.67°-39.69°) and TK:T5-12 (9.47°-28.05°), and reduction in apical vertebral rotation (AVR) (P < 0.001 for all). Spinal-alignment remained stable from 1-erect to 5Y. 3D rib-cage analysis demonstrated small reductions in baseline to first-erect depth (145-139 mm), width (235-232 mm), and increase in height (219-230 mm, P < 0.01), but no significant change in volume (5161-5222 cm,P = 0.184). From 1-erect to 5Y, significant increases in depth, width, height, and volume (all P < 0.001) occurred. PFTs showed preoperative to 5Y improvement in first second of Forced Expiratory Volume (FEV1) (2.74-2.98 L, P = 0.005) and forced vital capacity (FVC) (3.23-3.47 L, P = 0.008); however, total lung capacity (TLC) did not change (P = 0.517). Percent-predicted TLC decreased (Pre: 101.3% to 5Y: 89.3%, P < 0.001); however, percent-predicted forced expiratory volume and FVC did not (P = 0.112 and P = 0.068).

CONCLUSION

Although TK increases, coronal-Cobb and AVR decrease postoperatively; these do not directly influence TV, which increases from 1-erect to 5Y due to growth, corresponding with increases in FEV1 and FVC at 5Y; however, surgical restoration of kyphosis does not directly improve pulmonary function.

LEVEL OF EVIDENCE

3.

Trunk Growth in Early-Onset Idiopathic Scoliosis Measured With Biplanar Radiography

STUDY DESIGN

Cross-sectional and longitudinal retrospective study.

OBJECTIVES

To measure thoracic dimensions and volume during growth in early-onset idiopathic scoliosis (EOIS) patients and to compare them to a population of asymptomatic adults and to the previous literature.

SUMMARY OF BACKGROUND DATA

Data on trunk growth for scoliotic children between 6 and 14 years of age is sparse in the literature.

METHODS

Thirty-six patients (29 girls and 7 boys, between 3 and 14 years old, average Cobb angle 33°±15°) were included, all with a minimum two-year follow-up. Sixty-one asymptomatic girls and 54 asymptomatic adults were included as control groups. All subjects underwent biplanar radiography and 3D reconstruction of the spine, pelvis, and rib cage. EOIS patients repeated their radiologic examination every six months. Cobb angle, rib cage volume, anteroposterior and transverse diameters, thoracic index, thoracic perimeter, pelvic incidence, and T1-T12 and T1-S1 distance were calculated. Reproducibility of measurement was assessed.

RESULTS

Measurement reliability in such young patients was comparable to previous studies in adolescents and adults. Geometrical parameters of EOIS patients increased linearly with age. For instance, rib cage volume in girls with EOIS increased from 2200 cm³ at six to seven years of age to 4100 cm³ at 13-14 years (65% of adult values, 294 cm³/y). Comparison with asymptomatic girls showed that EOIS could affect growth spurt. Longitudinal analysis on a cohort of six girls who had a follow-up of six years confirmed the cross-sectional data.

CONCLUSIONS

In this longitudinal and cross-sectional study, trunk growth between 3 and 14 years of age was characterized, for the first time, with biplanar radiography and 3D reconstruction. The results can be useful to estimate patient growth and thus have potential application in the surgical planning of EOIS patients.

LEVEL OF EVIDENCE

Level II, retrospective study.