A total of 116 patients with curves > 100° were treated between 2012 and 2016. Ninety-eight (98) patients met the inclusion criteria and were classified into their respective categories using the aforementioned classification scheme detailed in the methods. The classification scheme yielded a total of 4 main types (1, 2, 3 and 4) and 6 subtypes under types 1 and 2 (1C, 1S, 1CS, 2P, 2D and 2PD) (Table 1). A summary of demographic and radiographic data is shown in Tables 2 and 3, respectively. Post-halo-gravity radiographic results are shown in Table 4. A detailed analysis of each curve, its characteristics and response to halo-gravity traction is described below.
Type 1C in which the coronal curve alone measures > 100° is depicted in Fig. 2. Nine (8 females, 1 male, mean age 17.7 ± 3.7 years) out of 98 patients (9.1%) met this description. The most common diagnosis was idiopathic (6), followed by congenital (2) and neuromuscular (1). The mean coronal and sagittal Cobb angles were 120° ± 8.2° and 81.6° ± 18.1°, respectively. All patients in this category underwent halo-gravity traction (mean 77.7 ± 59.5 days) and achieved a mean correction of 26 ± 2.2% in the coronal curve and 46.3 ± 39.8% in the sagittal curve.
Figure 3 shows an example of type 1S kyphoscoliosis described as a having only the sagittal Cobb of > 100°. There were 2 patients (2.6%), mean age 13.2 years, in this subtype, and both were diagnosed with congenital scoliosis. The mean coronal and sagittal Cobb angles were 79.6° and 113.2°, respectively. Both patients in this subtype underwent halo-gravity traction for 30 days which resulted in a mean correction of 30.5% and 33.3% in the coronal and sagittal curves, respectively.
The 1CS (coronal > 100°, sagittal > 100°) is shown in Fig. 4. The 1CS represented the most common subtype in our cohort consisting of 43 patients (55%), 23 males and 20 females. The mean age was 17.5 ± 4 years. The diagnosis consisted of idiopathic (29), congenital (13) and neuromuscular (1). The mean coronal and sagittal Cobb angles were 127.7° ± 15.8° and 131.8° ± 21.0°, respectively. All 43 patients in this category underwent halo-gravity traction (mean 82.4° ± 67.3° days). The mean correction post-traction in the coronal and sagittal curves was 28.1 ± 10.9% and 30.9 ± 12.5%, respectively.
Type 2P curves (coronal and/or sagittal curves > 100° with UEV positioned at or below the apical vertebra) are shown in Fig. 5. This group consisted of 21 patients (27%), 8 females, 13 males, mean age 18.9 ± 5.8 years. The diagnosis in this category consisted of 11 idiopathic, 6 congenital, 2 neuromuscular and 2 neurofibromatosis. The mean coronal and sagittal Cobb angles were 145.9° ± 27.6° and 169.3° ± 14.5°, respectively. All patients underwent halo-gravity traction (mean 106 ± 42.9 days). The mean correction in the coronal and sagittal curves was 35.6 ± 12.3% and 33 ± 7.2%).
Type 2D curves (coronal and/or sagittal curves > 100° with LEV positioned at or above the apical vertebra) consisted of 2 female patients (2.6%), mean age 19.5 years. The diagnosis in this category consisted of 1 idiopathic and 1 congenital scoliosis. The mean coronal and sagittal Cobb angles were 135.6° and 157.5°, respectively. Both patients in this subtype underwent halo-gravity traction for 72 days (mean) which resulted in a mean correction of 20.1% and 9.6% in the coronal and sagittal curves, respectively. A representative example of this subtype is shown in Fig. 6.
The type 2PD curve (coronal and/or sagittal curves > 100° with both UEV and LEV are either positioned at the level of, below or above the apical vertebra) was the least common type of curve and consisted of only a 22-year-old female patient. The coronal and sagittal Cobb angles were 171° and 176°, respectively. After 205 days in traction, the curve improved by 22% and 3% in coronal and sagittal planes, respectively. Figure 7 illustrates the radiographs and 3-D reconstruction images for this patient.
Type 3: gamma (γ)
Type 3 curves exhibited a complete vertebral transposition in the sagittal plane (Fig. 8). There were 16 patients (9 female, 7 males), mean age of 17.9 ± 4.1 in this category. Unlike the omega deformities in which both coronal and sagittal curves are large in magnitude, the gamma (γ) curves principally occurs in the sagittal plane with little to no angular deformity in the coronal plane. The mean sagittal Cobb was 216.7° ± 22.2°. The final measurement is reached by adding the angle subtended by the overlapping segments to 180° (Fig. 9). All patients underwent halo-gravity traction (mean 125 ± 49.6 days). The mean correction kyphosis following halo-traction was 157.8° ± 58.8°.
Type 4; alpha (α)
This curve type consisted of a vertical proximal segment, horizontal middle segment and a vertical distal segment represented the most severe of the curves (Fig. 10). Similar to gamma (γ) curves, this curve type can only be appreciated with a 3-D CT. A plain CT will underestimate the severity of this curve and could lead in inappropriate treatment. There were a total of 4 patients (2 males, 2 females), mean age 17.2 ± 4.2. Using the gamma measurement technique, the mean preoperative sagittal Cobb was 238° ± 6.5°. The mean correction measurement following halo-traction was 238.3° ± 10.9° indicating a lack of response to halo-traction in this subtype.