Aim:

To evaluate the effect of a stiffer rod in normalising thoracic hypokyphosis in adolescent idiopathic scoliosis (AIS).

Pedicle screw constructs (PSC) in scoliosis are a recently established and widely accepted method of managing scoliotic curves posteriorly. There is a perceived improved coronal and rotational correction when compared to other posterior only constructs. With continued use of this method, the authors and deformity surgeons in general have become aware of persistent thoracic hypokyphosis.

This review of 3 years of scoliosis cases using PSC looks at four different implant strategies utilised to manage this problem and our current practice. These strategies were:

All titanium 5.5 mm rod diameter (Expedium, Depuy spine)

All titanium 5.5 mm rod diameter with periapical washers (Expedium, Depuy spine)

All titanium 6.0 mm rod diameter (Pangea, Synthes)

Titanium pedicle screws with 5.5 mm diameter cobalt chrome rods (Expedium Depuy spine)

We have reviewed our outcomes with these strategies with respect to thoracic hypokyphosis. Strategy 1 had the highest rate of hypokyphosis on postoperative radiographs. Strategy 4 seems to have the best correction of coronal and sagittal plane abnormality post operatively. As a consequence, our current practice is the use of titanium pedicle screws and 5.5 mm diameter cobalt chrome rods when managing scoliosis with a pedicle screw construct.

Purpose of the study: The long-term results after surgical treatment of idiopathic scoliosis depends not only on the correction in the coronal plane but also the restoration of good sagittal balance and thus satisfactory sagittal curvatures. Recent publications have shown moderate correction of the thoracic hypokyphosis of idiopathic scoliosis with instrumentations using hooks and pedicular screws. We report results in the coronal and sagittal play with a reduction technique by simultaneous translation on two rods (ST2R).

Material and method: The radiographic parameters were measured preoperatively, at 6 weeks, at 1 year, and at last follow-up (range 2 – 7.4 years) in a consecutive series of 72 patients treated with posterior instrumentation and reduction using the ST2R system. The same operator performed all procedures using stable anchors (pedicle screws or self-stabilizing clamps). Screws and clamps had a threaded polyaxial extension which was linked to the rod by a connector. The deformity was reduced by progressively tightening the two rods alternatively using the nuts on the threaded extensions. This manoeuvre enabled the vertebrae to migrate progressively toward the rods, producing an anteroposterior translation.

Results: In the coronal plane, the mean main curvature was reduced from 54 to 17 and was maintained (70%) without loss of angle at last follow-up. There was not difference between the 56 patients with thoracic scoliosis (Lenke 1–4) and the 16 patients with thoracolumbar or lumbar scoliosis (Lenke 5 and 6). In the sagittal plane, for the patients with preoperative hypokyphosis (32 patients < 20), the mean kyphosis was significantly improved from 9 to 30 and remained stable at last follow-up (31) with a mean gain of 21 (p< 0.001). One patient still had hypokyphosis (18) at last follow-up. For patients with normal kyphosis preoperatively (> 20), the mean gain was 7.

Conclusion: In this consecutive series of 72 adolescents with idiopathic scoliosis, reduction by simultaneous translation on two rods was a simple and effect method which restored normal thoracic kyphosis.

Introduction: The clinically significant threshold above which a scoliotic curve could be abnormal remains arbitrary. Data on normal adolescent and adult back shape are scarce. However clinical decision making based on subjective, visual criteria influences management. We aimed to produce measurable values of normal back shape, against which deformity could be defined. Method: 48 volunteering young adults perceiving themselves as “normal” participated in the study. All have been cleared previously by school screening. Their age (18–28 years old) precluded curve deterioration, but was close enough to adolescent measurements at the end of growth. Back shape was assessed with the ISIS system. Results: A minority of 8% showed no curve, with 54% a single curve and the rest a double one. Right spinal asymmetry (77%) was more frequent than the left (52%). Mean values and 95% confidence intervals were 16.1° (14.0°–18.2°) for upper spinal asymmetry, 13.4° (10.1°–16.6°) for lower lateral asymmetry, 24.9 mm (20.6 mm–29.2 mm) for thoracic kyphosis and 14.9 mm (12.5 mm–17.2 mm) for lumbar lordosis. Increasing upper lateral asymmetry correlated with decreasing thoracic kyphosis (p< 0.01). Maximum skin surface angle correlated positively with only upper lateral asymmetry (p< 0.001). Conclusion: Normal spines comprise of lateral asymmetries, where straight is the exception more than the rule. Scoliosis seems to be an exacerbation of this lateral asymmetry beyond 18° for the upper and 16° for the lower spinal asymmetry. Hypokyphosis is related to upper lateral spinal asymmetry. Skin surface angle is a very good indicator of only the upper lateral asymmetry

Aims

This systematic review aims to identify 3D predictors derived from biplanar reconstruction, and to describe current methods for improving curve prediction in patients with mild adolescent idiopathic scoliosis.