Significance of peak height velocity as a predictive factor for curve progression in patients with idiopathic scoliosis

Background

Much attention has been paid to peak height velocity (PHV) as a possible predictor
of curve progression in patients with idiopathic scoliosis (IS). The aim of this study
was to analyze the relationship between the magnitude of the Cobb angle at PHV and
scoliosis progression, defined as having surgery prior to skeletal maturity in female
patients with IS.

Methods

A retrospective review identified 56 skeletally immature female IS patients who were
followed until maturity. The mean age and the mean pubertal status at the initial
visit were 10 years and 24 months before menarche respectively, with a follow-up period
of 5 years. They were divided into two groups: non-surgery group (NS) and surgery
group (S), depending on their treatment method in use at the final follow-up visit.
Surgery group was defined as an ultimately having surgery due to Cobb angle greater
than 45 degrees prior to skeletal maturity regardless of conservative management.
Height measurements were recorded at each visit; height velocity was calculated as
the height change, in cm, divided by the time interval, in years. The PHV, chronological
age at PHV (APHV), height at PHV (HPHV), and final height (FH) were determined for
each group. In patients with Cobb angle greater than 30 degrees, the corrected height
was calculated by Kono formula and corrected height velocity values were provided.
The sensitivity, specificity, and area under the curve (AUC) of the receiver-operating
-characteristic (ROC) analysis were calculated to predict spinal curve progression
for various Cobb-angle cutoff values at PHV.

Results

The corrected PHV had a mean value of 8.5 and 8.9 cm/year in the NS-group and S-group,
respectively. The APHV was 11.9 and 11 years, the corrected HPHV was 152.9, and 149.3
cm, and the corrected FH was 159.9 and 159.3 cm, respectively. When a Cobb angle of
31.5 degrees was at PHV, ROC analysis revealed 78% sensitivity, 82% specificity, and
an AUC of 0.93, acceptable values for curve progression in patients with IS.

Conclusions

These findings indicate that 31.5 degrees of spinal curvature when patients are at
PHV is a significant predictive indicator for progression of the curve to a magnitude
requiring surgery. We suggest that the curve-progression risk assessment in patients
with IS should include PHV, along with measures of skeletal and non-skeletal maturities.