The Journal of Bone and Joint Surgery, Vol 77, Issue 1 39-45, Copyright © 1995 by Journal of Bone and Joint Surgery, Inc
Posterior arthrodesis and instrumentation in the immature (Risser-grade-0) spine in idiopathic scoliosis
JO Sanders, JA Herring and RH Browne
Texas Scottish Rite Hospital for Children, Dallas.
We performed a retrospective study of the long-term results of posterior
instrumentation and arthrodesis of the spine in forty-three patients who
had idiopathic scoliosis and a Risser grade of 0 at the time of the
operation. The average age of the patients was 12.4 years (range, 6.7 to
15.5 years) at the time of the operation. The triradiate cartilages were
open in twenty-three patients and closed in twenty. At the time of the
latest follow-up evaluation (average duration of follow-up, four years;
range, two to eleven years), seventeen patients had a Risser grade of 5;
twenty-two, 4; two, 3; one, 2; and one, 0. The crankshaft phenomenon, a
progressive deformity resulting from continued growth of the anterior
aspect of the spine after posterior arthrodesis, was seen in only one
patient who had closed triradiate cartilages and in ten patients who had
open triradiate cartilages (p = 0.004). The most common radiographic
finding was a progressive rib-vertebra angle difference, which increased
more than 10 degrees in seven of the eleven patients who had the crankshaft
phenomenon. The mean increase in these eleven patients was 22 degrees,
compared with no increase in the thirty-two other patients (p < 0.0001).
Open triradiate cartilages (r = 0.58, p = 0.0001) and a younger age at the
time of the operation (p < 0.0001) were predictive of the amount of
progression as a result of the crankshaft phenomenon. In patients who had
open triradiate cartilages, less skeletal maturity was also predictive of
progression as a result of the crankshaft phenomenon (r = -0.72, p =
0.0002).
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