The dual growing rod method using pedicle screws as foundation in the both of upper and lower spine

1
The dual growing rod method using pedicle screws
as foundation in the both of upper and lower spine

• Ken Yamazaki, MD Hideki Murakami, MD
• Iwate Medical University, Morioka, JAPAN
• yamaken_at_iwate-med.ac.jp

2
Introduction

• Recently, there are not a few reports on high
  complication rates and the failure of the growing
  rod to spinal deformities in an early onset
  scoliosis ( EOS ).
• We fundamentally choose pedicle screws on both
  ends under a CT based navigation system for small
  size pedicles. Strong construct using pedicle
  screws could allow correcting the curve earlier
  and keeping up with the growth of the spine.

3
Method

• Six patients were treated with a dual growing rod
  system with pedicle screws as a foundation in
  both ends from 01/2006 to 01/2009.
• The average age of 6 patients ( Boy Girl 5
  1 ) was 6.1 years ( 2 8 ).
• Diagnosis were idiopathic scoliosis ( 2 ), SOTOS
  ( 1 ), myelomeningocele ( 1 ), NF1 ( 1 ), and
  miscellaneous ( 1 ). All patients were followed
  for a minimum of 6 months ( 6 42 ).
• The frequency of lengthening was an average of
  2.8 times ( lengthening every six months ).

4
Results

• Pre op. Cobbs angle was an average of 68.7
  degrees ( 43 93 ). Post op. Cobbs angle
  decreased to an average of 28.7 degrees ( 13 52
  ). The Correction rate was an average of 60.2 (
  44 73 ).
• After 1st. op. their standing height increased an
  average 4.0cm ( 2.0 7.0 ).
• There were no major complications in any of the
  patients.

5
Patient 1 Infantile Idiopathic Scoliosis
75
19
10
21
30
16
14
T5-T12 20?
T5-T12 40?
T5-T12 14?
T5-T12 21?
T5-T12 25?
T5-T12 17?
T5-T12 28?
T5-T12 30?
Age 2Y9M 3Y3M
3Y9M 4Y4M 4Y11M 5Y6M
6Y1M Ht. 82.5cm ? 84.7cm ? 89.1cm ?
93.5cm ? 98.0cm ?101.2cm ?105.0cm? 109.2cm

Tandem Connector changed upper rods
changed
6
Patient 1 Infantile Idiopathic Scoliosis
Age 2Y9M 3Y8M 4Y11M
6Y1M Ht. 82.5cm 93.5cm
101.2cm 109.2cm

7
Patient 4 9Y1M Idiopathic Scoliosis
Mental retardation, Optic nerve
hypoplasia
16
15
47
10
12
T5-T12 16? Ht. 120.4cm
T5-T12 20? 124.4cm
T5-T12 19? 125.5cm
T5-T12 20? 127.7cm
T5-T12 20? 132.7cm
Pre OP 1st. OP 2nd. OP
3rd. OP 4th. OP 9Y1M
9Y8M 10Y4M
10Y10M
8
Patient 4 9Y1M Idiopathic Scoliosis
Mental retardation, Optic nerve
hypoplasia
Pre-OP. Intra-OP Post-OP After 4th. OP
9Y1M
10Y11M
9
Patient 5 6Y6MSpina bifida,
sryngomyeliaMeningocele op. at
birthTethered cord synd. op. 5Y10M
52
93
46
101.2cm 108.0cm
32
62
30
Pre OP . Post OP. 2nd. OP
6Y6M 7Y
10
Discussion
1. Hook vs. pedicle screw as anchor
Advantages

• Pedicle screw
• Rigid fixation
• Significantly better curve correction
• High fusion rate
• Simplification and shortening of postoperative
  external support

• Hook
• Relatively simple procedure
• Less possibility of both vascular and
  neurological complications

References

• The hook displacement rate was 21.4 in 28
  patients who underwent growing rod surgery.
  Thompson GH et.al . J Pediatr Orthop. 2007

• In the biomechanical study, a foundation
  composed of four pedicle screws implanted in two
  adjacent vertebral bodies provides the strongest
  construct.
• 
  Mahar AT et al. Spine 2007

11
2. Screwing into small diameter pedicles

• CT based navigation system for small size pedicles

T3
T3
T4
rt2.2mm
rt1.8mm
lt2.2mm
lt1.7mm
L2
L3
L2
L3
rt4.5mm
rt3.5mm
lt3.5mm
lt4.0mm

• Expansive tapping method

? 2nd step of the tapping (expansive
tapping)
? Probing
? 1st step of the tapping
Tapping using the thinnest size
of tapper (?tapper ? ?pedicle)
Probing using thinner probe
Tapping using the next thinnest size down
tapper to expand small pedicle (?tapper gt
?pedicle)
12
Conclusion

• The growing rod instrumentation with pedicle
  screws on both ends is a safe and effective
  method in controlling curve of EOS earlier in all
  three planes.
• With a careful technique, previously reported
  high complication rates in the growing rod system
  can be considerably decreased.