Low density implants in correction of AIS

4. AIS
-Adolescent idiopathic scoliosis (AIS) is the most common form
of pediatric scoliosis. It occurs between the ages of 10 to 18.
-Surgical treatment is indicated to halt curve progression and
improve cosmetic appearance.
-The main goal of surgery is to achieve correction of deformity
including rotation, a fusion of the structural deformity of the
spine, which will prevent further progression.

5. Implant density is defined as number of implants per
spinal level fused. The ideal metal density in AIS is
unknown but would be the lowest metal density to achieve
satisfactory patient outcomes without increased
complications.

Implant Density

6. - Bilateral placement of pedicle screws at
every level has commonly been used.
- This method provides maximal rigidity to the scoliosis
construct.
-Disadvantages: Increased operative time
,risk of screw malposition and increased cost and blood
loss

All Screws Technique:

8. Aim Of The Work:
The aim of this study is to evaluate short term results of Low density
implants in correction of adolescent idiopathic scoliosis

9. Patient and Methods
-Patient selection
-Family counseling
-Preoperative Evaluation

10. 1- Inclusion criteria:
-Age (10-16) years old.
-Both sexes
-Lenke 1, 2, 3,4,5,6.
2- Exclusion criteria:
-Non idiopathic scoliosis.
-Previous spine surgery.
Patient selection

11. Family counseling
-AIS is primarily a cosmetic deformity
-Treatment was based on the desire to
change the shape of the back .

12. Preoperative Evaluation
-History taking :
-Personal history:.
-Evidence of maturation: included signs of puberty, onset of menarche.
-Presenting complaint
-History of present condition: the Age of onset, course and duration of
symptoms & evidence of maturation.
-Neurological symptoms
-Exclusion of non-idiopathic scoliosis criteria :

13. Physical Examination
-Assessment of shoulder balance
-Assessment of waist crease/pelvic obliquity
-Presence of any cutaneous abnormalities
-Indicators of maturity
-Gait
-Sensory and motor examination
-Reflex examination
-Forward Bending Test

14. Investigations
-Laboratory Investigations
-Pulmonary Function Test if curve more than 60
:
-Radiological Investigations
A-Essential radiographs
B-Measuring Cobb angle
C-Determination of stable and
neutral vertebra

15. A-Essential radiographs

16. B-Measuring Cobb angle

17. C-Determination of stable and
neutral vertebra

18. Assessment of Vertebral
Alignment and Balance

19. Pelvic parameters

20. Lenke classification system

21. Operative Details
-Anesthesia
-Bleeding Management
-Preoperative antibiotics
-Patient Positioning
-Neuromonitoring
-Surgical Technique:
All patients were treated by Correction derotation of curves by
low density implants construct less than 1.6 screw per level

22. Wide sub periosteal exposure of the
spine out to the tips of the transverse
processes

23. Pedicle Screw Insertion

25. Confirmation of the location of the bilateral
vertebral pedicles, screws were placed in an
anatomic position

26. Selection of Fused Levels
The upper instrumented vertebra was
T4 if high right shoulder (with MT curve ) .
T3 if balanced shoulders .
T2 if the high left shoulder .
In Lenke 5 with lumbar curve, fusion stopped at T10 or T9.
The lower instrumented vertebra was the end vertebra if it was
touched by the CSVL and end+1 or end+2 if the end vertebra was not
touched by CSVL .
.

27. Release
-Removal of the interspinous ligaments and midline
ligamentum flavum of the apical regions of the
deformity.
-Costotransversectomy was done to increase spinal
flexibility and facilitates correction technique.
- Costoplasty was done for cases had huge rib hump.

28. Correction maneuver:

30. Decortication of laminea & bone
grafting

31. Insertion of sub cutaneous
suction drain then wound
closure in layers.

32. Postoperative Management
-Day 0 : ICU & pain management
-Day1 : Patients were moved to the ward ,clinical
assessment and radiological imaging was done.
-Mobilization: Early mobilization out of bed was preferably
started the day after surgery.
-We used a postoperative dorsolumbar brace for 3 months
-Hospital discharge: Patients were discharged on 5th or 6th
day postoperatively.

33. Regular visits post-operative
-14th days: Stitches removal
-One month -3 months-6 months -1 year: Patients will be assessed
Functionally (SRS – 30 questionnaire) and Radiologically
-Radiological outcomes:
Cobbs angle (pre , post 3,6,12 m)
Correction degree
screw density
Loss of correction

34. Case presentation 1
Female patient 16 years old
with AIS Lenke type 3.
Pre Cobb's angle of major
curve was (75⁰),
Pre-operative SRS score was
65

35. She underwent posterior fusion and correction from
T4 to L3 with low density implants (1.58 screw /
level)

36. Final Follow Up at 12 months
-Initial post: 20⁰
-After 3m: 21⁰
-After 6m:23⁰
-After 12 m: 23⁰
-(SRS score = 127)
-Loss of correction : 3⁰ -5,45%.

38. Case presentation 2
Male patient 15 years old
with AIS Lenke type 5.
Pre Cobb's angle of major
curve was (74⁰),
Pre-operative SRS score was
76

39. He underwent posterior fusion and correction
from T5 to L5 with low density implants (1.46)

40. Final Follow Up at 12 months
-Initial post: 28⁰
-After 3m: 29⁰
-After 6m:29⁰
-After 12 m: 30⁰
-(SRS score = 120)
-Loss of correction : 2⁰ -4.34%.

42. Results

43. Demographic Data
Gender No. %
Female 28 93.3
Male 2 6.7
I
II
III
IV
V
VI

44. Cases
(n = 30)
Operative time
Range. 201 – 313
Mean ± SD. 258.57 ± 34.42
Blood loss
Range. 290 – 1360
Mean ± SD. 837 ± 307.38
Screw density
Range. 1 – 1.6
Mean ± SD. 1.23 ± 0.2
Blood transfusion No. %
No 21 70.0
Yes 9 30.0
Hospital stay
Range. 3 – 5
Intraoperative Data

45. Functional Outcomes
0
20
40
60
80
100
120
140
SRS
Pre-operative
Post-operative

46. Radiological Outcomes
60.47
19.1
0
10
20
30
40
50
60
70
80
COBB
Mean
±SD
Pre-operative Post-operative
Cobb's
Preoperative
Immediate
postoperative
3 m. 6 m. 12 m.
Range 38 – 81 8 – 28 8 – 28 10 – 30 10 – 30
Mean ± SD 60.47 ± 13.71 17.83 ± 5.69 18.0 ± 5.78 19.1 ± 7.29 19.1 ± 7.29
P value 0.001*

47. Cases
(n = 30)
Loss of correction
Range. 0 – 3
Mean ± SD. 1.97 ± 0.81
Loss of correction %
Range. 0 – 10%
Mean ± SD. 5.09 ±2.4
Correction degree
Range. 26 – 56
Mean ± SD. 41.37 ± 10.42
Correction rate (%)
Range. 50.8 – 83.6
Mean ± SD. 68.49 ± 9.1
Radiological outcomes.

48. There were non-statistically significant correlations
between Screw density and post-operative radiological
assessment, (p-values >0.05).
Screw density
r p-value
Loss of correction 0.164 0.387
Loss of correction %
0.035 0.856
Correction degree 0.164 0.387
Correction rate (%) -0.030 0.875

49. Screw density
r P
Operative time 0.504 0.005*
Blood loss 0.779 <0.001*
SRS change -0.259 0.176
Correction degree -0.084 0.150
190
210
230
250
270
290
310
330
0.7 0.9 1.1 1.3 1.5 1.7
Operative
time
Screw density
190
390
590
790
990
1190
1390
1590
0.7 0.9 1.1 1.3 1.5 1.7
Blood
loss
Screw density

50. Complications
Cases
(n = 30)
No. %
Postoperative anemia 2 cases 6.7
Partial neurology 2 cases 6.7
GIT complications (Vomiting) 2 cases 6.7
Wound infection 1 case 3.3

51. Discussion

52. The goals of surgical treatment
for AIS
-Arrest progression by achieving a solid fusion
-Correction of the deformity
-Improvement of the cosmetic appearance
-Improvement of the functional outcomes, physical and
psychosocial health
- Diminishing the development of low back pain, functional
impairment and cardiopulmonary compromise in adulthood

53. -In This prospective study 30 Patients diagnosed with AIS
treated by low density implants (less than 1.6 screw/level).
-They were evaluated by Whole spine Xrays AP standing ,
lateral & bending views .
-Measurement of cobb s angles in AP standing film pre
operative and postoperatively at 1,3,6,12 monthes.

54. -We found that the mean pre-operative Cobb's angle was 60.47,
the mean post-operative Cobb's was 19.1, the mean loss of
correction was 1.97 and the mean correction degree was 41.37
by using low density implants 1.23
-These correction rates compare equally well with other low
density correction studies cited in the literature.

55. -Advocates of pedicle screw constructs report that the advantages
for all pedicle screw constructs in AIS include improved coronal,
sagittal, and rotational correction, lower pseudarthrosis rates,
lower implant failures and fewer postoperative bracing
requirements.
-On the other hand studies of lower-density fixation, such as
skipped pedicle screw placement constructs, report this to be an
efficient and safe method in management of AIS

56. -All pedicle screws constructs have potential neurological,
vascular, and visceral complications which can result from
screw misplacement.
-Operative time , blood loss , risk and cost are decreased
with the use of low screw density constructs.

57. -Some surgeons were concerned regarding the potential
risks of LD constructs including implant failure, non-union
and increased revision rates.
-The lower safe limit of anchor density to maintain long-
term adequate correction remains undetermined.

58. Demographic data
Curve
types
Screws
density
Pre cobb
Post cobb
Blood loss Op. time
Immd.
Final.
(loss of correction)
Elmalky et
al., 2016 148
106 pts
14 y
All lenke
types
1,18 62,7 21,5 22.8(3.2%) 532 269.2
Ritzman et
al., 2016. 149
52pts
14,7 y
Lenke 1 1.1 54.3 19.3 22.1(8.5%) 856 309
Ozkunt et al.,
2018 147
59 pts
17,3 y
Lenke 5 1,5 42,8 15.37 15,31(0) 676.3 342.2
Tannous et
al., 2018 127
45 pts
14,9 y
All lenke
types
1,19 52,6 15,1 17,5(6.4%) 536.5 271.5
Li et al.,2018
117
63 pts
14.9 y
Lenke 1
Two groups
HD and LD
47.9 15.8 18.1 (3%) 1648 480
Yeh et al.,
2019126
172 pts
14.4 y
All lenke
types
1,3 57,4 20,8 21.7(2.7%) 721.4 302
Kilinc et al.,
2019 139
82pts
14,4 y
Lenke 1 1,1 59,1 28.2 29.9(3.1%) 496 251
Our study
30 pts
13,3 y
All lenke
types
1.23 60.47 17.83 19.1(5.09%) 837 258

59. Conclusion
-Implant density was not significantly related to coronal or axial
curve corrections.
-Low implant density with longer fusion level achieves
excellent curve correction and stability
-Operative time, blood loss, risk and cost are decreased with the
use of low screw density implants.

60. Recommendations

61. -Pre-operative planning by identification the type of curves is
the corner stone to obtain best correction.
-The use of low density implants achieves satisfactory correction
with less operative time, blood loss and complications.
-The use of monoaxial screws at periapical vertebrae and the use
of rod derotation technique are very useful to obtain good
correction by low density implants.

62. -Intraoperative neuromonitoring is essential to maintain
neurological integrity of the patients
-Intraoperative imaging at the end of surgery to assess
coronal and sagittal balance is very important.
-Further studies should include larger number of cases and
longer follow up period to detect more accurate results.

63. Thank you