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VOL. 95-B, No. 1, JANUARY 2013 75
SPINE
Early results of a remotely-operated magnetic
growth rod in early-onset scoliosis
Z. Dannawi,
F. Altaf,
N. S. Harshavardhana,
H. El Sebaie,
H. Noordeen
From Royal National
Orthopaedic
Hospital, Stanmore,
and Great Ormond
Street Hospital,
London, United
Kingdom
Z. Dannawi, FRCS(Tr & Orth),
Spinal Fellow
F. Altaf, BSc(Hons), Specialist
Registrar Trauma and
Orthopaedics
N. S. Harshavardhana,
MS(Orth), Spinal Fellow
H. Noordeen, FRCS(Tr &
Orth), Consultant Orthopaedic
Spinal Surgeon
Royal National Orthopaedic
Hospital, Brockley Hill,
Stanmore, Middlesex H A7 4LP,
UK.
H. El Sebaie, FRCS, MD,
Professor of Orthopaedic
surgery
Cairo University, School of
Medicine, Al-Saray Street, El
Manial, Cairo, PO Box 11956,
Egypt.
Correspondence should be sent
to Mr F. Altaf; e-mail:
farhaanaltaf@hotmail.com
©2013 British Editorial Society
of Bone & Joint Surgery
doi:10.1302/0301-620X.95B1.
29565 $2.00
Bone Joint J
2013;95-B:75–80.
Received 13 March 2012;
Accepted after revision 18
September 2012
Conventional growing rods are the most commonly used distraction-based devices in the
treatment of progressive early-onset scoliosis. This technique requires repeated
lengthenings with the patient anaesthetised in the operating theatre. We describe the
outcomes and complications of using a non-invasive magnetically controlled growing rod
(MCGR) in children with early-onset scoliosis. Lengthening is performed on an outpatient
basis using an external remote control with the patient awake.
Between November 2009 and March 2011, 34 children with a mean age of eight years (5 to
12) underwent treatment. The mean length of follow-up was 15 months (12 to 18). In total,
22 children were treated with dual rod constructs and 12 with a single rod. The mean
number of distractions per patient was 4.8 (3 to 6). The mean pre-operative Cobb angle was
69° (46° to 108°); this was corrected to a mean 47° (28° to 91°) post-operatively. The mean
Cobb angle at final review was 41° (27° to 86°). The mean pre-operative distance from T1 to
S1 was 304 mm (243 to 380) and increased to 335 mm (253 to 400) in the immediate post-
operative period. At final review the mean distance from T1 to S1 had increased to 348 mm
(260 to 420).
Two patients developed a superficial wound infection and a further two patients in the
single rod group developed a loss of distraction. In the dual rod group, one patient had pull-
out of a hook and one developed prominent metalwork. Two patients had a rod breakage;
one patient in the single rod group and one patient in the dual rod group. Our early results
show that the MCGR is safe and effective in the treatment of progressive early-onset
scoliosis with the avoidance of repeated surgical lengthenings.
Cite this article: Bone Joint J 2013;95-B:75–80.
Early-onset scoliosis (EOS) has been defined as
significant spinal deformity beginning before
the age of five years.1 Its most common types
are infantile idiopathic, congenital and neuro-
muscular.2 Left untreated, it can rapidly pro-
gress causing cosmetic disfigurement and
pulmonary insufficiency.3 The goals of treat-
ment are to control the deformity, allow
growth of the spine and chest wall and to
improve pulmonary function. Casting or brac-
ing are commonly used for early intervention,
but bracing is not effective in controlling the
curves of neuromuscular or congenital scolio-
sis.4-7 When the deformity is progressive and
severe, surgical treatment is often indicated.
Spinal fusion can be performed with or with-
out instrumentation. If undertaken before
growth is complete, it results in a short trunk
with possible underdevelopment of the lungs
and subsequent pulmonary complications.8-10
Procedures that allow or encourage growth
of the spine and chest have recently gained
popularity. These are variously referred to as
‘growth-sparing’ or ‘growth-friendly’.11 The
most commonly used devices are single and
dual growing-rod implants. The traditional
growing rod is inserted across the spinal cur-
vature under general anaesthesia and ideally
distracted every six months or sooner.12 This
requires re-opening the surgical incision to
distract the rod to mimic and maintain nor-
mal spinal growth. The disadvantages of
using the traditional growing rod include the
need for general anaesthesia and the invasive-
ness of repeated distractions. These implants
have been associated with high rates of com-
plication including wound infection, rod
breakage, auto-fusion, anchor failure or
prominence of the implant.13,14
There are also socioeconomic disadvan-
tages to the use of traditional growing rods
and their repeated surgeries, including the
indirect costs to child and parents as a result
of the time missed from school and absence
from work.15 Children exposed to multiple
operations are also more likely to experience
76 Z. DANNAWI, F. ALTAF, N. S. HARSHAVARDHANA, H. EL SEBAIE, H. NOORDEEN
THE BONE & JOINT JOURNAL
severe symptoms of post-traumatic stress disorder and
depression than those who experience a single event.16
An earlier animal study by Takaso et al17 suggested that the
use of a remotely-controlled extending rod instrumentation
system could decrease the number of procedures required.
That study involved five beagles with induced scoliosis. The
mean initial Cobb angle of 25° was corrected to a mean of 3°
after four distractions over a period of 12 weeks. No compli-
cations were recorded.17 Akbarnia et al18 implanted remotely
expandable rods in six immature Yucatan pigs. The mean dis-
traction achieved was 39 mm over a seven-week period with-
out any implant-related complications.
In the only study published so far on the use of a magnet-
ically controlled growing rod (MCGR) it was shown possi-
ble in five children to correct a spinal curvature and
encourage normal spinal growth.19
We present the largest series to date of the use of MCGR
in humans.
Patients and Methods
Between November 2009 and March 2011, 34 children
with EOS were treated using magnetically-controlled grow-
ing rods with prospective collection of data. The inclusion
criteria were EOS from any cause, failed non-operative
treatment with bracing or observation and progression of
the curvature of > 10° over a six-month period with a Cobb
angle20 > 40°. Infected patients were excluded.
Two patients had previously undergone conventional
treatment with growing rods before having an MCGR
implant. The parents of the two children who underwent
conversion from the conventional growing rod to the
MCGR requested this new technique on the grounds that
their children had significant remaining growth potential
and felt that their children would benefit from non-invasive
lengthening, having learnt of the treatment from other
patients. One of these children, aged six years, had an
infantile scoliosis with a left-sided thoracic curve and a
Cobb angle of 75° at the time of conversion. A dual MCGR
construct was implanted between T3 and L2. The other had
a diagnosis of neuromuscular scoliosis and had a left lum-
bar curve with a Cobb angle of 80° for which a dual MCGR
was implanted between T2 and the pelvis. The mean age of
the children included in the series was eight years (5 to 12).
There were 13 boys and 21 girls. The minimum length of
follow-up was 12 months (mean 15 months (12 to 18)). The
diagnosis was idiopathic scoliosis in 14 children, neuromus-
cular scoliosis in 11, congenital scoliosis in two, neurofi-
bromatosis in three, and there were four syndromic patients.
Skeletal maturity was assessed using Risser staging21 and by
evaluating the triradiate cartilage.
In all a single-rod construct was used for 12 patients and
22 required a dual-rod construct. All operations were per-
formed by the senior author (HN). Each patient had at least
three magnetically controlled lengthenings.
The decision to implant single or dual rods was depend-
ent on the size of the patient and the preference of the sur-
geon. Single rods were implanted into slim patients to avoid
the complications of symptomatic prominent metalwork.
As our experience with the MCGR technique increased, we
felt that the dual-rod construct provided better correction
and greater stability and was therefore implanted into older
patients with a higher body mass index.
The MCGR implant is made of titanium and includes a
telescopic actuator portion that holds a small internal mag-
net (Fig. 1). Rotation of the magnet, by the use of remote
control, causes the rod to lengthen or shorten.
Under general anaesthesia, with the patient prone, two
separate posterior proximal and distal skin incisions
were made over the foundation levels. In the revision
cases we used the whole length of the previous scar to
remove the previous metalwork and to implant the
MCGR. A subperiosteal dissection was performed and
the proximal and distal anchor sites prepared. A combi-
nation of hooks and pedicle screws were used as anchors.
The magnetic rods (MAGEC Ellipse technology, Irvine,
California) were contoured, tested and inserted submus-
cularly either as a single-rod (Fig. 2) or a dual-rod con-
struct (Fig. 3). The single rod was always placed on the
concavity of the curve. The levels of instrumentation did
not vary between the single and dual-rod technique.
When dual rods were used a connector was inserted
between the two rods. Local bone graft was used at the
exposed foundation levels to achieve a limited fusion and
stability at the anchor sites.
Fig. 1
Photograph of a magnetically controlled growing rod with a telescopic actuator portion that holds a
small internal magnet.
EARLY RESULTS OF A REMOTELY-OPERATED MAGNETIC GROWTH ROD IN EARLY-ONSET SCOLIOSIS 77
VOL. 95-B, No. 1, JANUARY 2013
The lengthenings were performed by an electrically pow-
ered remote controller. This contained two permanent mag-
nets that could be rotated using gears. The remote control
was placed externally over the patient’s spine at the level of
the actuator portion of the rod, which contained a magnet.
The magnetic field from the latter was identified using an
external magnet that was attracted to the rod magnet.
When activated, the external remote control causes the
magnet of the implanted device to rotate. The spinal dis-
tractions were performed on an outpatient basis without
the need for anaesthesia or analgesia. All distractions were
performed by the senior author (HN). The predicted
lengthening was displayed on the external distraction
device, which could also be used to retract the rod if the
patient was uncomfortable or in pain. Pre- and post-dis-
traction radiographs were taken for all patients to confirm
that the rods had been lengthened.
With the dual-rod construct we inserted a standard rod
on one side of the spine and an offset rod on the other side.
The internal lengthening mechanism of the offset rod was
located at the opposite end of the thickened portion of the
rod from the standard rod in order to prevent interaction
between the magnetic components of the rods during indi-
vidual distractions. The levels of implantation and fixation
were determined by the type of curve and the underlying
pathology with the proximal fixation being usually at the
level of T2-T4 and the distal instrumentation at the neutral
vertebra intersected by the central sacral vertical line
(CSVL). In neuromuscular cases, distal instrumentation
was continued to the pelvis using iliac bolt screws.
The lengthening was performed over a mean of 87 days
(56 to 132). Each patient was given an appointment at
three-month intervals for distraction. Two patients who had
an initial loss of distraction were seen at 56 and 61 days,
respectively, to address this. These patients had a retainer
magnet (externally applied to the skin at the site of the actu-
ator) to maintain the distraction and prevent its collapse.
The rod design was subsequently changed by the manufac-
turer to avoid this complication. One patient was length-
ened at 132 days as he failed to attend his outpatient
appointment at three months because of intercurrent illness.
Previous work has shown that patients lengthened at
intervals of less than six months have a higher annual
growth rate (1.8 cm vs 1.0 cm) than those lengthened at an
interval between nine and 20 months.22 Using this informa-
tion we chose a distraction interval of three months to opti-
mise the growth potential of the spine.
We calculated the length of predicted distraction based
on the growth chart by DiMeglio and Bonnel23 for healthy
children. In general, the spine was distracted by approxi-
mately 1.5 mm per month with the aim to do this at a faster
rate than the predicted spinal growth to allow for better
curve correction. Based on our distraction protocol of three
months, we aimed to achieve a distraction of approxi-
mately 4.5 mm per visit.
One spinal fellow (ZD) and one orthopaedic registrar
(FA) measured the Cobb angles and T1-S1 length pre-
operatively, post-operatively, and before and after each dis-
traction. Any discrepancy was discussed and a final meas-
urement agreed by consensus. The authors measured the
distraction as it pertained to the telescopic portion on radi-
ographs. The distance between T1 and S1 was used as an
Fig. 2a
Lateral (a) and posteroanterior (b) radiographs in a ten-year-
old girl at eight months after implantation of the single mag-
netic growth rod.
Fig. 2b
Fig. 3a
Lateral (a) and posteroanterior (b) radiographs in a seven-year-old boy
at six months after implantation of the dual magnetic growth rod in a
case of neuromuscular scoliosis.
Fig. 3b
78 Z. DANNAWI, F. ALTAF, N. S. HARSHAVARDHANA, H. EL SEBAIE, H. NOORDEEN
THE BONE & JOINT JOURNAL
indication of growth and truncal height, and measured as
the vertical distance between the two parallel lines that
passed through the centres of the upper end-plates of T1
and S1. Complications that were intra-operative or
implant-related and general complications, such as wound
infections, were recorded.
Statistical analysis. Comparison of the pre-operative and
post-operative Cobb angles and the distance between T1
and S1, was evaluated using a paired-samples t-test,
unpaired t-test, and analysis of variance (ANOVA) using
SPSS v20 software (IBM, Armonk, New York). An inde-
pendent samples t-test was used to compare patients who
underwent treatment with single magnetic growth rod with
those with dual magnetic growth rods. A p-value < 0.05
was considered statistically significant.
Results
There were a mean of 4.8 distractions (3 to 6) per patient.
The mean time to the first distraction was 66 days (22 to
112). The mean time between distractions was 87 days (56
to 132). The minimum follow-up was 12 months from the
time of initial surgery, with a mean of 15 months (12 to 18).
There was improvement in the mean Cobb angle and T1-
S1 lengthening, and to a lesser extent the global thoracic
kyphosis (Table I, Fig. 4).
In the single-rod group there was a significant differ-
ence between the mean pre-operative, immediate post-
operative and final Cobb angles (ANOVA, p < 0.001). In
addition, there was a significant reduction in the mean
Cobb angle between the pre-operative and immediate
post-operative measurements (paired t-test, p < 0.001)
Ta b l e I. Mean Cobb angles, global thoracic kyphosis angles and T1-S1 lengths pre- and post-operatively and at final follow-up, and by single- and
double-rod constructs
Pre-operative Post-operative
Mean
improvement
p-value
(pre-op vs post-op)*Final follow-up
p-value
(ANOVA)†
Mean Cobb angle (°) (range) 69 (46 to 108) 47 (28 to 91) 22 < 0.001 41 (27 to 86) < 0.001
Single-rod 67 (46 to 108) 48 (33 to 91) 19 < 0.001 44 (32 to 86) < 0.001
Double-rod 70 (56 to 95) 46 (28 to 60) 24 < 0.001 40 (27 to 56) < 0.001
p-value (single- vs double-rod)‡0.58 0.47 0.04 0.22
Mean global thoracic kyphosis (°)
(range)
33 (26 to 42) 29 (27 to 41) 4 0.13 32 (28 to 42) -
Mean T1-S1 length (mm) (range) 304 (243 to 380) 335 (253 to 400) 31 < 0.001 348 (260 to 420) < 0.001
Single-rod 307 (290 to 380) 335 (310 to 400) 28 < 0.001 347 (317 to 420) < 0.001
Double-rod 302 (243 to 352) 335 (253 to 386) 33 < 0.001 349 (260 to 401) < 0.001
p-value (single- vs double-rod)‡0.62 0.89 0.94
* paired t-test
† analysis of variance
‡ unpaired t-test
Fig. 4a
Postero-anterior radiographs showing an example of improvement in Cobb angle and lengthening
after single-rod implantation, a) pre-operatively (Cobb angle 62°, T1-S1 length 380 mm),
b) immediately post-operatively (Cobb angle 47°, T1-S1 length 400 mm), and c) at 12 months post-
operatively (Cobb angle 36°, T1-S1 length 420 mm).
Fig. 4b Fig. 4c
EARLY RESULTS OF A REMOTELY-OPERATED MAGNETIC GROWTH ROD IN EARLY-ONSET SCOLIOSIS 79
VOL. 95-B, No. 1, JANUARY 2013
(Table I). There was a significant difference between the
mean pre-operative, immediate post-operative and final
distance between T1 and S1 (ANOVA, p < 0.001), and a
significant increase in the mean T1-S1 distance between
the pre-operative and immediate post-operative measure-
ments (paired t-test, p < 0.001) (Table I).
In the dual rod group there was a significant difference
between the mean pre-operative, immediate post-opera-
tive and final Cobb angles (ANOVA, p < 0.001) and sig-
nificant reduction in the mean Cobb angle between the
pre-operative and immediate post-operative measure-
ments (paired t-test, p < 0.001) (Table I). There was a sig-
nificant difference between the mean pre-operative,
immediate post-operative and final distance between T1
and S1 (ANOVA, p < 0.001). Additionally, there was a sig-
nificant increase in the mean distance between T1 and S1
between the pre-operative and immediate post-operative
measurements (paired t-test, p < 0.001 (Table I).
The difference in the mean pre-operative Cobb angles
between the single and dual rod groups was not significant
(unpaired t-test, p = 0.58). The mean improvement in Cobb
angle (immediate post-operative to pre-operative Cobb
angle) was significantly different between the single and the
dual rod groups (unpaired t-test, p = 0.04).
One patient in each group developed a superficial wound
infection that was successfully treated with oral antibiotics.
There were also two patients in the single-rod group who
had a loss of distraction that was rectified by subsequent
lengthening. In each group there was one rod breakage that
required revision of the construct. The breakage in the
single-rod construct occurred in a patient who had previ-
ously undergone conventional growing rod treatment. The
breakage was noticed before her second lengthening. Hook
pull-out occurred in one patient in the dual rod group.
Another patient had prominent metalwork that required
trimming of the rod.
No patient encountered more than one complication.
Post-operative fusion did not occur in any patient and no
patient developed a neurological deficit.
Discussion
Treatment of children with an early onset scoliosis should
focus not only on the spinal deformity but also on the
growth of the chest wall and development of the lungs. If
surgical correction is required and fusion is performed
before the completion of growth, the child is left with a
short trunk and a disproportionate body habitus. This may
adversely affect lung development and result in respiratory
insufficiency in the very young.24,25 There is also a possibil-
ity of developing further deformity from the ‘crankshaft’
phenomenon.24,25
In order to allow continuous spinal growth and over-
come the complications arising from spinal fusion,
Harrington26 advocated distraction instrumentation with-
out fusion in young children. Moe et al27 subsequently
developed the technique of periodic lengthening of the
construct, using single distraction rods without fusion, to
correct the deformity and maintain spinal growth. Over the
last decade many growth-sparing procedures have gained
popularity. Sankar et al11 classified the various growth-
friendly procedures into three types: 1) distraction-based
devices; 2) tension-based devices; and 3) growth-guided
procedures. The most commonly used spine-based distrac-
tion technique is the ‘growing rods’ method. This technique
follows the concept of periodic distraction to catch up and
keep pace with the demands of growth. Single and dual
growing rod constructs have been used in an attempt to
control spinal deformity and allow continued spinal
growth. The proponents of the dual rod constructs report
better correction of deformity, increased stability and a
greater proportion of expected spinal growth than that
achieved with single rods.28
Conventional growing rods allow spinal growth to con-
tinue and prevent curve progression but need multiple
interventions that increase the risk of infection,14,29,30 com-
plications of general anaesthesia, and stress to both parents
and children.
In our study, only two of 34 patients developed a wound
infection, which is better than a conventional growth rod
series.14,29,30
Implant-related complications such as rod fracture, anchor
failure or prominence of the implant, were the most frequent
complications in one series of growth rods.31 Rod fractures
are inevitable with non-fusion techniques. Yang et al32 identi-
fied several risk factors that increased the probability of rod
breakage in a multicentre analysis of 322 patients with grow-
ing rods. These were single-rod constructs, rods of smaller
diameter, stainless steel rods and ambulatory patients. By
contrast, Thompson et al28 showed a higher rate of rod
fracture in the dual-rod group despite the perceived
greater stability provided by the construct. Klemme et al33
reported 33 implant-related problems in 25 patients
(37%) including one death during rod exchange through a
subfascial tunnel when the rod was deflected and trans-
gressed the retroperitoneal space and thorax. Bess et al13
showed a linear decrease in survivorship for each opera-
tion undertaken with 49% chance of having a complica-
tion after seven procedures.
In our preliminary series, there were two rod breakages
in 34 patients, a lower incidence than that reported in a
conventional growing-rod series,31 although our follow-up
was shorter. The two cases of rod breakage occurred in
patients with a residual coronal imbalance of > 2 cm at the
time of the original surgery. It is likely this resulted in
increased stress and bending moments on the rod and sub-
sequent rod breakage. The loss of distraction that occurred
in our first cases was again related to excessive stress caused
by the bending moment on the rod, leading to slippage of
the magnetic mechanism. We eliminated the slippage by the
addition of a retainer magnet and the rod design was sub-
sequently changed by the manufacturer, which has elimi-
nated this problem.
80 Z. DANNAWI, F. ALTAF, N. S. HARSHAVARDHANA, H. EL SEBAIE, H. NOORDEEN
THE BONE & JOINT JOURNAL
Non-invasive extendible endoprostheses have been used
successfully to reconstruct the lower limb after resection of
malignant bone tumours in children.34 Miladi and
Dubousset35 reported the use of a magnetically expandable
growing rod that can be used for distraction between ribs,
vertebra and pelvis. The idea of non-invasive multiple
lengthening in the treatment of scoliosis without the need
for open surgery under anaesthesia is appealing given the
direct relationship between repeated operations and a high
rate of complication. There is no evidence that the electro-
magnetic field causes any persistent or major side effect
with repeated distraction, especially in a local field.36
Limitations of this study include the variation in the
diagnosis, curve types, gender, post-operative distraction
period and the number of distractions, as well as short
duration of follow-up.
Our preliminary results show that the use of MCGR in
treatment of progressive EOS is safe and effective in cor-
recting deformity while allowing continuous spinal growth.
Overall, we found fewer complications than series that had
reviewed conventional growing rods.14,31 Lengthening of
the MCGR can be carried out as an outpatient procedure
and results in comparable spinal growth to the conven-
tional growing rod procedure. A larger cohort of patients
with a longer follow-up is required to determine the long-
term outcomes of this technique.
No benefits in any form have been received or will be received from a commer-
cial party related directly or indirectly to the subject of this article.
References
1. Rinella A, Lenke L, Whitaker C, et al. Perioperative halo-gravity traction in the
treatment of severe scoliosis and kyphosis. Spine (Phila Pa 1976) 2005;30:475–482.
2. Campbell RM Jr, Smith MD. Thoracic insufficiency syndrome and exotic scoliosis.
J Bone Joint Surg [Am] 2007;89-A(Suppl):108–122.
3. Campbell RM Jr, Smith MD, Mayes TC, et al. The characteristics of thoracic
insufficiency syndrome associated with fused ribs and congenital scoliosis. J Bone
Joint Surg [Am] 2003;85-A:399–408.
4. McMaster MJ, Macnicol MF. The manag ement of progressive infantile idiopathic
scoliosis. J Bone Joint Surg [Br] 1979;61-B:36–42.
5. Mehta MH. Growth as a corrective force in the early treatment of progressive infan-
tile scoliosis. J Bone Joint Surg [Br] 2005;87-B:1237–1247.
6. Robinson CM, McMaster MJ. Juvenile idiopathic scoliosis: curve patterns and
prognosis in one hundred and nine patients. J Bone Joint Surg [Am] 1996;78-A:1140–
1148.
7. Sponseller PD, Thompson GH, Akbarnia BA, et al. Growing rods for infantile
scoliosis in Marfan syndrome. Spine (Phila Pa 1976) 2009;34:1711–1715.
8. Emans JB, Kassab F, Caubet JF. Earlier and more extensive thoracic fusion is asso-
ciated with diminished pulmonar y function: outcomes after spinal fusion of 4 or more
thoracic segments before age 5. Paper presented at Scoliosis Research Society 39th
Annual Meeting, Argentina, 2004.
9. Goldberg CJ, Moore DP, Fogarty EE, Dowling FE. Long term results from in situ
fusion for congenital vertebral deformity. Spine (Phila Pa 1976) 2002;27:619–628.
10. Karol LA, Johnston C, Mladenov K, et al. Pulmonary function following early tho-
racic fusion in non-neuromuscular scoliosis. J Bone Joint Surg [Am] 2008;90-A:1272–
1281.
11. Sankar WN, Acevedo DC, Skaggs DL. Comparison of complications among grow-
ing spinal implants. Spine (Phila Pa 1976) 2010;35:2091–2096.
12. Yilmaz G, Huri G, Demirkran G, et al. The effect of posterior distraction on verte-
bral growth in immature pigs: an experimental simulation of growing rod technique.
Spine (Phila Pa 1976) 2010;35:730–733.
13. Bess S, Akbarnia BA, Thompson GH, et al. Complications of growing-rod treat-
ment for early-onset scoliosis: analysis on one hundred and forty patients. J Bone
Joint Surg [Am] 2010;92-A:2533–2543.
14. Farooq N, Garrido E, Altaf F, et al. Minimizing complications with single submus-
cular growing rods: a review of technique and results on 88 patients with minimum
two-year follow-up. Spine (Phila Pa 1976) 2010;25:2252–2258.
15. Caldas JC, Pais-Ribeiro JL, Carneiro SR. General anaesthesia, surgery and hos-
pitalization in children and their effects upon cognitive, academic, emotional and
sociobehavioral development: a review. Pediatr Anaesth 2004;14:910–915.
16. Suliman S, Mkabile SG, Fincham DS, et al. Cumulative effect of multiple trauma
on symptoms of posttraumatic stress disorder, anxiety, and depression in adoles-
cents. Compr Psychiatry 2009;50:121–127.
17. Takaso M, Moriya H, Kitahara H, et al. New remote-controlled growing-rod spinal
instrumentation possibly applicable for scoliosis in young children. J Orthop Sci
1998;3:336–340.
18. Akbarnia BA, Mundis GM, Salari P, Yaszay B, Pawelek JB. Inno vation in grow-
ing rod technique: a study of safety and efficacy of a magnetically controlled growing
rod in a porcine model. Spine (Phila Pa 1976) 2012;37:1109–1114.
19. Cheung K, Cheung JP, Samartzis D, et al. Magnetically controlled growing rods
for severe spinal curvature in young children: a prospective case series. Lancet
2012;379:1967–1974.
20. Cobb JR. Outline for the study of scoliosis. Instr Course Lect 1948;5:261–275.
21. Risser JC. The iliac apophysis: an invaluable sign in the management of scoliosis.
Clin Orthop Relat Res 1958;11:111–120.
22. Akbarnia BA, Breakwell LM, Marks DS, et al. Dual growing rod technique fol-
lowed for three to eleven years until final fusion: the effect of frequency of lengthen-
ing. Spine (Phila Pa 1976) 2008;33:984–990.
23. DiMeglio A, Bonnel F. Le rachis en croissance. Paris: Springer Verlag, 1990.
24. Karol LA, Johnston C, Mladenov K, et al. Pulmonary function, radiographic meas-
ures, and quality of life in children with congenital scoliosis: an evaluation of patient
outcomes after early spinal fusion. Spine (Phila Pa 1976) 2008;33:1242–1249.
25. Harrington PR. Treatment of scoliosis: correction and internal fixation by spine
instrumentation. J Bone Joint Surg [Am] 1962;44-A:591–634.
26. Harrington PR. Scoliosis in the growing spine. Pediatr Clin North Am 1963;10:225–
245.
27. Moe JH, Kharrat K, Winter RB, Cummine JL. Harrington instrumentation without
fusion plus external orthotic support for the treatment of difficult curvature problems
in young children. Clin Orthop Relat Res 1984;185:35–45.
28. Thompson GH, Akbarnia BA, Kostial P, et al. Comparison of single and dual
growing rod techniques followed through definitive surgery: a preliminary study.
Spine (Phila Pa 1976) 2005;30:2039–2044.
29. Akbarnia BA, Marks DS, Boachie-Adjei O, Thompson AG, Asher MA. Dual
growing rod technique for th e treatment of progressive early-onset scoliosis: a m ulti-
center study. Spine (Phila Pa 1976) 2005;30(Suppl):S46–S57.
30. Bess S, Akbarnia BA, Thompson GH, et al. Complications of growing-rod treat-
ment for early-onset scoliosis: analysis on one hundred and forty patients. J Bone
Joint Surg [Am] 2010;92-A:2533–2543.
31. Mineiro J, Weinstein SL. Subcutaneous rodding for progressive spinal curvatures:
early results. J Pediatr Orthop 2002;22:290–295.
32. Yang JS, Sponseller PD, Thompson GH, et al. Growing rod fractures: risk factors
and opportunities for prevention. Spine (Phila Pa 1976) 2011;36:1639–1644.
33. Klemme WR, Denis F, Winter RB, Lonstei n JW, Koop SE. Spinal instrumentation
without fusion for progressive scoliosis in young children. J Pediatr Orthop
1997;17:734–742.
34. Gupta A, Meswania J, Pollock R, et al. Non-invasive distal femoral expandable
endoprosthesis for limb-salvage surgery in pediatric tumours. J Bone Joint Surg [Br]
2006;88-B:649–644.
35. Miladi L, Dubousset J. Magnetic powered extensible rod for thorax or spine. In:
Akbarnia BA, Yazici M, Thompson GH, eds. The growing spine: management of spinal
disorders in young children. Berlin, Heidelberg: Springer-Verlag 2010:585–593.
36. Yamaguchi-Sekino S, Sekino M, Ueno SH. Biological effects of electromagnetic
fields and recently updated safety guidelines for strong static magnetic fields. Magn
Reson Med Sci 2011;10:1–10.
