magnetically controlled growing rods for early-onset...

SPINE Volume 41, Number 18, pp 1456–1462

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DEFORMITY

Magnetically controlled Growing Rods forEarly-onset Scoliosis

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1456

A Multicenter Study of 23 Cases With Minimum 2 years Follow-up

Pooria Hosseini, MD, MSc,� Jeff Pawelek, BS,� Gregory M. Mundis, MD,� Burt Yaszay, MD,y

John Ferguson, MD,z Ilkka Helenius, MD,§ Kenneth M. Cheung, MD,{ Gokhan Demirkiran, MD,jj

Ahmet Alanay, MD,�� Alpaslan Senkoylu, MD,yy Hazem Elsebaie, MD,zz and Behrooz A. Akbarnia, MD�

Curve correction was maintained for 2 years in both groups. T1-
Study Design. Retrospective study.Objective. To report 2-year clinical and radiographic results of
patients treated with magnetically controlled growing rods

(MCGR).Summary of Background Data. MCGR for early-onset sco-

liosis has been reported to provide adequate spinal growth and

curve correction by eliminating surgical lengthening procedures.

This study was designed to report the results of MCGR patients

with 2-year follow-up.Methods. A retrospective study of MCGR patients with the

following inclusion criteria: (i) major curve size �308, (ii) T1-

T12 height <22 cm, (iii) <11-years old; all at the time of index

surgery was performed. Of 54 patients enrolled, 23 had 2-year

follow-up. Both primary and conversion patients were evaluated

at baseline 6, 12, and 24 months.Results. Mean preoperative age in the primary group was

6.6� 2.6 years versus 8.3�2.2 years for the conversion group.

A total of 41 adverse events occurred in 11 patients, of which

14 events were implant related. Major coronal curve magnitude

improved from 61.38 to 34.38 from baseline to postoperation in

primary cases and from 49.48 to 43.88 in conversion cases.

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the �San Diego Spine Foundation, San Diego, CA; yRady Children’stal, San Diego, CA; zStarship Children’s Hospital, Grafton, Auckland,ealand; §Turku University Hospital, Turku, Finland; {The Duchess ofhildren’s Hospital, Pokfulam, Hong Kong; jjHacettepe University

tal, Ankara, Turkey; ��Florence Nightingale Hospital, Istanbul, Tur-nd yyAnkara Gazi University Hospital, Ankara, Turkey

wledgment date: July 9, 2015. First revision date: December 7, 2015.d revision date: January 8, 2016. Acceptance date: February 8, 2016.

evice(s)/drug(s) is/are FDA-approved or approved by correspondingal agency for this indication.

Technologies Inc. funds were received in support of this work.

nt financial activities outside the submitted work: consultancy,, payment for lectures, patents, royalties, stocks, payment for develop-of educational presentations, and travel/accommodations/meetingses.

ss correspondence and reprint requests to Gregory M. Mundis, MD,s Clinic Torrey Pines, 10666 N Torrey Pines Road, La Jolla, CA 92037;: [email protected]

10.1097/BRS.0000000000001561

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S1 height improved from 252.7 to 288.9 mm in primary cases

and was maintained for 2 years. However, conversion cases had

some decline in T1- S1 height (270.3 at baseline to 294.4 mm

post-MCGR and 290.2 mm at 2-year follow-up; mean loss of

4.2 mm (1.5%) from postoperation to 2 years, P>0.05).Conclusion. This study showed satisfactory curve correction

and growth is achieved among primary cases. T1-S1 height in

conversion cases had a slight decline in 2 years. However, this

decline was not statistically significant.Key words: dual growing rods, magnetically controlledgrowing rods, traditional growing rods.Level of Evidence: 3Spine 2016;41:1456–1462

urrently, traditional growing rods (TGR) are the

C most commonly used distraction-based techniquesin the surgical management of early-onset scoliosis

(EOS).1 These techniques that allow or encourage thegrowth of the spine and thorax, recently gained popularityand are referred to as ‘‘growth-friendly’’ distraction-basedtechniques.2

However, this technique requires repeated lengtheningideally every 6 months under general anesthesia.1,3 The needfor general anesthesia and the invasive nature of thelengthening procedures are considered the main shortfallsof this technique.4 There are also socioeconomic disadvan-tages of TGR. These include high cost of TGR,5,6 days offschool for children and time off of work for their parents,and the effect of repeat operations and anesthesia oncognitive, academic, emotional, and sociobehavioraldevelopment of the child.7 In addition, it has been shownthat children exposed to multiple operations are moreprone to development of posttraumatic stress disorder(PTSD), long-term language disabilities and cognitiondiminution.8,9

As a solution to the above-mentioned limitations of theTGR, magnetically controlled growing rods (MCGR) weredeveloped. Akbarnia et al10 implanted remote-controlled

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DEFORMITY Magnetically Controlled Growing Rods for Early-onset Scoliosis � Hosseini et al

expandable rods in six immature Yucatan pigs. The meandistraction achieved was 39 mm over a 7-week period with-out any implant related complications. Since then, MCGRhas been used in children with EOS. Till date, there are fewvaluable published articles looking at the clinical effective-ness and the safety of MCGR. In this article, we present thelargest series till date of the use of MCGR with 2-yearfollow-up.

METHODSThis study was a retrospective, multicenter review of EOSpatients who underwent either a primary or conversionspinal procedure using MCGR from November 2009 toDecember 2011. Of the 54 patients treated with MCGR, 35were implanted with generation 1 MCGR and the remain-der with generation 2. All data were from patients outsidethe United States at 15 centers. All data were compiled afterInstitutional Review Board approval of each participatingcenter. The inclusion criteria were as follows (i) major curvesize�308, (ii) thoracic spine height (TSH) (T1-T12)<22 cm,(iii) <11 years, and (iv) implanted with MCGR device.

The efficacy of MCGR was evaluated by major curvecorrection using Cobb measurement, thoracic spine height(T1-T12), and T1-S1 height. For each parameter, compari-sons were made between baseline, the immediate postoper-ative measurements, 6, 12, and 24 months. A singleindependent experienced observer for standardization pur-poses measured all radiographs. All adverse events wererecorded from the time of the index procedure throughoutthe 2-year follow-up period. To mitigate the inherent limita-tion of incomplete adverse event reporting present in anyretrospective study, the investigators were requested toinquire with each subject about the accuracy of recordeddata.

Baseline VisitDemographics, medical history, physical examination,radiographic assessment, and concomitant medicationswere recorded at baseline visit.

Operative DayThe following data were recorded on the operative day:MCGR implant used, method of fixation and spinal fixationsystem used, radiographic assessment (postindex surgery),adverse events, and neuromonitoring changes duringsurgery.

Follow-up VisitsThe following data were collected on follow-up visits:physical examination, distraction criteria and externalremote control (ERC) setting, radiographic assessment,and adverse events were recorded. Furthermore, if a reversalof distraction (retraction) was required, this was alsorecorded.

StatisticsDescriptive statistics for continuous variables includingmean, standard deviation, range, and sample size were used

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for demographics. Statistical comparisons between primaryand conversion groups were generated with a two-sidedt test. Categorical variables were summarized with percen-tages. For the safety evaluation, the incidence of all adverseevents was reported descriptively with number of events,number of subjects having one or more events, percentages,and sample size. All analyses were generated using SASVersion 9.3 software and SPSS Version 22.0 (Armonk, NY).

RESULTSA total of 115 patients from 15 different sites were screened.Fifty-four patients were enrolled in the study and the remain-der chose not to participate in the study or did not meet theinclusion criteria. Of 54 enrolled patients, three had nobaseline radiographic data available. A total of 51 patientswere included for analysis. At the time of data collection, 34patients were due for 2-year follow-up of which 23 patients(68%) completed 2-year follow-up. Twenty of 23 patients(87%) were implanted with generation one MCGR and theremainder (3/23; 13%) were generation two.

Baseline and Demographic ResultsEight of 23 patients underwent single-rod MCGR implan-tation, whereas the rest (15 patients) had dual rods. Five ofeight cases in the single rod group were primary cases andthe remaining three were conversion cases. The dual rodgroup had 10 primary and five conversion surgeries. Thebaseline demographics and characteristics are summarizedin Tables 1 and 2.

Primary and Conversion GroupsFifteen of 23 patients with 2-years follow-up were primarycases and the remaining eight belonged to conversion group.Six of eight conversion cases went through conversion toMCGR from their TGR to decrease the need for repeatedsurgery and consequently the morbidities associated withrepeated operations. One of eight conversion cases experi-enced skin problems after repeated lengthening proceduresas part of TGR management and MCGR was recom-mended. One case had progressive spinal deformity withthe TGR and to decrease the need for repeated surgeriesconversion to MCGR was recommended. All these eightcases went through conversion to MCGR after parentalrequest and surgical consultation.

EtiologyThe most common etiology in the primary group with 2-year follow-up was neuromuscular (46.7%) followed byidiopathic and congenital (both 20%), and syndromic(13.3%), whereas the most common etiology in the con-version subjects with 2-year follow-up was congenital(37.5%) followed by idiopathic and syndromic (both25%), and neuromuscular (12.5%).

Length of Follow-upThirty of 54 patients enrolled (55.5%) were primary and24 patients (44.5%) were conversion cases. At the time of

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TABLE 1. Patients’ Demographics (n¼23)

Single Rod Dual Rod Total

Age at index (yrs) (range),Mean � SD

Primary (n¼15) 2.4 – 6.5; 4.6� 1.6 3.2 – 10.7; 7.6�2.4 2.4 – 10.7; 6.6�2.6

Conversion (n¼8) 6.3 – 8.0; 7.4� 0.9 5.5 – 11.0; 8.8�2.6 5.5 – 11.0; 8.3�2.2

Sex; Male (n/N), (%);Female (n/N), (%)

Primary (n¼15) 2 / 5 (40.0 %); 3 / 5(60.0 %)

3 / 10 (30.0%); 7 / 10(70.0%)

5 / 15 (33.3%); 10 / 15(66.7 %)

Conversion (n¼8) 0 / 3 (0 %); 3 / 3 (100%)

2 / 5 (40.0 %); 3 / 5(60.0 %)

2 / 8 (25.0%); 6 / 8 (75.0%)

Height at index (cm)(range) Mean � SD

Primary (n¼8) 86-111; 95.3� 13.7 100-124; 115.2�11.3 86-124; 107.8�15.2

Conversion (n¼5) 98-100; 99.0�1.4 108-131; 116.7�12.5 98-131; 109.6�13.1

Weight at index (kg)(range) Mean � SD

Primary (n¼10) 13.0–19.9; 15.5�3.8 15.0–28.5; 22.8� 4.6 13–28.5; 20.6� 5.5

Conversion (n¼6) 13.8–14.5; 14.2�0.5 14.5–21.0; 17.8� 3.0 13.8–21.0; 16.6� 3.0

BMI at index surgery(kg/m2) (range) Mean� SD

Primary (n¼7) 11.0–17.6; 14.3�4.7 12.6–22,0; 16.1� 3.8 11.0–22.0; 15.6� 3.8

Conversion (n¼5) 14.4–14.5; 14.4�0.1 12.2–15.8; 13.9� 1.8 12.2–15.8; 14.1� 1.3

BMI indicates body mass index.


data collection 34 patients were due for 2-year follow-up ofwhich 23 were available for the visit (68%). A total of 23 of54 patients had 2-year follow-up; 15 of 23 patients wereprimary patients (65.2%) and 8 of 23 patients (34.8%) inthe conversion group.

Lengthening ProceduresThere were 180 noninvasive lengthening procedures in 23patients. The average number of distraction procedures inprimary group was 9.7�6.8 versus 4.1�2.9 in conversion(P¼0.01). The number of lengthening procedures rangedfrom two to 26 in the primary group and one to eight inconversion patients in those who had 2-year follow-up. Thevery few lengthening procedures (one and two lengthening)all happened at only one of our sites (case numbers 10 to 14 inTable 3) where investigator performed lengthening less fre-quently compared with the rest of the study cohort as per their

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TABLE 2. Patients’ Baseline Characteristics (n¼23

Single Rod

Major curve magnitude(8) (range) Mean � SD

Primary (n¼15) 55.0–101.0; 70.2

Conversion; (n¼8) 33.0–58.0; 44.7

T1–T12 height (mm)(range) Mean � SD

Primary (n¼15) 94.9–185.6; 134.6

Conversion (n¼ 8) 167.9–186.6; 176.9

Coronal balance (mm)(range) Mean � SD

Primary (n¼14) 0.8–40.4; 20.2

Conversion (n¼ 8) 7.3–18.8; 12.3

Sagittal balance (mm)(range) Mean � SD

Primary (n¼11) 3.9–77.2; 28.5

Conversion (n¼ 7) 1.0–111.8; 48.4

TSH indicates thoracic spine height.

1458 www.spinejournal.com

standard practice. In addition, this investigator had treatedseveral patients who were not residing locally; as such, thisfurther contributed to the lower frequency of lengthening.

Radiographic EvaluationIn primary cases major coronal curve improved from 61.38at baseline to 34.38 at postoperation (P¼0.002) and wasmaintained (39.18) at 2-year follow-up. In the conversiongroup it improved from 49.48 at baseline to 43.88(P¼0.075) and maintained the same (448) over 2 years.

Kyphosis changed from 48.58 at baseline to 29.38 atimmediate postoperation (P¼0.063) in primary cases andover 2 years increased to 58.58 (P¼0.138; comparedwith postoperation). This parameter changed from 39.18at baseline to 36.38 at postoperation (P¼0.116) and 33.38at 2-years follow-up (P¼0.593; compared with postopera-tion) in conversion group.

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)

Dual Rod Total

�18.0 36.0–100.0; 56.3�19.4 36.0–101.0; 61.3�19.5

�12.6 32.0–78.0; 52.2�17.7 32.0–78.0; 49.4�15.5

�38.8 123.6–192.3; 167.1�24.9 94.9–192.3; 156.2�32.9

�9.4 141.2–178.1; 167.9�15.2 141.2–186.6; 171.3�13.3

�19.7 2.5–123.6; 25,4�38.0 0.8–123.6; 23.5�31.9

�5.9 4.0–39.3; 24.0�15.1 4.0–39.3; 19.6�13.3

�30.9 8.2–94.6; 49.0�33.7 3.9–94.6; 39.7�32.6

�57.1 2.7–58.6; 36.8�24.8 1.0–111.8; 41.7�37.9

September 2016

TABLE 3. Breakdown of LengtheningProcedures Per Case

Patient ID Procedure

Total No. ofFollow UpsAvailable

Total No. ofFollow Ups

WithLengthening

1 Primary 13 8

2 Conversion 8 6

3 Primary 9 8

4 Primary 10 10

5 Primary 7 6

6 Primary 7 3

7 Conversion 4 4

8 Primary 9 8

9 Primary 13 5

10 Primary 4 2

11 Conversion 2 1

12 Conversion 6 2

13 Conversion 5 2

14 Conversion 4 2

15 Primary 5 5

16 Primary 28 26

17 Primary 23 22

18 Conversion 9 8

19 Conversion 8 8

20 Primary 14 14

21 Primary 11 11

22 Primary 13 13

23 Primary 6 5


Both T1-T12 and T1-S1 heights in primary casesimproved from 156.2 mm at baseline to 177.9 mm at post-operation (P¼0.003) and 252.7 mm to 288.9 mm(P¼0.008) respectively and both were maintained over2 years (T1-T12, 181.4 mm at 2 years; T1-S1, 292.8 mmat 2 years). However, although these two parameters inconversion cases improved from baseline to postoperation(171.3 to 185.7 mm, P¼0.345; 270.3 to 294.4 mm,P¼0.08), they declined over 2 years (185.7 mm to180.2 mm, P¼0.893 and 294.4 mm to 290.2 mm,P¼0.686) (Figure 1A–F).

Radiographic evaluation results at baseline, postopera-tive, 6, 12, and 24 months are summarized in Table 4.

Adverse EventsA total of 41 adverse events occurred in 11 patients of which14 (34%) were categorized as implant related and the restwere nonimplant related. These 14 implant related compli-cations occurred in 10 patients of whom five were primaryand five conversions (Table 5). No life-threatening implantrelated complication was reported. The implant related com-plications included pedicle screws pull out, rod fracture, painon distraction of one rod, loss of distraction, lack of lengthen-ing with intended distraction, and rods shortened instead oflengthened. Nonimplant related complications (27, 66%)


included acute nasopharyngitis, cough, raised liver functiontests, fever of unknown origin, influenza, nausea, vomiting,anemia, and unspecified contact dermatitis, which all wereaddressed successfully by the medical team.

DISCUSSIONSpinal fusion before the completion of the growth will leavea child with a shortened trunk and may adversely affectpulmonary development, which might be fatal at youngage.11 There is also the possibility of further deformitiescaused by ‘crankshaft’ phenomenon after fusion.11,12 Toovercome the complications of spinal fusion in children,Paul Harrington13 advocated distraction instrumentationwithout fusion, which was further developed by Moeet al.14 Moe et al developed periodic lengthening constructsusing single distraction rods without fusion. This was fol-lowed by the introduction of dual growing-rod technique,providing more stability, more predictable outcomes, andfewer complications.15,16 Over the last decade, manygrowth-friendly procedures have been defined.1 Skaggset al17 classified them into three main categories: ‘‘distrac-tion based’’ [e.g., TGR, vertical expandable prosthetic tita-nium rib (VEPTR), and MCGR); ‘‘tension based’’ (e.g.,staple and tether); and ‘‘growth guided’’ (e.g., Luque trolleyand Shilla). The most commonly used spine-based distrac-tion technique is the growing-rod method.1,18

TGR surgery provides an opportunity for normal spinalgrowth.15,19 However, this technique requires multipleoperations, which increases the risk of infection,4,16,20 com-plications of general anesthesia, and socioeconomic burdenon both patients/patient’s family and the healthcare sys-tem.5–8 In addition, TGR cases can experience implant-related complications such as rod fracture, anchor failure,or prominence of the implant.21 Bess et al4 reported a 24%increased risk of complications for each additional surgicalprocedure. Klemme et al22 reported 33 implant-relatedproblems in 25 patients (37%) including one death duringrod exchange. There are also reports of linear decrease insurvivorship for each operation undertaken with 49%chance of complication after seven procedures.4 To addressthe abovementioned shortfalls of TGR, the MCGR wasdeveloped.10 However, the concept of magnetic distractionis not new. Takaso et al,23 Soubeiran et al,24 Miladi,25 andWilkins and Soubeiran26 suggested that a remote magnetmight be able to provide the driving force for the GR system.MCGR has been reported to result in fewer surgical pro-cedures compared with TGR and consequently fewer gen-eral anesthesia complications. Akbarnia et al27 in a 17MCGR case-matched with TGR over 2 years reported a57 fewer surgical procedures than TGR cases. In addition, itwas shown that implant related complications were less inMCGR versus TGR (8 and 13, respectively).

The current study is the largest series of EOS patientstreated with MCGR with 2-years follow-up and the firstseries to report the clinical and radiographic results ofprimary and conversion cases analyzed independently with2-year follow-up. We have shown that the major curve


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Figure 1. A and B, Anteroposterior and lateral standing view of a 7 years old girl treated with MCGR and completed 2-year follow-up. C andD, Anteroposterior and lateral standing view of the same patient at immediate postindex MCGR surgery. E and F, Anteroposterior and lateralstanding view of the same patient after 24 months.

TABLE 4. Radiographic Results (Mean)

Baseline Postoperation 6 Months 12 Months 24 Months

Major curvemagnitude (8)

Primary 61.3 34.3 36.7 38 39.1

Conversion 49.4 43.8 37 39.5 44

Kyphosis (8) Primary 48.5 29.3 49.6 49.8 58.5

Conversion 39.1 36.3 43.7 42.7 33.3

T1–T12 height (mm) Primary 156.2 177.9 183.7 185.1 181.4

Conversion 171.3 185.7 175.1 188.6 180.2

T1–S1 height (mm) Primary 252.7 288.9 295.1 293 292.8

Conversion 270.3 294.4 275.8 289.8 290.2


1460 www.spinejournal.com September 2016

TABLE 5. Implant Related Adverse Events and Their Treatments

Case Procedure Rod Type Complication Treatment

1 Primary Dual rod Pain caused by prominent rod on rightside

Surgically resolved by trimming of rightsided rods

1 Primary Dual rod Right side pedicle screws out of pedicle Surgically revised

2 Primary Single rod Upper hook prominent Surgical revision and rod exchange

3 Primary Dual rod Rod collapse Lengthening repeated

Metallinergy is seen around the rods Bilateral rods are exchanged

3 Primary Dual rod Bilateral rods didn’t lengthen Rods are exchanged

4 Primary Dual rod Rod collapse Relengthening

Primary Dual rod Rod collapse Relengthening

5 Primary Dual rod Rod collapse Relengthening

6 Conversion Dual rod Lower part of rod broken Surgical revision but no rod exchange

7 Conversion Dual rod Protrusion of wire through skin Wire removal

8 Conversion Single rod Broken rod Rod exchange

9 Conversion Dual rod Rod foundation breakage Rod exchange

10 Conversion Single rod Broken rod Rod exchange


correction and thoracic height in primary cases were com-parable with historic TGR data and MCGR was safe andmore effective in the treatment of EOS in primary cases.Conversion cases had smaller major curve correction andminimal thoracic height improvement after 2 years. How-ever, the amount of spinal and thoracic growth appears tohave been limited in patients with previous TGR treatment.

Primary cases experienced a 44% correction (61.38 atpreoperation to 34.38 at immediate postoperation) of theirmajor curve magnitude and maintained it over 2 years,which is comparable with TGR21 versus conversion cases,in which the major curve correction was 11% (49.48 atpreoperation to 43.88 at immediate postoperation), whichwas maintained over 2 years. T1-T12 height improved from156 mm to 178 mm at immediate postoperation and over 2years. It went up to 181 mm, which can be considered asmaintaining the thoracic height in primary cases versus171 mm to 185 mm at immediate postoperation anddecrease to 180 mm in conversion cases after 2 years. Welooked at the data in detail and found not all of the patientswith 2-year follow-up have immediate postoperationmeasurements. By excluding the patients who did not havethe complete immediate postoperation measurements and2-year follow-up (8/23 cases), the average of all primaryand conversion cases at immediate postoperation improvedfrom 180.5 mm to 183.8 at 2 years. Although there is a3.8 mm improvement in thoracic height over 2 years, thisimprovement is not statistically significant (P¼0.460). Weexpected to see more obvious T1-T12 and T1-S1 heightimprovement over 2 years based on Dimeglio et al28 andAkbarnia et al15,16 findings.

To further investigate the marginal improvementrecorded in thoracic height, we reviewed all patient datawhere a decline in T1-T12 height was recorded. Seven of 23patients had a decline in their thoracic height after 2 yearscompared with their immediate postoperative measure-ments. The range of decline at 2 years compared with theimmediate postoperation was 3.57 mm to 26.74 mm. One


patient experienced three incidences of device collapse,which the treating surgeon opted to perform repeated dis-tractions at each incidence in lieu of replacing the device.This case had a thoracic height of 195.03 mm at baseline,which went down to 168.29 mm at 2 years (the maximumrange of worsening among all seven subjects). This worsen-ing certainly affected the means dramatically. Anotherpatient was involved in a road traffic accident, which causeda rod fracture. In this case, the treating surgeon decided notto exchange the rod but rather fixed the construct with rod-to-rod connectors. In remaining cases, not enough surgicalor medical information was available to understand the lossof height.

In addition, this study showed that 41 adverse eventsoccurred in 11 patients, of which 14 (34%) events werecategorized as implant related. This report is 3% less thancomplication rate of Klemme et al22 and lower than thereported adverse events of TGRs reported by Mineiroet al.21

The current study shows that MCGR is safe and effectivein primary cases. The major curve correction and thoracicheight in primary cases were comparable with historic TGRdata. Conversion cases had smaller major curve correctionand minimal thoracic height improvement after 2 years.However, the amount of spinal and thoracic growth appearsto have been limited in patients with previous TGR treat-ment. Based on this, we suggest setting realistic expectationsfor growth in conversion cases based on patient age, lengthof TGR treatment, and amount of growth prior to MCGRconversion.

The limitations of this study include the sample size andthe variation in diagnosis, age, and the retrospective natureof the study.

CONCLUSIONThe use of MCGR in treatment of EOS is safe with overallfewer complications than TGR20,21 and may be considered aviable alternative to TGR for EOS. A larger cohort study of



MCGR with longer follow-up and more homogenous groupof subjects is required to better understand the use of MCGRin particular its application to patients being converted fromTGR to MCGR.

14

Key Points

62

This study reported the clinical and radiographicresults of 23 EOS patients treated with MCGRincluding both primary and conversion cases withminimum follow-up of 2 years.

The major curve magnitude correction andthoracic height in primary cases werecomparable with historic TGR data.

MCGR is safe and effective in the treatment ofEOS in primary cases.

MCGR is safe in conversion cases, although theconversion cases in this study had smaller majorcurve correction and not statistically significantdecline in T1-T12 and T1-S1 height after 2 years.

The amount of spinal and thoracic growth appearsto have been limited in patients with previousTGR treatment. Based on this, we suggest settingrealistic expectations for growth achievement inconversion cases based on patient age, length ofTGR treatment, and amount of growth beforeMCGR conversion.

w

AcknowledgmentsThe authors are grateful to Mr. M.H. Hilali Noorden at TheRoyal National Orthopedic Hospital, UK without whoseguidance, they would not have been able to prepare thisarticle for publication in its current form.

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