Using Ultrasound as an Alternative to Radiography in Measuring Magnetically Controlled Growing Rods (MCGR) in Tibia and Femur Lengthening Patients
Phase: NA
Conditions: Limb Length Discrepancy
Sponsor: Nemours Children's Clinic

Title of the Study: Using Ultrasound as an Alternative to Radiography in Measuring 
Magnetically Controlled Growing Rods (MCGR) in Tibia and Femur Lengthening 
Patients 
 
 
IRB# 2169786 
 
9/8/2025 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
 
2. Objective (purpose) / Hypothesis: 
   
a. Objective: The purpose of this study is to evaluate the efficacy of ultrasound 
imaging as an alternative to radiographs in assessing the bone lengthening 
measurements in a pediatric cohort. 
    
b. Hypothesis: We hypothesize that ultrasound will obtain the same 
measurements as radiographs during tibia and femur lengthening procedures in 
pediatric patients. 
 
3. Background / Literature Review: 
Limb lengthening with expanding intramedullary rods has become the standard of care 
for limb lengthening procedures [1]. The procedure entails performing an osteotomy of 
the short bone and placing a mechanical expanding intramedullary nail (Fig. 1).  
 
 
 
 
 
 
The bone is then allowed to rest for 5-7 days to develop a callus, The callus is then 
stretched by using an external device to active the intramedullary rod. The lengthening 
is performed at home by the family at a rate of 0.75 to 1 cm per day. Patients 
undergoing lengthening have frequent follow ups in the orthopedic clinic for x-rays and 
Figure 1: Femur and Tibia Lengthening intramedullary nail.  

clinic exam to evaluate for complications such as joint contracture, hardware failure, or 
early consolidation. The average cumulative radiation dose from a lengthening 
procedure is estimated at 3.1 mSv or 1.1 mSv/cm [2]. Radiation exposure is cumulative 
and can cause cancers and diseases. Ultrasound is a non-invasive imaging modality 
that has been used in multiple aspects of medicine to measure the musculoskeletal 
system and help diagnosis disorders. Ultrasound has been used recently to assess 
magnetically controlled growth rod (MCGR) length in scoliosis treatment reveals 
promising results [3]. A prospective investigation by Yoon et al. highlights ultrasound as 
a reliable and non-invasive alternative to radiography, showing high agreement in 
MCGR length measurements [4]. However, studies by Cobanoglu et al. and Stokes et 
al. point out potential limitations, such as lower measurement values and 
underestimation of length compared to traditional X-rays, and the inability to assess 
certain complications or fusion blocks [5, 6]. Overall, these findings underscore the 
potential of ultrasound in reducing radiation exposure during pediatric scoliosis 
treatment. The aim of our study is to explore the role of ultrasound to measure tibia and 
femur lengthening procedures and compare the accuracy to standard radiographs.  
 
4. Methods: 
a. Study design: Prospective, Pilot Study 
b. Patient cohort: All patients who were treated at Nemours Children’s Hospital 
Florida for leg length discrepancy treated with a magnetically controlled growth rod in 
the tibia or femur (CPT 27715 Tibia lengthening and CPT 27466 femoral lengthening) 
c. Sample size  
 
5 tibias 
 
5 femurs 
  
About 10 pediatric patients  
d. Inclusion and Exclusion Criteria:  
Inclusion: 
• All patients 8 to 21 years old  
• Patients undergoing tibia or femur lengthening with an intramedullary 
mechanical rod.  
 
Exclusion: 
• Patients who underwent lengthening procedure with any other device such as 
external fixator.  
• Patients under 8 years old and over 21 years of age 
e. Data to be Collected:  
 
 
i. 
Primary outcome variable: 
• Tibia and femur lengthening measured via ultrasound  
• Tibia and femur lengthening measured via x-ray 
 
 
ii.Secondary variables:  
• Discomfort during imaging 
• Cost 
• Number of x-rays 
• Dose of Radiation 0.001 per x-ray 
• Patient Age 

• Gender 
• Laterality (Left vs Right limb) 
• Limb segment being measured. 
• Complications 
• Rate of lengthening  
• Final lengthening goal  
• Length achieved.  
f. Procedures: 
1. Patient will be recruited by Dr Malone in the orthopedic clinic 
Figure 2: Femur areas of measuring on x-rays and ultrasound during lengthening 

2. Consent will be obtained by Dr Malone 
3. All patients will follow up weekly for clinical exam and imaging with 
no change to current workflow or standard of care.   
4. All patients will obtain standard AP and Lateral x-rays  
a. Measurements will be obtained in three locations through the 
picture archiving and communication system (PACS) (Fig. 2 
and 3 for femur and tibia, respectively) 
A. The end of the proximal bone segment to the proximal 
end of the distal bone segment  
B. The distal end of the female aspect of the rod to the distal 
end of the male aspect of the rod 
C. The distal end of the female aspect of the rod to the 
proximal screw in the male aspect of the rod 
Figure 3: Tibia areas of measuring on x-rays and ultrasound during lengthening 

5. All enrolled patients will have ultrasound imaging and 
measurements will be obtained in three locations and measured in 
millimeters (Fig. 2 and 3 for femur and tibia, respectively) 
A. The end of the proximal bone segment to the proximal 
end of the distal bone segment  
B. The distal end of the female aspect of the rod to the distal 
end of the male aspect of the rod 
C. The distal end of the female aspect of the rod to the 
proximal screw in the male aspect of the rod 
 
6. Ultrasound measurements will be performed using a Point of Care 
Ultrasound (PoCUS), Butterfly iQ+  
7. All PoCUS measurements will be performed by an ultrasound 
trained physician 
a. Dr. Cassidy Foley 
b. Dr. Amit Patel 
c. Dr Julia Fink 
d. Kaitlin Maher PA-C 
8. Enrolled patients’ information will be placed and stored on a 
password protected excel file and given a patient number.  
9. All measurements will be stored on a password protected excel file 
with no patient identifiers except a patient number.  
10. Patient demographic will be obtained from the electronic medical 
record (EMR) 
11.  Dose of Radiation will be estimated at 0.001 microseverts per x-ray 
[7]. 
12. Cost of x-rays will be estimated from the Nemours Children’s 
Hospital, Florida posted chargemaster.  
a. The charge will not include the radiology read.  
b. The charge for a femur x-ray is $276.  
c. The charge for a tibia x-ray is $462.  
d. No charge will be made for PoCUS. 
13. Patients will be asked about pain from the PoCUS 
a. Pain score will be obtained using Wong Baker FACES Pain 
Rating Scale (Fig. 4).  
 
 
 
 
 
 
 
 
 
 
 
Figure 4: Wong-Baker Faces Pain Rating Scale 

 
g. Statistical Analyses:  
 
Means will be compared using T-test. Pearson correlation coefficient and 
the Bland-Altman method will be used to compare the measurements between 
ultrasound to x-ray measurements.  
 
 5. 
References: 
 
1. 
Laubscher, M., et al., Outcomes following femoral lengthening: An initial 
comparison of the Precice intramedullary lengthening nail and the LRS external 
fixator monorail system. Bone Joint J, 2016. 98-b(10): p. 1382-1388. 
2. 
Schiedel, F.M., T.C. Buller, and R. Rödl, Estimation of patient dose and 
associated radiogenic risks from limb lengthening. Clin Orthop Relat Res, 2009. 
467(4): p. 1023-7. 
3. 
Cheung, J.P., et al., Clinical utility of ultrasound to prospectively monitor 
distraction of magnetically controlled growing rods. Spine J, 2016. 16(2): p. 204-
9. 
4. 
Yoon, W.W., et al., The use of ultrasound in comparison to radiography in 
magnetically controlled growth rod lengthening measurement: a prospective 
study. Eur Spine J, 2015. 24(7): p. 1422-6. 
5. 
Çobanoğlu, M., et al., Comparison of Intended Lengthening of Magnetically 
Controlled Growing Rods: Ultrasound Versus X-Ray. Journal of Pediatric 
Orthopaedics, 2017. 39: p. e141–e146. 
6. 
Stokes, O.M., et al., Reducing radiation exposure in early-onset scoliosis surgery 
patients: novel use of ultrasonography to measure lengthening in magnetically-
controlled growing rods. Spine J, 2014. 14(10): p. 2397-404. 
7. 
Mettler, F.A., et al., Effective Doses in Radiology and Diagnostic Nuclear 
Medicine: A Catalog. Radiology, 2008. 248(1): p. 254-263.