Alternative Site Testing
Heidi H. Kecskemethy, RD, CSP, CBDTBiomedical Research & Medical Imaging Departments
No disclosures to report
Overview
The Basics What are Alternative Sites? Recommended Body Sites to Measure Alternative Sites Candidates Case Study Conclusion
Equipment – Measuring Bone Density
DXA Whole Body, PA & Lateral Spine, Proximal Femur, Forearm, Lateral Distal Femur, Hand
US Calcaneus, Forearm, Tibia pQCT Forearm, Tibia QCT Spine, Other Sites MRI Spine, Femur, Other Sites
Each of these technologies have standard measurement sites Varies by machine
Normative values may or may not be available
What is Alternative Site Testing?
“Creative Imaging” Acquiring DXA at body sites other than those
typically recommended Applying the use of DXA in non-standard ways
– Innovation (e.g. hemiscans, subregions)– Patient as own control in serial scans– Serial scans with no normative values
ISCD Recommended Body Sites to Measure
Differs for Adults vs. Children 2013 ISCD Official Positions – Adult and Pediatric
Recommended Body Sites to Measure by DXAAdult Pediatric
Lumbar Spine (PA) Total Body Less HeadProximal Femur Lumbar Spine (PA)Forearm (if unable to measure hip and/or spine, hyperparathyroidism, obesity)
Adult Alternative Sites
ForearmDXA Recommended and Alternative Sites
WHOLE BODY
SUBTOTAL WHOLE BODY (TBLH)
LUMBAR SPINE
HIP
FOREARM
LATERAL DISTAL FEMUR
Adult Pediatric
Alternative Sites
Forearm
Proximal Femur(pediatrics)
Lateral Distal Femur
Alternative Sites - Forearm
Measures distal radius and ulna
Is a scan option on machines, with analysis protocols and norms
Is a recommended site for adults in certain circumstances (official positions):– unable to obtain hip and/or PA spine– patient has hyperparathroidism– patient exceeds weight limit of table
In Pediatrics Useful if patient exceeds weight limit of machine Useful if other sites not obtainable Utility has been shown to monitor site-specific change Correlated with strength indices obtained from
peripheral computed tomography (Dowthwaite, et al. JBMR 2011)
Norms are available
Alternative Sites - Forearm
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Drawbacks Normative data for Hologic
machines only Positioning can be challenging
– reach, contractures Poorest precision of all
measurement sites (Shepherd, at al. JBMR 2011)
Image source - Hologic
Alternative Sites – Forearm (Pediatrics)
Alternative Sites: Proximal Femur (Pediatrics)
Prior to pubescence, hip is undergoing ossification and mineralization
Can lead to errors: - bone detection - ROI placement - poor reproducibility
Boy 6 yearsUseable in skeletally mature children (post puberty)
Normative data available on machines for children 3 – 20 years
Girl 17 years
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Normative Data – Hip and Forearm
The Bone Mineral Density in Childhood Study (BMDCS) has published reference data on both hip and forearm scans http://www.bmdcspublic.com
Normative data for the forearm and hip scans available on certain DXA machines – source of data and age ranges may vary by manufacturer
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Alternate Sites: Lateral Distal Femur (LDF)
First developed in early 1990s by pediatric radiologist (Harcke) and pediatric orthopedic surgeon (Henderson)
Measures site most commonly fractured in non-weight bearing children
Increasingly used in pediatric facilities around the world
Developed because children with
neuromuscular involvement frequently have joint contractures,
non-removable indwelling artifacts
(tubes, pumps, metallic hardware), and
movement disorders
Alternate Sites: Lateral Distal Femur (LDF)
In children with physical disabilities, no clear link between LS BMD and fracture (Henderson, et al. Dev Med Child Neurol 1997; Henderson, et al. JBMR 2010)
Distal femur is most common site of fx in non-ambulatory children; 60 – 70% of fractures occurring in femur (Henderson, et al. Pediatrics 2002; Bachrach S, et al. Dev Med Child Neurol 2008)
Children who sustain a low impact fx are also more likely to sustain another fx (Goulding, et al. J Peds 2005)
Fx rate in non-ambulatory children with CP = 4%/year; increases to 7%/yr if already had 1 fx (Stevenson, et al. Pediatr Rehabil. 2006)
Alternate Sites: Lateral Distal Femur (LDF)
Alternate Sites: Lateral Distal Femur
Align femur with table axis Foam
blocks support leg not being scanned
Sandbags help with stabilization
From Zemel, et al. J Clin Densitom 2009
Comfortable side-lying position
Less prone to movement artifacts
Obtainable on most patients
Quick <2 min scan time
Can be acquired without sedation
The LDF scan is analyzed for 3 regions of interest:
• Region 1: Anterior distal metaphysis: essentially trabecular bone
• Region 2: Metadiaphysis: both trabecular & cortical bone
• Region 3: Diaphysis: primarily cortical bone
Alternate Sites: Lateral Distal Femur (LDF)
In children with physical disabilities, significant relationship between LDF bone density, fracture history, and ambulatory status
(Harcke, et al. J Clin Neuromusc Dis 2006; Haas, et al, Dev Med Child Neurol 2012; Henderson, et al, JBMR 2013)
www.lateraldistalfemur.orgDrawbacks Scan modality not resident on machines – scans acquired in
forearm mode Manual analysis using subregions Requires training on acquisition and analysis Normative values for Hologic machine only (ages 6 – 18 years)
Alternate Sites: Lateral Distal Femur (LDF)
Pediatric LDF analysis uses growth plate landmark for placement of ROIs
Adult analysis technique developed and published No adult normative data available yet
Alternate Sites: Lateral Distal Femur (LDF)
J Clin Densitom 2014
Candidates for Alternative Site Testing
Limiting circumstances affecting acquisition:Musculoskeletal issues Contractures
Inability to lie flat Movement disorders
Behavioral problems Cognitive deficits
Discomfort positioning Spinal Compression Fx
Severe Scoliosis Skeletal Malformations
Obesity Pain
Limited ROM Presence of artifacts (tubes, metallic
hardware)
Sample Diagnoses Cerebral Palsy Pelizaeus Merzbacher Disease
Rett Syndrome Spina Bifida
Muscular Dystrophy Skeletal Dysplasias
Genetic Syndromes Osteogenesis Imperfecta
Candidates for Alternative Site Testing
Kecskemethy, et al, J Ped Rehab Med 2014
Candidates for Alternative Site Testing
Case study
18 year old with Pelizaeus Merzbacher Disease– Leukodystrophy, CNS involvement, delayed development
through teens then deterioration, dysmyelination Non-ambulatory/non-weight bearing Scoliosis Hx orthopedic surgery – left hip osteotomy with plate Joint contractures Baclofen pump (to decrease muscle tone) No history of fractures Eats by mouth; on Ca and Vit D supplements
Case Study
Case Study
Z-scores
-5.1-6.3-5.8
Z-scores
-5.0-6.2-5.5
Summary DXA resultsLS (L1-L4) -5.3RDF R1 -5.0RDF R2 -6.2RDF R3 -5.5LDF R1 -5.1LDF R2 -6.3LDF R3 -5.8
Applying the use of DXA in non-standard ways
Alternative site testing used when standard sites are not available or more clinically relevant site desired
What if no sites available? What if no norms available? Do you still scan?
Patients undergoing pharmacotherapy for low BMD and fracture
Each patient serves as their own control Evaluate results for interval change over time
Examples:– Lateral spine BMD & BMC– BMD/BMC of site containing metal (as long as metal has
not changed)– Subregion analysis
Applying the use of DXA in non-standard ways
Scan modality not available on all models of machines
No normative values Each subject can serve as their
own control to measure interval change over time
ROI placement can be challenging with small patients
Applying the use of DXA in non-standard ways -Lateral Spine
Summary
Creative imaging is required for challenging patients and situations
Keeping reproducibility, precision and accuracy in mind is paramount
Understanding technical aspects of DXA is critical Alternative site measures have value and should be
considered if clinically justified Obtaining appropriate training is important
Acknowledgements
H. Theodore Harcke, MD Richard C. Henderson, MD, PhD Steven J. Bachrach, MD Nemours Departments of Medical Imaging
and Biomedical Research Families and Patients ISCD Pediatric Bone Course Faculty ISCD Meeting Planning Committee
Questions?
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