Alternative Site Testing Heidi H. Kecskemethy, RD, CSP, CBDT Biomedical Research & Medical Imaging Departments.

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?