An academic presentation at the National orthopaedic hospital dala, kano

1. DISCUSS IMAGING IN
ORTHOPAEDICS
BY
DR MUHYIDEEN SHEHU
NOH DALA-KANO

2. SYNOPSIS
• INTRODUCTION
• IMAGING TECHNIQUES
• GENERAL APPLICATIONS OF IMAGING IN ORTHOPAEDICS
• DIAGNOSTIC
• PREOP PLANNING
• THERAPEUTIC
• MONITORING OF TREATMENT
• HAZARDS OF SOME IMAGING MODALITIES
• CONCLUSION

3. INTRODUCTION
• Imaging started with discovery of X-rays
by Wilhelm Konrad RÖntgen in 1895
• Initial application of radiography lay in
the demonstration of fractures and
radio-opaque foreign bodies
• Subsequent parallel development of Radiology
and Orthopaedics had broaden the scope
• Today, high precision interventional therapeutic
procedures can be carried out

4. THE IMAGING TECHNIQUES

5. CLASSIFICATION OF IMAGING TECHNIQUES
• Current techniques in practice of orthopaedics include
1. Clinical photograph
2. Plain radiography (x-rays)
3. Computerized tomography (CT) scan
4. Ultrasound scan
5. Magnetic Resonant imaging (MRI)
6. Radionucleotide scanning
7. Bone Densitometry

6. CLINICAL PHOTOGRAPH
• First line imaging
• For Documentation and monitoring
• USES
• In trauma with soft tissue involvement
• In management of clubfoot pre-,
intra- and post correction
• Angular deformities of the limb

7. Electromagnetic radiation
• Travel at speed of light ≈ 300,000km/s
• Travel in straight lines
• Not affected by electric or magnetic fields
• Travel through a vacuum

8. Plain radiography (X-rays)
• Definition
• High energy radiation which undergo differential
absorption by tissues as they pass through the body
• A tungsten cathode is heated in a vacuum
• Generates high velocity electrons
• These are directed towards a tungsten anode
• On hitting the anode some are knocked out of orbit
to create x-rays
• Only 1% of these electrons are used to make the x-ray
beam
• 99% to heat

9. X-rays cont.
• Quantity of x-rays generated
• Proportional to the number of moving electrons
• Quality of x-rays generated
• Proportional to the speed of the electrons i.e the energy they have
• Two outcomes when x-ray interacts with matter
• Photoelectric absorption
• Compton scattering
• Dose
• Amount of energy absorbed per unit mass of matter – Gray(Gy)
• Equivalent Dose
• Radiological effect of dose as the energy absorbed per unit mass
• The unit is the Sievert(Sv) (1 J/kg)
• The millisievert (mSv), one thousand of a Sievert, is used medicine

10. X-rays cont.
• Dense tissues absorb more x-rays
• The x-rays exiting the body are captured on a cassette
• The film is removed from the cassette and processed
to give an image
• Digital images have:
• Greater flexibility and versatility
• Lesser dose of radiation
• Higher quality and resolution
• Fluoroscopy
• Real time imaging
• Dynamic assessment
• Digital subtraction techniques, enhancing contrast

11. X-rays cont..
uses
• Invaluable investigation in orthopaedics
• Have wide applications such as
• Diagnosis
• Planning of surgery
• Intraoperative assessment of fixation of fractures
• Monitoring of treatment and healing
• Occasionally for intervention, e.g. vertebroplasty, TFSI
advantages
• Cheap
• Easily available
• Good in assessing bone due to its high calcium content and intrinsic contrast

12. Computerized tomography
(CT) scan
• X-rays are delivered by a fan shaped rotating
tube on a gantry
• Sensitive detectors record the attenuated
x-rays
• An image is formed on a computer
• Each image is made up of pixels
• Each pixel has depth as it is 3D-termed a
voxel (volume)
• Attenuation is the amount of x-rays
absorbed by tissues
• Different tissues have different attenuations

13. CT cont.
• Hounsfield units describe the
attenuation co-efficient of tissues
• Bone is 1000 Hu
• Water is 0 Hu
• Air is – 1000 Hu
• There is a much wider range of
attenuation co-efficients than the
greyscale a human eye can perceive
• Therefore we use different windows
for different tissue types
• This allows the whole range of attenuations
to be displayed and improves overall detail

14. CT cont.
• Advantages of CT
• Reconstruction possible in any plane desired
• Good for surgical planning in complex fractures
• 3D reconstruction
• Excellent resolution of cortical bone
• Better soft tissue attenuation than plain x-ray
• CT guided biopsy
• CT with contrast
• Disadvantages of CT
• Availability
• High radiation dose
• More slices = more radiation
• Claustrophobia
• Patient need to lie flat for longer
• (never take an unstable patient to the CT scanner)

16. Ultrasound scan
• Ultrasound waves are produced by a piezoelectric
ceramic crystal within a transducer
• By applying a voltage then reversing the voltage,
contraction and expansion of the crystals surface
is created
• This generate a compression wave-the ultrasound wave
• Pulse echo from tissue return to receiving transducer
• This again creates a voltage which is used to generate an image
• Depth of the structures calculated by time taken for the wave to
be reflected

17. Ultrasound cont.
• Acoustic impedance
• Impedance between tissues creates echo
• Minimal difference between fat and muscle
• Most wave pass through
• Large difference between air and skin
• Most waves reflected
• Us gel
• High impedance between soft tissues and cortex
• High impedance = bright
• Low impedance = dark
• Different probes for different tissues
• High frequency probes = better resolution/superficial structures
• Low frequency probes = reduced resolution/ deeper structures

18. Ultrasound cont.
• Advantages
• Non-ionizing
• Cheap
• Portable
• Dynamic imaging
• Very good for cystic structures
• Biopsy, injection, aspiration
• Disadvantages
• Highly operator dependent
• Only for superficial structures
(cannot penetrate cortical bone)
• Limited field of view
• Poor resolution comparatively

19. Magnetic Resonant imaging (MRI)
• Uses superconducting magnets and
radiofrequency coils to manipulate
hydrogen ions (protons) to create a
detailed, high contrast image
• Normally protons spin around their
own random axis (nuclear spin)
• on application of a magnetic field (1.5-3 tesla)
• Their axis of spin is aligned with the magnetic
field-longitudinally
• In this position they are primed to absorb
energy

20. MRI cont..
• Energy is the delivered by a radiofrequency
pulse
• On delivery of the pulse, the energy primed
protons line of spine changes again to lie
transverse to the longitudinal axis
• Radiofrequency pulse is switched off
• The protons gradually stop spinning in the
transverse axis and loose their coherence
Realign with the longitudinal magnetic field
• Energy is released as they start realigning from
when pulse is switched off
• The released energy (echo) is detected by a
Radiofrequency receiver coil and converted to
a digital image
• Fourier transform equation

21. MRI cont..
• T2 signal
• Time taken for the protons to loose their coherence once radiofrequency turned off
• Water rich tissues have longer T2 time as they contain more protons
• Hence they release energy for a longer time and give a high signal
• T1 signal
• Time taken for 63% of the protons to return to the longitudinal spin axis
• Repetition time(TR) (msec)
• The time between repetition of pulses
• T2 images have very high TR time
• Otherwise the water dense tissues will not have released enough energy to detected If the
pulses are given frequently though, fat appears white rather than water
• Time to echo(TE) (msec)
• time from when the pulse is stopped to when the signal is measured

22. MRI cont..
• Different sequences
• T1 weighted - short TR (TR<1000ms)
- short TE (TE<60ms)
• Fat = bright
• Fluid = dark
• Defining anatomy
• T2 weighted – long TR (TR>1000ms)
- long TE (TE> 60ms)
• Fluid = bright
• Defining pathology
• Proton density (PD) – long TR(TR>1000ms)
- short TE(TE< 60ms)
• Part TI, part T2,
• Useful in certain situation e.g the meniscus

23. MRI cont..
• Contrast = Gadolinium
• Rare earth metal with 7 unpaired electrons
• Therefore it has a high net magnetic moment
• It more strongly affects hydrogen ions in close
proximity to the contrast
• This enhances the image and results in high
signal on T1 scans as well
• Therefore shows pathologic fluid collections
better (abscess)

24. MRI cont..
• Advantages
• No ionizing radiation
• High quality image
• Can be used with contrast
• Abscesses and intra-articular pathology
• Disadvantages
• Claustrophobia
• Noisy
• Not tolerated well by children
• Availability
• Contraindication to MRI e.g aneurysm clips and pace makers, internal hearing aids,
• Metal artifact
• MARS sequence
• Over diagnosis of asymptomatic pathology

25. Radionuclide imaging (bone scanning)
• Gamma rays emitted from a radioactive
isotope of Technetium 99 bound to a
phosphate to give a map of blood flow
and osteoblastic activity
• Technetium 99
• Unstable radioisotope itself
• Emits gamma rays
• Derived from the decay of molybdenum 99
• It has a short half-life of 6hours
• It is excreted via the kidneys
• Protect bladder by hydration and frequent micturition

26. Radionuclide imaging..
• Mechanism of action
• Technetium-99 is attached to methyl diphosphonate when injected IV
• The MDP interact with HA crystals in bone
• Depending on adequate vascularity to the area in question
• Because HA crystals are generated by osteoblasts mineralizing bone it is a
direct reflection of osteoblastic activity
• The gamma rays emitted by the T-99 are detected by a gamma camera
• A digital image is created giving a map of blood flow and osteoblastic activity

27. Radionuclide imaging…
• The 3 phases of a triple bone scan are:
• Vascular phase (1-2min.)
• Shows arterial flow and hyper-perfusion
• Blood pool phase (3-5min)
• Shows bone and soft tissue hyperemia
• Infection / inflammation
• Static phase (4hrs)
• Soft tissue activity has cleared leaving only bone activity

28. Radionuclide imaging…
• Single-photon emission computed
tomography-CT (SPECT-CT)
• Gamma camera with CT component
on the same scanner
• Multi-planar imaging
• Increasing resolution, decrease noise
and increase localization
• Positron emission tomography-CT (PET-CT)
• Exploiting increase metabolic rate of tumors
i.e glucose consumption
• e.g deoxyglucose labelled 18Flourine
(1/2 life 112 min.)

29. Radionuclide imaging…
• WBC scan
• Labeling patient’s own WBC with radioactive
tracer such as indium
• Accumulates in the reticuloendothelial system
e.g bone marrow, liver and spleen but also
areas of active infection
• Hybrid PET-MRI
• Potential increase bone metastasis assessment
and response to treatment

30. Radionuclide imaging..
• Useful for:
• Tumors (metastatic and primary esp in spine)
• Infection – osteomyelitis
• Stress fractures
• Prosthetic loosening/pain
• Paget's
• Disadvantages
• Poor specificity although very sensitive
• Radiation dose is fairly high
• False negative in areas of low blood supply
• E.g avascular bone, lytic tumor
• False negative in myeloma
• Myeloma inhibits osteoblasts

31. DEXA scans
• DEXA scanning
• Dual energy x-ray absorbimetry
• Utilizes x-rays of different energies
• Absorbed in different proportions
by bone and soft tissue
• Used to assess bone mineral density
• Scans of femur and lumbar spine
centered on L3 are taken

32. DEXA scans…
• Result interpretation
• Units of bone mineral density are g/cm²
• Values are related to the peak BMD of a young adult or matched by age
• The T score represents comparison with peak BMD of a young adult
• The Z score represents the age-matched score
• Sex and race are match in both
• Only difference is age matching in the z score
• The T score is used to determine whether there is osteoporosis
• The Z score is used to assess whether the reduced BMD is related to another
cause i.e lower than expected for age

33. DEXA scans..
• WHO criteria for osteoporosis relies on the T score
• 0 to – 1 = normal
• -1 to -2.5 = osteopenia
• < -2.5 = osteoporosis
• < -2.5 + fragility fracture = severe osteoporosis
• Disadvantages
• No differentiation between cortical and cancellous density
• Falsely high BMD in fractured sclerotic vertebrae and degenerative disease

35. GENERAL APPLICATION OF IMAGING IN
ORTHOPAEDICS
• Imaging is applied in orthopaedics practice in
• Diagnosis, classification and staging of diseases
• Preoperative planning and templating
• Intraoperative monitoring
• Therapeutic purposes
• Monitoring of treatment and healing process

36. DIAGNOSIS
• Almost all of the modalities are used to make or confirm diagnosis
• Plain radiography plays an invaluable role especially in trauma
• CT scan usually augments plain radiograph, though plays important
role in complex trauma
• Biopsies can be US, fluoroscopic or CT-guided
• DDH, joint collection by USS
• Bone scans
• Bone densitometry

37. PREOPERATIVE PLANNING
• Plain radiographs, CT scan with 3D reconstruction and MRI
• Plain radiographs used in templating
• MRI especially in spine, ligamentous injuries, oncology

38. INTRAOPERATIVE
• Fluoroscopy in fracture fixations
• Limb reconstructions
• Corrective osteotomies
• Spine fixations
• Minimally invasive surgeries and closed reductions and fixation

39. THERAPEUTIC/INTERVENTIONAL
PROCEDURES
• Arthrography/Diagnostic-therapeutic injections
• Facet injections
• Discography
• Vertebroplasty

40. MONITORING
• Fracture healing and status of the implants
• Endoprostheses
• Effect of treatment, e.g. Ricketts, osteoporosis

41. • Risks
• Cell death and distorted replication
• Cancers
• Thyroid
• 85% of papillary cancers thought to be radiation related
• others skin, breast, etc
• Cataracts
• Reducing risk (measures)
• Justify, optimize (ALARA), limit
• PPE
• Scatter
• The annual whole body Dose Equivalent Limit for
occupationally exposed persons is 20mSv

42. CONCLUSION
• Imaging is paramount in orthopaedics practice
• Sound knowledge and broad understanding of radiological techniques
as they applied to orthopaedics is paramount for the orthopaedics
surgeon

43. REFERENCES
• Ramachandran M, Ramachandran N and Saifuddin A. Imaging
Techniques. In: Ramachandran M (Ed). Basic Orthopaedic Sciences-
The Stanmore Guide. Hodder-Arnold; New York; .2007. PP51-60.
• Berquist TH. Imaging of Orthopaedic Fixation Devices and
Prostheses. Lippincott Williams & Wilkin, a Wolters Kluwer
Business. Philadelphia; 2009. PP1-9.
• Ebnezar J. Textbook of Orthopaedics. 4th ed. Jaypee. New Delhi. 2010.
• Rockwood C.A. et al. Rockwood and Green’s Fractures in Adults 6th
ed. Lippincott-Raven. Philadelphia. 2004. Mettler FA,
GuiberteauMJ. Essentials of nuclear medicine, 5th ed.
Philadelphia:WB Saunders; 2005.

44. THANK YOU