This document discusses various imaging techniques used in orthopedics, including plain radiography, CT, ultrasound, MRI, radionuclide scanning, and bone densitometry. It provides details on how each technique works, its applications in orthopedics for diagnostic, pre-operative planning, therapeutic, and post-operative monitoring purposes. It also notes some limitations and hazards of certain modalities. The document aims to introduce orthopedic imaging techniques and their general uses.

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