A new software has been developed to measure the hip-knee condylar angle using digital radiological images and computer analysis. In a study comparing the new computerized method to conventional manual goniometry, 60 knee x-rays following total knee arthroplasty were measured twice by the same observer using both methods. Statistical analysis showed the computerized method produced highly reproducible results with a mean difference of 0.324 degrees between readings and a Pearson correlation of 0.999. The new software allows for precise, reliable and inexpensive measurement of joint angles that can be performed by non-medical personnel.

3. A new software for the measurementA new software for the measurement
of the hip-knee condylar angleof the hip-knee condylar angle
Mr.Mubarak M.F.A. KerimMr.Mubarak M.F.A. Kerim
Associate ProfessorAssociate Professor
Consultant 0rthopaedic SurgeonConsultant 0rthopaedic Surgeon
Khartoum North Teaching HospitalKhartoum North Teaching Hospital
MBBS MCh Orth(UK) FRCSI FRCSEd FRSM(UK)MBBS MCh Orth(UK) FRCSI FRCSEd FRSM(UK)

4. IntroductionIntroduction
 Osteoarthritis of the knee is a majorOsteoarthritis of the knee is a major
problemproblem
 Total knee Arthroplasty is theTotal knee Arthroplasty is the
ultimate treatment.ultimate treatment.
 Success & longevity depends onSuccess & longevity depends on
many factorsmany factors
 Aims of TKA:Aims of TKA:
• Relief of painRelief of pain
• Restore alignmentRestore alignment

5. Technical AspectsTechnical Aspects
 Restoration of mechanical alignment.Restoration of mechanical alignment.
 Preservation of joint line.Preservation of joint line.
 Balanced ligaments.Balanced ligaments.
 Radiological evaluation is essentialRadiological evaluation is essential
for follow-upfor follow-up

7. The concept of ideal alignment inThe concept of ideal alignment in
total knee arthroplasty has beentotal knee arthroplasty has been
stressed by many authors.stressed by many authors.
 InsallInsall et al.et al. (1985) recommended to(1985) recommended to
err on the valgus angle.err on the valgus angle.
 Peterson & Engh (1988)Peterson & Engh (1988)
recommended a line passing throughrecommended a line passing through
the middle of the prosthesisthe middle of the prosthesis

8. Ideal Alignment in TKRIdeal Alignment in TKR
 RitterRitter et al.et al. (1994) recommended a(1994) recommended a
slight amount of valgus or neutralslight amount of valgus or neutral
alignment.alignment.
 MaquetMaquet et al.et al. (1972) defined the(1972) defined the
alignment as a straight line from thealignment as a straight line from the
centre of the femoral head to thecentre of the femoral head to the
centre of the talus, passing throughcentre of the talus, passing through
the centre of the knee.the centre of the knee.

9. Methods used to measure angles ofMethods used to measure angles of
alignmentalignment
 Two methodsTwo methods
• Conventional manual methodConventional manual method
• Computerized methodComputerized method

10. Conventional methodConventional method
 Too tediousToo tedious
 Time consumingTime consuming
 Limitations of goniometryLimitations of goniometry
 Inherited inaccuraciesInherited inaccuracies
• Positioning problemsPositioning problems
• DeformityDeformity
• Lack of standardizationLack of standardization
• ParallaxParallax

11. Computerized methodComputerized method
 Easy, inexpensiveEasy, inexpensive
 Converts radiological images intoConverts radiological images into
clinical dataclinical data
 Data can be stored & retrievedData can be stored & retrieved
 Ability to manipulate imageAbility to manipulate image
 ReproducibleReproducible
 Allows non-medically qualifiedAllows non-medically qualified
personnel to measure angles.personnel to measure angles.

13. MaterialsMaterials
 Sixty radiological films of the knees afterSixty radiological films of the knees after
TKR done by me as specialist registrarTKR done by me as specialist registrar
(short films) were selected randomly.(short films) were selected randomly.
 Personal ComputerPersonal Computer
 ScannerScanner
 X-ray analyser softwareX-ray analyser software

16. MethodMethod
 Films scanned, digitized & stored TIFFilms scanned, digitized & stored TIF
 Two sets of readings, two weeksTwo sets of readings, two weeks
interval – single observerinterval – single observer
 Select 4 points on the imageSelect 4 points on the image
• Two on the lower edge of the femoralTwo on the lower edge of the femoral
componentcomponent
• Two on the upper edge of the tibialTwo on the upper edge of the tibial
componentcomponent

17. Method continuedMethod continued
 Draw a box on the femur as farDraw a box on the femur as far
proximally as the X-ray allowsproximally as the X-ray allows
 Click on the analyserClick on the analyser

18. Computerised routineComputerised routine
 The grey scale 0-256.The grey scale 0-256.
. Precision of measurements depends on degree of. Precision of measurements depends on degree of
resolutionresolution
 Digitised x-ray with the grey values over theDigitised x-ray with the grey values over the
image, anatomical features still identified on it.image, anatomical features still identified on it.
 Algorithm used for automatic identification ofAlgorithm used for automatic identification of
boundaries between bone and soft tissue.boundaries between bone and soft tissue.
 Within an area the computer detects bony edges.Within an area the computer detects bony edges.

21. ResultsResults
Results obtained were named readingResults obtained were named reading
1 and reading 21 and reading 2
The pairedThe paired tt-test and Pearson-test and Pearson’’ss
correlation were used to analyse thecorrelation were used to analyse the
results.results.

22. ResultsResults
 Readings were named reading 1 & 2Readings were named reading 1 & 2
 The paired t-test and PearsonThe paired t-test and Pearson’’ss
correlation were used to analysecorrelation were used to analyse
results.results.

23. Paired sample statisticsPaired sample statistics
 Mean of reading 1 is 9.789Mean of reading 1 is 9.789
 Mean of reading 2 is 10.112Mean of reading 2 is 10.112
 Mean of difference is 0.324Mean of difference is 0.324
 Minimum difference is 0.167Minimum difference is 0.167
 Maximum difference is 3.13Maximum difference is 3.13
 STD of mean difference is 1.214STD of mean difference is 1.214
 T-test is 0.937T-test is 0.937
 Pearson correlation 0.999Pearson correlation 0.999
 Confidence interval is 2.055Confidence interval is 2.055

24. Intra-observer variabilityIntra-observer variability
13%
28%
41%
12%
3% 3%
0 - .499
.5 - .999
1 - 1.499
1.5 - 1.99
2 - 2.499
> 2.5

26. 0
5
10
15
20
25
30
35
40
0-4 4 to 6 6 to 9 >9
First reading in degrees
Second reading in degrees

27. DiscussionDiscussion
 Computer reduces errors arising fromComputer reduces errors arising from
subjective component of conventionalsubjective component of conventional
method.method.
 This method automatically determines theThis method automatically determines the
long axis of the bone.long axis of the bone.
 Cost is reduced by using personalCost is reduced by using personal
computer.computer.
 Image manipulation does not substituteImage manipulation does not substitute
for poor quality x-rays.for poor quality x-rays.
 Visual feedback is important in certainVisual feedback is important in certain
situations.situations.

29. Figure 1 : Intra Observer
13%
28%
41%
12%
3% 3%
0 - .499
.5 - .999
1 - 1.499
1.5 - 1.99
2 - 2.499
> 2.5

30. ConclusionConclusion
 Computerized method is preciseComputerized method is precise
 ReliableReliable
 In-expensiveIn-expensive
 Can enable non-medically qualified personnel toCan enable non-medically qualified personnel to
measure angles and distances in TKRmeasure angles and distances in TKR
 Matches all knee scoresMatches all knee scores

31. LimitationsLimitations
 Positioning of the limb.Positioning of the limb.
 Morphological factors.Morphological factors.
 Quality of radiographsQuality of radiographs

32. Thank You !Thank You !

33. Thank youThank you