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Journal of Orthopaedic Surgery 2000, 8(1): 33–37

Address correspondence and reprint requests to: Dr Boonyarak Visutipol, Lerdsin General Hospital, Silom Road, Bangkok, 10500

Thailand.

Evaluation of Letournel and Judet classificationof acetabular fracture with plain radiographsand three-dimensional computerizedtomographic scan

Boonyarak Visutipol, Pornchai Chobtangsin, Bunyat Ketmalasiri, Narongchai Pattarabanjird andNamchai VarodompunInstitute of Orthopaedics, Lerdsin General Hospital, Bangkok, Thailand.

ABSTRACT

Letournal and Judet classification of acetabular fracture

is widely used. The classification is based on theidentification of fracture lines on plain radiographs.Three-dimensional CT scan was claimed to give a

better view of the fracture line.Our study showed that intraobserver

reproducibility and interobserver reliability werealmost the same when classification was done by usingplain radiographs and 3D-CT scan. And 3D-CT scandid not increase either the interobserver reliability orthe intraobserver reproducibility in classifying thefracture.

Key words: Letournal and Judet classification, acetabular fracture, three dimensional CT scan, intraobserver reproducibility, interobserver reliability

radiographs in AP, iliac and obturator oblique5,13 arecommonly used to evaluate the fracture lines in eacharea of the pelvis and acetabulum. However, due tothe complexity of the fracture, the accuracy of thediagnosis is in doubt.

It is claimed that two-dimensional computerizedtomography (2D-CT scan) (Fig. 2) gives more detail of the fracture lines and might give more accuracy inclassification.6,7,11 However, there are some difficulties

because a lot of images have to be viewed. Modernthree-dimensional computerized tomography (3D-CTscan) using a software program to create three-dimensional images from 2D-CT scan is said to give

better details of the fracture lines and gives moreaccuracy in classifying the fracture (Fig. 3).1,2,4

One way to measure the accuracy and efficiencyof a classification is to measure the intraobserver

reproducibility and interobserver reliability, which isthe measurement of the agreement of one observer atdifferent periods of time and among differentobservers, respectively.

To our knowledge, there is no study whichcompares the use of plain radiographs and 3D-CT scanto classify acetabular fracture in terms of intra andinterobserver variation.

INTRODUCTION

Letournel and Judet classification (L-J classification)5,10

of the acetabular fracture is widely used (Fig. 1). Plain



34 Boonyarak Visutipol et al. Journal of Orthopaedic Surgery

Figure 1 L-J classification which was divided into 10 subtypes.

Figure 2 2D-CT scan



Vol. 8 No. 1, June 2000 Evaluation of Letournel and Judet classification of acetabular fracture 35

The objectives of this study were:1. To find the intraobserver reproducibility and

interobserver reliability of L-J classification withthe use of plain radiographs (AP, iliac andobturator oblique) and 3D-CT scan.

2. To evaluate if 3D-CT scan could increase theintraobserver reproducibility and interobserverreliability from the use of plain radiographs.

MATERIALS AND METHODS

20 sets of plain radiographs (AP, iliac and obturatoroblique) from 20 patients who had fractures of theacetabulum were studied. The names, hospital numberand date of X-ray were covered. The radiographs weremarked with serial numbers from 1 to 20.

These radiographs were reviewed by 5 orthopaedicsurgeons. Before the review, all the observers weresupplied with information and diagrams of the L-Jclassification of the acetabulum. The sets of plain

radiograph were reviewed twice with a 2-month

Figure 3 3D-CT scan: The images can be created in differentviews.

interval. The serial numbers of the radiographs werechanged before the second review.

The 3D-CT scans, which were created from 3 mmcut interval 2D-CT scans, from another set of 20patients, were reviewed in the same manner as the

plain radiographs.Then intraobserver reproducibility and

interobserver reliability were evaluated by using theKappa test introduced by Cohen.3 The Kappacoefficient (K),3 which is the level of agreementcorrected by proportion of agreement by chance, wascalculated using an SPSS 7.5 software program andinterpreted by using Landis and Koch guidelines:9

values of less than 0.00 indicate poor agreement; 0.00to 0.20, slight agreement; 0.21 to 0.40, fair agreement;0.41 to 0.60, moderate agreement; 0.61 to 0.80,substantial agreement; and more than 0.80, excellent

agreement.

RESULTS

From our study, intraobserver reproducibility of theplain radiographs and 3D-CT scan were almost thesame (0.42 for plain radiographs and 0.44 for 3D-CTscan), and both were in a moderate level of agreement(Table 1). Interobserver reliability in both groups were0.24, which was in the fair level of agreement. Therefore3D-CT scan did not help increasing the reliability (Table

2).

Table 2Interobserver reliability

Kappa coefficients for interobserver reliability

Plain radiography mean K 0.24 (0.15 to 0.37)

3D-CT scan mean K 0.24 (–0.30 to 0.46)

Table 1Intraobserver reproducibility

Kappa coefficients for intraobserver reproducibility

Observer K plain radiograph K 3D-CT scan

1 0.33 0.47

2 0.59 0.38

3 0.24 0.46

4 0.56 0.59

5 0.39 0.30

mean Kappa for plain radiographs= 0.42 (0.24 to 0.59)mean Kappa for 3D-CT scan = 0.44 (0.30 to 0.59)



36 Boonyarak Visutipol et al. Journal of Orthopaedic Surgery

DISCUSSION

Plain radiography in AP and both oblique views of the pelvis, as described by Judet et al.,8 has long servedas the standard for diagnosis of acetabular fractures.

Modern computerized scan in 2 dimensions has beensuggested to be superior in the detection of fractureinvolving the sacrum, quadrilateral surface, acetabularroof, posterior acetabular lip and the abnormality of the joint space.6,12 The disadvantage is that manyimages have to be viewed. 3D-CT scan, which can berotated in different views and some parts can be erasedfor a better vision, was claimed to be more useful incharacterizing complex displacement of theacetabulum.1,2

Our study was not designed to evaluate theefficacy of the 3D-CT scan in identifying the fracture

lines. The objective of our study was to evaluate thelevel of agreement of one observer and among differentobservers in classifying acetabular fracture using L-Jclassification.

From our study, moderate intraobserverreproducibility (K = 0.42) and fair interobserverreliability (K = 0.24) were observed when theclassification was done using plain radiographs. Whenthe classification was done using 3D-CT scan, theintraobserver reproducibility increased slightly butremained in the moderate level of agreement (K = 0.42)while the interobserver reliability remained the same

(K = 0.24). We think the reasons why both theintraobserver reproducibility and interobserverreliability were low in L-J classification is because theclassification is too complicated (there are 10 types)and too difficult to differentiate one type from the otherespecially in complex fracture groups. Though 3D-CT

scan might have given a better detail of the fractureline, it did not help to improve either the intraobserverreproducibility or the interobserver reliability. Thissuggested that even when the fracture lines are moreclearly viewed, the classification is so complicated that

an accurate classification cannot be made.Among the observers, observer number 4 who is

specialized in trauma seems to have the highest Kappa both in plain radiographs and 3D-CT scan. Thissuggests that the level of experience might be animportant factor in determining the L-J classification.The effect of experience on determining L-Jclassification needs further study. However, even withthe most experienced surgeon, the Kappa coefficientwas still in the moderate level of agreement which,again, reflects the difficulty of the classification.

The question is whether it is really necessary to

differentiate one subtype from another in complexfracture groups when all of them require an extensiveapproach and the prognosis depends on thecomminution and the degree of reduction. Thus,simplification of the classification may be helpful inimproving the intraobserver reproducibility andinterobserver reliability.

CONCLUSION

Intraobserver reproducibility and interobserver

reliability were found to be low in L-J classificationand 3D-CT scan did not seem to increase them. Theresults of this study suggest that Letournel and Judetclassification might be too complicated and too difficultfor the average orthopaedic surgeon.

REFERENCES

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3. Dunn G. Design and analysis of reliability studies: The statistical evaluation of measurement errors. London: Edward Arnold,1989.

4. Gautsch TL, Johnson EE, Seeger LL. True three dimensional stereographic display of 3D-reconstructed CT scans of the pelvisand acetabulum. Clin Orthop 1994, 305:138–51.

5. Guyton JL. Fracture of hip, acetabulum, and pelvis. In: Crenshaw AH, ed. Campbell’s Operative Orthopaedics. 9th ed. StLouis: CV Mosby, 1998, 2234–52.

6. Harley JD, Mack LA, Winquist RA. CT of acetabular fractures. AJR 1982, 138:413–7.7. Hayes WC, Balkisson RAA. Current concepts in imaging of the pelvis and hip. Orthop Clin North Am 1997, 28:617–41.8. Judet R, Judet J, Letournel E. Fracture of the acetabulum: Classification and surgical approaches for open reduction: Preliminary

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Vol. 8 No. 1, June 2000 Evaluation of Letournel and Judet classification of acetabular fracture 37

11. Rafii M, Firooznia H, Golimber C, Waugh T Jr, Naidick D. The impact of CT in clinical management of pelvic and acetabularfractures. Clin Orthop 1983, 178:228–35.

12. Shirhoda A, Brashear HR, Staab EV. Computed tomography of acetabular fractures. Radiology 1980, 134:683–8.13. Tile M. Fracture of the acetabulum. In: Rockwood CA, ed. Rockwood and Green’s Fractures in Adults, 4th ed . Philadelphia:

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