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Osteochondrosis is a disturbance of normal endo-chondral ossification characterized by abnormal

maturation of the growing cartilage. Osteochondrosis is termed OCD when cartilage fragmentation occurs.1 Osteochondritis dissecans commonly occurs on the MAHC. In addition to lesions of the medial coronoid or anconeal processes, dogs with elbow dysplasia may have OCD of the MAHC or may have an abnormal sur-face on the medial humeral condyle without OCD. That abnormal surface is often referred to as a kissing lesion. Osteochondritis dissecans of the humeral condyle is a genetic disease for which heritability ranges from 0.3 to 0.77 in previous reports.2,3 Osteochondritis dissecans has a lower prevalence than fragmentation of the MCP.4 It occurs almost exclusively in dogs weighing > 20 kg as adults.3,5 When present, OCD often affects both elbow

Comparison of five radiographic views for assessment of the medial aspect

of the humeral condyle in dogs with osteochondritis dissecans

Guillaume Chanoit, DEDV; Nikita N. Singhani, DVM; Denis J. Marcellin-Little, DEDV; Jason A. Osborne, PhD

Objective—Tocompare5 radiographicviews for thedetectionofosteochondritisdisse-cans(OCD)indogswithsignsofelbowjointpain.Animals—53 dogs (100 elbow joints) with forelimb lameness and signs of elbow jointpain.Procedures—Mediolateral (ML), flexed ML, craniocaudal (CC), craniolateral-caudomedialoblique (Cr15L-CdMO),anddistomedial-proximolateraloblique (Di35M-PrLO) radiographicviews of the 100 elbow joints were obtained. Four examiners graded radiographs withregardtoelbowjointOCD.Jointswereassessedbyuseofarthroscopy.Receiveroperat-ingcharacteristic(ROC)curves,kappameasureofagreement,andFisherexacttestsforassociationbetweenmediandiagnosticvalueandactualstatuswerecomputed.Results—47jointshadanabnormalmedialaspectofthehumeralcondyle(MAHC),andamongthem,11hadOCD.ThepresenceoffracturesofthemedialcoronoidprocesswassignificantlyandpositivelycorrelatedwiththepresenceofabnormalitiesoftheMAHC(r=0.40),butwasnegativelycorrelatedwiththepresenceofOCD(r=–0.32).At95%specific-ity,mediansensitivitiestodetectOCDwere57%forCr15L-CdMO,56%forCC,10%forflexedML,7%forML,and4%forDi35M-PrLOviews.TheareasundertheROCcurvesweresignificantlylargerfortheCr15L-CdMOandCCviewsthanfortheML,flexedML,andDi35M-PrLOviewsforthedetectionofOCD.OnlytheCr15L-CdMOandCCviewsallowedaccuratedetectionofOCD.Conclusions and Clinical Relevance—Indogswithsignsofelbowjointpain,theCr15L-CdMOviewisexcellentandtheCCviewwasgoodfordetectionofOCD.(Am J Vet Res2010;71:780–783)

joints. Eleven of 21 (52%) dogs with elbow joint OCD were affected bilaterally in 1 report.6 The radiographic signs of elbow joint OCD include abnormal shape of the medial aspect of the humeral condyle and a semilu-nar or conical radiolucency potentially surrounded by a radiopaque area.7 In a report8 involving 18 dogs with elbow joint dysplasia, CC and flexed ML views had a 46% sensitivity at 100% specificity and a 73% accuracy to detect elbow joint OCD. These studies unfortunately were based on small samples, included a limited num-ber of radiographic views, and did not use assessment

Received February 5, 2009.Accepted June 25, 2009.From the Department of Clinical Sciences, College of Veterinary Med-

icine (Chanoit, Singhani, Marcellin-Little), and Department of Sta-tistics, College of Agriculture and Life Sciences (Osborne), North Carolina State University, Raleigh, NC 27606.

The authors thank Drs. Laurent Blond, Philippe Haudiquet, and Lisa Jesse for technical assistance.

Address correspondence to Dr. Marcellin-Little (denis_marcellin@ncsu.edu).

AbbreviAtionsAUC Area under the curveCC CraniocaudalCr15L-CdMO Craniolateral-caudomedial obliqueDi35M-PrLO Distomedial-proximolateral obliqueMAHC Medial aspect of the humeral condyleMCP Medial coronoid processML MediolateralOCD Osteochondritis dissecansROC Receiver operating characteristic

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methods that would allow evaluation of their diagnos-tic values regardless of examiner specificity. The pur-pose of the study reported here was to determine and compare sensitivities and specificities of 5 radiographic views used to assess the presence of abnormalities and OCD lesions of the humeral condyle by use of ROC curve analysis in dogs with pain response to palpation of the elbow joint.9

Materials and Methods

Animals—Radiographs of 53 dogs enrolled in a previous study10 assessing a novel radiographic view aimed at enhancing the detection of fragmentation of the MCP were used. Dogs that were referred to the Cli-nique Vétérinaire de l’Ouest between June 1997 and July 1999 for forelimb lameness and signs of pain on palpation of the elbow joint were included in this study. Dogs were excluded from the study if they had an or-thopedic disease other than elbow joint dysplasia.

Data collection—The CC, Cr15L-CdMO, ML, flexed ML, and Di35M-PrLO views were made for both elbow joints under sedation. All radiographs were made by use of a nonrigid table-top technique with a detailed film-screen system. Intensity ranged from 9.6 to 15 mA, and penetrability ranged from 50 to 60 kVp. Arthrosco-py of both elbow joints was performed during general anesthesia by a highly experienced arthroscopist using the medial portals of a 2.7-mm-diameter 30° oblique arthroscopea placed in a 3.5-mm-diameter sleeve. The joints were distended and irrigated with lactated Ring-er’s solution. The ulnar notch, lateral coronoid process, radial head, humeral capitulum, humeral trochlea, MCP, and medial collateral ligaments were evaluated. The cartilage of the MAHC and MCP was probed. The procedures were recorded on videotape, and the lesions were documented with still pictures. Lesions (fragmen-tation of MCP and OCD lesions) observed during this examination were curetted or excised. Meloxicam (0.2 mg/kg) was injected IM at the end of surgery for analge-sia. The dogs were discharged on the day of surgery.

Four examiners evaluated the radiographs inde-pendently and in random order. Examiners included 2 board-certified surgeons and 2 radiology residents. The examiners assessed the medial aspect of the humeral condyle for the presence of OCD and graded each radio-graph as definitely normal, probably normal, possibly abnormal, probably abnormal, and definitely abnormal. Arthroscopically, elbow joint OCD was diagnosed when a flap was present at the MAHC. An abnormal MAHC was diagnosed when fibrillation or small, partial-thick-ness lesions were seen. The ROC curve analysis was used to estimate sensitivities of the CC, Cr15L-CdMO, ML, and flexed ML views at estimated specificities of 90% and 95% for the detection of an OCD fragment.9,11

Statistical analysis—The arthroscopic findings were used as the gold standard for statistical analysis. The radiographic findings were compared with the findings of arthroscopy by use of ROC curve analysis.11 Area under the curve of the ROC for the median rat-ing among 4 raters was estimated empirically for detec-tion of an OCD fragment by use of the trapezoid rule.9

Pairwise significance tests of the hypothesis of equal population AUC were conducted.12,13,b For each of the 5 views, the κ measure of agreement was computed for all 6 pairs of raters.14 The Fisher exact test was used to test for an association between the diagnosis of OCD provided by use of the median rating of a given view and the actual status of the dog. For these analyses, the median rating was compared with a threshold of possi-bly abnormal. If the median of the 4 raters was possibly abnormal, probably abnormal, or definitely abnormal, the joints would be diagnosed as having OCD. Pearson correlation coefficients between abnormalities of the MAHC and lesions of the MCP were calculated. Results were considered significant at P < 0.05.

Results

One hundred joints of 53 dogs were included in this study.10 Forty-seven joints had an abnormal MAHC, and among them, 11 joints had OCD of the MAHC. Forty-six of the 47 joints with abnormal MAHC had an abnormal medial coronoid process. The presence of abnormalities (fissures or fractures) of the MCP was positively correlated with the presence of abnormalities of the MAHC (r = 0.41; P < 0.001). The presence of fractures of the MCP was also positively correlated with the presence of abnormalities of the MAHC (r = 0.40; P < 0.001). The presence of abnormalities (fissures or fractures) of the MCP was not correlated with the pres-ence of OCD of the MAHC (r = 0.09; P = 0.380). The presence of fractures of the MCP was negatively cor-related with the presence of OCD of the MAHC (r = –0.32; P = 0.001).

At a specificity of 90%, median sensitivities to de-tect OCD were 84% for the Cr15L-CdMO view, 73% for the CC view, 20% for the flexed ML view, 14% for the ML view, and 7% for the Di35M-PrLO view. At a specificity of 95%, median sensitivities to detect OCD were 57% for the Cr15L-CdMO view, 56% for the CC view, 10% for the flexed ML view, 7% for the ML view, and 4% for the Di35M-PrLO view. The ROC curves rep-resenting the detection of OCD of the MAHC by use of the median value of the examiners for each view were

Figure 1—Receiver operating characteristic curves for detectionofOCDof theMAHC in100elbow jointsof53clinicallyaffecteddogscalculatedonthebasisofthemedianvaluesof4independentradiographic readers, compared with findings on arthroscopy.The5curvesrepresentthetrue-positivefraction(sensitivity)of5radio-graphicviews todetectOCDatvarious false-positive fractions (1-specificity).Theareasunderthecurvesforthevariousradiographicviewsareproportionaltothediagnosticvaluesoftheviews.CCO=Cr15L-CdMOview.D=Di35M-PrLOview.FML=FlexedMLview.

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drawn (Figure 1). The AUCs for the Cr15L-CdMO and CC views were significantly larger than the AUC for the ML, flexed ML, and Di35M-PrLO views for the detec-tion of OCD lesions of the MAHC (Table 1). The in-ter-rater agreement (kappa statistic) was good for the Cr15L-CdMO view, fair for the CC view, and slight for the ML, flexed ML, and Di35M-PrLO views (Table 2). Detection of OCD on Cr15L-CdMO and CC radiograph-ic views was significantly associated with the presence of arthroscopic lesions of the MAHC (P < 0.001 for the Cr15L-CdMO view and CC view), but detection of OCD on ML and flexed ML views was not (P = 0.383 for the ML view and P = 0.110 for the flexed ML view).

Discussion

The aim of this study was to compare the diagnos-tic values of 5 radiographic views to detect OCD lesions of the MAHC in dogs with pain response to palpation of the elbow joint. The radiographic findings were com-pared with the arthroscopic findings of OCD. We in-cluded the Di35M-PrLO view, an oblique mediolateral projection that has better diagnostic value than other radiographic views to detect the presence of an abnor-mal medial coronoid process.10 We anticipated that the Di35M-PrLO view would enhance the detection of OCD lesions, compared with ML and flexed ML views, because the medial and lateral aspects of the condyle are offset on the Di35M-PrLO view but not on the ML and flexed ML views. This was not confirmed by the results of the present study. The ability to detect OCD

of the MAHC on the Di35M-PrLO view was probably negatively affected by the fact that the MAHC appeared foreshortened and distorted by superimposition of the ulna and MAHC and by residual superimposition of the medial and lateral aspects of the humeral condyle. Also included was a craniolateral to caudolateral oblique view because that view possibly enhances the detection of abnormalities on the MAHC.15,16 Although the re-ported obliquity of the craniomedial view ranged from 15° to 50° in previous reports, we selected a 15° angle because that view was validated in a previous report.17 The fact that the dogs included in the present study had a pain response to palpation of the elbow joint de-creased the number of patients with true-negative test results. Although this may have influenced the results of this study, this situation matches clinical situations in which patients undergo radiographic and arthroscopic evaluations of their elbow joints.

Several dogs in the present study had a fragmented medial coronoid process. Abnormalities of the MAHC were more likely to occur in joints with fissures or frac-tures of the MCP than in joints with normal MCP. By comparison, OCD of the MAHC was less likely to oc-cur in joints with fractures of the MCP than in other joints.

We used ROC curve analysis because that method provides more perspective on the value of diagnostic tests than other methods. When a fixed threshold is used to diagnose an abnormality, the personality of a rater might influence the conventional assessment of a diagnostic test. For example, the sensitivity of a test is decreased and its specificity is increased when a rat-er is conservative in judgment of the test. With ROC curve analysis, however, the diagnostic value of a test is determined across all thresholds, regardless of reader personality. The area under the ROC curve is a descrip-tion of the overall quality of a diagnostic test: the higher the AUC, the more efficient a test is to discriminate be-tween diseased and disease-free populations. In recent veterinary publications,18,19 the area under ROC curves for tests that were considered accurate by the investiga-tors varied between 0.94 and 0.88. The Cr15L-CdMO and CC views were in that range for detection of OCD of the MAHC.

In the present study, arthroscopy was used as a gold standard for the assessment of kissing and OCD lesions of the MAHC because it allows direct inspection of all compartments of the elbow joint.20 Computed tomography has recently been advocated as a reliable test and compared favorably with arthroscopy to assess fragmentation of the medial coronoid process, kissing lesions on the humeral condyle, and irregular radial incisure (notch) in 101 canine elbow joints.21 In that report, 8 elbow joints appeared normal via arthroscopy but a lesion of the MCP was detected via computed to-mography, suggesting that dogs may have normal car-tilage over the MCP, as seen arthroscopically, but may also have abnormal subchondral bone in that region. A recent report22 comparing the detection of osteo-chondral lesions of the talus in humans identified a sensitivity of 70% (specificity, 94%) for radiographs, 81% (specificity, 99%) for computed tomography, 96% (specificity, 60%) for magnetic resonance imaging, and

View AUC CC ML FlexedML Di35M-PrLO

Cr15L-CdMO 0.944a 0.274 0.001 0.001 0.001CC 0.885a — 0.004 0.003 0.003ML 0.638b — — 0.694 0.678FlexedML 0.616b — — — 0.956Di35M-PrLO 0.611b — — — —

—=Notapplicable.a,bAUCwithdifferentsuperscriptsdiffersignificantly(P0.05).

Table1—AreasundertheROCcurvesfor5radiographicviewsusedfordetectionofOCDoftheMAHCin100elbowjointsof53clinicallyaffecteddogs(secondcolumn[AUC]),andP valuesfor comparisons between radiographic views (third to sixthcolumns).

View Rater Rater2 Rater3 Rater4

Cr15L-CdMO Rater1 0.51 0.45 0.49 Rater2 — 0.48 0.62 Rater3 — — 0.53CC Rater1 0.40 0.33 0.22 Rater2 — 0.45 0.47 Rater3 — — 0.31ML Rater1 0.20 0.19 –0.01 Rater2 — 0.16 –0.03 Rater3 — — 0.07FlexedML Rater1 0.27 0.14 0.13 Rater2 — 0.12 0.11 Rater3 — — 0.07Di35M-PrLO Rater1 0.02 –0.09 0.17 Rater2 — 0.24 0.09 Rater3 — — 0.06

SeeTable1forkey.

Table2—Inter-rateragreement(kappastatistic)for5radiographicviewstodetectOCDandanabnormalhumeralcondyleindogs.

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100% (specificity, 97%) for arthroscopy. In that study, arthroscopy and computed tomography were clearly superior to radiographs, and magnetic resonance imag-ing had a surprisingly low specificity for detection of osteochondral lesions.

Results of the present study indicated that the Cr15L-CdMO view was excellent, the CC view was good, and the 3 ML views were poor for detection of OCD by use of the scoring system proposed by Tape.23 The observed AUC determined by use of the Cr15L-CdMO view was greater than that for the CC view, al-though the difference was not significant. The sensitivi-ties of the Cr15L-CdMO and CC views to detect OCD lesions (84% and 73% at 90% specificity and 57% and 56% at 95% specificity, respectively) were higher than those reported in a study8 involving 18 dogs (sensitiv-ity, 46%). This discrepancy may have resulted from dif-ferences in the grading system and the relatively small sample size of the previous study. In the present study, inter-rater agreement was moderate for the Cr15L-CdMO view, fair to moderate for the CC and ML views, and poor to fair for the flexed ML view. The inter-rater agreement of the Di35M-PrLO view ranged from no agreement to fair agreement. In humans, the interob-server agreement of radiographic changes associated with hip osteoarthrosis was poor (κ agreement, 0.24) in 1 study.24

The Fisher exact test was used to investigate the ac-curacy of the use of the median grade of the 4 raters, us-ing a given view, to diagnose OCD. These analyses were conducted to quantify the amount of evidence against the null hypothesis that the diagnosis was unrelated to the actual status of the dog with regard to OCD. The Fisher exact tests computed the probability of observ-ing entries within a 2 X 2 contingency table that were more contradictory of the null hypothesis, while hav-ing the same fixed row and column totals. It was not possible to obtain a P value for the Di35M-PrLO view because none of the dogs had a median rating exceed-ing 3 by use of this view and the contingency table had 0 entries for the positive diagnosis. This most likely re-sulted from lack of rater confidence with regard to the presence of OCD when reading Di35M-PrLO views.

Results indicated that the Cr15L-CdMO view was excellent and the CC view was good for detection of OCD of the MAHC in dogs with a pain response to palpation of the elbow joint. The ML, flexed ML, and Di35M-PrLO views had low diagnostic value for detec-tion of OCD lesions.

a. Hopkins Forward-Oblique Telescope 30°, Storz France, Roissy CDG, France.

b. SAS, version 9.1.3, SAS Institute Inc, Cary, NC.

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