H. Nguyen (Utrecht, NL)
Universitair Medisch Centrum UtrechtPresenter Of 2 Presentations
P191 - Visual Inspection to Determine Leg Alignment is not Reliable; Whole Leg Radiographs are Advised
Abstract
Purpose
Gold standard for diagnosing malalignment is weight bearing Whole Leg Radiograph (WLR) and technological advancements led to a significant decrease in radiation dosage. However, WLR is not always part of the standard workup for patients with knee pathology and often only obtained when there is a suspicion for malalignment during physical examination (visual inspection). Therefore, malalignment might be missed if visual inspection is unreliable. The aim of this study is to investigate the extent of missed malalignment when relying solely on visual inspections of the legs.
Methods and Materials
This study enrolled 50 patients. Each patient underwent a WLR, additionally a standardized digital photograph was taken of the lower limbs (Figure 1). Four persons (different experience levels) rated the digital photograph twice (unaware of the Hip Knee Angle (HKA) on the WLR) and placed them in the category: severe valgus (>5°), moderate valgus (2°-5°), neutral, moderate varus (2°-5°), and severe varus (>5°). Ratings were compared to the measured Hip Knee Angle (HKA) on the WLR. Raters’ performance based on experience years was tested for possible differences. 
Results
The percentage of incorrect visual leg axis assessment ranged between 47.9% - 67.0% (Figure 2). With Spearman’s rho of 0.499 (p<0.01) between the visual ratings and measured HKA on the WLR. Figure 2 also plots the 4 raters with different experience levels separately. Chi-Square tests for homogeneity between the 4 raters resulted in no significant differences (χ2=1.651, p=0.199).
Conclusion
Visual inspection of the lower limb alignment was moderate reliable, where in 47.9% - 67.0% of the cases the assessment was incorrect when compared to the measured HKA. Standard whole leg radiographs should be obtained to determine the correct leg axis.
P197 - A New Protocol for Obtaining Whole Leg Radiographs with Excellent Reproducibility
Abstract
Purpose
Whole Leg Radiographs (WLR) are the gold standard for diagnosing malalignment and for pre-operative osteotomy planning. Positioning can affect the reproducibility of the measured hip knee angle (HKA), resulting in insufficient diagnostics and preoperative plans. We developed an easy-to-use WLR protocol by standardizing patient positioning and focusing on reproducibility (Figure 1). This study aims on testing this reproducibility.
Methods and Materials
This study enrolled 30 patients for a test-retest analysis. Each patient underwent two bilateral WLRs on the same day using the investigated positioning protocol. Three observers measured the HKA, mechanical medial proximal tibial angle (mMPTA), mechanical lateral distal femoral angle (mLDFA), and joint line convergence angle (JLCA) on the two radiographs. Twice each, with one week between.
Results
The intra-observer and inter-observer reliabilities were excellent, with intraclass correlation coefficients (ICCs) between 0.990 and 0.996. The ICCs between the measured HKA (0.985), mMPTA (0.922), and mLDFA (0.903) on the two separate radiographs were excellent. The ICC between the JLCA measured on the first and second WLR was moderate with 0.632. The mean absolute error between the HKA, mMPTA, mLDFA, and JLCA measurements on the first and second WLR were respectively: 0.442°, 0.783°, 0.828°, and 0.794°, which were all sub 1° with narrow standard deviations (Figure 2).
Conclusion
The investigated novel WLR positioning protocol produced excellent and reproducible HKA measurements, with clinically acceptable degrees of error. We recommend applying this easy-to-use protocol when obtaining WLRs for osteotomy planning.
Presenter Of 2 Presentations
P191 - Visual Inspection to Determine Leg Alignment is not Reliable; Whole Leg Radiographs are Advised
Abstract
Purpose
Gold standard for diagnosing malalignment is weight bearing Whole Leg Radiograph (WLR) and technological advancements led to a significant decrease in radiation dosage. However, WLR is not always part of the standard workup for patients with knee pathology and often only obtained when there is a suspicion for malalignment during physical examination (visual inspection). Therefore, malalignment might be missed if visual inspection is unreliable. The aim of this study is to investigate the extent of missed malalignment when relying solely on visual inspections of the legs.
Methods and Materials
This study enrolled 50 patients. Each patient underwent a WLR, additionally a standardized digital photograph was taken of the lower limbs (Figure 1). Four persons (different experience levels) rated the digital photograph twice (unaware of the Hip Knee Angle (HKA) on the WLR) and placed them in the category: severe valgus (>5°), moderate valgus (2°-5°), neutral, moderate varus (2°-5°), and severe varus (>5°). Ratings were compared to the measured Hip Knee Angle (HKA) on the WLR. Raters’ performance based on experience years was tested for possible differences.
Results
The percentage of incorrect visual leg axis assessment ranged between 47.9% - 67.0% (Figure 2). With Spearman’s rho of 0.499 (p<0.01) between the visual ratings and measured HKA on the WLR. Figure 2 also plots the 4 raters with different experience levels separately. Chi-Square tests for homogeneity between the 4 raters resulted in no significant differences (χ2=1.651, p=0.199).
Conclusion
Visual inspection of the lower limb alignment was moderate reliable, where in 47.9% - 67.0% of the cases the assessment was incorrect when compared to the measured HKA. Standard whole leg radiographs should be obtained to determine the correct leg axis.
P197 - A New Protocol for Obtaining Whole Leg Radiographs with Excellent Reproducibility
Abstract
Purpose
Whole Leg Radiographs (WLR) are the gold standard for diagnosing malalignment and for pre-operative osteotomy planning. Positioning can affect the reproducibility of the measured hip knee angle (HKA), resulting in insufficient diagnostics and preoperative plans. We developed an easy-to-use WLR protocol by standardizing patient positioning and focusing on reproducibility (Figure 1). This study aims on testing this reproducibility.
Methods and Materials
This study enrolled 30 patients for a test-retest analysis. Each patient underwent two bilateral WLRs on the same day using the investigated positioning protocol. Three observers measured the HKA, mechanical medial proximal tibial angle (mMPTA), mechanical lateral distal femoral angle (mLDFA), and joint line convergence angle (JLCA) on the two radiographs. Twice each, with one week between.
Results
The intra-observer and inter-observer reliabilities were excellent, with intraclass correlation coefficients (ICCs) between 0.990 and 0.996. The ICCs between the measured HKA (0.985), mMPTA (0.922), and mLDFA (0.903) on the two separate radiographs were excellent. The ICC between the JLCA measured on the first and second WLR was moderate with 0.632. The mean absolute error between the HKA, mMPTA, mLDFA, and JLCA measurements on the first and second WLR were respectively: 0.442°, 0.783°, 0.828°, and 0.794°, which were all sub 1° with narrow standard deviations (Figure 2).
Conclusion
The investigated novel WLR positioning protocol produced excellent and reproducible HKA measurements, with clinically acceptable degrees of error. We recommend applying this easy-to-use protocol when obtaining WLRs for osteotomy planning.