Sang Hyeong Lee

Statistical Consideration for Bilateral Cases in Orthopaedic Research

BACKGROUND Statistical independence means that one observation is not affected by another; however, the principle of statistical independence is violated if left and right-side measures within a subject are considered to be independent, because they are usually correlated and can affect each other. The purpose of the present study was to analyze the violation of statistical independence in recent orthopaedic research papers and to demonstrate the effect of statistical analysis that considered the data dependency within a subject. METHODS First, all original articles that had been published in The Journal of Bone and Joint Surgery (American Volume) over a two-year period were evaluated. The analysis was designed to identify articles that included bilateral cases and possible violations of statistical independence. Second, a demonstrative logistic regression without consideration of statistical independence was performed and was compared with a statistical analysis that considered data dependency within a subject. Radiographs of 1200 hips in 600 patients were used to examine the differences in terms of odds ratios (with 95% confidence intervals) of the risk factors for hip osteoarthritis. RESULTS Four hundred and eighty-six original articles were reviewed, and 151 articles (including forty-one articles involving the hip, thirty-four involving the knee, twenty-one involving the foot or ankle, nineteen involving the shoulder, ten involving the hand or wrist, nine involving the elbow, and seventeen involving other structures) were considered to include bilateral cases. Of the 486 articles that were reviewed, 120 articles (25%) (including thirty-six articles involving the hip, twenty-six involving the knee, fifteen involving the foot or ankle, fourteen involving the shoulder, seven involving the elbow, six involving the hand or wrist, and sixteen involving other structures) were found to have possibly violated statistical independence. Demonstrative statistical analysis showed that logistic regression was not robust to the violation of statistical independence. The 95% confidence intervals of the odds ratios for the risk factors showed narrower ranges (1.13 to 2.68 times) when data dependency within a subject was not considered. CONCLUSIONS Researchers need to consider statistical independence when performing statistical analysis, particularly in studies involving bilateral cases. If data dependency within a subject is not considered, studies involving bilateral cases can bias results, depending on the context of those studies.

Validity and Reliability of Measuring Femoral Anteversion and Neck-Shaft Angle in Patients with Cerebral Palsy

BACKGROUND Increased femoral anteversion and coxa valga are common in patients with cerebral palsy. The purpose of the present study was to determine the validity and reliability of the methods that are commonly used to measure the proximal femoral geometry in patients with cerebral palsy. METHODS Thirty-six consecutive patients (mean age, eleven years; range, five to twenty years) with cerebral palsy were enrolled in the present study. The validity and the interobserver reliability of the physical examinations performed by three examiners were determined by comparing the results of a trochanteric prominence angle test, hip internal rotation measurements, and hip external rotation measurements (all with the patient in the prone position) with the amount of femoral anteversion on two-dimensional computed tomography. Validity and intraobserver and interobserver reliability were assessed by comparing the neck-shaft angle on the anteroposterior internal rotation radiograph of the hips with that on the multiplanar reformatted computed tomographic image. RESULTS The trochanteric prominence angle test showed excellent concurrent validity (R = 0.862, p < 0.001) and reliability (intraclass correlation coefficient, 0.809). Hip internal rotation also showed good concurrent validity (R = 0.787, p < 0.001) and excellent reliability (intraclass correlation coefficient, 0.889), whereas hip external rotation appeared to be unsuitable for predicting femoral anteversion. The neck-shaft angle on the anteroposterior internal rotation radiograph of the hips showed excellent concurrent validity (R = 0.892, p < 0.001) and reliability (intraclass correlation coefficient, 0.912). CONCLUSIONS A physical examination for determining femoral anteversion and the neck-shaft angle as measured on the internal rotation radiograph of the hips appear to be clinically relevant methods for evaluating the proximal femoral geometry and version in patients with cerebral palsy. Computed tomographic examination can probably be replaced by physical examination and an anteroposterior internal rotation radiograph of the hips for patients with stable hips who are able to walk.

Reliability and Validity of Radiographic Measurements in Hindfoot Varus and Valgus

BACKGROUND Clinical decision-making in the treatment of foot deformities is based primarily on the results of the physical examination and the radiographic findings. The purpose of this study was to determine the validity and reliability of commonly used radiographic measurements of hindfoot valgus and varus deformities. METHODS Seventy-two patients with hindfoot deformity (thirty-six hindfoot valgus, mean age 15.5 years; thirty-six hindfoot varus, mean age 30.2 years) were evaluated. Nine representative indices on weight-bearing radiographs were assessed. Three examiners measured the radiographic indices at two sessions, and intraobserver and interobserver reliability was determined. Discriminant validity of the radiographic measurements between hindfoot valgus and varus was evaluated. The correlation with pedobarographic findings in evaluating the distribution of foot pressure during gait was assessed for convergent validity. RESULTS Naviculocuboid overlap, anteroposterior talonavicular coverage angle, anteroposterior talus-first metatarsal angle, calcaneal pitch angle, and lateral talus-first metatarsal angle showed excellent reliability. Naviculocuboid overlap, anteroposterior talonavicular coverage angle, and anteroposterior talus-first metatarsal angle showed excellent discriminant validity (in terms of effect-size r) and convergent validity (in terms of correlation coefficients with pedobarography). CONCLUSIONS Naviculocuboid overlap, anteroposterior talonavicular coverage angle, and anteroposterior talus-first metatarsal angle are reliable and valid measures for the evaluation of hindfoot valgus and varus deformities.

Hip osteoarthritis and risk factors in elderly Korean population.

OBJECTIVE To investigate the prevalence of hip osteoarthritis (OA) in a community-based elderly Korean population and to identify its risk factors. DESIGN Radiographs of hip and knee were evaluated in 288 men and 386 women (age>or=65 years) that participated in the Korean Longitudinal Study on Health and Aging (KLoSHA). Minimum joint space widths (JSW), center-edge angles (CEA), and neck-shaft angles were measured on hip radiographs, and tibio-femoral angles on knee radiographs. Hip OA was defined as minimum JSW of <or=2mm or <or=2.5mm. The following potential risk factors of OA were examined; demographic data, acetabular dysplasia, large CEA (>or=40 degrees) and deformities of femoral neck and knee joint. Multivariate analysis with generalized estimating equation (GEE) model was performed to exclude confounding factors. RESULTS When hip OA was defined as JSW<or=2mm, the overall prevalence of the disease was 2.1% (95% confidence interval [CI], 1.0-3.2%), and only older age (>or=70 years) was identified as a significant risk factors with an odds ratio (OR) of 10.0. However, when hip OA was defined as a JSW of <or=2.5mm, the overall prevalence of the disease was 13.1% (95% CI, 10.5-15.6%), and older age (>or=70 years), female, large CEA (>or=40 degrees), and acetabular dysplasia (CEA<20 degrees) were identified as significant risk factors with ORs of 2.1, 2.1, 2.3, and 10.2, respectively. CONCLUSIONS The prevalence of hip OA in elderly Korean was 2.1% (JSW<or=2mm) in community-based population. Older age (>or=70 years), female, large CEA (>or=40 degrees), and acetabular dysplasia (CEA<20 degrees) appeared to be significant risk factors of hip OA.

Tibial Torsion in Cerebral Palsy: Validity and Reliability of Measurement

Physical examinations of tibial torsion are used for preoperative planning and to assess outcomes of tibial osteomy in patients with cerebral palsy (CP). The thigh-foot angle (TFA) and transmalleolar axis (TMA) are commonly used, and the second toe test recently was introduced. However, the validity and reliability of the three methods have not been clarified. This study was performed to evaluate the validity and reliability of these physical measures. We recruited 18 patients (36 limbs) with CP. During reliability sessions, three raters with various levels of orthopaedic experience independently measured tibial torsion using the three different methods during one day before surgery. Validity was assessed by performing a correlation study between physical examination and two-dimensional computed tomographic (CT) findings. Interobserver reliability was greatest for the TMA followed by TFA and then by the second toe test with intraclass correlation coefficients of 0.92, 0.74, and 0.57, respectively. In terms of the concurrent validity, the correlation coefficients (r) for the CT measurements were 0.62, 0.52, and 0.55. When depicting tibial torsion by physical examination, all three methods had substantial validity, but test reliability and validity were highest for TMA measurements.Level of Evidence: Level I, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Morphometric changes in the acetabulum after Dega osteotomy in patients with cerebral palsy

We carried out a morphometric analysis of the acetabulum following Dega osteotomy in patients with cerebral palsy using three-dimensional CT. We assessed 17 acetabula in 12 patients with instability of the hip. A Dega osteotomy and varus derotation femoral osteotomy were performed in all 17 hips. Three-dimensional CT scans were taken before and approximately one year after operation. Acetabular cover was evaluated using anterosuperior, superolateral and posterosuperior acetabular indices, and the change in the acetabular volume was calculated. Inter- and intra-observer reliability was assessed using the intraclass correlation coefficient. After the osteotomy, the anterosuperior, superolateral and posterosuperior cover had improved significantly towards the value seen in a control group. The mean acetabular volume increased by 68%.

Kinematic aspects of trunk motion and gender effect in normal adults

BackgroundThe purpose of this study was to analyze kinematic trunk motion data in normal adults and to investigate gender effect.MethodsKinematic trunk motion data were obtained for 20 healthy subjects (11 men and 9 women; age from 21 to 40 years) during walking a 9 m long lane at a self selected speed, namely, motions in the sagittal (tilt), coronal (obliquity), and transverse (rotation) planes, which were all expressed as motions in global (relative to the ground) and those in pelvic reference frame (relative to pelvis), i.e., tilt (G), obliquity (G), rotation (G), tilt (P), obliquity (P), rotation (P).ResultsRange of tilt (G), obliquity (G) and rotation (G) showed smaller motion than that of tilt (P), obliquity (P) and rotation (P), respectively. When genders were compared, female trunks showed a 5 degree more extended posture during gait than male trunks (p = 0.002), which appeared to be caused by different lumbar lordosis. Ranges of coronal and transverse plane motion appeared to be correlated. In gait cycle, the trunk motion appeared to counterbalance the lower extremity during swing phase in sagittal plane, and to reduce the angular velocity toward the contralateral side immediate before the contralateral heel strike in the coronal plane.ConclusionsMen and women showed different lumbar lordosis during normal gait, which might be partly responsible for the different prevalence of lumbar diseases between genders. However, this needs further investigation.

Effects of distal hamstring lengthening on sagittal motion in patients with diplegia Hamstring length and its clinical use

This study was undertaken to determine the effect of distal hamstring lengthening (DHL) on hip and knee sagittal kinematics, and to investigate the validity of modeled hamstring length for clinical use. Patient group consisted of 28 patients (56 limbs, mean age 7.4 years) with spastic diplegia who underwent bilateral DHL and tendo-Achilles lengthening with/without rectus femoris transfer (RFT) (DHL+RFT subgroup, 40 limbs; DHL subgroup, 16 limbs). Kinematic data was obtained by gait analysis, and hamstring lengths were obtained using a musculoskeletal modeling technique. Postoperatively, knee extension improved (p<0.001) without aggravating anterior pelvic tilt (p=0.565). However, DHL aggravated anterior pelvic tilt in the DHL subgroup (2.2 degrees, p=0.011). In terms of concurrent validity, hamstring length was found to be correlated with mean pelvic tilt (r=0.798, p<0.001) and popliteal angle (r=-0.425, p=0.001), but the correlation between hamstring length and knee flexion at initial contact was minimal (r=0.068, p=0.753). In terms of construct validity, DHL did not lengthen mean hamstring length (p=0.918). In conclusion, DHL appeared to significantly improve knee motion in patients with spastic diplegia. Furthermore, DHL did not increase pelvic tilt, when performed with RFT. Modeled hamstring length is believed to have limited validity in patients with cerebral palsy, because it does not reflect knee kinematics or postoperative change when DHL was combined with multilevel surgery.

Clinical relevance of valgus deformity of proximal femur in cerebral palsy.

Background Proximal femoral deformity related to physis has not been studied in patients with cerebral palsy (CP). This study was performed to investigate the clinical relevance of neck shaft angle (NSA), head shaft angle (HSA), and proximal femoral epiphyseal shape in patients with CP, which represent the deformities of metaphysis, physis, and epiphysis, respectively. Methods Three hundred eighty-four patients with CP (mean age 9.1 y, 249 males and 135 females) were included. Extent of involvement and functional states [Gross Motor Function Classification System (GMFCS) level] were obtained. Radiographic measurements including NSA, HSA, and qualitative shape of the proximal femoral epiphysis were evaluated and analyzed according to extent of involvement and GMFCS level. Reliability and correlation with each measurement were assessed. Multiple regression test was performed to examine the significant contributing factors to migration percentage (MP) that represents hip instability. Results NSA showed excellent interobserver reliability with intraclass correlation coefficients of 0.976. Correlation with the MP was higher in the NSA (r=0.419, P<0.001) than in the HSA (r=0.256, P<0.001). NSA, HSA, and MP tended to increase with increasing GMFCS level, and proportion of valgus deformed proximal femoral epiphysis also increased with increasing GMFCS level, which means valgus deformity and unstable hips in the less favorable functional states. Multiple regression analysis revealed NSA, GMFCS level, and shape of the proximal femoral epiphysis to be significant factors affecting MP. Conclusions NSA appeared to be more clinically relevant than HSA in evaluating proximal femoral deformity in patients with CP. Shape of proximal femoral epiphysis is believed to have clinical implications in terms of hip instability. Level of Evidence Diagnostic level II.

Parental satisfaction after single-event multilevel surgery in ambulatory children with cerebral palsy.

Background: The purpose of this study was to analyze parent satisfaction and factors affecting that satisfaction with single-event multilevel surgery outcomes in ambulatory children with cerebral palsy. Methods: Two hundred seventy-nine ambulatory patients with cerebral palsy were enrolled in this study. Parental satisfaction after surgery was evaluated using a visual analog scale (0-10), and the explanatory variables were collected by chart review. Results: Overall mean (SD) satisfaction after surgery was 7.9 (2.0), with mean follow-up of 6.6 years. The parents of patients classified asGross Motor Function Classification System (GMFCS) level I cerebral palsy were more satisfied than parents of patients classified as GMFCS level II or III cerebral palsy (P = 0.029). Surgical satisfaction was higher for unilaterally involved patients than for bilaterally involved ones (P < 0.001). Multiple regression revealed predictors ofsatisfaction to be preoperative GMFCS level, diagnosis, age at surgery, and duration of follow-up. Conclusions: We believe that this data can be used to help predict the level of parental satisfaction when planning single-event multilevel surgery in ambulatory children with cerebral palsy. Level of Evidence: Level II-Prognostic studies (investigating the effect of patient characteristic on the outcome of disease).