Chen-Kun Liaw

A new tool for measuring cup orientation in total hip arthroplasties from plain radiographs.

Orientation of the hip cup is important in total hip arthroplasties. Orientation includes abduction (inclination) and anteversion. Anteversion can be considered as true (anatomic) and planar (radiographic) anteversion. Some measurement methods either are too complicated or are less precise. We developed a new protractor to measure cup orientation using postoperative anteroposterior radiographs centered at the hip. The new protractor measures true and planar anteversion and abduction easily and precisely. We verified its accuracy using a software simulator and simulated 45 radio- graphs of total hip arthroplasties with 15 different anteversions ranging from 15°-29° and 45 actual radiographs of total hip arthroplasties. We then measured the planar ante- version with our method and the method of Lewinnek et al. Maximal errors were 3° and 2.61°, respectively, and mean errors were 0.96° and 1.2°, respectively. The standard deviations were 0.74° with our method and 0.57° with the method of Lewinnek et al. For the real radiographs, the mean of absolute difference between the two methods was 1.34°, and the standard deviation was 1.13°. We found no difference between the two methods and no difference in our findings compared with those of Pradhan.Level of Evidence: Diagnostic study, level II.

Risk factors for single and recurrent falls: a prospective study of falls in community dwelling seniors without cognitive impairment.

OBJECTIVE The purpose of this study is to contribute evidence towards heterogeneity in risk factors for single and recurrent falls. METHOD This is a prospective study conducted in Taiwan. Participants were randomly selected from the examinees of the annual health examination in 2010. Participants were interviewed with a detailed questionnaire and followed up one year later. Predictor variables included socio-demographic characteristics, medical conditions, laboratory data, and risk factors for osteoporosis. The outcome was falls in the ensuing 12 months. RESULTS The mean age of the 653 completers was 75.6 ± 6.4. Half (48.7%) were women. Fallers and recurrent fallers comprised 14.5% and 6.0% of the participants, respectively. Blurred vision (adjusted odds ratio (aOR): 1.93, 95% confidence interval (CI): 1.02-3.67), minimal outdoor activities (aOR: 2.28, 95% CI: 1.06-4.88), and overactive thyroid/parathyroid (aOR: 3.49, 95% CI: 1.29-9.50) were associated with single falls. Frailty (aOR: 2.81, 95% CI: 1.11-7.09), decreased body height (aOR: 3.15, 95% CI: 1.52-6.54) and taking sedatives/hypnotics (aOR: 4.23, 95% CI: 2.06-8.67) were associated with recurrent falls. Previous falls (aOR: 2.64, 95% CI: 1.44-4.84 for single falls; aOR: 5.26, 95% CI: 2.61-10.60 for recurrent falls) were associated with all falls. CONCLUSION Different intervention strategies should be developed for single and recurrent fallers.

Measurement of the acetabular cup anteversion on simulated radiographs.

Widmer (J Arthroplasty 2004;19:387) reported a protractor for measuring the anteversion of acetabular cups on radiographs but with limited precision. We intended to improve its precision by trigonometric mathematics. We measured the anteversion of the acetabular cups on 336 simulated radiographs using aforementioned 2 methods. The anteversion measured by Widmers protractor ranged from 7 degrees to 41 degrees (mean +/- SD = 28.0 degrees +/- 9.8 degrees), and our methods, 5 degrees to 51 degrees (27.7 degrees +/- 13.2 degrees). The mean +/- SD of error by Widmers protractor was 5.2 +/- 2.5 degrees, and our protractor, 0.8 degrees +/- 0.8 degrees (Student t test, P b .0001). The interobserver study showed the difference between measurements less than 2 degrees for each method. Therefore, the smaller error of our method than that of Widmer implicated a potentially precise measurement of the anteversion (level of evidence: diagnostic study, level II).

Image changes of paraspinal muscles and clinical correlations in patients with unilateral lumbar spinal stenosis

Study designThis is a retrospective study.PurposeTo compare the morphometric parameters of the psoas major and lumbar multifidus muscles in lumbar spinal stenosis (LSS) patients exhibiting different functional performance.Summary of background dataLSS refers to symptoms related to size reduction of the lumbar spinal canal; however, the degree of stenosis is poorly related to symptom severity and functional impairments. Morphometric changes in the paraspinal muscles have been correlated with chronic lower back pain in previous studies. However, correlations between the functional performance of LSS patients and the morphometric changes in paraspinal muscles have seldom been reported.MethodsSixty-six LSS patients without mechanical back pain or segmental instability were enrolled in the study. A review of their medical records and MRI images was performed. Morphometric parameters, including the fatty infiltration (FI) of the lumbar multifidus muscle as well as the relative cross-sectional area (RCSA) of the psoas major and lumbar multifidus muscles, were measured. Subjects were divided into high and low functional performance groups according to their Japanese Orthopedic Association (JOA) scores.ResultsThe male LSS patients exhibited a larger psoas RCSA than the female patients, whereas the older patients exhibited a smaller psoas RCSA and higher multifidus FI than the younger patients. LSS patients in the high functional performance group exhibited a significantly larger psoas RCSA and lower multifidus FI.ConclusionThe psoas RCSA and multifidus FI can be used as predictive factors for functional performance in LSS patients.

A simple mathematical standardized measurement of acetabulum anteversion after total hip arthroplasty

We invented a standardization method to measure the cup’s anteversion after total hip arthroplasty without the influence of patient’s position. We measured 68 radiographs of 10 patients after total hip replacement (THR) and calculated the error of each measurement, defined as the difference with the average of the same measuring method on the same patient. We also calculated the repeatability standard deviation (RSD) of each method according to the American Society for Testing and Materials, ASTM E691. Mean absolute inter-examination angle error, defined as the average of the absolute deviations, was 0.758 for standardized anteversion (range 0.03– 2.518), as compared with those without standardization, 2.308 (range 0.04 – 13.048). The inter-examination measurement reliability (precision), defined as one RSD, was 0.998 for standardized anteversion, as compared with those without standarization, 3.508. There is no difference between patients four and five without (p ¼ 0.097). There is a significant difference with standardization (p , 0.0001). Our study demonstrated that this mathematical method is a precise tool to measure the anteversion of the acetabular cup. We hope that it can be used widely in the future.

Biomechanical analyses of static and dynamic fixation techniques of retrograde interlocking femoral nailing using nonlinear finite element methods.

Femoral shaft fractures can be treated using retrograde interlocking nailing systems; however, fracture nonunion still occurs. Dynamic fixation techniques, which remove either the proximal or distal locking screws, have been used to solve the problem of nonunion. In addition, a surgical rule for dynamic fixation techniques has been defined based on past clinical reports. However, the biomechanical performance of the retrograde interlocking nailing systems with either the traditional static fixation technique or the dynamic fixation techniques has not been investigated by using nonlinear numerical modeling. Three-dimensional nonlinear finite element models were developed, and the implant strength, fixation stability, and contact area of the fracture surfaces were evaluated. Three types of femoral shaft fractures (a proximal femoral shaft fracture, a middle femoral shaft fracture, and a distal femoral shaft fracture) fixed by three fixation techniques (insertion of all the locking screws, removal of the proximal locking screws, or removal of the distal locking screws) were analyzed. The results showed that the static fixation technique resulted in sufficient fixation stability and that the dynamic fixation techniques decreased the failure risk of the implant and produced a larger contact area of the fracture surfaces. The outcomes of the current study could assist orthopedic surgeons in comprehending the biomechanical performances of both static and dynamic fixation techniques. In addition, the surgeons could also select a fixation technique based on the specific patient situation using the numerical outcomes of this study.

Comparison of the bending performance of solid and cannulated spinal pedicle screws using finite element analyses and biomechanical tests.

Spinal pedicle screw fixations have been used extensively to treat fracture, tumor, infection, or degeneration of the spine. Cannulated spinal pedicle screws with bone cement augmentation might be a useful method to ameliorate screw loosening. However, cannulated spinal pedicle screws might also increase the risk of screw breakage. Thus, the purpose of this study was to investigate the bending performance of different spinal pedicle screws with either solid design or cannulated design. Three-dimensional finite element models, which consisted of the spinal pedicle screw and the screws hosting material, were first constructed. Next, monotonic and cyclic cantilever bending tests were both applied to validate the results of the finite element analyses. Finally, both the numerical and experimental approaches were evaluated and compared. The results indicated that the cylindrical spinal pedicle screws with a cannulated design had significantly poorer bending performance. In addition, conical spinal pedicle screws maintained the original bending performance, whether they were solid or of cannulated design. This study may provide useful recommendations to orthopedic surgeons before surgery, and it may also provide design rationales to biomechanical engineers during the development of spinal pedicle screws.

Association of quality of life with laboratory measurements and lifestyle factors in community dwelling older people in Taiwan

Objectives: Little is known about the influence of routine laboratory measurements and lifestyle factors on generic quality of life (QOL) at older ages. We aimed to study the relationship between generic QOL and laboratory measurements and lifestyle factors in community dwelling older Chinese people. Methods: We conducted a cross-sectional analysis. Six hundred and ninety nine elders were randomly selected from the examinees of the annual health examination in Taipei City, Taiwan. Blood, urine and stool of the participants were examined and lifestyle data were collected. Participants completed the CASP-19 (control, autonomy, self-realization, pleasure) questionnaire, a 19-item QOL scale. The relationship between QOL and laboratory results and lifestyle factors was explored, using multiple linear regression and profile analysis. Results: The mean age of the participants was 75.5 years (SD = 6.5), and 49.5% were female. Male gender standardized β coefficients (β = 0.122) and exercise habit (β = 0.170) were associated with a better QOL, whereas advanced age (β = −0.242), blurred vision (β = −0.143), depression (β = −0.125), central obesity (β = −0.093), anemia (β = −0.095), rheumatoid arthritis (β = −0.073), Parkinsonism (β = −0.079), malignancy (β = −0.086) and motorcycle riding (β = −0.086) were associated with a lower QOL. Profile analysis revealed that young–old males, social drinkers, regular exercisers and car drivers had the best QOL (all p < 0.001). Conclusion: Of the many laboratory measurements, only anemia was associated with the lower QOL. By contrast, several lifestyle factors, such as social drinking, exercise habit and car driving, were associated with better QOL, whereas abdominal obesity and motorcycle riding were associated with lower QOL.

THR Simulator – the software for generating radiographs of THR prosthesis

BackgroundMeasuring the orientation of acetabular cup after total hip arthroplasty is important for prognosis. The verification of these measurement methods will be easier and more feasible if we can synthesize prosthesis radiographs in each simulated condition. One reported method used an expensive mechanical device with an indeterminable precision. We thus develop a program, THR Simulator, to directly synthesize digital radiographs of prostheses for further analysis.Under Windows platform and using Borland C++ Builder programming tool, we developed the THR Simulator. We first built a mathematical model of acetabulum and femoral head. The data of the real dimension of prosthesis was adopted to generate the radiograph of hip prosthesis. Then with the ray tracing algorithm, we calculated the thickness each X-ray beam passed, and then transformed to grey scale by mapping function which was derived by fitting the exponential function from the phantom image. Finally we could generate a simulated radiograph for further analysis.ResultsUsing THR Simulator, the users can incorporate many parameters together for radiograph synthesis. These parameters include thickness, film size, tube distance, film distance, anteversion, abduction, upper wear, medial wear, and posterior wear. These parameters are adequate for any radiographic measurement research. This THR Simulator has been used in two studies, and the errors are within 2° for anteversion and 0.2 mm for wearing measurement.ConclusionWe design a program, THR Simulator that can synthesize prosthesis radiographs. Such a program can be applied in future studies for further analysis and validation of measurement of various parameters of pelvis after total hip arthroplasty.

Simultaneous bilateral sleeve fracture of the patellae in a preadolescent athlete.

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