Flexion Measurements Research Articles

MEASURING GRAVITATIONAL LENSING FLEXION IN A1689 USING AN ANALYTIC IMAGE MODEL

Measuring dark matter substructure within galaxy cluster haloes is a fundamental probe of the Lambda-CDM model of structure formation. Gravitational lensing is a technique for measuring the total mass distribution which is independent of the nature of the gravitating matter, making it a vital tool for studying these dark-matter dominated objects. We present a new method for measuring weak gravitational lensing flexions, the gradients of the lensing shear field, to measure mass distributions on small angular scales. While previously published methods for measuring flexions focus on measuring derived properties of the lensed images, such as shapelet coefficients or surface brightness moments, our method instead fits a mass-sheet-transformation-invariant Analytic Image Model (AIM) to the each galaxy image. This simple parametric model traces the distortion of lensed image isophotes and constrains the flexion fields. We test the AIM method using simulated data images with realistic noise and a variety of unlensed image properties, and show that it successfully reproduces the input flexion fields. We also apply the AIM method for flexion measurement to Hubble Space Telescope observations of Abell 1689, and detect mass structure in the cluster using flexions measured with the AIM method.

Determining the Feasibility of Measuring Outdoor Road Cycling Kinematics Using Inertial Motion Capture Technology

Unlike traditional optical systems, inertial motion capture systems (IMSs) can measure human kinematics outdoors as well as in a laboratory. However, these systems are sensitive to magnetic interference. This study evaluated an IMS for use in sports performance analysis, using road cycling as a case study. The objective was to establish the feasibility of obtaining accurate outdoor kinematic data on competition-level road bicycles. Ten male cyclists were recorded on their own bicycle on a stretch of road wearing the IMS. Results revealed unacceptable magnetic interference to the IMS near the pedal and handlebar interfaces. Therefore, accurate full-body cycling kinematics is not currently feasible on most competition-level road bicycles. However, lower limb flexion measurements are possible using the IMS's kinematic coupling algorithm which obtained RMS errors of less than 3.5° for all joints in a benchmark test with an optical system regarded as gold-standard.

Probing galaxy dark matter haloes in COSMOS with weak lensing flexion

Current theories of structure formation predict specific density profiles of galaxy dark matter haloes, and with weak gravitational lensing we can probe these profiles on several scales. On small scales, higher-order shape distortions known as flexion add significant detail to the weak lensing measurements. We present here the first detection of a galaxy-galaxy flexion signal in space-based data, obtained using a new Shapelets pipeline introduced here. We combine this higher-order lensing signal with shear to constrain the average density profile of the galaxy lenses in the Hubble Space Telescope COSMOS survey. We also show that light from nearby bright objects can significantly affect flexion measurements. After correcting for the influence of lens light, we show that the inclusion of flexion provides tighter constraints on density profiles than does shear alone. Finally we find an average density profile consistent with an isothermal sphere.

Reproducibility of concentric isokinetic and isometric strength measurements at the hip in patients with hip osteoarthritis: A preliminary study

To determine the reproducibility of isokinetic and isometric hip flexion, extension, abduction and adduction strengt h scores in patients with hip osteoarthritis (N = 16) and healthy subjects, testing was conducted twice 7 days apart. The patient group (PG) consisted of 16 subjects with unilateral or bilat eral osteoarthritis of the hip (11 women, 5 men; age 56-75y). The control group (CG) included 13 age-matched healthy subjects (9 women, 4 men; age 54-73y). The standard error of measurement (SEM) served as the reproducibility outcome parameter. The highest SEM values were obtained for hip extension measurements (15.4-16.7 Nm), followed by hip adduction (7.9-11.8 Nm) and hip flexion measurements (5.2-7.5 Nm). The smallest values were quantified for hip abduction measurements (4.7-7 .7 Nm). PG showed larger values in all isometric measures except for hip extension and isokinetic hip abduction. When the 95% confidence interval is incorporated, these SEMs become sign ificant. Thus clinicians should be aware of the large measurement error in patients with hip OA. Adequate preparations and firm fixa tion of the pelvis are key elements to achieve reproducible results.

歩行訓練と下肢筋力トレーニングに伴う下腿義足歩行動作改善の 1 例

In order to examine the process of improvement in the walking ability of trans-tibia amputees fitted with lower-limb prostheses, this study carried out tests of free walking and fast walking movements in a man with a TSB trans-tibia prosthesis. The tests included measurements of hip flexion in a sitting position, walking speed, step length, step rate, supporting time and swing time. The measurements were carried out every two weeks, for a total of six times. Furthermore, in order to examine the connection between the subject's walking ability and his training programs, investigative records of the subject's muscle strengthening and rehabilitation with walking were also examined. The results showed that there were continuous improvements of muscle strength in both legs as a result of muscle training and rehabilitation during 11 weeks. An obvious improvement of walking ability was observed two weeks after the start of walking as muscle strength increased, and the differences between the two legs evident at the initial stage slowly decreased. This bilateral difference showed a conspicuous improvement from about the seventh week, and perfectly normal walking was achieved from the 11th week. However, these results need to be interpreted with caution because this was a case study involving only one subject with a lower-limb prosthesis, and was not a case in which the socket of the artificial leg had considerable non-conformity.

Novel methods for 3D postoperative analysis of total knee arthroplasty using 2D–3D image registration

Background Radiographic evaluation of patients after total knee arthroplasty is an important tool for assessing the correct position of the implants and the axis of limb alignment because this will determine long-term durability of the implants. Recently, 2D–3D medical image registration methods are developed for 3D postoperative analysis of total knee arthroplasty. However, most of these techniques have focused only on knee implants. Methods A 2D–3D medical image registration is implemented to compute the 3D positions of not only implants but also lower limb bones. The following 3D postoperative analysis methods for total knee arthroplasty are presented in this paper: (1) automatic calculation of relative angles of implants and bones, (2) assessment of external rotation angles of inserted implants, and (3) measurement and comparison of both flexion–extension gap balances. Finally these methods have been applied in five patients who underwent total knee replacements. Findings A practical method that can evaluate the patient's knee conditions has been successfully developed. The repeatability and accuracy of 2D–3D registration were around 0.2 mm as obtained from the tests using model bones. Based on the 3D information, the novel methods of postoperative analysis were proposed and successfully applied to the patients. Interpretation The 3D positions for both knee implants and lower limb bones can be calculated in order to perform comprehensive postoperative analyses of total knee arthroplasty. The proposed analyses of the postoperative evaluations facilitated various 3D evaluations of the status of implants, alignment of lower limb and gap balances which were not previously feasible.

A randomised controlled trial investigating the effect of posterior capsular stripping on knee flexion and range of motion in patients undergoing primary knee arthroplasty

Increasing knee flexion following total knee arthroplasty (TKA) has become an important outcome measure. Surgical technique is one factor that can influence knee motion. In this study, it was hypothesised that stripping of the posterior knee capsule could improve flexion and range of motion (ROM) following TKA. Patients who were undergoing TKA were prospectively randomised into two groups — one group (62 patients) were allocated stripping of the posterior knee capsule (PCS), the other group (66 patients) no stripping (no-PCS). The primary outcome was change in flexion and ROM compared to pre-operative measurements at three time points; after wound closure, 3 months and 1 year post-operatively. Secondary outcomes were absolute measurements of flexion, extension, ROM and complications. All operations were performed by a single surgeon using the same implant and technique. All patients received identical post-operative rehabilitation. There was a significant gain in flexion after wound closure in the PCS group ( p = 0.022), however there was no significant difference at 3 months or 1 year post-operatively. Absolute values of extension ( p = 0.008) and flexion ( p = 0.001) 3 months post-operatively were significantly reduced for the PCS group. The absolute value of ROM was significantly higher for the no-PCS group at 3 months ( p = 0.0002) and 1 year ( p = 0.005).There were no significant difference in the rate of complications. Posterior capsular stripping causes a transient increase in flexion that does not persist post-operatively. We do not recommend routine stripping of the posterior knee capsule in patients undergoing TKA.

WEAK LENSING MASS RECONSTRUCTION: FLEXION VERSUS SHEAR

Weak gravitational lensing has proven to be a powerful tool to map directly the distribution of dark matter in the Universe. The technique, currently used, relies on the accurate measurement of the gravitational shear that corresponds to the first-order distortion of the background galaxy images. More recently, a new technique has been introduced that relies on the accurate measurement of the gravitational flexion that corresponds to the second-order distortion of the background galaxy images. This technique should probe structures on smaller scales than that of a shear analysis. The goal of this paper is to compare the ability of shear and flexion to reconstruct the dark matter distribution by taking into account the dispersion in shear and flexion measurements. Our results show that the flexion is less sensitive than shear for constructing the convergence maps on scales that are physically feasible for mapping, meaning that flexion alone not be used to do convergence map reconstruction, even on small scales.

Corticosteroids as an Adjunct to Antibiotics and Surgical Drainage for the Treatment of Pyogenic Flexor Tenosynovitis

Many similarities exist between pyogenic flexor tenosynovitis and other closed-space infections such as septic arthritis. Previous studies have demonstrated that corticosteroids in conjunction with antibiotics considerably improve treatment outcomes in patients with septic arthritis. Using a chicken model, we investigated whether or not corticosteroids in combination with antibiotics and/or surgical drainage could minimize the loss of range of motion typically associated with pyogenic flexor tenosynovitis. We inoculated the flexor tendon sheath of the right long toe of broiler chickens with Staphylococcus aureus (American Type Culture Collection 29523 NA) (6 × 10(9) colony-forming units/mL) and twenty-four hours later administered one of six treatments to groups of fourteen or fifteen chickens. Treatment combinations included systemic or intrasynovial antibiotics, surgical drainage with catheter irrigation or no surgical drainage, and local corticosteroid injections or no corticosteroid injections. Measurements of active digital flexion at the proximal and middle interphalangeal joints were performed before inoculation and treatment and at seven, fourteen, and twenty-eight days after treatment. Flexion measurements were compared between groups as well as with similar measurements in the contralateral, uninfected, control long toe. At twenty-eight days, two of three groups treated with locally administered corticosteroids and the group treated with intrasynovial antibiotics alone (without surgery) regained significantly more active flexion in comparison with chickens treated with systemic antibiotics and surgical drainage (the current standard of care). Pooled data revealed that the corticosteroid-treated groups regained significantly more active flexion at all post-treatment time points. Our data support the hypothesis that adding locally administered corticosteroids to the treatment regimen for pyogenic flexor tenosynovitis in a chicken model can significantly decrease loss of motion resulting from the infection. Furthermore, locally administered antibiotics may be effective for the treatment of pyogenic flexor tenosynovitis.

A MOBILE COMPUTING TOOL FOR COLLECTING CLINICAL OUTCOMES DATA FROM SHOULDER PATIENTS

The collection of outcomes data is critical for conducting clinical studies in orthopaedic surgery. Both subjective outcome data [e.g. Short Form-12 (SF-12) and Western Ontario Rotator Cuff (WORC) index] and objective data (e.g. range of motion) are necessary. Numerous studies have been conducted on the collection of patient survey data through electronic means (e.g. personal digital assistant and tablet PC), but none of these studies have made use of a device with an intuitive touch-screen interface. Studies have also been conducted on the collection of physical examination data through research-grade accelerometers but few have focused on the use of commercially available electronic devices. The goal of our project was to develop a mobile computing touch-screen system for capturing subjective and objective outcome data for the assessment of patients with rotator cuff tears. We were able to accomplish this goal through the development of a novel iPad/iPod Touch tool. Intra-rater and inter-rater reliability of shoulder flexion and external rotation measurements were good.

Measurement of the Extreme Ankle Range of Motion Required by Female Ballet Dancers

Female ballet dancers require extreme ankle motion, especially plantar flexion, but research about measuring such motion is lacking. The purposes of this study were to determine in a sample of ballet dancers whether non-weight-bearing ankle range of motion is significantly different from the weight-bearing equivalent and whether inclinometric plantar flexion measurement is a suitable substitute for standard plantar flexion goniometry. Fifteen female ballet dancers (5 university, 5 vocational, and 5 professional dancers; age 21 ± 3.0 years) volunteered. Subjects received 5 assessments on 1 ankle: non-weight-bearing goniometry dorsiflexion (NDF) and plantar flexion (NPF), weight-bearing goniometry in the ballet positions demi-plié (WDF) and en pointe (WPF), and non-weight-bearing plantar flexion inclinometry (IPF). Mean NDF was significantly lower than WDF (17° ± 1.3° vs 30° ± 1.8°, P < .001). NPF (77° ± 2.5°) was significantly lower than both WPF (83° ± 2.2°, P = .01) and IPF (89° ± 1.6°, P < .001), and WPF was significantly lower than IPF (P = .013). Dorsiflexion tended to decrease and plantar flexion tended to increase with increasing ballet proficiency. The authors conclude that assessment of extreme ankle motion in female ballet dancers is challenging, and goniometry and inclinometry appear to measure plantar flexion differently.

One-year prognosis in sick-listed low back pain patients with and without radiculopathy. Prognostic factors influencing pain and disability

Background context Previous research has documented various psychosocial risk factors with influence on outcome in low back pain (LBP) patients, but the value of clinical predictors has been less well documented. Purpose To identify clinical and psychosocial risk factors at baseline influencing disability and pain at 1 year in LBP patients sick-listed 3 to 16 weeks, and to look for differences between nonspecific LBP and radiculopathy. Study design Cohort study with 1-year follow-up based on a randomized clinical trial. Outcome measures Disability and change of disability, pain and change in pain at 1 year. Methods In a randomized clinical study evaluating multidisciplinary versus brief intervention, 325 patients were followed for 1 year. At baseline, they completed a questionnaire and went through a clinical low back examination, including measure of forward flexion and side flexion as well as tender point examination, a method to estimate diffuse tenderness. Furthermore, degenerative changes on plain X-rays of the lumbar spine were quantified, and sciatica was investigated by magnetic resonance imaging. Results Radiculopathy was verified by magnetic resonance imaging in 111 (34%) patients. At 1 year, questions of disability in daily life activities and pain were answered by 60% and 67%, respectively. The intensity of back+leg pain and disability was closely correlated. Statistically significant predictors for both disability and back+leg pain at 1 year were intensity of back+leg pain, worrying and health anxiety, many tender points, and little or moderate exercise in leisure time. Two additional risk factors were identified in patients with radiculopathy: older age and “drinking alcohol less than once per month.” Furthermore, disability at 1 year was associated with initial disability and compensation claim, and back+leg pain at 1 year was associated with fear avoidance about physical activity and the duration of pain. Change in disability was more closely associated with return to work than change in pain. Disc degeneration was not associated with disability or pain at 1 year. General health was not statistically significantly associated with outcome when adjusted for back+leg pain, disability, and worrying and health anxiety. Conclusions Disability and pain at 1 year were associated with baseline disability and pain, diffuse tenderness, worrying and health anxiety, compensation claim, fear avoidance, and baseline exercise habits. Only in patients with verified nerve root affection, older age, and restrained alcohol seemed to play a role. The multivariate models were insufficient in predicting disability and pain, partly because disability and pain were also strongly associated with return to work.

Delensing gravitational wave standard sirens with shear and flexion maps

Supermassive black hole binary systems (SMBHB) are standard sirens -- the gravitational wave analogue of standard candles -- and if discovered by gravitational wave detectors, they could be used as precise distance indicators. Unfortunately, gravitational lensing will randomly magnify SMBHB signals, seriously degrading any distance measurements. Using a weak lensing map of the SMBHB line of sight, we can estimate its magnification and thereby remove some uncertainty in its distance, a procedure we call "delensing." We find that delensing is significantly improved when galaxy shears are combined with flexion measurements, which reduce small-scale noise in reconstructed magnification maps. Under a Gaussian approximation, we estimate that delensing with a 2D mosaic image from an Extremely Large Telescope (ELT) could reduce distance errors by about 30-40% for a SMBHB at z=2. Including an additional wide shear map from a space survey telescope could reduce distance errors by 50%. Such improvement would make SMBHBs considerably more valuable as cosmological distance probes or as a fully independent check on existing probes.

Is low-level laser therapy effective in acute or chronic low back pain?

The purpose of this study was to compare the effectiveness of low-level laser therapy (LLLT) on pain and functional capacity in patients with acute and chronic low back pain caused by lumbar disk herniation (LDH). LLLT has been used to treat acute and chronic pain of musculoskeletal system disorders. This study is a randomized, double-blind, placebo-controlled study. Forty patients with acute (26 females/14 males) and 40 patients with chronic (20 females/20 males) low back pain caused by LDH were included in the study. Patients were randomly allocated into four groups. Group 1 (acute LDH, n = 20) received hot-pack + laser therapy; group 2 (chronic LDH, n = 20) received hot-pack + laser therapy; group 3 (acute LDH, n = 20) received hot-pack + placebo laser therapy, and group 4 (chronic LDH, n = 20) received hot-pack + placebo laser therapy, for 15 sessions during 3 weeks. Assessment parameters included pain, patients' global assessment, physician's global assessment, and functional capacity. Pain was evaluated by visual analog scale (VAS). [corrected] Patients' and physician's global assessment were also measured with VAS. Modified Schober test and flexion and lateral flexion measures were used in the evaluation of range of motion (ROM) of lumbar spine. Roland Disability Questionnaire (RDQ) and Modified Oswestry Disability Questionnaire (MODQ) were used in the functional evaluation. Measurements were done before and after 3 weeks of treatment. After the treatment, there were statistically significant improvements in pain severity, patients' and physician's global assessment, ROM, RDQ scores, and MODQ scores in all groups (p < 0.05). However, no significant differences were detected between four treatment groups with respect to all outcome parameters (p > 0.05). There were no differences between laser and placebo laser treatments on pain severity and functional capacity in patients with acute and chronic low back pain caused by LDH.

Comparative study of intraoperative knee flexion with three different TKR designs

Substantial flexion after total knee arthroplasty (TKA) is required for certain categories of patients who wish to squat or kneel in their daily life. Many factors influence this postoperative flexion, including the prosthesis design. It is therefore valuable to in vivo analyze these factors on three knee prosthesis designs through a study of their intraoperative flexion. The posterior-stabilized (PS) knee prostheses provide better intraoperative flexion than the ultracongruent (UC) model. Of the currently available PS models, the high-flexion ones have better intraoperative flexion than standard models. Our main focus endpoint was the intraoperative flexion achieved, before soft-tissues closure, during TKA surgical procedure. This was a controlled study. Seventy-two osteoarthritic knees requiring TKA were included to compare three selected prosthesis models: the SAL ultracongruent and two PS models (the standard LPS and the LPS Flex). This was a single-operator study, with patients divided into three homogenous, comparable groups, in which intraoperative measurement of flexion was performed using computer-assisted navigation. Statistical analysis allowed comparison of the three models. Intraoperatively, after prosthesis implantation, before soft-tissues closure, the mean flexion of the LPS-Flex was 134 degrees versus 124 degrees for the SAL (p=0.0004); the mean flexion of the standard LPS model was 130 degrees versus 124 degrees for the SAL (p=0.14); the PS Flex model showed no significant difference (p=0.26) in flexion (134 degrees) compared to the standard model (130 degrees). The SAL ultracongruent model seemed to be a factor reducing the intraoperative flexion by 8 degrees compared to the PS models (p<10(-4)). In this study, the PS designs (standard or Flex) provided better intraoperative flexion than the SAL ultracongruent design. However, the LPS Prosthesis did not demonstrate superiority over the standard LPS Prosthesis. Level III, low-power prospective study.

Muscle Strength and Body Size and Later Cerebrovascular and Coronary Heart Disease

To investigate the associations between muscle strength, relative weight, and stature in young adulthood with later coronary heart disease (CHD) and stroke incidence. Cohort study. Baseline data were drawn from the Swedish Military Service Conscription Register from the records of 1969 to 1994. At baseline, male Swedish citizens born between 1951 and 1976 (median age, 18.2 y) attended a mandatory conscription examination from which the only grounds for exemption were a severe handicap or a chronic disease. Full data sets with blood pressure in the acceptable range [diastolic (DBP), 40-100 mm Hg and systolic (SBP), 100-180 mm Hg] were available for 1 145 467 men (99%). The conscription examination included measurements of elbow flexion, hand grip, and knee extension strength; DBP and SBP, and height and weight for calculation of body mass index (BMI). Data on education and socioeconomic status were derived from censuses conducted every decade. The main outcome measures were fatal and nonfatal CHD events and hemorrhagic and ischemic strokes in relation to strength, BMI, and height. Follow-up data were collected from 1969 to 2006 from the Swedish Cause of Death Register, Swedish Hospital Discharge Register, and Statistics Sweden's Emigration Register. Follow-up time was counted from conscription examination to death or hospitalization (median follow-up time, 24.4 y). Standardized hazard ratios (HR) were calculated for a 1-SD increase in the exposure variables. During the follow-up period 12 323 CHD and 8865 stroke cases occurred. After adjustment for other risk factors, strength indicators were inversely associated with CHD and all strokes (HR for CHD: elbow flexion strength, 0.95; 95% confidence interval [CI], 0.93-0.97; grip strength, 0.89; 95% CI, 0.88-0.91; knee extension strength, 0.92; 95% CI, 0.90-0.94; and HR for stroke: elbow flexion strength, 0.96; 95% CI, 0.94-0.99; grip strength, 0.95; 95% CI, 0.93-0.97; knee extension strength, 0.93; 95% CI, 0.90-0.95). Greater grip strength predicted a lower risk of intracerebral infarction (HR, 0.91; 95% CI, 0.88-0.95) and greater knee extension strength predicted a lower risk of intracerebral and subarachnoid hemorrhagic stroke (HR, 0.88; 95% CI, 0.82-0.93 and HR, 0.92, 95% CI, 0.86-0.99, respectively). Risk of CHD and intracerebral infarction increased progressively with increasing BMI, whereas both very low BMI and overweight were associated with intracerebral and subarachnoid hemorrhagic stroke. Tallness was positively associated with lower rates of CHD and stroke. Muscle strength was inversely associated with risk of fatal and nonfatal coronary heart disease and stroke, independently of associations of BMI and stature with mortality and morbidity, during 24 years of follow-up of men on Swedish conscription rolls.

A new tool to determine masses and mass profiles using gravitational flexion

In a recent publication, an aperture mass statistic for gravitational flexion was derived and shown to be effective, at least with simulated data, in detecting massive structures and substructures within clusters of galaxies. Further, it was suggested that the radius at which the flexion aperture mass signal falls to zero might allow for estimation of the mass or density profile of the structures detected. In this paper, we more fully explore this possibility, considering the behaviour both of the peak signal and the zero-signal contours for two mass models--the singular isothermal sphere and Navarro-Frenk-White profiles--under varying aperture size, filter shape and mass concentration parameter. We demonstrate the effectiveness of the flexion aperture mass statistic in discriminating between mass profiles and concentration parameters, and in providing an accurate estimate of the mass of the lens, to within a factor of 1.5 or better. In addition, we compare the aperture mass method to a direct nonparametric reconstruction of the convergence from flexion measurements. We demonstrate that the aperture mass technique is much better able to constrain the shape of the central density profile, obtains much finer angular resolution in reconstructions, and does not suffer from ambiguity in the normalisation of the signal, in contrast to the direct method.

高速動作からみた下肢の動的安定性

The purpose of this study is to evaluate the stability of the lower limbers during high speed motion. The tests included analysis of motion in 15-second stationary stepping motions and muscle strength measurements of the hip flexion in a sitting position. The motions of 80 subjects ranging from a teenager to an elderly person were videotaped with a video camera operating at 60 Hz. The stability was evaluated by the change of coefficient of variation of the knee during the stepping motion. The coefficient of variation was calculated on the ratio of the standard deviation to the mean of peak height values the knee joint reached at each step. The result showed that a sexual distinction of stability exists in the teenaged and middle-aged group, being less stable in the female teenaged group and male middle-aged group. Stability of motion and muscle strength were not influenced by aging and muscle strength from the age of 12 to 70. Stability of motion and muscle strength showed a tendency of decline from the age of 70 in both males and females. The decline of muscle strength had an influence on the stability of motion in elderly, having reduced stability from less than 17kg in males and less than 9 kg in females. The decline of stability of motion may be an important factor explaining the fall risk of elderly during fast walking or running.

Helical axis calculation based on Burmester theory: experimental comparison with traditional techniques for human tibiotalar joint motion

In prosthetics and orthotics design, it is sometimes necessary to approximate the multiaxial motion of several human joints to a simple rotation about a single fixed axis. A new technique for the calculation of this axis is proposed, originally based on Burmester's theory. This was compared with traditional approaches based on the mean and finite helical axes. The three techniques were assessed by relevant optimal axis estimation in in vitro measurements of tibiotalar joint motion. A standard jig and radiostereometry were used in two anatomical specimens to obtain accurate measurements of joint flexion. The performance of each technique was determined by comparing the motion based on the resulting axis with the experimental data. Random noise with magnitude typically similar to that of the skin motion was also added to the measured motion. All three techniques performed well in identifying a single rotation axis for tibiotalar joint motion. Burmester's theory provides an additional method for human joint motion analysis, which is particularly robust when experimental data are considerably error affected.

Assessment of tibiofemoral position in total knee arthroplasty using the active flexion lateral radiograph

This study is a retrospective comparative cohort radiographic analysis of 114 consecutive patients who underwent posterior cruciate retaining (PCR) total knee arthroplasty (TKA), medial and patellofemoral compartment bicruciate retaining arthroplasty (BCR), or bicruciate substituting (BCS) TKA. In an effort to obtain a quantitative measurement of both anteroposterior (AP) tibiofemoral position and active knee flexion we have routinely taken post-operative lateral radiographs in a position of maximal active flexion. Passive range of motion (PRoM) after TKA was significantly greater than pre-operative passive range of motion for each cohort ( p < 0.001). When comparing post-operative active range of motion (ARoM) to PRoM, there was a statistically significant difference within the PCR and BCR cohorts ( p < 0.001 and p < 0.005, respectively), while none was detected in the BCS group ( p = 0.09). The mean rollback of PCR was − 1.2 mm, BCR was − 3.3 mm and BCS was − 12.0 mm. The mean rollback of all three groups was similar to measurements reported from previous fluoroscopic historical control data. Our findings indicate that tibiofemoral AP translation during knee flexion can be assessed on an active flexion lateral knee radiograph and provide additional information that is not available from a routine lateral radiograph.