Recurrent Neural Network Methods for Extracting Dynamic Balance Variables during Gait from a Single Inertial Measurement Unit.

Monitoring dynamic balance during gait is critical for fall prevention in the elderly. The current study aimed to develop recurrent neural network models for extracting balance variables from a single inertial measurement unit (IMU) placed on the sacrum during walking. Thirteen healthy young and thirteen healthy older adults wore the IMU during walking and the ground truth of the inclination angles (IA) of the center of pressure to the center of mass vector and their rates of changes (RCIA) were measured simultaneously. The IA, RCIA, and IMU data were used to train four models (uni-LSTM, bi-LSTM, uni-GRU, and bi-GRU), with 10% of the data reserved to evaluate the model errors in terms of the root-mean-squared errors (RMSEs) and percentage relative RMSEs (rRMSEs). Independent t-tests were used for between-group comparisons. The sensitivity, specificity, and Pearson's r for the effect sizes between the model-predicted data and experimental ground truth were also obtained. The bi-GRU with the weighted MSE model was found to have the highest prediction accuracy, computational efficiency, and the best ability in identifying statistical between-group differences when compared with the ground truth, which would be the best choice for the prolonged real-life monitoring of gait balance for fall risk management in the elderly.

Trend of serum C-reactive protein is associated with treatment outcome of hip Periprosthetic joint infection undergoing two-stage exchange arthroplasty: a case control study.

BACKGROUND: Serum C-reactive protein (CRP) trends are critical for monitoring patients' treatment response following a two-stage exchange arthroplasty for periprosthetic joint infection (PJI) of the hip. However, CRP trends are poorly described in the literature. The primary aim of this study was to identify the relationships between PJI treatment outcomes and our proposed CRP trend definitions, parameters, and microbiological data. The secondary aim was to investigate CRP trends after the occurrence of spacer-related complications. METHODS: We conducted a retrospective review of 74 patients treated with a two-stage exchange protocol for PJI in a tertiary referral joint center between 2014 and 2016. Patients with factors that may affect CRP levels (inflammatory arthritis, concomitant infections, liver and kidney diseases, and intensive care admissions) were excluded. CRP trends were categorized into five types and PJI treatment outcome was defined as "success" or "failure" according to the Delphi criteria. RESULTS: Treatment was successful in 67 patients and failed in 7 patients. Multivariate logistic regression analysis showed that type 5 CRP, defined as serum CRP fluctuation without normalization after first stage surgery (odds ratio [OR]: 17.4; 95% confidence interval [CI]: 2.3-129.7; p = 0.005), and methicillin-resistant Staphylococcus aureus (MRSA; OR: 14.5; 95% CI: 1.6-131.7; p = 0.018) were associated with treatment failure. Spacer-related complications occurred in 18 patients. Of these, 12 had elevated CRP levels at later follow-up, while six had no elevation in CRP levels. CONCLUSIONS: We found that MRSA infection and type 5 CRP were associated with PJI treatment failure.

Evaluation of a multibody kinematics optimization method for three-dimensional canine pelvic limb gait analysis.

BACKGROUND: Skin marker-based three-dimensional kinematic gait analysis were commonly used to assess the functional performance and movement biomechanics of the pelvic limb in dogs. Unfortunately, soft tissue artefact would compromise the accuracy of the reproduced pelvic limb kinematics. Multibody kinematics optimization framework was often employed to compensate the soft tissue artefact for a more accurate description of human joint kinematics, but its performance on the determination of canine pelvic limb skeletal kinematics has never been evaluated. This study aimed to evaluate a multibody kinematics optimization framework used for the determination of canine pelvic limb kinematics during gait by comparing its results to those obtained using computed tomography model-based fluoroscopy analysis. RESULTS: Eight clinically normal dogs were enrolled in the study. Fluoroscopy videos of the stifle joint and skin marker trajectories were acquired when the dogs walked on a treadmill. The pelvic limb kinematics were reconstructed through marker-based multibody kinematics optimization and single-body optimization. The reference kinematics data were derived via a model-based fluoroscopy analysis. The use of multibody kinematics optimization yielded a significantly more accurate estimation of flexion/extension of the hip and stifle joints than the use of single-body optimization. The accuracy of the joint model parameters and the weightings to individual markers both influenced the soft tissue artefact compensation capability. CONCLUSIONS: Multibody kinematics optimization designated for soft tissue artefact compensation was established and evaluated for its performance on canine gait analysis, which provided a further step in more accurately describing sagittal plane kinematics of the hip and stifle joints.

Geometrical analysis for assessing torsional alignment of humerus.

BACKGROUND: Compared to other types of surgeries, minimally invasive surgeries (MISs) of humeral shaft fractures are associated with less radial nerve injury, less soft tissue injury and higher union rate. However, malrotation often occurs in MISs when closed reduction methods are used. This study aims to define specific palpable landmarks to help surgeons determine the correct torsional angle and reduce the incidence of malrotation. METHODS: Twenty-eight normal humeral computed tomography scans were retrieved from our image database. One line was drawn through the vertices of the intertubercular sulcus of the humeral head in the coronal view, and another line was drawn through the longest axis between the medial and lateral condyles in the coronal view. The angle between these two lines was measured at least 3 times for each scan. RESULTS: The profile of the intertubercular sulcus tangent line of the humeral head and the axis of the distal humerus was identified as the most accurate method for assessing the precision of torsion during MIS for humeral shaft fractures. The transepicondylar axis line is more internally rotated than the intertubercular sulcus tangent line. The mean angle was measured to be 41.1 degrees. CONCLUSIONS: The axis of the distal humeral condyles is internally rotated by approximately 41.1 degrees compared with the intertubercular sulcus tangent line of the humeral head. Minimally invasive surgeries can be performed by using these palpable landmarks. The torsional deformities can be reduced with the proper angle adjustment without the need for fluoroscopy. It can also be used to treat unstable comminuted humeral fractures. LEVEL OF EVIDENCE: Retrospective Study, Diagnostic study, Level III.

Influence of extension stem length and diameter on clinical and radiographic outcomes of revision total knee arthroplasty.

BACKGROUND: Extension stems provide stability to revision total knee arthroplasty (RTKA). Little is known regarding the relationship between stem characteristics and RTKA stability. We aimed to identify the relationship between canal filling ratio (CFR) and aseptic loosening following RTKA. METHODS: We retrospectively reviewed demographics, radiographic parameters, and outcomes associated with RTKA performed between 2008 and 2013 in a tertiary hospital. The inclusion criteria were: revision for aseptic loosening, hybrid fixation, minor bone defect, Zimmer® LCCK prosthesis, and follow-up > 24 months. Using the modified Knee Society radiographic scoring system, radiographic prosthesis loosening was defined as a radiolucent line (RLL) score ≥ 9 on the femoral side or ≥ 10 on the tibial side. We utilized receiver operating characteristic (ROC) curve analysis to evaluate the cutoff value for stem length and diameter in terms of prosthesis loosening or not. Furthermore, CFR-related parameters were analyzed with logistic regression to clarify their relationships with prosthesis loosening. RESULTS: Prosthesis loosening was detected in 17 of 65 patients included. On logistic regression analysis, male sex and severity of the tibial bone defect were associated with loosening. On multivariate analysis, male sex and bone defect severity were associated with loosening on the femoral side, while malalignment was associated with loosening on the tibial side. Protective factors included femoral CFR > 0.85, CFR > 0.7 for > 2 cm, and CFR > 0.7 for > 4 cm, as well as tibial CFR > 0.85. CONCLUSIONS: To minimize loosening post-RTKA, femoral CFR > 0.7 for > 2 cm and tibial CFR > 0.85 are recommended. Risk factors may include male sex, bone defect severity, and malalignment.

The value of MR T2* measurements in normal and osteoarthritic knee cartilage: effects of age, sex, and location.

OBJECTIVES: Our aim was to investigate the role of age, sex, and location on MR T2* values of the knee cartilage in asymptomatic controls and patients with osteoarthritis (OA). METHODS: A total of 100 participants, including 40 with OA and 60 asymptomatic controls, were enrolled in this study. Patients with OA were compared to age- (≥ 41 years old) and sex-matched controls. Controls were divided by age (aged 21-40 years, 41-60, ≥ 61). T2* values were acquired using a T2*-weighted fast gradient-echo sequence and a 1.5-T MRI scanner. T2* values of the femoral and tibial cartilages at the weight-bearing areas were obtained for comparisons. RESULTS: The T2* values significantly increased with age and were significantly higher in the medial femoral cartilage (35.96 ± 4.06 and 31.85 ± 2.44 ms), medial tibial cartilage (30.95 ± 2.87 and 28.24 ± 1.74 ms), and lateral femoral cartilage (33.90 ± 3.15 and 31.51 ± 2.28 ms) in OA patients versus age- and sex-matched controls. Among OA patients, the T2* values for women exceed those in men in the medial femoral cartilage (37.59 ± 4.43 and 34.16 ± 2.63 ms) and medial tibial cartilage (32.17 ± 2.59 and 29.62 ± 2.53 ms; p < 0.01). Correlations were found between the Lequesne index and the T2* values for the medial femoral cartilage (r = 0.636, p < 0.001) and the medial tibial cartilage (r = 0.433, p = 0.005). CONCLUSION: Cartilage T2* values tend to increase with age and are useful in assessing cartilage degeneration in early OA. KEY POINTS: • Age, sex, and location have important effects on cartilage T2* values at the knee. • MR T2* measurements are useful toward assessing cartilage degeneration. • The medial femoral and tibial cartilage T2* values correlate well with disease severity.

Quantification of three-dimensional soft tissue artifacts in the canine hindlimb during passive stifle motion.

BACKGROUND: Three-dimensional joint kinematics during canine locomotion are commonly measured using skin marker-based stereophotogrammetry technologies. However, marker-related errors caused by the displacement of the skin surface relative to the underlying bones (i.e., soft tissue artifacts, STA) may affect the accuracy of the measurements and obscure clinically relevant information. Few studies have assessed STA in canine limbs during kinematic analysis. The magnitudes and patterns of the STA and their influence on kinematic analysis remain unclear. Therefore, the current study aims to quantify the in vivo STA of skin markers on the canine thigh and crus during passive joint motion. The stifle joints of ten dogs were passively extended while the skin markers were measured using a motion capture system, and skeletal kinematics were determined using a CT-to-fluoroscopic image registration method. RESULTS: The skin markers exhibited considerable STA relative to the underlying bones, with a peak amplitude of 27.4 mm for thigh markers and 28.7 mm for crus markers; however, the amplitudes and displacement directions at different attachment sites were inconsistent. The markers on the cranial thigh and lateral crus closer to the stifle joint had greater STA amplitudes in comparison to those of other markers. Most markers had STA with linear and quadratic patterns against the stifle flexion angles. These STA resulted in underestimated flexion angles but overestimated adduction and internal rotation when the stifle was flexed to greater than 90°. CONCLUSIONS: Marker displacements relative to the underlying bones were prominent in the cranial aspect of the thigh and the proximal-lateral aspect of the crus. The calculated stifle kinematic variables were also affected by the STA. These findings can provide a reference for marker selection in canine motion analysis for similar motion tasks and clarify the relationship between STA patterns and stifle kinematics; the results may therefore contribute to the development of STA models and compensation techniques for canine motion analysis.

Balance Control and Energetics of Powered Exoskeleton-Assisted Sit-to-Stand Movement in Individuals With Paraplegic Spinal Cord Injury.

OBJECTIVE: To quantify the effects of initial hip angle and angular hip velocity settings of a lower-limb wearable robotic exoskeleton (WRE) on the balance control and mechanical energy requirements in patients with paraplegic spinal cord injuries (SCIs) during WRE-assisted sit-to-stand (STS). DESIGN: Observational, cross-sectional study. SETTING: A university hospital gait laboratory with an 8-camera motion analysis system, 3 forceplates, a pair of instrumented crutches, and a WRE. PARTICIPANTS: Patients (N=12) with paraplegic SCI. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The inclination angle (IA) of the body's center of mass (COM) relative to the center of pressure (COP), and the rate of change of IA (RCIA) for balance control, and the mechanical energy and forward COM momentum before and after seat-off for energetics during WRE-assisted STS were compared between conditions with 2 initial hip angles (105° and 115°) and 3 initial hip angular velocities (800, 1000, 1200 rpm). RESULTS: No interactions between the main factors (ie, initial hip angle vs angular velocity) were found for any of the calculated variables. Greater initial hip angle helped the patients with SCI move the body forward with increased COM momentum but reduced RCIA (P<.05). With increasing initial angular hip velocity, the IA and RCIA after seat-off (P<.05) increased linearly while total mechanical energy reduced linearly (P<.05). CONCLUSIONS: The current results suggest that a greater initial hip angle with smaller initial angular velocity may provide a favorable compromise between momentum transfer and balance of the body for people with SCI during WRE-assisted STS. The current data will be helpful for improving the design and clinical use of the WRE.

Test-retest reliability of mandibular morphology measurements on cone-beam computed tomography-synthesized cephalograms with random head positioning errors.

BACKGROUND: Cephalometric radiography has been used for orthodontic and surgical treatment planning and assessment, and for quantifying mandibular growth. However, it remains unclear how head positioning errors and the level of examiner experience affect the reliability of such morphometric measurements. The current study aimed to bridge the gap by determining the intra-, inter-rater, and inter-session reliability of measurements of mandibular morphology with random head positioning errors as measured by a junior and a senior dentist. METHODS: Cone-beam computed tomography data of twelve mandibles were obtained with each rotated randomly away from the neutral position within the range of +3 and -3° along each of the anatomical axes to simulate six imaging trials. A synthetic cephalogram for each trial was obtained via a digitally reconstructed radiography (DRR) technique and eleven landmarks for twelve morphological parameters on the cephalogram were identified manually six times by a junior and a senior dentist. The procedure was repeated on another day within 5 days. Test-retest reliability was assessed in terms of an intra-class correlation coefficient (ICC) using a two-way mixed-effects model. RESULTS: Good to very good intra-rater (senior: ICC > 0.92; junior: ICC > 0.78), inter-rater (ICC > 0.70 for most parameters) and inter-session reliability (senior: ICC > 0.84; junior: ICC > 0.62) were found. Bland & Altman plots of inter-rater comparisons show that there were systematical biases between the examiners on most parameters, except for the distance between Gonion and Pogonion. CONCLUSIONS: The current results suggest that good to very good intra-rater, inter-rater and inter-session reliability can be achieved for most parameters with randomized head positioning errors; higher inter-session reliability can be achieved by more experienced examiners; and that long-term monitoring of mandibular growth based on cephalographic measurements should be made by the same more experienced examiner. The current DRR-based approach can be used to evaluate individual factors that affect the morphological measurements.

Effects of shoe heel height on the end-point and joint kinematics of the locomotor system when crossing obstacles of different heights.

High-heeled shoes increase the risk of falling during walking, especially in the presence of obstacles. The study aimed to compare the end-point (foot/shoe) trajectories and joint angles of the lower extremities in 12 healthy females crossing obstacles of different heights while barefoot and when wearing narrow-heeled shoes (heel heights: 3.9, 6.3 and 7.3 cm). During obstacle-crossing, young females in narrow-heeled shoes maintained the same leading toe-clearance as when barefoot, irrespective of the heel height, primarily through increased plantarflexion of the leading swing ankle. However, the shoe heel-clearance was significantly reduced when compared with barefoot, presumably related to the difficulty in precisely sensing the position of the shoe-heel tip. With an increasing obstacle height, the toe-clearance, heel-clearance and shoe heel-clearance were reduced linearly, indicating an increasing risk of tripping over the obstacle. The results will be helpful for the design and development of strategies to reduce the risk of falling when wearing narrow-heeled shoes. Practitioner Summary: Knowledge of the influence of narrow-heeled shoes and obstacles on lower limb joint and end-point kinematics helps in shoe design to address fall risks. Compared to barefoot, narrow-heeled shoes reduced shoe heel-clearances, which were further reduced linearly with increasing obstacle height, indicating an increasing risk of tripping over the obstacle.

Validity and reliability of ankle morphological measurements on computerized tomography-synthesized planar radiographs.

BACKGROUND: Clinical success of total ankle arthroplasty depends heavily on the available information on the morphology of the bones, often obtained from measurements on planar radiographs. The current study aimed to evaluate the intra-rater, inter-rater and inter-session reliability and the validity of radiograph-based measurements of ankle morphology, and to quantify the effects of examiner experience on these measurements. METHODS: Twenty-four fresh frozen ankle specimens were CT scanned, data of which were used to reconstruct 3D volumetric bone models for synthesizing 2D radiographs. Two orthopaedic surgeons with different levels of clinical experience identified twenty landmarks five times on each of the synthesized sagittal and coronal radiographs and repeated the test on a subsequent day within 5 days. The landmarks were used to calculate fourteen morphological parameters. The two-way mixed-effects (ICC3,1), two-way random-effects (ICC2,k) and two-way random-effects (ICC3,k) models were used, respectively, to assess the intra-rater, inter-rater and inter-session reliability of measurements. The validity of the measurements for each examiner was assessed by comparing them with gold standard values obtained from the 2D radiographs projected from the 3D volumetric models using Pearson's correlation analysis and Bland and Altman plots, and the differences were defined as the measurement errors. RESULTS: Most of the morphological parameters were of good to very good intra-rater, inter-session and inter-rater reliability for both examiners (ICC > 0.61). Experience appeared to affect the inter-rater and inter-session reliability, the senior examiner showing greater inter-session ICC values than the junior examiner. Most of the tibial parameters had moderate to excellent correlations with the corresponding gold standard values but were underestimated by both examiners, in contrast to most of the talar parameters that were overestimated and had only poor to fair correlations. CONCLUSIONS: Most of the morphological parameters of the ankle can be estimated from radiographs with good to very good intra-rater, inter-session and inter-rater reliability, for both clinically experienced and less experienced examiners. Clinical experience helped increase the reliability of repeated evaluations after a longer interval, such as in a follow-up assessment. It is suggested that critical clinical decisions based on repeated morphology measurements should be made by more experienced surgeons or after appropriate training.

Evaluation of three force-position hybrid control methods for a robot-based biological joint-testing system.

BACKGROUND: Robot-based joint-testing systems (RJTS) can be used to perform unconstrained laxity tests, measuring the stiffness of a degree of freedom (DOF) of the joint at a fixed flexion angle while allowing the other DOFs unconstrained movement. Previous studies using the force-position hybrid (FPH) control method proposed by Fujie et al. (J Biomech Eng 115(3):211-7, 1993) focused on anterior/posterior tests. Its convergence and applicability on other clinically relevant DOFs such as valgus/varus have not been demonstrated. The current s1tudy aimed to develop a 6-DOF RJTS using an industrial robot, to propose two new force-position hybrid control methods, and to evaluate the performance of the methods and FPH in controlling the RJTS for anterior/posterior and valgus/varus laxity tests of the knee joint. METHODS: An RJTS was developed using an industrial 6-DOF robot with a 6-component load-cell attached at the effector. The performances of FPH and two new control methods, namely force-position alternate control (FPA) and force-position hybrid control with force-moment control (FPHFM), for unconstrained anterior/posterior and valgus/varus laxity tests were evaluated and compared with traditional constrained tests (CT) in terms of the number of control iterations, total time and the constraining forces and moments. RESULTS: As opposed to CT, the other three control methods successfully reduced the constraining forces and moments for both anterior/posterior and valgus/varus tests, FPHFM being the best followed in order by FPA and FPH. FPHFM had root-mean-squared constraining forces and moments of less than 2.2 N and 0.09 Nm, respectively at 0° flexion, and 2.3 N and 0.14 Nm at 30° flexion. The corresponding values for FPH were 8.5 N and 0.33 Nm, and 11.5 N and 0.45 Nm, respectively. Given the same control parameters including the compliance matrix, FPHFM and FPA reduced the constraining loads of FPH at the expense of additional control iterations, and thus increased total time, FPA taking about 10 % longer than FPHFM. CONCLUSIONS: The FPHFM would be the best choice among the methods considered when longer total time is acceptable in the intended clinical applications. The current results will be useful for selecting a force-position hybrid control method for unconstrained laxity tests using an RJTS.

Modeling the Human Tibiofemoral Joint Using Ex Vivo Determined Compliance Matrices.

Several approaches have been used to devise a model of the human tibiofemoral joint for embedment in lower limb musculoskeletal models. However, no study has considered the use of cadaveric 6 × 6 compliance (or stiffness) matrices to model the tibiofemoral joint under normal or pathological conditions. The aim of this paper is to present a method to determine the compliance matrix of an ex vivo tibiofemoral joint for any given equilibrium pose. Experiments were carried out on a single ex vivo knee, first intact and, then, with the anterior cruciate ligament (ACL) transected. Controlled linear and angular displacements were imposed in single degree-of-freedom (DoF) tests to the specimen, and the resulting forces and moments were measured using an instrumented robotic arm. This was done starting from seven equilibrium poses characterized by the following flexion angles: 0 deg, 15 deg, 30 deg, 45 deg, 60 deg, 75 deg, and 90 deg. A compliance matrix for each of the selected equilibrium poses and for both the intact and ACL-deficient specimen was calculated. The matrix, embedding the experimental load-displacement relationship of the examined DoFs, was calculated using a linear least squares inversion based on a QR decomposition, assuming symmetric and positive-defined matrices. Single compliance matrix terms were in agreement with the literature. Results showed an overall increase of the compliance matrix terms due to the ACL transection (2.6 ratio for rotational terms at full extension) confirming its role in the joint stabilization. Validation experiments were carried out by performing a Lachman test (the tibia is pulled forward) under load control on both the intact and ACL-deficient knee and assessing the difference (error) between measured linear and angular displacements and those estimated using the appropriate compliance matrix. This error increased nonlinearly with respect to the values of the load. In particular, when an incremental posterior-anterior force up to 6 N was applied to the tibia of the intact specimen, the errors on the estimated linear and angular displacements were up to 0.6 mm and 1.5 deg, while for a force up to 18 N, the errors were 1.5 mm and 10.5 deg, respectively. In conclusion, the method used in this study may be a viable alternative to characterize the tibiofemoral load-dependent behavior in several applications.

Comparison of measurements of mandible growth using cone beam computed tomography and its synthesized cephalograms.

BACKGROUND: The current study aimed to compare the measurements of the mandible morphology using 3D cone beam computed tomography (CBCT) images with those using 2D CBCT-synthesized cephalograms; to quantify errors in measurements based on 2D synthesized cephalograms; and to clarify the effects such errors have on the description of the mandibular growth. METHODS: Mandibles of six miniature pigs were scanned monthly using CBCT over 12 months and the data were used to reconstruct the 3D bone models. Five anatomical landmarks were identified on each bone model, and the inter-marker distances and monthly distance changes were calculated and taken as the gold standard. Synthetic 2D cephalograms were also generated for each bone model using a digitally reconstructed radiography (DRR)-generation method. Errors in cephalogram measurements were determined as the differences between the calculated variables in cephalograms and the gold standard. The variations between cephalograms and the gold standard were also compared using paired t-tests. RESULTS: While the inter-marker distance increases varied among the marker pairs, all marker pairs increased their inter-marker distances gradually every month, reaching 50% of the total annual increases during the fourth and fifth months, and then slowing down in the subsequent months. The 2D measurements significantly underestimated most of the inter-marker distances throughout the monitoring period, in most of the monthly inter-marker distance changes during the first four months, and in the total growth (p < 0.05). CONCLUSIONS: Significant errors exist in the measurements using 2D synthesized cephalogram, underestimating the mandibular dimensions and their monthly changes in the early stages of growth, as well as the total annual growth. These results should be considered in dental treatment planning at the beginning of the treatment in order to control more precisely the treatment process and outcome.

Immediate efficacy of laterally wedged insoles with arch support on walking in persons with bilateral medial knee osteoarthritis.

OBJECTIVE: To investigate the immediate efficacy of laterally wedged insoles with arch support (LWAS) on gait in persons with bilateral medial knee osteoarthritis (OA). DESIGN: A prospective case-control intervention study. SETTING: A gait laboratory with a 6-camera motion analysis system and 2 forceplates. PARTICIPANTS: Fifteen women with bilateral medial knee OA and 15 healthy control subjects (N=30). INTERVENTIONS: LWAS. MAIN OUTCOME MEASURES: Subjective knee pain and objective biomechanical indices, namely, joint angles and moments in the frontal plane, frontal plane ground reaction force and lever arm, as well as medial/lateral center of mass and center of pressure during gait. RESULTS: When wearing the LWAS, knee pain during gait in persons with medial knee OA decreased (P=.01). Peak internal knee abductor moments were also reduced (P<.001) with increasing foot progression angles, laterally shifted center of pressure, and a shortened frontal plane lever arm (all P<.05). However, ankle invertor moments were increased (P<.05) when wearing the LWAS. CONCLUSIONS: Although peak internal knee abductor moment and knee pain were immediately reduced during gait when wearing the LWAS, increased ankle invertor moments were found, suggesting that the LWAS should be used with caution. Strengthening and monitoring the condition of the ankle invertor muscles may be necessary if the LWAS is used as an intervention for persons with bilateral medial knee OA.

Clinical outcomes following sublaminar-trimming laminoplasty for extensive lumbar canal stenosis.

PURPOSE: Current surgical approaches for treatment of lumbar canal stenosis are often associated with relatively high rates of reoperation and recurrent stenosis. We have developed a new approach for treatment of this condition: sublaminar-trimming laminoplasty. To describe the surgical approach of sublaminar-trimming laminoplasty and to assess associated outcomes. METHODS: Patients with extensive lumbar canal stenosis who received sublaminar-trimming laminoplasty from 2006 to 2008 were considered for inclusion in the study. The surgery comprised aspects of laminotomy and laminectomy. The following were assessed before surgery and 3 years after surgery: leg and back pain by visual analog scale (VAS), extent of disability by Oswestry Disability Index (ODI), severity of back pain by Japanese Orthopedic Association Score for Back Pain (JOA), walking tolerance, and leg numbness. Complications were noted. RESULTS: A total of 49 patients were included in the study (mean age 65.6 ± 10.6 years). VAS leg and back pain, ODI, and JOA scores significantly changed from before surgery to 3 years after surgery (P < 0.001). Mean changes (95 % confidence interval) were -6.2 (-6.7, -5.7), -4.3 (-4.8, -3.8), -21.4 (-23.4, -19.5), and 13.4 (12.1, 14.7) for leg pain, back pain, ODI, and JOA scores, respectively. Patients experienced significant improvements in walking tolerance and leg numbness (P < 0.001). There were no instances of recurrent stenosis or postoperative spinal instability. Complications included intraoperative dural tear (n = 2), postoperative urinary tract infection (n = 2), and inadequate decompression and junctional stenosis during follow-up (both n = 1). CONCLUSION: Sublaminar-trimming laminoplasty shows promise as an effective treatment for extensive lumbar canal stenosis.

Three-dimensional computer graphics-based ankle morphometry with computerized tomography for total ankle replacement design and positioning.

Morphometry of the bones of the ankle joint is important for the design of joint replacements and their surgical implantations. However, very little three-dimensional (3D) data are available and not a single study has addressed the Chinese population. Fifty-eight fresh frozen Chinese cadaveric ankle specimens, 26 females, and 32 males, were CT-scanned in the neutral position and their 3D computer graphics-based models were reconstructed. The 3D morphology of the distal tibia/fibula segment and the full talus was analyzed by measuring 31 parameters, defining the relevant dimensions, areas, and volumes from the models. The measurements were compared statistically between sexes and with previously reported data from Caucasian subjects. The results showed that, within a general similarity of ankle morphology between the current Chinese and previous Caucasian subjects groups, there were significant differences in 9 out of the 31 parameters analyzed. From a quantitative comparison with available prostheses designed for the Caucasian population, few of these designs have both tibial and talar components suitable in dimension for the Chinese population. The current data will be helpful for the sizing, design, and surgical positioning of ankle replacements and for surgical instruments, especially for the Chinese population.

Inter-joint sharing of total support moments in the lower extremities during gait in narrow-heeled shoes of different heights.

The study aimed to investigate the influence of the base and height of shoe heels on the total support moment (Ms) and individual joint contributions during gait. Fifteen healthy females walked barefoot and with narrow-heeled shoes (heel heights: 3.9, 6.3 and 7.3 cm) while kinematic and kinetic data were measured. Compared with the barefoot condition, the subjects maintained unaltered Ms in the sagittal plane in shod conditions. This was achieved by increasing the knee extensor moment to compensate for the diminished ankle plantarflexor moments in medium and high heel conditions. In the frontal plane, subjects in shod conditions had to sustain an increased Ms for balance control during late single-leg stance with increased knee abductor and ankle pronator moments as a result of the reduced base of the heels. The results will be helpful for future shoe designs to reduce fall risks and prevent relevant musculoskeletal problems.

Influence of model complexity and problem formulation on the forces in the knee calculated using optimization methods.

BACKGROUND: Predictions of the forces transmitted by the redundant force-bearing structures in the knee are often performed using optimization methods considering only moment equipollence as a result of simplified knee modeling without ligament contributions. The current study aimed to investigate the influence of model complexity (with or without ligaments), problem formulation (moment equipollence with or without force equipollence) and optimization criteria on the prediction of the forces transmitted by the force-bearing structures in the knee. METHODS: Ten healthy young male adults walked in a gait laboratory while their kinematic and ground reaction forces were measured simultaneously. A validated 3D musculoskeletal model of the locomotor system with a knee model that included muscles, ligaments and articular surfaces was used to calculate the joint resultant forces and moments, and subsequently the forces transmitted in the considered force-bearing structures via optimization methods. Three problem formulations with eight optimization criteria were evaluated. RESULTS: Among the three problem formulations, simultaneous consideration of moment and force equipollence for the knee model with ligaments and articular contacts predicted contact forces (first peak: 3.3-3.5 BW; second peak: 3.2-4.2 BW; swing: 0.3 BW) that were closest to previously reported theoretical values (2.0-4.0 BW) and in vivo data telemetered from older adults with total knee replacements (about 2.8 BW during stance; 0.5 BW during swing). Simultaneous consideration of moment and force equipollence also predicted more physiological ligament forces (< 1.0 BW), which appeared to be independent of the objective functions used. Without considering force equipollence, the calculated contact forces varied from 1.0 to 4.5 BW and were as large as 2.5 BW during swing phase; the calculated ACL forces ranged from 1 BW to 3.7 BW, and those of the PCL from 3 BW to 7 BW. CONCLUSIONS: Model complexity and problem formulation affect the prediction of the forces transmitted by the force-bearing structures at the knee during normal level walking. Inclusion of the ligaments in a knee model enables the simultaneous consideration of equations of force and moment equipollence, which is required for accurately estimating the contact and ligament forces, and is more critical than the adopted optimization criteria.