Comparison of the Radiographic and Clinical Outcomes between the Sinus Tarsi and Extended Lateral Approaches for Intra-Articular Calcaneal Fractures: A Retrospective Study.

The aim of this study was to compare the radiological and functional outcomes of the extended lateral and sinus tarsi approaches for managing displaced intraarticular calcaneal fractures. This retrospective study involved 44 patients with displaced intra-articular calcaneal fractures. The patients were treated with either the extended lateral or sinus tarsi approach and followed up for at least a year. The radiological and clinical outcomes were compared between the approaches. The waiting time for surgery was shorter and the complication rate was lower in the sinus tarsi approach group than in the other group. There were no significant differences in the American Orthopedic Foot and Ankle Society ankle-hindfoot score, Foot Function Index, or visual analog scale score between the groups. In both groups, the radiological outcomes (Böhler angle, calcaneal width, and calcaneal height) were better postoperatively than preoperatively. The sinus tarsi approach is a safe and effective alternative to the extended lateral approach for managing displaced intraarticular calcaneal fractures. It is associated with a lower complication rate and a shorter waiting time for surgery than the extended lateral approach, with similar functional and radiological outcomes.

Patient-specific instrumentation improves functional kinematics of minimally-invasive total knee replacements as revealed by computerized 3D fluoroscopy.

BACKGROUND AND OBJECTIVES: Minimally-invasive total knee arthroplasty (MIS-TKA) has demonstrated very good short-term success, but its mid- to long-term results remain inconclusive. The success may be related to the tradeoff between a small incision and accurate positioning of the implant components. Patient-specific instrumentation (PSI) aims to improve the accuracy in restoring the knee axis and the clinical outcomes for MIS-TKA, but the results are yet to be confirmed by accurate assessment during functional activities. The purpose of the current study was to measure and compare the in vivo three-dimensional (3D) rigid-body and surface kinematics of MIS-TKA implanted with and without PSI during isolated knee active flexion/extension and sit-to-stand using state-of-the-art 3D model-based fluoroscopy technology. METHODS: Ten patients treated for advanced medial knee osteoarthritis by MIS-TKA without PSI (non-PSI group) and nine with PSI (PSI group) participated in the current study. Each subject performed non-weight-bearing knee flexion/extension and sit-to-stand tasks while the motion of the prosthetic knee was under bi-plane fluoroscopy surveillance. The computer models of each of the knee prosthesis components were registered to the measured fluoroscopy images for each time frame via a novel validated 3D fluoroscopy method. Non-parametric 1-tailed Mann-Whitney tests were performed to detect the differences in the joint and surface kinematic variables every 10° of knee flexion between the non-PSI and PSI groups. The 1-tailed significance level was at α = 0.05. RESULTS: The PSI group showed clear, coupled flexion/internal rotation during activities, while the non-PSI group remained roughly at an externally rotated position with slight internal rotations. The coupled rotation in the PSI group was accompanied by an anterior displacement of the medial contact and a posterior displacement of the lateral contact, which was different from the screw-home mechanism. Neither of the two groups showed the normal roll-back phenomenon, i.e., posterior translation of the femur relative to the tibia during knee flexion. CONCLUSIONS: With the state-of-the-art 3D fluoroscopy method, differences in both the rigid-body and surface kinematics of the prosthetic knees between MIS-TKA with and without PSI were identified. Patients with PSI demonstrated significant positive effects on the reconstructed rigid-body kinematics of the knee, showing clearer coupled flexion/internal rotations - an important kinematic characteristic in healthy knees - than those without PSI during activities with or without weight-bearing. However, none of them showed normal contact patterns. The current findings will be helpful for surgical instrument design, as well as for surgical decision-making in MIS total knee arthroplasty.

Effects of gait speed on the body's center of mass motion relative to the center of pressure during over-ground walking.

Preferred walking speed (PWS) reflects the integrated performance of the relevant physiological sub-systems, including energy expenditure. It remains unclear whether the PWS during over-ground walking is chosen to optimize one's balance control because studies on the effects of speed on the body's balance control have been limited. The current study aimed to bridge the gap by quantifying the effects of the walking speed on the body's center of mass (COM) motion relative to the center of pressure (COP) in terms of the changes and directness of the COM-COP inclination angle (IA) and its rate of change (RCIA). Data of the COM and COP were measured from fifteen young healthy males at three walking speeds including PWS using a motion capture system. The values of IAs and RCIAs at key gait events and their average values over gait phases were compared between speeds using one-way repeated measures ANOVA. With increasing walking speed, most of the IA and RCIA related variables were significantly increased (p<0.05) but not for those of the frontal IA. Significant quadratic trends (p<0.05) with highest directness at PWS were found in IA during single-limb support, and in RCIA during single-limb and double-limb support. The results suggest that walking at PWS corresponded to the COM-COP control maximizing the directness of the RCIAs over the gait cycle, a compromise between the effects of walking speed and the speed of weight transfer. The data of IA and RCIA at PWS may be used in future assessment of balance control ability in people with different levels of balance impairments.

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.

Comparison of body's center of mass motion relative to center of pressure between treadmill and over-ground walking.

Treadmills have been used in rehabilitation settings to provide convenient protocols and continuous monitoring of movement over multiple cycles at well-controlled speeds for gait and balance training. However, the potential differences in the movement control may affect the translation of the training outcomes to real life over-ground walking (OW). The similarities and differences in the balance control between treadmill walking (TW) and OW have largely been unexplored. The current study bridged the gap by comparing the motions of the body's center of mass (COM) relative to the center of pressure (COP) between TW and OW, in terms of the COM-COP inclination angle (IA) and its rate of change (RCIA). The movement of the COM and COP separately were quite different between OW and TW, but when describing the COM motion relative to the COP, the COM motions became similar qualitatively with similar butterfly patterns. However, significantly increased peak values in themediolateral RCIA and greater ranges of mediolateral IA were found during TW (p<0.004). In the sagittal plane, the posterior velocity of the belt led to an anterior RCIA (posterior RCIA in OW) with increasing anterior IA during early double-limb support phase, and reduced posterior RCIA (p<0.009) with an increased anterior IA (p<0.001) during the remainder of the phase. These differences between TW and OW may have to be taken into account in future designs of strategies to optimize the translation of treadmill gait training outcomes into real life over-ground walking.

Effects of belt speed on the body's center of mass motion relative to the center of pressure during treadmill walking.

Treadmills are often used in clinical settings to improve walking balance control in patients with gait impairments. However, knowledge of the effects of belt speed on balance control remains incomplete. The current study determined such effects in terms of inclination angles (IA) and the rate of change (RCIA) of the center of mass (COM) motion relative to the center of pressure (COP) in twelve healthy adults at five belt speeds, including the subjects' preferred walking speed (PWS), as measured using a motion capture system and an instrumented treadmill. The values of IAs and RCIAs at key gait events and their average values over single-limb support (DLS) and double-limb support (DLS) were compared between speeds using one-way repeated measures analysis of variances. While the COM-COP controls were different between SLS and DLS, they were inter-related to form an integrated whole. Among the belt speeds, the range of frontal IA during SLS was smallest at the PWS (p<0.05). With increasing speed, most variables of the sagittal IAs and RCIAs, and of the frontal RCIAs during DLS showed a linearly increasing trend (p<0.001). A linearly decreasing trend was found in the frontal IA at toe-off and in the average frontal RCIA during SLS (p<0.05). The PWS appeared to be the best compromise between frontal stability during SLS and smooth weight-transfer during DLS. The current results provide useful baseline data for selecting speeds according to training needs, and may be helpful for developing protocols for gait retraining for patients with gait impairment.

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.

Effects of soft tissue artifacts on differentiating kinematic differences between natural and replaced knee joints during functional activity.

Functional performance of total knee replacement (TKR) is often assessed using skin marker-based stereophotogrammetry, which can be affected by soft tissue artifacts (STA). The current study aimed to compare the STA and their effects on the kinematics of the knee between twelve patients with TKR and twelve healthy controls during sit-to-stand, and to assess the effects of STA on the statistical between-group comparisons. Each subject performed the sit-to-stand task while motions of the skin markers and the knees were measured by a motion capture system integrated with a three-dimensional fluoroscopy technique. The bone motions measured by the three-dimensional fluoroscopy were taken as the gold standard, with respect to which the STA of the markers were obtained. The STA were found to affect the calculated segmental poses and knee kinematics between the groups differently. The STA resulted in artefactual posterior displacements of the knee joint center, with magnitudes significantly greater in TKR than controls (p<0.01). The STA-induced knee external rotations in TKR were smaller than those in controls with mean differences of 2.3-3.0°. These between-group differences in the STA effects on knee kinematics in turn concealed the true between-group differences in the anterior-posterior translation and internal/external rotation of knee while leading to false significant between-group differences in the abduction/adduction and proximal-distal translation.

Calibration of an instrumented treadmill using a precision-controlled device with artificial neural network-based error corrections.

Instrumented treadmills (ITs) are used to measure reaction forces (RF) and center of pressure (COP) movements for gait and balance assessment. Regular in situ calibration is essential to ensure their accuracy and to identify conditions when a factory re-calibration is needed. The current study aimed to develop and calibrate in situ an IT using a portable, precision-controlled calibration device with an artificial neural network (ANN)-based correction method. The calibration device was used to apply static and dynamic calibrating loads to the surface of the IT at 189 and 25 grid-points, respectively, at four belt speeds (0, 4, 6 and 8 km/h) without the need of a preset template. Part of the applied and measured RF and COP were used to train a threelayered, back-propagation ANN model while the rest of the data were used to evaluate the performance of the ANN. The percent errors of Fz and errors of the Px and Py were significantly decreased from a maximum of -1.15%, -1.64 mm and -0.73 mm to 0.02%, 0.02 mm and 0.03 mm during static calibration, respectively. During dynamic calibration, the corresponding values were decreasing from -3.65%, 2.58 mm and -4.92 mm to 0.30%, -0.14 mm and -0.47 mm, respectively. The results suggest that the calibration device and associated ANN will be useful for correcting measurement errors in vertical loads and COP for ITs.

Anticipatory changes in control of swing foot and lower limb joints when walking onto a moving surface traveling at constant speed.

Adapting to a predictable moving surface such as an escalator is a crucial part of daily locomotor tasks in modern cities. However, the associated biomechanics have remained unexplored. In a gait laboratory, fifteen young adults walked from the ground onto a moving or a static surface while their kinematic and kinetic data were obtained for calculating foot and pelvis motions, as well as the angles and moments of the lower limb joints. Between-surface-condition comparisons were performed using a paired t-test (α = 0.05). The results showed that anticipatory locomotor adjustments occurred at least a stride before successfully walking onto the moving surface, including increasing step length and speed in the trailing step (p < 0.05), but the opposite in the leading step (p < 0.05). These modifications reduced the plantarflexor moment of the trailing ankle needed for stabilizing the body, while placing increased demand on the knee extensors of the trailing stance limb. For a smooth landing and to reduce the risk of instability, the subjects adopted a flat foot contact pattern with reduced leading toe-clearance (p < 0.05) at an instantaneous speed matching that of the moving surface (p > 0.05), mainly through reduced extension of the trailing hip but increased pelvic anterior tilt and leading swing ankle plantarflexion (p < 0.05). The current results provide baseline data for future studies on other populations, which will contribute to the design and development of strategies to address falls while transferring onto moving surfaces such as escalators.

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.

Effects of positioning on radiographic measurements of ankle morphology: a computerized tomography-based simulation study.

BACKGROUND: Measurements of the morphology of the ankle joint, performed mostly for surgical planning of total ankle arthroplasty and for collecting data for total ankle prosthesis design, are often made on planar radiographs, and therefore can be very sensitive to the positioning of the joint during imaging. The current study aimed to compare ankle morphological measurements using CT-generated 2D images with gold standard values obtained from 3D CT data; to determine the sensitivity of the 2D measurements to mal-positioning of the ankle during imaging; and to quantify the repeatability of the 2D measurements under simulated positioning conditions involving random errors. METHOD: Fifty-eight cadaveric ankles fixed in the neutral joint position (standard pose) were CT scanned, and the data were used to simulate lateral and frontal radiographs under various positioning conditions using digitally reconstructed radiographs (DRR). RESULTS AND DISCUSSION: In the standard pose for imaging, most ankle morphometric parameters measured using 2D images were highly correlated (R > 0.8) to the gold standard values defined by the 3D CT data. For measurements made on the lateral views, the only parameters sensitive to rotational pose errors were longitudinal distances between the most anterior and the most posterior points of the tibial mortise and the tibial profile, which have important implications for determining the optimal cutting level of the bone during arthroplasty. Measurements of the trochlea tali width on the frontal views underestimated the standard values by up to 31.2%, with only a moderate reliability, suggesting that pre-surgical evaluations based on the trochlea tali width should be made with caution in order to avoid inappropriate selection of prosthesis sizes. CONCLUSIONS: While highly correlated with 3D morphological measurements, some 2D measurements were affected by the bone poses in space during imaging, which may affect surgical decision-making in total ankle arthroplasty, including the amount of bone resection and the selection of the implant sizes. The linear regression equations for the relationship between 2D and 3D measurements will be helpful for correcting the errors in 2D morphometric measurements for clinical applications.