Evaluation of a method to quantify posture and scapula position using biplanar radiography.

BACKGROUND: Recent studies have stated the relevance of having new parameters to quantify the position and orientation of the scapula with patients standing upright. Although biplanar radiography can provide 3D reconstructions of the scapula and the spine, it is not yet possible to acquire these images with patients in the same position. METHODS: Two pairs of images were acquired, one for the 3D reconstruction of the spine and ribcage and one for the 3D reconstruction of the scapula. Following 3D reconstructions, scapular alignment was performed in two stages, a coarse alignment based on manual annotations of landmarks on the clavicle and pelvis, and an adjusted alignment. Clinical parameters were computed: protraction, internal rotation, tilt and upward rotation. Reproducibility was assessed on an in vivo dataset of upright biplanar radiographs. Accuracy was assessed using supine cadaveric CT-scans and digitally reconstructed radiographs. FINDINGS: The mean error was less than 2° for all clinical parameters, and the 95 % confidence interval for reproducibility ranged from 2.5° to 5.3°. INTERPRETATION: The confidence intervals were lower than the variability measured between participants for the clinical parameters assessed, which indicates that this method has the potential to detect different patterns in pathological populations.

3D reconstruction of the scapula from biplanar X-rays for pose estimation and morphological analysis.

BACKGROUND: Patient-specific scapular shape in functional posture can be highly relevant to clinical research. Biplanar radiography is a relevant modality for that purpose with already two existing assessment methods. However, they are either time-consuming or lack accuracy. The aim of this study was to propose a new, more user-friendly and accurate method to determine scapular shape. METHODS: The proposed method relied on simplified manual inputs and an upgraded version of the first 3D estimate based on statistical inferences and Moving-Least Square (MLS) deformation of a template. Then, manual adjustments, with real-time MLS algorithm and contour matching adjustments with an adapted minimal path method, were added to improve the match between the projected 3D model and the radiographic contours. The accuracy and reproducibility of the method were assessed (with 6 and 12 subjects, respectively). FINDINGS: The shape accuracy was in average under 2 mm (1.3 mm in the glenoid region). The reproducibility study on the clinical parameters found intra-observer 95% confidence intervals under 3 mm or 3° for all parameters, except for glenoid inclination and Critical Shoulder Angle, ranging between 3° and 6°. INTERPRETATION: This method is a first step towards an accurate reconstruction of the scapula to assess clinical parameters in a functional posture. This can already be used in clinical research on non-pathologic bones to investigate the scapulothoracic joint in functional position.

Multimodal data analysis of knee osteoarthritis assessment: factors selection for conservative care decision making.

When assessing a patient with knee osteoarthritis (OA), a number of factors are considered to guide treatment plan, namely, demographic, radiographic, clinical, musculoskeletal, and biomechanical factors. The aim of this study is to identify which of these factors are the most related to each other to potentially better prioritize the modifiable factors to be addressed as they may influence treatment outcomes. We investigated a multimodal canonical correlation analysis to evaluate associations between these factors. The analysis was performed on 415 OA patients who were not candidates for knee arthroplasty, to identify factors that are associated to the patients' clinical conditions.

Tibio-femoral joint contact in healthy and osteoarthritic knees during quasi-static squat: A bi-planar X-ray analysis.

The aim of this study was to quantify the tibio-femoral contact point (CP) locations in healthy and osteoarthritic (OA) subjects during a weight-bearing squat using stand-alone biplanar X-ray images. Ten healthy and 9 severe OA subjects performed quasi-static squats. Bi-planar X-ray images were recorded at 0°, 15°, 30°, 45°, and 70° of knee flexion. A reconstruction/registration process was used to create 3D models of tibia, fibula, and femur from bi-planar X-rays and to measure their positions at each posture. A weighted centroid of proximity algorithm was used to calculate the tibio-femoral CP locations. The accuracy of the reconstruction/registration process in measuring the quasi-static kinematics and the contact parameters was evaluated in a validation study. The quasi-static kinematics data revealed that in OA knees, adduction angles were greater (p<0.01), and the femur was located more medially relative to the tibia (p<0.01). Similarly, the average CP locations on the medial and lateral tibial plateaus of the OA patients were shifted (6.5±0.7mm; p<0.01) and (9.6±3.1mm; p<0.01) medially compared to the healthy group. From 0° to 70° flexion, CPs moved 8.1±5.3mm and 8.9±5.3mm posteriorly on the medial and lateral plateaus of healthy knees; while in OA joints CPs moved 10.1±8.4mm and 3.6±2.8mm posteriorly. The average minimum tibio-femoral bone-to-bone distances of the OA joints were lower in both compartments (p<0.01). The CPs in the OA joints were located more medially and displayed a higher ratio of medial to lateral posterior translations compared to healthy joints.

A new morphological classification for greater tuberosity fractures of the proximal humerus: validation and clinical implications.

In this study, we describe a morphological classification for greater tuberosity fractures of the proximal humerus. We divided these fractures into three types: avulsion, split and depression. We retrospectively reviewed all shoulder radiographs showing isolated greater tuberosity fractures in a Level I trauma centre between July 2007 and July 2012. We identified 199 cases where records and radiographs were reviewed and included 79 men and 120 women with a mean age of 58 years (23 to 96). The morphological classification was applied to the first 139 cases by three reviewers on two occasions using the Kappa statistic and compared with the AO and Neer classifications. The inter- and intra-observer reliability of the morphological classification was 0.73 to 0.77 and 0.69 to 0.86, respectively. This was superior to the Neer (0.31 to 0.35/0.54 to 0.63) and AO (0.30 to 0.32/0.59 to 0.65) classifications. The distribution of avulsion, split and depression type fractures was 39%, 41%, and 20%, respectively. This classification of greater tuberosity fractures is more reliable than the Neer or AO classifications. These distinct fracture morphologies are likely to have implications in terms of pathophysiology and surgical technique.

Influence of prosthetic humeral head size and medial offset on the mechanics of the shoulder with cuff tear arthropathy: a numerical study.

This numerical study assesses the influence of an oversized humeral hemiprosthesis with a larger medial offset on the mechanics of the shoulder with cuff tear arthropathy (CTA). Shoulder elevation in the scapular plane is performed, and a Seebauer Type IIa CTA is simulated: a massive rotator cuff tear, a proximal and static migration of the humeral head, and two contacts with friction (glenohumeral and acromiohumeral). The CTA model without a prosthesis (friction coefficient 0.3) is evaluated first as a reference model. Then, three humeral head prosthetic geometries (friction coefficient 0.15) are evaluated: anatomical head, oversized head, and oversized head with a large medial offset. The function of the middle deltoid (i.e. moment arm, applied force, and strength), the contact forces, and the range of motion are studied. The anatomical head, which reduces friction by half, decreases the middle deltoid force (25%) and the contact forces (glenoid 7%; acromion 25%), and increases the range of motion from 41 to 54°. The oversized head increases the moment arm (15%) and the middle deltoid strength (13%), which further decreases the deltoid force (7%) and the contact forces (glenoid 7%; acromion 17%), and increases the range of motion from 54° to 69°. The oversized head with a large medial offset enhances these effects: the moment arm increases by another 3.1%, the deltoid force decreases by another 5% and the acromiohumeral contact force by another 12%, and the range of motion increases from 69° to 84°. These results suggest that increasing the medial offset and oversizing the hemiprosthetic head improve the function of the deltoid, reduce acromial solicitation, and restore elevation to almost 90°.

Influence of the medial offset of the proximal humerus on the glenohumeral destabilising forces during arm elevation: a numerical sensitivity study.

This study assessed the influence of the medial offset of the proximal humerus on the glenohumeral destabilising forces during arm elevation in the plane of the scapula, using the AnyBody Modeling System. The variability of the medial offset was covered using literature data (minimum, 0 mm; average, 7 mm and maximum, 14 mm). The following parameters were studied: moment arm (MA; middle deltoid), muscle activity and stability ratios. The minimum offset decreased the MA of the middle deltoid ( -11%), increased its activation (+18%) and its superior destabilising action (+40%). The maximum offset had an opposite effect (+9%, -30% and -30%). The stabilising action of the rotator cuff was not affected. Varying the medial offset seems to have an influence on the destabilising action of the middle deltoid. The AnyBody simulation tool appears to be promising in establishing links between shoulder morphology and stability.

Effect of axis alignment on in vivo shoulder kinematics.

BACKGROUND. To describe 3D shoulder joint movements, the International Society of Biomechanics (ISB) recommends using segment coordinate systems (SCSs) on the humerus, scapula and thorax, and joint coordinate systems (JCSs) on the shoulder. However, one of the remaining problems is how to define the zero angles when the arm is in an initial reference position. The aim of this paper is to compare various methods of determining the JCSs of the shoulder that make it possible to define the zero angles of the arm in the resting position. METHODS. Able-bodied subjects performed elevation movements in the scapular plane, specifically neutral, internal and external rotations of the humerus. The initial humerus position (at the beginning of the arm movement) and range of motion were analysed for the purpose of clinical interpretation of arm attitude and movement. The following four different JCSs were explored: (1) the standard JCS, defined as recommended by the ISB, (2) a first aligned JCS, where the humerus SCS is initially aligned with the scapula SCS, (3) a second aligned JCS, where the opposite operation is performed and 4) a third aligned JCS, where both the humerus and the scapular SCS are initially aligned with the thorax SCS. FINDINGS. The second aligned JCS was the only method that did not produce any exaggerated range of movement in either anatomical plane. INTERPRETATION. Mathematical JCS alignment allows clearer clinical interpretation of arm attitude and movement.

Evaluation of unipodal stance in knee osteoarthritis patients using knee accelerations and center of pressure.

OBJECTIVE: This study aims to compare knee joint instability and postural impairments during the performance of a unipodal stance task between patients having knee osteoarthritis (OA) and healthy elderly subjects using knee accelerations and center of pressure (COP) measurements. MATERIALS AND METHODS: Twenty patients with medial knee OA and nine healthy individuals participated in this study. Three-dimensional (3D) knee joint accelerations and COP were measured during unipodal stance. The range and the root mean square (RMS) were extracted from medial lateral (ML) and anterior-posterior (AP) knee accelerations, whereas sway area, velocity, and ML and AP ranges were measured from the COP. The average parameters of three trials for each subject were compared between groups. RESULTS: Results show that knee OA patients exhibited a significantly higher range of knee acceleration in both ML (0.22±0.08 g vs 0.15±0.05 g) and AP (0.17±0.06 g vs 0.06±0.01 g) directions and a lower COP velocity (136.6±22.3 mm/s vs 157.6±18.4 mm/s) than did the healthy age-matched group. Significant correlations between the COP and knee acceleration parameters were also obtained. CONCLUSIONS: This study confirmed that patients with knee OA displayed greater body sway than did able-bodied subjects. Moreover, using an accelerometric-based method, this study highlighted the higher knee joint instability in the frontal and sagittal planes in knee OA patients compared with able-bodied subjects during a unipodal standing task.

The responsiveness of three-dimensional knee accelerations used as an estimation of knee instability and loading transmission during gait in osteoarthritis patient's follow-up.

OBJECTIVE: Knee instability and joint loading transmission are two important biomechanical factors in subjects with knee osteoarthritis (OA). However, the relationship between these factors in a rehabilitation treatment remains unclear. The purpose of this study is to determine the responsiveness of a new three-dimensional (3D) acceleration method used as an estimation of knee instability and joint loading transmission during gait in OA subjects after a rehabilitation treatment. METHOD: Twenty-four subjects with medial knee OA were included in this study. They had clinical and gait evaluations before and after 12 weeks of treatment. 3D linear knee accelerations, quadriceps and hamstring isometric strength and Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) pain were quantified, and compared between both evaluations. Nine asymptomatic subjects participated in this study for gait comparison. RESULTS: A significant reduction of the anterior posterior (AP) knee acceleration peak (P=0.02) had been detected after the treatment. No difference for both distal and lateral knee accelerations peak was found. A significant increase in quadriceps (P<0.001) and hamstring (P=0.006) strength was seen after treatment. The WOMAC of pain had shown significant reduction after the treatment (P<0.001). CONCLUSION: The present study demonstrates that the estimation of knee acceleration parameters is sensitive to changes in knee OA gait after a rehabilitation treatment. This study also indicates that a treatment of 3 months which combines therapeutic and exercises program could have benefits on knee OA by increasing AP knee stability and stabilize joint loading transmission during gait.

Habituation to treadmill walking.

The use of a treadmill to evaluate gait patterns makes it possible to analyze many gait cycles and stride to stride variations. The objective of this study was to assess the time required for a subject to habituate to walking on a treadmill. The evolution of knee kinematics and spatio-temporal parameters were analyzed to measure habituation to walking on the treadmill. To obtain this information, data were recorded on 10 healthy subjects for about 45 minutes as they walked on a treadmill. A steady state was attained for knee kinematics and most spatio-temporal parameters at the time the treadmill had attained its maximal speed (approximately 30 seconds). However, 10 minutes were necessary for stride length to become reproducible. Time for habituation to walking on a treadmill must be considered when kinematics are evaluated during gait of healthy and disabled subjects. We have shown that, at least for young, healthy individuals who are non-naïve to walking on a treadmill, a 10-minute warm-up is enough before three-dimensional knee kinematics and spatio-temporal data can be recorded.

Estimation of tibial and femoral 3D linear accelerations during gait.

Shock wave traveling through the skeletal are more and more considered in the development of articular disorders. A method to quantify those skeletal transients is to estimate body segment linear accelerations. However, linear accelerations magnitude is influenced by many factors such as location and fixation of sensors, walking velocity, walking level and also by wearing conditions. Hence, experimental results in literature can't be easily compared and normative data haven't been established yet. The present paper proposes a method to estimate three-dimensional (3D) tibial and femoral linear accelerations during treadmill walking. 15 able-bodied subjects were evaluated. 3D kinematics data recorded from an optoelectronic system (Optotrak 3010, Northern Digital, Canada) at knee joint level were derived to estimated 3D linear accelerations of the tibia and the femur at their respective coordinate system origins.

Computer based method for the three-dimensional kinematic analysis of combined posterior cruciate ligament and postero-lateral complex reconstructions on cadaver knees.

The aim of this study is to evaluate the effect of combined posterior cruciate ligament (PCL) and postero-lateral corner (PLC) reconstruction on laxity and three-dimensional kinematics of cadaver knees. We performed anatomical double bundle PCL reconstruction, and functional one bundle 'over-the-bottom' PCL reconstruction combined with one type of PLC reconstruction, running from the postero-lateral tibia to an isometric point near the lateral epicondyle of the femur. Our results showed that combined reconstruction was necessary to restore rotatory laxity. PLC reconstruction, according to the technique described, invariably created a shift towards internal rotation of the kinematic curves, compared to the intact knee.

Comparison of two methods for reconstruction of the posterior cruciate ligament using a computer based method: quantitative evaluation of laxity, three-dimensional kinematics and ligament deformation measurement in cadaver knees.

The aim of this paper is to present a biomechanical comparison of two different methods for reconstruction of the posterior cruciate ligament in cadaver knees. We used an original computer-based method allowing precise calculation of three-dimensional (3D) knee kinematic parameters as well as the estimation of combined graft deformation (elongation-flexion-torsion). After isolated posterior cruciate ligament (PCL) dissection, double bundle and 'over-the-bottom' methods were performed successively on each knee using synthetic polyester ligaments. The effect of pre-tensioning was tested with the 'over-the-bottom' method. antero-posterior (A-P) and rotational laxity as well as 3D kinematics were recorded and analysed. Our computer based method allowed us to show that both reconstruction methods were equivalent in restoring A-P and rotational laxity as well as kinematic curves. Combined deformation of the prostheses was equivalent for both ligaments.

Computer-based method for the 3-D kinematic analysis of posterior cruciate ligament and postero-lateral corner lesions.

Posterior cruciate ligament (PCL) rupture, whether or not combined with postero-lateral corner (PLC) tears, are more often diagnosed today thanks to improved imaging techniques. However, due to the lack of reliable instrumentation to quantitatively evaluate the knee, much is still unknown about the function of these ligamentous structures. The aim of this paper is to present results on the effect of progressive resection of the PCL and PLC on knee laxity and 3-D knee kinematics. The results show that 3-D movement analysis is important and complements laxity measurements by helping to interpret the complex alteration of knee function.