Oliver Rettig

A new kinematic model of the upper extremity based on functional joint parameter determination for shoulder and elbow

A new upper extremity model is introduced for clinical application. It combines the advantages of functional methods to determine the joint parameters for the shoulder joint centre and the elbow axis location with the ease of a minimal skin mounted marker set. Soft tissue artefacts at the shoulder and upper arm are reduced via a coordinate transfer between dynamic calibration and the actual motion analyzed. A unique technical frame linked to markers on the forearm is defined for the humerus. The protocol has been applied to 50 subjects over a wide age range (5-85 years) and with varying physical status, proving clinical feasibility. Variability in joint centre localization in repeated measures was typically below 1 cm. Based on these estimated joint centre locations for shoulder and elbow, three shoulder joint angles together with elbow flexion and forearm pro-/supination were determined in a large set of static arm postures in 5 subjects. These were compared to synchronous universal goniometer measurements to analyse intra-tester, inter-tester, and inter-subject repeatability. Differences between the computed angles and the angles obtained directly with the goniometer remained below +/-5 degrees for joint angles up to 120 degrees and +/-10 degrees above 120 degrees.

Dynamic assist by carbon fiber spring AFOs for patients with myelomeningocele.

Patients with calf muscle insufficiency and a calcaneus gait are often dependent on ankle-foot orthoses (AFO). The orthosis is intended to improve walking and posture and should prevent structural deformities. AFOs are often manufactured with a dorsiflexion stop. The design of this type of orthosis has been investigated in several previous studies. In the current study, orthoses with a dorsal carbon fiber spring were compared with the classic design. Five patients with Spina Bifida took part in the current study. All participants underwent a 3D gait analysis including kinematic (VICON infrared cameras) and kinetic (Kistler force plates) data collection. The measurements showed that the carbon spring was able to support the patient during the complete stance phase. It was found that the use of a carbon fiber spring significantly increases the energy return during the 3rd rocker, simulating the natural push-off action (p<0.05). Via a simple mechanical test, the contribution of the carbon spring to the overall kinetics could be estimated proving that the spring does assist the patient for push-off. The more physiological ankle and knee kinematics implies a functional improvement from the carbon springs compared to classic orthosis. This investigation showed, further, that in the fitting process a neutral alignment with the shoe wear has to be carefully checked since the spring kinematics and kinetics during stance phase were influenced significantly by the alignment. Further studies are needed to assess the clinical outcome and to prove the functional benefit of this kind of orthosis.

Can shoulder arthroplasty restore the range of motion in activities of daily living? A prospective 3D video motion analysis study.

HYPOTHESIS There are limited data how total shoulder arthroplasty (TSA) improves shoulder function during activities of daily living (ADL). The hypothesis of this study was that the range of motion (ROM) in ADL gets back to normal after TSA. MATERIALS AND METHOD We examined 13 patients before they received TSA for osteoarthritis and 6 months postoperatively with a 3D motion video analysis during 3 ADL and compared them with a control group without any shoulder pathology. RESULT Comparing the TSA status preoperatively and postoperatively resulted in a significant increase of the mean values of the ROMs in the ADL in all planes (P < .05). When the postoperative ROM was compared with the controls, TSA was able to restore the ROM in all planes except for abduction in 2 of 3 ADL. The patients were not able to use their maximum active abduction during the course of the ADL. DISCUSSION TSA improves the ROM in ADL, but it cannot return completely to normal in abduction after 6 months. CONCLUSION This is not related to limitations of active or passive ROM but may be due to impaired proprioception or pathologic movement patterns, or both.

Three-dimensional motion analysis of compensatory movements in patients with radioulnar synostosis performing activities of daily living.

BackgroundThe aim of this study was to quantify the compensatory movements of the shoulder and elbow in patients with congenital radioulnar synostosis during 10 activities of daily living (ADL).MethodsMaximum and minimum joint angles and range of motion were measured by use of a motion capture system in seven patients and seven matched controls. The forearm was fixed in 0° of rotation in four patients and in 20° of pronation in three patients.ResultsThe main compensatory movements were shoulder internal/external rotation during five ADL tasks, shoulder abduction/adduction and elbow flexion/extension during three tasks, and shoulder flexion/extension during two tasks. These compensatory movements were observed mainly when turning a key and drawing.ConclusionsPatients with congenital radioulnar synostosis in nearly neutral rotation could perform all ADL tasks with the aid of compensatory movements of the shoulder and elbow.

Motion analysis of the upper extremity in children with unilateral cerebral palsy—An assessment of six daily tasks

Restrictions in range of motion of the upper extremity are common in patients with unilateral cerebral palsy (CP). The purpose of this study was to investigate movement deviations of the upper extremity in children with unilateral CP by means of 3D motion capture as well as by the use of easy to use scores and questionnaires (MACS, MRC, MAS, ABILHAND-Kids). 16 children with a spastic, unilateral CP were included and compared to a group of 17 typically developing adolescents (TD). The movement time and range of motion (ROM) of six uni- and bimanual daily tasks were compared and correlated with the scores and questionnaires. Movement times increased significantly with involvement according to MACS in all tasks. The restrictions in ROM were pronounced in the forearm. As a compensatory mechanism the children of the MACS 2 and 3 groups showed increased trunk movement. Furthermore, there was a positive correlation between the MACS and the ABILHAND-Kids Questionnaire. In contrast to previous studies, which reported a correlation between the restrictions in ROM and the MACS, this study showed no consistent correlation between the restrictions in ROM neither with the MACS nor with the ABILHAND-Kids. While the MACS and the ABILHAND-Kids function as a simple rating tool for clinical use, the detailed analysis of different daily tasks using 3-D-motion capture provides more detailed information about the movement deviations and spatiotemporal parameters.

Conjunct rotation: Codman’s paradox revisited

This contribution mathematically formalizes Codman’s idea of conjunct rotation, a term he used in 1934 to describe a paradoxical phenomenon arising from a closed-loop arm movement. Real (axial) rotation is distinguished from conjunct rotation. For characterizing the latter, the idea of reference vector fields is developed to define the neutral axial position of the humerus for any given orientation of its long axis. This concept largely avoids typical coordinate singularities arising from decomposition of 3D joint motion and therefore can be used for postural (axial) assessment of the shoulder joint both clinically and in sports science in almost the complete accessible range of motion. The concept, even though algebraic rather complex, might help to get an easier and more intuitive understanding of axial rotation of the shoulder in complex movements present in daily life and in sports.

Patient-specific bone geometry and segment inertia from MRI images for model-based analysis of pathological gait

Patient-specific modeling is a vital component in the translation of computational multibody dynamics into clinical practice. Recent research has focused on ways to derive such models from medical imaging, but the process is usually time consuming and sensitive to operator skill. Here, we present methods to derive kinematic and inertial properties of body segments from MRI images, and condense them into a dynamically consistent patient-specific multibody model (PSM). We develop a semi-automated tool chain to classify bone, muscle and fat in the lower body and use optimization and geometrical methods to derive personalized bone meshes and segment inertial properties. The tool chain is applied to investigate the gait of a 12-yr old female with bone deformities. The patient-specific results are compared to those arising from generic scaled models with parameters based on regression equations. We found several kinematic and inertial differences between the two models, and overall the PSM resulted in markedly smaller angular and force residuals. The PSM was able to capture vital aspects of this patient׳s gait in the transverse plane that were overlooked by the generic model. These results are relevant to the use of multibody dynamics in the planning of surgical interventions, and form the basis for developing efficient and automatic methods to create patient-specific models.

Does the reverse shoulder prosthesis medialize the center of rotation in the glenohumeral joint

Reverse shoulder arthroplasty is commonly used to improve the function of osteoarthritic shoulders in cases with irreparable refractory rotator cuff-tear arthropathy when conventional prosthesis designs cannot be applied. There is indication that moving the glenohumeral joint center more medially may lead to improved shoulder function by extending the lever arm for the deltoid muscle and facilitating muscle recruitment. However, there is little experimental evidence for this medialization effect. Marker based motion data of pre- and one year postoperative examinations on nine subjects who underwent reverse shoulder arthroplasty were analyzed applying functional methods for joint center estimation. The aim was to determine the location of the functional center of rotation in the operated and the non-operated contralateral side before and after surgery to verify if the joint center of this reverse prosthesis design is located more medially compared to the anatomic situation before surgery. It was shown that the operated shoulders demonstrated a medialization effect of 8.3±4.3mm. For the non-operated side the difference was 0.1±2.3mm, proving the accuracy of measurements.

Proposition of a protocol to evaluate upper-extremity functional deficits and compensation mechanisms: application to elbow contracture

AbstractObjective Instrumented gait analysis is widely accepted as an objective assessment of lower-extremity function. Conversely, upper-extremity function suffers from lack of objective evaluation. The present paper aims at proposing a protocol to be used to clinically and objectively evaluate upper-extremity function whatever the pathological joint. Secondly, it aims at better understanding the consequences on upper-extremity function and the compensation mechanisms induced by elbow contracture. Elbow contracture was simulated in this study by using a brace.DesignTwelve healthy subjects followed an instrumented 3D movement analysis while performing 11 daily life movements. The movements were performed with 3 different elbow contracture conditions, simulated by wearing an adjustable elbow brace.ResultsThe proposed protocol was successful in creating a wide range of motion at all the upper-extremity joints. The activity-related range of motion and the mean range of motion computed on the whole set of daily life movements were effective in evaluating the severity of elbow contracture. The lack of elbow flexion was compensated by trunk flexion, hand flexion and radial deviation, and combined movement of shoulder flexion, abduction, and humeral internal rotation. Deficit in elbow extension was mainly compensated by the use of trunk flexion.ConclusionA protocol could be proposed for the objective evaluation of upper-extremity function. Its application to elbow contracture suggests that loss of elbow flexion affects more movements than loss of elbow extension.

Knee-ankle-foot orthosis with powered knee for support in the elderly

A prototype of a powered knee orthotic device was developed to determine whether fractional external torque and power support to the knee relieves the biomechanical loads and reduces the muscular demand for a subject performing sit-to-stand movements. With this demonstrator, consisting of the subsystems actuation, kinematics, sensors, and control, all relevant sensor data can be acquired and full control is maintained over actuator parameters. A series-elastic actuator based on a direct current motor provides up to 30 Nm torque to the knee via a hinge joint with an additional sliding degree of freedom. For reasons of feasibility under everyday conditions, user intention is monitored by employing a noninvasive, nonsticking muscle activity sensor to replace electromyographic sensors, which require skin preparation. Furthermore, foot plates with force sensors have been developed and included to derive ground reaction forces. The actual knee torque needed to provide the desired support is based on an inverse dynamics model using ground reaction forces signals and leg kinematics. A control algorithm including disturbance feed forward has been implemented. A demonstration experiment with two subjects showed that 23 % of moment support in fact leads to a similar reduction in activation of the main knee extensor muscle.