Jurriaan H. de Groot

The variability of shoulder motions recorded by means of palpation

Objective. The objective of this methodological study is the quantification of the sources of variability in the recorded three-dimensional motions of the shoulder mechanism for comparative purposes. Background. The palpation and subsequent digitization of skeletal landmarks of the shoulder mechanism is a non-invasive and relatively easy method to quantify shoulder orientations. Comparison of individual motions is subject to the accuracy of the palpation method, the magnitude of kinematic redundancy of the shoulder mechanism and inter-subject differences in morphology and physiology. Quantification of these sources of variance i.e. the palpation error, motoric noise and inter-subject differences, demonstrated the accuracy of the method and the potential validity of the descriptive motion parameters, e.g. Cardan angles, in intra- and inter-individual studies for clinical, ergonomical and biomechanical studies. Methods. The orientations of the shoulder bones were recorded five times for each of five subjects by palpation and digitization of 12 skeletal landmarks for 10 equidistant arm elevation postures in the scapular plane. The orientations were described by means of Cardan angles. The palpation error was determined at a standardized initial rest position and expressed by Cardan angles for each recorded posture. Adding motoric noise and inter-subject differences gave the inter-individual variance. Results. The palpation error was approximately 2 °. The major recorded variance originated from motoric noise (±33%) and inter-subject difference (±55%). Conclusions. The palpation method is an accurate means of recording the three-dimensional orientations of the shoulder mechanism and for intra-individual studies. However, inter-subject variability is large.

Localized immediate early gene expression related to the strength of song learning in socially reared zebra finches.

Recent evidence showed that exposure of tape‐tutored zebra finch (Taeniopygia guttata castanotis) males to the tutor song involves neuronal activation in brain regions outside the conventional ‘song control pathways’, particularly the caudal part of the neostriatum (NCM) and of the hyperstriatum ventrale (CMHV). Zebra finch males were reared with a live tutor during the sensitive period for song learning. When, as adults, they were re‐exposed to the tutor song, the males showed increased expression of Fos, the protein product of the immediate early gene c‐fos, in the NCM and CMHV, compared with expression in two conventional ‘song control nuclei’, high vocal centre (HVC) and Area X. The strength of the Fos response (which is a reflection of neuronal activation) in the NCM (but not in the other three regions) correlated significantly and positively with the number of song elements that the birds had copied from the tutor song. Thus, socially tutored zebra finch males show localized neural activation in response to tutor song exposure, which correlates with the strength of song learning.

The scapulo-humeral rhythm: effects of 2-D roentgen projection

Abstract Objective. The objective of this study is to illustrate the low accuracy of two-dimensional (2-D) X-ray projection methods for the quantification of the three-dimensional (3-D) shoulder motions. Background. The traditional method for the quantification of the gleno-humeral motion is by means of 2-D X-ray recording. The motion was characterized by the scapulo-humeral rhythm: the ratio of the nett humeral elevation over nett scapular rotation. The method was based on the quantification of the planar projection of the spatial positions of X-ray dense structures of the scapula. The deformations introduced by the central projection method, a feature of X-ray projection, cannot be compensated for by calibration: the position of the scapula with respect to the camera setting is unknown, and skeletal landmarks of the scapula cannot uniquely be identified. The transformation from 3-D orientations to 2-D angles will, therefore, be inaccurate. Methods. A 2-D X-ray projection of the scapula during a typical arm abduction was simulated. The 3-D motion was obtained by means of palpation and subsequent digitization of skeletal landmarks of the scapula. The 3-D positions of the recorded landmarks were projected on a plane by a simulation based on the parameters of the X-ray equipment. The scapulo-humeral rhythm was calculated for the different scapular landmarks, and for the orientation of the subject with respect to the projection axis. The results were compared with previous published scapulo-humeral rhythms. Results. The scapulo-humeral rhythm depends both on the choice of the skeletal landmarks, used to quantify the scapular rotations, and on the orientation of the subject in the X-ray setting. The full range of results obtained from earlier published experiments could be obtained from a simulation based on a single 3-D arm abduction. Conclusions. The 2-D scapulo-humeral rhythm, obtained from planar X-ray projection, is an inaccurate parameter to define the scapular motions.

Effect of different arm loads on the position of the scapula in abduction postures.

Abstract Objective. The objective of this study is to determine the relation between arm load and the three-dimensional shoulder orientations. Background. Analysis of a musculo-skeletal system by means of an inverse dynamical simulation requires postural data of the bony elements involved. For the shoulder, the positions of the clavicle and the scapula are difficult to record due to the skin displacement. It would therefore be useful to predict the three-dimensional relation between the orientation of the arm, the clavicula and the scapula, i.e. the three-dimensional shoulder rhythm, with respect to the thorax under different load conditions. Methods. The orientation of the clavicula and the scapula was determined with respect to the thorax by means of palpation of skeletal landmarks, for seven postures of arm elevation in the frontal plane at four load conditions: 0, 0.9, 1.9 and 2.9 kg at the wrist. The data were expressed by Cardan angles and analyzed by means of repeated measurements analysis of variance. Results. While the clavicular and scapular angles were significantly related to the arm elevation, no significant relation was found with the load in the hands for the seven arm postures. Conclusions. The three-dimensional shoulder rhythm does not change under different gravitational load conditions on the arm. Relevance The fact that the magnitude of the load does not affect the shoulder postures, i.e. the moment arms of the muscles, facilitates the biomechanical, ergonomical and clinical studies on the shoulder by the reduction on the number of recordings for equal task under different load conditions, and easy imitation of real life tasks in the laboratory.

Velocity effects on the scapulo-humeral rhythm.

OBJECTIVE: The objective of this study is to verify the assumption that the three-dimensional (3-D) shoulder motions can be described by means of an interpolation of statically recorded postures and thus, support the application of non-invasive but static techniques for motion analysis of the shoulder. BACKGROUND: During shoulder motions the scapula moves underneath the skin. Recording of motions is only possible by means of invasive methods. An alternative for the recording is palpation of skeletal landmarks on the scapula and subsequent digitization. The method is non-invasive and relatively easy, but static. Motions are modelled by means of interpolation of the subsequent position recordings. Validity of this method, however, has never been demonstrated. METHODS: Seven subjects performed an alternating abduction-adduction motion of the arm in a plane 30 degrees forward rotated with respect to the frontal plane, at three sub-maximal frequencies: 0.04, 0.25 and 0.50 Hz. The humeral and scapular motions were recorded by means of a two-dimensional (2-D) X-ray video system. The motions of the humerus, the scapular spine and the glenoid ridge were defined by angles, and the sinusoidal motion curves were characterized by means of the offset, the amplitude and the phase of the motions. RESULTS: By means of Repeated Measurements Multi-Variate Analysis of Variance, a significant effect of arm motion on the phase and the amplitude of the scapular motion was found. However, the magnitude of the effects are negligibly small for the present applications at sub-maximal arm motion velocities. CONCLUSIONS: For normal arm motions in the vertical plane, the kinematics of the shoulder skeleton can be derived by the interpolation of statically recorded positions of the bones. RELEVANCE: The 3-D motions of the shoulder are the result of the kinematic constraints of the skeletal system and the coordinated muscle forces, and are only one of the few characteristics that can be quantified. The motions contain relevant information which is essential in the analysis of clinical disorders, e.g. sub-acromial disorders and glenohumeral subluxation, the evaluation of clinical interventions and physiotherapy, and in the analysis of ergonomic and biomechanical problems.

Effects of Unilateral Upper Limb Training in Two Distinct Prognostic Groups Early After Stroke: The EXPLICIT-Stroke Randomized Clinical Trial

Background and Objective. Favorable prognosis of the upper limb depends on preservation or return of voluntary finger extension (FE) early after stroke. The present study aimed to determine the effects of modified constraint-induced movement therapy (mCIMT) and electromyography-triggered neuromuscular stimulation (EMG-NMS) on upper limb capacity early poststroke. Methods. A total of 159 ischemic stroke patients were included: 58 patients with a favorable prognosis (>10° of FE) were randomly allocated to 3 weeks of mCIMT or usual care only; 101 patients with an unfavorable prognosis were allocated to 3-week EMG-NMS or usual care only. Both interventions started within 14 days poststroke, lasted up until 5 weeks, focused at preservation or return of FE. Results. Upper limb capacity was measured with the Action Research Arm Test (ARAT), assessed weekly within the first 5 weeks poststroke and at postassessments at 8, 12, and 26 weeks. Clinically relevant differences in ARAT in favor of mCIMT were found after 5, 8, and 12 weeks poststroke (respectively, 6, 7, and 7 points; P < .05), but not after 26 weeks. We did not find statistically significant differences between mCIMT and usual care on impairment measures, such as the Fugl-Meyer assessment of the arm (FMA-UE). EMG-NMS did not result in significant differences. Conclusions. Three weeks of early mCIMT is superior to usual care in terms of regaining upper limb capacity in patients with a favorable prognosis; 3 weeks of EMG-NMS in patients with an unfavorable prognosis is not beneficial. Despite meaningful improvements in upper limb capacity, no evidence was found that the time-dependent neurological improvements early poststroke are significantly influenced by either mCIMT or EMG-NMS.

The monosynaptic Ia afferent pathway can largely explain the stretch duration effect of the long latency M2 response

Sudden stretch of active muscle typically results in two characteristic electromyographic responses: the short latency M1 and the long latency M2. The M1 response originates from the monosynaptic Ia afferent reflex pathway. The M2 response is less well understood and is likely a compound response to different afferent inputs mediated by spinal and transcortical pathways. In this study the possible contribution of the Ia afferent pathway to the M2 response was investigated. A mechanism was hypothesized in which the M1 response synchronizes the motoneurons, and therewith their refractory periods. Stretch perturbation experiments were performed on the wrist and results were compared with a computational model of a pool of motoneurons receiving tonic and Ia afferent input. The simulations showed the same stretch amplitude, velocity, and duration-dependent characteristics on the M2 as found experimentally. It was concluded that the stretch duration effect of the M2 likely originates from the proposed Ia afferent mediated mechanism.

Electromyography of shoulder muscles in relation to force direction

In a static force task the electromyographic level of 14 shoulder muscles including 3 rotator cuff muscles was related to force direction. Surface and wire electrodes were used. The force direction of maximal electromyography (principal action) was identified for every muscle. The principal action expresses the function of a muscle in a special situation. The deltoid was active in a force direction that could be understood from its anatomy. The trapezius and serratus were mainly involved in stabilizing the scapula in upward and outward force directions. Large multiarticular muscles such as the pectoralis and the latissimus were active in downward and forward forces. The rotator cuff seems to have a specific role in stabilizing the glenohumeral joint. These data can be compared with data of patients with shoulder disorders and with kinematic data of a shoulder model.

Differentiation between non-neural and neural contributors to ankle joint stiffness in cerebral palsy

BackgroundSpastic paresis in cerebral palsy (CP) is characterized by increased joint stiffness that may be of neural origin, i.e. improper muscle activation caused by e.g. hyperreflexia or non-neural origin, i.e. altered tissue viscoelastic properties (clinically: “spasticity” vs. “contracture”). Differentiation between these components is hard to achieve by common manual tests. We applied an assessment instrument to obtain quantitative measures of neural and non-neural contributions to ankle joint stiffness in CP.MethodsTwenty-three adolescents with CP and eleven healthy subjects were seated with their foot fixated to an electrically powered single axis footplate. Passive ramp-and-hold rotations were applied over full ankle range of motion (RoM) at low and high velocities. Subject specific tissue stiffness, viscosity and reflexive torque were estimated from ankle angle, torque and triceps surae EMG activity using a neuromuscular model.ResultsIn CP, triceps surae reflexive torque was on average 5.7 times larger (p = .002) and tissue stiffness 2.1 times larger (p = .018) compared to controls. High tissue stiffness was associated with reduced RoM (p < .001). Ratio between neural and non-neural contributors varied substantially within adolescents with CP. Significant associations of SPAT (spasticity test) score with both tissue stiffness and reflexive torque show agreement with clinical phenotype.ConclusionsUsing an instrumented and model based approach, increased joint stiffness in CP could be mainly attributed to higher reflexive torque compared to control subjects. Ratios between contributors varied substantially within adolescents with CP. Quantitative differentiation of neural and non-neural stiffness contributors in CP allows for assessment of individual patient characteristics and tailoring of therapy.

Study protocol subacromial impingement syndrome: the identification of pathophysiologic mechanisms (SISTIM)

BackgroundThe Subacromial Impingement Syndrome (SIS) is the most common diagnosed disorder of the shoulder in primary health care, but its aetiology is unclear. Conservative treatment regimes focus at reduction of subacromial inflammatory reactions or pathologic scapulohumeral motion patterns (intrinsic aetiology). Long-lasting symptoms are often treated with surgery, which is focused at enlarging the subacromial space by resection of the anterior part of the acromion (based on extrinsic aetiology). Despite that acromionplasty is in the top-10 of orthopaedic surgical procedures, there is no consensus on its indications and reported results are variable (successful in 48-90%). We hypothesize that the aetiology of SIS, i.e. an increase in subacromial pressure or decrease of subacromial space, is multi-factorial. SIS can be the consequence of pathologic scapulohumeral motion patterns leading to humerus cranialisation, anatomical variations of the scapula and the humerus (e.g. hooked acromion), a subacromial inflammatory reaction (e.g. due to overuse or micro-trauma), or adjoining pathology (e.g. osteoarthritis in the acromion-clavicular-joint with subacromial osteophytes).We believe patients should be treated according to their predominant etiological mechanism(s). Therefore, the objective of our study is to identify and discriminate etiological mechanisms occurring in SIS patients, in order to develop tailored diagnostic and therapeutic strategies.MethodsIn this cross-sectional descriptive study, applied clinical and experimental methods to identify intrinsic and extrinsic etiologic mechanisms comprise: MRI-arthrography (eligibility criteria, cuff status, 3D-segmented bony contours); 3D-motion tracking (scapulohumeral rhythm, arm range of motion, dynamic subacromial volume assessment by combining the 3D bony contours and 3D-kinematics); EMG (adductor co-activation) and dynamometry instrumented shoulder radiographs during arm tasks (force and muscle activation controlled acromiohumeral translation assessments); Clinical phenotyping (Constant Score, DASH, WORC, and SF-36 scores).DiscussionBy relating anatomic properties, kinematics and muscle dynamics to subacromial volume, we expect to identify one or more predominant pathophysiological mechanisms in every SIS patient. These differences in underlying mechanisms are a reflection of the variations in symptoms, clinical scores and outcomes reported in literature. More insight in these mechanisms is necessary in order to optimize future diagnostic and treatment strategies for patients with SIS symptoms.Trial registrationDutch Trial Registry (Nederlands Trial Register) NTR2283.