[Experimental investigation on the reproducibility of ensemble-averaged electromyographic gait analysis data in the area of experimental and clinical orthopaedics]. / Experimentelle Untersuchungen zur Reproduzierbarkeit von Ensemble-gemittelten elektromyographischen Ganganalysedaten im Bereich der experimentellen und klinischen Orthopädie.

With suitable application and signal processing methods, surface electromyography is a comparatively simple instrument for investigating the temporal pattern of the muscular activity of a walking subject. The influence of changes both in the external experimental conditions (e.g. orthopedic shoe design) and in the human locomotor system (due to disease or therapy) on the individual muscular gait characteristics can be documented in this way. The usefulness of this kind of investigation is basically limited by the reproducibility of the gait analytical findings of the subject, who is examined at different times with unchanged bodily state and under identical experimental conditions unchanged. In our experiments we observed that the reproducibility of electromyographic activity curves obtained by ensemble averaging over a sufficiently high number of full strides differs for different muscles and in different subjects. Within the same experimental session it is very high and considerably better than in experiments done on different days. In examinations done on different days the basic characteristics of the activity curves are reproduced better than the absolute height of the amplitudes. In view of these findings the differences observed in the gait analysis of patients in the course of operative or conservative therapy have to be interpreted very carefully as to their true origin.

Ensemble averaging and multiple statistical testing of EMG activities of cyclically repeated body motions. A tool for muscle function analysis in experimental and clinical orthopaedics.

Coupled with suitable computerized signal recording and processing methods surface electromyography can be a powerful tool for the analysis of muscle activity in specific body movements. It can be used for this purpose in experimental and in clinical diagnostic orthopaedics as well as in physiotherapy. We describe in this paper a motion analysis system comprising this feature. It has been employed for the diagnosis of the basic angular kinematics and muscle function in human gait and other cyclically repeatable movements of the human locomotive system. Changes in the temporal characteristics of the movements and the muscle activity due to changed physical or experimental conditions can be systematically investigated this way. Such changes can be the result of surgical and/or conservative orthopaedic therapy, a long term physiotherapeutic program, or modified walking conditions as in experimental orthopaedics. They are displayed and validated by signal ensemble averaging and subsequent multiple statistical testing (e.g. by a suitably adapted Bonferroni criterion). The efficiency of the system is demonstrated by an exemplary gait analysis of selected kinematic and muscular effects caused by an experimental simulation of a leg length inequality.

[Kinematic analysis before and after bicondylar resurfacing knee arthroplasty]. / Kinematische Analyse vor und nach bikondylärem Oberflächenersatz des Kniegelenks.

Knee joint motion appears as a hinge movement around the flexion-extension axis. Corresponding to the rolling-sliding mechanism and alternative models of knee joint kinematics, an instant center pathway must be expected. The current photogrammetric investigation aimed to analyze these pathways when assessed in the sagittal plane in patients with preoperative varus or valgus deformity. A total of 40 patients either with varus or valgus deformity (20 in each group) were examined before and 6 months after implantation of PFC-SIGMA prostheses. Apart from the influence of knee joint deformity, a so-called soft tissue ratio was investigated. Therefore, the relation of thigh and femur as well as lower limb and tibia diameters was calculated and combined in one value. The investigation unit consisted of a standardized chair with passive knee joint movement (90-0 degrees flexion) supported by an electric motor. The position of predefined skin markers was assessed by digital camera with online transmission to a PC. The instant center pathway was then evaluated applying the Reuleaux technique based on the changes of skin marker positions. Results showed the following characteristics: small values of soft tissue ratio were represented by round or oval courses of the pathway whereas increasing ratios led to triangular and slightly increased dimensions of the courses. Varus deformity was primarily combined with an increase of the pathway's dimension and in contrast, valgus deformity showed decreased pathways. In each case, dimensions normalized after prosthesis implantation. The instant center pathway of knee joint motion showed for both patient groups characteristic phenomena. They were clearly associated with constitutional and clinical features of each patient.

[Photogrammetry of knee joint kinematics after hinge arthroplasty]. / Photogrammetrische Untersuchung des Kniegelenks nach Implantation von Scharnierendoprothesen.

Hinge prostheses are the oldest total knee arthroplasties based on the easiest model of knee joint kinematics. The complex knee joint movement is simplified by a hinge rotating around the flexion-extension axis. Nevertheless, different studies showed that in unscathed joints an instant center pathway in the sagittal plane must be expected. The objective of the current photogrammetric investigation was the assessment of these pathways after hinge arthroplasty. Moreover, they were compared with reference pathways from healthy participants. A total of 20 patients were examined on average 12.1 years after implantation of St. Georg hinge prostheses. Apart from this, 50 test persons with unscathed knee joints were investigated. The examination unit consisted of a standardized chair with passive knee joint movement (90-0 degrees flexion) supported by an electric motor. The position of predefined skin markers was assessed by digital camera with online transmission to a PC. The instant center pathway was then evaluated applying the Reuleaux technique based on the changes of skin marker positions. Patients with hinge prostheses showed small pathways almost comparable to dots. Apart from this, courses of the pathways depended on the extent of soft tissue in the knee joint area. Small values were associated with round or oval courses,whereas increasing soft tissue led to triangular and slightly increased dimensions of the courses. Pathways of the reference participants confirmed this observation and additionally showed clearly greater dimensions of the pathways. The instant center pathway of unscathed knee joints showed a dependence of the course on the extent of soft tissue. The same observation was made in patients with hinge prostheses. Moreover,the latter were characterized by very small, almost fixed pathways. These results confirm the neglect of additional movement components in hinge prostheses.

[Kinematic changes after bicondylar resurfacing knee arthroplasty]. / Anderung der Kniegelenkskinematik nach bikondylärem Oberflächenersatz.

AIM: Knee joint motion appears as a hinge movement around the flexion - extension axis. But corresponding to the rolling-sliding-mechanism and alternative models of knee joint kinematics an instant center pathway must be expected. Objective of the study was the comparison of this pathway when assessed in the sagittal plane in patients with preoperative varus or valgus deformity. METHOD: A total of 40 patients either with varus or valgus deformity (20 in each group) were examined before and 6 months after implantation of PFC(R)-SIGMA prostheses. Apart from the influence of knee joint deformity (35 degrees varus to 24 degrees valgus), a so called soft tissue ratio was investigated. Therefore the relation of thigh and femur as well as lower limb and tibia diameters was calculated and combined in one value. The examination by means of photogrammetry consisted of a standardized chair with passive knee joint movement (90 degrees to 0 degrees flexion) supported by an electric motor. The position of defined skin markers was assessed by digital camara with online transmission to PC. The instant center pathway was then evaluated applying the Reuleaux-technique based on the changes of skin marker positions. RESULTS: Results showed a dependence of the course and dimension of the instant center pathway on the extent of soft tissue ratio as well as knee joint deformity. Small values of the ratio (W = 2.9) were represented by round or oval courses of the pathway whereas increasing ratios (W = 4.0) led to triangular and slightly increased dimensions of the courses. Varus deformitywas primarily combined with an increase of the pathways dimension and in contrast, valgus deformity showed decreased pathways. In each case, dimension normalized after prostheses implantation. CONCLUSION: The instant center pathway of knee joint motion showed for both patient groups characteristic phenomen. They were clearly combined with constitutional and clinical features of each patient.

[Function of back extensor muscles in upright standing position and during sitting with identical back posture--an electromyography study]. / Die Aktivität der Rückenstreckmuskulatur beim aufrechten Stehen und beim Sitzen mit standidentischer Rumpfhaltung--eine elektromyographische Studie.

PROBLEM: There is a controversial discussion about the loading of the spine by the force of the extending muscles of the back in upright sitting with the back curved as in upright standing. Experimental studies investigating this issue are still lacking. METHODS: In the study presented in this paper we measured in 30 subjects the activity of the extending back muscles both in a natural upright standing posture and in sitting with identical posture of the back as recommended in some back training programs. To this end we recorded the electromyographical surface activity of the back muscles at four levels of the spine in both postures. The EMG activities were intraindividually normalized with reference to the respective activity recorded at maximum voluntary isometric contraction (MVC). RESULTS: At three of the four levels of the spine examined, the group averages of the EMG activity in sitting were significantly higher than in standing (p < 0.001). The maximum activity enhancement evaluated was 48% at Th12. The force of the lower back muscles in sitting with a posture of the back as in natural upright standing could be estimated to be at least greater than 30% of the force at MVC. CONCLUSION: The force needed to enforce in sitting a posture of the back identical to the posture at natural standing entails lower back muscle fatigue in a few minutes. The results of our study agree with recent experimental findings about an increased loading of the spine in lordotic sitting.

[Measurement of migration of acetabular components in cementless hip replacement]. / Messung der Pfannenwanderung bei zementfreien Hüftimplantaten.

PURPOSE: Migration measurements of acetabular components using a special computer aided method (EBRA = abbreviation for the German term "Ein-Bild-Röntgenanalyse") were performed to evaluate early results of the implants and predict aseptic loosening. METHODS: Standard ap-radiographs of the pelvis were marked, specific points were digitised. Simulating the spatial situation the programme computes longitudinal and vertical migration of the cup. 74 acetabular components in 71 patients could be studied by migration measurements. RESULTS: 14 patients showed migration of more than 1 mm, which is the confidence limit of this method. Each of these patients showed diverse reasons for the migration, i.e. osteoporosis of the acetabular bone stock or problems concerning the surgical technique which means malposition of the cup or insufficient reaming of the bone. There were some patients with severe congenital dysplasia of the hip and in some cases the inclination angle of the cup was too great. CONCLUSION: The technique applied for measuring migration of acetabular components can be useful for evaluating early instability of the implant and can be helpful in detecting problems concerning the surgical technique.

Gait analysis in idiopathic scoliosis before and after surgery: a comparison of the pre- and postoperative muscle activation pattern.

In a prospective experimental study the level gait activity scores of the iliocostalis lumborum, glutaeus medius, tensor fasciae latae, vastus lateralis and peronaeus longus muscles of both body sides were examined by computerized electromyography in 23 patients with idiopathic scoliosis before and after CD instrumentation. The pre- and postoperative findings were examined as to asymmetric patterns in muscle requisition during gait and the respective changes induced by the spinal correction. These results were compared with the corresponding results obtained in healthy subjects in two independent sessions with identical experimental conditions. A muscle activity asymmetry coefficient was defined to quantify the degree of left/right muscle activation asymmetry observed. Postoperatively a statistically significant reduction (P < 0.05) of a preoperatively strongly increased activity was found in the lumbar muscles of the convex side of double major scolioses as well as in the glutaeus medius and tensor fascia lata muscles of the concave side of thoracic curvatures. Both the casuistic and statistical analysis of the results of our study support the hypothesis that activity asymmetries observed in the paravertebral musculature in idiopathic scoliosis patients are the result of the scoliotic body deformities, with consequent asymmetries in the biomechanical force patterns of body postures and body motions, rather than an aetiological factor of scoliotic curvatures.

Maximal power and EMG of lower limbs after 21 days spaceflight in one astronaut.

Long term space flights affect negatively muscle structure and function (Grigoriev end Egorov, 1901, 1902; Edgerton and Roy, 1994; Jaweed, 1994; Nicogossian, 1994a; Antonutto et al., 1995, Edgerton and Roy, 1997), essentially because of the long-term exposure to microgravity. Indeed, we have previously shown that the average power developed during a very short (approximately 0.25 s) maximal effort of the lower limbs, such as a vertical jump off both feet ("maximal explosive power", MEP) was reduced to 67% of pre-flight values after one month in microgravity (one subject) and to 45% after six months (three subjects). The reductions of MEP was larger than the concomitant decrease of muscle mass (9 to 13%, Zange et al., 1997). This suggests that a substantial fraction of the decrease of maximal power is due to the deterioration of the motor control, brough about by the absence of gravity. The aim of the present study was to investigate further the effects of microgram on maximal muscular power assessing also the EMG activities of 3 heads of the quadriceps femoris muscle, which contributes the major share of MEP.

The influence of lateral release on patello-femoral joint loading in knee arthroplasty. An experimental in vitro study.

Eight fresh, cadaveric knees have been fitted with four different total knee cemented prostheses. Loading forces at the bone implant fixation interface of the patella component have been measured in a knee joint testing rig by four miniaturized force transducers, before and after a lateral release of the patellar retinaculum. The lateral release resulted in a significant local force reduction in the lateral and/or proximal quadrant of the patella resection plane depending on the knee flexion angle, quadriceps tensile force direction, and the patellar prosthesis design.

The effect of cement fixation on initial micromotion of the femoral component in condylar knee replacement.

Four fresh, cadaveric specimens were fitted with total knee replacements and mounted on a knee joint loading and measuring rig. Femoral component micromotion in the sagittal plane was measured with a transducer during flexion and extension of the specimen. Various condylar designs were used without and with cement. Movement followed a characteristic curve pattern and was less with cement fixation particularly for bone of low trabecular strength as determined by bone sample tests for stiffness. Cement fixation appears to be superior to cementless fixation.

The deltoid muscle: an electromyographical analysis of its activity in arm abduction in various body postures.

We have carried out an electromyographical examination of the activity of five different regions of the deltoid muscle during abduction/adduction in various body postures with different biomechanical actions of arm gravity. The results show that the deltoid action is highly differentiated in its different regions and is not restricted only to the generation of an abducting moment in the shoulder joint. There is obviously a biomechanical contribution, mainly by its spinal and clavicular regions, to the stabilization of the glenohumeral joint and to the control of the selected plane of abduction.

[Stress on the Achilles tendon in Alpine skiing]. / Zur Achillessehnenbelastung im alpinen Skisport.

In an attempt to gain more systematic knowledge of the biomechanical mechanism involved in the genesis of injuries caused by a fall during skiing, we undertook a comprehensive analysis of more than 100 experimental ski falls simulated under controlled conditions. The well-known relation between speed, release time of the ski binding and injury risk of the lower extremity was confirmed by our experimental results. The EMG investigations revealed the central importance of the musculus triceps surae, and hence of the Achilles tendon, during a fall. The results of our biomechanical model indicate that the present method of setting the ski binding according to the tibial strength, is rather questionable, to say the least.

[Mechanics as a basic physical discipline in orthopedics and traumatology]. / Die Mechanik als physikalische Grundlagendisziplin der Orthopädie und Traumatologie.

Among the various relationships between fields of the clinical medicine and fields of physics, the relationship between orthopaedics and traumatology and mechanics is of a particularly close and manifold nature. We try to present in this contribution a description of the physical principles of mechanics and to give a survey of its various fields of application in orthopaedic and traumatologic basic research.

[Use of a computer-controlled kinematic-electromyographic motion analysis system to investigate gait patterns of healthy subjects on the level walkway and the treadmill (author's transl)]. / Anwendung eines computergesteuerten kinematisch- elektromyographischen Bewegungsanalysesystems zur Untersuchung des Gehverhaltens gesunder Probanden auf der Laufstrecke und auf der Rollgehbahn.

In an attempt to clarify the question if the level walkway and the treadmill present comparable conditions for analytic examinations of the human gait we investigated in either situation with a computer-controlled motion analysis system some kinematic and electromyographic aspects of the gait pattern of 20 healthy subjects. The results show that on the treadmill certain kinematic events in the time pattern of the gait cycle are shifted towards the beginning of the full stride. Moreover, in the treadmill walk the amplitude of the angular motion of the thigh is diminished in the forward and enhanced in the backward direction, while the angular amplitude of the shank is diminished in either direction. As to the electromyographic results, we found in the treadmill walk a prolonged activity of the gluteus maximus, and adductor magnus, the semitendinosus, and the gastrocnemius muscle. These results show that there may exist significant kinematic and electromyographic differences between the treadmill and the normal level walk. This fact has to be considered whenever a treadmill is considered for gait analytical investigations.