Polycentric Exoprosthetic Knee Joints - Extent of Shortening During Swing Phase.

BACKGROUND: An often assumed advantage of polycentric knee joints compared to monocentric ones is the improved ground clearance during swing phase due to the geometric shortening of the lower leg segment (LLS). OBJECTIVE: To investigate whether polycentric knee joints considerably improve ground clearance and to evaluate the influence of prosthetic alignment on the extent of ground clearance. METHODOLOGY: 11 polycentric and 2 monocentric knee joints were attached to a rigid, stationary testing device. Shortening of the LLS and the resulting ground clearance during knee flexion were measured. Prosthetic components were mounted at the same height and the anterior-posterior position was in accordance with the manufacturer's alignment recommendations. FINDINGS: Shortening of up to 14.7 (SD=0.0) mm at the instance of minimal ground clearance during swing phase was measured. One knee joint elongated by 4.4 (SD=0.0) mm. Measurements of the ground clearance demonstrated differences up to 25.4 (SD=0.0) mm. One monocentric knee joint provided more ground clearance when compared to 8 of the polycentric knee joints investigated. CONCLUSION: Only some polycentric knee joints shorten appreciably during swing phase. With an optimized prosthetic alignment and a well-designed swing phase control, a monocentric knee joint may generate greater ground clearance compared to a polycentric knee joint.

[Function of prosthesis components in lower limb amputees with bone-anchored percutaneous implants : Biomechanical aspects]. / Funktion exoprothetischer Bauteile bei Beinamputierten mit osseointegrierten, perkutan ausgeleiteten Implantaten : Biomechanische Aspekte.

BACKGROUND: Bone anchorage of an artificial limb has been proven to be an alternative intervention for amputees when prosthesis use is seriously reduced because of stump problems. Little is known about how prosthesis components interact with bone and joints and which potential the optimum use provides with respect to quality of treatment of leg amputees. OBJECTIVE: Does osseointegration influence the motor activity of residual limbs differently compared with socket prostheses? How should prosthesis components be aligned? What type of prosthetic knee joints should be preferred in transfemoral amputees? MATERIAL AND METHODS: Transfer of biomechanical knowledge of socket prosthetics to bone-anchored prostheses. Pilot studies with a limited number of amputees. RESULTS: Force transmission at the interface between the prosthesis and residual limb stump is completely different for osseointegrated fixation and socket design; however, the number of muscles available for control remains unchanged. Because the iliotibial tract is missing, bending moments of the femur are expected to be greater. Prosthetic alignment is very critical for gait pattern and the basic rules seem to be the same as for socket design. The foot position determines the knee function for below-knee amputees. The position of the femur influences the gait pattern of above-knee amputees. The lowest risk of falls and best functional properties are shown by microprocessor controlled knee joints. CONCLUSION: Osseointegrated leg prostheses have some biomechanical advantages over the socket design. Since rehabilitation quality is clearly affected the prosthetic alignment has to be done carefully and precisely. As a rule microprocessor controlled knee joints are indicated.

[Changes in the Locomotor System as a Consequence of Amputation of a Lower Limb]. / Veränderungen am Bewegungsapparat als Folge von Amputationen an der unteren Extremität.

Background: It is often assumed that leg amputations result in a greater risk of degenerative changes to the locomotor system. This paper analysed the extent to which this assumption is supported by the scientific literature. In particular, the study analysed the level of risk of various degenerative diseases in amputees. Method: A systematic literature search was conducted in scientific databases on degenerative changes caused by amputations. All pertinent articles were qualitatively analysed; the available quantitative results were summarised and compared to data for the able bodied population. Results: The search yielded 40 publications that met the inclusion criteria. A quantitative summary of the studies showed that 56 % of amputees suffered from back pain, radiographic signs of arthritis were found in the sound knee of 35 % of patients, compared with clinical signs in 33 %. Clinical symptoms of hip osteoarthritis were seen in 15 % of amputees on the prosthetic side and in 20 % on the sound side. 87 % of patients exhibited reduced bone density in the hip on the prosthetic side and all amputees exhibited muscular atrophy in the residual limb. Conclusions: Thanks to the development of prosthetic components it is possible to adjust the length of the prosthesis to the length of the sound limb, so that there are no longer discrepancies in leg length. This means that flexion deformities of the spine of amputees have become rarer and are therefore no longer discussed in the current literature. The risks of back pain, knee osteoarthritis in the sound side, reduced bone density on the prosthetic side hip and muscular atrophy are still significantly greater than in the able bodied population. The prevalence of back pain and knee osteoarthritis increases in more proximal amputations. It may be possible to reduce these risks with novel prosthetic components and by optimising prosthetic fitting. On the one hand, an optimised prosthesis will be used more often. On the other hand, it will be exposed to greater loads and therefore the load to the locomotor system could be distributed more evenly between the two legs. Both aspects would result in a more physiological loading of the locomotor system. There was not enough published evidence to determine to what extent the sound side foot shows degenerative changes.

[Gait-analytical studies in patients treated by valgus tibial head osteotomy]. / Ganganalytische Untersuchungen von Patienten mit valgisierender Tibiakopfosteotomie.

So far, the use of imaging methods has been the only way of evaluating unicompartmental gonarthritis caused by malalignment of lower extremity axes and the results of operative correction. Unfortunately, radiological visualization does not give any information about the actual loads on the joint, i.e.the forces and moments acting on it under dynamic conditions. These can be determined by means of gait-analytical measurements. The authors explain how the anomalous loading that occurs in the knee joint in the case of varus gonarthritis can be calculated and assessed. The mean maximum varus moment of knee joints in a group of patients with varus deformity was 0.74 Nm\kg, which was significantly higher than that in a control group (0.63 Nm\kg). Even after correction of the axes, increased maximum moments--some of them independent of the angle of the knee and of the correction angle--were observed in 30% of the cases investigated. These cases were found to be characterized by a predisposition to revarization. Knee joints in which the preoperative varus moment was significantly high or there was a tendency to under-correction were especially likely to show these features. For these reasons, valgus tibial head osteotomies should generally be performed with slight overcorrection. If the preoperative gait analysis has already confirmed that significantly increased varus forces are in play, a definite overcorrection to about 5 degrees beyond the physiological angle should be the aim.

[Functional results of dynamic gait analysis after 1 year of hobby-athletes with a surgically treated ankle fracture]. / Funktionelle Ergebnisse bei Freizeitsportlern in der dynamischen Ganganalyse 1 Jahr nach operativ versorgten Sprunggelenkfrakturen.

Retrospectively 20 patients with a surgically treated ankle fracture caused by hobby-accidents were examined clinically and radiologically by a score modified to Phillips after 12 months postoperatively. Further they have taken part in a dynamical gait analysis at the same time. A group of 20 healthy adults was used as a control group comparable to age, sex, height and weight. Although 19 patients out of 20 have achieved a good result at the score evaluation and none of them was clinically noticed with any pathological gait, gait analysis has shown a significant slowed gait speed and a decreased stride length. The reduction of the plantarflexor moment at the injured ankle joint immediately following heel contact was yet the most remarkable result of the gait analysis. The changes of gait pattern are interpreted as an adapted and internalized motion pattern caused by pain and behaviour of rest at any time while the mobilisation-phase was going on. It could not document any significant correlation between subjective and clinical parameters and parameters registered by gait analysis. However, a significant correlation of gait-analysed parameters was found between the injured and uninjured side. By dynamical gait analysis it is possible to quantify remarkable gait changes, to obtain objective data, but also to demonstrate asymmetrical loading and motion that were not clinically detectable previously. It follows that it can be relevant to patients with complaints by leading them to specific physiotherapeutical treatment and gait training so that they would be able to carry on their sports-activities again.

[Significance of static prosthesis alignment for standing and walking of patients with lower limb amputation]. / Die Bedeutung des statischen Prothesenaufbaus für das Stehen und Gehen des Unterschenkelamputierten.

The influence of three alignment parameters of a transtibial prosthesis (sagittal foot position, plantar flexion, mediolateral foot position) on the load and motion of the lower extremity joints was investigated in 13 unilateral transtibial amputees. The aim was to determine whether a correlation exists between static prosthetic alignment and gait pattern that would allow an optimal biomechanical prosthetic alignment. The gait pattern was measured using kinematic, kinetic, and electromyographic methods. Statics was defined using the alignment apparatus L.A.S.A.R. Posture. The electromyogram of the m. vastus lateralis and m. biceps femoris was recorded on both sides. The motion of joints is described by joint angles. External joint moments define the mechanical loads. Alignment has almost no influence on muscle activity and joint mechanics of the contralateral leg. In contrast, prosthetic alignment affects clearly and systematically the load and motion of the knee joint during the stance phase on the ipsilateral side. The sagittal foot position influences the maximal flexion angle in the stance phase. The plantar flexion of the foot affects the temporal structure of knee motion. The mediolateral foot position causes correspondingly different varus and valgus moments acting on the knee. Swing phase motion does not depend on prosthetic alignment. The iEMG of the m. vastus lateralis is reduced. Innervation characteristics of the m. biceps femoris on the prosthetically fitted leg has completely changed. The ischiocrural muscles take over the neuromuscular action of the m. gastrocnemius to compensate for the external knee extension moment during the second part of the stance phase. Prosthetic statics determines if the knee joint is physiologically stressed in a standing posture and during walking. Statics will be correct if the anatomical knee axis of the standing amputee is located about 15 mm posterior to the load line in the sagittal plane. In the frontal plane, the load line touches the lateral patella border and strikes the middle of the foot about 5 cm anterior to the adapter. During walking, attention should be paid to performance of knee flexion in the stance phase.

Selective thigh muscle atrophy in trans-tibial amputees: an ultrasonographic study.

In trans-tibial amputees, PTB (patellar tendon bearing) prostheses provide almost physiological mobility of the knee joint in the sagittal plane. Nevertheless, there are characteristic adaptations of the knee joint muscles. Myosonography is a suitable method for depicting muscle atrophy and hypertrophy due to muscle dysfunction. The present study was intended to assess anatomical alterations of thigh muscles in trans-tibial amputees wearing a PTB prothesis. Thicknesses and cross-sectional areas of the quadriceps femoris, sartorius, gracilis, semitendinosus and biceps femoris muscles were determined ultrasonographically on both limbs in 17 amputees with a PTB prothesis. The gait was analysed using an optoelectronical system, force plates and surface electromyography of the vastus lateralis and biceps femoris muscles. Quadriceps femoris and sartorius muscles of the amputated extremity exhibited significant atrophy compared with the contralateral limb (reduction of muscle thickness ranged between 11.7% and 30.4%), whereas the gracilis and hamstring muscles were not significantly affected. Even the quadriceps femoris muscle of the non-amputated limb showed a slight atrophy compared with a reference group. Increased echointensities were found predominantly in the quadriceps muscle on the amputated leg. During gait, electromyographical activity within the amputated limb was reduced in the vastus lateralis and increased in the biceps femoris muscle. Even long-term adaptation to PTB prostheses results in characteristic deviation from normal gait. Atrophy occurs in the ventral thigh muscles, predominantly on the amputated leg, whereas the dorsal thigh muscles are hardly affected, probably due to compensatory hyperactivity.

Effects of sagittal plane prosthetic alignment on standing trans-tibial amputee knee loads.

The influence of sagittal plane prosthetic alignment changes on loads applied to the ispilateral knee was investigated using 5 transtibial amputee subjects. The goal was to determine which prosthetic alignment results in the most energy efficient standing and also minimises stresses on knee structures during standing. The electromyogram, the external mechanical loading of the prosthetic leg and the amputees' posture were recorded for a wide range of prosthetic alignments. The EMG of the vastus lateralis and biceps femoris muscles was measured bilaterally; the EMG of the gastrocnemius muscle was measured only on the contralateral side. The distance between the anatomical knee centre and each individual's load line, as determined by the Otto Bock "L.A.S.A.R. Posture" alignment system, was used as a measure of the mechanical load applied to the knee joint. Prosthetic alignment has almost no influence on muscle activity of the contralateral lower limb during static standing. On the other hand, prosthetic alignment has a significant influence on the load applied to the amputee's ipsilateral knee joint. The external knee moments applied to the knee ligaments and knee muscles on the amputated side change systematically in response to different plantar flexion or dorsiflexion angles of the prosthetic ankle-foot. During standing the extensor muscles stabilise the limb by contracting if the load line is located less than 15 mm anterior to the anatomical knee centre. The biceps femoris muscle appears to have little or no protective function against hyperextension during standing even if large external knee extension moments are caused by excessive plantar flexion. Such extreme alignments significantly increase the stresses on knee ligaments and the posterior knee capsule. When prosthetic sagittal plane alignment is altered, the trans-tibial amputee compensates by balancing the upper part of the body over the centre of pressure of the prosthetic foot. Biomechanically optimal alignment of the trans-tibial prosthesis occurs when the individual load line is approximately 15 mm anterior to the anatomical knee centre, permitting a comfortable, energy efficient standing and minimising the mechanical loading on the knee structures.

[Evaluation with biomechanical gait analysis of various treatment methods after rupture of the anterior cruciate ligament]. / Biomechanisch-ganganalytische Bewertung verschiedener Behandlungsmethoden nach Ruptur des vorderen Kreuzbandes.

The purpose of the present study is to evaluate the rehabilitation of different treatments of ACL ruptured knees by means of gait parameters. The gait analysis results in two surgically treated patient groups (patellar tendon autograft reconstructions (n = 35) and augmented repairs (n = 15) and one non-surgically treated patient group (n = 19) are evaluated by means of gait parameters of normal controls (n = 30). The technical equipment included an optoelectronic system for recording the kinematics of gait (Primas, NL) and two force plates for measuring the ground reaction forces (Kistler, CH). The moments acting on joints can be determined experimentally with both systems. It can be shown from special gait tests that the derived quantitative evaluation parameters are independent from the gait analysis conditions. One year after surgery, both the patellar tendon autograft reconstruction group and the augmented repair group show clear deficiencies in gait parameters compared with the controls. In particular this concerns the midstance extension motion of the knee (p < = 0.01) and the extension moments acting on the knee joint during the stance phase (sagittal plane, p < = 0.01). The deficiencies of both surgically treated groups are approximately the same. However, one year after occurrence of the disruption the non-surgically treated group cannot be distinguished from the controls. From this and from additional pre-surgical measurements, it can be concluded, that operating has an important influence on gait parameters. The role of the gait analysis results has been discussed.

A new biomechanical method for determination of static prosthetic alignment.

A new static alignment method for trans-tibial prostheses is suggested using the individual load line as a reference. Standing posture and static alignment of 18 experienced trans-tibial prosthetic users with good walking ability were determined and compared with 20 healthy persons. The individual load line was defined by means of the new Otto Bock alignment system "L.A.S.A.R. Posture". The sagittal standing posture of trans-tibial amputees and non-amputees differs. Normally only a prosthesis worn by the trans-tibial amputee and dynamically aligned over an extended period of time satisfies biomechanical rules of alignment. In contrast, prostheses aligned during one session in the traditional subjective manner seem to lack any recognizable biomechanical systematics. Initial results suggest the knee centre should be 10 to 30mm behind the load line, depending on patient's weight. This knee position is independent on the type of prosthetic foot.

[Determination of the elasticity of the femoral cortex of Adam's arc in patients with osteoarthritis]. / Ermittlung der Bruchfestigkeit der Femurkortikalis am Adam'schen Bogen bei Patienten mit Osteoarthrose.

In this study, the compressive strength, the compressive force as well as cortical thickness of prismatic specimens from Adam's arc of the femur were determined in patients with osteoarthrosis. Correlations were evaluated between the cortical bone parameters, which depend on age and sex. Supported by histomorphometric data of cancellous bone, the great variability of mechanical properties revealed the variable osteological status prior to implantation of hip endoprostheses. Its eventual consequences for alloarthroplastic surgery had been discussed.

Importance of morphological findings in the progress and treatment of chest wall deformities with special reference to the value of computed tomography, echocardiography and stereophotogrammetry.

Patients with chest wall deformities have many particular anatomical, physiological, genetic, biomechanical and psychological characteristics. It is generally recognized that surgical correction of funnel chest and pigeon breast may be done for psychosocial reasons alone. Morphological and dynamic investigations are done to identify the function of the deformed chest wall and to permit objective assessment of the cosmetic and functional outcomes of the operation. There is no universally agreed standard for the diagnosis of funnel chest and pigeon breast. Non-invasive investigations, such as computed tomography (CT), echocardiography (ECG) and stereophotogrammetry (SP), improve the quality of the diagnostic assessment, including evaluation of its functional aspects, without directly influencing the decision to operate, which is still made mainly on subjective grounds. The value of these techniques in the diagnosis of chest wall deformities is assessed and the results of our personal experience are presented.

[The relationship between the gait of humans and the hip joint structure in the frontal plane]. / Die Beziehung zwischen dem Gang des Menschen und dem Hüftgelenkaufbau in der Frontalebene.

The forces at the hip joint acting between the femur head and acetabulum are significant for the function properties a lifetime. These forces are determined by the geometry of skeleton and the dynamic of limbs motions. The interaction of hip joint anatomy, gait dynamics, and joint force is described biomechanically. The connections are verified by 35 adults. The results of this investigation allow to conclude that individual variants of macroscopic hip joint anatomy are founded by the relation between maximum loading during gait and hip joint structure. The correlation between the angle of weight-bearing-surface and the hip joint force direction is very significant. For a normal hip joint function, the anatomical structure of the acetabulum is essential more important as that of the coxal femur.

[Biomechanical construction principles of the human hip joint in frontal plane]. / Biomechanische Bauprinzipien des menschlichen Hüftgelenkes in der Frontalebene.

The prognosis of hip joint function is only to determine unsatisfactory on the base of the knowledges of anatomy by means of inspection or angles and distances from X-rays as well as on the base of models known for the biomechanic of hip. The term "normal anatomical" hip structure is analysed with respect to functional biomechanical influences on its macroscopic design in frontal plane. It is shown to interpret the macroscopic hip design as result of an effective arrangement of centre of rotation and muscle forces which a minimum on energy needing for its function. A mathematical equation describes the skeleton-muscle-system hip biomechanically. This new connection between angles and distances as well as first easy consequences are proofed on a-p-hip radiographs of 53 normal adults.