[Orthopedic made-to-measure shoes for diabetics. Long-term 5-year outcome]. / Orthopädische Massschuhversorgung bei Diabetikern: 5-Jahres-Outcome.

For patients with diabetes mellitus and diabetic foot syndrome customized orthopedic shoes represent the most effective treatment to avoid foot ulceration and amputation. A total of 53 patients suffering from diabetes and treated with customized orthopedic shoes for more than 5 years were included in the study. Of the patients 91% had peripheral artery occlusion disease, polyneuropathy and diabetic neuropathic osteoarthropathy (DNOAP) and in nearly 25% amputation of one limb had already been carried out. The incidence of ulcers over a time period of 5 years was assessed from the patient records and questioning the patients. Questions on the duration of wearing orthopedic shoes, the durability of the shoes and resulting pain were also included. All patients except for one had problems walking on uneven surfaces. Of the patients 89% claimed to have used their shoes always or nearly always and 25% of the shoes had to be replaced after 1 year. The incidence of ulcers was 38% after 5 years. Treatment with customized orthopedic shoes is an effective method to prevent ulcers and amputation. To be successful it is necessary to control that the shoes are made correctly. Not all shoes last as long as 2 years.

Plantar pressure reduction in step-to gait: a biomechanical investigation and clinical feasibility study.

BACKGROUND: Protection of the foot may necessitate reduction of peak pressures in specific plantar regions. The study focuses on the unloading effects that exercising step-to gait may have. METHODS: 20 healthy volunteers were recruited and completed three pedobarographic examinations measuring peak pressures in different gait patterns: normal, half-step length, step-to gait with normal step length on the leading side and zero step length on the trailing side--all gait patterns with an individual but constant cadence. To test clinical feasibility 10 diabetic-neuropathic patients were studied in normal and step-to gait without any restrictions regarding speed or cadence. FINDINGS: Volunteers exercising step-to gait exhibit a significant (P<1%) reduction of peak pressures under the heels and central metatarsals by 9% and 67% on the leading side and of 32% and 19% on the trailing side, respectively. In the diabetic-neuropathic patients unloading effects of the same magnitude but less significant were observed. INTERPRETATION: Reduction of speed reduces peak pressures in all plantar regions. Asymmetry of step patterns reduces peak pressures in the heel and forefoot regions of that foot where heel strike and push-off are suppressed, respectively. However, pressures on the contralateral side are increased. The result is an asymmetric distribution of pressure that is reduced in all regions. Step-to gait may be an option, if pressure protection is required in selected plantar regions. This is confirmed by a feasibility study done with diabetic-neuropathic patients. Protection of the foot, however, is balanced at the cost of harmony of gait, impeding clinical application.

[Changes in shape and size of the foot during pregnancy]. / Form- und Grössenveränderungen des Fusses während der Schwangerschaft.

Many women report an increase in foot size during their pregnancy. Our objective was to verify this anecdotal evidence. In an initial survey of 21 mothers in 2 Münster nursery schools we found a tendency towards an increase in foot size during pregnancy. We therefore developed a measuring system to measure changes in foot length, width, height and volume. A total of 40 women recruited from the antenatal clinic of the University Hospital of Münster and a participating practice were seen three times during their pregnancy. The results were analysed using the Wilcoxon test. We found a statistically significant increase in foot length, width and volume, whereas foot height decreased slightly. This difference was, however, not significant. Especially in diabetic women with polyneuropathy it is important to pay attention to shoe size to prevent pressure sores.

[The influence of proprioceptive insoles (Bourdiol) on the sagittal curvature and inclination of the trunk]. / Der Einfluss neurologischer Einlagen nach Bourdiol auf die Rumpfhaltung.

Proprioceptive insoles rely on the concept of Réné-Jaques Bourdiol, a French neurologist. The aim is to modulate plantar surface sensibility and to influence posture and statics of patients: it is hypothesized that the effect of modified afferent sensory input through proprioceptive stimulation of terminal muscle chains will have either a relaxing or stimulating effect on the whole body, which may be realized by affecting the posture. Small pads with a thickness of typically 1-3 mm are embedded into the insole to provide a specific stimulation. In fitting the insoles selectively to the individual patient the effect of the insoles on the trunk posture is taken as a feedback. This study investigates the influence of proprioceptive insoles on the sagittal curve in 20 selected patients. The protocol used a repeated measures research design. The measures of the sagittal curve were obtained using raster stereography. The four different conditions were: (1) barefoot, (2) convenient shoes without the insoles, (3) the same shoes with a placebo insole, and (4) the same shoes with neurological insoles. Evaluation of raster stereographs provided the kyphotic angle between T4 and T12 and lordotic angle between T12 and S1. Statistical evaluation was performed with the t-test for paired measurements. No significant differences were found in the sagittal profile. Only trunk inclination in normal posture was found to yield a significant difference (0.38 degrees) between placebo and neurological insoles. However, no clear statement on the efficiency of neurological insoles can be made.

[The influence of the C-leg knee-shin system from the Otto Bock Company in the care of above-knee amputees. A clinical-biomechanical study to define indications]. / Einfluss des C-Leg-Kniegelenk-Passteiles der Fa. Otto Bock auf die Versorgungsqualität Oberschenkelamputierter. Eine klinisch-biomechanische Studie zur Eingrenzung von Indikationskriterien.

The C-Leg microprocessor-controlled knee-shin system for the above-knee amputees is introduced as a dramatic improvement over all other prosthetic knees. This is due to its combination of on-board microprocessor and the hydraulic controls acting both on the swing and stance phase. A more secure, natural and efficient gait is expected. Following the recommendations of Otto Bock the indications for the prescription of the C-leg are: Amputees with mobility level "able to walk outdoors without limitations" (AK3) and "able to walk outdoors without limitations plus engage in high performance activities" (AK4) if they face at least one extra obstacle as listed in the Otto Bock catalogue of indications. In this article it is aimed to critically review the indications for the C-leg. In particular the question is posed, whether a different or sophisticated indication of mobility levels might be suggested. Therefore this study does not concentrate on the 3C-100 C-Leg((R)) component but on the system patient + C-leg. So the testing is done by comparing the C-Leg against the regular knee, which is assumed to be an adequate choice for this patient and to which he is accustomed. So far 25 patients with activity levels AK 2 (5), AK 3 (13) and AK 4 (7) have participated in the study. 23 patients, i.e. all patients except one AK 2 and one AK 3 exhibit functional improvement at least according to one criterion. On the other side, only three patients (2 AK 4), fulfill all criteria of functional improvement, which have been defined for this test. It is concluded, that multi-handicapped patients of all activity levels generally experience substantial improvement due to this system. AK 2 patients may show significant functional improvement. As a prerequisite, however, they must not exhibit deficiencies regarding stump movement, muscular status or cognitive abilities. Active patients (AK 3 and AK 4) benefit in the majority of cases. However, some highly active patients of AK 4 complain about interferences between their intended movement and the microprocessor control of knee movements.

[Reduction of plantar peak pressure by limiting stride length in diabetic patients]. / Verringerung des plantaren Spitzendrucks beim Diabetiker durch Verkürzung der Schrittlänge.

Plantar peak pressure is a diagnostically significant parameter for the evaluation of the risk of foot ulceration in patients with diabetic neuropathy. The prophylaxis and therapy of the diabetic foot therefore is to a large extent oriented on peak pressure, and is aimed at an extensive reduction in this parameter. This is mainly accomplished with protective footwear including shoe modifications and cushioning. In comparison, other approaches affecting the loading and motion pattern of the patient are of minor importance--as for example control of gait pattern. In this study we examined shortening of stride length as a possible measure in reducing plantar peak pressure during gait. In 17 diabetic patients without acute foot ulcerations, stride length was reduced to 33% of leg length using an elastic hobble. This led to a reduction in stride length of 23%. At the same time, the walking speed was significantly reduced by 27% and the cadence by 5.7%. As a consequence, the peak pressure was reduced in nearly all regions of the foot--except the small toes. In the metatarsal region peak pressure is reduced by 14.5%. Thus, a reduction in stride length offers the possibility of reducing plantar peak pressure as a supplementary measure in addition to orthopaedic footwear. However, at present clinical feasibility has not yet been established.

[Effect of weight load and carrying conditions on plantar peak]. / Der Einfluss von getragener Last und Tragetechnik auf den plantaren Spitzendruck.

Knowledge is limited regarding the effects exerted by carrying a load on the distribution of plantar peak pressures. It is unknown whether a special technique might exist which keeps peak pressures low when carrying a load. This question is important to diabetic neuropathic patients at risk for tissue damage and pressure ulcerations and therefore with a need for minimized plantar peak pressures. The study included 19 healthy volunteers (14 M, 5 F, mean age: 34.2+/-15.2 years). They walked three times each along a 7-m walkway with an EMED pressure measurement platform under five different carrying conditions. The conditions were: carrying no load (reference), carrying a load of 20 kg in a backpack, carrying a load of 20 kg in a waistcoat, and carrying 20 kg in two bags. A fifth condition, carrying a waistcoat with a load of 10 kg only,was used to check the linearity of peak pressure and weight. Velocity and step length were measured to check the gait parameters. Peak pressures were determined in six regions: large toe, small toes,metatarsals, lateral and medial midfoot, and heel. In agreement with the literature, the reference measurements showed peak pressure to be widely independent of body weight. On the other hand, a significant increase of peak pressure was observed in a single person when a carried load was added. In the regions of the large toe,metatarsals, and heel the peak pressure increased linearly with the carried weight and amounted to 0.54, 0.76, and 0.38 N/cm(2) per kg additional load, respectively. No significant difference between the various techniques of carrying was detected. The plantar peak pressure increases with weight load,however, this is independent of the way the load is carried. No specific recommendation on the technique of carrying a load can be given in order to take care of diabetic feet.

[Effect of body weight on plantar peak pressure in diabetic patients]. / Der Einfluss des Körpergewichts auf den plantaren Spitzendruck beim Diabetiker. Untersuchungen mit simulierter Gewichtsveränderung.

The goal was a better understanding of the correlation between body mass and plantar peak pressure in patients with diabetic neuropathy. A further aim was to obtain insight into the practicability of simulated weight increase and weight release and to delineate more clearly the indications for reducing body weight in order to lower the risk of ulcerations. Simulated change of body weight: (1) +20 kg by a waistcoat and (2)-20 kg by a movable overhead suspension. While normal forces and thus mean normal pressures depend directly on body mass, this does not necessarily apply to peak normal pressures. As shown in a transversal study by Cavanagh with pressure measurements in the bare foot, there is only a poor correlation between body mass and peak pressure. Therefore, peak pressure in heavy persons cannot be expected to be higher than in lighter weight persons. However, from these results it cannot be concluded that peak pressure is likely to remain unchanged irrespective of a change in body weight in a specific subject. Ten subjects were investigated: five controls and five patients suffering from diabetes without neuropathy or preceding ulcerations. All subjects wore the same kind of ready made shoes with ready made standard fitting insoles of cork. Each subject was measured in three modes of weight simulation: normal weight,20 kg weight increase (waistcoat with weight pieces), and 20 kg weight release. Weight release was effected by a modified rescue harness attached to an overhead suspension rail with 6m free walking distance. Individual alignment of the waistcoat and the suspension was checked by a force platform. In-shoe pressure measurement was done with the PEDAR in-shoe system (by Novel, Munich,Germany). For data analysis with the PEDAR standard software only peak pressures were considered. The foot was divided into six regions, particularly metatarsal region and heel. No significant difference between diabetics and controls was found. In the regions at highest risk (metatarsals and heel),peak pressure increased and decreased with weight. In the combined group (n=10), a simulated weight loss of 20 kg decreased metatarsal peak pressure by 5.4+/-1.9 N/cm(2), a 20 kg weight gain increased it by 7.4+/-5.1 N/cm(2). Therefore, without a significant deviation from linearity, peak pressure was found to be a linear function of weight. The results of this study show that weight increase or weight loss in the individual patient has an effect on the plantar peak pressure. The effect is significant in the metatarsal and heel regions. The linearity allows for a simple method of predicting the effect of weight loss by inverting the effect of simulated weight gain.

[Effect of walking speed on pressure distribution of orthopedic shoe technology]. / Der Einfluss der Geschwindigkeit beim Gehen auf die Druckverteilung bei orthopädieschuhtechnischer Versorgung.

Lesions to the diabetic foot have various causes. However, there is broad consensus that excessive plantar pressure plays a major role in the chain of events leading to ulcerations and gangrenes. During walking, on the other hand, peak values of plantar pressure are likely to increase with velocity even in therapeutic shoes. Therefore, the question arises whether a moderate velocity should be recommended to diabetic patients to reduce the risk of foot lesions. In this study, two velocities were compared for different types of therapeutic footwear. The velocities selected were considered moderate (0.7 m/s) and normal (1.3 m/s) for diabetic patients. A specially designed mathematical algorithm (velocity normalization) provided the pressure distributions from a common set of measurements: seven trials at different velocities for each subject and each type of footwear. Ten test subjects with healthy feet were studied. The shoes were ready-made and all had a midfoot rocker. The following four conditions were tested: flexible or rigid outsole respectively in combination with a flat insole or molded foot bed respectively. Pressure distribution measurements were performed with the Pedar in-shoe system, and the Pedar software package was used for analysis. The foot was divided into six regions: first toe, second to fifth toes, metatarsal region, medial midfoot, lateral midfoot, and heel. Only peak pressures were taken into account. Gait velocity was found to have an effect on plantar pressure distribution, mainly in the toes and heel region. Peak pressure in the heels increased significantly by about 20%. In the toe region, the increase was about the same, but was not statistically significant. At a higher velocity, pressure even slightly decreased in the midfoot region. The percentage variation was similar for all four conditions. Thus, walking slowly prevented the foot from high peak pressures, and the combination of rigid outsole and molded foot bed was best suited for both slow and higher velocities.

[Functional rasterstereographic images. A new method for biomechanical analysis of skeletal geometry]. / Rasterstereographische Funktionsaufnahmen. Eine neue Methode zur biomechanischen Analyse der Skelettgeometrie.

Video rasterstereography has been developed for optical back shape measurement and for biomechanical analysis of spinal and pelvic geometry. Analysis of one single measurement permits 3-dimensional reconstruction of the back surface and calculation of shape parameters including pelvis tilt and torsion. In addition, estimates of the lateral deviation of the spinal midline and of vertebral rotation are provided. Its extended analytic potential makes rasterstereography a very appropriate tool for functional examinations. The term "functional examinations" refers in this context to biomechanical analysis of functional movements of the spine and pelvis caused by quasi-continuous changes of posture, if these can be observed as changes in back shape. Two examples are given to illustrate the aim and performance of functional examinations. Shoe elevation is used to correct leg-length discrepancy and is therefore prescribed for prevention and correction of scoliosis produced by pelvic obliquity. In a previous study it was shown that simulating leg-length discrepancy by raising a foot causes the pelvis to perform a torsional movement about the transverse axis. In effect, this movement reduces to some extent the effect of shoe elevation; thus a larger elevation might give better results. 42 scoliotic patients underwent functional examination. Leg-length discrepancies were simulated in 7 steps, and the resulting back shape was analysed by rasterstereography. The measurements were corrected for pelvic torsion. This method provided satisfactory correspondence with radiographically recorded leg-length discrepancies, i.e. 0.7 mm +/- 11.2 mm. One specific advantage of this procedure is that it covers aspects relating to spinal lateral deviation and vertebral rotation. It is concluded, however, that the 7 measurements used are hardly sufficient for this application and that better results are therefore to be expected from extended series. Kyphosis and lordosis clearly depend on posture. This is confirmed in a functional examination where these angles are measured under voluntary changes of posture. In forward bending, the trunk straightens and kyphosis and lordosis angles decrease. The reverse case applies to backward bending. If this effect is taken into quantitative consideration, an improved accuracy of measurements is obtained by reference to a standardised, mathematically defined posture. The resulting rms-error of kyphosis/lordosis measurement is then reduced from 3.10 degrees/2.95 degrees to 1.65 degrees/1.40 degrees. These figures open up new applications in the follow-up of kyphotic and lordotic deformities.

Assessment of disc injury in subjects exposed to long-term whole-body vibration.

Long-term exposure to whole-body vibration is known to increase the risk of low back problems. The chain of events leading from repeated loading of the lumbar spine to back complaints and the exact nature of the vibration-induced damage are, however, obscure. Fluid in- and outflow as well as viscoelastic deformation are important aspects of the physiological function of the lumbar disc. Precision measurement of stature, termed 'stadiometry', has previously been applied in healthy subjects to document changes in disc height in relation to the load on the lumbar spine. The purpose of this study was to explore the relation between spinal loading and stature in a cohort of 20 subjects with long-term exposure to whole-body vibration. If the change of stature (and thus the change of disc height) caused by changes in spinal loading differed between exposed and normal subjects, this would point to vibration-induced changes in structure and material properties of the discs. For this purpose, four hypotheses were tested: (1) the viscoelastic deformation and fluid exchange of intervertebral discs during phases of spinal loading and unloading differs from normal; (2) the water content of lumbar discs of subjects exposed to long-term whole-body vibration deviates from normal; (3) the mean disc height of the lumbar spine depends on the total time of vibration exposure; (4) repeated loading influences trabecular bone density of vertebrae in the lumbar spine. A cohort of 20 operators of heavy earth-moving machinery was enrolled. Back complaints suspected to be due to long-term exposure (mean 17.6 +/- 2.1 years) to whole-body vibration and application for early retirement were the selection criteria used. Change of stature during a regular 8-h shift and change of stature in standing, carrying and sitting activities were measured. The stadiometric investigations were supplemented by magnetic resonance imaging (MRI) of the lumbar spine to assess whether the water content of the discs exhibited deviations from normal. In addition, quantitative computed tomography (QCT) was performed to assess whether the trabecular bone density of the third lumbar vertebra deviated from normal. The results showed no significant difference in change of stature while standing, carrying or sitting between exposed machine operators and non-exposed operators. Likewise, MRI examinations revealed no significant differences in the water content of the discs averaged over the lumbar spine. In addition, QCT examinations revealed no significant difference in the trabecular bone density of the third lumbar vertebra. The study thus revealed no significant difference between a cohort with long-term exposure and non-exposed controls with respect to viscoelastic properties of discs as determined by stadiometry, average water content of lumbar discs and trabecular bone density of L3.

[3-dimensional surface measurement of spinal deformities with video rasterstereography]. / Die dreidimensionale Oberflächenvermessung von Wirbelsäulendeformitäten anhand der Videorasterstereographie.

QUESTION: Video rasterstereography is a method for back surface measurement comprising automatic back surface reconstruction and shape analysis. Aim of this prospective study was to determine the accuracy of this method in comparison to the conventional frontal and lateral standing radiographs. METHOD: 95 patients with idiopathic scoliosis or scoliotic postural abnormalities and 18 patients with thoracic hyperkyphosis and Scheuermann's disease were investigated. The Cobb angles, the sagittal profile and apical vertebral rotation as well as pelvic obliquity and trunk decompensation were measured. The analysis was carried out by two independent observers. RESULTS: The root mean square (r.m.s.) deviation of the Cobb angle in the cases of idiopathic scoliosis ranged between 7 degrees and 8 degrees. In video rasterstereography there were no false negative results and two false positive results concerning differentiation between structural scoliosis and scoliotic postural abnormality. The r.m.s. deviation of apical vertebral rotation averaged 7.9 degrees and for pelvic obliquity respectively trunk imbalance 0.65 cm respectively 1.07 cm. The thoracic hyperkyphosis in Scheuermann's disease showed a r.m.s. deviation of 5.6 degrees. CONCLUSIONS: Video rasterstereography is a reliable method in the three-dimensional evaluation of spinal deformities and constitutes a valuable additional tool to the clinical examination and can reduce the number of radiographs.

Spinal shrinkage during work in a sitting posture compared to work in a standing posture.

OBJECTIVE: The objective was to measure the possible differences in shrinkage of the thoracolumbar spine in subjects working in a sitting and a standing posture for 6.5 h at work, in a realistic work environment. The isolated shrinkage of the thoracic and the lumbar spine was also examined. STUDY DESIGN: This study presents a new protocol to measure shrinkage of the thoracic and lumbar spine separately. BACKGROUND: Controversies still exist with regard to the load on the spine in a sitting compared to a standing position. Some report that shrinkage is greatest in the sitting position while others report the reverse. However, nothing is known about the height reduction of the thoracic and the lumbar spine during loading for 6.5 h in a real work environment. Therefore, the behaviour of the thoracic and the lumbar spine under practical condition has to be investigated. METHOD: A stadiometer with a measurement error of 0.51 mm was used to measure changes in spinal height during work. To exclude first-time behaviour of the spine, a pre-test lasting 50 min was undertaken. The mean of the last three measurements was used as the reference height. During work, height measurements of the spine were performed every 20 min. To separate the behaviour of the thoracic and the lumbar spine, two benchmarks were placed at the vertebrae prominens and at the thoracic-lumbar junction. Shrinkage of the spine was investigated within three different cohorts: (I) work in a sitting posture for 6.5 h; (II) relaxed sitting for 2 h vs work for 2 h in a sitting position and (III) work in a standing position for 6.5 h. RESULTS: Relaxed sitting leads to a gain in stature compared to work in a sitting position for 2 h. The major gain in stature occurred in the lumbar spine. Comparison of cohort (III) working in a standing position with cohort (I) working in a sitting position shows that the shrinkage of the spine is greatest when work is performed in a standing posture. The major differences were found in the shrinkage of the lumbar spine, e.g. shrinkage of the lumbar spine in the standing cohort (III) was 4.16 mm compared to 1.73 mm in the sitting cohort (I). CONCLUSIONS: There is a gain in stature during relaxed sitting compared to work in a sitting posture. The load on the spine is greatest when work in a standing position is performed. The greater shrinkage of the lumbar spine during work in a standing position compared to a sitting posture is probably due to: (i) differences in lumbar lordosis and (ii) the effect of bending and torsion while handling the work materials.

Assessment of scoliotic deformity from back shape asymmetry using an improved mathematical model.

OBJECTIVE: The objective of the study was to improve with respect to accuracy and smoothness the three-dimensional model of the spinal midline which has been calculated from rasterstereographic back surface data. DESIGN: A new mathematical model using frequency-modulated sine curves has been applied to existing rasterstereographic and radiographic data in an in vivo study. BACKGROUND: Analysis of back shape (measured by rasterstereography) enables a three-dimensional model of the spinal midline to be calculated. The model is based on the so-called symmetry line which coincides approximately with the line of the spinous processes. In addition the surface rotation on the symmetry line is taken as an estimate for vertebral axial rotation in scoliosis. METHODS: Four hundred and seventy-eight pairs of radiographs and rasterstereographs of scoliotic patients have been evaluated and compared using the new model. The radiographs were digitized manually, delivering curves of lateral deviation and vertebral rotation. Analysis of back shape from the rasterstereographs delivers a three-dimensional model of the spinal midline, the frontal projection of which is to be compared with the radiographic curve. Likewise, vertebral rotation and surface rotation are compared. RESULTS: The use of frequency-modulated sine curves improved the results as compared to the existing procedure with respect to prediction accuracy of lateral deviation (typically from sigma(x) = 4.6 mm to sigma(x) = 4.0 mm, P < 10(-10)). The prediction of axial rotation was not significantly improved (sigma(varrho) thick approximate 3.8 degrees ). In addition, the smoothness of the curves is considerably improved. The prediction accuracy proved to be independent of the scoliosis type as represented by apex height (r = -0.09 ellipsis + 0.03). CONCLUSION: The use of frequency-modulated sine curves improves significantly the accuracy and smoothness of the spinal model curves.

Back shape measurement using video rasterstereography and three-dimensional reconstruction of spinal shape.

Video rasterstereography is a method for back surface measurement comprising automatic back surface reconstruction and shape analysis. It is particularly appropriate for the examination of scoliosis. In this application shape analysis includes model-based calculations of vertebral rotation (determined from surface rotation) and of the spinal midline in three dimensions. The results are delivered in quasi-real time (computing time < 5 min). The aim of the present study was to validate the method by comparison of rasterstereographic and radiographic data. Anteroposterior radiographs and rasterstereographs (478) of 113 scoliosis patients were analysed, each pair taken on the same day. Matching the radiographic midline of the spine to its rasterstereographic equivalent, the deviations between the two curves are properly expressed by their root mean square (r.m.s.) deviation. A r.m.s. deviation in the order of 4 mm was found. Similarly, the r.m.s. deviation of vertebral rotation from surface rotation was about 3°. No systematic difference of vertebral and surface rotation, as reported by other authors, could be found. This may be attributed to our method of data evaluation, consisting of a sophisticated analysis of surface curvature and shape asymmetry. These mathematical procedures are made possible by the high sampling density and resolution of video rasterstereography. Conventional scoliosis parameters (e.g. Cobb angle, apical rotation, apex height, etc.) can be estimated with limited accuracy from the reconstructed midline. The relevant standard deviations are given.

Evaluation of frontal radiographs of scoliotic spines--Part II. Relations between lateral deviation, lateral tilt and axial rotation of vertebrae.

The shape of scoliotic spines as measured from frontal radiographs (see Part I of this paper) is analysed with respect to interrelations between lateral deviation, lateral tilt and axial rotation of the vertebrae. These parameters are represented by sinusoidal functions of the longitudinal coordinate. The interrelations can, therefore, be expressed in terms of amplitude and phase relations. Two additional functions--'spinal tilt' and (local) curvature--are calculated from the first and second derivatives of lateral deviation. The method has been applied to three patient groups with different aetiology: 113 patients with idiopathic scoliosis (478 radiographs, partially follow-up examinations), 23 patients with scoliosis secondary to Wilms' tumour irradiation and 18 patients with scoliosis secondary to poliomyelitis. The amplitude and phase relations of all functions reveal a characteristic pattern which is apparently independent of the specific aetiology. The results show that the available biomechanic explanations of coupling of vertebral motions are questionable.

Evaluation of frontal radiographs of scoliotic spines--Part I. Measurement of position and orientation of vertebrae and assessment of clinical shape parameters.

A new method largely exploiting the shape information which may be obtained from frontal radiographs of scoliotic patients is presented. For a complete description of spinal deformity, six position parameters are needed for each vertebra. From a strictly mathematical point of view, none of them can be determined from a single standard radiograph. However, the four most important parameters can be measured if some reasonable assumptions are made. For a better interpretation, three of these parameters (lateral coordinate x, lateral tilt alpha and axial rotation rho) are plotted as a function of the fourth parameter, the longitudinal coordinate y. These functions may well be approximated by sinusoidal curves (or possibly by Fourier series). The data smoothing implied by this procedure improves the reliability of the data. The method has been tested with 478 radiographs of 113 patients (Cobb angles up to 52 degrees). The results are compared with scoliosis parameters which have been determined according to the conventional clinical rules. A particular advantage of approximation by a sinusoidal function lies in the direct relation of the curve parameters to common scoliosis parameters. Moreover, a mathematical analysis of the interrelations between different parameters--for example, between lateral deviation and axial rotation--is possible in this case.

Automatic localization of anatomical landmarks on the back surface and construction of a body-fixed coordinate system.

A method for automatic measurement of anatomical landmarks on the back surface is presented. The landmarks correspond to the verteba prominens, the dimples of the posterior superior iliac spines and the sacrum point (beginning of rima ani), which are characterized by distinct surface curvature. The surface curvatures are calculated from rasterstereographic surface measurements. The procedure of isolating a region of interest for each landmark (surface segmentation) and the calculation of the landmark coordinates are described in detail. The accuracy of landmark localization was tested with serial rasterstereographs of 28 patients (with moderate idiopathic scoliosis). From the results the intrinsic accuracy of the method is estimated to be little more than 1 mm (depending on the sampling density of the surface measurement). Therefore, the landmarks may well be used for the objective definition of a body-fixed reference coordinate system. The accuracy is, however, dependent on the specific landmark and a minor influence of posture variations is observed.

Movement of the human pelvis and displacement of related anatomical landmarks on the body surface.

Anatomical landmarks on the body surface can be measured with high accuracy by using rasterstereography and surface curvature analysis. The present study shows that the lumbar dimples can be localized with a statistical error of about 1 mm. It is generally assumed that the dimples are in close relation to the pelvis (in particular to the PSISs) and may thus be taken as indicators for pelvis movements. By introducing an artificial pelvis tilt of up to +/- 10 degrees this relation was examined. In fact, a nearly perfect correlation (r approximately equal to 0.99) between landmark and pelvis movements was observed. Asymmetries of pelvis motion due to scoliotic deformity were not observed. There was, however, a systematic lag of the dimple movements, resulting in a displacement of the dimples of up to +/- 1.5 mm relative to the pelvis (for +/- 10 degrees pelvis tilt). Either a soft tissue effect or a torsion of the pelvis may be responsible for this behaviour. The theory of pelvis torsion is confirmed by the fact that the orientation of the back surface at the locus of the dimples reveals a corresponding torsion of similar magnitude and sign. A torsion angle of about +/- 1.5 degrees in either sacro-iliac joint is sufficient to explain the observed dimple lag and the surface torsion. An independent measurement (e.g. using roentgenphotogrammetry) would be desirable to further validate this theory. According to our measurements the dimples of the PSISs cannot be taken as exact indicators for orientation and movement of the pelvis.(ABSTRACT TRUNCATED AT 250 WORDS)