[Two key describers of the sacro-acetabular relationships: the angles of sacral and acetabular incidence]. / Deux descripteurs clé des relations sacro-cotyloïdiennes : les angles d'incidence sacrée et cotyloïde Mise en évidence par le logiciel De-Visu.

PURPOSE OF THE STUDY: Implantation of total hip arthroplasties raises several important questions concerning the relationship between the orientation of the lumbosacral joint and the acetabular-femoral joint; in other words, between the position of the patients trunk and the orientation of the acetabula. To elucidate better these complex relationships, we conducted a morphometry study on a sample of 51 dry pelves: pelv 26 female and 25 male specimens. MATERIAL AND METHODS: Three-dimensional coordinates of 47 homologous points were recorded for each pelvis. Data were then processed with De-Visu, a graphic visualization software. Seven parameters were compared: sacral slope, sacral incidence, and five parameters quantifying the three-dimensional orientation of the acetabula. RESULTS: The graphic modelization enabled an integral 3-D visualization of each pelvis. The sagittal view enabled simultaneous visualization of the sacrum, the sacroiliac joints, the acetabula, and their alignments, as well as the variability of their spatial relation. The position reference chosen to simulate the upright position aligned the anterior iliac spines and the superior pubic point. This position was found pertinent because the mean value of the sacral slope (41.8) and the sacral incidence (54) were not different from published series. The sacral slope was the most strongly correlated with the acetabular parameters. It exhibited a positive correlation with sagittal acetabular slope (r=0.59) and acetabular inclination (r=0.59). It exhibited a negative correlation with acetabular anteversion (R=0.45). The correlation with the sagittal acetabular slope was very strong for anteversion (r=0.92), and rose with acetabular inclination (r=-0.66). The angle formed by the two acetabular axes was highly variable (37). The correlation between this angle and inclination was very high in males (r=-0.88) and non-significant in females. There was however a very strong correlation with anteversion in females (r=-0.74) which was non-significant in males. This contrasting finding was related to the wide spread of the inclination values in males and anteversion values in females. DISCUSSION: We demonstrated a new sagittal parameter: the acetabular incidence. The summit of this angle is the center of the acetabulum. The sides are the pelvic thickness and the acetabular axes. This parameter was negatively correlated with the sacral incidence. It account simultaneously for the sagittal position of the sacrum in relation to the acetabula and for the degree of acetabular anteversion and inclination. We have demonstrated that the geometric sum of these two angles, sacral incidence and acetabular incidence, is equivalent to the sacro-acetabular angle demonstrated by Lazennec and Saillant. These authors showed that the sacro-acetabular angle is the sum of two positional parameters, the sacral slope and the sagittal acetabular tilt (or slope). The three angles -- sacral incidence, acetabular incidence, sacro-acetabular angle -- are anatomic angles which do not vary with the pelvic position.

Gravitational forces and sagittal shape of the spine. Clinical estimation of their relations.

The sagittal morphology of the pelvis determines the amount of lordosis needed for each individual. The proper harmony of the sagittal spinal curves allows a stable balance, economical in terms of mechanical effects and muscular energy. A previous barycentremetrical laboratory study allowed us to demonstrate that the axis of gravity of the upper body segment was located behind the lumbar vertebrae and the femoral heads, thus ensuring economy and stability. The determination of the anatomical connection of the individual gravity is thus of primary importance for the evaluation of sagittal balance. Data for 42 patients without spinal pathology, previously evaluated by barycentremetry, were used to establish a predictive equation for the application point of the gravity at the level of the third lumbar vertebra (L3). This equation, using anthropometric and radiographic pelvic and spinal parameters, was integrated into a software program called Similibary. It was applied to the same 42 subjects. These results were compared in order to validate the method. No significant difference was observed between the two techniques. This easy-to-use tool allows a personalised evaluation of the sagittal balance of the spine, both through the evaluation of the harmonious relationship between the spinal curves and the pelvis, and through the location of gravity supported by the vertebral structures in L3.

Sagittal alignment of spine and pelvis regulated by pelvic incidence: standard values and prediction of lordosis.

Pelvis and spinal curves were studied with an angular parameter typical of pelvis morphology: pelvic incidence. A significant chain of correlations between positional pelvic and spinal parameters and incidence is known. This study investigated standards of incidence and a predictive equation of lordosis from selective pelvic and spinal individual parameters. One hundred and forty nine (78 men and 71 women) healthy adults, aged 19-50 years, with no spinal disorders, were included and had a full-spine lateral X-ray in a standardised upright position. Computerised technology was used for the measurement of angular parameters. Mean-deviation section of each parameter and Pearson correlation test were calculated. A multivariate selection algorithm was running with the lordosis (predicted variable) and the other spinal and pelvic parameters (predictor variables), to determine the best sets of predictors to include in the model. A low incidence (<44 degrees ) decreased sacral-slope and the lordosis is flattened. A high incidence (>62 degrees ) increased sacral-slope and the lordosis is more pronounced. Lordosis predictive equation is based on incidence, kyphosis, sacral-slope and +/-T9 tilt. The confidence limits and the residuals (the difference between measured and predicted lordosis) assessed the predicted lordosis accuracy of the model: respectively, +/-1.65 and 2.41 degrees with the 4-item model; +/-1.73 and 3.62 degrees with the 3-item model. The ability of the functional spine-pelvis unit to search for a sagittal balance depended both on the incidence and on the variation section of the other positional parameters. Incidence gave an adaptation potential at two levels of positional compensation: overlying state (kyphosis, T9 tilt), underlying state (sacral slope, pelvic tilt). The biomechanical and clinical conditions of the standing posture (as in scoliosis, low back pain, spondylisthesis, spine surgery, obesity and postural impairments) can be studied by comparing the measured lordosis with the predicted lordosis.

The sagittal anatomy of the sacrum among young adults, infants, and spondylolisthesis patients.

The anatomic pelvic parameter "incidence" - the angle between the line perpendicular to the middle of the sacral plate and the line joining the middle of the sacral plate to the center of the bicoxo-femoral axis - has been shown to be strongly correlated with the sacral slope and lumbar lordosis, and ensures the individual an economical standing position. It is important for determining the sagittal curve of the spine. The angle of incidence has also been shown to depend partly on the sagittal anatomy of sacrum, which is established in childhood while learning to stand and walk. The purpose of this study was (1) to define the relationship between the sacrum and the angle of incidence, and (2) to compare these parameters in three populations: young adults, infants before walking, and patients with spondylolisthesis. Forty-four normal young adults, 32 infants not yet walking and 39 patients with spondylolisthesis due to isthmic spondylolysis underwent a sagittal full-spine radiography. A graphic table and the software for bidimensional study of the sacrum developed by J. Hecquet were used to determine various anatomic and positional parameters. Comparison tests of means, and multiple and partial correlation tests were used. A study of the reliability of the measurements using factorial plan methods was performed. The sagittal anatomic parameters of the sacrum were found to have a close relationship with the pelvic parameter of incidence angle, and therefore with the sagittal balance of the spine. The anatomy of the sacrum in spondylolisthesis patients is particular in that some features are much like those of young infants, but it is more curved and the incidence angle is significantly larger. There is a close relationship between angle of incidence and the slip of spondylolisthesis. All the parameters of young infants are significantly smaller than those of adults. It can be concluded that the sagittal anatomy of the sacrum plays a key role in spinal sagittal balance. The sacral bone is an integral a part of the pelvis and constitutes the undistorted part of the spinal curves. Organization of sagittal curves during growth can be followed up by looking at the sacrum. The sacrum in the spondylolisthesis group differs from the normal, and the greater angle of incidence and sacral slope in this group could predispose to vertebral slip.

Access to a three-dimensional measure of vertebral axial rotation.

Scoliotic curvatures can only be assessed through three-dimensional (3D) procedures. Measurement of the axial vertebral rotation appears to be of primary importance for such techniques. Nevertheless, traditional methods are based only on 2D data, obtained through antero-posterior radiographic projections of the spine. A 3D method is described in this study, taking into account the sagittal tilt of the vertebrae. Only such a measurement provides a real 3D method for a true appraisal of the scoliotic spine. The practical implications are developed.

Pelvic incidence: a fundamental pelvic parameter for three-dimensional regulation of spinal sagittal curves.

This paper proposes an anatomical parameter, the pelvic incidence, as the key factor for managing the spinal balance. Pelvic and spinal sagittal parameters were investigated for normal and scoliotic adult subjects. The relation between pelvic orientation, and spinal sagittal balance was examined by statistical analysis. A close relationship was observed, for both normal and scoliotic subjects, between the anatomical parameter of pelvic incidence and the sacral slope, which strongly determines lumbar lordosis. Taking into account the Cobb angle and the apical vertebral rotation confers a three-dimensional aspect to this chain of relations between pelvis and spine. A predictive equation of lordosis is postulated. The pelvic incidence appears to be the main axis of the sagittal balance of the spine. It controls spinal curves in accordance with the adaptability of the other parameters.

The outcome of walking in stable neuromuscular deficiencies.

In some patients with stable or very gradually worsening neuromuscular disorders, walking performance nevertheless decreases with increasing hip flexion and spinal deformity as the patient grows. The relations between muscular deficiency, pelvic and spinal deformity, head stability, gravity parameters and walking performance were studied in 43 patients aged 18 months to 38 years with a view to finding out how these parameters are related, whether progressive spinal deformity and loss of walking can be avoided or delayed, and whether specific therapy for each of these parameters can help. Early combating of hip flexion deformity by physiotherapy, accompanied by limbering-up exercises of the spine to counteract lumbar and thoracic lordosis are useful, as are orthoses to correct pelvic tilt anteversion, spinal lordosis and head instability. If physiotherapy is ineffectual or too late, tenoctomy of the rectus femoris may help.

Threshold values for supine and standing Cobb angles and rib hump measurements: prognostic factors for scoliosis.

Seven parameters recorded at the first clinical examination of 326 growing scoliotic patients were correlated with the speed of progression of the scoliotic curve during a natural history survey period. The parameters were: age; bone age (according to Greulich and Pyle); pubertal and Risser stage; curve shape; rib hump, measured in forward bending in a sitting patient and supine and standing radiographic Cobb angles of the scoliotic curve. The speed of progression of the scoliotic curve was expressed as the annual increase in Cobb angle. It was quantified graphically after plotting the measurements taken from all the radiographic examinations made during the survey. The survey period ranged from 6 months to several years, depending on the rate of progression. It was 6 months only if the scoliotic curve demonstrated worsening of more than 3 degrees at two successive examinations performed at least 3 months apart. The authors aimed to identify the minimum values of curve angle and rib hump, identified at first examination in 95-100% of patients whose parameters at follow-up were above these values (supine angle: 17 degrees; standing angle: 24 degrees; rib hump: 11 mm), therefore demonstrating curve worsening. Then, they analysed how the other parameters such as age, bone age, state of maturation and curve shape influenced these threshold values of rib hump and supine and standing angles. The authors present the threshold values for the whole sample according to the sexual state of maturation and also for each curve shape. They demonstrate that a combination of states of maturation, several measures of the scoliotic curve and curve shape provides the best basis for individual prognosis.

Rib hump and supine angle as prognostic factors for mild scoliosis.

A retrospective study was conducted on 262 patients with minor idiopathic scoliosis, having supine angles of less than 30 degrees and rib humps of less than 30 mm at the first examination. The initial radiographic measurement of the Cobb supine angle and rib hump height, recorded during a bending test performed on subjects in a sitting position, was correlated with the rate of scoliosis progression. Scoliosis progression was estimated graphically from an angle diagram established by monitoring untreated patients for 7 months to several years, depending on the rate of progression before treatment. More than 95% of the patients with initial supine angles of more than 17 degrees or rib humps greater than 11 mm suffered from progressive scoliosis. The importance of the size of the supine angle, rib-hump height, scoliotic pattern, and state of maturation for the progression rate are analyzed. Knowledge of these parameters can be used to make individual prognoses for approximately 95% of these subjects.

A Barycentremetric study of the sagittal shape of spine and pelvis: the conditions required for an economic standing position.

The standing posture of 17 young men and women were studied using Barycentremeter measurements and full spine radiograph with a single referential system. These procedures provide in vivo measurements of the weight and center of weight supported by each vertebra and the coxofemoral joints. The relationship between the vertebra, the sacrum or the coxofemoral rotation axis and the center of weight they support, is displayed. The moment of the corresponding force may also be assessed. Mean values were computed and the relation with spine sagittal curves and pelvic parameters were studied. The position of the center of weight, in front of or behind the vertebra or the coxofemoral joints, requires an opposing muscle force to ensure mechanical stability. The load exerted on the vertebra cannot be precisely evaluated, but we can describe the way in which these loads vary when the spinal curves and the pelvic slope change. This study provides basic data suggesting that there is a tendency to maintain the body in the most economical position in terms of muscle fatigue and vertebral strain. Individual anatomical shapes and pelvic parameters of the pelvis induce corresponding specific sagittal curves of the spine. This concept is very useful for analysing pathological situations and devising appropriate treatment.

Upward displacement of the centre of gravity in paraplegic patients.

The centres of gravity of 44 complete chronic spinal cord injured patients and 24 normal subjects were measured using a gamma ray scanner (Barycentremetre). The results are expressed as a percentage of body length and as anatomical level. The mean weight of paraplegic patients was 12kg less than the controls. The centre of gravity was 5% of body length higher in the paraplegic patients than in the controls, equivalent to 3 to 4 vertebrae level. The importance of such changes in the centre of gravity for the design of stable wheelchairs is discussed.

Age-dependent responsiveness of rabbit and human cartilage cells to sex steroids in vitro.

Rabbit epiphyseal cartilage tissue has been shown to convert testosterone (T) to dihydrotestosterone (DHT). In this report, the metabolic conversion of T into DHT is shown to be age-dependent, being most active in cartilage from animal at the age of gonadal maturation. Human cartilage from newborn and prepubertal children is also shown to convert T into DHT and--to a lesser extent--to estradiol. Low concentrations of DHT and 17 beta-estradiol (E2) (10(-11)-10(-9) M) were also shown to stimulate in vitro cartilage cells from boys and girls respectively. As previously shown for cultured rabbit chondrocytes, the stimulating effects of both hormones on human chondrocytes was age-dependent. Cartilage cells derived from children up to one year old did not respond, while cells from boys and girls in the early phase of puberty responded best. These data indicate that human cartilage tissue in vivo, contains both 5 alpha-reductase and aromatase activities during post-natal skeletal growth. Androgens may act on cartilage after their metabolic conversion to estrogens. The mechanism of age-dependency of both cartilage androgen enzymatic activities and chondrocyte responsiveness to sex steroids in vitro remains to be explained.

[Infantile spinal muscular atrophy]. / Amyotrophie spinale infantile.

The authors report 100 cases with prolonged spinal muscular atrophy (SMA) and survival beyond 4 years old. There were 46 boys and 54 girls. 23 of them had histories with an autosomal recessive form of inheritance. One case had a dominant form. The unity of cases described as Werdnig Hoffman disease [SMA I, SMA II (Childhood), ans SMA III (Kugelberg Welander)] is supported and our cases fell in three groups according to their ambulatory capabilities: never acquired, lost, or retained. 71 cases have never walked: the onset of symptoms was noted at an average age of 6.4 months +/- 3; the average age at the last examination was 16 years (4-39). Death occurred in 6 cases. Loss of walking occurred in 24 cases: the onset of symptoms was noted at an average age of 17.4 months +/- 14.2. 5 cases were still ambulatory: the onset of symptoms was noted at an average age of 2.4 years +/- 2.8. For these last 29 cases the average age at the last examination was 20 years (4-38); death occurred in two cases. The weakness was symmetrical and proximal. The period of worsening varied but, frequently, patients with a later onset of symptoms had a longer period of deterioration. Tongue fasciculations were present in all cases who never walked. Facial and masseter weakness occurred in 3 cases. Oesophagus dyskinesia and distension of the stomach due to brain stem lesions occurred in many cases. This brain stem damage was responsible of 2 sudden deaths (8-30 years). Premature puberty occurred in 14 cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth of trunk and legs of children with myelomeningocele.

Total body length and body segments (crown-rump length, sub-ischeal length) of 78 children with myelomeningocele were measured at regular intervals during growth for a mean duration of 4.4 years. These children were shown to have defective growth, with an increased upper segment/lower segment ratio. It was found that the higher the level of the meningocele the greater the growth defects. However, the relationship was statistically significant only for the first seven years of life. It is concluded that neurological damage was mainly responsible for defective growth during the first years of life, but that other factors independent of the level of the meningocele also come into play in later years.

Visualization on full spine radiographs of the anatomical connections of the centres of the segmental body mass supported by each vertebra and measured in vivo.

A gamma-ray scanner has been used to develop in vivo a rapid, noninvasive technique for the estimation of the mass of successive body scans, and the positions of the centres of those masses. The integrated data are computed to calculate the mass supported by each vertebra and the coordinates of the centre of these masses. These coordinates are transferred from the coordinate system of the gamma ray table to the coordinate system of the X-ray radiographs. In this way, the anatomical relations of the centres of these masses are visualized on the frontal and sagittal full spine radiographs. The method allowed the estimation of various biomechanical parameters such as the height of half the body mass or the compressive load on a specific vertebra. These new parameters were found to be similar to equivalent parameters in the literature. Therefore, these comparisons validate the method. Fourteen normal subjects were tested, and their mean data are proposed as reference.

[Respiratory, spinal and thoracic problems in children with prolonged infantile spinal amyotrophy]. / Les problèmes thoraciques rachidiens et respiratoires de l'enfant atteint d'amyotrophie spinale infantile à évolution prolongée.

The authors studied the evolution of spinal and respiratory involvements in 88 patients with prolonged spinal muscular atrophy. Patients were divided into 3 groups according to their ambulatory capabilities: never acquired, lost or retained. Evaluation at the time of the first examination gives an idea of the spontaneous evolution. It shows the high incidence (91%) and severity of scoliosis, and the variable severity of the respiratory impairment from one group to another. The follow-up period ranged from 6 to 9 years. Ten patients died. At the end of the follow-up period a new spinal and respiratory evaluation was performed. Results suggest the efficacy of early treatment of spinal impairment and emphasize the need for assisted ventilation as soon as the disease is diagnosed.

Scoliosis at less than 30 degrees. Properties of the evolutivity (risk of progression).

In an attempt to find prognostic factors for mild scoliosis, the first clinical and radiologic data of 159 subjects with idiopathic scoliosis less than 30 degrees were correlated with the annual speed of progression estimated graphically by further examinations. Thoracic and double major are more progressive than thoracolumbar and lumbar. The correlation with rate of progression is better for supine angle than for standing angle. Curves with low supine angles are those that have great relative collapse and low risk of progression. Only the rib hump of thoracic and thoracolumbar are correlated with evolutivity. Predictive equations give less approximation for individual prognosis than a previous graphic method, so they are not used. Approximately 73% of scoliosis have evolutivities less than 6 degrees per year and required nocturn corrective treatment.

Flexibility of scoliosis. What does it mean? Is this terminology appropriate?

This work is a critical analysis of the term "flexibility of scoliosis." The authors demonstrate that this measure includes two very different and noncorrelated phenomena: the collapse and the reducibility of the structural curve. In 228 paralytic curves, these two phenomena were quantified and correlated with different parameters of scoliosis: sex, stage of maturation, curve pattern, number of vertebrae in the curve, spinal and abdominal test values, and the scoliotic evolution rate. Reducibility can be predicted since it is an elasticity process. Collapse is more complex, but it is a prognostic factor for evolution and effectiveness of treatment. The preliminary results of a similar study of idiopathic scoliosis are the same.