Three-dimensional reconstructions of Lenke 1A curves

Background

Scoliosis is a 3D deformity that can be reconstructed through 2D antero-posterior and lateral radiographs, which provide an upper view of the deformed spine as well as regional planes matching all vertebrae of elective plane for each curve. The objective of this study is to explore whether all idiopathic scoliosis classified Lenke 1A have the same 3D representation made with regional planes.

Methods

All patients treated for idiopathic thoracic scoliosis during the growth period and classified Lenke 1A were included in this study conducted in the pediatric spinal orthopedic department of Centre des Massues. A photogrammetric technique was used to obtain a 3D reconstruction, from regional planes identified on radiographs made with the EOS system. Three regional planes are usually identified in asymptomatic spines: lumbar, dorsal, and cervical—none of them presenting rotation. In the studied group, the number of planes, the rotation, and the limit vertebrae of each plane were looked for.

Results

Sixty-three patients were included (47 girls and 16 boys, mean age 11.3 years). The Cobb angle was meanly 36.5°. The scoliosis was reconstructed with three regional planes (57%) or four ones (43%, with the thoracic plane divided into two planes). Maximal rotation was found in the thoracic plane, especially when scoliosis was represented with four regional planes. The transition between planes 2 and 3 was mainly located between the fourth and sixth dorsal vertebrae.

Conclusion

The use of an arbitrary regional plane representation of a 3D shape leads to conclude that there are two types of Lenke 1A scoliosis, which should be taken into account for designing the brace.

Motor function levels and pelvic parameters in walking or ambulating children with cerebral palsy

BACKGROUND

In children with cerebral palsy, spinal equilibrium and pelvic strategies may vary according to the functional status.

OBJECTIVES

To study the relationship between motor function and pelvic and spinal parameters in a population of children and adolescents with cerebral palsy (rated from level I to level IV on Gross Motor Function Classification System [GMFCS]). A sagittal X-ray of the spine in the standing position was analyzed with Optispine(®) software.

RESULTS

The study population comprised 114 children and adolescents (mean [range] age: 12.35 [4-17]). For the study population as a whole, there were significant overall correlations between the GMFCS level on one hand and pelvic incidence and pelvic tilt (PT) on the other (P=0.013 and 0.021, respectively).

DISCUSSION

Pelvic parameters vary according to the GMFCS level but do not appear to affect spinal curvature. The sacrum is positioned in front of the head of the femur (i.e. negative PT) in GMFCS level I and progressively moves backwards (i.e. positive PT) in GMFCS levels II, III and IV.

Sagittal X-ray parameters in walking or ambulating children with cerebral palsy

Adolescents with cerebral palsy (CP) who walk or ambulate often have an abnormal clinical and radiological spinal profile during pubertal growth compared with adolescents of the same age without neuromotor impairments. Therefore, in the following study, we aimed to conduct a radiological assessment of static data on the lumbar-pelvic-femoral complex in ambulatory children with CP to compare these data with those of an asymptomatic population. The CP population was comprised of 119 children and the asymptomatic population was comprised of 652 children. The large format (30×90cm) sagittal X-rays were taken while subjects were in a comfortable position in which knees and hips were in maximal extension. Analyses were performed using Optispine(®) software to measure the parameters of an X-ray of the profile of the spine, pelvis and femurs. Comparing, the two populations, we found no difference in the shape parameter (pelvic incidence) but we did find significant differences in the positional parameters (pelvic tilt and sacral slope) of the pelvis. We found a difference in the curvature and orientation of lumbar lordosis as well as in the number of vertebrae involved in the kyphosis and its orientation. There was also a significant difference in the C7 plumb line. We can say that the CP population is not structurally different from the control population, but that parameters become disturbed during growth. These disturbances should be identified and monitored so that changes can be detected early and progression can be prevented.

[Audits of good practice: implantable medical devices are also concerned]

INTRODUCTION

Within the framework of a good practices agreement, French hospitals must perform clinical audits of costly molecules and implantable medical devices (IMD) to justify their medical costs. We present two examples of clinical audits of IMD: hip arthroplasties and cardiac stimulators.

PATIENTS AND METHODS

The clinical audits were managed by the pharmacy with the support of the medical teams. Retrospective evaluation of patient files was performed by a pharmaceutical team using evaluation grids developed from official references from the French National Authority for Health and French National Health Insurance.

RESULTS

The audit of hip arthroplasty procedures, including a retrospective and prospective study, showed that 95.4% and 96.9% of the surgical procedures followed guidelines. The audit of cardiac stimulators showed 100% agreement with guidelines. The audit of traceability showed that 97% of the files were complete.

DISCUSSION

These audits show that the cost increases of the IMD are linked to following guidelines. It is important for these audits of pertinent use to be performed by both physicians and pharmacists.

CONCLUSION

There is very little information in the literature or from authorities to help implement these audits. It would be interesting to propose common prospective and retrospective methods to evaluate the pertinent use of IMD.

Geometric Structure of 3D Spinal Curves: Plane Regions and Connecting Zones

This paper presents a new study of the geometric structure of 3D spinal curves. The spine is considered as an heterogeneous beam, compound of vertebrae and intervertebral discs. The spine is modeled as a deformable wire along which vertebrae are beads rotating about the wire. 3D spinal curves are compound of plane regions connected together by zones of transition. The 3D spinal curve is uniquely flexed along the plane regions. The angular offsets between adjacent regions are concentrated at level of the middle zones of transition, so illustrating the heterogeneity of the spinal geometric structure. The plane regions along the 3D spinal curve must satisfy two criteria: (i) a criterion of minimum distance between the curve and the regional plane and (ii) a criterion controlling that the curve is continuously plane at the level of the region. The geometric structure of each 3D spinal curve is characterized by the sizes and orientations of regional planes, by the parameters representing flexed regions and by the sizes and functions of zones of transition. Spinal curves of asymptomatic subjects show three plane regions corresponding to spinal curvatures: lumbar, thoracic and cervical curvatures. In some scoliotic spines, four plane regions may be detected.

Age- and sex-related variations in sagittal sacropelvic morphology and balance in asymptomatic adults

INTRODUCTION

Many studies suggest the importance of the sagittal sacropelvic balance and morphology in spinal and hip disorders. This study describes the normal age- and sex-related changes in sacropelvic morphology and balance in a prospective cohort of asymptomatic adults without spinal disorder.

MATERIALS AND METHODS

A prospective cohort of 709 asymptomatic adults without spinal pathology was recruited. There were 354 males and 355 females aged 37.9 ± 14.7 and 35.7 ± 13.9 years, respectively. For each subjects, pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS) were measured from standing lateral radiographs. Ratios of SS to PI (SS/PI), PT to PI (PT/PI), and PT to SS (PT/SS) were also calculated.

RESULTS

There was no significant difference in PI (pelvic incidence), SS (sacral slope), PT (pelvic tilt), PT/PI, SS/PI, or PT/SS between males and females. The mean ± 2 standard deviations (SD) range was 32°-74°, 0°-27°, and 24°-55° for PI, PT and SS, respectively. The mean ± 2 SD range was greater than 0.5 for SS/PI and less than 0.5 for PT/PI. PI was not related to age in either sex group. PT, SS, PT/PI, SS/PI, and PT/SS presented only weak correlation coefficients (r ≤ 0.21) with respect to age.

CONCLUSION

The current study presents the largest cohort of asymptomatic adults in the literature dedicated to the evaluation of sagittal sacropelvic morphology and balance. The range of values corresponding to the mean ± 2 SD can provide invaluable information to clinicians about the normal range of values expected in 95% of the normal population.

Personalized models of bones based on radiographic photogrammetry

The radiographic photogrammetry is applied, for locating anatomical landmarks in space, from their two projected images. The goal of this paper is to define a personalized geometric model of bones, based uniquely on photogrammetric reconstructions. The personalized models of bones are obtained from two successive steps: their functional frameworks are first determined experimentally, then, the 3D bone representation results from modeling techniques. Each bone functional framework is issued from direct measurements upon two radiographic images. These images may be obtained using either perpendicular (spine and sacrum) or oblique incidences (pelvis and lower limb). Frameworks link together their functional axes and punctual landmarks. Each global bone volume is decomposed in several elementary components. Each volumic component is represented by simple geometric shapes. Volumic shapes are articulated to the patient's bone structure. The volumic personalization is obtained by best fitting the geometric model projections to their real images, using adjustable articulations. Examples are presented to illustrating the technique of personalization of bone volumes, directly issued from the treatment of only two radiographic images. The chosen techniques for treating data are then discussed. The 3D representation of bones completes, for clinical users, the information brought by radiographic images.

[Testing of pronation and supination strength in the outpatient setting: a preliminary study]

Dynamometric studies of grip strength are widely used in clinics. We present a clinic dynamometer that can be used to measure pronation and supination moments while the subject being tested is holding a cylindrical handle in neutral pronosupination. One hundred volunteers without any previous history of upper extremity injury were tested in pronation and supination in order to provide a database of strength values and to study variations with respect to sex, age, dominance, weight and height.

Analysis of structural features of deformed spines in frontal and sagittal projections

In the study of spine, two approaches exist. Clinicians still measure directly, either on X-ray films or on digitized images, a small number of angular values characterizing the profile of deformed spines. 3D software programs exist, but they describe the spinal features calculated from a large set number of inputs. An alternative approach is proposed for clinical applications. Frontal and sagittal radiographs are treated separately. Neutral curves are drawn from a small number of records in a small amount of time. Feature parameters accurately describe the spinal shape, and they are the basis for drawing the modeled curve of the spine. These parameters facilitate the follow up of evolutive back pathologies. Several examples display the new technique.

A variability study of computerized sagittal spinopelvic radiologic measurements of trunk balance

OBJECTIVE

The accurate measurement of spinal and pelvic alignment in the sagittal plane is of prime importance for various disorders. Pelvic incidence (PI) is a fundamental anatomic parameter that is specific and constant for each adult individual and is related to pelvic orientation as well as to the size of lumbar lordosis (LL). It is the summation of the sacral slope (SS) and pelvic tilt (PT), two position-dependent variables that determine pelvic orientation in the sagittal plane. The authors have proposed a computer software designed to measure PI, SS, PT, LL, and thoracic kyphosis (TK) on standardized standing lateral digitized x-rays of the spine and pelvis. The purpose of this study was to evaluate the inter- and intraobserver variability of measurements using this software, to determine if it can be used reliably in a clinical environment.

METHODS

The standing lateral x-rays of 30 subjects were randomly selected from the database of two medical institutions. The normal population had standard radiographs on which the various pertinent landmarks were marked by one operator prior to digitization, whereas the scoliotic population had digital radiographs that obviated the need for prior marking of landmarks. Four individuals measured all variables on the 30 x-rays on two occasions, with a 15-day interval between the two sessions. Statistical analysis was done with intraclass correlation coefficients (ICCs).

RESULTS

The ICC measured within observers was between 0.93 and 0.99, whereas the ICC between observers varied between 0.92 and 0.99. The variations observed were similar for normal and scoliotic subjects, and prior marking of the x-rays had no significant influence.

CONCLUSION

We conclude that the variability of measurements with this method is lower than with similar radiologic measures done manually and that the use of this software can be recommended for future clinical and research studies of spinopelvic sagittal balance.

Three-dimensional in vivo displacements of the shoulder complex from biplanar radiography

The goal of this study was to adapt roentgen photogrammetry to in vivo studies of shoulder skeletal motion during arm elevation in the scapular plane. Numerous in vitro and in vivo studies have been published describing shoulder bone movements. They involve plain radiographic measurements and utilize a three-dimensional (3D) approach. Measurements are either direct using pins implanted in bones, or indirect recording points on medical images. Roentgen photogrammetry locates points in space from two projections obtained from two different radiographic incidences. The technique has been applied in vivo by implanting metallic balls in bones. However, to be used as a standard clinical procedure, the technique must be adapted to be less invasive. In vivo photogrammetric reconstruction of known points in 3D space requires that the subject is strictly motionless between the successive radiographic exposures or that the exposures are obtained simultaneously. Methods used in this study were developed to allow subsequent exposures to be used for analysis. Numerical tools have been developed to align the two projections of a point in 3D space which have moved slightly between two successive exposures. The standard photogrammetric technique is completed by geometric modeling of the shoulder complex and humerus, and by the control of their mutual proximity at the level of joints. Bones are modeled as a set of simple volumes linked together using geometric shapes described by shape parameters. The coincidence between real bone contours and radiographic projections of the modeled bone gives the values of the shape parameters and the accurate location in space. Results focus on two different topics: errors related to the use of roentgen photogrammetry with successive exposures, and results obtained by applying roentgen photogrammetry to the in vivo shoulder complex. Results describing shoulder bone and joint displacements are presented for comparison with previously published results. The technique of roentgen photogrammetry can successfully be applied to patients. The radiographic protocol is simple, and data can be obtained easily and quickly from the digitized films. The data obtained from asymptomatic shoulders compared favorably with published values. Future research will focus on comparisons between kinematics of the symptomatic and asymptomatic contralateral limbs in volunteers.

[Geometrical and mechanical analysis of lumbar lordosis in an asymptomatic population: proposed classification]

PURPOSE OF THE STUDY

The main objective of this study was to describe the morphology and the mechanism underlying the organization of lumbar lordosis in terms of position and shape of the pelvis. A classification of lumbar lordosis was proposed based on the orientation of the sacral plane.

MATERIAL AND METHODS

One hundred sixty asymptomatic young adult volunteers were x-rayed in a standardized standing position. A dedicated software was used for analysis of the spine and pelvis. The pelvic parameters were: pelvic incidence, sacral slope, pelvic tilt. The point separating thoracic kyphosis and lumbar lordosis was called the inflexion point. Lumbar lordosis was bounded by the sacral plate and the inflexion point. At the apex, the lumbar curve was divided into two tangent arcs of circle, quantified by an angle and the number of included vertebrae. The lower arc was geometrically equal to the sacral slope. Regarding the vertical line, a lordosis tilt angle was drawn between the inflexion point and the frontal limit of the sacral plate.

RESULTS

The value of the lumbar lordosis was very variable. The best correlation was between lumbar lordosis and sacral slope, then between sacral slope and pelvic incidence. The upper arc of a circle remained constant while the lower arc changed with sacral slope. Good correlations were found between the sacral slope and the position of the apex and between sacral slope and lordosis tilt angle.

DISCUSSION AND CONCLUSION

Regarding sacral slope, lumbar lordosis can be classified into four types. When the sacral slope is low, lumbar lordosis can either be both short and curved with a low apex and a backward tilt (type 1) or both long and flat with a higher position of the apex (type 2). When the sacral slope increases, lumbar lordosis increases in angle and number of vertebrae with an upper apex, with a progressively forward tilt (types 3 and 4). Depending on the shape and position of the pelvis, and because of the relation between sacral slope and pelvic tilt, the morphology of lumbar lordosis could be the main mechanical cause of degenerative diseases of the lumbar spine.

Sagittal morphology and equilibrium of pelvis and spine

A prospective analysis of the sagittal profile of 100 healthy young adult volunteers was carried out in order to evaluate the relationship between the shape of the pelvis and lumbar lordosis and to create a databank of the morphologic and positional parameters of the pelvis and spine in a normal healthy population. Inclusion criteria were as follows: no previous spinal surgery, no low back pain, no lower limb length inequality, no scoliotic deviation. For each subject, a 30 x 90-cm sagittal radiograph including spine, pelvis and proximal femurs in standing position on a force plate was performed. The global axis of gravity was determined with the force plate. Each radiograph was digitized using dedicated software. The spinal parameters registered were values for thoracic kyphosis and lumbar lordosis. The pelvic angles measured were: pelvic incidence, sacral slope and pelvic tilt. The global axis of gravity was on average 9 mm anterior of the center of the femoral heads. The anatomic parameter of pelvic incidence angle varied from 33 degrees to 85 degrees (mean: 51.7 degrees, SD: 11 degrees). The average lumbar lordosis was 46.5 degrees. The average thoracic kyphosis was 47 degrees. We found a statistical correlation between incidence angle and lumbar lordosis (r=0.69, P<0.001) and between sacral slope angle and lumbar lordosis (r=0.75, P<0.001). Spine and pelvis balance around the hip axis in order to position the gravity line over the femoral heads. We propose a scheme of sagittal balance of the standing human body.

Anatomical basis of latissimus dorsi and teres major transfers in rotator cuff tear surgery with particular reference to the neurovascular pedicles

Musculotendinous transfers (MTT) of latissimus dorsi (LD) and teres major (TM), either in isolation or combination, have recently been advocated to treat irreparable rotator cuff tears. The purpose of this study was to (1) review the anatomy of the LD and TM neurovascular pedicles, and (2) undertake experimental MTT to humeral insertions of either supraspinatus or infraspinatus to evaluate tension on their nutrient arteries in six positions of the arm. Twenty-six shoulders were studied, 22 of which had previously been injected with red latex. Gross dissection, using 4.3 x magnification when necessary, was followed by one MTT for each shoulder (11 LD, 6 TM, 9 combined). The anatomy of the LD and TM neurovascular pedicles was consistent with classic descriptions in 85% of cases; "medialisation" of the thoracodorsal artery was observed in 4 specimens. Tension on the teres major artery was not observed in 15 isolated or combined MTTs, while tension on the thoracodorsal artery in at least one arm position was observed in 60% of 20 isolated or combined MTTs. Three factors were found to be associated with tension: medialisation of the thoracodorsal artery, fixation onto the supraspinatus insertion, and 90 degrees abduction combined with internal rotation. The results suggest that tension on the thoracodorsal artery is possible under certain circumstances when an isolated LD or combined MTT is performed to treat irreparable rotator cuff tear.