Rotation Of Spine Research Articles

Gait in Pregnancy-related Pelvic girdle Pain: amplitudes, timing, and coordination of horizontal trunk rotations

Walking is impaired in Pregnancy-related Pelvic girdle Pain (PPP). Walking velocity is reduced, and in postpartum PPP relative phase between horizontal pelvis and thorax rotations was found to be lower at higher velocities, and rotational amplitudes tended to be larger. While attempting to confirm these findings for PPP during pregnancy, we wanted to identify underlying mechanisms. We compared gait kinematics of 12 healthy pregnant women and 12 pregnant women with PPP, focusing on the amplitudes of transverse segmental rotations, the timing and relative phase of these rotations, and the amplitude of spinal rotations. In PPP during pregnancy walking velocity was lower than in controls, and negatively correlated with fear of movement. While patients’ rotational amplitudes were larger, with large inter-individual differences, spinal rotations did not differ between groups. In the patients, peak thorax rotation occurred earlier in the stride cycle at higher velocities, and relative phase was lower. The earlier results on postpartum PPP were confirmed for PPP during pregnancy. Spinal rotations remained unaffected, while at higher velocities the peak of thorax rotations occurred earlier in the stride cycle. The latter change may serve to avoid excessive spine rotations caused by the larger segmental rotations.

Ergonomic assessment of neck posture in the minimally invasive surgery suite during laparoscopic cholecystectomy

With the expanding implementation of minimally invasive surgery, the operating team is confronted with challenges in the field of ergonomics. Visual feedback is derived from a monitor placed outside the operating field. This crossover trial was conducted to evaluate and compare neck posture in relation to monitor position in a dedicated minimally invasive surgery (MIS) suite and a conventional operating room. Assessment of the neck was conducted for 16 surgeons, assisting surgeons, and scrub nurses performing a laparoscopic cholecystectomy in both types of operating room. Flexion and rotation of the cervical spine were measured intraoperatively using a video analysis system. A two-question visual analog scale (VAS) questionnaire was used to evaluate posture in relation to the monitor position. Neck rotation was significantly reduced in the MIS suite for the surgeon (p = 0.018) and the assisting surgeon (p < 0.001). Neck flexion was significantly improved in the MIS suite for the surgeon (p < 0.001) and the scrub nurse (p = 0.018). On the questionnaire, the operating room team scored their posture significantly higher in the MIS suite and also indicated fewer musculoskeletal complaints. The ergonomic quality of the neck posture is significantly improved in the MIS suite for the entire operating room team.

The intrinsic stiffness of the in vivo lumbar spine in response to quick releases: Implications for reflexive requirements

Torso muscles contribute both intrinsic and reflexive stiffness to the spine; recent modeling studies indicate that intrinsic stiffness alone is sometimes insufficient to maintain stability in dynamic situations. The purpose of this study was to experimentally test this idea by limiting muscular reflexive responses to sudden trunk perturbations. Nine healthy males lay on a near-frictionless apparatus and were subjected to quick trunk releases from the neutral position into flexion or right-side lateral bend. Different magnitudes of moment release were accomplished by having participants contract their musculature to create a range of moment levels. EMG was recorded from 12 torso muscles and three-dimensional lumbar spine rotations were monitored. A second-order linear model of the trunk was employed to estimate trunk stiffness and damping during each quick release. Participants displayed very limited reflex responses to the quick load release paradigms, and consequently underwent substantial trunk displacements (>50% flexion range of motion and >70% lateral bend range of motion in the maximum moment trials). Trunk stiffness increased significantly with significant increases in muscle activation, but was still unable to prevent the largest trunk displacements in the absence of reflexes. Thus, it was concluded that the intrinsic stiffness of the trunk was insufficient to adequately prevent the spine from undergoing potentially harmful rotational displacements. Voluntary muscular responses were more apparent than reflexive responses, but occurred too late and of too low magnitude to sufficiently make up for the limited reflexes.

Real‐time ultrasound measurements of changes in suboccipital vertebral artery diameter and blood flow velocity associated with cervical spine rotation

The vulnerability of the vertebral artery (VA) to distortion with sustained, full-range cervical spine rotation, resulting in compromised blood flow and possible vertebrobasilar ischaemia, is well recognized. However, few studies have measured such blood flow changes in the parts of the VA downstream from the region of maximum cervical spine rotation: the suboccipital (VA3) and intracranial vertebral arteries. The purpose of this experimental study was to visualize the VA3 and record the changes in its blood flow associated with cervical spine rotation. VA3 diameters and blood flow velocities were measured in the neutral cervical spine position and with active full-range rotation to the left and right, in 35 healthy female subjects, using colour-coded real-time ultrasound. Both left and right VA3 diameters and blood flow velocities decreased significantly on ipsilateral rotation. These values increased non-significantly in the left VA3 and decreased non-significantly in the right VA3 on contralateral rotation. The results of this study suggest that the distortion or compression of VA3 demonstrated by the reduction in diameter on ipsilateral cervical spine rotation, particularly, was sufficient to result in compromised blood flow. A significant stretching effect of VA3, on contralateral rotation, was not demonstrated in these subjects. Nevertheless, these findings add evidence to support the recommendation that sustained, full-range cervical spine rotation should be avoided in professional practice.

Reliability of the Assessment of Lumbar Range of Motion and Maximal Isometric Strength in Patients With Chronic Low Back Pain

Roussel NA, Truijen S, De Kerf I, Lambeets D, Nijs J, Stassijns G. Reliability of the assessment of lumbar range of motion and maximal isometric strength in patients with chronic low back pain. Objective To examine the interobserver reliability of the assessment of lumbar range of motion (ROM) and maximal isometric strength in patients with chronic low back pain (CLBP) using commercially available equipment. Design A prospective repeated-measures design. Setting Ambulatory care in a university hospital. Participants Twelve patients (5 men, 7 women; age range, 20−52y) with CLBP, with a mean visual analog scale score of 31.5±25.8mm, volunteered for the study. The duration of their symptoms was 63±115 months and the mean Oswestry Disability Index score was 31%. Interventions Not applicable. Main Outcome Measures Movements of the lumbar spine were assessed with commercially available equipment. Both the range of motion (ROM) and the maximal isometric strength for flexion, extension, lateroflexion, and rotation of the lumbar spine were evaluated twice to analyze the interobserver reliability. The same test procedure was performed on 2 separate days by 2 investigators who were blinded to the outcome of the assessment of their colleague. The order of investigator was balanced, so that each investigator tested the same number of patients as first investigator. Results The intraclass correlation coefficient varied between .91 and .98 for the measurements of the lumbar ROM and was between .93 and .97 for all the strength measurements. Post hoc power analysis confirmed previous power analysis, that is, despite the small sample size, an excellent power was found for the observed interobserver reliability coefficients (power range, 0.93−1.00). No learning effect was found when comparing the results of the second measurement with the first measurement ( P>.05). Conclusions The interobserver reliability is excellent for the measurement of the ROM of the lumbar spine and for the maximal isometric strength using specific devices in patients with CLBP.

Effects of Age on Spinal Rotation during a Driving Task

Many older adults experience declines in their flexibility, which in turn can affect their safe operation of a vehicle and their driving performance. Previous research has shown that reduced trunk flexibility is associated with greater accident risks. To explore further questions about and measures of spinal flexibility, differences in spinal flexibility between younger and older drivers were explored in two contexts: a stretching exercise and a real driving maneuver. Results indicated that younger drivers had on average greater stretch spinal flexibility than older drivers, but that during the driving maneuver, study participants did whatever necessary, such as bracing themselves on the seatback or steering wheel, to overcome any flexibility limitations to complete the driving task. Using a multivariate regression mode, the degree of spinal rotation in the stretch and driving tasks were significantly affected by age and by the use of the vehicle to brace while rotating. In the stretch tasks, self-reported health and driving frequency were jointly statistically significant predictors of degree of rotation. In terms of driving, however, the use of bracing suggests that drivers may have evolved strategies to compensate for any physical limitations they may experience to continue driving.

Are coupled rotations in the lumbar spine largely due to the osseo-ligamentous anatomy?—A modeling study

Prior studies have found that primary rotations in the lumbar spine are accompanied by coupled out-of-plane rotations. However, it is not clear whether these accompanying rotations are primarily due to passive (discs, ligaments and facet joints) or active (muscles) spinal anatomy. The aim of this study was to use a finite element (FE) model of the lumbar spine to predict three-dimensional coupled rotations between the lumbar vertebrae, due to passive spinal structures alone. The FE model was subjected to physiologically observed whole lumbar spine rotations about in vivo centres of rotation. Model predictions were validated by comparison of intra-discal pressures and primary rotations with in vivo measurements and these showed close agreement. Predicted coupled rotations matched in vivo measurements for all primary motions except lateral bending. We suggest that coupled rotations accompanying primary motions in the sagittal (flexion/extension) and transverse (axial rotation) planes are primarily due to passive spinal structures. For lateral bending the muscles most likely play a key role in the coupled rotation of the spine.

Viscoelastic stresses on anisotropic annulus fibrosus of lumbar disk under compression, rotation and flexion in manual treatment

Twisting (spinal rotation) and bending (flexion) are commonly reported as triggers for low back pain. This paper addresses whether the twisting stress on the annulus fibrosus of the lumbar disk is greater or less than the bending stress for the same angle of twist or bending. Stress-strain relation for transversely isotropic material is applied to the transversely isotropic annulus fibrosus of the lumbar disk to analyze the viscoelastic stresses produced due to 6% compression, 10 degrees twist and 10 degrees bending. The bending stress is 450 times greater than the twisting stress for the same angle of twist or bending of the annulus fibrosus. The twisting and bending moments increase two-fold in quick maneuvers lasting 0.1s (as in high velocity manipulations), compared to slow maneuvers lasting 60s. From biomechanical perspective, in situations where both flexion and spinal rotation occur, the stress on the intervertebral disk is markedly higher with flexion compared to rotation. In patients with low back pain that has a disk mediated (discogenic) component, manipulation and mobilization therapies should avoid flexion to minimize stress on the disks. This is particularly relevant for high velocity manipulations where the stress on the disk is doubled for both flexion and rotation. The results in this paper can help guide manual therapists to adjust their treatments to minimize stress on the intervertebral disk.

Is mechanical deformation of the suboccipital vertebral artery during cervical spine rotation responsible for vertebrobasilar insufficiency?

The atlanto-axial region of the vertebral artery (VA) has traditionally been considered at risk for injury during cervical spine rotation, leading to compromised blood flow to the hindbrain and vertebrobasilar insufficiency or ischaemia (VBI). The anatomical relationships of the suboccipital VA (VA3) and related haemodynamic changes associated with cervical spine movements have been neglected, however. The present review aims to provide a new perspective on possible causes of reduced blood flow to the hindbrain, with particular reference to the functional anatomy of VA3 and related biomechanics of cervical spine rotation, to inform evidence-based practice. To support the hypothesis that it is VA3, not the VA in the atlanto-axial region, that is compressed or stretched during cervical spine rotation, current studies of blood flow changes in the VA distal to the region of rotation and possible arterial deformation were retrieved, using AMED, CINAHL, Embase, Pedro and PubMed, and reviewed. Possible sites for VA3 deformation, based on a re-examination of its anatomy and biomechanics, are described. However, no research reports of VA3 blood flow measurements associated with cervical spine rotation have been published to date. Five studies on blood flow changes in the intracranial VA after cervical spine rotation were reviewed. The subjects for four of these reports were young, healthy individuals, and the fifth included older patients and young non-patients. The analysis of these studies demonstrated that more rigorous control of variables is necessary before meaningful conclusions can be made. The paucity of studies of VA3 emphasises the need for research based on informed understanding of the anatomy and biomechanics of this area. This view on mechanical deformation of VA3 associated with cervical spine rotation as a possible cause of compromised blood flow to the hindbrain and VBI provides further argument for avoiding full-range or sustained cervical spine rotation in clinical practice.

Thoracic Insufficiency Syndrome and Exotic Scoliosis

Most spinal curves can be described as standard scoliosis and are due to adolescent idiopathic scoliosis. In patients with standard scoliosis, the thorax is usually spacious, having achieved most of its adult volume through growth, and has near normal vital capacity. Standard scoliosis is characterized on an anteroposterior radiograph by the level and degree of the curve and is treated by bracing or definitive spinal fusion to effect a decrease in the Cobb angle. Treatment has a negligible effect on thoracic growth or long-term pulmonary outcome. Exotic scoliosis describes an early-onset spinal deformity that is more complex in nature, often associated with a thorax that has been distorted by spinal lordosis and curve rotation, thus having a volume-depletion deformity as well as thoracic growth inhibition with indirect adverse effects on lung growth (Fig. 1). Exotic means “foreign,” “outlandish,” or “alien,” and the curves of exotic scoliosis are easily recognizable. In the coronal plane, this scoliosis is not only a “lateral curve” but, from a three-dimensional thoracic viewpoint, can be considered a lateral flexion contracture of the thorax with volume depletion on the concave side and often additional volume depletion on the convex side, in the transverse plane, from a windswept deformity of the thorax. Primary rib-cage abnormalities, such as absent or fused ribs, add further thoracic disability. The typical treatment approaches to spine deformity may be impractical for the treatment of exotic scoliosis because of potential spine and thoracic growth inhibition from early fusion or because of additional comorbidities (e.g., the bone stock may be insufficient or too osteopenic to hold the instrumentation, the patient may be too small for standard spinal implants, or the lung function may be so poor that the patient would not survive surgery). In addition, a spine fusion may be unable to address the three-dimensional …

A kinematic and anthropometric study of the upper cervical spine and the occipital condyles

The center of rotation (COR) of the upper cervical spine (UCS) is an important biomechanical landmark that is used to determine upper neck moment, particularly when evaluating injury risk in the automotive environment. However, neither the location of the UCS CORs nor the occipital condyles (OCs), which are frequently the referenced landmark for UCS CORs, have been measured with respect to known cranial landmarks. This study determines the CORs using pure bending (±3.5 N m), 3D digitization, and image analysis. Landmarks digitized included the OCs, external auditory meatus (EAM), infraorbital foramen, zygion, nasion, and the foramen magnum. The centroid of each occipital condylar surface (area 301±29.8 mm 2; length 25.4±3.2 mm) was located 18.4 mm posterior, 54.4 mm medial, and 31.0 mm inferior of the EAM. The UCS CORs were distinct: On average, OC–C1 CORs (22.5 mm posterior and 22.6 mm inferior to the left EAM) were superior and more posterior of OCs; C1–C2 CORs (7.4 mm posterior and 46.7 mm inferior to the left EAM) were inferior and more anterior of OC; and OC–C2 CORs (17.0 mm posterior and 33.1 mm inferior to the left EAM) were aligned with OC. There was a statistically significant difference between the percentage of UCS rotation in C1–C2 and OC–C1; 45% of the flexion and 71% of the extension occurred in OC–C1. Details of an anatomical variant with two pairs of distinct condylar surfaces are also presented.

Normative Values for Active Lumbar Range of Motion in Children

The purpose of this study was to establish normative values for active lumbar movement in children five, seven, nine, and 11 years of age. End range active flexion, extension, and right- and left-side bending and rotation of the lumbar spine were measured for 225 normally developing children (116 girls, 109 boys) using the Back Range of Motion (BROM II) device. Means were determined for each motion by age and sex. Group relationships were explored. Normative values for lumbar spine cardinal plane movements were identified. Reduced lumbar movement was found in the 11-year-old group compared with the five-year-old group in active lumbar flexion in girls and in active lumbar side bending and rotation in both girls and boys. Normative data for cardinal plane movements of the lumbar spine provide therapists with a baseline for assessing spinal mobility of children of these ages.

Doppler insonation of vertebral artery blood flow changes associated with cervical spine rotation: Implications for manual therapists

The controversy related to changes in vertebral artery (VA) blood flow associated with rotation of the cervical spine and the implications for professional practice is still of concern to manual therapists. The aim of this review of the literature is, first, to assess current evidence of altered VA blood flow following cervical spine rotation in persons with and without signs and symptoms of vertebrobasilar ischemia/insufficiency (VBI). Second, any reported, related alterations in blood flow that may have consequences for the individual will be discussed to assist manual therapists in pretreatment risk assessment of patients. The most commonly used noninvasive, in vivo technique for measuring blood flow is Doppler ultrasonography. Of the 88 relevant papers retrieved by a systematic literature search covering the past 50 years, 20 studies reported measurement of VA blood flow related to cervical spine rotation. A critical analysis of these reports revealed that there is no standardization of methods used (heterogeneous samples, small sample sizes, various measurement positions and instruments, and different parts of the VA measured); no consensus of findings (no change, and a significant reduction in contralateral VA blood flow, with or without VBI); and no correlations found between rotation, blood flow, and VBI. Nevertheless, this review is of value in increasing our knowledge of the possible mechanisms and consequences of repeated minor arterial trauma and of blood flow changes related to rotational movements used in cervical manual therapy. It highlights, too, the need for caution in the interpretation of pretreatment risk assessment outcome measures.

Manual fixation versus locking during upper cervical segmental mobilization.: Part 2: An in vitro three-dimensional arthrokinematic analysis of manual axial rotation and lateral bending mobilization of the atlanto-axial joint

Background Three-dimensional kinematic aspects of coupled motion during manual cervical mobilization have not previously been studied. Using an in vitro 3D-motion analysis method, the kinematic effects of two different segmental techniques for axial rotation and lateral bending mobilization of the upper cervical spine were investigated as a second part of the study (in part one, kinematic effects of flexion-extension mobilization have been investigated). Methods Axial rotation and lateral bending mobilization of the atlanto-occipital and atlanto-axial segments were analysed in vitro using an electromagnetic tracking device. Local reference frames were defined based on bony reference points that were registered using a 3D-digitizing stylus. Five embalmed and one fresh specimen were analysed. Segmental motion was registered simultaneously in the atlanto-occipital and the atlanto-axial joints during manual mobilization through the full range of axial rotation and lateral bending mobility. The 3D-kinematic aspects during regional mobilization were compared with those during segmental mobilization with manual fixation and during segmental mobilization using a locking technique. Results During both segmental axial rotation techniques of the atlanto-axial joint, a significant reduction of the coupled lateral bending and flexion-extension motion was observed. The locking technique also induced an increase in the main axial rotation component. During lateral bending mobilization of the atlanto-axial joint, the manual fixation technique reduced the effect on the coupled flexion-extension component significantly. Interpretations These results suggest that for manual segmental axial rotation and lateral bending mobilization of the upper cervical spine segmental manual fixation or locking may be preferred in different situations depending on the desired effects. This study brings additional information to the data provided by part 1 of this study on the 3D-arthrokinematic effects of flexion-extension mobilization.

Ex Vivo and In Vitro Determination of the Axial Rotational Axis of the Human Thoracic Spine

Different geometrical and biomechanical evaluations were performed to determine the axial rotational axis of the thoracic spine. Our research group has been dealing with the determination of the axial rotational axis of the thoracic spine. Here, we would like to present the geometrical and experimental results of our trials. With our experiments, we are trying to evaluate the contradictions of the related literature. In the present state, we know quite a lot about the biomechanics of healthy and pathologic spines. Nevertheless, for a seemingly simple question like the position of the axial rotation of the thoracic spine, the literature gives contradicting results. During correction of a scoliotic deformity, when trying to correct the pathologic rotation, not knowing the physiologic rotation can be hazardous. We wanted to clarify this question, so we examined the thoracic spine in many different ways. First, we examined the problem from a geometrical point of view then we modeled the different rotational axes by studying the change in volume of the spinal canal. Finally, we used cadaver spines that we rotated and examined with radiographs and digital pictures. Based on the results, we made the following establishments: most of the center points fell on the anterior half of the vertebral body or into the spinal canal, basically on the midsagittal axis of the vertebra. The rib cage has a significant effect on the place of the axis. After removing the ribs, the axis of axial rotation moved forward. After evaluating the results, we determined that the most likely place for the rotational axis is on the median-sagittal plane, in the anterior portion of the spinal canal.

A segmental radiological study of the spine and rib--cage in children with progressive infantile idiopathic scoliosis.

BackgroundThe role of rib cage in the development of progressive infantile idiopathic scoliosis (IIS) has not been studied previously. No report was found for rib growth in children with IIS. These findings caused us to undertake a segmental radiological study of the spine and rib-cage in children with progressive IIS. The aim of the present study is to present a new method for assessing the thoracic shape in scoliotics and in control subjects and to compare the findings between the two groups.Materials and methodsIn the posteroanterior (PA) spinal radiographs of 24 patients with progressive IIS, with a mean age of 4.1 years old, the Thoracic Ratios (TRs) (segmental convex and concave TRs), the Cobb angle, the segmental vertebral rotation and vertebral tilt were measured. In 233 subjects, with a mean age of 5.1 years old, who were used as a control group, the segmental left and right TRs and the total width of the chest (left plus right TRs) were measured in PA chest radiographs. Statistical analysis included Mann-Whitney, Spearman correlation coefficient, multiple linear regression analysis and ANOVA.ResultsThe comparison shows that the scoliotic thorax is significantly narrower than that of the controls at all spinal levels. The upper chest in IIS is funnel-shaped and the vertebral rotation at T4 early in management correlates significantly with the apical vertebral rotation at follow up.ConclusionThe IIS thorax is narrower than that of the controls, the upper chest is funnel-shaped and there is a predictive value of vertebral rotation at the upper limit of the thoracic curve of IIS, which reflects, impaired rib control of spinal rotation possibly due to neuromuscular factors, which contribute also to the funnel-shaped chest.

Functionally Oriented Rehabilitation Program for Patients with Fibromyalgia

To evaluate function and disability in patients with fibromyalgia before and after participation in a functionally oriented, multidisciplinary, 8-wk treatment program. A total of 23 patients who met American College of Rheumatology criteria for the diagnosis of fibromyalgia were enrolled in the study. Outcome measures included: range of motion, 6-min walk test, a modified Fibromyalgia Impact Questionnaire, a modified SF-36 Physical Functioning Scale, and the Fibromyalgia Health Assessment Questionnaire. Pretreatment and posttreatment scores were analyzed using paired t tests. All subjects completed the program, and there were no reported injuries. Three subjects failed to complete the survey instruments at the conclusion of the study. Intention to treat analysis including these subjects was carried out but did not significantly change results. For the remaining subjects (n = 20), a significant improvement was found on the Physical Functioning Scale (P = 0.01). Trends toward improvement on the Fibromyalgia Impact Questionnaire (P = 0.40) and Fibromyalgia Health Assessment Questionnaire (P = 0.14) were seen but did not achieve statistical significance. Range of motion testing revealed significant improvements in lumbar spine extension (P < 0.001), straight-leg raise (P < 0.001), cervical spine flexion (P < 0.01), cervical spine rotation (P < 0.05), and cervical spine side bending (P < 0.05). Distance traveled during the 6-min walk test increased significantly (P < 0.01), whereas perceived exertion as measured by the Borg scale did not change. There were no injuries or other adverse consequences of the program. This study utilized multiple functional outcome measures to demonstrate improved function and decreased disability in patients with fibromyalgia. Our patients reported significantly improved physical function after participation in the 8-wk intensive multidisciplinary treatment program. This progressive, functionally based exercise training program was well tolerated by all participants and outlines an effective exercise prescription for patients with fibromyalgia. Fibromyalgia patients in this study responded favorably to a treatment program that focused on function instead of pain.

Reliability of the Assessment of Lumbar Range of Motion and Maximal Isometric Strength

Roussel N, Nijs J, Truijen S, Breugelmans S, Claes I, Stassijns G. Reliability of the assessment of lumbar range of motion and maximal isometric strength. Objective To examine the interobserver reliability and intrasubject variability of the assessment of lumbar range of motion (ROM) and maximal isometric strength in asymptomatic subjects by using commercially available equipment. Design A cross-sectional repeated-measures design. Setting Ambulatory care in a university hospital. Participants Convenience sample of 61 asymptomatic healthy subjects aged 20 to 55 years. Interventions Not applicable. Main Outcome Measures Six movements of the lumbar spine were assessed with commercially available equipment. Both the ROM and the maximal isometric strength for flexion, extension, lateroflexion, and rotation of the lumbar spine were assessed by 2 investigators who were blinded to the outcome of the assessment performed by their colleague. Results The intraclass correlation coefficient (ICC) was above .95 for all the strength measurements. For the assessment of the ROM of the lumbar spine, the ICC varied between .77 and .94. There was a significant intrasubject variability for 8 of 12 measurements. Conclusions The interobserver reliability is excellent for the measurement of the maximal isometric strength and good for the assessment of the ROM of the lumbar spine. There is a significant intrasubject variability, which requires the use of the mean or the best value of different trials.

In vivo study of the kinematics in axial rotation of the lumbar spine after total intervertebral disc replacement: long-term results: a 10–14 years follow up evaluation

We did not find any in vivo study of spinal segment kinematics after disc replacement, especially over the long term. In vitro studies did show that it restores almost normal kinematics except for axial rotation. The goal of this study is to develop a new technique in order to analyse axial rotation of a spinal segment, in vivo, after total disc replacement. A comparative retrospective study of motion in axial rotation at L4L5 level was carried out on 17 patients with artificial discs versus six healthy volunteers. Five patients carried one prostheses at L4L5 level and 12 carried two prosthesis at L4L5 and L5S1 levels. The follow up ranged from 10.8 to 14.3 years (average 12.4+/-1, median 12.6). Dynamic radiographs in axial rotation were made using a special protocol. A new technique associating a stereographic method and image processing software was developed in order to evaluate the range of motion in axial rotation as well as the mechanical coupling. The standard deviation of angular measurements was 1.8 degrees . Eleven (65%) patients had a normal mobility in torsion, identical to those of the volunteers and of the literature, whereas six (35%) had an abnormal increased mobility. If only one disc was replaced, mobility in torsion was identical to that of the volunteers, in the case of two replaced discs, 50% (6/12) of the patients had an abnormal increased mobility. In the sub-group of normal mobility, the coupling was identical to that of the volunteers. In the sub-group of increased mobility, the coupling was different with a strong flexion (10 degrees ), increased by about 7 degrees (P<0.001). The implementation of only one discal prosthesis SB Charité seems to restore kinematics close to that of the healthy volunteers and comparable to the literature. The implementation of two adjacent prostheses does not restore normal kinematics in 50% of the cases. It is probable that the existence of active stabilizing elements explains the difference with the in vitro studies carried out beforehand.

DORSAL SURGICAL CORRECTION OF SCOLIOSIS WITH CDI WITH AND WITHOUT PRELIMINARY HALO-PELVIC-TRACTION

Objective. To estimate results of surgical treatment of mobile forms of high-grade scoliosis by CDI with preliminary halo-pelvic-traction and without it. Material and Methods. The outcomes of surgery for III–IV Grade scoliosis in 70 patients were analyzed. One stage dorsal deformity correction with CDI combined with posterior spinal fusion was performed in 38 patients. In 32 patients the instrumented correction was preceded by halo-pelvic-traction without anterior release. Mobility of the spine was estimated with Kazmin’s stability index, mobility index, correction at traction, and index of postoperative correction. Results. In Group 1 the Kazmin’s index of stability was 0.82, and in Group 2 – 0.85. The mobility index was 55.96 in Group 1, and 62.90 in Group 2. Correction at traction was 44.04 in Group 1, and 37.10 % in Group 2. In Group 1 the achieved correction was 56.4 % and in Group 2 – 55.4 %. In Group 1 a deformity correction with CDI exceeded initial spine mobility by 20 % and in Group 2 – by 40 %. In both groups a disc height increased by 40 % on a concave side and decreased by 20 % on a convex side. Lordoscoliosis predominated in both groups (17 patients in Group 1, 15 – in Group 2). Kyphoscoliosis was in 9 patients in Group 1, and in 8 – in Group 2. Postoperative sagittal profile became normal in a majority of patients in both groups. There was no considerable derotation in patients of Group 1. In Group 2 a rotation of the whole spine in one direction was recorded after halo-pelvic-traction. Conclusion. The CDI allows achieving significant curve correction in patients with mobile forms of scoliosis (more than 50 %). Preliminary halo-pelvic-traction without anterior release could be effective in patients with severe and rather mobile forms of scoliosis.