Design and position control of a robotic brace dedicated to the treatment of scoliosis

This paper’s content focuses on designing and prototyping a robotic brace dedicated to treating scoliosis. Scoliosis is an abnormal spinal curvature affecting 1–3% of children and constitutes a major therapeutic problem. In moderate cases of deformity, passive brace treatment is performed. However, this approach can lead to important patient discomfort. So, we propose a robotic solution providing greater mobility and the possibility of adapting the procedure to each patient. The robotic brace we built and tested is composed of three specific rings adapted to the patient’s torso. Each independent module of two consecutive rings is movable through a Stewart–Gough platform-type mechanism. As the robotic brace is lightweight, it brings better portability and improves the patient’s comfort.

The first part of the paper shows the state of the art of bracing techniques: from passive to active orthoses. Next, the mechatronics of the device is detailed, and the robot’s kinematic models are developed. The motion control principle is given. In the last part, motion tests were administered with a healthy human to validate the brace architecture choice and its position and motion control strategies.

Effects of bracing on pelvic parameters in adolescent idiopathic scoliosis: A retrospective study

To evaluate the effects of Chêneau bracing on Cobb's angle (CA) and spinopelvic parameters in adolescent idiopathic scoliosis (AIS) patients. In this retrospective study, we evaluated 51 AIS patients who received Chêneau bracing treatment between January 2020 and August 2021. The prebracing and in-bracing radiographs were analyzed about the spinopelvic parameters. The CA, pelvic coronal obliquity angle, thoracolumbar kyphosis (TLK), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), sagittal vertical angle, and coronal vertical angle were measured. Paired t-test was used to compare prebracing and in-bracing spinopelvic parameters. The Pearson correlation analysis was used to identify the relationships between the variations in the spinopelvic parameters. The mean age at the initiation of bracing was 13.6 ± 1.5 years. The mean prebracing CA was 24.0° ± 6.3°. There were no statistically significant differences between prebracing and in-bracing measurements of sagittal and coronal vertical angles. However, there were statistically significant differences between the prebracing and in-bracing measurements of the CA, pelvic coronal obliquity angle, TLK, LL, PT, and SS. A significant correlation was observed between PT and thoracolumbar kyphosis variations in the sagittal plane. The pelvic coronal obliquity angle variation was correlated to the prebracing pelvic coronal obliquity angle in the coronal plane. Chêneau's bracing effects of AIS can be extended to the pelvis. Affected by the Chêneau brace, the pelvis should be retro-rotated correspondingly to TLK hyperkyphosis on the sagittal plane, whereas in the coronal plane, pelvic obliquity was improved independently. The effect of Chêneau braces on the pelvic parameters should be fully considered before bracing treatment.

Actuator and Contact Force Modeling of an Active Soft Brace for Scoliosis

Scoliosis is an abnormality of the spinal curvature that severely affects the musculoskeletal, respiratory, and nervous systems. Conventionally, it is treated using rigid spinal braces. These braces are static, rigid, and passive in nature, and they (largely) limit the mobility of the spine, resulting in other spinal complexities. Moreover, these braces do not have precise control over how much force is being applied by them. Over-exertion of force may deteriorate the spinal condition. This article presents a novel active soft brace that allows mobility to the spine while applying controlled corrective forces that are regulated by varying the tensions in elastic bands using low-power light weight twisted string actuators (TSAs). This article focuses on the actuator and contact force modeling of the active soft brace (ASB). The actuator modeling is required to translate the twisting of string in terms of contraction of the string’s length, whereas the contact force modeling helps in estimating the net resultant force exerted by the band on the body using single point pressure/force sensors. The actuators (TSAs) are modeled as helix geometry and validated using a laser position sensor. The results showed that the model effectively tracked the position (contraction in length) with root mean square error (RMSE) of 1.7386 mm. The contact force is modeled using the belt and pulley contact model and validated by building a custom testbed. The actuator module is able to regulate the pressure in the range 0–6 Kpa, which is comparable to 0–8 Kpa pressure regulated in rigid braces. This makes it possible to verify and demonstrate the working principle of the proposed active soft brace.

Sacral Agenesis: A Neglected Deformity That Increases the Incidence of Postoperative Coronal Imbalance in Congenital Lumbosacral Deformities

STUDY DESIGN

A retrospective study.

OBJECTIVES

To identify if there is a link between sacral agenesis (SA) and post-operative coronal imbalance in patients with congenital lumbosacral deformities.

METHODS

This study reviewed a consecutive series of patients with congenital lumbosacral deformities. They had a minimum follow-up of 2 years. According to different diagnosis, they were divided into SA and non-SA group. Comparison analysis was performed between patients with and without post-operative coronal imbalance and risk factors were identified.

RESULTS

A total of 45 patients (18 in SA group and 27 in non-SA group) were recruited into this study, among whom 33 patients maintained coronal balance while 12 demonstrated postoperative coronal imbalance at last follow-up (14.32 ± 7.67 mm vs 35.53 ± 3.91 mm, P < 0.001). Univariate analysis showed that preoperative lumbar Cobb angle, immediate postoperative coronal balance distance and diagnosis of SA were significantly different between patients with and without post-operative coronal imbalance (P < 0.05). Binary logistic regression analysis showed that SA was an independent risk factor for postoperative coronal imbalance.

CONCLUSIONS

As an independent risk factor for postoperative coronal imbalance, high level of suspicion of SA should be aware in children with congenital lumbosacral deformities. Sufficient bone grafts at sacroiliac joint are recommended for SA patients to prevent postoperative coronal imbalance.

Spinal Deformities and Advancement in Corrective Orthoses

Spinal deformity is an abnormality in the spinal curves and can seriously affect the activities of daily life. The conventional way to treat spinal deformities, such as scoliosis, kyphosis, and spondylolisthesis, is to use spinal orthoses (braces). Braces have been used for centuries to apply corrective forces to the spine to treat spinal deformities or to stabilize the spine during postoperative rehabilitation. Braces have not modernized with advancements in technology, and very few braces are equipped with smart sensory design and active actuation. There is a need to enable the orthotists, ergonomics practitioners, and developers to incorporate new technologies into the passive field of bracing. This article presents a review of the conventional passive braces and highlights the advancements in spinal orthoses in terms of improved sensory designs, active actuation mechanisms, and new construction methods (CAD/CAM, three-dimensional (3D) printing). This review includes 26 spinal orthoses, comprised of passive rigid/soft braces, active dynamics braces, and torso training devices for the rehabilitation of the spine.

Non-Fusion Surgical Correction of Thoracic Idiopathic Scoliosis Using a Novel, Braided Vertebral Body Tethering Device: Minimum Follow-up of 4 Years

Anterior vertebral body tethering to effect scoliosis correction in a growing spine has been shown to work with varying degrees of success. This report describes the mid-term results of this technique using a new device composed of a braided ultra-high molecular weight polyethylene (UHMWPE) cord anchored to bone screws applied without segmental compression.

Methods

This was a single-center prospective observational study of an investigational device. Five female patients aged 9 to 12 years with thoracic scoliosis underwent thoracoscopic insertion of the UHMWPE tether. Radiographs and magnetic resonance imaging (MRI) were performed, and the Scoliosis Research Society (SRS)-22 was administered, preoperatively and at regular intervals after surgery, with a minimum of 4 years of follow-up.

Results

All tethering devices spanning the end vertebrae (range, 7 to 8 vertebrae) were implanted successfully. Mean blood loss was 136 mL, and the mean operative time was 205 minutes. The mean preoperative main thoracic Cobb angle was 40.1°. Curve correction of the tethered segment ranged from 0% to 133.3% at 4 years. We observed greater correction in 2 patients with open triradiate cartilage (TRC), achieving full scoliosis correction at 2 years and 121.5% at 4 years. MRI showed improvement in periapical disc wedging morphology and 55% improvement of rotation at 3 years. There were 20 adverse events, of which 16 were mild and 4 were moderate in severity. The 4 moderate events of pneumonia, distal decompensation, curve progression, and overcorrection occurred in 3 patients, 2 of whom required fusion.

Conclusions

Anterior vertebral body tethering resulted in scoliosis deformity correction in the coronal and axial planes, with preservation of curve flexibility. Actual correction by growth modulation was noted only in patients with open TRC, whereas curve stabilization was noted in patients with closed TRC. Overcorrection, curve progression, and distal decompensation are problems with this technique.

Level of Evidence

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Robotic Spine Exoskeleton (RoSE): Characterizing the 3-D Stiffness of the Human Torso in the Treatment of Spine Deformity

Spine deformity is typically treated with a brace that fits around the torso and hips to correct the abnormal curve of the spine. While bracing has been shown to curtail progression of abnormal spine curves, current braces impose several limitations due to their rigid, static, and sensor-less designs: (1) forces and moments exerted by the brace cannot be measured or modulated and (2) the 3-D stiffness of the human torso has not been characterized-these may be important factors to be considered in bracing treatment. We address these limitations using a robotic spine exoskeleton (RoSE), capable of controlling the position/orientation of specific cross sections of the human torso while simultaneously measuring the forces/moments exerted on the body. Eight healthy subjects and two subjects with spine deformity participated in a study to characterize the 3-D stiffness of their torso. The results show that the 3-D stiffness of human torso can be characterized using RoSE and indicated that the spine deformities induce torso stiffness characteristics significantly different from the healthy subjects. These characteristics are curve-specific and present a pronounced asymmetry. These results open up the possibility for the design of spine braces incorporating patient specific torso stiffness characteristics and potential for new interventions using the dynamic modulation of 3-D forces for spine deformity treatment.

INVESTIGATION OF ROBOTIC BRACES OF PATIENTS WITH IDIOPATHIC SCOLIOSIS (IS) — REVIEW OF THE LITERATURE AND DESCRIPTION OF A NOVEL BRACE

Idiopathic scoliosis (IS) is a complex three-dimensional (3D) deformity. The non-operative treatments for IS have been developed for a long time. According to current studies, hard braces are more effective than soft braces for the treatment of scoliosis. Though current braces are proved to be effective for the treatment of IS, there are several shortcomings needed to be overcome: (i) Braces cannot realize precise control over a specific vertebra. (ii) Braces affect cardiopulmonary efficiency (braces limit maximal exercise performance). (iii) The brace is not modulated based on user’s needs. (iv) Braces, including motions during eating, tying shoes, sitting, and standing. (v) Braces apply forces on skin, which causes pain, skin breakdown, and abnormal deformation of bone. In order to solve these boring problems of the current braces, this paper proposed a new intelligent robotic spine brace based on the principle of human biomechanics, three point pressure treatment theory and parallel mechanism theory. This novel brace can offer 3D active dynamic adjustable corrective forces for the treatment of IS and some experiments are employed for verifying the effect of the proposed brace.

Concept design of a novel robotic spinal brace for the treatment of scoliosis

This article presents a novel robotic brace for the treatment of scoliosis. The motivation of this new device comes from the shortcomings in current braces including the rigid brace and the soft brace. Besides, the novel active brace can be used not only for applying active corrective forces on spine, but also for the rehabilitation exercise. The design and control architectures are described for the novel brace and genetic algorithm is used to obtain optimal structural parameters. Two Stewart platforms connected in series form this brace which is driven by 12 electric actuators. Each platform can be controlled in motion or force mode independently. The device can move in six orientations in motion mode and apply six-degree-of-freedom forces on the spine in force mode. In order to evaluate the function and performance of the dynamic brace system, a simple proportional–integral–differential control strategy is employed in both the two control modes. Experimental results depict that the proposed device can respond to the desired position/force commands excellently.

Predictive factors of Osaka Medical College (OMC) brace treatment in patients with adolescent idiopathic scoliosis

Background

Factors influencing clinical course of brace treatment apply to adolescent idiopathic scoliosis (AIS) patients remain unclear. By making clear them, we may select suitable patients for brace treatment and alleviate overtreatment. The purpose of this study was to explore predictive factors of Osaka Medical College (OMC) brace treatment for AIS patients in accordance with the modified standardized criteria proposed by the Scoliosis Research Society (SRS) committee on bracing and non-operative management.

Methods

From 1999 through 2010, 31 consecutive patients with AIS who were newly prescribed the OMC brace and met the modified SRS criteria were studied. The study included 2 boys and 29 girls with a mean age of 12 years and 0 month. We investigated the clinical course and evaluated the impacts of compliance, initial brace correction rate, curve flexibility, curve pattern, Cobb angle, chronological age, and Risser stage to clinical outcomes. The clinical course of the brace treatment was considered progression if ≥6° curvature increase occurred and improvement if ≥6° curvature decrease occurred according to SRS judgment criteria.

Results

The curve progressed in 10 cases, the curve improved in 6 cases, and the curve remained unchanged in 15 cases (success rate: 67.7%). The success rate was statistically higher in the patient group whose instruction adherence rate was greater than 50% as compared with in those 50% or less. Initial brace correction rate, curve flexibility, curve pattern, the magnitude of Cobb angle, chronological age, and Risser stage did not have any significant effect for clinical courses. However, success rate was insignificantly higher in the cases whose Cobb angle in brace was smaller than that in hanging position.

Conclusions

OMC brace treatment could alter the natural history of AIS, however, that was significantly affected by compliance of brace wear.

Review of current technologies and methods supplementing brace treatment in adolescent idiopathic scoliosis

PURPOSE

To report on the current technologies and methods supplementing brace treatment in adolescent idiopathic scoliosis.

METHODS

A comprehensive literature review was performed to determine the effectiveness of bracing, to report on imaging techniques that can assist in the assessment of bracing, to understand the roles of the biomechanical treatment concepts on bracing and to address the importance of the quality of life of the brace wearers.

RESULTS

The effectiveness of bracing still remains controversial. Many technologies are still in development to improve the bracing process and quantify the effects of bracing. Imaging techniques with decreased or no radiation are promising in providing more frequent data on curve progression for patients. Computer-assisted design models have been used for both fitting and manufacturing the brace to patient contours. Ultrasound has been developed as a new means of diagnosing scoliosis and determining the effects of a brace on a patient's spine in real time. The brace treatment outcomes are correlated to the quantity and the quality of brace usage. Compliance monitors and force sensors have been developed to track the quality of brace usage. Improvements to brace wear also require consideration of patient quality of life. Surveys have been developed to describe the effects of family influence and self-image on bracing effectiveness of patient quality of life.

CONCLUSIONS

Bracing remains a highly qualitative process, relying on the empirical judgment of the physicians and orthotists, along with buy-in with the patient. The suggested improvements will help to push bracing into a more evidence-based practice.

Right ventricular function impaired in children and adolescents with severe idiopathic scoliosis

BACKGROUND

Although it is speculated that scoliosis may induce cardiac dysfunction, there is no report about evaluation of cardiac function, especially right cardiac function in patients with scoliosis. Therefore, we evaluated right ventricular function in idiopathic scoliotic patients with mild to severe curves and compared them with healthy children and adolescents matched in age, then explored relationship between scoliosis and right ventricular function.

METHODS

Thirty-seven patients diagnosed with idiopathic scoliosis with a mean age of 16y/o (range, 8-25y/o) and an average spine curve of 77.5°Cobb (range, 30-157°) were studied by echocardiography. TAD was obtained using M-mode echocardiography. Similar examination was performed in a control group of 17 healthy individuals in matched-age. According to the different curve degree, all patients were divided into 3 groups (mild, moderate and severe). Comparison was done among the groups and the relationship between TAD and spine curve of Cobb was analyzed.

RESULTS

Patients with severe scoliosis showed depressed TAD. There was good correlation between TAD and spine curve of Cobb.

CONCLUSIONS

Patients with severe scoliosis showed a significant lower right ventricular systolic function.

Evolution of the curve patterns during brace treatment for adolescent idiopathic scoliosis

The curve pattern of idiopathic scoliosis is important for making decisions concerning bracing. However, whether the curve pattern changes during brace treatment have not been fully documented. The aim of this study was to investigate the changes of curve pattern during brace treatment in skeletally immature patients with adolescent idiopathic scoliosis (AIS).

METHODS

From January 2002 to January 2011, AIS patients treated with a Boston or Milwaukee brace were recruited after meeting the following inclusion criteria: older than 10 years of age at initiation of bracing; having a Cobb angle of 25°-40°; with a Risser sign 0-2; being regularly followed until the weaning of brace or the necessity of surgical treatment; and without history of previous treatment. A total of 130 female and 11 male AIS patients were included. The mean age was 12.9 years at initiation of bracing, and the female patients were, on average, 2.7 months past menarche. The mean follow-up period was 2.6 years (range 1.0-5.5 years). The definitions of changes in curve patterns were divided into four categories as follows: (1) shift of the apex of the main curve; (2) change in the curve span of more than two vertebrae; (3) change in the main curve type with regard to the apex location; and (4) change of curve direction. The patients were divided into two groups. Group A was comprised of patients who had experienced one or more categories of curve pattern changes, and Group B was comprised of those who had not.

RESULTS

Of these 39 patients, 14 had apex shifting, 2 underwent curve span changes, 22 experienced changes in the main curve type, and one female had both changes in the apex and curve span. At the initiation of bracing, patients in Group A demonstrated significantly lower menarchal status (P = 0.018) and lower Risser grade (P = 0.025) than those in Group B. The difference in the percentage of patients who underwent Boston bracing between the two groups was statistically significant (41.5 % for Group A vs. 24.0 % for Group B, P = 0.023).

CONCLUSION

Changes in curve pattern can occur during brace treatment. Patients with less skeletal maturity and those treated with a Boston brace are more susceptible to this phenomenon.

Prospective evaluation of physical activity in patients with idiopathic scoliosis or kyphosis receiving brace treatment

Bracing is an established method of conservative treatment for adolescent idiopathic scoliosis and kyphosis. Compliance among adolescents is frequently inadequate due to the discomfort of wearing a brace, cosmetic issues, and fear on the part of patients and parents that bracing may reduce everyday physical activities. The aim of this prospective, controlled study was to objectify the impact of spinal bracing on daily step activity in patients receiving conservative treatment for adolescent idiopathic scoliosis (AIS) or adolescent kyphosis (AK). Forty-eight consecutive patients (mean age 13.4 ± 2.3 years), consisting of 38 AIS patients (33 girls, 5 boys) and 10 AK patients (6 girls, 4 boys) were included. Once the decision to carry out bracing had been taken and while the patients were waiting for the individual brace to be built, step activity was assessed without braces by means of step activity monitoring (SAM) for seven consecutive days. After 8 weeks of brace wearing, step activity was assessed during regular brace treatment, again for seven consecutive days. In addition, brace-wearing times were simultaneously recorded using temperature probes implanted in the braces to measure compliance. Before and during brace treatment, patients completed the Scoliosis Research Society (SRS-22) questionnaire. The SAM was worn for an average of 12.7 ± 1.5 h/day during the first measurement and 12.3 ± 1.9 h on average during the second measurement. The mean gait cycles (GCs) per day and per hour before treatment were 5,036 ± 1,465 and 395 ± 105, respectively. No significant reduction in step activity was found at the follow-up measurement during bracing, at 4,880 ± 1,529 GCs/day and 403 ± 144 GCs/h. Taking the 23-h recommended time for brace wearing as a basis (100%), patients wore the brace for 72.7 ± 27.6% of the prescribed time, indicating an acceptable level of compliance. Girls showed a higher compliance level (75.6 ± 25.6%) in comparison with boys (56.7 ± 31.9%), although the difference was not significant (P = 0.093). The SRS-22 total score showed no differences between the two measurements (2.57 ± 0.23 vs. 2.56 ± 0.28). Implementing a simultaneous and objective method of assessing step activity and brace-wearing times in everyday life proved to be feasible, and it expands the information available regarding the impact of bracing on patients' quality of life. The results clearly show that brace treatment does not negatively interfere with daily step activity in AIS and AK patients. This is an important finding that should help reduce patients' and parents' worries concerning bracing.

The influence of elastic orthotic belt on sagittal profile in adolescent idiopathic thoracic scoliosis: a comparative radiographic study with Milwaukee brace

Background

The effectiveness of bracing on preventing curve progression in coronal plane for mild and moderate adolescent idiopathic scoliosis (AIS) patients has been confirmed by previous radiographic researches. However, a hypokyphotic effect on the sagittal plane has been reported by a few studies. A relatively increasing number of AIS patients were noticed to wear a new kind of elastic orthotic belt for the treatments of scoliosis without doctors' instructions. We postulate the correcting mechanism of this new appliance may cause flattening of the spine. To our knowledge, no study has investigated the effects of this new orthosis on the sagittal profile of AIS patients. The aim of this study was to evaluate and compare the effects of elastic orthotic belt and Milwaukee brace on the sagittal alignment in AIS patients.

Methods

Twenty-eight female AIS patients with mild or moderate thoracic curves were included in this study. Standing full-length lateral radiographs were obtained in three conditions: natural standing posture without any treatment, with elastic orthotic belt and with Milwaukee brace. Thoracic kyphosis (TK), lumber lordosis (LL) and pelvic incidence (PI) were measured and compared between the above three conditions.

Results

Both elastic orthotic belt and Milwaukee brace can lead to significant decrease of TK, however, the decrease of TK after wearing elastic orthotic belt is significantly larger than that after wearing Milwaukee brace. Compared with no treatment, LL was found to be significantly smaller after wearing Milwaukee brace, however, such significant decrease was not noted after wearing elastic orthotic belt. No significant changes were observed for the PI between 3 conditions.

Conclusions

The elastic orthotic belt could lead to more severe thoracic hypokyphosis when compared with Milwaukee brace. This belt may not be a suitable conservative method for the treatment of mild and moderate AIS patients.

Adult scoliosis surgery outcomes: a systematic review

OBJECT

Appreciation of the optimal management of skeletally mature patients with spinal deformities requires understanding of the natural history of the disease relative to expected outcomes of surgical intervention. Appropriate outcome measures are necessary to define the surgical treatment. Unfortunately, the literature lacks prospective randomized data. The majority of published series report outcomes of a particular surgical approach, procedure, or surgeon. The purpose of the current study was to systematically review the present spine deformity literature and assess the available data on clinical and radiographic outcome measurements.

METHODS

A systematic review of MEDLINE and PubMed databases was performed to identify articles published from 1950 to the present using the following key words: "adult scoliosis surgery," "adult spine deformity surgery," "outcomes," and "complications." Exclusion criteria included follow-up shorter than 2 years and mean patient age younger than 18 years. Data on major curve (coronal scoliosis or lumbar lordosis Cobb angle as reported), major curve correction, Oswestry Disability Index (ODI) scores, Scoliosis Research Society (SRS) instrument scores, complications, and pseudarthroses were recorded.

RESULTS

Forty-nine articles were obtained and included in this review; 3299 patient data points were analyzed. The mean age was 47.7 years, and the mean follow-up period was 3.6 years. The average major curve correction was 26.6 degrees (for 2188 patients); for 2129 patients, it was possible to calculate average curve reduction as a percentage (40.7%). The mean total ODI was 41.2 (for 1289 patients), and the mean postoperative reduction in ODI was 15.7 (for 911 patients). The mean SRS-30 equivalent score was 97.1 (for 1700 patients) with a mean postoperative decrease of 23.1 (for 999 patients). There were 897 reported complications for 2175 patients (41.2%) and 319 pseudarthroses for 2469 patients (12.9%).

CONCLUSIONS

Surgery for adult scoliosis is associated with improvement in radiographic and clinical outcomes at a minimum 2-year follow-up. Perioperative morbidity includes an approximately 13% risk of pseudarthrosis and a greater than 40% incidence of perioperative adverse events. Incidence of perioperative complications is substantial and must be considered when deciding optimal disease management. Although the quality of published studies in this area has improved, particularly in the last few years, the current review highlights the lack of routine use of standardized outcomes measures and assessment in the adult scoliosis literature.