Health-related quality of life in early onset scoliosis patients treated with the spring distraction system: what to expect in the first 2 years after surgery

PURPOSE

The Spring Distraction System (SDS) is a novel "growth-friendly" implant for the treatment of Early-Onset Scoliosis (EOS). This prospective study aims to determine the evolution of the "24-Item Early-Onset Scoliosis Questionnaire" (EOSQ-24) scores during 2-year follow-up after SDS surgery. Secondary aims include investigating the relation between EOSQ-24 scores and EOS etiology, and evaluating the impact of an unplanned return to the operating room (UPROR) on HRQoL.

METHODS

All SDS patients with at least 2-year follow-up were included. Caregivers completed the EOSQ-24 pre-operatively, post-operatively, and at 6, 12, and 24 month follow-up. Mean total and -domain scores were graphed over time. Repeated-measures ANOVA analyzed the influence of etiology on EOSQ-24 scores. Multiple regression analyzed associations between UPRORs and EOSQ-24 scores.

RESULTS

Forty-nine patients were included. Mean total EOSQ-24 scores decreased from 70 pre-operatively to 66 post-operatively, then gradually increased to 75 (24 months). Most domains exhibited changes over time, with initial declines, but eventually surpassing pre-operative levels after 2-year follow-up. Neuromuscular/Syndromic patients had lower scores, but showed similar improvements over time compared with other etiologies. Multiple regression showed lower Parental Burden domain score (- 14 points) in patients with UPRORs, although no significant reductions were found in total score, or in other domains.

CONCLUSION

HRQoL decreases immediately following SDS surgery but quickly recovers and exceeds pre-operative levels at 2-year follow-up in all domains. Neuromuscular/Syndromic patients have lower initial scores, but progress similarly over time. UPRORs do not influence EOSQ-24 scores, except for a negative impact on the Parental Burden domain in the short term.

LEVEL OF EVIDENCE

III.

Monitoring of Curve Progression in Patients with Adolescent Idiopathic Scoliosis Using 3-D Ultrasound

OBJECTIVE

The aim of the work described here was to determine whether 3-D ultrasound can provide results comparable to those of conventional X-ray examination in assessing curve progression in patients with adolescent idiopathic scoliosis (AIS).

METHODS

One hundred thirty-six participants with AIS (42 males and 94 females; age range: 10-18 y, mean age: 14.1 ± 1.9 y) with scoliosis of different severity (Cobb angle range: 10º- 85º, mean: of 24.3 ± 14.4º) were included. Each participant underwent biplanar low-dose X-ray EOS and 3-D ultrasound system scanning with the same posture on the same date. Participants underwent the second assessment at routine clinical follow-up. Manual measurements of scoliotic curvature on ultrasound coronal projection images and posterior-anterior radiographs were expressed as the ultrasound curve angle (UCA) and radiographic Cobb angle (RCA), respectively. RCA and UCA increments ≥5º represented a scoliosis progression detected by X-ray assessment and 3-D ultrasound assessment, respectively.

RESULTS

The sensitivity and specificity of UCA measurement in detecting scoliosis progression were 0.93 and 0.90, respectively. The negative likelihood ratio of the diagnostic test for scoliosis progression by the 3-D ultrasound imaging system was 0.08.

CONCLUSION

The 3-D ultrasound imaging method is a valid technique for detecting coronal curve progression as compared with conventional radiography in follow-up of AIS. Substituting conventional radiography with 3-D ultrasound is effective in reducing the radiation dose to which AIS patients are exposed during their follow-up examinations.

The Dutch version of the Spinal Appearance Questionnaire for adolescents with idiopathic scoliosis: patient-based cross-cultural adaptation and measurement properties evaluation

PURPOSE

Adolescent idiopathic scoliosis (AIS) affects the appearance of spine and trunk. The Spinal Appearance Questionnaire (SAQ) assesses the perception of appearance in AIS patients. The aim of this study is to translate and culturally adapt the recommended short version of the SAQ into Dutch and to test its measurement properties.

METHODS

A Dutch SAQ (14-item; appearance and expectations domains) was developed following guidelines for translation and cross-cultural adaptation. The COSMIN Study Design checklist was used for measurement properties evaluation. In this multicenter study, the Dutch SAQ, SRS-22R and NPRS (back pain) were administered to 113 AIS patients (aged 15.4 years [SD 2.2], 21.2% male). Floor and ceiling effects were evaluated for content analysis. For reliability, internal consistency (Cronbach's alpha) and test-retest reliability (ICC; n = 34) were evaluated. Predefined hypotheses of relationships with other questionnaires and between subgroups based on scoliosis severity (radiological and clinical) were tested for construct validity. Exploratory factor analysis (EFA) was performed to investigate the validity of the underlying structure of this 14-item questionnaire.

RESULTS

No floor and ceiling effects were found for domains and total scores. Cronbach's alpha ranged from 0.84 to 0.89. ICCs varied from 0.76 to 0.77. For construct validity, 89% (8/9) of the predefined hypotheses were confirmed. Significant higher scores for the appearance domain were found for subgroups based on radiological (Cobb angle; > 25.0°) and clinical outcomes. (Angle of Trunk Rotation; > 9.0°). A two-factor structure was found (EV 5.13; 36.63% explained variance).

CONCLUSION

The Dutch SAQ is an adequate, valid and reliable instrument to evaluate patients' perception of appearance in AIS.

LEVEL OF EVIDENCE

Level I-diagnostic studies.

Automatic generation of subject-specific finite element models of the spine from magnetic resonance images

The generation of subject-specific finite element models of the spine is generally a time-consuming process based on computed tomography (CT) images, where scanning exposes subjects to harmful radiation. In this study, a method is presented for the automatic generation of spine finite element models using images from a single magnetic resonance (MR) sequence. The thoracic and lumbar spine of eight adult volunteers was imaged using a 3D multi-echo-gradient-echo sagittal MR sequence. A deep-learning method was used to generate synthetic CT images from the MR images. A pre-trained deep-learning network was used for the automatic segmentation of vertebrae from the synthetic CT images. Another deep-learning network was trained for the automatic segmentation of intervertebral discs from the MR images. The automatic segmentations were validated against manual segmentations for two subjects, one with scoliosis, and another with a spine implant. A template mesh of the spine was registered to the segmentations in three steps using a Bayesian coherent point drift algorithm. First, rigid registration was applied on the complete spine. Second, non-rigid registration was used for the individual discs and vertebrae. Third, the complete spine was non-rigidly registered to the individually registered discs and vertebrae. Comparison of the automatic and manual segmentations led to dice-scores of 0.93-0.96 for all vertebrae and discs. The lowest dice-score was in the disc at the height of the implant where artifacts led to under-segmentation. The mean distance between the morphed meshes and the segmentations was below 1 mm. In conclusion, the presented method can be used to automatically generate accurate subject-specific spine models.

Comment on Burgos et al. Fusionless All-Pedicle Screws for Posterior Deformity Correction in AIS Immature Patients Permit the Restoration of Normal Vertebral Morphology and Removal of the Instrumentation Once Bone Maturity Is Reached. J. Clin. Med. 2023, 12, 2408

With great interest, we read the recently published paper "Fusionless All-Pedicle Screws for Posterior Deformity Correction in AIS Immature Patients Permit the Restoration of Normal Vertebral Morphology and Removal of the Instrumentation Once Bone Maturity is Reached" by Burgos et al. [...].

The Risk and Benefits of Various Innovations in Fusion and Fusionless Surgery for AIS

Adolescent idiopathic scoliosis is the most common variety of the condition, constituting a three-dimensional deformity of the spine and chest that primarily affects otherwise healthy adolescents [...].

Did the dislocation risk after primary total hip arthroplasty decrease over time? A meta-analysis across six decades

BACKGROUND

While continuous optimization is attempted to decrease the incidence of dislocation after total hip arthroplasty (THA), dislocation remains a major complication. This meta-analysis aims to analyze the evolution of the dislocation risk after primary THA over the decades and to evaluate its potential publication bias.

PATIENTS AND METHODS

A systematic search was performed according to the PRISMA guidelines for this meta-analysis in the literature published between 1962 and 2020. MEDLINE, Cochrane and Embase databases were searched for studies reporting the dislocation risk and length of follow-up. Studies that reported on revision rates only and did not mention separate dislocations were excluded. All study designs were eligible. Study quality was assessed by existing quality assessment tools adjusted for arthroplasty research. Overall risk and yearly dislocation rates were calculated and related to historical time frame, study design, sample size and length of follow-up.

RESULTS

In total, 174 studies were included with an overall moderate quality. In total there were 85.209 dislocations reported in 5.030.293 THAs, showing an overall dislocation risk of 1.7%, with a median follow-up of 24 months. The overall dislocation risk classified per decade decreased from 3.7% in 1960-1970 to 0.7% in 2010-2020. The yearly dislocation rate decreased from 1.8 to 0.7% within these same decades. There was no significant correlation between the reported dislocation risk and the duration of follow-up (p = 0.903) or sample size (p = 0.755). The reported dislocation risk was higher in articles with registry data compared to other study designs (p = 0.021).

CONCLUSION

The dislocation risk in THA has been decreasing over the past decades to 0.7%. Non-selective registry studies reported a higher dislocation risk compared to studies with selective cohorts and RCTs. This indicates that the actual dislocation risk is higher than often reported and 'real-world data' are reflected better in large-scale cohorts and registries.

Imaging Methods to Quantify the Chest and Trunk Deformation in Adolescent Idiopathic Scoliosis: A Literature Review

Background context: Scoliosis is a three-dimensional deformity of the spine with the most prevalent type being adolescent idiopathic scoliosis (AIS). The rotational spinal deformation leads to displacement and deformation of the ribs, resulting in a deformity of the entire chest. Routine diagnostic imaging is performed in order to define its etiology, measure curve severity and progression during growth, and for treatment planning. To date, all treatment recommendations are based on spinal parameters, while the esthetic concerns and cardiopulmonary symptoms of patients are mostly related to the trunk deformation. For this reason, there is a need for diagnostic imaging of the patho-anatomical changes of the chest and trunk in AIS. Aim: The aim of this review is to provide an overview, as complete as possible, of imaging modalities, methods and image processing techniques for assessment of chest and trunk deformation in AIS. Methods: Here, we present a narrative literature review of (1) image acquisition techniques used in clinical practice, (2) a description of various relevant methods to measure the deformity of the thorax in patients with AIS, and (3) different image processing techniques useful for quantifying 3D chest wall deformity. Results: Various ionizing and non-ionizing imaging modalities are available, but radiography is most widely used for AIS follow-up. A disadvantage is that these images are only acquired in 2D and are not effective for acquiring detailed information on complex 3D chest deformities. While CT is the gold standard 3D imaging technique for assessment of in vivo morphology of osseous structures, it is rarely obtained for surgical planning because of concerns about radiation exposure and increased risk of cancer during later life. Therefore, different modalities with less or without radiation, such as biplanar radiography and MRI are usually preferred. Recently, there have been advances in the field of image processing for measurements of the chest: Anatomical segmentations have become fully automatic and deep learning has been shown to be able to automatically perform measurements and even outperform experts in terms of accuracy. Conclusions: Recent advancements in imaging modalities and image processing techniques make complex 3D evaluation of chest deformation possible. Before introduction into daily clinical practice, however, there is a need for studies correlating image-based chest deformation parameters to patient-reported outcomes, and for technological advancements to make the workflow cost-effective.

Three-dimensional correction of scoliosis by a double spring reduction system as a dynamic internal brace: a pre-clinical study in Göttingen minipigs

BACKGROUND CONTEXT

Adolescent idiopathic scoliosis (AIS) is a major skeletal deformity that is characterized by a combination of apical rotation, lateral bending and apical lordosis. To provide full 3D correction, all these deformations should be addressed. We developed the Double Spring Reduction (DSR) system, a (growth-friendly) concept that continuously corrects the deformity through two different elements: A posterior convex Torsional Spring Implant (TSI) that provides a derotational torque at the apex, and a concave Spring Distraction System (SDS), which provides posterior, concave distraction to restore thoracic kyphosis.

PURPOSE

To determine whether the DSR components are able to correct an induced idiopathic-like scoliosis and to compare correction realized by the TSI alone to correction enforced by the complete DSR implant.

STUDY DESIGN/SETTING

Preclinical randomized animal cohort study.

PATIENT SAMPLE

Twelve growing Göttingen minipigs.

OUTCOME MEASURES

Coronal Cobb angle, T10-L3 lordosis/kyphosis, apical axial rotation, relative anterior lengthening.

METHODS

All mini-pigs received the TSI with a contralateral tether to induce an idiopathic-like scoliosis with apical rotation (mean Cobb: 20.4°; mean axial apical rotation: 13.1°, mean lordosis: 4.9°). After induction, the animals were divided into two groups: One group (N=6) was corrected by TSI only (TSI only-group), another group (N=6) was corrected by a combination of TSI and SDS (DSR-group). 3D spinal morphology on CT was compared between groups over time. After 2 months of correction, animals were euthanized.

RESULTS

Both intervention groups showed excellent apical derotation (TSI only-group: 15.0° to 5.4°; DSR-group: 11.2° to 3.5°). The TSI only-group showed coronal Cobb improvement from 22.5° to 6.0°, while the DSR-group overcorrected the 18.3° Cobb to -9.2°. Lordosis was converted to kyphosis in both groups (TSI only-group: -4.6° to 4.3°; DSR-group: -5.2° to 25.0°) which was significantly larger in the DSR-group (p<.001).

CONCLUSIONS

The TSI alone realized strong apical derotation and moderate correction in the coronal and sagittal plane. The addition of distraction on the posterior concavity resulted in more coronal correction and reversal of induced lordosis into physiological kyphosis.

CLINICAL SIGNIFICANCE

This study shows that dynamic spring forces could be a viable method to guide the spine towards healthy alignment, without fusing it or inhibiting its growth.

Convex-concave and anterior-posterior spinal length discrepancies in adolescent idiopathic scoliosis with major right thoracic curves versus matched controls

PURPOSE

The apical deformation in adolescent idiopathic scoliosis (AIS) is a combination of rotation, coronal deviation and passive anterior lengthening of the spine. In AIS surgery, posterior-concave lengthening or anterior-convex shortening can be part of the corrective maneuver, as determined by the individual surgeon's technique. The magnitude of convex-concave and anterior-posterior length discrepancies, and how this needs to be modified to restore optimal spinal harmony, remains unknown.

METHODS

CT-scans of 80 pre-operative AIS patients with right convex primary thoracic curves were sex- and age-matched to 80 healthy controls. The spinal length parameters of the main thoracic curves were compared to corresponding levels in controls. Vertebral body endplates and posterior elements were semi-automatically segmented to determine the length of the concave and convex side of the anterior column and along the posterior pedicle screw entry points while taking the 3D-orientation of each individual vertebra into account.

RESULTS

The main thoracic curves showed anterior lengthening with a mean anterior-posterior length discrepancy of + 3 ± 6%, compared to a kyphosis of - 6 ± 3% in controls (p < 0.01). In AIS, the convex side was 20 ± 7% longer than concave (0 ± 1% in controls; p < 0.01). The anterior and posterior concavity were 7 and 22 mm shorter, respectively, while the anterior and posterior convexity were 21 and 8 mm longer compared to the controls.

CONCLUSIONS

In thoracic AIS, the concave shortening is more excessive than the convex lengthening. To restore spinal harmony, the posterior concavity should be elongated while allowing for some shortening of the posterior convexity.

The risk of delayed spinal cord injury in pediatric spinal deformity surgery

Delayed spinal cord injury (SCI) hours or days after surgery, with uneventful monitoring and initial normal postoperative neurological examination, is a rare complication. Based on anecdotal evidence, the risk of delayed spinal cord injury might be higher than previously assumed. Therefore the aim of this study was to determine the risk of delayed SCI after pediatric spinal deformity surgery between 2013-2019 in the Netherlands. The total number of pediatric spinal deformity surgeries performed for scoliosis or kyphosis between 2013-2019 was obtained from the Dutch National Registration of Hospital Care. All eleven Dutch hospitals that perform pediatric spinal deformity surgery were contacted for occurrence of delayed SCI. From the identified patients with delayed SCI, the following data were collected: patient characteristics, details about the SCI, the surgical procedure, management and degree of improvement.2884 pediatric deformity surgeries were identified between 2013-2019. Seven patients (0.24%) with delayed SCI were reported: 3 idiopathic, 2 neuromuscular (including 1 kypho-scoliosis) and 2 syndromic scoliosis. The risk of delayed SCI after pediatric deformity surgery was 1:595 in idiopathic scoliosis, 1:214 in syndromic scoliosis, 1:201 in neuromuscular scoliosis. All seven patients had a documented normal neurological examination in the first postoperative period; neurological deficits were first diagnosed at a median 16h (range 2.5-40) after surgery. The risk of delayed SCI after pediatric deformity surgery is higher than previously reported, especially in patients with non-idiopathic scoliosis. Regular postoperative testing for late neurologic deficit should be performed for timely diagnosis and management of this devastating complication.

CT analysis of the posterior anatomical landmarks of the scoliotic spine

AIM

To use computed tomography (CT) to assess the validity and reliability of the posterior landmarks, spinous processes (SP), transverse processes (TP), and centre of lamina (COL), as compared to the Cobb angle to assess the curve severity and progression of adolescent idiopathic scoliosis (AIS).

MATERIALS AND METHODS

A consecutive series of CT examinations of severe AIS patients were included retrospectively. SP, TP, and COL angles were measured for all curves and compared to the Cobb angle.

RESULTS

One hundred and five patients were included. The mean Cobb versus SP, TP, and COL angles were, 54° versus 37°, 49°, and 51° in the thoracic curves and 34° versus 26°, 31°, and 34° in the (thoraco)lumbar curves. Intraclass correlation coefficient values for intra-rater measurements of the SP, TP, and COL angles were 0.93, 0.97, and 0.95 and 0.70, 0.90, and 0.88 for inter-rater measurements. The correlations between the Cobb angle and SP, TP, and COL angles in thoracic and (thoraco)lumbar curves were 0.79 and 0.66, 0.87 and 0.84, and 0.80 and 0.70.

CONCLUSIONS

The posterior spinal landmarks can be used for assessment of scoliosis severity in AIS; however, they show a systematic underestimation, but a strong correlation with the coronal Cobb angle. TP and COL angles had the highest validity.

Current Evidence for Spinopelvic Characteristics Influencing Total Hip Arthroplasty Dislocation Risk

BACKGROUND

Decreased pelvic mobility and pelvic retroversion may result from spinal degeneration and lead to changes in the orientation of the acetabular implant after total hip arthroplasty (THA). While multiple patient and surgery-related factors contribute to THA dislocations, there is increasing evidence that sagittal spinopelvic dynamics are relevant for THA stability. The aim of this systematic review was to assess the relationship between previously described sagittal spinopelvic characteristics and implant dislocations after primary THA.

METHODS

A comprehensive literature search in the PubMed and Embase databases was conducted for studies reporting on spinopelvic morphology, alignment, pathology, or surgery and THA dislocations. Risk of bias was assessed using the MINORS criteria. Because of high heterogeneity in study methodology, a synthesis of best evidence was performed. Odds ratios (ORs), relative risks (RRs), and effect sizes (g) were calculated.

RESULTS

Fifteen studies (1,007,900 THAs) with quality scores of 15 to 23 out of 24 were included. Nine different spinopelvic alignment parameters (8 studies, g = 0.14 to 2.02), spinal pathology (2 studies, OR = 1.9 to 29.2), and previous spinal fusion surgery (8 studies, OR = 1.59 to 23.7, RR = 3.0) were found to be related to THA dislocation. Conflicting results were found for another sagittal pelvic morphology parameter, pelvic incidence.

CONCLUSIONS

Several sagittal spinopelvic patient characteristics were found to be related to THA dislocation, and the associated risks were greater than for other patient and surgery-related factors. Future research is needed to determine which of those characteristics and parameters should be taken into account in patients undergoing primary THA.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Disc and Vertebral Body Morphology From Birth to Adulthood

STUDY DESIGN

Cross-sectional.

OBJECTIVE

The aim of this study was to describe the morphology of intervertebral discs and vertebral bodies during growth in asymptomatic children and adolescents.

SUMMARY OF BACKGROUND DATA

Earlier studies demonstrated that spinal growth occurs predominantly in vertebral bodies. This axiom introduced a vertebral-body-focus for unravelling etiological questions and achieve growth-modulation in young spinal deformity patients. Recent studies show the importance of the intervertebral discs in the early phases and possible etiology of pediatric spinal deformities. There is presently a paucity of 3D morphometric data of spinal elements during growth.

METHODS

A database of 298 patients aged 0 to 21 that have received a computed tomography scan for indications not related to the spine was analyzed. Custom made software was used to semi-automatically measure intervertebral disc and vertebral body morphology, corrected for orientation in all 3 planes.

RESULTS

Vertebral body height increased from birth up to adulthood, from 4-to-14 mm in the cervical, 6 to 20 mm in the thoracic, and 9 to 28 mm in the lumbar spine. This increase was 0.70 mm/year in males, more pronounced than females with 0.62 mm/year (P = 0.001). Lumbar discs increased throughout growth from 4.4 to 9.0 mm, whereas thoracic discs only increased from 3.5 to 4.9 mm at age 4 and remained stable afterwards, similarly for cervical discs. The disc transverse surface area increased greatly and consistently throughout growth. Disc slenderness was stable in the lumbar spine during growth, but decreased in the thoracic and cervical spine. Overall, discs were more slender in females, especially around early adolescence.

CONCLUSION

The spine grows predominantly in the vertebral bodies. Thoracic discs increase in height only during the first years, whereas the transverse surface area continues to increase throughout growth, thus discs slenderness decreases. Relatively, female discs remained slenderer around growth-spurt. These measurements may assist future studies on the role of disc morphology in the etiology and treatment of spinal deformity.Level of Evidence: 4.

Calculation of the 3-D femoral component's orientation in total hip arthroplasty using a trigonometric algorithm

Femoral component orientation plays a key role in implant stability and therefore the success rate of total hip arthroplasty. To date, this topic has been studied using various definitions and a variety of imaging modalities and protocols. The aim of this study is a proof of concept that a new algorithm can be used to describe the femoral component’s 3D orientation on the three orthogonal anatomical planes and relative to its mechanical axis using input from two orthogonal planes. CT scans of 18 patients with a total of 22 hip arthroplasties were collected. From these, orthogonal coronal and sagittal projections of the complete femur were acquired in the scanning position (MIPs) and relative to the femoral mechanical axis (corrected MIPs). On these images, the orientation of the neck of the femoral component in space and relative to the femoral axis, respectively, was measured by coronal inclination (CI_F), sagittal inclination (SI_F) and transverse version (TV_F). With the algorithm, TV_F was also calculated based on CI_F and SI_F. Differences between measured and calculated TV_F and intra- and inter-observer reliability were evaluated using intra-class correlation coefficients (ICC). The error of non-orthogonal imaging (85° angle between the sagittal and coronal reconstructions) was tested on a third series of MIPs. The ICC between the calculated TV_F and manually measured TV_F, in space and relative to the femoral axis, was 0.98 for both with median absolute differences of 1.3 and 1.5°. For non-orthogonal images this was 0.70 with a median absolute difference of 5°. ICCs for intra-observer and inter-observer reliability for the calculated TV_F values were 0.98 and 0.88, respectively. With this algorithm the transverse orientation of the neck of the femoral component can be assessed in space and relative to the mechanical femoral axis by combining its sagittal and coronal orientation. As long as the imaging visualizes two orthogonal planes, the orientation of an implant can be assessed in 3-D, regardless of the imaging modality.

Comment on Grivas et al. Morphology, Development and Deformation of the Spine in Mild and Moderate Scoliosis: Are Changes in the Spine Primary or Secondary? J. Clin. Med. 2021, 10, 5901

With great interest, we have read the article entitled "Morphology, Development and Deformation of the Spine in Mild and Moderate Scoliosis: Are Changes in the Spine Pri-mary or Secondary [...].

Reply to Weiss, H.-R. Comment on "Costa et al. The Effectiveness of Different Concepts of Bracing in Adolescent Idiopathic Scoliosis (AIS): A Systematic Review and Meta-Analysis. J. Clin. Med. 2021, 10, 2145"

We would like to thank you for the opportunity to reply to the comments in regard of the letter by Dr. Weiss [...].

The role of the femoral component orientation on dislocations in THA: a systematic review

INTRODUCTION

Dislocation remains a major complication in total hip arthroplasty (THA), in which femoral component orientation is considered a key parameter. New imaging modalities and definitions on femoral component orientation have been introduced, describing orientation in different planes. This study aims to systematically review the relevance of the different orientation parameters on implant stability.

METHODS

A systematic review was performed according to the PRISMA guidelines to identify articles in the PubMed and EMBASE databases that study the relation between any femoral component orientation parameters and implant stability in primary THA.

RESULTS

After screening for inclusion and exclusion criteria and quality assessment, nine articles were included. Definitions to describe the femoral component orientation and methodologies to assess its relevance for implant stability differed greatly, with lack of consensus. Seven retrospective case-control studies reported on the relevance of the transversal plane orientation: Low femoral- or low combined femoral and acetabular anteversion was statistical significantly related with more posterior dislocations, and high femoral- or combined femoral and acetabular anteversion with anterior dislocations in two studies. There were insufficient data on sagittal and coronal component orientation in relation to implant stability.

CONCLUSION

Because of incomparable definitions, limited quality and heterogeneity in methodology of the included studies, there is only weak evidence that the degree of transverse component version is related with implant stability in primary THA. Recommendations about the optimal orientation of the femoral component in all three anatomical planes cannot be provided. Future studies should uniformly define the three-dimensional orientation of the femoral component and systematically describe implant stability.

Thoracic Morphology and Bronchial Narrowing Are Related to Pulmonary Function in Adolescent Idiopathic Scoliosis

BACKGROUND

In adolescent idiopathic scoliosis (AIS), lung function impairment is not necessarily related to the coronal spinal deformity. Recently, right-sided bronchial narrowing has been reported in thoracic AIS. The aim of this study was to describe the relation of chest and spinal deformity parameters, bronchial narrowing, and lung volumes with pulmonary function in preoperative AIS.

METHODS

Spinal radiographs, low-dose computed tomographic (CT) scans of the spine including the chest, and pulmonary function tests were retrospectively collected for 85 preoperative patients with thoracic AIS in 2 centers and were compared with 14 matched controls. Three-dimensional lung and airway reconstructions were acquired. Correlation analysis was performed in which radiographic spinal parameters, CT-based thoracic deformity parameters (rib-hump index [RHi], spinal penetration index, endothoracic hump ratio, hemithoracic-width ratio), lung volume asymmetry, and bronchial cross-sectional area were compared with percent-of-predicted spirometry results.

RESULTS

Forty-one patients (48%) had a percent-of-predicted forced expiratory volume in 1 second (FEV1%) or percent-of-predicted forced vital capacity (FVC%) of <65%, and 17 patients (20%) had obstructive lung disease. All thoracic deformity parameters correlated significantly with FEV1% and FVC%; RHi was found to be the best correlate (rs = -0.52 for FEV1% and -0.54 for FVC%). Patients with AIS with impaired pulmonary function had hypokyphosis, a larger rib hump, increased spinal and thoracic rotation, a narrower right hemithorax, and increased intrusion of the spine into the chest. Spinal intrusion correlated with right-sided bronchial narrowing, relative right lung volume loss, and decreased FEV1% and FVC%. Multivariate regression including spinal and thoracic deformity parameters, lung volume asymmetry, and airway parameters could explain 57% of the variance in FEV1% and 54% of the variance in FVC%.

CONCLUSIONS

Chest intrusion by the endothoracic hump is related to right-sided bronchial narrowing and lung function loss in preoperative AIS. The findings support the theory that ventilatory dysfunction in thoracic AIS is not only restrictive but frequently has an obstructive component, especially in patients with hypokyphosis. RHi is the most predictive chest parameter for lung function loss.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

The role of sagittal pelvic morphology in the development of adult degenerative scoliosis

PURPOSE

Pelvic morphology dictates the alignment and biomechanics of the spine. Recent observations in different types of adolescent idiopathic scoliosis indicate that individual pelvic morphology is related to the spinal levels in which scoliosis develops: primary lumbar adolescent scoliosis is associated with a higher pelvic incidence (PI) than thoracic scoliosis and non-scoliotic controls. We hypothesize that adult degenerative scoliosis (ADS) of the lumbar spine follows the same mechanical principles and is associated with a high PI.

METHODS

This study used an existing CT-scan database, 101 ADS patients were sex and age matched to 101 controls. The PI was measured by two observers with multi-planar reconstruction, perpendicular to the hip-axis according to a previously validated technique.

RESULTS

The PI was 54.1° ± 10.8° in ADS patients and 47.7° ± 10.8° in non-scoliotic controls (p < 0.001). The median ADS curve apex was the disc L2-3 and median curve length was 4 vertebral levels. The mean supine Cobb angle was 21° ± 8° (ranged 10°-47°). There was no significant correlation between PI and the apex level (p = 0.883), the curve length (p = 0.418) or the Cobb angle (p = 0.518).

CONCLUSIONS

ADS normally develops de novo in the lumbar spine of patients with a higher PI than controls, similar to primary lumbar adolescent idiopathic scoliosis. This suggests a shared mechanical basis of both deformities. Pelvic morphology dictates spinal sagittal alignment, which determines the segments of the spine that are prone to develop scoliosis.

Health-related quality of life and sagittal balance at two to 25 years after posterior transfixation for high-grade dysplastic spondylolisthesis

Aims

High-grade dysplastic spondylolisthesis is a disabling disorder for which many different operative techniques have been described. The aim of this study is to evaluate Scoliosis Research Society 22-item (SRS-22r) scores, global balance, and regional spino-pelvic alignment from two to 25 years after surgery for high-grade dysplastic spondylolisthesis using an all-posterior partial reduction, transfixation technique.

Methods

SRS-22r and full-spine lateral radiographs were collected for the 28 young patients (age 13.4 years (SD 2.6) who underwent surgery for high-grade dysplastic spondylolisthesis in our centre (Scottish National Spinal Deformity Service) between 1995 and 2018. The mean follow-up was nine years (2 to 25), and one patient was lost to follow-up. The standard surgical technique was an all-posterior, partial reduction, and S1 to L5 transfixation screw technique without direct decompression. Parameters for segmental (slip percentage, Dubousset’s lumbosacral angle) and regional alignment (pelvic tilt, sacral slope, L5 incidence, lumbar lordosis, and thoracic kyphosis) and global balance (T1 spino-pelvic inclination) were measured. SRS-22r scores were compared between patients with a balanced and unbalanced pelvis at final follow-up.

Results

SRS-22r domain and total scores improved significantly from preoperative to final follow-up, except for the mental health domain that remained the same. Slip percentage improved from 75% (SD 15) to 48% (SD 19) and lumbosacral angle from 70° (SD 11) to 101° (SD 11). Preoperatively, 35% had global imbalance, and at follow-up all were balanced. Preoperatively, 63% had an unbalanced pelvis, and at final follow-up this was 32%. SRS-22r scores were not different in patients with a balanced or unbalanced pelvis. However, postoperative pelvic imbalance as measured by L5 incidence was associated with lower SRS-22r self-image and total scores (p = 0.029).

Conclusion

In young patients with HGDS, partial reduction and transfixation improves local lumbosacral alignment, restores pelvic, and global balance and provides satisfactory long-term clinical outcomes. Higher SRS-22r self-image and total scores were observed in the patients that had a balanced pelvis (L5I < 60°) at two to 25 years follow-up.

Cite this article: Bone Jt Open 2021;2(3):163–173.

The Effect of Postural Pelvic Dynamics on the Three-dimensional Orientation of the Acetabular Cup in THA Is Patient Specific

BACKGROUND

Sagittal pelvic dynamics mainly consist of the pelvis rotating anteriorly or posteriorly while the hips flexes, and this affects the femoroacetabular or THA configuration. Thus far, it is unknown how the acetabular cup of the THA in the individual patient reorients with changing sagittal pelvic dynamics.

QUESTIONS/PURPOSES

The aim of this study was to validate a method that establishes the three-dimensional (3-D) acetabular cup orientation with changing sagittal pelvic dynamics and describe these changes during functional pelvic dynamics.

METHODS

A novel trigonometric mathematical model, which was incorporated into an easy-to-use tool, was tested. The model connected sagittal tilt, transverse version, and coronal inclination of the acetabular cup during sagittal pelvic tilt. Furthermore, the effect of sagittal pelvic tilt on the 3-D reorientation of acetabular cups was simulated for cups with different initial positions. Twelve pelvic CT images of patients who underwent THA were taken and rotated around the hip axis to different degrees of anterior and posterior sagittal pelvic tilt (± 30°) to simulate functional pelvic tilt in various body positions. For each simulated pelvic tilt, the transverse version and coronal inclination of the cup were manually measured and compared with those measured in a mathematical model in which the 3-D cup positions were calculated. Next, this model was applied to different acetabular cup positions to simulate the effect of sagittal pelvic dynamics on the 3-D orientation of the acetabular cup in the coronal and transverse plane. After pelvic tilt was applied, the intraclass correlation coefficients of 108 measured and calculated coronal and transverse cup orientation angles were 0.963 and 0.990, respectively, validating the clinical use of the mathematical model.

RESULTS

The changes in 3-D acetabular cup orientation by functional pelvic tilt differed substantially between cups with different initial positions; the change in transverse version was much more pronounced in cups with low coronal inclination (from 50° to -29°) during functional pelvic tilt than in cups with a normal coronal inclination (from 39° to -11°) or high coronal inclination (from 31° to 2°). However, changes in coronal inclination were more pronounced in acetabular cups with high transverse version.

CONCLUSION

Using a simple algorithm to determine the dynamic 3-D reorientation of the acetabular cup during functional sagittal pelvic tilt, we demonstrated that the 3-D effect of functional pelvic tilt is specific to the initial acetabular cup orientation and thus per THA patient.

CLINICAL RELEVANCE

Future studies concerning THA (in)stability should not only include the initial acetabular cup orientation, but also they need to incorporate the effect of sagittal pelvic dynamics on the individual 3-D acetabular cup orientation. Clinicians can also use the developed tool, www.3d-hip.com, to calculate the acetabular cup's orientation in other instances, such as for patients with spinopelvic imbalance.

The heritability of coronal and sagittal phenotype in idiopathic scoliosis: a report of 12 monozygotic twin pairs

PURPOSE

One of the pathways through which genetics may act in the causation of idiopathic scoliosis is inheritance of a specific sagittal profile that predisposes for its development. In this study, coronal and sagittal parameters were compared in an international collection of monozygotic twins with idiopathic scoliosis.

METHODS

Twelve monozygotic twin pairs who underwent biplanar radiography for idiopathic scoliosis were systematically identified in existing scoliosis databases in The Netherlands, Sweden, and Denmark. On the first available radiographs, the coronal and sagittal curve parameters (Roussouly and Abelin types, thoracic kyphosis, lumbar lordosis and length of the posteriorly inclined segment) were determined.

RESULTS

In all 12 monozygotic twin pairs, both twins were affected by AIS. Four (33%) twin pairs had similar coronal and sagittal spinal phenotype, whereas two (17%) had different coronal phenotype and similar sagittal profiles, and six (50%) pairs had different coronal as well as sagittal phenotype.

CONCLUSIONS

Analysis of biplanar curve characteristics in monozygotic twins showed that all twin pairs were affected by idiopathic scoliosis. However, only 33% of the pairs had similar coronal and sagittal spinal phenotypes. Based on this limited dataset, the hypothesis can be formulated that besides genetic pre-disposition, the individual (inherited) sagittal profile plays a role in the development of different coronal curve type.

Unravelling the knee-hip-spine trilemma from the CHECK study

AIMS

The aetiologies of common degenerative spine, hip, and knee pathologies are still not completely understood. Mechanical theories have suggested that those diseases are related to sagittal pelvic morphology and spinopelvic-femoral dynamics. The link between the most widely used parameter for sagittal pelvic morphology, pelvic incidence (PI), and the onset of degenerative lumbar, hip, and knee pathologies has not been studied in a large-scale setting.

METHODS

A total of 421 patients from the Cohort Hip and Cohort Knee (CHECK) database, a population-based observational cohort, with hip and knee complaints < 6 months, aged between 45 and 65 years old, and with lateral lumbar, hip, and knee radiographs available, were included. Sagittal spinopelvic parameters and pathologies (spondylolisthesis and degenerative disc disease (DDD)) were measured at eight-year follow-up and characteristics of hip and knee osteoarthritis (OA) at baseline and eight-year follow-up. Epidemiology of the degenerative disorders and clinical outcome scores (hip and knee pain and Western Ontario and McMaster Universities Osteoarthritis Index) were compared between low PI (< 50°), normal PI (50° to 60°), and high PI (> 60°) using generalized estimating equations.

RESULTS

Demographic details were not different between the different PI groups. L4 to L5 and L5 to S1 spondylolisthesis were more frequently present in subjects with high PI compared to low PI (L4 to L5, OR 3.717; p = 0.024 vs L5 to S1 OR 7.751; p = 0.001). L5 to S1 DDD occurred more in patients with low PI compared to high PI (OR 1.889; p = 0.010), whereas there were no differences in L4 to L5 DDD among individuals with a different PI. The incidence of hip OA was higher in participants with low PI compared to normal (OR 1.262; p = 0.414) or high PI (OR 1.337; p = 0.274), but not statistically different. The incidence of knee OA was higher in individuals with a high PI compared to low PI (OR 1.620; p = 0.034).

CONCLUSION

High PI is a risk factor for development of spondylolisthesis and knee OA. Low pelvic incidence is related to DDD, and may be linked to OA of the hip. Level of Evidence: 1b Cite this article: Bone Joint J 2020;102-B(9):1261-1267.

A computed tomography-based spatial reference for pedicle screw placement in adolescent idiopathic scoliosis

STUDY DESIGN

Cross-sectional.

OBJECTIVES

To determine semiautomatically the 3D position of the pedicle axis in operative adolescent idiopathic scoliosis (AIS) patients relative to the operating table and the lamina, as orientation for pedicle screw placement for better understanding and reference of spine surgeons. Pedicle morphology is well described as the angle between the convex and concave pedicle. However, the pedicle angle as relative to the neutral anterior-posterior axis or to an easy-to-use intravertebral landmark, remained unknown.

METHODS

The pedicles of the apex and two adjacent vertebrae cranial and caudal to the apex of 86 right-sided primary thoracic AIS curves were evaluated using semiautomatic 3D software on high-resolution CT scans, in the same prone position as during surgery. Pedicle vectors were obtained and calculated as transverse and sagittal angles, as relative to the neutral axis (corresponding with an axis perpendicular to the operating table) and to an axis perpendicular to the lamina.

RESULTS

At the apex, the mean convex and concave transverse pedicle angles were 14.3º (95% confidence interval [95% CI]: 12.0-16.6) and 30.4º (95% CI: 28.1-32.8) to the right. The angles decreased toward the adjacent levels cranial and caudal to the apex (p < 0.001) and linearly increased with a higher Cobb angle (r ≥ 0.472; p < 0.001). The mean transverse pedicle-lamina angles, sagittal pedicle angles and the sagittal pedicle-lamina angles differed along the curve as well (p < 0.001).

CONCLUSIONS

Pedicle angulation differs between convex and concave and depends on the position of the vertebra relative to the apex, as well as the curve severity. The transverse and sagittal pedicle angles, as relative to the operating table and laminae, could provide useful reference for better understanding of the distorted 3D morphology, and the angles, as given in this study, could serve as an approximate guideline for the expected direction of the pedicle screw.

LEVEL OF EVIDENCE

Level IV.

Sagittal spinal parameters after en bloc resection of mobile spine tumors

BACKGROUND CONTEXT

En bloc resection and reconstruction (EBR) in patients with spinal malignancy aims to achieve local disease control. This is an invasive procedure with significant alterations of the physiological anatomy and subsequently, the spino-pelvic alignment. Sagittal spinal parameters are useful measurements to objectively identify disproportionate alignment on a radiograph. In the field of spinal deformities, there is increasing evidence for a relationship between sagittal alignment and patient reported outcomes.

PURPOSE

To determine sagittal spino-pelvic alignment after EBR in patients with spinal malignancies and the effect of these parameters on surgical and patient reported outcomes.

STUDY DESIGN

A retrospective case series.

METHODS

We included 35 patients who underwent EBR for spinal malignancies between 2000 and 2018. Radiographic measurements were performed using semi-automatic software; the parameters included were pelvic incidence (PI), sacral slope, pelvic tilt (PT), global tilt and lumbar lordosis. We calculated PI-based Global Alignment and Proportion (GAP) scores and prospective patient reported outcome scores Patient-Reported Outcome Measurement Information System-Physical Function (PROMIS-PF) were used.

RESULTS

Twenty-one (60%) patients filled out the PROMIS-PF score at a median of 16 months (Interquartile Range (IQR) 4-108) after surgery with a median score of 39 (IQR 32-42), the median GAP score was 7 (IQR 5-9). Bivariate analysis showed no statistically significant relationship between GAP score and instrumentation failure or need for revision surgery. Multivariable analysis of GAP score and PROMIS-PF score corrected for local disease recurrence showed a statistically significant correlation coefficient of -1.721 (p=.026; 95%CI=-3.216, -0.226).

CONCLUSION

In this cohort, all patients had a moderate or severe disproportioned spinal alignment after EBR and reconstruction surgery. The degree of sagittal spino-pelvic misalignment after EBR for spinal malignancies seems to be associated with patient reported health status in terms of PROMIS-PF scores. Further research with a larger patient cohort and standardized imaging and follow-up protocols is necessary in order to accurately use sagittal alignment as a predictive value for instrumentation failure and revision surgery.

CT-based study of vertebral and intravertebral rotation in right thoracic adolescent idiopathic scoliosis

Purpose

To define the longitudinal rotation axis around which individual vertebrae rotate, and to establish the various extra- and intravertebral rotation patterns in thoracic adolescent idiopathic scoliosis (AIS) patients, for better understanding of the 3D development of the rotational deformity.

Methods

Seventy high-resolution CT scans from an existing database of thoracic AIS patients (Cobb angle: 46°–109°) were included to determine the vertebral axial rotation, rotation radius, intravertebral axial rotation, and local mechanical torsion for each spinal level, using previously validated image processing techniques.

Results

For all levels, the longitudinal rotation axis, from which the vertebrae rotate away from the midline, was localized posterior to the spine. The axis became closer to the spine at the apex: apex, r = 11.5 ± 5.1 cm versus two levels above (radius = 15.8 ± 8.5 cm; p < 0.001) and beneath (radius = 14.2 ± 8.2 cm; p < 0.001). The vertebral axial rotation, intravertebral axial rotation, and local mechanical torsion of the vertebral bodies were largest at the apex (21.9° ± 7.4°, 8.7° ± 13.5° and 3.0° ± 2.5°) and decreased toward the neutral, junctional zones (p < 0.001).

Conclusion

In AIS, the vertebrae rotate away around an axis that is localized posterior to the spine. The distance between this axis and the spine is minimal at the apex and increases gradually to the neutral zones. The vertebral axial rotation is accompanied by smaller amounts of intravertebral rotation and local mechanical torsion, which increases toward the apical region. The altered morphology and alignment are important for a better understanding of the 3D pathoanatomical development of AIS and better therapeutic planning for bracing and surgical intervention.

Graphic abstract

These slides can be retrieved under Electronic Supplementary Material.

Non-equivalent Results from Different Anteversion Measurements Methods for the Evaluation of the Acetabular Cup Orientation in Total Hip Arthroplasty

Objective

To determine the comparability among 10 radiographic anteversion methods for acetabular cup orientation in total hip arthroplasty (THA) found in the literature and the “gold” standard of assessing the anteversion with CT.

Methods

This is a retrospective study that blindly compares 10 different conventional radiographic anteversion measurements with the “gold” standard, the measurement of anteversion on the transverse plane of the 3‐D images made with CT. The patient archiving and communications system (PACS) was systematically searched for subjects that had undergone a CT angiogram of the abdomen and lower extremities, including the pelvis, had at least one THA in situ and had undergone anterior‐posterior (AP) and cross‐lateral pelvic radiography between January 2013 and August 2016 in the Diakonessenhuis Hospital Utrecht/Zeist, a non‐academic institution. CT scans of patients (n = 16) were systematically collected. Three observers independently measured cup anteversion from radiographs, using a total of 10 different methods, and measured the “gold” standard on CT images. The outcomes of the 10 radiographic anteversion were compared in terms of linear correlation with the “gold” standard on CT images.

Results

The correlations of the radiographic measured anteversions with the “gold” standard measured on CT images were 0.528 for the method of Liaw, 0.556 for Wan, 0.562 for the cross‐lateral method, 0.586 for Hassan, 0.594 for Dorr, 0.602 for Lewinnek, 0.624 for Widmer, 0.671 for the lateral CT, 0.747 for Ackland, and 0.771 for the method of Riten Pradham.

Conclusion

Anteversion measurement methods represent different projectional angles of the acetabular cup in different planes around different axes. Therefore, they differ from the “gold” standard and are not interchangeable, as is shown by this study. We consider the anatomical anteversion in the transverse plane rotating around the longitudinal axis as the “gold” standard and recommend avoiding using the term anteversion for other projectional angles in different planes.

Scoliosis in association with the 22q11.2 deletion syndrome: an observational study

OBJECTIVE

The 22q11.2 deletion syndrome (22q11.2DS) is the most common microdeletion syndrome in humans. It is characterised by wide phenotypic variability, including congenital heart disease (CHD), immunodeficiency and scoliosis. However, little is known regarding the prevalence and characteristics of scoliosis in patients with 22q11.2DS. The objective of this study is to assess the prevalence of scoliosis, its characteristics and the association with CHD in patients with 22q11.2DS.

DESIGN

This prevalence study is based on physical examination and questionnaires of the world's largest 22q11.2DS longitudinal collected database (n=1393, Children's Hospital of Philadelphia) and was augmented with the scoliosis prevalence based on radiography in a smaller cohort (cross-sectional, University Medical Center Utrecht).

PATIENTS

Patients with a laboratory-confirmed 22q11.2 deletion who visited the specialised outpatient clinics were considered for inclusion.

MAIN OUTCOME MEASURES

(1) The prevalence of scoliosis, (2) its association with CHD, and (3) the similarity between 22q11.2DS curve patterns and adolescent idiopathic scoliosis (AIS) curve patterns.

RESULTS

Within the Philadelphia cohort, the prevalence of scoliosis in patients older than 16 years (n=317) was 48% (n=152). A similar prevalence (49%) was shown for the younger Utrecht cohort (n=97). The occurrence of scoliosis was not associated with the presence of CHD. Sixty-three per cent of patients with scoliosis had a scoliotic curve pattern that resembled AIS.

CONCLUSIONS

Clinicians should be aware that scoliosis is highly prevalent (48%-49%) in association with 22q11.2DS, irrespective of other clinical features (eg, the presence of CHD). Furthermore, 22q11.2DS may provide insights into the causes of AIS.

Anterior-posterior length discrepancy of the spinal column in adolescent idiopathic scoliosis-a 3D CT study

BACKGROUND CONTEXT

One of the characteristics of reported observations in adolescent idiopathic scoliosis (AIS) is that the thoracic spine is longer anteriorly than posteriorly, more pronounced around the apex than the transitional zones. This reversal of the normal kyphotic anatomy of the thoracic spine is related to questions of etiopathogenesis of AIS. The changes in the anatomy of the anterior column have been described rather in detail; however, the role of the posterior spinal column and the laminae has so far not been elucidated. If the posterior column exhibits a longitudinal growth disturbance, it could act as a tether, leading to a more or less normal anterior column with a deformed and shorter posterior aspect of the spine. So far, it has remained unclear whether this anterior-posterior length discrepancy is the result of relative anterior lengthening or relative posterior shortening, and which tissues (bone, disc, intervertebral soft tissue) are involved.

PURPOSE

The present study aimed to compare the discrepancy of the anterior-posterior length of the spinal column in the "true" midsagittal plane of each vertebra in patients with idiopathic scoliosis versus controls, using three-dimensional computed tomography (CT) scans.

STUDY DESIGN/SETTING

This is a cross-sectional study.

PATIENT SAMPLE

The sample consisted of computed tomography scans of 80 patients with moderate to severe AIS (Cobb angle: 46°-109°) before scoliosis navigation surgery and 30 non-scoliotic age-matched controls.

OUTCOME MEASURES

The height of the osseous and non-osseous structures from anterior to posterior in the "true" midsagittal plane has been determined: the anterior side of the vertebral body and disc, the posterior side of the vertebral body and disc, the lamina and interlaminar space and the spinous process and interspinous space, as well as the height ratios between the anterior column and posterior structures of the primary thoracic and lumbar AIS curves and corresponding levels in non-scoliotic controls.

METHODS

Semiautomatic software was used to reconstruct and measure the parameters in the true midsagittal plane of each vertebra and intervertebral structure that are rotated and tilted in a different way.

RESULTS

In AIS, the anterior height of the thoracic curve was 3.6±2.8% longer than the posterior height, 2.0±6.1% longer than the length along the laminae, and 8.7±7.1% longer than the length along the spinous processes, and this differed significantly from controls (-2.7±2.4%, -7.4±5.2%, and +0.7±7.8%; p<.001). The absolute height of the osseous parts did not differ significantly between AIS and controls in the midsagittal plane. In contrast, the intervertebral structures contributed significantly to the observed length discrepancies. In absolute lengths, the anterior side of the disc of the thoracic curve was higher in AIS (5.4±0.8 mm) than controls (4.8±1.0 mm; p<.001), whereas the interspinous space was smaller in AIS (12.3±1.4 mm vs. 14.0±1.6 mm; p<.001).

CONCLUSIONS

Based on this in vivo analysis, the true three-dimensional anterior-posterior length discrepancy of AIS curves was found to occur through both anterior column lengthening and posterior column shortening, with the facet joints functioning as the fulcrum. The vertebrae contribute partly to the anterior-posterior length discrepancy accompanied by more significant and possibly secondary increased anterior intervertebral discs height.

What Is the Actual 3D Representation of the Rib Vertebra Angle Difference (Mehta Angle)?

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

To establish the relevance of the conventional two-dimensional (2D) rib vertebra angle difference (RVAD) and the relationship with the complex three-dimensional (3D) apical morphology in scoliosis.

SUMMARY OF BACKGROUND DATA

The RVAD, also known as Mehta angle, describes apical rib asymmetry on conventional radiographs and was introduced as a prognostic factor for curve severity in early onset scoliosis, and later applied to other types of scoliosis as well.

METHODS

An existing idiopathic scoliosis database of high-resolution computed tomography scans used in previous work, acquired for spinal navigation, was used. Eighty-eight patients (Cobb angle 46°-109°) were included. Cobb angle and 2D RVAD, as described by Mehta, were measured on the conventional radiographs and coronal digitally reconstructed radiographs (DRR) of the prone computed tomography scans. A previously validated, semiautomatic image processing technique was used to acquire complete 3D spinal reconstructions for the measurement of the 3D RVAD in a reconstructed true coronal plane, axial rotation, and sagittal morphology.

RESULTS

The 2D RVAD on the x-ray was on average 25.3° ± 11.0° and 25.6° ± 12.8° on the DRR (P = 0.990), but in the true 3D coronal view of the apex, hardly any asymmetry remained (3D RVAD: 3.1° ± 12.5°; 2D RVAD on x-ray and DRR vs. 3D RVAD: P < 0.001). 2D apical rib asymmetry in the anatomical coronal plane did not correlate with the same RVAD measurements in the 3D reconstructed coronal plane of the rotated apex (r = 0.155; P = 0.149). A larger 2D RVAD was found to correlate linearly with increased axial rotation (r = 0.542; P < 0.001) and apical lordosis (r = 0.522; P < 0.001).

CONCLUSION

The 2D RVAD represents a projection-based composite radiographic index reflecting the severity of the complex 3D apical morphology including axial rotation and apical lordosis. It indicates a difference in severity of the apical deformation.

LEVEL OF EVIDENCE

4.

Upright, prone, and supine spinal morphology and alignment in adolescent idiopathic scoliosis

BACKGROUND

Patients with adolescent idiopathic scoliosis (AIS) are usually investigated by serial imaging studies during the course of treatment, some imaging involves ionizing radiation, and the radiation doses are cumulative. Few studies have addressed the correlation of spinal deformity captured by these different imaging modalities, for which patient positioning are different. To the best of our knowledge, this is the first study to compare the coronal, axial, and sagittal morphology of the scoliotic spine in three different body positions (upright, prone, and supine) and between three different imaging modalities (X-ray, CT, and MRI).

METHODS

Sixty-two AIS patients scheduled for scoliosis surgery, and having undergone standard pre-operative work-up, were included. This work-up included upright full-spine radiographs, supine bending radiographs, supine MRI, and prone CT as is the routine in one of our institutions. In all three positions, Cobb angles, thoracic kyphosis (TK), lumbar lordosis (LL), and vertebral rotation were determined. The relationship among three positions (upright X-ray, prone CT, and supine MRI) was investigated according to the Bland-Altman test, whereas the correlation was described by the intraclass correlation coefficient (ICC).

RESULTS

Thoracic and lumbar Cobb angles correlated significantly between conventional radiographs (68° ± 15° and 44° ± 17°), prone CT (54° ± 15° and 33° ± 15°), and supine MRI (57° ± 14° and 35° ± 16°; ICC ≥0.96; P < 0.001). The thoracic and lumbar apical vertebral rotation showed a good correlation among three positions (upright, 22° ± 12° and 11° ± 13°; prone, 20° ± 9° and 8° ± 11°; supine, 16° ± 11° and 6° ± 14°; ICC ≥0.82; P < 0.001). The TK and LL correlated well among three different positions (TK 26° ± 11°, 22° ± 12°, and 17° ± 10°; P ≤ 0.004; LL 49° ± 12°, 45° ± 11°, and 44° ± 12°; P < 0.006; ICC 0.87 and 0.85).

CONCLUSIONS

Although there is a generalized underestimation of morphological parameters of the scoliotic deformity in the supine and prone positions as compared to the upright position, a significant correlation of these parameters is still evident among different body positions by different imaging modalities. Findings of this study suggest that severity of scoliotic deformity in AIS patients can be largely represented by different imaging modalities despite the difference in body positioning.

Asymmetry of the Vertebral Body and Pedicles in the True Transverse Plane in Adolescent Idiopathic Scoliosis: A CT-Based Study

STUDY DESIGN

Cross-sectional.

OBJECTIVES

To quantify the asymmetry of the vertebral bodies and pedicles in the true transverse plane in adolescent idiopathic scoliosis (AIS) and to compare this with normal anatomy.

SUMMARY OF BACKGROUND DATA

There is an ongoing debate about the existence and magnitude of the vertebral body and pedicle asymmetry in AIS and whether this is an expression of a primary growth disturbance, or secondary to asymmetrical loading.

METHODS

Vertebral body asymmetry, defined as left-right overlap of the vertebral endplates (ie, 100%: perfect symmetry, 0%: complete asymmetry) was evaluated in the true transverse plane on CT scans of 77 AIS patients and 32 non-scoliotic controls. Additionally, the pedicle width, length, and angle and the length of the ideal screw trajectory were calculated.

RESULTS

Scoliotic vertebrae were on average more asymmetric than controls (thoracic: AIS 96.0% vs. controls 96.4%; p = .005, lumbar: 95.8% vs. 97.2%; p < .001) and more pronounced around the thoracic apex (95.8%) than at the end vertebrae (96.3%; p = .031). In the thoracic apex; the concave pedicle was thinner (4.5 vs. 5.4 mm; p < .001) and longer (20.9 vs. 17.9 mm; p < .001), the length of the ideal screw trajectory was longer (43.0 vs. 37.3 mm; p < .001), and the transverse pedicle angle was greater (12.3° vs. 5.7°; p < .001) than the convex one. The axial rotation showed no clear correlation with the asymmetry.

CONCLUSIONS

Even in non-scoliotic controls is a degree of vertebral body and pedicle asymmetry, but scoliotic vertebrae showed slightly more asymmetry, mostly around the thoracic apex. In contrast to the existing literature, there is no major asymmetry in the true transverse plane in AIS and no uniform relation between the axial rotation and vertebral asymmetry could be observed in these moderate to severe patients, suggesting that asymmetrical vertebral growth does not initiate rotation, but rather follows it as a secondary phenomenon.

LEVEL OF EVIDENCE

Level 4.

Anterior Overgrowth in Primary Curves, Compensatory Curves and Junctional Segments in Adolescent Idiopathic Scoliosis

Introduction

Although much attention has been given to the global three-dimensional aspect of adolescent idiopathic scoliosis (AIS), the accurate three-dimensional morphology of the primary and compensatory curves, as well as the intervening junctional segments, in the scoliotic spine has not been described before.

Methods

A unique series of 77 AIS patients with high-resolution CT scans of the spine, acquired for surgical planning purposes, were included and compared to 22 healthy controls. Non-idiopathic curves were excluded. Endplate segmentation and local longitudinal axis in endplate plane enabled semi-automatic geometric analysis of the complete three-dimensional morphology of the spine, taking inter-vertebral rotation, intra-vertebral torsion and coronal and sagittal tilt into account. Intraclass correlation coefficients for interobserver reliability were 0.98–1.00. Coronal deviation, axial rotation and the exact length discrepancies in the reconstructed sagittal plane, as defined per vertebra and disc, were analyzed for each primary and compensatory curve as well as for the junctional segments in-between.

Results

The anterior-posterior difference of spinal length, based on “true” anterior and posterior points on endplates, was +3.8% for thoracic and +9.4% for (thoraco)lumbar curves, while the junctional segments were almost straight. This differed significantly from control group thoracic kyphosis (-4.1%; P<0.001) and lumbar lordosis (+7.8%; P<0.001). For all primary as well as compensatory curves, we observed linear correlations between the coronal Cobb angle, axial rotation and the anterior-posterior length difference (r≥0.729 for thoracic curves; r≥0.485 for (thoraco)lumbar curves).

Conclusions

Excess anterior length of the spine in AIS has been described as a generalized growth disturbance, causing relative anterior spinal overgrowth. This study is the first to demonstrate that this anterior overgrowth is not a generalized phenomenon. It is confined to the primary as well as the compensatory curves, the junctional zones do not exhibit this growth discrepancy, however, they are straight.

How Does Spinal Release and Ponte Osteotomy Improve Spinal Flexibility? The Law of Diminishing Returns

STUDY DESIGN

Experimental study.

OBJECTIVES

To evaluate the effect of stepwise resection of posterior spinal ligaments, facet joints, and ribs on thoracic spinal flexibility.

SUMMARY OF BACKGROUND DATA

Posterior spinal ligaments, facet joints and ribs are removed to increase spinal flexibility in corrective spinal surgery for deformities such as adolescent idiopathic scoliosis (AIS). Reported clinical results vary and biomechanical substantiation is lacking.

METHODS

Ten fresh-frozen human cadaveric thoracic spinal specimens (T6-T11) were studied. A spinal motion simulator applied a pure moment of ±2.5 Nm in flexion, extension, lateral bending (LB) and axial rotation (AR). Range of motion (ROM) was measured for the intact spine and measured again after stepwise resection of the supra/interspinous ligament (SIL), inferior facet, flaval ligament, superior facet, and rib heads.

RESULTS

SIL resection increased ROM in flexion (10.2%) and AR (3.1%). Successive inferior facetectomy increased ROM in flexion (4.1%), LB (3.8%) and AR (7.7%), and flavectomy in flexion (9.1%) and AR (2.5%). Sequential superior facetectomy only increased ROM in flexion (6.3%). Rib removal provided an additional increase in flexion (6.3%), LB (4.5%) and AR (13.0%). Extension ROM increased by 10.5% after the combined removal of the SIL, inferior facet and flaval ligament.

CONCLUSIONS

Posterior spinal releases in these non-scoliotic spines led to an incremental increase in spinal flexibility, but each sequential step had less effect. As compared to SIL resection with inferior facetectomy, additional superior facetectomy did not improve flexibility in AR and LB and only 6.3% in flexion. The data presented from this in vitro study should be interpreted with care, as no representative cadaveric spine model for AIS was available, However, the results presented here at least question the benefits of performing routine complete facetectomies (i.e. Ponte osteotomies) to increase spinal flexibility in scoliosis surgery.

Reliability and validity of the adapted Dutch version of the revised Scoliosis Research Society 22-item questionnaire

BACKGROUND CONTEXT

As in other fields of medicine, there is an increasing interest among orthopedic surgeons to measure health-related quality of life in adolescent idiopathic scoliosis patients and to evaluate the burden of disease and the effectiveness of different treatment strategies. The development of the revised Scoliosis Research Society 22-item patient questionnaire (SRS-22r) enabled a comprehensive evaluation of health-related quality of life of these patients. Over the years, the SRS-22r gained wide acceptance and has been used in several different countries, languages, and cultures. The SRS-22r has not been translated into Dutch to date.

PURPOSE

To translate the SRS-22r into Dutch and adapt it cross-culturally as outlined by international guidelines and to test its psychometric properties to measure health-related quality of life of adolescent idiopathic scoliosis patients in the Netherlands.

STUDY DESIGN/SETTING

A cross-sectional, multicenter validation study.

PATIENT SAMPLE

A total of 135 adolescent idiopathic scoliosis patients (mean age 15.1 years old) of three major scoliosis centers in the Netherlands were enrolled in this study. Ninety-two (68%) subjects completed the Dutch SRS-22r, Child Health Questionnaire (CHQ)-CF87 (golden standard for adolescents), and Short Form (SF)-36 (golden standard for adults). Two weeks later, 73 (79%) of 92 respondents returned a second SRS-22r. Demographics, curve type, Risser stage, and treatment status were documented.

OUTCOME MEASURES

Floor and ceiling effects, internal consistency, reproducibility, concurrent validity, and discriminative ability of the Dutch version of the SRS-22r questionnaire.

METHODS

For content analysis, SRS-22r domain scores (function, pain, self-image, mental health, and satisfaction with management) were explored and floor and ceiling effects were determined. Cronbach's α was calculated for internal consistency of each domain of the questionnaires and reproducibility was assessed by test-retest reliability analysis. Using Pearson's correlation coefficient, comparison of the domains of the Dutch SRS-22r with the domains of the SF-36 and Child Health Questionnaire-CF87 assessed the concurrent validity. Differences in SRS-22r domain scores between untreated patients with different curve severity determined the discriminative ability of the questionnaire.

RESULTS

The SRS-22r domains as well as the SF-36 and CHQ-CF87 domains demonstrated no floor effects, but the function, pain, and satisfaction with management domains had ceiling effects, indicating the proportion of subjects with the maximum score between 19.6% and 33.0%. Internal consistency was very satisfactory for all SRS-22r domains: Cronbach's α was between 0.718 and 0.852. By omitting question 15, the internal consistency of the function domain increased from 0.746 to 0.827. Test-retest reliability was ≥0.799 for all SRS-22r domains. The function, pain, mental health, and self-image domains correlated under the 0.001 significance level with the corresponding CHQ-CF87 and SF-36 domains. The satisfaction with management domain did not correlate with the other questionnaires. The SRS-22r had the ability to detect differences between groups with different curve severity; patients with a severe scoliotic curvature had significantly lower pain and self-image domain scores than patients with relatively mild scoliosis.

CONCLUSIONS

The Dutch SRS-22r had the properties needed for the measurement of patient perceived health-related quality of life of adolescent idiopathic scoliosis patients in the Netherlands. The Dutch SRS-22r could be used for the longitudinal follow-up of adolescent idiopathic scoliosis patients from adolescence to adulthood and for establishing the effects of conservative or invasive surgical treatment.

How 'idiopathic' is adolescent idiopathic scoliosis? A systematic review on associated abnormalities

Background

Despite more than a century of dedicated research, the etiology and pathogenesis of adolescent idiopathic scoliosis (AIS) remain unclear. By definition, ‘idiopathic’ implies an unknown cause. Nevertheless, many abnormalities concomitant to AIS have been described, often with the suggestion that these abnormalities are related to etio-pathogenesis. Insight in the concomitant abnormalities may assist in improving the understanding of the etiological pathways of AIS. We aimed to systematically review and synthesize available studies on abnormalities concomitant to AIS.

Methods

Original studies comparing untreated AIS patients with healthy adolescents on abnormalities other than the deformity of the spine were retrieved from PubMed and Embase. We followed PRISMA guidelines and to quantify the relationship between each abnormality and AIS we used a best-evidence-syntheses for relating risk-of-bias to consistency of effect sizes.

Results

We identified 88 relevant citations, forty-seven carried high risk-of-bias and twenty studies did not report quantitative data in a sufficient manner. The remaining twenty-one publications failed to report data from before initiation of the deformity and blind assessments. These cross-sectional studies provided data on fourteen abnormalities concomitant to AIS. With our best-evidence-syntheses we were unable to find both strong evidence and a consistent pattern of occurrence for AIS and any of these abnormalities. From moderate risk-of-bias studies a relatively consistent pattern of occurrence for AIS and impaired gait control (4 studies; 155 subjects; Cohen’s d = 1.00) and decreased bone mineral density (2 studies; 954 subjects; Cohen’s d = −0.83) was found. For nine abnormalities a consistent pattern of occurrence with AIS was found, but the evidence for these was weak.

Conclusions

Based on the available literature, strong evidence is lacking for a consistent pattern of occurrence of AIS and any abnormality. The relevance for understanding the multifactorial etiology of AIS is very limited.