Using three-dimensional difference maps to assess changes in scoliotic deformities

Photogrammetry Applied to Neurosurgery: A Literature Review

Photogrammetry refers to the process of creating 3D models and taking measurements through the use of photographs. Photogrammetry has many applications in neurosurgery, such as creating 3D anatomical models and diagnosing and evaluating head shape and posture deformities. This review aims to summarize the uses of the technique in the neurosurgical practice and showcase the systems and software required for its implementation. A literature review was done in the online database PubMed. Papers were searched using the keywords "photogrammetry", "neurosurgery", "neuroanatomy", "craniosynostosis" and "scoliosis". The identified articles were later put through primary (abstracts and titles) and secondary (full text) screening for eligibility for inclusion. In total, 86 articles were included in the review from 315 papers identified. The review showed that the main uses of photogrammetry in the field of neurosurgery are related to the creation of 3D models of complex neuroanatomical structures and surgical approaches, accompanied by the uses for diagnosis and evaluation of patients with structural deformities of the head and trunk, such as craniosynostosis and scoliosis. Additionally, three instances of photogrammetry applied for more specific aims, namely, cervical spine surgery, skull-base surgery, and radiosurgery, were identified. Information was extracted on the software and systems used to execute the method. With the development of the photogrammetric method, it has become possible to create accurate 3D models of physical objects and analyze images with dedicated software. In the neurosurgical setting, this has translated into the creation of anatomical teaching models and surgical 3D models as well as the evaluation of head and spine deformities. Through those applications, the method has the potential to facilitate the education of residents and medical students and the diagnosis of patient pathologies.

The association between Scoliosis Research Society-22 scores and scoliosis severity changes at a clinically relevant threshold

STUDY DESIGN

Cross-sectional correlation study.

OBJECTIVE

To determine the threshold in spinal deformity severity measurements beyond which there is a progressive decline in health-related quality-of-life (HRQOL).

SUMMARY OF BACKGROUND DATA

The associations between HRQOL and scoliosis deformity measures are at best moderate when assessed using linear regressions. This may be because HRQOL is not affected until a severity threshold is reached. Identifying the thresholds in deformity beyond which HRQOL deteriorates could assist in treatment recommendations.

METHODS

The Scoliosis Research Society-22 (SRS-22) questionnaire was completed by 101 females with adolescent idiopathic scoliosis (age, 15.0 +/- 1.8; largest Cobb angle, 36.9 degrees +/- 14.6 degrees). Radiographs and surface topography were used to quantify the severity of the internal (largest Cobb angle) and external deformity (cosmetic score, decompensation, trunk twist), respectively. Segmented linear regression models were estimated to determine the association between SRS-22 domains and spinal deformity measures. This analysis also identifies deformity thresholds beyond which HRQOL is more affected. The percentage of variance explained (R2) by linear and segmented models were compared (alpha = 0.05) to identify the best models.

RESULTS

Cobb angle predicted significantly more variance in all SRS-22 domains except mental health using segmented models (R2: 0.09-0.30) than linear models (R2: 0.02-0.21). Segmented models with a single threshold estimated at a Cobb angle between 43 degrees and 48 degrees predicted between 3% and 11% more variance compared to corresponding linear model using the same variables. Surface topography parameters were not strongly associated with SRS-22 variables with linear and segmented models explaining less than 10% of the variance.

CONCLUSION

Deterioration in SRS-22 scores is mildly associated with increases in the severity of the internal deformity. HRQOL is stable until the curve reaches a maximal Cobb angle threshold at approximately 45 degrees where HRQOL declines linearly with increasing internal deformity. The association between HRQOL and scoliosis severity is low, but is better explained by segmented rather than linear models.

Discriminative and predictive validity of the scoliosis research society-22 questionnaire in management and curve-severity subgroups of adolescents with idiopathic scoliosis

STUDY DESIGN

Prospective cross-sectional measurement study.

OBJECTIVE

To determine the ability of the Scoliosis Research Society (SRS)-22 questionnaire to discriminate among management and scoliosis severity subgroups and to correlate with internal and external measures of curve severity.

SUMMARY OF BACKGROUND DATA

In earlier studies of the SRS-22 discriminative ability, age was not a controlled factor. The ability of the SRS-22 to predict curve severity has not been thoroughly examined.

METHODS

The SRS-22 was completed by 227 females with adolescent idiopathic scoliosis. Using Analysis of covariance analyses controlling for age, the SRS-22 scores were compared among management subgroups (observation, brace, presurgery, and postsurgery) and curve-severity subgroups (in nonoperated subjects: Cobb angles of <30 degrees, 30 degrees -50 degrees, and >50 degrees). A stepwise discriminant analysis was used to identify the SRS-22 domains most discriminative for curve-severity categories. Correlation between SRS-22 scores and radiographic or surface topography measurements was used to determine the predictive ability of the questionnaire.

RESULTS

Pain was better for subjects treated with braces than for those planning surgery. Self-image was better for subjects under observation or postsurgery than for those planning surgery. Satisfaction was better for the brace and postsurgery subgroups than for the observation or presurgery subgroups. Statistically significant mean differences between subgroups were all larger than 0.5, which is within the range of minimal clinically important differences recommended for each of the 5-point SRS-22 domain scoring scales. Pain and mental health were worse for those with Cobb angles of >50 degrees than with Cobb angles of 30 degrees to 50 degrees. Self-image and total scores were worse for those with Cobb angles of >50 degrees than both other subgroups. Using discriminant analysis, self-image was the only SRS-22 domain score selected to classify subjects within curve severity subgroups. The percentage of patients accurately classified was 54% when trying to classify within 3 curve severity subgroups. The percentage of patients accurately classified was 73% when classifying simply as those with curves larger or smaller than 50 degrees .

CONCLUSION

Pain, self-image, and satisfaction scores could discriminate among management subgroups, but function, mental health and total scores could not. The total score and all domain scores except satisfaction discriminated among curve-severity subgroups. Using discriminant analysis, self-image was the only domain retained in a model predicting curve-severity categories.

Validating an imaging and analysis system for assessing torso deformities

We present the results of the numeric and functional validation of an imaging and analysis system used for assessing human torsos for deformities such as scoliosis. The system comprises of image acquisition, image reconstruction, and shape analysis components. The numeric validation procedure consists of assessing the accuracy of reconstruction of the system using inanimate models (a calibration box and a mannequin). The functional validation involves determining the system's response to variations in shape caused by sway and breathing, and evaluating the variability of a clinically relevant index, the Cosmetic Score, from multiple scans of scoliosis and non-scoliosis volunteers. Results show that the reconstruction accuracy of the system is 1.16+/-1.04 mm. This is better than the required accuracy for monitoring scoliosis of 2 mm. The system is robust to shape variations caused by sway and breathing and shows limited variability to the Cosmetic Score.

Classifying torso deformity in scoliosis using orthogonal maps of the torso

Analysis of three-dimensional (3D) images of human torsos for torso deformities such as scoliosis requires classifying torso distortion. Assessing torso distortion from 3D images is not trivial as actual torsos are non-symmetric and show an outstanding range of variations leading to high classification errors. As the degree of spinal deformity (and classification of torso shape) influences scoliosis treatment options, the development of more accurate classification procedures is desirable. This paper presents a technique for assessing torso shape and classifying scoliosis into mild, moderate and severe categories using two indices, 'twist' and 'bend', obtained from orthogonally transformed images of the complete torso surface called orthogonal maps. Four transforms (axial line, unfolded cylinder, enclosing cylinder and subtracting cylinder) were used. Blind tests on 361 computer models with known deformation parameter values show 100% classification accuracy. Tests on eight volunteers without scoliosis validated the system and tests on 22 torso images of volunteers with scoliosis showed up to 95.5% classification accuracy. In addition to classifying scoliosis, orthogonal maps present the entire torso in one view and are viable for use in scoliosis clinics for monitoring the progression of scoliosis.

Critical review on non-operative management of adolescent idiopathic scoliosis

There are a number of different non-operative interventions which aim to control moderate adolescent idiopathic scoliosis (AIS) from progression. Clinicians may find difficulties in the selection of appropriate interventions for AIS. A comprehensive literature review was carried out to study all contemporary non-operative interventions, it was noted that rigid spinal orthoses apparently give more curve control; however, it would compromise the patient's quality of life via those inevitable factors--physical constraint, poor acceptance and psychological disturbance. There is a trend to develop more effective, acceptable and user-friendly interventions. Under such an aspiration, the theories and clinical evidence of different interventions should be developed along the clinical pathway of early intervention with reliable indicators/predictors, patient's active participation, dynamic control mechanism, holistic psychological and psychosocial considerations, and effective and long-lasting outcome.