Carol-Claudius Hasler

Using Skin Markers for Spinal Curvature Quantification in Main Thoracic Adolescent Idiopathic Scoliosis: An Explorative Radiographic Study.

Background and Purpose Although the relevance of understanding spinal kinematics during functional activities in patients with complex spinal deformities is undisputed among researchers and clinicians, evidence using skin marker-based motion capture systems is still limited to a handful of studies, mostly conducted on healthy subjects and using non-validated marker configurations. The current study therefore aimed to explore the validity of a previously developed enhanced trunk marker set for the static measurement of spinal curvature angles in patients with main thoracic adolescent idiopathic scoliosis. In addition, the impact of inaccurate marker placement on curvature angle calculation was investigated. Methods Ten patients (Cobb angle: 44.4±17.7 degrees) were equipped with radio-opaque markers on selected spinous processes and underwent a standard biplanar radiographic examination. Subsequently, radio-opaque markers were replaced with retro-reflective markers and the patients were measured statically using a Vicon motion capture system. Thoracolumbar / lumbar and thoracic curvature angles in the sagittal and frontal planes were calculated based on the centers of area of the vertebral bodies and radio-opaque markers as well as the three-dimensional position of the retro-reflective markers. To investigate curvature angle estimation accuracy, linear regression analyses among the respective parameters were used. The impact of inaccurate marker placement was explored using linear regression analyses among the radio-opaque marker- and spinous process-derived curvature angles. Results and Discussion The results demonstrate that curvatures angles in the sagittal plane can be measured with reasonable accuracy, whereas in the frontal plane, angles were systematically underestimated, mainly due to the positional and structural deformities of the scoliotic vertebrae. Inaccuracy of marker placement had a greater impact on thoracolumbar / lumbar than thoracic curvature angles. It is suggested that spinal curvature measurements are included in marker-based clinical gait analysis protocols in order to enable a deeper understanding of the biomechanical behavior of the healthy and pathological spine in dynamic situations as well as to comprehensively evaluate treatment effects.

Quantifying spinal gait kinematics using an enhanced optical motion capture approach in adolescent idiopathic scoliosis

BACKGROUND AND PURPOSE The pathogenesis of adolescent idiopathic scoliosis (AIS) remains poorly understood. Previous research has indicated possible relationships between kinematics of the spine, pelvis and lower extremities during gait and the progression of AIS, but adequate evidence on spinal kinematics is lacking. The aim of this study was to provide a detailed assessment of spinal gait kinematics in AIS patients compared to asymptomatic controls. METHODS Fourteen AIS patients and 15 asymptomatic controls were included. Through introducing a previously validated enhanced trunk marker set, sagittal and frontal spinal curvature angles as well as general trunk kinematics were measured during gait using a 12-camera Vicon motion capture system. Group comparisons were conducted using T-tests and relationships between kinematic parameters and severity of scoliosis (Cobb angle) were investigated using regression analyses. RESULTS The sagittal thoracic curvature angle in AIS patients showed on average 10.7° (4.2°, 17.3°) less kyphosis but 4.9° (2.3°, 7.6°) more range of motion (Cobb angle-dependent (R(2)=0.503)). In the frontal plane, thoracic and thoracolumbar/lumbar curvature angles indicated average lateral deviations in AIS patients. General trunk kinematics and spatio-temporal gait parameters, however, did not show any clinically relevant differences between the groups. CONCLUSIONS This demonstrates that the dynamic functionality of the scoliotic spine can be assessed using advanced non-invasive optical approaches and that these should become standard in clinical gait analysis. Furthermore, curvature angle data might be used to drive sophisticated computer simulation models in order to gain an insight into the dynamic loading behavior of the scoliotic spine during gait.

Neuromuscular Spine Deformities

Neuromuscular scoliosis in patients under the age of 10 years is characterized by a disease-specific high progression rate due to muscular imbalance such as the primum movens, ongoing growth, and osteopenia. Those mostly non-ambulating patients typically suffer from pelvic obliquity, loss of sitting balance, rib impingement on the iliac crest, delicate skin conditions, and concomitant medical problems such as pulmonary function deficits, recurrent urinary infections, malnutrition, and skin ulcerations. The resulting therapeutic challenge is that of an increasing spine deformity in a sick patient. The type and timing of intervention should be based on a sound knowledge of the specific natural history and multiple disease-specific factors but should also take the individual needs of the patient and his psychosocial environment into thorough consideration to avoid complications and disasters in this high-risk population.

Statistical shape modeling of pathological scoliotic vertebrae: A comparative analysis

Statistical shape models (SSMs) have been used widely as a basis for segmenting and interpreting complex anatomical structures. The robustness of these models are sensitive to the registration procedures, i.e., establishment of a dense correspondence across a training data set. In this work, two SSMs based on the same training data set of scoliotic vertebrae, and registration procedures were compared. The first model was constructed based on the original binary masks without applying any image pre- and post-processing, and the second was obtained by means of a feature preserving smoothing method applied to the original training data set, followed by a standard rasterization algorithm. The accuracies of the correspondences were assessed quantitatively by means of the maximum of the mean minimum distance (MMMD) and Hausdorf distance (HD). Anatomical validity of the models were quantified by means of three different criteria, i.e., compactness, specificity, and model generalization ability. The objective of this study was to compare quasi-identical models based on standard metrics. Preliminary results suggest that the MMMD distance and eigenvalues are not sensitive metrics for evaluating the performance and robustness of SSMs.

Spinal Loading System: A Novel Technique for Assessing Spinal Flexibility in Adolescent Idiopathic Scoliosis

The assessment of curve flexibility and its geometric patterns are important parameters in the surgical decision-making process for patients with adolescent idiopathic scoliosis (AIS). Despite numerous publications in recent years evaluating and comparing different preoperative clinical techniques, there is still no consensus among surgeons as to the most appropriate technique for assessing spinal flexibility. The preoperative tests currently used in clinical practice are subjected to numerous uncertainties and are difficult, depending on the experience of the observers and on the patient’s emotional and physical conditions. In order to overcome these limitations, a mechatronic system capable of applying a controlled pure quasi-static axial load to the patient’s cervical spine has been developed and clinically evaluated. Our preliminary results suggest that the proposed SLS may be a useful tool for assessing curve flexibility.

Achsen und Längen

Mit dem Einwartsgang demonstriert das Kind, dass wir nicht gottlichen, sondern tierischen Ursprungs sind. Wie bei allen Saugetieren ist der menschliche Fotus mit einer in der Hufte flektierten Stellung im Mutterleib. Die Zentrierung des Femurkopfes ist bei erhohter Antetorsion in Flexion besser als bei nur geringer Drehung des Schenkelhalses nach vorne.

VEPTR Instrumentation in Early Onset Scoliosis

VEPTR has been developed for the treatment of thoracic insufficiency syndrome in cases of congenital scoliosis with or without rib fusions but quickly evolved as an alternative for the treatment of many types of early onset scoliosis. The efficacy of VEPTR instrumentation in controlling complex congenital spine deformities, the relative ease of application, and the spine-sparing approach have been factors to stimulate this conversion. VEPTR in non-congenital cases has been shown to be effective in correcting loss of balance and pelvic obliquity, control scoliosis, and moderately improve it. However, it requires periodic lengthening and thus has a high complications rate, and usually after a certain time lengthenings become less effective. VEPTR instrumentation remains a viable alternative to other methods of management of early onset scoliosis.

Other Neuromuscular Disorders with Scoliosis

Neuromuscular scoliosis proves itself to be a challenge due to many facts. Among these are the usually early age of onset, rapid progression, rigidity, and lack of response to brace treatment. Added to that the inherent problems present in an already sick child, surgical interventions become perilous. Meningomyelocele patients provide an additional challenge by their lack of posterior anchor points for instrumentation and difficulty in achieving soft-tissue coverage. Neurofibromatosis type-1 scoliosis often accompanies preexisting neurological deficits, neurofibromas, rib protrusion into the spinal canal, and others. Arthrogryposis syndromes with multiple joint contractures and micrognathia may make intubation and patient positioning a challenge before surgery is even begun. Growth-retaining constructs such as the VEPTR and double growing rods represent the current mainstay of surgical treatment, barring specific contraindications unique to the disorder at hand.