We present a study done to measure the change of angle of the acetabulum or cup, due to leg length discrepancy, deformity of hip and spine on standing. In 1998 a 3-dimensional reconstruction of hip model was prepared on CAD and the change of angle of the cup was measured as Functional Acetabular Inclination Angle (FAIA) with patient standing without squaring the pelvis. The FAIA on standing was compared with angle of the cup with patient in supine position with squared pelvis. The position of the cup changed on weight bearing due to multiple issues. The results showed that one centimetre of leg lengthening changed FAIA by 3°, 10° of abduction deformity resulted in apparent lengthening of 2.87 cm and loss of lordosis anteverted the cup on loading and vice-versa. We conclude that fixed hip deformities, leg length discrepancy and spine deformities can affect the angle of cup in hip replacement surgery and may prone to dislocations, impingement and segmental wear of the cup

There is an increased incidence of dislocation, dysplasia, slipped epiphysis, Perthes’ disease, and avascular necrosis leading to degenerative arthritis which occurs in up to 28% of Down's syndrome patients. As the life expectancy for patients with Down's syndrome has increased, so has the presence of hip disease. Hip replacement has been shown to have good results in this population. Special considerations include a high risk of postoperative dislocation and leg length inequality which often require large head THR or dual mobility type reconstruction to reduce these risks. Numerous spine deformities including scoliosis and C1-2 subluxation need to be taken into account-anesthesia consult

Summary. Optimum position of pedicle screws can be determined preoperatively by CT based planning. We conducted a comparative study in order to analyse manually determined pedicle screw plans and those that were obtained automatically by a computer software and found an agreement in plans between both methods, yet an increase in fastening strengths was observed for automatically obtained plans. Hypothesys. Automatic planning of pedicle screw positions and sizing is not inferior to manual planning. Design. Prospective comparative study. Introduction. Preoperative planning in spinal deformity surgery starts by a proper selection of implant anchors throughout the instrumented spine, where pedicle screws provide the optimum choice for bone fixation. In the case of severe spinal deformities, dysplastic pedicles can limit screw usage, and therefore studying the anatomy of vertebrae from preoperative images can aid in achieving the safest screw position through optimal fastening strength. The purpose of this study is to compare manually and automatically obtained preoperative pedicle screw plans. Materials and Methods. CT scans of 17 deformed thoracic spines were studied by two experienced spine deformity surgeons, who placed 316 pedicle screws in 3D using a software positioning tool by aiming for the safest trajectory that permitted the largest possible screw sizes. The resulting manually obtained screw sizes, trajectory angles, entry points and normalised fastening strengths were compared to those obtained automatically by a dedicated computer software that, basing on vertebral anatomy and bone density in 3D, determined optimal screw sizes and trajectories. Results. Statistically significant differences were observed between manually and automatically obtained plans for screw sizes (p < 0.05) and trajectory angles (p < 0.001). However, for automatically obtained plans, screws were not smaller in diameter (p < 0.05) or shorter in length (p < 0.001), while screw normalised fastening strengths were higher (p < 0.001). Conclusions. In comparison to manual planning, automatically obtained plans did not result in smaller screw diameters or shorter screw lengths, which is in agreement with the definition of the pull-out strength, but in different screw trajectory angles, which is reflected by higher normalised fastening strengths. Captions. Fig. 1. Visual comparison among automatically obtained (green colour) and manually defined pedicle screw placement plans by two experienced spine surgeons (red and blue colour) for three different patients with adolescent idiopathic scoliosis, shown from top to bottom in a three-dimensional view, left sagittal, right sagittal and coronal view. Fig. 2. Histograms of differences between observers and (left column), between observer and automated method (middle column), and between observer and automated method (right column), shown from top to bottom for differences in pedicle screw pedicle screw diameter, sagittal inclination, and normalised fastening strength. For figures/tables, please contact authors directly.

Introduction. EOS® is a low dose imaging system which allows the acquisition of coupled AP and lateral high-definition images while the patient is in standing position. HipEos has been developped to perform pre-surgical planning including hip implants selection and virtual positioning in functional weight-bearing 3D. The software takes advantage of the real size 3D patient anatomical informations obtained from the EOS exam. The aim of this preliminary study on 30 consecutive THP patients was to analyze the data obtained from HipEos planning for acetabular and femoral parameters and to compare them with pre and post-operative measurements on standing EOS images. Material and methods. Full body images were used to detect spino-pelvic abnormalities (scoliosis, pelvic rotation) and lower limbs discrepancies. One surgeon performed all THP using the same type of cementless implants (anterior approach, lateral decubitus). The minimum delay for post-op EOS controls was 10 months. A simulation of HipEos planning was performed retrospectively in a blinded way by the same surgeon after the EOS controls. All measurements were realized by an independent observer. Comparisons were done between pre and post-op status and the “ideal planning” taking in account the parameters for the restitution of joint offset and femur and global limb lengths according to the size of the selected implants. Regarding cup anteversion, the data included the anatomical anteversion (with reference to the anterior pelvic plane APP) and functionnal anteversion (according to the horizontal transverse plane in standing position). Results. The difference between pre-op and post-op APP angles is not statistically significant (p = 0.85), likewise for the sacral slope (p = 0.3). Thus, there has been no change in the orientation of the pelvis after THP. Comparing the two hips on post-op EOS data shows that the difference in femoral offset is not statistically significant (p = 0.76). However, the femoral length is statistically different (p <0.05) (mean 4mm, 0–12mm). The difference for femoral offset between HipEOS planning and post-op EOS data is not statistically significant (p = 0.58). However, the mean difference is significant (p <0.05) for femur length (5mm), inclination (5°) and anteversion of the cup. The mean post-op anatomic anteversion measured in the APP is 27°, whereas it is 11° with HipEOS planning. The mean functional anteversion of the cup on standing post-op EOS data is 35° while planning it is 17°. Otherwise, differences in femoral anteversion are not significant. Conclusion. The planning tools currently available include only the local anatomy of the hip for THP adjustment. This software integrates weight-bearing position, which allows to consider the impact of spine deformities and length discrepancies. This preliminary study is only retrospective, but it highlights the potential interest this “global planning” particularly for the optimization of acetabular anteversion and length adjustment according to pelvic tilt. Planning using the standing lateral view is interesting not only for visualization of the sagittal curvature of the femur and the detection of potential difficulties, but also for the visual data provided on the sagittal orientation of the cup

Objective. Posterior vertebral column resection (PVCR) is indicated in the management of severe rigid spine deformities. It is a complex surgical procedure and is only performed in a few spine centres due to the technical expertise required and associated risk. The purpose of this study is to review the indications, surgical challenges and outcomes of patients undergoing PVCR. Methods. 12 patients with severe spinal deformities who underwent PVCR were retrospectively reviewed after a follow-up of 2 years. Surgery was performed with the aid of motor evoked spinal cord monitoring and cellsaver when available. The average surgical duration was 310 minutes (100–490). The average blood loss was 1491 ml (0–3500). The indication for PVCR was gross deformity and myelopathy which was due to congenital spinal deformities and one case of old tuberculosis. Clinical records and the radiographic parameters were reviewed. Results. Kyphosis of an average of 72 degrees was corrected to 28 degrees. The associated scoliosis was corrected from an average of 49.2 to 21.2 degrees. Ten patients improved neurologically to ASIA D and E. One patient deteriorated markedly, required revision with no initial improvement but reached ASIA E at 6 months after surgery. Four patients had associated syringomyelia. All were re-scanned at 1 year. The three with small syrinx's demonstrated no progression on MRI and the large syrinx resolved completely. In addition to the neurological deterioration, complications included 1 right lower lobe pneumonia. Conclusion. PVCR is an effective option to correct complex rigid kyphoscoliosis. In addition it allows excellent circumferential decompression of the cord and neurological recovery. When the congenital scoliosis is associated with syringomyelia with no other cause evident, it may allow resolution of the syrinx. Key words: Posterior vertebral column resection, severe spinal deformities, myelopathy, syringomyelia. NO DISCLOSURES