European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society
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Correction of adolescent idiopathic scoliosis (AIS) has been reported with various systems. All-screw constructs are currently the most popular, but they have been associated with a significant decrease in thoracic kyphosis, with a potential risk of junctional kyphosis, not observed with hybrid constructs in the literature. In addition, it is important to weigh potential advantages of pedicle screw fixation against risks specific to its use. ⋯ The technique was safe, and reduced operative time, radiation exposure, and blood loss. While achieving correction of deformity in the coronal and axial planes equivalent to the best reported results of all-screw or previous hybrid constructs, the UC hybrid technique appears to provide superior correction in the sagittal plane. The excellent outcome in all three planes was maintained at 2 year follow up.
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The effects of different parameters on the mechanical behaviour of the lumbar spine were in most cases determined deterministically with only one uncertain parameter varied at a time while the others were kept fixed. Thus most parameter combinations were disregarded. The aim of the study was to determine in a probabilistic finite element study how intervertebral rotation, intradiscal pressure, and contact force in the facet joints are affected by the input parameters implant position, implant ball radius, presence of scar tissue, and gap size in the facet joints. ⋯ Intervertebral rotation and contact force in the facet joints depend strongly on the input parameters studied. The probabilistic study shows a large variation of the results and likelihood of certain values. Clinical studies will be required to show whether or not there is a strong correlation of parameter combinations that cause high facet joint forces and low back pain after total disc replacement.
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Shoulder balance is one of the key components to the body deformity in adolescent idiopathic scoliosis (AIS) patients with double thoracic curve and shoulder cosmesis plays an important role in patients' satisfaction of surgical outcomes. Up to now, only radiographic parameters were used to evaluate the shoulder balance in literatures; no corresponding cosmetic parameters have been developed to evaluate the cosmetic shoulder balance. Meanwhile, we often confronted that perfect radiographic shoulder balance was achieved, but the patients complained about the residual cosmetic deformity. ⋯ The results indicated that radiographic parameters could only partially reflect the shoulder cosmetic appearances. However, none of the existing parameters can accurately reflect the shoulder cosmetic appearance. As cosmesis is critical important to patients' satisfaction, spine surgeons should pay more attention to the cosmetic shoulder balance rather than radiographic shoulder balance.
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Wear simulation is an essential pre-clinical method to predict the mid- and long-term clinical wear behavior of newly introduced devices for total disc arthroplasty. The main requirement of a suitable method for spinal wear simulation has to be the ability to distinguish between design concepts and allow for a direct comparison of predicate devices. The objective of our study was to investigate the influence of loading and kinematic patterns based on two different protocols for spinal wear simulation (ISO/FDIS 18192-1 (2006) and ASTM F2423-05). ⋯ Due to previous retrieval observations, it seems to be very unlikely that a lumbar artificial disc is loaded with a linear wear path. Testing according to ASTM F2423-05 with pure unidirectional motion does not reflect the kinematics of TDA patients' daily activities. Based on our findings it seems to be more reliable to predict the clinical wear behavior of an artificial disc replacement using the ISO/FDIS 18192-1 method.