Search

Introduction The understanding of the biomechanics of movements in the spinopelvic segment plays an important role in the successful treatment of patients with hip-spine syndrome. Analysis of the biomechanical processes occurring in the biokinematic chain of the spine–pelvis–hip during the transition from standing position to sitting position allows us to conclude that the acetabular axis of rotation of the pelvis in space is not the only one. Classical methods for measuring PI, PT, overhang S1 are applicable for patients in a standing position and use the hip joint as a starting point, since it is the point of rotation of the pelvis in space in a standing position. Previously, using mathematical modeling, we described spatial changes in the pelvis during a given change in the body position and showed the presence of a second point of pelvis rotation in space, which appears in a sitting position. We assumed that in a sitting position, it is necessary to use other methods for calculating indicators of spinopelvic relationships for their determination. Purpose of the study was to evaluate the parameters of patients’ sagittal balance using the proposed alternative method in standing and sitting positions. Materials and methods Medical documentation and the results of X-ray examination of 20 patients with unilateral idiopathic coxarthrosis who underwent total hip replacement surgery were analyzed. The radiographic parameters were calculated: PI, PT, overhang S1 in standing and sitting positions, anterior inclination of the acetabular component; parameters PI ischial, PT ischial, deviation of the ischial tuberosities in standing and sitting positions were proposed and calculated. Results The study shows that there is no statistical difference in the values of the angles PI standard for a standing position and PI ischial for a sitting position. It corresponds to objective data and is generally accepted. Examples of changes in radiographic parameters of the sacral slope and the deviation of the ischial tuberosities were shown reflecting the rotation of the pelvis in space through the second, ischial axis, that confirm the biaxial concept of pelvic rotation. Discussion The calculations demonstrated the possibility of using alternative indicators of spinopelvic relationships (PT, distance of overhang of the sacrum (overhang S1), deviation of the ischial tuberosities). They enabled assessment of the spatial transformation of the pelvis and the ability to predict the spatial position of the acetabulum, which is an important factor for successful treatment of patients with combined pathology of the hip joint and spine. Conclusion Our findings complement the biaxial concept of pelvic rotation. An alternative method for measuring sagittal balance parameters in a sitting position has been proposed. Further research is required to assess the practical significance of this method.

Introduction The success of the treatment of patients with degenerative diseases of the spine and concomitant damage to the hip joint depends on the understanding of the biomechanics of movements in the spinal-pelvic segment. After a thorough analysis of the biomechanical processes occurring in the spine-pelvis system during the transition from a standing to a sitting position, it becomes clear that the acetabular axis of rotation of the pelvis in space is not the only one. The purpose of the study was to develop and test a virtual model of the pelvis to study the kinematics of the movement of the spinal-pelvic complex with a description of the emergence of the iscial axis of rotation by changing the position from standing to sitting. Materials and methods The problem was solved using the finite element method. The bones were modeled as absolutely rigid bodies. The main ligaments and muscles were modeled using finite element springs: elastic fragments with specified rheological characteristics. The study of contact interaction was carried out for pairs: "femoral head – acetabulum" and "ischial tuberosities - chair surface". Results A new axis of rotation was revealed, the ischial axis, which corresponded to the points of initial contact of the ischial tuberosities with the surface of the chair. The axis of the acetabulum rotated by 7.1° relative to the ischial axis and at the final moment shifted in the horizontal direction relative to the acetabular axis by 8.83 mm. The gap between the surfaces of the femoral head and the acetabulum was about 8 mm. Discussion The study shows that the pelvis rotates depending on the position around two axes: acetabular and ischial ones, hence it follows that the acetabular axis oscillates back and forth during anteand retroversion, that is, it is non-static. Shortcomings of the model: 1) muscles and ligaments were modeled using FE springs, the end and beginning of which were set by two points, and the muscles and ligaments in the real body are attached along the entire surface of the bones; 2) soft tissues were not modeled in real volume. The merit of the study is the contact interaction of the pelvis with the chair and its rotation relative to the ischial axis, while other studies consider the rotation of the pelvis only relative to the acetabular axis. Conclusion A new axis of rotation arises due to the contact interaction of the pelvic bone with the surface of the chair when the skeleton moves from a standing position to a sitting position, the ischial axis. The gap between the surfaces of the femoral head and the acetabulum was about 8 mm. It is advisable to conduct a clinical study.

Introduction The article presents a case report and a brief literature review of an adverse event of brachial plexus injury associated with prone positioning in spinal surgery. The purpose was to report a case of bilateral brachial plexus injury after correction of Scheuermann's kyphosis. Material and methods Reported is a case of brachial plexus injury in a patient with Scheuermann's kyphosis after surgical correction. Results The patient could completely regain motor function of the left limb at 6 months with palsy scored 3 proximally retained in the right hand. Discussion The literature describes three pathophysiological conditions that predispose to brachial plexus injury in the postoperative period: sprain, compression, and ischemia. The adverse event is reversible in most cases and recovery depends on the degree of neurological deficit at an early stage. Recommendations are offered for surgeons and anesthesiologists to avoid the occurrence of the complication or take timely measures to alleviate the consequences. Conclusion Upperlimb somatosensory evoked potentials, a part of neurophysiological monitoring can be practical for prevention of the complication. Prevention of brachioplexopathy should be part of perioperative care.